MINERALOGY AND GEOCHEMISTRY OF GRANITOID PEGMATITE DYKES FROM MAWAT OPHIOLITE, KURDISTAN REGION, NORTHEASTERN IRAQ
A thesis Submitted to the Council of Faculty of Science and Science Education School of Science at the University of Sulaimani In partial fulfillment of the requirements for the degree of Master of Science in Geology (Mineralogy)
By
Hiwa Jamal Kareem B.Sc. in Geology (2008), University of Sulaimani
Supervised by
Dr. Yousif Osman Mohammad Assistant Professor
Jozardan, 2715 KU.
May, 2015 A.D.
Supervisor Certification I certify that the preparation of this thesis, entitled "Mineralogy and Geochemistry of Granitoid Pegmatite dykes from Mawat Ophiolite, Kurdistan Region, Northeastern Iraq" accomplished by (Hiwa Jamal Kareem), was prepared under my supervision in the School of Science, Faculty of Science and Science Education at the University of Sulaimani, as a partial requirement for the degree of Master of Science in Geology (Mineralogy).
Signature: Name: Dr. Yousif O. Mohammad Title: Assistant Professor Date:
/
/2015
In view of the available recommendation, I forward this thesis for debate by the examining committee.
Signature: Name: Dr. Diary A. Muhammad Title: Assistant Professor Date:
/
/2015
Examining Committee Certification We certify that we have read this thesis entitled " Mineralogy and Geochemistry of Granitoid Pegmatite dykes from Mawat Ophiolite, Kurdistan Region, Northeastern Iraq" prepared by (Hiwa Jamal Kareem), and as Examining Committee, examined the student in its content and in what is connected with it, and in our opinion it meets the basic requirements toward the degree of Master of Science in Geology “Mineralogy”.
Signature:
Signature:
Name: Dr. Nabaz Rashid Hama Aziz
Name: Dr. Sarmad Asi Ali
Title: Assistant Professor
Title: Assistant Professor
Date: 28 / 5 / 2015
Date: 28 / 5 / 2015
(Chairman)
(Member)
Signature:
Signature:
Name: Dr. Sardar M. Ridha Babashekh
Name: Dr.Yousif O. Mohammad
Title: Lecturer
Title: Assistant Professor
Date: 28 / 5 / 2015
Date: 28 / 5 / 2015
(Member)
(Supervisor - Member)
Approved by the Dean of the Faculty of Science and Science Education
Signature: Name: Dr. Bakhtiar Q. Aziz Title: Professor Date:
/
/ 2015
Dedication To my Father and My Mother My wife My Brothers and Sisters
Acknowledgments
First of all, it is my duty to thank my “God” who gave me the health and power to finish this thesis. I would like to express my deepest thanks to my supervisor Dr. Youisf Osman Mohammad, Their patience, encouragement and advice he has provided throughout my time as his student. I have been extremely lucky to have a supervisor who cared so much about my work, and who responded to my questions, precious remarks throughout the work, and providing me with many valuable references. I am thankful to the School of Science and Geology Department, University of Sulaimani for providing available facilities and administrative support and my special thanks to head of the geology department for his considerable assistance. A special thanks to Dr. Nabaz R. H. Aziz for help me during the fieldwork observation and interpretation the geochemical data. I am particular thankful to my friends (Mr.Asaad Ibrahim and Mrs. Kurda Latife) from geology department for his help during the field work and sample collection, and (Mr. Karwan A. Mustafa and Mr. Faraydoon N. Rashid) PhD students from United Kingdom for providing references. I would like to thank my friends Mr. Fahmi O. Mohammad for helping in drawing maps and Dr. Salim H. Sulaiman for abstract translation into Arabic. Above all I would like to thank my wife “Rozha” for her love and constant support, for all the late nights and early mornings, and for keeping me sane over the past few months, thank you for being my best friend. I owe you everything. My final thanks are reserved for my family especially my Father, my Mother and my greater brother who have been a continual source of support both financial and emotional, strength and motivation and for that I am forever grateful.
I
Abstract The highly evolved Kuradawe felsic pegmatite is discordant dykes hosted in harzburgite – dunite succession of Mawat Ophiolite situated in Kurdistan Region of Northeastern Iraq. For the first time the felsic pegmatite dikes have been identified in the Mawat ophiolite. They are mainly composed of quartz, K-feldspar, albite, tourmaline, muscovite, and lepidolite. Mg-cordierite, andalusite, Ce-Monazite, biotite, Zircon, Nb-rutile Cl-Apatite, and Sc-columbite are the most significant accessory minerals.
Field, petrographical, mineralogical and geochemical study show the complete internal zonal sequence from the border inward: border zone (5-10 cm), wall zone (80 cm-1 m), intermediate zone (1-2 m), and core zone (nearly 2 m). Kuradawe felsic pegmatite classified as the LCT (Lithium, Cesium, Tantalum) family, rare-element class, REL-REE subclass, and allanite-monazite type. High-temperature minerals assemblages cordierite + andalusite suggest that the rock overprinted by contact metamorphism along the border during intrusions to semi-solid hot country rocks.
P-T evolution history suggests that crystallization of Kuradawe felsic Pegmatite occur at shallow level (2-4 Kbar) with crystallization sequences started from the contact toward the core with temperature, the maximum temperature equal to (772oC) and the minimum temperature equal to (534oC)
The major and trace element signatures of Kuradawe felsic pegmatite precisely align with a compositional affinity with S-type granite.
Detailed field, petrographic and geochemical data of the Kuradawe felsic pegmatite body are consistent with a fractional crystallization model from a granitic melt and with a definite petrogenetic relationship with the underlying peraluminous tourmaline leucogranites.
The leucogranite and pegmatite assemblages, probably emplaced during initial stage of Zagros Ophiolite obduction (95 Ma), represent an upward fingering-out system II
presumably rooted in a deeper-seated granitic parent, which was derived by anatexis of felsic lithologies of the subduction wedge.
Geochemical features of Kuradawe felsic pegmatite dikes favor orogenic subductionrelated, syn-collisional tectonic setting.
III
CONTENTS Subjects
Page No.
Acknowledgements
…………………………………………………………..
I
Abstract
…………………………………………………………..
II
List of Contents
…………………………………………………………..
IV
List of Figures
…………………………………………………………..
VIII
List of Tables
…………………………………………………………..
XVI
Chapter One: Introduction 1.1
Preface ………………………………………………………...............
1
1.2
Location of the studied area……………………………………………
2
1.3
Tectonic setting………………………………………………………..
6
1.4
Local geology of the studied area ……………………………………...
7
1.5
Previous works………………………………………………………...
10
1.6
Aims of the study………………………………………………………
14
1.7
Field description……………………………………………………….
14
1.8
Analytical techniques………………………………………………….
14
Chapter Two: Petrography and Mineralogy 2.1
Preface…………………………………………………………………
18
2.2
Petrography……………………………………………………………
18
2.2.1
Petrography of host rock……………………………………………….
18
2.2.2
Petrography of pegmatite dykes……………………………………….
19
2.3
Textures of Kuradawe felsic pegmatite………………………………..
21
2.3.1
Igneous textures………………………………………………………..
21
2.3.1.1
Perthitic Texture……………………………………………………….
21
2.3.1.2
Graphic Texture………………………………………………………..
22
2.3.2
Metamorphic textures………………………………………………….
23
2.3.2.1
Deformation Twins……………………………………………………
23
2.3.2.2
Corona structure……………………………………………………….
23
2.3.2.3
Kink Bands…………………………………………………………….
25
2.3.2.4
Crenulation cleavage…………………………………………………..
25
2.3.2.5
Granoblastic Texture…………………………………………………..
25
2.3.2.6
Lepidoblastic Texture………………………………………………….
27
2.3.2.7
Porphyroblastic Texture……………………………………………….
27
IV
2.3.2.8
Mica fish……………………………………………………………….
29
2.4
Mineral constituent of the Kuradawe felsic pegmatite…………………
33
2.4.1
Essential Minerals……………………………………………………..
33
2.4.1.1
Quartz………………………………………………………………….
33
2.4.1.2
Alkali-feldspars (Orthoclase and Microcline)…………………………
33
2.4.1.3
Plagioclase…………………………………………………………….
34
2.4.1.4
Muscovite……………………………………………………………...
36
2.4.1.5
Tourmaline…………………………………………………………….
39
2.4.2
Accessory minerals……………………………………………………
44
2.4.2.1
Biotite………………………………………………………………….
44
2.4.2.2
Zircon………………………………………………………………….
44
2.4.2.3
Andalusite……………………………………………………………..
44
2.4.2.4
Rutile…………………………………………………………………..
44
2.4.2.5
Cordierite……………………………………………………………...
46
2.4.2.6
Columbite……………………………………………………………...
46
2.4.2.7
Apatite…………………………………………………………………
46
2.4.2.8
Monazite……………………………………………………………….
46
2.4.3
Secondary Mineral…………………………………………………….
46
2.5
Mineral composition of host rock……………………………………...
49
2.6
Mineralogical classification…………………………………………...
50
2.7
Mineralogical zones in Kuradawe felsic pegmatite……………………
51
2.8
Mineral chemistry……………………………………………………..
53
2.8.1
Plagioclase…………………………………………………………….
54
2.8.2
Alkali feldspar…………………………………………………………
54
2.8.3
Muscovite……………………………………………………………...
56
2.8.4
Tourmaline…………………………………………………………….
57
2.8.5
Zircon………………………………………………………………….
61
2.8.6
Monazite……………………………………………………………….
62
2.8.7
Columbite……………………………………………………………...
63
2.8.8
Cordierite……………………………………………………………...
64
2.8.9
Andalusite……………………………………………………………..
66
2.8.10
Apatite…………………………………………………………………
67
2.8.11
Rutile…………………………………………………………………..
68
V
Chapter Three: Geochemistry 3.1
Preface…………………………………………………………………
69
3.2
Major Oxides…………………………………………………………..
69
3.2.1
Silica (SiO2)……………………………………………………………
69
3.2.2
Aluminum Oxide (Al2O3)……………………………………………...
72
3.2.3
Sodium Oxide (Na2O)…………………………………………………
73
3.2.4
Potassium Oxide (K2O)………………………………………………..
75
3.2.5
Calcium Oxide (CaO)………………………………………………….
76
3.2.6
Magnesium Oxide (MgO)……………………………………………..
77
3.2.7
Iron Oxide (Fe2O3)…………………………………………………….
77
3.2.8
Other Oxides and LOI………………………………………………….
79
3.3
Nomenclature of the Kuradawe felsic pegmatite………………………
79
3.4
Trace elements…………………………………………………………
84
3.4.1
Compatible trace elements…………………………………………….
86
3.4.2
Incompatible trace elements…………………………………………...
87
3.4.2.1
Large-ion lithophile elements (LILE)………………………………….
87
3.4.2.2
High field strength elements (HFSE)………………………………….
90
3.5
REE elements………………………………………………………….
94
3.6
Pressure – Temperature condition of Kuradawe felsic pegmatite……...
99
Chapter Four: Anatomy and Classification 4.1
Preface…………………………………………………………………
104
4.2
Pegmatite classification………………………………………………..
104
4.2.1
Simple Pegmatite………………………………………………………
105
4.2.2
Complex Pegmatite……………………………………………………
105
4.2.2.1
Pegmatite families……………………………………………………..
107
4.2.2.2
Pegmatite classes and types……………………………………………
111
4.3
Internal anatomy of Kuradawe felsic pegmatite……………………….
114
4.3.1
Border zone……………………………………………………………
115
4.3.2
Wall zone………………………………………………………………
115
4.3.3
Intermediate zone……………………………………………………...
116
4.3.4
Core zone………………………………………………………………
117
4.4
Kuradawe felsic pegmatite zones evaluation…………………………..
120
VI
Chapter Five: Petrogenesis 5.1
Petrogenesis…………………………………………………………...
122
5.1.1
Major element indicator……………………………………………….
122
5.1.2
Trace element indicator………………………………………………..
124
5.1.2.1
Strontium versus the Rb/Sr ratio……………………………………….
124
5.1.2.2
Rubidium versus the K/Rb ratio………………………………………..
125
5.1.2.3
Cesium versus the K/Cs and K/Rb ratios………………………………
126
5.1.2.4
Hafnium versus the Zr/Hf ratios……………………………………….
127
5.1.2.5
Zirconium versus Yttrium and Zr/Y ratio……………………………...
129
5.1.3
Rare element indicator…………………………………………………
130
5.2
Tectonic setting………………………………………………………..
132
Chapter Six: Conclusions and Recommendations 6.1
Conclusions……………………………………………………………
136
6.2
Recommendations……………………………………………………..
139
References ………………………………………………………………………...
140
Appendix ……………………………………………………………………………………
VII
List of Figures Figures 1.1
Chapter One
Page No.
(A) Regional tectonic map of the Kurdistan region of NE Iraq showing major tectonic subdivisions (after Al-kadhimi et al. (1996). (B) Geological map of the study area and showing the three locations of the felsic pegmatite, after (Mohammad et al. 2014)……………………
3
Google earth image of the study area, showing locations of felsic pegmatite within ultramafic unit of Mawat ophiolite…………………..
4
Digital elevation model map for the Mawat area and showing the location of the samples on the largest pegmatites dykes in the studied area……………………………………………………………………
5
(A) A-B cross-section across northeast Iraq showing major tectonic division and boundaries (Mohammad et al., 2014). (B) Geological cross-section from Azmur mountain to Diri (modified after Al-Qayim et al., 2012). (C) Stratigraphic columnar section of Chwarta-Mawat area and showing the felsic pegmatite…………………………………
9
1.5
Highly fracture dyke number one in the Kuradawe felsic pegmatite…...
17
1.6
Larger dyke in the Kuradawe felsic pegmatite…………………………
17
1.2
1.3
1.4
Chapter Two 2.1 2.2
2.3 2.4
2.5
Field photograph is showing very large elongated crystal of tourmaline in the KFP (dyke 3)……………………………………………………. Slab Showing the grain size distribution of tourmaline in Kuradawe felsic pegmatite coarsening from the margin to the center of the body (dyke 2)………………………………………………………………..
20
20
Field photo is showing skeletal crystal of tourmaline, which appears as a black snowflake from KFP (dyke 3)………………………………….
21
Sketch showing different types of Perthite: (a) stringlets; (b) strings; (c) rods; (d) beads; (e) fractured beads; (f) interlocking; (g) interpenetrating; (h) and (j) replacement (Deer et al, .1992)…………...
22
Photomicrographs from KFP showing: (A) Strings and rods type perthitic texture, XP, SN: YO28. (B) Graphic intergrowth of quartz in orthoclase, XP. (C) Deformation twin in albite, XP, SN: YO15 (D) Corona structures in tourmaline mineral, XP. Note: for the abbreviations of minerals using the standard Kretz, (1983), and SN= Sample number………………………………………………………...
24
VIII
2.6
Photomicrographs of KFP showing: (A) Kink bands texture in muscovite, XP, SN: YO14. (B) Kink bands texture in albite, XP, SN: YO26. (C) Asymmetrical crenulation cleavage in muscovite, XP, SN: YO6b. (D) Granoblastic (amoeboid) texture in quartz, XP, SN: YO24..
26
2.7
Photomicrographs from KFP showing: (A) Folded Lepidoblastic texture in muscovite, XP. (B) Pre-tectonic porphyroblastic texture, XP, SN: YO17……………………………………………………………... 28
2.8
Schematic representation of pre-tectonic, sin-tectonic, inter-tectonic and post-tectonic porphyroblast growth. The upper part of the diagram refers to deformation resulting in a single foliation or deformation of an earlier foliation without folding; the lower part considers deformation resulting in crenulation of order foliation (Passchier and Trouw, 2005)………………………………………………………….. 29
2.9
(A) The main types of white mica fish recognized in thin section. (B)
Inferred development of the different types of mica fish (after Ten Grotenhuis et al. 2003)…………………………………………………
31
Photomicrographs from KFP in the sample number YO31 showing: (A) Mica fish (muscovite) mineral, XP. (B) Mica fish (muscovite) mineral, XP. (C) Mica fish (muscovite) mineral, XP. (D) Crenulation cleavage in Muscovite and undulose extinction in quartz, XP…………
32
Photomicrograph from KFP showing: (A) undulose extinction in quartz mineral, XP, SN: YO24. (B) The intergranular aggregate of quartz, XP, SN: YO24 (C) Carlsbad twinning in orthoclase mineral, XP. (D) Cross-hatched twining in Microcline mineral, XP, SN: YO25..
35
2.12
Field photograph of Albite mineral in the Kuradawe felsic pegmatite…
36
2.13
Field photo is showing muscovite in the Kuradawe felsic pegmatite….
37
2.14
Photomicrographs from KFP showing: (A) Chessboard texture in the albite minerals, XP. (B) Carlsbad-twinning in albite mineral, XP. (C). Perfect cleavage in muscovite mineral, XP. (D). Fine grain muscovite formed from the alteration tourmaline mineral, XP, SN: YO6b………..
38
Field photo showing: (A) Pointed (tapered) tourmaline minerals in the border pegmatite zones. (B) Large tourmaline minerals in the core pegmatite zones………………………………………………………..
40
Photomicrographs from KFP showing: (A) Dark green tourmaline occur in the border zone, PPL, sample number (SN): YO6 (B) Brown tourmaline occurs in the border zone, PPL, SN: YO9 (C) Blue to green tourmaline occurs in the wall zone, PPL, SN: YO15 (D) Zoned tourmaline mineral occurs in the wall zone, PPL, SN: YO3……………
42
Photomicrographs from KFP showing: (A) Dark blue to green tourmaline occur in the intermediate zone, PPL, SN: YO22 (B) Green to light green tourmaline occurs in the intermediate zone, PPL, SN: YO29 (C) Light blue to gray tourmaline occurs in the core zone, PPL, SN: YO22b (D) Pink tourmaline mineral occurs in the core zone, PPL, SN: YO32……………………………………………………………...
43
2.10
2.11
2.15
2.16
2.17
IX
2.18
2.19
2.20
2.21 2.22
2.23
2.24 2.25
2.26
2.27 2.28
2.29
Photomicrographs from KFP showing: (A) Primary biotite minerals in the KFP, PPL. (B) Biotite minerals formed from the alteration of tourmaline, PPL, SN: YO32 (C). Zircon mineral, XP, SN: YO14 (D) High relief zircon mineral, PPL, SN: YO14……………………………
45
Photomicrographs from KFP showing: (A) Euhedral to subhedral grains of andalusite mineral, XP, SN: YO17 (B) Rutile mineral in the border zone of KFP, PPL, SN: YO12b (C) Cordierite mineral in the KFP, XP, SN: YO17 (D) Ferrocolumbite mineral in the KFP, PPL, SN: YO15…………………………………………………………………..
47
Photomicrographs from KFP showing: (A) Apatite grains in the KFP, XP, SN: YO17 (B) Monazite mineral in the border zone of KFP, PPL, SN: YO17 (C) Monazite mineral in the KFP, XP, SN: YO17 (D) Secondary chlorite mineral in the KFP, PPL, SN: YO6………………..
48
Plotting of host rock (ultramafic) on ternary diagram after (Le Maitre, 2002)…………………………………………………………………..
50
Plotting of Kuradawe felsic pegmatite data (Modal %) on a preliminary QAP classification of acidic rocks for field use (after Streckeisen, 1976). Q=quartz; A=albite (An0-An5) +Orthoclase (microcline); P= anorthite + albite (An5-An100) after (Le Maitre, 2002)……………….
51
Approximate mineral percentage of mineralogical zone in Kuradawe felsic pegmatite. Abbreviations: Q= Quartz; M= Muscovite; A= Albite; P= Perthite; MI= Microcline…………………………………...
53
Backscattered image of albite and K-feldspar (Orthoclase), plus symbol represent selected points for EMPA analyses, SN: YO5b……..
55
Nomenclature and composition of the feldspars (Alkali feldspar and plagioclase feldspar) of the Kuradawe felsic pegmatite, onto the albite (Ab) – orthoclase (Or) – anorthite (An) triangular diagram after (Deer et al., 1966)…………………………………………………………….
55
Composition of muscovite in the KFP. It shows the primary (magmatic) origin of the analyzed muscovite on the Mg–Ti–Na (a.p.f.u) triangular diagram from Miller et al., (1981)………………….
56
Backscattered image of muscovite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO4b………………………..
57
Classification of the tourmaline super group minerals of Kuradawe felsic pegmatite by chemical composition. The primary division (Top) is made according to the dominant occupancy of the X site to give the X-site vacant, alkali, and calcic groups. The secondary division (Bottom) is made according to the dominant occupancy of the Y site (Mg, Fe+2, 2Li or 1.5 Li) with the Z site =Al dominant and V= OH dominant for X-site vacant group and alkali group, after Henry et al., (2011)………………………………………………………………….
59
Plotting Kuradawe felsic pegmatite tourmaline data on the binary diagram of Mg/Mg+Fe+2 vs. X□/ (X□+Na+1+K+1) after Henry et al., (2011)…………………………………………………………………
60
X
2.30 2.31 2.32 2.33 2.34 2.35 2.36 2.37 2.38 2.39
Backscattered image of tourmaline in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO1b………………………..
60
Backscattered image of zircon in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO12b………………………
61
Backscattered image of monazite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO14………………………..
62
Diagram showing the classification and compositional trends of the columbite-tantalite, after Linnen and Cuney (2005)…………………...
63
Backscattered image of Columbite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO15………………………..
64
Compositional diagram is showing cordierite classification of the KFP, after Černý et al., (1997)……………………………………………….
65
Backscattered image of cordierite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO17………………………..
65
Backscattered image of andalusite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO17………………………..
66
Backscattered image of apatite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO17………………………..
67
Backscattered image of rutile in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO14………………………..
68
Chapter Three 3.1 3.2
3.3 3.4 3.5 3.6 3.7 3.8 3.9
Distribution pattern of silica oxide across the Kuradawe felsic pegmatite………………………………………………………………
70
(A) Harker diagram between SiO2 and Al2O3 in the Kuradawe felsic pegmatite (KFP). (B) Harker diagram between SiO2 and MgO in the (KFP) (after Harker, 1909)…………………………………………….
70
Distribution pattern of Aluminum Oxide across the Kuradawe felsic pegmatite zones………………………………………………………..
72
(A) Binary plot of CaO% versus Al2O3%. (B) The binary plot of MgO% versus Al2O3%...........................................................................
73
Distribution pattern of Sodium oxide (Na2O %) across the Kuradawe felsic pegmatite………………………………………………………..
74
(A) The binary plot of Na2O % versus CaO %. (B) The binary plot of Na2O % versus K2O%.............................................................................
74
Distribution pattern of potassium oxide (K2O %) across the Kuradawe felsic pegmatite………………………………………………………..
75
Distribution pattern of calcium oxide (CaO %) across the Kuradawe felsic pegmatite………………………………………………………..
76
Distribution pattern of Magnesium oxide (MgO %) across the Kuradawe felsic pegmatite…………………………………………….
77
XI
3.10
Distribution pattern of Iron oxide (Fe2O3 %) across the Kuradawe felsic pegmatite………………………………………………………..
78
Bar chart of major elements concentration across the Kuradawe felsic pegmatite………………………………………………………………
79
Normative Ab-Or-An diagram for the Pegmatite rocks of the study area, with dividing lines according to O’Connor, (1965), Ab= Albite, Or= Orthoclase, An= Anorthite………………………………………..
80
Bar chart of major mineral composition by CIPW norms in different Kuradawe felsic pegmatite zones……………………………………...
80
3.14
Al2O3 — CaO — (Na2O+K2O) diagram……………………………….
82
3.15
Fe2O3-Na2O+K2O-MgO (AFM) diagram……………………………...
82
3.16
Plot Kuradawe felsic pegmatite rocks on the of Wright’s (1969) diagram, alkalinity index = Al2O3+CaO+Na2O+K2O/Al2O3+CaONa2O+K2O…………………………………………………………….
83
ACF ternary diagram for the type of Kuradawe felsic pegmatite rocks, after (Hyndman, 1985) Molar ratio: A = Al2O3–Na2O–K2O, C = CaO, F = Fe2O3+MgO……………………………………………………….
83
Zr and Zn versus 10000*Ga/Al genetic classification diagrams for Atype granitoid (Whalen et al., 1987), showing a significant position of the Kuradawe felsic pegmatite…………………………………………
84
Distribution pattern of compatible elements across the Kuradawe felsic pegmatite. Sc = Scandium, Cr = Chromium, Co = Cobalt, Ni = Nickel………………………………………………………………….
86
Distribution pattern of rubidium (Rb) across the Kuradawe felsic pegmatite zones………………………………………………………..
88
Distribution pattern of strontium (Sr) across the Kuradawe felsic pegmatite zones………………………………………………………..
88
Distribution pattern of barium (Ba) across the Kuradawe felsic pegmatite zones………………………………………………………..
89
Distribution pattern of cesium (Cs) across the Kuradawe felsic pegmatite zones………………………………………………………..
89
Distribution pattern of zirconium (Zr) across the Kuradawe felsic pegmatite zones………………………………………………………..
90
Distribution pattern of hafnium (Hf) across the Kuradawe felsic pegmatite zones………………………………………………………..
91
Binary plot between hafnium (Hf) and zirconium (Zr) in the Kuradawe felsic pegmatite zones………………………………………………….
91
Distribution pattern of niobium (Nb) across the Kuradawe felsic pegmatite zones………………………………………………………..
92
Distribution pattern of tantalum (Ta) across the Kuradawe felsic pegmatite zones………………………………………………………..
93
3.11 3.12
3.13
3.17
3.18
3.19
3.20 3.21 3.22 3.23 3.24 3.25 3.26 3.27 3.28
XII
3.29
Distribution pattern of thorium (Th) across the Kuradawe felsic pegmatite zones………………………………………………………..
93
Distribution pattern of uranium (U) across the Kuradawe felsic pegmatite zones………………………………………………………..
94
Total light rare earth element pattern across the Kuradawe felsic pegmatite zones………………………………………………………..
96
Total heavy rare earth element pattern across the Kuradawe felsic pegmatite zones………………………………………………………..
96
Relationship between light rare earth element (LREE) and the heavy rare earth element (HREE) in deferent zones of Kuradawe felsic pegmatite………………………………………………………………
97
Chondrite normalized REE plots for Kuradawe felsic pegmatite, Normalization values are those of Sun and McDonough, (1989)………
98
Phase relationships and minimum melt compositions in the CIPW normative system quartz-albite-orthoclase ±H2O ±anorthite ±F. Experimental minimum melt compositions from (Rollinson, 1993)…...
100
3.36
P-T phase diagram after (Winter, 2001)………………………………..
100
3.37
P-T field of environments hosting pegmatite populations of the abyssal (AB), muscovite (MS), muscovite – rare-element (MSREL), rareelement (REL) and miarolitic (MI) classes (Modified after Ginsburg et al., 1979 and Černȳ, 1990a. Arrows indicate regional trends of fractionation in the pegmatites relative to metamorphic grades of the host rocks. The MS and MSREL populations, as well as those of the REL and MI pegmatites, tend to be in some cases transitional one to the other (after Černȳ and Ercit, 2005). Aluminosilicate fields and their limits of error from Robie & Hemingway (1984), spodumene– petalite boundary from London (1984), granite liquidus – solidus after Jahns (1982). The 25°C/km and 50°C/km gradients correspond to average Barrovian and Abukuma metamorphic facies series, respectively……..
101
T-Size relation of tourmaline mineral in a different zone from Kuradawe felsic pegmatite…………………………………………….
102
3.30 3.31 3.32 3.33
3.34 3.35
3.38
XIII
Chapter Four 4.1
4.2 4.3
4.4 4.5
4.6
4.7
(a) The pegmatite classification scheme adopted by Černý and Erict (2005). (b) P-T diagram showing the fields of the four pegmatite classes proposed by Ginsburg (1984) and Černý (1991). The pegmatite classes are abyssal (AB), muscovite (MS), rare-element (RE), and miarolitic (MI). Lable reaction-boundaries are (1) kyanite → andalusite, (2) kyanite → sillimanite, (3) andalusite → sillimanite, (4) spodumene + 3 quartz → virgilite, (5) petalite + quartz → βspodumene, (6) spodumene + 2 quartz → petalite, and (7) sekaninaite (Skn, the Fe analog of cordierite) → almandine + aluminosilicate + quartz. Reaction (1) – (3) from Pattison (1992) as modified be Cesare et al. (2003), reaction (4) – (6) are simplified from London (1984), reaction (7) is from Mukhopadhyay and Holdaway (1994). Red start is the average of the KFP samples……………………………………...
106
A/NK = Al2O3/ (Na2O + K2O) versus A/CNK = Al2O3 / (CaO + Na2O + K2O) diagram after Maniar & Piccoli, (1989)………………………..
108
Discrimination diagrams for LCT and NYF-family granitic pegmatites. Al2O3-MgO-FeO ternary diagram for biotite, after (Wise, 2013)…………………………………………………………………..
110
Typical zoning sequence pegmatite modified from Vlasov (1961). From the granitic source……………………………………………….
114
Model for Kuradawe felsic pegmatites zones. The KFP consist of four zones, border zone, wall zone, intermediate zone, and core zone respectively from margin to center of pegmatite………………………. 3D Block diagram of a zoned Kuradawe felsic pegmatite, showing the concentric nature of zoning in steeply dipping. Lateral and vertical scales are in meters……………………………………………………. Model for temperature evaluation of Kuradawe felsic pegmatite……...
118
119 121
Chapter Five 5.1
Harker variation diagram for most major oxide in the Kuradawe felsic pegmatite………………………………………………………………
123
Strontium and Rb/Sr variation diagram for the Kuradawe felsic pegmatite. F =melt fraction; Ms (VA) =vapor absent muscovite melting; Ms (VP) vapor present muscovite melting; Bt (VA) =vapor absent biotite melting. After Inger & Harris, (1993)…………………...
125
5.3
The evolution paths of KFP plotted in K/Rb vs. Rb after (Černý, 1991).
126
5.4
(A) The K/Cs versus Cs (B) The K/Rb versus Cs, trends from Daraban leucogranite to Kuradawe felsic pegmatite (after Černȳ et al., 1985)…..
127
Hafnium versus Zr/Hf ratio and fractionation trend from Daraban leucogranite to Kuradawe felsic pegmatite (after Linnen and Cuney, 2005)…………………………………………………………………..
128
5.2
5.5
XIV
5.6
5.7
5.8
5.9
5.10
5.11
(A) Binary diagram between Zr and Y for Kuradawe felsic pegmatite (KFP) and Daraban leucogranite (DG). (B) Binary diagram between Zr and Zr/Y ratio for KFP and DG. And shown the modeled fractional crystallization trends for granitic melt. Fractional mineral vectors for acidic composition illustrated for Y - Zr and Y - Zr/Y ratio relationships (distribution coefficients from a compilation by Rollinson, (1993)………………………………………………………
129
(La/Lu)N versus LaN diagrams showing the variation of REE contents of KFP by the fractionation of accessory minerals, particularly monazite. The arrows indicate the effect of fractional crystallization of allanite (Aln), apatite (Ap), monazite (Mnz), titanite (Ttn) and zircon (Zrn) on the composition of residual liquids and point towards the melt direction governed by each of these minerals (distribution coefficients from compilation by Rollinson, (1993)………………………………...
130
Chondrite normalized REE patterns for the Kuradawe felsic pegmatite, which extend the trend of the Daraban leucogranite as visible in shaded field cover (after Sun and McDonough, 1989)…………………………
132
(A) Y-Nb discriminate diagram and (B) Yb-Ta discriminant diagram, for Kuradawe felsic pegmatite after Pearce et al. (1984). (VAG) Volcanic arc granites, (syn-COLG) syn-collision granites, (WPG) within plate granites, and (ORG) Ocean Ridge Granites……………….
133
R1 = 4Si–11(Na + K)–2(Fe + Ti) versus R2 = 6 Ca + 2Mg + Al diagram for Kuradawe felsic pegmatite, after de la Roche et al. (1980) displaying the geotectonic fields (Bachelor and Bowden, 1995)………
134
The comparison of Ocean Ridge Granites (ORG) normalized multielement spider diagram of the Kuradawe felsic pegmatite with typical syn-collision granites (Syn-COLG) and post-collision granites (PostCOLG) after Pearce et al. (1984)………………………………………
135
XV
List of Tables Table 1.1
Chapter One
Page No.
Sampling and field discription of the Kuradawe felsic pegmatite dykes.
16
Chapter Two 2.1 2.2 2.3
2.4
Names and formulae of the tourmaline species currently recognized by the IMA and that occur in association with pegmatite (London, 2008)...
40
Tourmaline distribution at the Kuradawe felsic pegmatite…………….
41
Modal analysis (%) of ultramafic (host) rock showing mineral constituent. abbreviations: MUM-1= Mawat ultramafic sample 1; MUM-2= Mawat ultramafic sample 2; MUM-3= Mawat ultramafic sample 3………………………………………………………………..
49
Semi-quantitative modal percentage of minerals by the XRD methods………………………………………………………………..
52
Chapter Three 3.1 3.2 3.3 3.4
Major oxide analyzes and CIPW norms of some Kuradawe felsic pegmatite samples……………………………………………………..
71
Whole rocks trace element analysis of Kuradawe felsic pegmatite…….
85
Whole rock REE analyzes of Kuradawe felsic pegmatite…………….
95
Temperature and grain size in different Kuradawe felsic pegmatite…...
103
Chapter Four 4.1 4.2
Principal subdivision and characteristics of the five class of granitic pegmatite, after Černý and Ercit (2005)……………………………….. Subdivision of felsic pegmatites of the rare-element class, after Černý and Ercit, (2005)……………………………………………………….
XVI
112 113
CHAPTER ONE
INTRODUCTION
CHAPTER ONE INTRODUCTION 1.1 Preface Pegmatite defined as a very coarse-grain (greater than 2.5 mm) igneous rocks, and the abundance of crystals with skeletal, graphic, or other strongly directional growth-habits. Pegmatite occurs as sharply bounded homogeneous to zoned bodies within igneous or metamorphic host rocks, and usually of granitic composition, that tend to enrich in rare elements such as lithium, beryllium, tantalum, and others (Jackson, 1997; Clark & Steigeler 2000).
Pegmatites have long attracted interest for the colorful gemstones and fine mineral specimens that they provide. As the primary source of feldspar for glass and ceramic industries and quartz for silica glass and silicon microchip, pegmatite plays a mostly obscure but hugely important part in our economy and our everyday lives (Harald, 2015)
In geoscience, pegmatite been scrutinized for nearly two centuries because they are arguably among the most complex rocks known on Earth. Explaining their origins has become a challenge, and a measure of how well geoscientists understand the formation of crystals and rocks in general.
In this study the terms that have proposed for classification of Kuradawe felsic pegmatite at various scales. The classification begins at the regional scale, where schemes distinguish pegmatite on the basis of their inferred depth of formation, and on the basis of their signatures of rare-element enrichment. Moreover, the mineralogical study of Kuradawe felsic pegmatite have aided to understanding the conditions and the processes that form felsic pegmatite hosted in ultramafic rocks of Mawat ophiolite.
1
CHAPTER ONE
INTRODUCTION
1.2 Location of the studied area The Mawat ophiolite complex is located in northeast Iraq 30 km north of Sulaimani city and 5 km north of Chwarta district. It lies between longitudes (45o32'30"45o32'57" E) and latitudes (35o50'29" – 35o51'25" N). The felsic pegmatite rocks crop out in three locations, which lie in the northeast of Kuradawe village by 4 km (Figures 1.1, 1.2 and 1.3). The studied area has complex and highly topographic, the felsic pegmatite rock crop out in different altitudes and elevations as below: Location one: elevation 1961m, latitude (N 35o 50' 29") and longitude (E 45o 32' 30"). Location two: elevation 1954m, latitude (N 35o 50' 29.6") and longitude (E 45o 32' 29"). Location three: elevation 2059m, latitude (N 35o 51' 25") and longitude (E 45o 32' 57").
2
CHAPTER ONE
INTRODUCTION
Figure (1.1): (A) Regional tectonic map of the Kurdistan region of NE Iraq showing major tectonic subdivisions (after Al-kadhimi et al. (1996). (B) Geological map of the study area and showing the three locations of the felsic pegmatite, after (Mohammad et al. 2014).
3
Figure (1.2): Google earth image of the study area, showing locations of felsic pegmatite within ultramafic unit of Mawat ophiolite.
CHAPTER ONE INTRODUCTION
4
Figure (1.3): Digital elevation model map for the Mawat area and showing the location of the samples on the largest pegmatites dykes in the studied area.
CHAPTER ONE INTRODUCTION
5
CHAPTER ONE
INTRODUCTION
1.3 Tectonic setting The Tertiary NW-SE striking Zagros Orogenic Belt is an integral part of the AlpineHimalayan orogenic belt that stretches across much of southern Europe, Middle East, and the southwest Asia. The Zagros Orogenic Belt is a young continental convergence zone, which extends from eastern Turkey through northern Iraq and the length of Iran to the Straits of Hormuz, then into northern Oman (Moghadam & Stern, 2011). The Zagros Mountains are located on the boundary between the Arabia and Eurasia lithospheric plates, and formed during a collision between Eurasia and Arabia during the Cenozoic (Takin, 1972; Agard et al., 2005; Ali et al., 2012 and 2013).
In the Kurdistan region of northeastern Iraq the Zagros Mountains form a major mountain belt that can be divided from northeast to southwest into four parallel NW-SE– trending structural domains shown in (Figure 1.1 A). These are the Sanandaj-Sirjan Zone, the Imbricate Zone, the Zagros (High and Low) Fold and Thrust Belt, and the Mesopotamian Foreland Basin (Alavi, 2004; Omrani et al., 2008)
In Iraq the Sanandaj-Sirjan Zone comprises the entire narrow V-shaped salient into adjacent Iranian territory (Figure 1.1 A), a 30 to 40 km wide zone, composed mainly of deformed and metamorphosed Palaeozoic to Mesozoic phyllite, Cenomanian Kata-Rash volcanic rocks and the Meshaw granodiorite-granite intrusion. The Sanandaj-Sirjan Zone is regarded to be of Eurasian affinity. The southern active margin of the Iranian plate, which was accreted to the Arabian margin at the end of Neo-Tethys ocean closure (Berberian & King, 1981; Mohajjel et al. 2003; Mohammad et al. 2014). The Sanandaj-Sirjan Zones were thrust southwestward over the Imbricate Zone. The Main Zagros Reverse Fault that divided the two domains represents the suture between the Arabian and Iranian plates (Berberian & King, 1981; Agard et al. 2005). The Imbricate Zone composed of imbricated tectonic slices including Mawat Ophiolite Complex and Qulqula radiolarite. Mesozoic and Cenozoic sedimentary rocks and Walash volcanic rocks, in addition to thrust sheets derived from the Sanandaj-Sirjan Zone (Agard et al. 2005). The Imbricate Zone bound to the southwest by the High Zagros Reverse Fault (Berberian, 1995). The Fold and Thrust Belt characterized by well-developed folds involving the entire 12-14 km thick sedimentary cover of the Zagros Basin (Falcon, 1974; Colman-Sadd, 1978), which developed as a thrust-propagated fold of the foreland basin in response to compression between the 6
CHAPTER ONE
INTRODUCTION
Arabian and Iranian plates (Mohammad et al., 2014). On the base of wavelength and amplitude of the folds, the Zagros Fold and Thrust Belt in Iraq can be subdivided into a High Fold and Thrust Belt characterized by short wavelength and high amplitude and a Low Fold and Thrust Belt with long wavelength and low amplitude folds, the latter including the hydrocarbon-prolific Kirkuk embayment. The Mesopotamian Foreland Basin lies southwest of the Low Fold and Thrust belt. The proximal part of the foreland basin characterized by NW-SE–trending buried anticlines, including the hydrocarbon-prolific Dezful Embayment (Dunnington, 1968). Miocene to Quaternary detrital deposits (Bakhtyari Formation) fill the Mesopotamian Foreland Basin.
1.4 Local geology of the studied area The Mawat Ophiolite Complex is part of the Neo-Tethyan ophiolite belt of the Middle East and lies in the Zagros Imbricate Zone. The ophiolite cooling after magmatic crystallization age dated at 101 ± 5 Ma (K-Ar) by Aswad and Elias (1988), and appears to be synchronous with the formation ages of the Neyriz Ophiolite, [93–98 Ma (Ar-Ar); Ghazi et al. 1999]; The Kermanshah Ophiolite (95–98 Ma (Ar-Ar); Hassanipak et al. (2002) of Iran; The Samail Ophiolite of Oman [95 Ma (U-Pb): Tilton et al. 1981; Tippit et al. (1981); The Hasanbag ophiolite (106-92 Ma (Ar-Ar). The allochthonous Mawat Ophiolite Complex exposed over 250 km2 as a triangular, elevated area with significant topographic relief within the Imbricate Zone (Figure 1.4 A). The complex consists of various partial ophiolite sequences, represented by mantle tectonites (harzburgite and dunite) and gabbro intruded by minor silicic, intermediate and mafic bodies (Mirza and Ismail, 2007). Mantle tectonites are volumetrically predominant and tectonically overlie the mafic sequences due to overthrust. The mantle tectonite and mafic sequence of Mawat Ophiolite were in turn thrust over Paleocene-Eocene Walash Volcanic Formation (Ali et al., 2013), and both thrust over the Tertiary clastic Red bed Series (Figure 1.4 B).
The Kuradawe felsic pegmatite occurs as a series of NW-SE striking and to the NE dipping peraluminous, muscovite-bearing dykes of different widths (1–20m) within 7
CHAPTER ONE
INTRODUCTION
serpentinized harzburgite and dunite of the Mawat Ophiolite (Figure 1.1 B), in close association with the Mawat Shear Zone. In addition to the cross-cutting relationships, the sharp boundary between Kuradawe felsic pegmatite and host serpentinized peridotite is interpreted as an intrusive contact, showing that the Kuradawe felsic pegmatite is younger than the harzburgitic and dunite host rock.
Quartz grains in the felsic pegmatite show visible foliation and development of quartz ribbons. Field observations indicate that these felsic pegmatite dikes experienced younger deformation. This clearly indicated by abundant joints, fracturs and crusht that was probably synchronous with the tectonic emplacement of the host harzburgite slab.
8
Figure (1.4): (A) A-B cross-section across northeast Iraq showing major tectonic division and boundaries (Mohammad et al., 2014). (B) Geological cross-section from Azmur mountain to Diri (modified after Al-Qayim et al., 2012). (C) Stratigraphic columnar section of Chwarta-Mawat area and showing the felsic pegmatite.
CHAPTER ONE INTRODUCTION
9
CHAPTER ONE
INTRODUCTION
1.5 Previous works The early work of (Heron & Less, 1943) suggested that the northeastern part of Iraq represents a nappe zone. They subdivided the area into three parts: the nappe of igneous rocks, the metamorphic nappe, and nappe of radiolarian cherts and shale.
Heron & Less division in 1943 had later modified by (Lehner, 1954) who subdivided the area into the Jurassic radiolarian host block, the igneous and metamorphic nappe and the Tertiary sedimentary units.
Bolton, (1957) introduced the division of the area from east to west: 1- Trust zone which consists of (from bottom to top): Naopurdan series, Walash series and Qandil series. 2- Intermediate zone that consists of Cretaceous Qulqula series and Tertiary Red Bed. 3- Folded zone.
Smirnov & Nelidov, (1962) concluded that the Mawat complex consists of peridotite, gabbros, granodiorites and granophyres and they divided gabbroic rocks into normal gabbro and amphibolized gabbro.
Akif et al., (1972) studied the geology and mineralogy of ultramafic rocks in Ser Shiw area. They divided these rocks into dunite, chromites dunite, pyroxene peridotite, and pyroxene hornblendite.
Etabi, (1972) studied the petrography of Mawat igneous complex (basic and ultrabasic rocks) and indicated that the basic rocks are represented by gabbros and constitute the major part of the igneous complex.
Jassim, (1972) investigated the geology of the central sector of the Mawat igneous complex. He indicated that this area comprised the basic and ultrabasic igneous rocks and minor intrusions. He also recognized various types of banding in gabbro; they are rhythmic, injection, and alteration banding.
10
CHAPTER ONE
INTRODUCTION
Mashek & Etabi, (1973) studied the petrography of igneous and metamorphic rocks of Mawat ophiolite complex. They indicated that the pyroxenite rocks are younger than mafic rocks.
Al-Mehaidi, (1974) investigated the Mawat-Chwarta area. He produced a geological map of the area with detail description of all rock units. He also indicated that the Mawat nappe consists of Mawat ophiolite complex and Gimo sequence.
Al-Hashimi & Al-Mehaidi, (1975) studied the description of Cr, Ni, and Cu in Mawat ophiolite complex. They introduced maps to explain the distribution of these elements.
Al-Hassan, (1975) made a comparative study of Mawat and Penjwin igneous complexes and found similarities in the mineralogy, texture and chemistry of the igneous complexes of both. And he also indicated that these complexes had suffered similar postmagmatic history.
Jassim & Al-Hassan, (1977) made a comparison between the petrography and the origin of the Mawat and Penjwin igneous complexes. They concluded that the postmagmatic modification occurred during this emplacement and largely during thrusting in the climax of the Alpine orogeny.
Buda & Al-Hashimi, (1977) studied the petrology of Mawat ophiolite complex and showed that the gabbro are mostly cumulate but often show foliation due to high deformation.
Buday & Jassim, (1987) concluded that Mawat ophiolite complex (Upper Cretaceous) lies within the Penjwin Walash subzone, and they also found that banded gabbro is the main basic intrusion in the area.
Aqrawi, (1990) studied the petrochemistry and petrogenesis of ultramafic and gabbroic rocks around Root Mountain. And he indicated that the petrographic evidence of gabbroic rocks was characterized by textural features due to tectonic deformation, recrystallization alteration, and metamorphism. 11
CHAPTER ONE
INTRODUCTION
Zakaria, (1992) introduced the division of the gabbroic rocks on the basis of their mineral composition into amphibolized gabbro and meta gabbro.
Aswad, (1999) introduced the division of the Chwarta-Mawat area into; parautochthon, neo-autochthon, Tertiary sedimentary cover, allochthon Walash-Naopurdan nappe, and allochthon Mawat Nappe.
Farjo, (2006) studied geochemistry and petrogenesis of the volcanic rocks of Mawat ophiolite. He indicated that the Mawat ophiolite complex derived from fast-spreading centers.
Koyi (2006) studied the petrochemistry, petrogenesis & isotope dating of Walash volcanic rocks of Mawat-Chawarat area. He related these rocks to island arc tholeiite and calc-alkaline basalt of Middle-Eocene to Late-Eocene age.
Musa, (2007) studied the geochemistry and genesis of copper-iron mineralization and associated rocks in Waraz area, and he concluded that the studied gabbro had not reached the amount to regarded as a mineralization.
Mirza & Ismail, (2007) classified some granitoid (minor acidic intrusions) of the complex as plagiogranites. They provided that these rocks are metaluminous, low-K calcalkaline with mineralogical and geochemical characteristics of oceanic plagiogranite (trondhjemite).
Mirza, (2008) studied the petrogenesis of Mawat ophiolite complex and the associated chromite. She classified the primary rocks as tholeiitic and related to island arc tholeiites.
Mohammad, (2008) studied the petrology of Ultramafic and related rocks along Iraqi Zagros Thrust Zone. He proposed that peridotites indicate that they are mantle tectonite, rather than cumulate or replacive rocks. And they are mainly depleted harzburgite and dunite.
12
CHAPTER ONE
INTRODUCTION
Aziz, (2008) studied the petrogenesis, evolution and tectonics of the serpentinites of the Zagros suture zone. And concluded that two types of serpentinites are present in Mawat; first serpentinites directly related to ophiolitic massifs (ophiolite-serpentinite associate); second serpentinites mélange (within Walash volcano-sedimentary group) containing exotic blocks of metabasalt and metasediments.
Aziz et al., (2011) studied the Rb-Sr and Sm-Nd isotopes study of serpentinites and their impact on the tectonic setting of Zagros suture zone, NE Iraq. They gave the age of ophiolite serpentinite associate 80-110 Ma while the age of mélange serpentinite is 150200 Ma.
Ameen, (2012) studied the petrogenesis and geochronology of granitoid rocks in Mawat ophiolite. And he concluded that the Daraban Leucogranite rocks appear as small discontinuous dikes as well as a small elongated boss like intrusions in the field, and they intruded into harzburgite rocks of Mawat ophiolite complex. Ali, (2012) Geochemistry and geochronology of Tethyan – arc related Igneous rocks, NE Iraq. And he concluded that the disappearance of some original textural and mineralogical characteristics, due to the superimposed condition that prevailed during ocean-floor and subsequent hydrothermal alteration, this led to the appearance of secondary minerals that partially or completely replaced the original ones in both the Walash and Naopurdan volcanic rocks.
Mohammad et al., (2014) studied the geochemistry and Ar-Ar muscovite ages of Daraban Leucogranite, Mawat ophiolite, northeastern Iraq: Implications for Arabia-Eurasia continental collision. And he concluded that the volumetrical and compositionally of the leucogranitic dike of the Mawat Ophiolite were similar to crustal melt leucogranites from the Himalaya and other (high pressure) collisional environments.
13
CHAPTER ONE
INTRODUCTION
1.6 Aims of the study: 1. Identification and nomenclature of felsic pegmatite in Mawat ophiolite. 2. Anatomy and classification of Mawat felsic pegmatite. 3. Minerals & whole rocks investigate of major, trace and REE elements concentration. 4. Petrogensis of the Kuradawe felsic pegmatite. 5. Determine the tectonic setting of Mawat felsic pegmatite.
1.7 Field description The Kuradawe felsic pegmatite bodies were studied in the field using normal interpretative mapping method, GPS, Lense and compass. The Kuradawe felsic pegmatite composed of three dykes, and collecting forty five samples and descript in the field as showing in the Table (1.1). In the laboratory, hand specimen-slab examination of the structure and thin section petrography were performed.
1.8 Analytical techniques The compositions of minerals analyzed by Hitachi S-400N scanning electron microscope equipped with Oxford Inca EDS-WDS X-ray microanalysis system at Gothenburg University, Sweden. The analytical conditions were 20 KV, working distance 10 mm and 3.5nA current. Cobalt metal standard were used for calibration and checked with the Smithsonian mineral standard.
whole-rock analyses for major, trace elements and Rare earth element (REE). Where done by ALS Laboratory Group SL Seville Spain, using ICP-AES with the Lithium Borate fusion method as a whole rock package encoding ME-MS81d and ME-4ACD81.
Whole-rock analyses by the X-ray diffraction (Quality and Quantity) in the University of Leeds, School of Earth and Environment. The X-ray diffraction data collected on a Philips PW1050 diffractometer with a θ/2θ goniometer. Hiltonbrooks’ HBX software 14
CHAPTER ONE
INTRODUCTION
package was used to collect the data. CuKα radiation used with a graphite monochromator, divergence and anti-scatter slits each of 1° and receiving slit of 0.2°. The data collected over a range of 3-70° 2θ with a step size of 0.02° and counting at 2 sec/step. A power of 50kV, 40mA was placed on the tube.
Quantification of the mineralogical composition of the samples was carried out using the reference intensity ratio (RIRcor.) method. The method also known as the ‘matrix flushing’ method as the matrix absorption effects removed from the equation for quantitative analysis, Chung (1974).
15
CHAPTER ONE
INTRODUCTION
Table (1.1): Sampling and field discription of the Kuradawe felsic pegmatite dykes.
Dykes
Dyke (1)
Dyke (2)
Dyke (3)
E 45o 32' 30"
E 45o 32' 29"
E 45o 32' 57"
Latitude:
N 35o 50' 29"
N 35o 50' 29.6"
N 35o 51' 25"
Elevation:
1961 m
1954 m
2059 m
Samples No.
Longitude:
YO1,
YO2,
YO3, YO10, YO11, YO12, YO21,
YO22,
YO23,
YO4,
YO5,
YO6, YO13, YO14, YO15, YO24,
YO25,
YO26,
YO7,
YO8,
YO9, YO16, YO17, YO18, YO27,
YO28,
YO29,
YO31,
YO32,
YO5b,
YO6b
YO1b, YO2b, YO3b, YO19, YO4b.
YO20, YO30,
YO11b, YO12b.
YO33,
YO21b, YO22b, YO23b, YO24b. -This is the smallest -This
dyke
larger -This dyke is the larger
dyke in which the than the dyke number dyke in which the length length equal to 2.5m one in which the equal to 8m and the width and the width equal length equal to 3m is
General description
to 0.8m (Figure 1.5). -White
greater
than
4
m
and the width equal (Figure 1.6).
color, to 1.3 m.
-White color, the grain
medium grain size -White color, fine to size change in which the ranging from 1cm-5 medium grain size quartz is fine grain but cm. -They
ranging from 2mm- albite are
fractured body.
highly 2cm
and
tourmaline
crystal are very large
-The change
quartz and
grain grain ranging from 7cmfining 40cm,
toward the host rock.
and
larger
tourmaline crystal found in the dyke.
16
the
CHAPTER ONE
INTRODUCTION
Figure (1.5): Highly fracture dyke number one in the Kuradawe felsic pegmatite.
Figure (1.6): Larger dyke in the Kuradawe felsic pegmatite
17
CHAPTER TWO
PETROGRAPHY & MINERALOGY
CHAPTER TWO PETROGRAPHY AND MINERALOGY
2.1 Preface Petrographically most felsic pegmatite rock composed mainly of essential minerals like quartz, plagioclase, tourmaline, biotite, and muscovite. Identification, modal analysis, grain size measurements of primary phases play an important role in classification, crystallization sequences and thermal history of various types of felsic pegmatite.
Forty-five samples prepared for thin section and optical microscope examination. Samples are chosen based on the distance from the contact of the pegmatite bodies toward the center of the three pegmatite dikes in Mawat ophiolite complex. The thin sections are examined using Meiji polarized microscope to find out the mineral constituents, grain size distribution, and modal percentages of various phases. The semi-quantitative percentage (SEQXRD) was done by XRD methods to determine the percentage of the primary minerals from margin to the center of the bodies. Nine samples are chosen based on the distance from the country rocks (from margin to core of the pegmatite body), the results of SEQXRD is given in (Table 2.4) for the XRD diffractograms see (Appendix I)
2.2 Petrography 2.2.1 Petrography of host rock The Kuradawe felsic pegmatites hosted in both serpentinized harzburgite and serpentinized dunite rock units of Mawat ophiolite complex. Petrographically the host rocks composed of various proportions of the Primary minerals olivine, orthopyroxene, clinopyroxene and spinel. Primary phases partly replaced by secondary phase like serpentine polymorphs, chlorite and talc (Mohammad, 2008).
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2.2.2 Petrography of pegmatite dykes The mineral constituent and compositions of most pegmatite are substantially similar to those of ordinary igneous rocks (London, 2008). What distinguishes pegmatites from all other igneous rock types is their texture. For this reason, “felsic pegmatite” is better thought of as a textual variant of a more common igneous rock; in much the same way as “felsic porphyry” refers to a sharply bimodal grain-size. Any of the following textural attributes, individually or in combination, can be sufficient to classify an igneous rock as pegmatitic (London, 2008): ■ Extremely coarse grain-size in relation to normal igneous rocks of similar composition (Figure 2.1) ■ Extremely variable grain-size that increases with pegmatite thickness in a systematic fashion from margins to the center of a distinct body (Figure 2.2). ■ A prominence of skeletal crystal habits or graphic intergrowths (Figure 2.3).
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Figure (2. 1): Field photograph is showing very large elongated crystal of tourmaline in the KFP (dyke 3).
Figure (2. 2): Slab Showing the grain size distribution of tourmaline in Kuradawe felsic pegmatite coarsening from the margin to the center of the body (dyke 2).
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Figure (2. 3): Field photo is showing skeletal crystal of tourmaline, which appears as a black snowflake from KFP (dyke 3).
2.3 Textures of Kuradawe felsic pegmatite 2.3.1 Igneous textures 2.3.1.1 Perthitic Texture Perthitic texture can defined as exsolution lamellae of albite occurring in orthoclase or microcline (Nelson, 2004). Perthite types from studied pegmatite range from strings, rods and interpenetrating (Deer et al., 1992) (Figure 2.4). In the Kuradawe felsic pegmatite, perthite combinations are of albite intermixed with orthoclase (Figure 2.5 A).
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Figure (2. 4): Sketch showing different types of Perthite: (a) stringlets; (b) strings; (c) rods; (d) beads; (e) fractured beads; (f) interlocking; (g) interpenetrating; (h) and (j) replacement (Deer et al, .1992).
2.3.1.2 Graphic Texture A graphic texture is an igneous rock texture in which an intergrowth of two minerals has the appearance of runic writing. Graphic textures are most commonly intergrowths of quartz and alkali feldspar in which the quartz appears as V-shaped inclusions enclosed by the feldspar. A micrographic texture is a graphic intergrowth than can only be observed under the microscope (Deer et al., 1992). This type of texture is common in the Kuradawe felsic pegmatite in which the micrographic intergrowth of quartz in orthoclase is common (Figure 2.5 B).
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2.3.2 Metamorphic textures 2.3.2.1 Deformation Twins Minerals can deform by deformation twinning (or mechanical twinning or Flame-shape twinning) in addition to dislocation. In general, twinning occurs in the lower temperature range. Deformation twins can commonly distinguished from growth twins by their shape; deformation twins tapered while growth twins are often straight and stepped. Twins may restricted to certain parts of a crystal. Growth twins are bounded by zoning while deformation twins can concentrated at high strain sites such as the rim of crystals or sites where two crystals touch each other. Deformation twinning can also accommodate a limited amount of strain in specific crystallographic directions. It is common in calcite and plagioclase. Because some slip and twin directions are more effective than others (Deer et al., 1992). In the Kuradawe felsic pegmatite, this texture is common among the albite grains (Figure 2.5 C).
2.3.2.2 Corona structure A Corona is a zone of minerals, usually with the radial arrangement, around another mineral. It is a general term that has applied to reaction rims. A change in physicochemical conditions can give rise to porphyroblast growth or partial replacement of some minerals by others. Such replacement usually occurs along grain boundaries and causes the development of reaction rims (Passchier and Trouw. 2005). In Kuradawe felsic pegmatite, thin reaction rim of secondary muscovite observed along the rim of euhedral tourmaline grain in the wall zone (Figure 2.5 D).
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A
C
PETROGRAPHY & MINERALOGY
0.5mm
0.5mm
B
D
0.5mm
0.25mm
Figure (2. 5): Photomicrographs from KFP showing: (A) Strings and rods type perthitic texture, XP, SN: YO28. (B) Graphic intergrowth of quartz in orthoclase, XP. (C) Deformation twin in albite, XP, SN: YO15 (D) Corona structures in tourmaline mineral, XP. Note: for the abbreviations of minerals using the standard Kretz, (1983), and SN= Sample number.
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2.3.2.3 Kink Bands Kinking resembles twinning but is not so strictly limited to specific crystallographic planes and directions. Kinking is common in crystals with a single slip system such as micas but also occurs in quartz, feldspar, amphibole, aluminosilicate and pyroxenes at low temperature (Passchier and Trouw. 2005). In the Kuradawe felsic pegmatite, the kink bands are observed clearly in both muscovite and albite (Figures 2.6 A and 2.6 B).
2.3.2.4 Crenulation cleavage Crenulation cleavage is two foliations, one the initial cleavage and the other the plane of fold axes that crenulate the first one (Barker, 1990). While a pervasive cleavage forms by the alignment of platy or elongated crystals. A crenulation cleavage forms by the parallel alignment of the fold axial planes of crenulations of earlier fabrics with an orientation broadly perpendicular to the principle stress direction. Variations in the orientations of crenulations, however, can occur on a microscopic scale, in particular, adjacent to porphyroblasts. This texture observed and restricted to 10 cm border of the Kuradawe felsic pegmatite with host rock (Figure 2.6 C).
2.3.2.5 Granoblastic Texture A granoblastic texture is an equigranular texture in which crystals adopt a polygonal morphology with grain triple junctions of approximately 120 degrees. The formation of granoblastic textures occurs to minimize the combined surface energy of phases within a rock (Passchier and Trouw. 2005). The type of granoblastic texture is common among quartz grain in the core of Kuradawe felsic pegmatite. Quartz grains shows Granoblastic amoeboid texture because all the grains have anhedral irregular outlines (Figure 2.6 D).
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A
PETROGRAPHY & MINERALOGY
0.5mm
B
0.5mm
0.25mm
C
0.5mm
D
Figure (2. 6): Photomicrographs of KFP showing: (A) Kink bands texture in muscovite, XP, SN: YO14. (B) Kink bands texture in albite, XP, SN: YO26. (C) Asymmetrical crenulation cleavage in muscovite, XP, SN: YO6b. (D) Granoblastic (amoeboid) texture in quartz, XP, SN: YO24.
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2.3.2.6 Lepidoblastic Texture (after Lepidolite) A lepidoblastic texture is a texture in which platy or tabular minerals are aligned to produce a planar fabric. This texture is due to the parallel orientation during recrystallization of minerals with a flaky or scaly habit, e.g. mica, chlorite (Passchier and Trouw. 2005). The Kuradawe felsic pegmatite contains the folded lepidoblastic texture of the muscovite mineral along the contact with the host rock (Figure 2.7 A).
2.3.2.7 Porphyroblastic Texture A porphyroblast is a crystal grown during metamorphism that is significantly larger than the surrounding matrix. Porphyroblasts are commonly euhedral crystals and have often deflected the surrounding foliation. They also are frequently associated with strain shadows. Porphyroblasts form from mineral phases in a metamorphic rock that have more limited nucleation than the matrix minerals. Porphyroblasts can be described as syntectonic or post-tectonic depending on whether they formed during or after the deformation represented by the foliation in the rock (Passchier and Trouw. 2005).
Porphyroblasts are containing inclusion trails whose orientations match with the external schistosity and that do not deflect foliations are often considered post-tectonic. Porphyroblasts containing abundant inclusions are frequently termed poikiloblasts showing Figure (2.8).
1. Pre-tectonic porphyroblasts are rarely described and seem to be uncommon in areas affected by regional metamorphism, except possibly in low-pressure/hightemperature metamorphism. Even in the case of contact metamorphism, some deformation may predate porphyroblast growth. If present, inclusions in pretectonic porphyroblasts are randomly oriented. 2. Intertectonic porphyroblasts Porphyroblasts that have grown over a secondary foliation, and surrounded by a matrix affected by a later deformation phase that did not leave any record in the porphyroblast.
3. Syntectonic porphyroblasts have grown during a single phase of deformation Dn and are the most frequently encountered type of porphyroblasts in nature,
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probably because deformation has a catalyzing effect on mineral nucleation and diffusion rates. Inclusion patterns curved in syntectonic porphyroblasts and random or straight in pre- and inter-tectonic porphyroblasts. 4. Pos-tectonic porphyroblasts This group is easy to define by the absence of deflection of Se, strain shadows, undulose extinction or other evidence of deformation, which is common to pre- syn- and inter-tectonic. If inclusions are present, Si is continuous with Se even if folded.
The Kurdawe felsic pegmatite is the Pre-tectonic porphyroblasts because the central part of the main crystal does not contain any strain (Figure 2.7 B).
0.5mm
0.5mm
A
B
Figure (2.7): Photomicrographs from KFP showing: (A) Folded Lepidoblastic texture in muscovite, XP. (B) Pre-tectonic porphyroblastic texture, XP, SN: YO17.
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Figure (2. 8): Schematic representation of pre-tectonic, sin-tectonic, inter-tectonic and posttectonic porphyroblast growth. The upper part of the diagram refers to deformation resulting in a single foliation or deformation of an earlier foliation without folding; the lower part considers deformation resulting in crenulation of order foliation (Passchier and Trouw, 2005).
2.3.2.8 Mica fish Micas deform mainly by slip, therefore, show abundant evidence for accommodation mechanisms such as pressure solution and fracturing (Kronenberg et al. 1990, Shea and Kronenberg 1992, Mares and Kronenberg 1993). Folding and kinks are particularly common in muscovite of Kuradawe felsic pegmatite (Figures 2.6 A and 2.7 A). Commonly, folding occurs on the outside and pressure solution or kinking in the core of a folded crystal. Fractures usually associated with a deflection of basal planes and lead to the barrel or fish-shaped boudinaged grains (Figures 2.10 A, B, and C). Grain boundary migration and recrystallization support medium to high-grade recrystallization (Bell 1998).
Of all mineral fish, white mica is most common. Their initial shape is probably due to a combination of the factors mentioned above. (Ten Grotenhuis et al. 2003) Show a number of white mica fish shapes that recognized as showing in (Figure 2.9). Each group is 29
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considered to result from a particular combination of mechanisms. Mica fish (muscovite) in the Kuradawe felsic pegmatite represent the group 1 and 2 may have attained their apparently stable inclined position by back rotation from an original position approximately parallel to the foliation to a new stable position. The shape of group 2 fish is thought to evolve from group 1 by drag along zones of concentrated shear, localized along the upper and lower contacts, comparable to the development of σ - type mantled clasts.
Mica fish of group 3 can easily be attained by slip on (001), starting from a position parallel to the foliation. Mica fish of group 4 are thought to have formed by antithetic slip on (001) from grains with an original high angle between internal cleavage and foliation. Alternatively they could have developed from fish of groups 1 or 2 by further removal of the upper and lower parts. Mica fish of group 5 mica fish explained as originated from short. Thick micas in a similar way as group 4 ones, but with additional modification by removal along C'-type shear bands, at a small synthetic angle with the foliation. Mica fish of group 6 micas may result from drag folding along C'-type shear bands.
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A
B Figure (2.9): (A) The main types of white mica fish recognized in thin section. (B) Inferred development of the different types of mica fish (after Ten Grotenhuis et al. 2003).
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PETROGRAPHY & MINERALOGY
0.25mm
0.5mm
B
0.25mm
0.25mm
D
C
Figure (2.10): Photomicrographs from KFP in the sample number YO31 showing: (A) Mica fish (muscovite) mineral, XP. (B) Mica fish (muscovite) mineral, XP. (C) Mica fish (muscovite) mineral, XP. (D) Crenulation cleavage in Muscovite and undulose extinction in quartz, XP.
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2.4 Mineral constituent of the Kuradawe felsic pegmatite: The minerals that occur in any rock depend on the rock's overall chemistry and the pressure and temperature conditions under which it formed. Most felsic pegmatites composed of the same minerals found in ordinary granites, that is, quartz, Plagioclase (albite), alkali-feldspars (orthoclase, microcline), micas, tourmaline, and on occasion some
common accessory minerals such as, monazite, columbite, cordierite, rutile, zircon, and andalusite. Also chlorite is a secondary mineral. Detailed optical study and petrographical characteristics of observed minerals in the pegmatite rock samples from Mawat ophiolite discussed as follows:
2.4.1 Essential Minerals 2.4.1.1 Quartz Quartz is the essential mineral in the Kuradawe felsic pegmatite present in all rock samples, most of the quartz grain is subhedral to anhedral and interstitial to feldspar and other minerals. It occurs as small or large (bimodal) crystals and shows undulose extinction and has multiple fractures as showing in (Figures 2.11 A and B), grain size varies from 0.3mm to 0.6mm. Quartz forms the massive central units referred to as pegmatite core and decrease the ratio of the wall and border of the pegmatite. Skeletal and graphic habits are common in the quartz mineral showing as (Figure 2.5 A).
2.4.1.2 Alkali-feldspars (Orthoclase and Microcline) Alkali feldspar is one of the essential mineral in Kuradawe felsic pegmatite; abundant alkali feldspar occurs as large blocky, elongate to anhedral to (rarely) euhedral, crystals exhibiting perfect cleavage. These crystals are white, to gray, to a mottled brown in color. Elongate alkali feldspar crystals usually oriented perpendicular to the pegmatite/wall rock contact. Blocky, euhedral alkali feldspar also commonly surrounds quartz cores.
Orthoclase in Kuradawe felsic pegmatite characterized by a special type of Carlsbad twinning (Figure 2.11 C). Alkali feldspar is commonly micro perthitic to perthitic, although
visually homogeneous crystals also occur. Perthite types range from strings and rods to interpenetrating (Deer et al., 1966) (Figure 2.5 B). Microcline is also present in Kuradawe
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felsic pegmatite near to the core of the body, with subhedral to anhedral crystals forming cross-hatched twining (Figure 2.11 D).
2.4.1.3 Plagioclase Plagioclase appears to be the most dominant mineral in the Kuradawe felsic pegmatite and occurs in many forms. The grain size is range from 0.1 mm to 5 cm. The grain size of Albite increase toward the core of the KFP.
In zoned pegmatite; Cameron et al (1949) reported that the mole percent of anorthite component in plagioclase decreases from An12 at the border to An2 or less in the innermost portions. XRD analysis of nine samples is showing that the Kuradawe felsic pegmatite plagioclase restricted to Albite. Carlsbad-twinning are common in the albite mineral according to albite law showing as (Figure 2.14 A), also chessboard texture more common in the Kuradawe felsic pegmatite as showing in (Figure 2.14 B).
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A
C
PETROGRAPHY & MINERALOGY
0.5mm
B
0.5mm
D
0.5mm
0.5mm
Figure (2. 11): Photomicrograph from KFP showing: (A) undulose extinction in quartz mineral, XP, SN: YO24. (B) The intergranular aggregate of quartz, XP, SN: YO24 (C) Carlsbad twinning in orthoclase mineral, XP. (D) Cross-hatched twining in Microcline mineral, XP, SN: YO25.
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Figure (2. 12): Field photograph of Albite mineral in the Kuradawe felsic pegmatite.
2.4.1.4 Muscovite Muscovite is of bimodal origin, Primary muscovite, occurs as fine-grained to coarsegrained (2mm to 5cm) crystals in Kuradawe felsic pegmatite dikes. Primary muscovite shows acicular to tabular fine-grained (<2mm). Muscovite occurs on the border of the Pegmatite bodies with host rock mineralogical zones. It is characterized by a perfect cleavage with slight distortion (Figure 2.14 C), it has a colorless under plane polarized. Toward the core of the Pegmatite the grain size increase until it reaches a maximum length of 5 cm. Secondary Muscovite occurs as a pseudomorphic replacement of the aluminosilicates (feldspar and tourmaline) (London, 2008). In the Kuradawe felsic pegmatite this type of muscovite formed by the alteration of tourmaline, observed along the rim and the core (Figure 2.14 D).
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Figure (2. 13): Field photo is showing muscovite in the Kuradawe felsic pegmatite.
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0.5mm
0.25mm
B
A
0.25mm
0.5mm
D
C
Figure (2. 14): Photomicrographs from KFP showing: (A) Chessboard texture in the albite minerals, XP. (B) Carlsbad-twinning in albite mineral, XP. (C). Perfect cleavage in muscovite mineral, XP. (D). Fine grain muscovite formed from the alteration tourmaline mineral, XP, SN: YO6b.
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2.4.1.5 Tourmaline Black tourmaline is a common essential mineral in the Kuradawe felsic pegmatite. Tourmaline is present as euhedral or subhedral with grain size (1mm to 30cm). The tourmaline species relevant to pegmatite and currently recognized by the International Mineralogical Association (IMA) listed in Table (2.1). The observed color of Tourmaline sample suggests that the tourmaline in KFP belong to the schorl-dravite series. Modal percentage of tourmaline decrease toward the core of the Pegmatite bodies while the size increased. Elongate Tourmaline usually oriented perpendicular to the pegmatite/wall rock contact tourmaline. (Figures 2.15 A and B). Muscovite and biotite of numerous thick subparallel packets were observed as alteration products of tourmaline along fracture and cleavage, suggesting that the tourmaline reacted directly to form muscovite. Černý, P., (1982) observed that various minerals in pegmatites, especially Al-rich minerals, are subject to late sericite replacement by residual fluids. K+ and H+ metasomatism commonly results in assemblages containing muscovite as an alteration product (Černý and Burt 1984). Aluminous minerals either react directly to form muscovite as a final alteration product or indirectly through various intermediate stages as the fluids evolve, and equilibrium attained.
Tourmaline reflects the presence of boron in pegmatite-forming environments. Boron is a highly effective flux for pegmatite-forming melts at wt. % levels. As a result of fluxing effects, the boron-rich melt can migrate farther from the source, to lower temperatures, and with higher contents of dissolved H2O. Much of the boron originally contained by pegmatite-forming melt is lost to the surrounding host rocks because pegmatites are poor in the iron and magnesium needed to make the common species of tourmaline. Consequently, abundant tourmaline associated with pegmatites is found where boron from the pegmatite mixes with iron and magnesium from the host rocks. Upon emplacement, iron and magnesium diffuse into the pegmatite-forming magma to make tourmaline (London, 2008). The Kuradawe felsic pegmatite gets iron and magnesium from the serpentinized harzburgite and serpentinized dunite rock in the Mawat ophiolite complex to form tourmaline mineral along the border.
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Table (2. 1): Names and formulae of the tourmaline species currently recognized by the IMA and that occur in association with pegmatite (London, 2008).
Species
Formula
Species
Formula
Schorl
NaFe3Al6(BO3)3Si6O18(OH)4
Rossmanite
□LiAl2Al6(BO3)3 Si6O18(OH)4
Dravite
NaMg3Al6(BO3)Si6O18(OH)4
Liddicatite
CaLiAlAl6(BO3)3 Si6O18(OH)3F
Olenite
NaAl3Al6(BO3)3Si6O18O3(OH)
Uvite
CaMg3MgAl5(BO3)3 Si6O18(OH)3F
Foitite
□Fe2AlAl6(BO3)3 Si6O18(OH)4
Elbaite
NaLi1.5Al1.5Al6(BO3)3
Buergerite
NaFe3Al6(BO3)3Si6O18O3F
Si6O18(OH)4
Figure (2. 15): Field photo showing: (A) Pointed (tapered) tourmaline minerals in the border pegmatite zones. (B) Large tourmaline minerals in the core pegmatite zones.
Tourmaline color and grain size change from border to the core of Pegmatite zones. Kuradawe felsic pegmatite shows the several color of tourmaline mineral according to the occurrences, each type tends to occur characteristically in a given zone showing as (Table 2.2). Fine-grained, dark green tourmaline occurs in the border zone as euhedral (Figure 2.16 A). Light-brown tourmaline occurs in the border zone near the host-rock (Figure 2.16 B), tapered prisms. These crystals are commonly fractured perpendicular to the C-axis, and filled with the fine-grained matrix characteristic of the zone.
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A very distinctive assemblage of tourmaline especially intergrown with coarse muscovite also occurs in the wall zone. In this zone, the tourmaline is euhedral, forming fine to medium grained, slender prisms. Some of these are finely color-zoned (Figure 2.16 D). With light blue to green color (Figure 2.16 C).
Table (2. 2): Tourmaline distribution at the Kuradawe felsic pegmatite.
Pegmatite zones
Color
Grain size
Notes
Border zone (1)
Brown
Very fine-fine
Grain size scheme:
Border zone (2)
Dark green
Very fine-fine
-very fine = <6mm
Wall zone
Blue-green
Fine-medium
-fine = 6mm to 2.5cm
Intermediate subzone (1)
Dark blue to green
Fine-medium
Intermediate subzone (2)
medium
Core subzone (1)
Green to light green Light blue to gray
Core subzone (2)
Pink to brown
Medium-coarse
Fine-medium
-medium = 2.5cm to 10cm -coarse = 10cm to 30 cm
Dark blue to green tourmaline occurs in the intermediate zones toward wall zone (Figure 2.17 A), occurs as subhedral to anhedral crystals that form fine to medium grained aggregates. Tourmaline aggregates intergrown with the quartz and albite matrix of this zone. Tourmaline of moderate to light green occurs in the intermediate zone toward the core zone (Figure 2.17 B). They are prismatic crystals, euhedral tourmaline from skeletal crystals associated with quartz and albite (Figure 2.3). Tourmaline in the pegmatite core consists of two texturally distinct varieties. Very light blue, fine-grained, subhedral tourmaline is intergrown with quartz and albite (Figure 2.17 C). Pink, euhedral, coarsegrained Tourmaline also occurs in the core zone associated with quartz and albite (Figure 2.17 D).
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A
C
PETROGRAPHY & MINERALOGY
0.25mm
B
0.5mm
D
0.5mm
0.25mm
Figure (2. 16): Photomicrographs from KFP showing: (A) Dark green tourmaline occur in the border zone, PPL, sample number (SN): YO6 (B) Brown tourmaline occurs in the border zone, PPL, SN: YO9 (C) Blue to green tourmaline occurs in the wall zone, PPL, SN: YO15 (D) Zoned tourmaline mineral occurs in the wall zone, PPL, SN: YO3
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0.5mm
0.5mm
A
B
0.5mm
0.5mm
C
D
Figure (2.17): Photomicrographs from KFP showing: (A) Dark blue to green tourmaline occur in the intermediate zone, PPL, SN: YO22 (B) Green to light green tourmaline occurs in the intermediate zone, PPL, SN: YO29 (C) Light blue to gray tourmaline occurs in the core zone, PPL, SN: YO22b (D) Pink tourmaline mineral occurs in the core zone, PPL, SN: YO32
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2.4.2 Accessory minerals: 2.4.2.1 Biotite Biotite in the Kuradawe felsic pegmatite are accessory mineral (2-3 modal %), Subhedral to anhedral grains, reddish to brown color, fine grain less than 2mm in size. It shows one perfect set of cleavage (Figure 2.18 A). Two type of biotite present in the Kuradawe felsic pegmatite, primary biotite formed by the crystallization of magma, and they are small grain in this pegmatite associated with secondary muscovite and plagioclase, the secondary biotite produced by alteration of tourmaline (Rinaldi et al. 1972) this type of biotite more reddish color and coarser grain size (Figure 2.18 B).
2.4.2.2 Zircon Zircon in the Kuradawe felsic pegmatite occurs in trace quantities. Zircon in the KFP samples appeared as euhedral crystal and with very high relief as showing in (Figures 2.18 C and D). They are fine grain less than (0.1mm), and they are colorless to pale brown color under microscope.
2.4.2.3 Andalusite Andalusite occurs as an accessory mineral in many types of felsic igneous rocks, including rhyolites, granites, pegmatites. Andalusite mineral present in the border zone of Kuradawe felsic pegmatite. It is characterized by a square prism and elongated grain, grain size range from 0.5 to 2 mm (Figure 2.19 A), high relief, andalusite association with muscovite and cordierite mineral in the KFP.
2.4.2.4 Rutile Rutile mineral associated with potassium feldspar, quartz, and muscovite mineral in the border zone of Kuradawe felsic pegmatite. Grain size range from 0.5 to 2 mm, dark reddish brown color with the very high relief (Figure 2.19 B).
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0.5mm
0.25mm
B
A
C
0.25mm
D
0.5mm
Figure (2.18): Photomicrographs from KFP showing: (A) Primary biotite minerals in the KFP, PPL. (B) Biotite minerals formed from the alteration of tourmaline, PPL, SN: YO32 (C). Zircon mineral, XP, SN: YO14 (D) High relief zircon mineral, PPL, SN: YO14.
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2.4.2.5 Cordierite Cordierite is another accessory mineral in Kuradawe felsic pegmatite. They are associated with muscovite and albite mineral in the border zone of KFP. Cordierite grains are colorless, Euhedral to subhedral crystals, grain size range from 1 to 3 mm (Figure 2.19 C).
2.4.2.6 Columbite Columbite-group minerals are (manganocolumbite, ferrocolumbite, manganotantalite, and ferrotantalite). Only ferrocolumbite minerals observed throughout the Kuradawe felsic pegmatite, the columbites are euhedral crystals, and they are less than 1mm in size (Figure 2.19 D). They are most invariable associated with albite minerals in the wall and intermediate zone of the Kuradawe felsic pegmatite.
2.4.2.7 Apatite Apatite is a very common early-formed accessory mineral in nearly all type of igneous rocks. Apatite is also concentrated by late magmatic segregation, and it appears in granite pegmatite (Deer et al., 1992). In the KFP apatite is found in the border zone, and characterized by high relief, very fine grain range from 0.3 to 1 mm (Figure 2.20 A).
2.4.2.8 Monazite Monazite occurs in euhedral light green to colorless grains, which are usually small size less than 1 mm (Figures 2.20 B and C). It characterized by the high relief and maximum interference color of lower fourth order.
2.4.3 Secondary Mineral Chlorite is the secondary mineral in the Kuradawe felsic pegmatite. Chlorite is fine grain and has perfect cleavage, green color, and pleochroic (Figure 2.20 D).
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0.5mm
0.5mm
B
A
0.5mm
0.5mm
D
C
Figure (2. 19): Photomicrographs from KFP showing: (A) Euhedral to subhedral grains of andalusite mineral, XP, SN: YO17 (B) Rutile mineral in the border zone of KFP, PPL, SN: YO12b (C) Cordierite mineral in the KFP, XP, SN: YO17 (D) Ferrocolumbite mineral in the KFP, PPL, SN: YO15.
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0.5mm
B
A
0.25mm
0.25mm
0.25mm
D
C
Figure (2. 20): Photomicrographs from KFP showing: (A) Apatite grains in the KFP, XP, SN: YO17 (B) Monazite mineral in the border zone of KFP, PPL, SN: YO17 (C) Monazite mineral in the KFP, XP, SN: YO17 (D) Secondary chlorite mineral in the KFP, PPL, SN: YO6.
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2.5 Mineral composition of host rock Three samples collected of the host rock with in the Kuradawe felsic pegmatite. Two samples collected in the locations one and two, composed of harzburgite and one sample collected in the location three, composed of dunite. Harzburgite host rock consists of olivine (75-78%), orthopyroxene (16-18%), clinopyroxene (2%), serpentine (1-2%), chromite (1%) by visual estimation modal analysis (Figure 2.21). The essential minerals composed of olivine and orthopyroxene, the accessory mineral composed of clinopyroxene, and chromite, the secondary mineral is serpentine, that is due to the serpentinization of the olivine mineral. Dunite host rock consists of olivine (>90%), orthopyroxene (3-4%), clinopyroxene (1-2%), spenal (1%), and serpentine (1%) by visual estimation modal analysis as showing in (Table 2.3).
Table (2. 3): Modal analysis (%) of ultramafic (host) rock showing mineral constituent. abbreviations: MUM-1= Mawat ultramafic sample 1; MUM-2= Mawat ultramafic sample 2; MUM-3= Mawat ultramafic sample 3.
Sample No.
MUM-1-
Minerals
MUM-2-
MUM-3-
Modal %
Olivine Orthopyroxene Clinopyroxene Spenal Chromite
78 16 2 0
75 18 2 0
91 4 2 1
1
1
0
Serpentine
2 99
2 98
1 99
Total %
49
Essential Accessory Secondary
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Figure (2. 21): Plotting of host rock (ultramafic) on ternary diagram after (Le Maitre, 2002).
2-6 Mineralogical classification Semi-quantitative XRD percentage of primary minerals of the Kuradawe felsic pegmatite indicate that the KFP can classified as (alkali-feldspar quartz syenite, alkali feldspar granite, and quartzolite) on the QAP diagram Le Maitre (2002) (Figure 2.22). The scattered in the fields attributed to different minerals domain zones of pegmatite.
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Figure (2. 22): Plotting of Kuradawe felsic pegmatite data (Modal %) on a preliminary QAP classification of acidic rocks for field use (after Streckeisen, 1976). Q=quartz; A=albite (An0An5) +Orthoclase (microcline); P= anorthite + albite (An5-An100) after (Le Maitre, 2002).
2.7 Mineralogical zones in Kuradawe felsic pegmatite Based on field observation, SEMQXRD (Table 2.4), and Petrographic analysis of primary phase, five mineralogical zones have been identified in the Kuradawe felsic pegmatite in order from margin to the core. Each zone identified by type and quantity of different mineral phases present. These zones include a) Q-A-M (quartz-albite- muscovite) zone, b) Q-A (quartz-albite) zone, c) Q-P-M (quartz-perthite-muscovite) zone, d) Q-MI (quartz-microcline) zone, and f) Q (quartz) zone. The Approximate percentage for each of the zones given in (Figure 2.23).
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Table (2. 4): Semi-quantitative modal percentage of minerals by the XRD methods. Sample ID Quartz Plagioclase % (Albite) % YO17 9.0 31.1 YO14 3.8 52.3 YO1b 3.1 32.1 YO12b 42.8 55.7 YO5b 29.5 58.3 YO25 26.4 28.8 YO28 16.3 86.4 YO31 34.6 52.6 YO24 95.1 3.8
Orthoclase (Microcline) % 0.0 0.0 0.0 0.0 0.0 38.1 0.0 0.0 0.0
Mica Tourmaline Chlorite Total Pegmatite % % % Zones 38.7 16.4 5.8 100.9 Border zone 24.6 19.9 0.0 100.5 26.6 34.9 0.0 96.8 Wall zone 0.0 0.0 0.0 98.5 2.2 5.9 1.6 97.4 0.0 6.5 0.0 99.8 Intermediate 0.0 0.0 0.0 102.6 Zones 9.3 4.2 0.0 100.8 1.5 0.0 0.0 100.4 Core zone
The (Q-A-M) zone is fine to coarse grained and consists of varying proportions of quartz, albite, and muscovite (Figure 2.23). Several accessory minerals are present including tourmaline, and andalusite. Tourmaline occurs as tapered crystals with grain size range (0.5mm-2cm). Secondary mineral chlorite is present in small quantities.
The (Q-A) zone characteristically contain the assemblage quartz and albite. Albite is most abundant and is typically intergrown with quartz. Tourmaline minerals also present in this zone, and the size are coarser than before zone.
The (Q-P-M) zone is distinguished by the presence of coarse grained perthite crystals with quartz, muscovite, and albite, and tourmaline mineral is present. Tourmaline in this zone is course.
The (Q-MI) zone distinguished by the presence of coarse-grained to very coarse-grained potassium feldspar crystal (microcline) and quartz. Several accessory minerals are present including albite, and very coarse crystal of tourmaline.
The (Q) mineralogical zone of Kuradawe felsic pegmatite contains principally quartz, albite, and a small amount of muscovite. In the (Q) zone, tourmaline crystal is very coarse more than 40cm length and 30cm width.
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Figure (2.23): Approximate mineral percentage of mineralogical zone in Kuradawe felsic pegmatite. Abbreviations: Q= Quartz; M= Muscovite; A= Albite; P= Perthite; MI= Microcline.
2.8 Mineral chemistry
After careful petrographic study, ten polished thin sections from the Kuradawe felsic pegmatite selected for the study of mineral chemistry. The detailed analytical techniques used for determination of mineral compositions of KFP given in chapter one. To achieve these goals and to confirm the field observations, the electron probe microanalyses, X-Ray diffractometric and polarizing microscopy techniques used. The polished thin sections of the KFP were studied under the polarizing microscope to identify different mineral phase, which described in detail in the mineralogy of KFP. Further to confirm this phase, the electron probe microanalysis used.
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2.8.1 Plagioclase Plagioclase along with quartz and alkali feldspar are the major constituents of the felsic pegmatite. These three minerals are also present in all the zones of zoned pegmatites except the core zone, which mainly composed of quartz. However, the proportion of these three minerals is always variable in these zones (Jahns, 1953; Černý, 1982a; Foord et al., 1986). As far as the plagioclase concerned, most of the felsic pegmatites are mainly composed of plagioclase, either albite or oligoclase in composition but certain pegmatites entirely composed of albite or variety “cleavelandite” and the proportion of oligoclase is very low (Norton and Redden, 1990). The Kuradawe felsic pegmatite mainly composed of albite, alkali feldspar and quartz. The electron probe microanalysis for sixteen spots (in the different zone) of plagioclase mineral have analyzed in the samples, and its formula calculated based on eight oxygen. Representative microprobe analyses of plagioclase from Kuradawe felsic pegmatite given in (Appendix II, Table 2.5). Indicate that the plagioclase is albite (Ab97 – An02 – Or01) in composition and are similar to the well-known pegmatites elsewhere in the world (Jahns, 1953, 1955; Jahns and Tuttle, 1963; Černý, 1982a and Černý et al., 1984). The plagioclase are plotting on the ternary diagram of Klien et al., 1993. All plagioclase of KFP samples fall in the albite zone (Figure 2.25), and albite content of plagioclase increasing toward the center of the pegmatite body from Ab92 to Ab97. The zoned KFP have albite as the major constituent of all the zones (border zone, wall zone, intermediate zone, and core zone), but the proportion of orthoclase content is relatively higher as compared to albite, especially in the first intermediate zone.
2.8.2 Alkali feldspar The electron probe microanalysis for eight spots of alkali feldspar in the Kuradawe felsic pegmatite given in (Appendix II, Table 2.6). Major element compositions of the KFP rocks are: SiO2 is ranging from 64.1% to 66.2%, Al2O3 from 16.97% to 18.38%, K2O from 15.03% to 17.56% and Na2O from 0.23% to 1.48%. All the other cations are less than 0.1%. The data suggest that the alkali feldspar in the KFP is mostly orthoclase in composition (Or92 – Ab09 – An01) as showing in (Figure 2.25). However, in thin section study some microperthite textures are observed. All that analyzed orthoclase grains are agreement with the standard analyses of pegmatitic orthoclase. 54
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Figure (2. 24): Backscattered image of albite and K-feldspar (Orthoclase), plus symbol represent selected points for EMPA analyses, SN: YO5b.
Figure (2. 25): Nomenclature and composition of the feldspars (Alkali feldspar and plagioclase feldspar) of the Kuradawe felsic pegmatite, onto the albite (Ab) – orthoclase (Or) – anorthite (An) triangular diagram after (Deer et al., 1966).
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2.8.3 Muscovite Muscovite is the main primary mineral of the Kuradawe felsic pegmatite, and common in all zones but the size increasing toward the central of the pegmatite body, the common associations of muscovite are two feldspar (plagioclase and alkali feldspar), quartz and tourmaline. Eighteen spots of muscovite in various samples of studied pegmatite analyzed by the electron probe microanalyzer, and the data given in (Appendix II, Table 2.7). The mineral assemblage, texture and chemistry of muscovite in the KFP indicate that these are primary and of magmatic in origin (Figure 2.26). Fe/ (Fe+Mg) ratios from all locations ranged from 0.370 to 1 indicating the muscovite is Fe-rich. The backscattered image of muscovite in the KFP as showing in figure (2.27)
Figure (2. 26): Composition of muscovite in the KFP. It shows the primary (magmatic) origin of the analyzed muscovite on the Mg–Ti–Na (a.p.f.u) triangular diagram from Miller et al., (1981).
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Figure (2. 27): Backscattered image of muscovite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO4b
2.8.4 Tourmaline Tourmaline is a primary mineral in the Kuradawe felsic pegmatite, the term tourmaline not only used as a single mineral, but it is also used for a group of minerals. The main compositional varieties found in this mineral group are the magnesium tourmalines or dravites, the iron tourmalines and/or schorl and the alkali tourmaline and/or elbaites. In these varieties, the Y-sites are predominantly composed of Mg, Fe+2 and Li respectively. There is also a continuous series between dravites and schorl and between schorl and elbaite, but there appears to be an immiscibility gap between elbaite and dravites. The ironrich varieties found in the granitic rocks and belong to the schrol-elbaite series (London, 1986; Černý et al., 1985; Kleck and foord, 1999). Twelve spots of the tourmaline mineral in the Kuradawe felsic pegmatite are analyzed by using electron probe microanalyzer, and the results given in (Appendix II, Table 2.8). Li presents a more complicated problem, however, as Li can occur in tourmaline in variable amounts at the Y site. As the EPMA don‘t analyze the Li, the Li can be calculated stoichiometrically based on microprobe data. If all other cations have analyzed and a proper cation basis of normalization is established (Burns et al., 1994, Dutrow & Henry, 57
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2000). Li can be calculated by the equation (Li (apfu) = 15 - (Y site cations + Z site cations + tetrahedral site cations (apfu)). As Z and T sites fully occupied, Li was estimated by subtracting the sum of the Y-site cations from 3 (Li=3-ΣY), assuming no vacancies in the octahedral sites (Henry & Dutrow, 1996). Tourmaline data was calculated based on Selway and Xiong, 2003, Excel sheet software. The tourmaline minerals fall in the fields of alkali groups and X-vacancy groups in the Ca-(X) vacancy - Na+K ternary diagrams of Henry et al., (2011)( Figure 2.28).
The tourmalines of KFP are iron-rich variety called schorl, and some of these tourmalines are foitite (Figure 2.29). The SiO2 in these schorl is up to 35 wt. %, while the Al2O3, FeO and Na2O are ranging from 33.40% to 35.98%, 8.23% to 18.54%, and 1.06% to 2.65% respectively. Chemically, the schorl and foitite are almost identical in their Si and Al contents but the two major ions (Fe and Na) are deficient in foitite and rich in schorl. Therefore, both the iron-rich varieties (foitite and schrol) of tourmaline are present in the Kuradawe felsic pegmatite. Back scattered image of tourmaline in KFP as showing in figure (2.30).
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Primary tourmaline groups
Alkali group ggroup
X-site vacant group
Figure (2. 28): Classification of the tourmaline super group minerals of Kuradawe felsic pegmatite by chemical composition. The primary division (Top) is made according to the dominant occupancy of the X site to give the X-site vacant, alkali, and calcic groups. The secondary division (Bottom) is made according to the dominant occupancy of the Y site (Mg, Fe+2, 2Li or 1.5 Li) with the Z site =Al dominant and V= OH dominant for X-site vacant group and alkali group, after Henry et al., (2011).
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Figure (2. 29): Plotting Kuradawe felsic pegmatite tourmaline data on the binary diagram of Mg/Mg+Fe+2 vs. X□/ (X□+Na+1+K+1) after Henry et al., (2011).
Figure (2. 30): Backscattered image of tourmaline in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO1b.
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2.8.5 Zircon Four spots of zircon grains within the Kuradawe felsic pegmatite are analyzed by the electron probe microanalyzer, and the results given in (Appendix II, Table 2.9). The chemical composition of these zircons is ZrO2 ranging from 59.2% to 69.2% and SiO2 are ranging from 30.8% to 38.7% and a small amount of hafnium associated with zircons in the KFP. The most common range for Hf/Zr ratio in zircons is 0.02–0.04 (Deer et al., 1992), the zircons from the Kuradawe felsic pegmatite fall in this range equal to 0.03. The backscattered image of zircon in the KFP as showing in Figure (2.31).
Figure (2. 31): Backscattered image of zircon in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO12b.
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2.8.6 Monazite Monazite is the accessory mineral in the Kuradawe felsic pegmatite, two spots of monazite grains within the KFP are analyzed by the electron probe microanalyzer, and the results given in (Appendix II, Table 2.10). Monazite of Kuradawe felsic pegmatite is characterized by high Ce- concentration, its concentration ranges from 0.29 to 0.46 (a.p.f.u.) and La concentration is about 0.0 to 0.15 (a.p.f.u.). And enriched in REE and P. The
substitution of REE governs the compositional variations of monazite by Th, U, Ca and Y. The most grains monazite present especially in the border zone of KFP. The backscattered image of monazite in the KFP as showing in figure (2.32).
Figure (2. 32): Backscattered image of monazite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO14.
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2.8.7 Columbite Five spots of columbite grains within the KFP analyzed by the electron probe microanalyzer and the results are given in (Appendix II, Table 2.11), the average result of the oxide weight percent are as follows: Nb2O5, 71.19%; Ta2O5, 1.88%; MnO, 5.41%; FeO, 14.76%; TiO2, 5.06%; and Sc2O3, 1.7%. According to the Linnen and Cuney (2005) classification of the columbite mineral, the Kuradawe felsic pegmatite is the ferrocolumbite (Figure 2.33). Columbite-group minerals with 1-3 % Sc2O3 referred to as scandian columbite- tantalite (Wise et al. 1998) so that the columbite mineral in the KFP is scandian columbite because the ratio of Sc2O3 between 1.5 % to 2.06 %. Crystals of columbite-tantalite that zoned with respect to variations in Mn/ (Mn +Fe) and Ta/ (Ta + Nb) do not show zoning in terms of Sc (Figure 2.34). In all specimens examined, the distribution of Sc appears to be homogeneous throughout the crystal from the rim to core.
Figure (2. 33): Diagram showing the classification and compositional trends of the columbitetantalite, after Linnen and Cuney (2005).
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Figure (2. 34): Backscattered image of Columbite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO15.
2.8.8 Cordierite Seven spots of cordierite grains within the KFP analyzed by the electron probe microanalyzer and the results given in (Appendix II, Table 2.12). Cordierite is the group of mineral (cordierite and sekaninaite); they are present in the border zone of the Kuradawe felsic pegmatite. They are characterized by the high ratio of MgO% ranges from 12.4 to 12.69%, while FeO% ranges from 2.6 to 3.2%, indicate that the cordierite in the KFP are Mg-cordierite (Figure 2.35). Cordierite in the KFP associated with muscovite, the zoning are not present in the cordierite of KFP. The backscattered image of Mg-cordierite in the KFP is showing in figure (2.36).
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Figure (2. 35): Compositional diagram is showing cordierite classification of the KFP, after Černý et al., (1997).
Figure (2. 36): Backscattered image of cordierite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO17.
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2.8.9 Andalusite Andalusite is the accessory mineral in the Kuradawe felsic pegmatite. Six spots of andalusite grains within the KFP are analyzed by the electron probe microanalyzer. The result are given in (Appendix II, Table 2.13); they are present only in the border zone of KFP. The general chemical composition of andalusite is Al2SiO5, in which 62% is Al2O3 and 37.84% is SiO2, they are associated with muscovite. The backscattered image of andalusite in the KFP is showing in figure (2.37).
Figure (2. 37): Backscattered image of andalusite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO17.
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2.8.10 Apatite Apatite is the common accessory mineral group found in most of the igneous rocks. Besides, it is also found in the sedimentary and metamorphic rocks. The most common varieties found in this group are fluorapatite, chlorapatite, hydroxylapatite, and carbonate apatite (Deer et al., 1966).
Apatite observed in the Kuradawe felsic pegmatite, six spots of apatite grains analyzed by electron probe microanalyzer and the results are given in (Appendix II, Table 2.14). Apatite in the KFP associated with muscovite and tourmaline. Apatite of KFP is the chlorapatite due to the chemical composition is CaO ranges from 49.2% to 51.15%, P2O5 ranges from 46.31% to 47.84%, Cl ranges from 1.6% to 2.03%, and the ratio of F less than 1%. The backscattered image of apatite in the KFP as showing in figure (2.38)
Figure (2. 38): Backscattered image of apatite in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO17.
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2.8.11 Rutile Rutile is observed to be in samples from the Kuradawe felsic pegmatite. It most frequently found in association with albite and muscovite. Eleven spot of rutile grains are analyzed by electron probe microanalyzer, and the results given in (Appendix II, Table 2.15). The chemical composition of rutile from the KFP are average 1.49% FeO, 5.65%
Nb2O5, 91.75% TiO2, and 0.75% SiO2. The backscattered image of rutile in the KFP as showing in figure (2.39)
Figure (2. 39): Backscattered image of rutile in the KFP, plus symbol represent selected points for EMPA analyses, SN: YO14.
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CHAPTER THREE GEOCHEMISTRY 3.1 Preface Nine samples of pegmatites were analyzed for whole rock major, trace and rare earth elements using inductively-coupled plasma atomic emission spectrophotometry (ICPAES), at ALS Laboratories Group SL, In Spain. The samples are selected based on the petrographical study to reduce the effect of the alteration and to be representative for various mineralogical zones as observed in the previous chapter. The analytical results are presented in tables (3.1, 3.2, and 3.3). The principal purpose of this chapter is to show how geochemical data can used for interpretation of different issue of pegmatite in Mawat ophiolite complex including:
1- Identification and nomenclature of Kuradawe felsic pegmatite and norm percentage calculation. 2- Distribution of elements in different zones and testing the possibility of elemental zoning. 3- Identify the family type of Kuradawe felsic pegmatite. 4- Estimate the crystallization conditions of Kuradawe felsic pegmatite (pressure and temperature).
3.2 Major Oxides 3.2.1 Silica (SiO2) The percentage of silica oxide in the Kuradawe felsic pegmatite (KFP) are vary according to the zones of pegmatite (47.4% to 98.1%) with an average 70.47%. The ratios of silica oxide gradually increase toward the core zone of pegmatite (Figure 3.1). As silica oxide increases, alumina and magnesia decrease and show linear negative trend (Figure 3.2 A and B). This variation in SiO2 is attributed to increasing of Albite and quartz percentages toward the core of the Kuradawe felsic pegmatite, as approved by CIPW norm percentage (Table 3.1).
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Figure (3.1): Distribution pattern of silica oxide across the Kuradawe felsic pegmatite.
Figure (3.2): (A) Harker diagram between SiO2 and Al2O3 in the Kuradawe felsic pegmatite (KFP). (B) Harker diagram between SiO2 and MgO in the (KFP) (after Harker, 1909).
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Table (3.1): Major oxide analyzes and CIPW norms of some Kuradawe felsic pegmatite samples.
Rock type Kuradawe felsic pegmatite Sample No. YO17 YO14 YO1b YO15 YO4b YO26 YO5b YO25 YO24 Major elements (wt. %) SiO2
47.4
57.2
60.0
71.1
76.2
74.2
78.3
71.8
98.1
TiO2
0.17
0.23
0.07
0.13
0.13
0.01
0.05
0.01
0.01
Al2O3
35.8
28.9
24.3
16.3
14.85 16.45 12.95 14.45
1.61
Fe 2O3 MnO MgO CaO Na2O
0.99 0.01 1.68 0.66 2.57
0.67 0.01 0.53 0.62 6.17
1.18 0.02 0.41 0.55 8.34
3.06 0.07 0.3 0.23 6.09
0.92 0.01 0.24 0.48 6.76
0.54 0.01 0.05 0.34 9.64
0.91 0.01 0.08 0.24 4.99
0.44 0.01 0.02 0.11 3.75
1.2 0.01 0.02 0.03 0.89
K2O
5.35
3.78
1.33
0.32
0.56
0.15
2.81
7.41
0.03
P2O5
0.14
0.15
0.18
0.07
0.05
0.09
0.1
0.07
0.01
1.34 97.7 38.23 2.3777 2.5129
0.71 98.4 14.87 2.455 2.543
0.56 100.8 31.72 1.9038 2.0287
0.27 101.8 14.16 1.624 1.68
0.44 100.9 13.54 1.6107 1.6603
LOI 4.54 2.96 Total 99.3 101.2 Mg# 75.14 58.49 A/CNK 4.172 2.734 A/NK 4.52 2.905 CIPW Norms Quartz 8.28 4.88 Zircon 0.01 0.01 Anorthite 2.67 2.16 Hypersthene 3.98 1.15 Albite 25.32 55.92 Orthoclase 39.92 25.37 Apatite 0.31 0.30 Ilmenite 0.01 0.01 Corundum 18.82 9.68 Rutile 0.12 0.15 Hematite 0.58 0.36 Total 100.0 100.0 bdl = below detection limit.
5.07 35.61 33.61 16.66 37.79 0.01 0.01 0.01 …….. …….. 1.64 0.69 1.98 1.03 0.51 0.90 0.65 0.50 0.10 0.16 76.83 55.07 58.16 80.84 42.49 9.23 2.07 3.52 0.90 17.40 0.37 0.14 0.10 0.17 0.19 0.03 0.09 0.01 0.01 0.01 6.00 4.00 1.58 0.02 0.96 0.03 0.03 0.08 …….. 0.02 0.63 1.63 0.47 0.27 0.46 100.7 100.0 100.0 100.0 100.0
71
0.17 0.06 98.2 102.0 7.49 2.88 1.282 1.695 1.295 1.75 21.59 …….. 0.09 0.04 32.21 45.57 0.13 0.01 0.14 …….. 0.24 100.0
91.50 …….. 0.08 0.04 7.51 0.18 0.02 0.01 0.05 0.00 0.61 100.0
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3.2.2 Aluminum Oxide (Al2O3) In the KFP samples, the percentage of Al2O3 ranges between 1.61%-35.8% with an average 18.4% (Table 3.1). The alumina oxides are decreasing gradually toward the pegmatite core with the maximum percentage in the border and wall pegmatite zones (Figure 3.3). The high ratio of Al2O3 in border zone from the Kuradawe felsic pegmatite attributed to the occurrence of Al-rich phases including Cordierite, andalusite, and muscovite. As Al2O3 decreases, MgO and CaO also decreases (Figures 3.4 A and B).
Figure (3.3): Distribution pattern of Aluminum Oxide across the Kuradawe felsic pegmatite zones.
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Figure (3.4): (A) Binary plot of CaO% versus Al2O3%. (B) The binary plot of MgO% versus Al2O3%.
3.2.3 Sodium Oxide (Na2O) In the Kuradawe felsic pegmatite, the percentage of Na2O show a bimodal pattern with a first peak at wall zone attributed to the dominance of schorl in this zone. The second highest peak recorded in the intermediate zone of the pegmatite body which reflect the dominance of albite in this zone (Figure 3.5). The Na2O in KFP range between 9.64% – 0.89% with an average of 5.46%, the Na2O % show increasing with CaO% and decreasing with K2O% (Figures 3.6 A and B).
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Figure (3.5): Distribution pattern of Sodium oxide (Na2O %) across the Kuradawe felsic pegmatite.
Figure (3.6): (A) The binary plot of Na2O % versus CaO %. (B) The binary plot of Na2O % versus K2O%.
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3.2.4 Potassium Oxide (K2O) The ratio of potassium oxide ranges from 0.03% -7.41% with an average of 2.4% (Table 3.1). The concentration of potassium oxide in the Kuradawe felsic pegmatite is variable across the pegmatite zones. K2O percentage show bimodal distribution pattern with a high concentration in both border and intermediate zones (Figure 3.7). The high concentration in the border zone attributed to the dominance of muscovite mineral whereas the high concentration in the intermediate zone due to the dominance of both microcline and orthoclase mineral in this zone.
Figure (3.7): Distribution pattern of potassium oxide (K2O %) across the Kuradawe felsic pegmatite.
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3.2.5 Calcium Oxide (CaO) The Low percentage of calcium oxide observed in the Kuradawe felsic pegmatite. The ratio of CaO change between 0.03% - 0.66%, with an average of 0.36%. The CaO pattern shows gradual decreasing toward the pegmatite core (Figure 3.8). Abnormal decreasing and negative anomalies observed in the wall zone of KFP, which may be due to the dominance of Na-rich tourmaline. Low concentration of CaO in the Kuradawe suggest that the plagioclase phases in KFP is albite, which was supported by both SEMQXRD and CIPW norm % (Table 3.1).
‘
Figure (3.8): Distribution pattern of calcium oxide (CaO %) across the Kuradawe felsic pegmatite.
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3.2.6 Magnesium Oxide (MgO) Kuradawe felsic pegmatite rock characterized by very low content magnesium oxide, range between 0.02% - 1.68% with an average of 0.37% (Table 3.1). These concentration is increasing in the border zone due to the occurrence of tourmaline minerals (Figure 3.9) followed by gradual decreasing toward the core of KFP.
Figure (3.9): Distribution pattern of Magnesium oxide (MgO %) across the Kuradawe felsic pegmatite.
3.2.7 Iron Oxide (Fe2O3) Kuradawe felsic pegmatite rock characterized by very low content of iron oxide. The concentration range from 0.44% - 3.06% with an average of 1.1% (Table 3.1). The Fe2O3 pattern shows approximately flat pattern across the pegmatite body with abrupt increasing in the wall zone due to the presence of tourmaline and a small quantity of biotite in this zone. (Figure 3.10).
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Figure (3.10): Distribution pattern of Iron oxide (Fe2O3 %) across the Kuradawe felsic pegmatite.
The bar chart below for major oxides concentration of KFP show that SiO2 has the highest percentages while MgO, Fe2O3, K2O, Na2O, and CaO are relatively low (Figure 3.11). Suggesting that the Kuradawe felsic Pegmatite geochemically classified as granitic pegmatite. Al2O3 ranging from 1.61 – 35.8 wt. % with an average of 18.7 wt. %, in the KFP samples and this reflected by the existence of corundum in CIPW norm suggesting that the parental rock was of sedimentary origin.
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Figure (3.11): Bar chart of major elements concentration across the Kuradawe felsic pegmatite.
3.2.8 Other Oxides and LOI The Kuradawe felsic pegmatite characterized by a very low concentration of TiO2 ranging between 0.01% - 0.57%, P2O5 ranging from 0.01% - 0.18%, MnO ranging between 0.01% - 0.02%, LOI ranging between 0.06% - 4.54% (Table 3-1). No clear pattern is shown in TiO2, P2O5 and MnO across in the Kuradawe felsic pegmatite zones because some very low concentration.
3.3 Nomenclature of the Kuradawe felsic pegmatite In the normative Ab-Or-An diagram (Figure 3.12), most of the samples plots of Kuradawe felsic pegmatite rocks fall in the trondhjemite (albite) and granite field. The observed variation in the areas is either primarily due to different zones exist in KFP, and the calculated normative percentage of Ab-Or-An. The CIPW only calculate anhydrous mineral and neglect hydrous mineral in case of KFP (Figure 3.13).
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Figure (3.12): Normative Ab-Or-An diagram for the Pegmatite rocks of the study area, with dividing lines according to O’Connor, (1965), Ab= Albite, Or= Orthoclase, An= Anorthite.
Figure (3.13): Bar chart of major mineral composition by CIPW norms in different Kuradawe felsic pegmatite zones.
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In KFP, hydrous mineral mica group and tourmaline group are dominance mineral in the border and wall zones. In addition, on SEMQXRD and Petro graphical study no orthoclase observed in these tow zone, while in CIPW the orthoclase is the dominance mineral. To solve this inconsistency in the mineral percentage, we can address the problem by some isochemical reactions as follow:
1- Muscovite
KAlSi3O8 + Al2O3+ H2O → KAl3Si3O10(OH)2 K-feldspar + corundum + H2O = muscovite
(Ferguson and Al-Ameen, 1985)
And
KAlSi3O8 + Al2SiO5 +H2O → KAl2Si3AlO10 (OH) 2 + SiO2 K-feldspar + andalusite + H2O = muscovite + quartz
(Ferguson and Al-Ameen, 1985)
2-Tourmaline
2.9 Muscovite + 3.0 B+3 +2.2 O2 + 0.5 Na+ = Tourmaline + 2.1 K+ + 2.9 SiO2 + 2.5 H2O (Jung and Peter, 1998)
In the Al2O3-CaO-(Na2O+K2O) diagram (Figure 3.14), all samples of the Kuradawe felsic pegmatite rocks fall in the field of peraluminous. In Fe2O3-(Na2O+K2O)-MgO (AFM) diagram (Figure 3.15) shows increasing of Fe2O3 with the decreasing of MgO during the initial stage of differentiation. In the later stage of differentiation, increasing the alkali with a depletion of Fe2O3. Most of the plots of the Kuradawe felsic pegmatite rocks fall in the field of calc-alkaline series except two samples fall in the field of tholeiitic due to the high ratio of tourmaline mineral in these samples. According to the Wright’s (1969) diagram the Kurdawe felsic pegmatite rocks fall in the calc-alkaline field (Figure 3.16).
ACF diagram (Figure 3.17) and some distinctive chemical properties of the Kuradawe felsic pegmatite rocks of the area indicate that these felsic pegmatite rocks of are mostly Stype felsic pegmatite. As proposed by Whalen et al., (1987), in some discrimination diagrams with FeOtot/MgO, Zr and Zn versus 10000Ga/Al (Figure 3.18), the investigated KFP falls in the field of I- and S-types granites.
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Figure (3-14): Al2O3 — CaO — (Na2O+K2O) diagram.
Figure (3.15): Fe2O3-Na2O+K2O-MgO (AFM) diagram.
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Figure (3.16): Plot Kuradawe felsic pegmatite rocks on the of Wright’s (1969) diagram, alkalinity index = Al2O3+CaO+Na2O+K2O/Al2O3+CaO-Na2O+K2O.
Figure (3.17): ACF ternary diagram for the type of Kuradawe felsic pegmatite rocks, after (Hyndman, 1985) Molar ratio: A = Al2O3–Na2O–K2O, C = CaO, F = Fe2O3+MgO.
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Figure (3.18): Zr and Zn versus 10000*Ga/Al genetic classification diagrams for A-type granitoid (Whalen et al., 1987), showing a significant position of the Kuradawe felsic pegmatite.
3.4 Trace elements Trace element is a chemical element whose concentration is less than 0.1% of a rock's composition. Trace element compositions for the Kuradawe felsic pegmatites rock samples given in (Table 3.2). The trace element in the Kuradawe felsic pegmatite rocks grouped into compatible and incompatible trace elements, also the incompatible trace elements divided into large ion lithophile elements (LILE) and high field strength elements (HFSE).
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Table (3.2): Whole rocks trace element analysis of Kuradawe felsic pegmatite. Rock type
Kuradawe felsic pegmatite
Sample No.
YO17 YO14 YO1b YO15 YO4b YO26 YO5b YO25 YO24 Detection limit(ppm)
Trace element (ppm) Ba 2310 986 Co 1 bdl Cs 4.77 6.09 Ga 34.2 39.3 Hf 4.2 6.5 Nb 91.3 92.4 Rb 121.5 127.5 Sn 9 12 Sr 200 52.1 Ta 8.7 8.8 Th 15.1 20.6 U 9 9.91 W 6 3 Zr 74 99 Y 67.2 81.5 Cr bdl bdl Ni 3 bdl V bdl bdl Zn 5 6 Sc 3 5 Tl bdl bdl Pb bdl bdl Cu 1 1 Li 20 10
666 1 4.98 33.4 4.3 101 38 3 138 10.3 12.4 7.24
31.3 1 1.33 40.9 5.2 228 22.3 5 18.7 14.5 31.6 8.9
52.2 1 7.11 20 2.8 41.5 45.3 3 28 4.4 8.17 3.65
37 bdl 0.01 20.2 0.2 8.4 2.5 bdl 40.5 2.1 0.65 2.07
396 bdl 5.71 12.7 1.2 22.4 106 bdl 36.8 2.4 3.04 2.02
130.5 bdl 0.2 10.9 0.3 6.3 85.8 bdl 36.4 0.8 0.39 0.45
8.5 bdl 0.09 1.7 1.1 3.8 2.2 bdl 1.9 2 0.21 0.28
0.5 1 0.01 0.1 0.2 0.2 0.2 1 0.1 0.1 0.05 0.05
1 46 29.5 10 3 bdl 30 8 bdl 2 4 bdl
2 54 50.1 30 2 bdl 135 26 bdl bdl 3 bdl
3 43 50.8 30 1 bdl 17 2 bdl 8 4 bdl
bdl 4 5.6 30 bdl bdl 5 bdl bdl 2 3 bdl
9 15 8.9 10 5 bdl 7 2 bdl 9 4 bdl
bdl 5 0.9 20 5 bdl 5 bdl bdl 6 3 bdl
bdl 3 bdl 40 3 bdl 9 bdl bdl 6 5 bdl
1 2 0.5 10 1 5 2 1 10 2 1 10
bdl= below detection limit
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3.4.1 Compatible trace elements Compatible trace element in the Kuradawe felsic pegmatite rock samples comprises Ni, Co, Cr, and Sc. The concentration pattern of both Ni and Co are indicating homogeneous concentration across the pegmatite body (Figure 3.19), the low and homogeneous concentration attributed to the original composition of protolith and that the rock not contaminated by Ni and Co of the host rock. The concentration of Scandium (Sc) show unimodal distribution pattern with the highest concentration recorded wall zone, attributed to the occurrence of columbite in this zone. The Cr distribution pattern shows flat unimodal in the wall zone which attributed to the dominance of tourmaline in the wall zone and the high concentration in the core zone (Figure 3.19). The mechanisms that appear to control the composition of tourmaline at these localities are dominant substitution Al+3 ↔ Cr +3. The low concentration of Cr at border suggest that the rock not contaminated by Cr of the host rock (Figure 3.19).
Figure (3.19): Distribution pattern of compatible elements across the Kuradawe felsic pegmatite. Sc = Scandium, Cr = Chromium, Co = Cobalt, Ni = Nickel.
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3.4.2 Incompatible trace elements Incompatible element is an element that is unsuitable in charge and size to the cation sites of the minerals. They are defined by the partition coefficient between rockforming minerals and melt being much smaller than one (Albarede, 2003). They prefer to remain in the liquid phase rather than the solid phase of the melt. Incompatible trace elements divided into large ion lithophile elements (LILE) and high field strength elements (HFSE).
3.4.2.1 Large-ion lithophile elements (LILE) Includes elements that have large ionic radius, the Kuradawe felsic pegmatite consists of rubidium (Rb), cesium (Cs), strontium (Sr), barium (Ba) elements. The concentration of large ion lithophile element change due to the fractionation of some minerals. Ba, Rb, and Sr appear especially abundant (Figures 3.20, 3.21, and 3.22) while Cs is the very low concentration in the Kuradawe felsic pegmatite (Figure 3.23).
The concentration of Rb and Sr range between 2.2ppm – 121.5ppm and 1.9ppm – 200 ppm respectively (Table 3.2). The High concentration of Rb and Sr due to substitution with K2O in the crystal structure of both muscovite and K-feldspar ( Rb+1 ↔ K+1). Thus, the first positive anomalies of Rb in the border zone is due to the dominance of muscovite in this zone. The second positive anomalies are recorded in the inner intermediate zone, reflecting the existence of K-feldspar in this zone (Figures 3.20 and 3.21). Ba distribution shows similar behavior as Rb across the KFP zones suggests that dominance substitution is Ba+1↔K+1 (Figure 3.22). As the Sr is a substitute for Ca ( Sr+2↔Ca+2 ), the Sr distribution pattern reflects the Ca-phases such that the border zone of KFP is controlled by phosphate phases ( monazite and apatite ). Where as wall zone of KFP show, the positive Sr anomalies indicate the existence of albitite with plenty of Ca in the crystal structure. However, the concentration of Cs is very low with an average (3.36 ppm). The Cs show zigzag pattern reflecting the effect of K-bearing mineral (Figure 3.23). Among the major elements (K2O) is the only one for which Cs can substitute. The lower electronegativity and ionization potential of Cs+ relative to those of K+ impart a more “ionic” character to Cs-O bonds. However, the behavior of Cs in igneous and postmagmatic events is govern by its large ionic radius (1.67 Ao) relative to that of K+ (1.33 Ao) (Černȳ et al., 1985).
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Figure (3.20): Distribution pattern of rubidium (Rb) across the Kuradawe felsic pegmatite zones.
Figure (3.21): Distribution pattern of strontium (Sr) across the Kuradawe felsic pegmatite zones.
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Figure (3.22): Distribution pattern of barium (Ba) across the Kuradawe felsic pegmatite zones.
Figure (3.23): Distribution pattern of cesium (Cs) across the Kuradawe felsic pegmatite zones.
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3.4.2.2 High field strength elements (HFSE) This group includes elements of large ionic valences (or high charges). The Kuradawe felsic pegmatite contain most of the (HFSE) in different concentration (Table 3.2), such as zirconium (Zr) 3ppm - 99 ppm, hafnium (Hf) 0.2ppm - 6.5 ppm, thorium (Th) 0.21ppm - 31.6 ppm, uranium (U) 0.28ppm - 9.91 ppm, niobium (Nb) 3.8ppm - 228 ppm, and tantalum (Ta) 0.8ppm - 14.5 ppm.
The concentration of Zirconium (Zr) in the border zone is high and decrease toward the core of KFP (Figure 3.24), due to the presence of zirconium mineral in the border zone. Hafnium is also decreasing toward the core of KFP (Figure 3.25). The relation between zirconium and hafnium are directly proportion (Figure 3.26), suggesting that the zircon and hafnium substitution each other (Zr+4↔ Hf+4).
Figure (3.24): Distribution pattern of zirconium (Zr) across the Kuradawe felsic pegmatite zones.
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Figure (3.25): Distribution pattern of hafnium (Hf) across the Kuradawe felsic pegmatite zones.
Figure (3.26): Binary plot between hafnium (Hf) and zirconium (Zr) in the Kuradawe felsic pegmatite zones.
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Tantalum and niobium are highly incompatible in quartz and feldspar (Rollinson, 1993). Thus, their bulk distribution coefficients are typically very small in the Intermediate and core of Kuradawe felsic pegmatite zones. However, they are compatible in muscovite and partition strongly into columbite minerals. The concentration of niobium (Nb) and tantalum (Ta) in the Kuradawe felsic pegmatite change and decreasing toward the pegmatite core due to the minerals fractionation (Figure 3.27 and 3.28). The concentration of thorium (Th) and uranium (U) change and decreasing from the border to core of Kuradawe felsic pegmatite zones, the high concentration of thorium in the wall zone due to th columbite mineral in this zone, and the high concentration of uranium in the border zone due to the monazite mineral in this zone. (Figuer 3.29, and 3.30).
Figure (3.27): Distribution pattern of niobium (Nb) across the Kuradawe felsic pegmatite zones.
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Figure (3.28): Distribution pattern of tantalum (Ta) across the Kuradawe felsic pegmatite zones.
Figure (3.29): Distribution pattern of thorium (Th) across the Kuradawe felsic pegmatite zones.
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Figure (3.30): Distribution pattern of uranium (U) across the Kuradawe felsic pegmatite zones.
3.5 REE elements The rare-earth elements (REEs) geochemical data are obtained for all rocks sample of Kuradawe felsic pegmatite. Include the 14 natural lanthanide elements; lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu). The REEs divided into light REE (La to Sm) and heavy REE (Eu to Lu) (Rollinson, 1993), the results are given in (Table 3.3). The concentration of light rare earth element and heavy rare earth element ploted across the pegmatite zones (Figure 3.31 and 3.32), the Kuradawe felsic pegmatite show uniform distribution pattern of LREE and HREE, with LREE being more enriched relative to HREE.
The summation of LREE and summation HREE concentration pattern show
gradual decreasing toward the core of the pegmatite bodies. Moreover, the relation between light REE and heavy REE in deferent zone are variable with the light REE been
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more enriched as compared to heavy REE in the border zone with inverse relation toward the core zone (Figure 3.33).
Table (3.3): Whole rock REE analyzes of Kuradawe felsic pegmatite. Rock type Sample No. YO17 Rare earth element (ppm) La 24.1 Ce 61.1 Pr 7.34 Nd 26.3 Sm 7.35 Eu 0.12 Gd 7.71 Tb 1.36 Dy 9.28 Ho 2.11 Er 6.59 Tm 1.02 Yb 6.35 Lu 1.01 ∑ REE 161.74 Eu/Eu* 0.05 (La/Sm)N 1.798 (La/Yb)N 2.3 Total LREE 126.19 Total HREE 35.55
YO14
Kuradawe felsic pegmatite YO1b YO15 YO4b YO26 YO5b YO25 YO24 Detection limit
19.7 59.8 7.59 28.3 8.77 0.06 9.06 1.68 11.1 2.39 7.65 1.2 8.13 1.25 166.68 0.02 1.23 1.469
3.2 13.5 2.1 8.2 3.72 0.08 3.4 0.71 4.64 0.84 2.7 0.51 3.39 0.46 47.45 0.07 0.472 0.572
124.16 42.52
30.72 16.73
3.2 21.7 3.5 15 7.74 <0.03 7.06 1.43 7.79 1.27 3.35 0.78 5.47 0.78 79.07 0 0.227 0.355
51.14 27.93
95
9 27.7 3.8 13.6 4.64 0.03 4.93 1.04 6.77 1.46 4.41 0.81 4.95 0.75 83.89 0.02 1.06 1.102
58.74 25.15
<0.5 0.8 <0.5 <0.5 3.5 <0.5 0.3 0.6 0.07 1.3 2.3 0.2 0.92 0.94 0.22 0.13 0.03 0.04 0.72 0.85 <0.05 0.14 0.17 <0.01 0.73 1.24 0.16 0.13 0.21 <0.01 0.37 0.7 0.04 0.1 0.13 0.02 0.62 1.07 0.2 0.08 0.14 0.01 5.54 12.68 0.96 0.47 0.1 0.01 0.85 0.467 1.78 1.321 0.453 2.2
2.52 3.02
8.14 4.54
0.49 0.47
<0.5 <0.5 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 0.04 <0.01 0.04 0 1 1
0 0.04
0.5 0.5 0.03 0.1 0.03 0.03 0.05 0.01 0.05 0.01 0.03 0.01 0.03 0.01
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Figure (3.31): Total light rare earth element pattern across the Kuradawe felsic pegmatite zones.
Figure (3.32): Total heavy rare earth element pattern across the Kuradawe felsic pegmatite zones.
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Samples No. Figure (3.33): Relationship between light rare earth element (LREE) and the heavy rare earth element (HREE) in deferent zones of Kuradawe felsic pegmatite.
The normalized REE pattern are quite variable across the zones of KFP (Figure 3.34). In the border zone of the KFP, the light REE (LREE) is enriched relative to the heavy REE (HREE), and the patterns are relatively smooth. However, in the pegmatitic zones, the overall patterns are subhorizontal with the appearance of a high negative Eu anomaly. Moreover, the REE pattern shows enrichment more than one chondrite except samples YO25 and YO24 are depleted.
The REE abundance of Kuradawe felsic pegmatite shows flat pattern, and with the high negative Eu anomaly [Eu/Eu*)
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Figure (3.34): Chondrite normalized REE plots for Kuradawe felsic pegmatite, Normalization values are those of Sun and McDonough, (1989).
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3.6 Pressure – Temperature condition of Kuradawe felsic pegmatite Though poorly constrained, the pressure attending pegmatite crystallization appear to range from ̴ 300 to 500 MPa for the common and some rare-element pegmatites, and ̴ 300 to 200 MPa for the most evolved rare-element and miarolitic pegmatites, and
̴ 150
MPa for the small, segregation pegmatite formed within subvolcanic bodies of magma (London, 2008). The pressure of Kuradawe felsic pegmatite is estimated based on the Q-Ab-Or ternary diagram after (Rollinson, 1993). The value of 2.5 Kbar, according to the average of samples CIPW-normative compositions. Samples are randomly arranged in this diagram because the samples are collected in different pegmatite zone and also in the different mineralogical zone, this lead to use the average normative as pressure estimate (Figure 3.35). Moreover, the occurrence of andalusite mineral in the Kuradawe felsic pegmatite is the typical evidence of the low pressure (<3 Kbar) in this pegmatite (Figures 3.36 and 3.37). The temperature of pegmatite crystallization more definitively known through applications of mineral equilibria, chemical and isotope exchange, and analyzes of fluid inclusions. The maximum temperature is (772 oC), and the minimum are (534 oC) in the Kuradawe felsic pegmatite, has reported with the uncertainty of ≈ ±25oC. Zircon saturation thermometer indicates that the temperature change and decreasing toward the core zone of
the pegmatite. This drawdown in temperature toward the core clearly observed in the field by increasing the grain size of the mineral toward the core of the body (Figure 3.38).
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Figure (3.35): Phase relationships and minimum melt compositions in the CIPW normative system quartz-albite-orthoclase ±H2O ±anorthite ±F. Experimental minimum melt compositions from (Rollinson, 1993).
Figure (3.36): P-T phase diagram after (Winter, 2001).
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Figure (3.37): P-T field of environments hosting pegmatite populations of the abyssal (AB), muscovite (MS), muscovite – rare-element (MSREL), rare-element (REL) and miarolitic (MI) classes (Modified after Ginsburg et al., 1979 and Černȳ, 1990a. Arrows indicate regional trends of fractionation in the pegmatites relative to metamorphic grades of the host rocks. The MS and MSREL populations, as well as those of the REL and MI pegmatites, tend to be in some cases transitional one to the other (after Černȳ and Ercit, 2005). Aluminosilicate fields and their limits of error from Robie & Hemingway (1984), spodumene– petalite boundary from London (1984), granite liquidus – solidus after Jahns (1982). The 25°C/km and 50°C/km gradients correspond to average Barrovian and Abukuma metamorphic facies series, respectively.
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Figure (3.38): T-Size relation of tourmaline mineral in a different zone from Kuradawe felsic pegmatite.
The temperature of Kuradawe felsic pegmatite determined based on the concentration of zircon in the different samples (Table 3.2). The approach of estimating magmatic temperature through zircon saturation has been proposed by (Watson and Harrison, 1983). Hanchar & Watson, (2003) reviewed the zircon saturation thermometry studies and summarized the main applications of the zircon saturation thermometry to igneous rocks and metamorphic rocks.
From Miller et al, 2003, Waston and Harrison (1983) established the following relationship between zircon solubility, temperature, and major element composition of melt:
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In DZr zircon/melt = {- 3.8 – [0.85(M – 1)]} + 12,900/ T
Where DZr
zircon/melt
Hanchar & Watson (2003)
is the ratio of Zr concentration (ppm) in zircon (~ 476,000 ppm) to
that in the saturated melt; M is a compositional factor that accounts for dependence of zircon solubility on SiO2 and peraluminous of the melt [(Na + K + 2.Ca)/ (Al.Si), all in cation fraction]; and temperature, T, is in kelvins, the temperature convert to oC. Rearranging the equation to yield T-yield a geothermometer for melt:
TZr = 12,900/ [2.95 + 0.85 M + ln (496,000/ Zr melt)]
Miller et al., (2003)
Table (3.4): Temperature and grain size in different Kuradawe felsic pegmatite.
Samples No.
Temperature (oC)
grain size (cm)
YO17 YO14 YO1b YO15 YO4b YO26 YO5b YO25
771 772 727 694 700 534 548 622
0.3 0.5 1 1.4 1.5 9 8 12
YO24
542
30
103
Pegmatite zones Border zone Wall zone Intermediate zone Core zone
CHAPTER FOUR
ANATOMY & CLASSIFICATION
CHAPTER FOUR ANATOMY AND CLASSIFICATION
4.1 Preface Like the taxonomy of living organisms, the classification of pegmatite follows a lineage, seeking the genetic links that relate individual bodies to larger populations through a common process of magmatic evaluation from their source. The extreme range of textural and mineralogical features of pegmatites makes their classification more challenging than for most other rock types. The nomenclature and classification of pegmatites pertain mostly to those of felsic (granitic) composition (London, 2008).
The goals of this chapter is to show how field, geochemical, and mineralogy data can be used for interpretation of different issues including classification and anatomy of pegmatite in Mawat ophiolite complex including (family, class, subclass, type, and subtype) of Kuradawe felsic pegmatite in addition to internal anatomy of Kuradawe felsic pegmatite bodies (border zone, wall zone, intermediate zone, and core zone).
4.2 Pegmatite classification Basically pegmatite has been classified using the same nomenclature as used in the classification of igneous rocks; depend on the mineral present, and chemical composition as follow: A. Acid pegmatite: this type of pegmatite are much more abundant and of much mineralogical interest like (alaskite, normal granite, alkaline granite, granodiorite, quartz monzonite, and quartz diorite) (Landes (1933), Fersman (1940)). This type subdivided into two categories:
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1. Simple pegmatite 2. Complex pegmatite, with following phases (aside from albitization): lithium, fluorine, beryllium, boron, phosphate, graphite, rare earth, Ore mineral, and quartz vein. B. Intermediate pegmatite (syenite, alkaline syenite, monzonite, diorite) 1. Simple pegmatite 2. Complex pegmatite, with following phases: rare alkaline mineral, calcite, radioactive mineral, and sulfide). C. Basic and Ultrabasic pegmatite (gabbro, diabase, anorthosite, and pyroxenite). 1. Simple 2. Complex (calcite-apatite-phlogopite phase).
4.2.1 Simple Pegmatite The Landes (1933) scheme of classifying pegmatites is straightforward. Starting with the object noun “pegmatite”. It attaches adjective modifiers of igneous composition that include all affinities or types. It distinguishes the mineralogically simple pegmatite from those that contain exotic minerals, and selects one mineral or compositional adjective as a diagnostic or at least distinguishing features. These pegmatites are hosted by metamorphic rocks of the amphibolite to granulite facies, or by other plutonic igneous rocks, and, for this reason, they could be included in the abyssal or muscovite classes. They are the pegmatites that Černý (1991) initially placed in the muscovite class in the (Figure 4.1 b), but then extracted into the Muscovite – rare – element class of Černý and Erict (2005) (Figure 4.1 a).
4.2.2 Complex Pegmatite The classification scheme of Černý and Erict (2005) contains three families, five classes, ten subclasses, thirteen types and seven subtypes (Figure 4.1 a). The classes are the same as those used by Ginsburg (1984). Which Černý and Erict (2005) perpetuated with some regret, because of the weak and in some cases misleading connection between the depth of pegmatite emplacement and the metamorphic grade of the host rock. Except for the muscovite class, the subclasses are distinguished by a particular rare – element Association, and then, in the pegmatite types and subtypes, by rare-element mineralogy (London, 2008). 105
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Depend on the geochemical, and mineralogical criteria observed, Kuradawe felsic pegmatite classified under acidic complex type pegmatites.
Figure (4. 1): (a) the pegmatite classification scheme adopted by Černý and Erict (2005). (b) P-T diagram showing the fields of the four pegmatite classes proposed by Ginsburg (1984) and Černý (1991). The pegmatite classes are abyssal (AB), muscovite (MS), rare-element (RE), and miarolitic (MI). Lable reaction-boundaries are (1) kyanite → andalusite, (2) kyanite → sillimanite, (3) andalusite → sillimanite, (4) spodumene + 3 quartz → virgilite, (5) petalite + quartz → β-spodumene, (6) spodumene + 2 quartz → petalite, and (7) sekaninaite (Skn, the Fe analog of cordierite) → almandine + aluminosilicate + quartz. Reaction (1) – (3) from Pattison (1992) as modified be Cesare et al. (2003), reaction (4) – (6) are simplified from London (1984), reaction (7) is from Mukhopadhyay and Holdaway (1994). Red start is the average of the KFP samples.
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4.2.2.1 Pegmatite families Pegmatite classified into the three distinguished families (NYF, LCT and mixed), based on the petrogenetic, developed for pegmatite derived by igneous differentiation from plutonic sources (Černý et al. 2005). An NYF family with the progressive accumulation of niobium, yttrium, and fluorine (besides Be, REE, Sc, Ti, and U). The NYF fractionated from subaluminous to metaluminous A- and I-type granites (Collins et al. 1982) or “within plate” granite (Pearce et al. 1984). A peraluminous LCT family with the progressive accumulation of lithium, Cesium, and Tantalum (besides Rb, Be, Sn, B, P, and F). LCT derived mainly from S-type granite, less common from I-type granites. Most of the pegmatites with the LCT signature have a compositional affinity with S-type granite (Chappell & White 1992, 2001) that originate from metasedimentary rocks rich in muscovite (London, 1995). The peraluminous nature of S-type granite is expressed by an assemblage of muscovite, garnet, cordierite, sillimanite or andalusite, tourmaline, and gahnite (Černý et al. 2012). The Kuradawe felsic pegmatite is of the LCT family because they are S-type originated source (see figures 3.17 and 3.18), and strongly peraluminous (Figures 4.2 and 3.14). Also assemblage and include muscovite, cordierite, andalusite, and black tourmaline. Mixed family (NYF+LCT family) consists of pegmatites that display mixed geochemical and mineralogical characteristics. These characters can manifest as LCT accessory minerals and LCT trace-elements mixed within differentiated NYF pegmatites or LCT pegmatites formed during late stages of evolution of NYF pegmatite populations.
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Figure (4. 2): A/NK = Al2O3/ (Na2O + K2O) versus A/CNK = Al2O3 / (CaO + Na2O + K2O) diagram after Maniar & Piccoli, (1989).
The classification scheme for LCT and NYF granite families as defined by Černý and Ercit (2005) help to discriminate different sources for granitic pegmatites.
LCT family include:
1. LCT I-type: subaluminous (A/CNK=1) fertile granites of igneous protoliths, such as those generated by low-percentage anatexis of meta-igneous rocks of the basement (Wright and Haxel 1982). These granite will origin pegmatite is poor in Cs, B, P, and S.
2. LCT S-type: peraluminous (A/CNK>1) fertile granites of metasedimentary and metavolcanic protoliths (Černý and Brisbin, 1982a). These granite will origin pegmatite enriched in Cs, B, P, S. Peraluminous fertile granites display fractionation levels equal to those of evolved rare-element pegmatite liquid melts. However, many fertile granites are proven to have derived from melting of the
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mixed basement and supra crustal protoliths, and they show intermediate geochemical compositions (Walker et al. 1986).
NYF family include:
1. NYF A-type: anorogenic granites belong to bimodal gabbro-granite suites. And generated by partial melting of depleted lower crust generate sub alkaline (A/NK =1) to metaluminous (A/CNK<1) NYF pegmatites (Simmons et al., 1987). These granites will generate topaz and fluorite-bearing pegmatites.
2. NYF I-type: syn to late-orogenic granites produced by large anatexis of I-type tonalitic protoliths and subsequent moderate differentiation. This granite will make topaz-bearing pegmatites (Buck et al., 1999; Kjellman et al., 1999). Petrological, isotopic and geochemical evidence suggest several possible modes of origin of the NYF-granite magmas. The sources could be from differentiation of mantle-derived basaltic magmas (Fowler and Doig, 1983): Melting of middle or lower crust depleted by a previous melting causing LCT granites to mobilized but NYF granites to be conserved (Collins et al., 1982; Whalen et al., 1987; Černý, 1990, 1991a); melting of continental crust enriched in NYF elements by mantle-derived fluids following the model of bimodal gabbro–granite suites (Harris and Marriner 1980, Jackson et al., 1984; Martin and De Vito 2004).
(Wise, 2013) Used the mineral chemistry to discriminating between pegmatites of LCT and NYF affiliation. The proposed discrimination scheme is applied only to pegmatites of the rare-element and miarolitic classes and based on the major, and trace element chemistry of K-feldspar, biotite, topaz, and beryl. Reasonably good discrimination between LCT and NYF affiliated pegmatites can be obtained using the Ga concentrations of Kfeldspar. Gallium contents in K-feldspars from NYF pegmatites commonly fall between 20 and 100 ppm. By comparison, K-feldspar from LCT pegmatites, typically contain Ga contents between 10 and 40 ppm with only the most evolved pegmatites having as much as 100 ppm. The Ga contents of K-feldspar dominate zone from KFP is consistent with the Ga values of LCT type Pegmatite (Table 3.2, sample No. YO 25).
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Plotted in the ternary diagram Al2O3-MgO-total FeO, biotite from NYF pegmatites appear to separate into two distinct groups from the LCT pegmatites. Biotite from the NYF groups have identified as those that related to A-type granites (designated here as NYF-A) and a second group apparently affiliated with I-type granites (NYF-I). Although biotite from both NYF and LCT pegmatites may have similar Fe concentrations, biotite from LCT pegmatites has higher Al contents than the NYF-I and NYF-A group, respectively. Mineral chemistry of biotite from Kuradawe felsic Pegmatite plots in the field of LCT family according to this scheme (Figure 4.3).
Figure (4. 3): Discrimination diagrams for LCT and NYF-family granitic pegmatites. Al2O3MgO-FeO ternary diagram for biotite, after (Wise, 2013).
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4.2.2.2 Pegmatite classes and types Five “formation” or classes of pegmatites are classified and recognized, this classification scheme generated by Ginsburg (1984). These are abyssal, muscovite, muscovite–rare-element, rare-element, and miarolitic classes, based on mineralogical or textural features that they are related to the depth of emplacement. Most of which classes subdivided into subclass depend on the different geochemical characteristics. In addition most of the subclass are divided into type and subtype according to the different geochemical signatures or P-T condition of solidification, expressed in variable assemblages of accessory minerals (Černý et al. 2005). This classification improved by Černý and Ercit (2005) with correlating the pegmatite classes with other petrogenetic data, for example the stability fields of the aluminosilicate polymorphs and the lithium aluminosilicates, this scheme is widely used today (Figure 4.1).
Kuradawe felsic pegmatite belongs to a REE class and REL-REE subclass because they characterized by the assemblage of high field strength element. The LREE element is more than the HREE. They contain some minerals like monazite, zircon, rutile, ilmenite. Depend on this reasons the Kuradawe felsic pegmatite is the Allanite-monazite type according to the Černý and Ercit (2005) Classification (Table 4.2).
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Table (4. 1): Principal subdivision and characteristics of the five class of granitic pegmatite, after Černý and Ercit (2005) Class
Typical miner element
Subclass
Metamorphic environment
Relation to granite
Abyssal (AB) HREE
HREE,Y,Nb,Zr,U,Ti
(upper amphibolite)
None (?)
LREE
LREE, U, Th, Ti
low-T to high-P granulite
(segregations of
U
U, Th, Zr, LREE
facies ̴ 4 to 9 Kbar,
anatectic
Bbe
B, Be
o
̴ 700-800 C
leucosome?)
Muscovite (MS) No rare-element Mineralization (Micas and ceramic minerals).
High-P, barrovian Amphibolite fancies (Kyanite-sillimanite)
None Anatectic bodies) tomarginal and
5 to 8 Kbar, 650 to 580 o C
exterior
Muscovite – Rare-element (MSREL) MSREL-REE
Be, Y, REE, Ti, U, Th, Na-Ta
MSREL-Li
Li, Be, Nb
Moderate to high P, (T)
Interior to exterior:
amphibolite facies:
locally poorly defined o
3 to 7 kbar, 650 to 520 C
Rare-element (REL) REL-REE
Be, Y, REE, Ti, U, Th, Na>Ta
variable, largely shalow and postdating regional events affecting the host rocks
interior to marginal (rarely exterior)
REL-Li
Li, Rb, Cs, Be, Ga, Sn, Hf, Nb, Ta, B, P, F
low-P, Abukuma amphibolite (andalusite-sillimanite) to upper greenschist facies:
interior to marginalt to exterior
̴2 to 4 kbar, ̴650 to 450 oC
Miarolitic (MI) REE
Y, REE, Ti, U, Th, Zr, Nb, F
Li
Li, Be, B, F, Ta>Nb
very low P, postdating regional events that affect the host rocks low-P amphibolite to greenschist
interior to marginal (interior to) marginal
facies, 3 to 1.5 kbar, 500 to 400 oC to exterior
112
REL - Li
REL-REE
Subclass
113
albite
albite- spodumene
Complex
beryl
gadolinite
euxenite
allanite-monozite
Type
amblygonite
elbaite
lepidolite
petalite
spodumene
beryl-columbite beryl-columbite- phosphare
Subtype
Ta-Nb, Be, (Li, Sn, B)
columbite-tantalite, beryl, cassiterite
spodumene, beryl, columbite-tantalite, (amblygonite, lepidolite, pollucite) petalite, beryl, columbite-tantalite, as above (amblygonite, lepidolite, pollucite) lepidolite, beryl, topaz, microlite, Li, F, Rb, Cs, Be, Ta-Nb, columbite-tantalite, (pollucite) (Sn, P, B) tourmaline, hambergite, danburite, Li, B, Rb, Sn, F, (Ta, Be, Cs) datolite, microlite, (polylithionite) amblygonite, beryl, columbite-tantalite Li, Rb, Cs, Ta-Nb, Be, (Sn) (lepidolite, pollucite) spodumene, (cassiterite, beryl, columbite-tantalite) Li, (Sn, Be, Ta-Nb, B)
beryl, columbite, tantalite, triplite, triphylite
beryl, columbite, tantalite, (rutile)
Be, Nb-Ta, (Sn, B) Be, Nb-Ta, P, (Li, F, Sn, B) Li, Rb, Cs, Be, Ta-Nb, (Sn, P, F, B)
euxenite, monozite, xenotime, zircon, rutile, ilmenite, (fergusonite, aeschynite, zinnwaldite) gadolinite, fergusonite, samarkite, zircon, rutile, ilmenite, fluorite, (zinnwaldite)
allanite, monozite, zircon, rutile, fluorite, illmenita
Typical minerals
LREE, U.Th, (Be, Nb>Ta, F,[p]) L-H-REE, Y, Ti, Zr, Nb>Ta, (F,P) Be, Y, HREE, Zr, Ti, Nb>Ta, F, (P)
Geochemical signature
Table (4. 2): Subdivision of felsic pegmatites of the rare-element class, after Černý and Ercit, (2005).
Kuradawe felsic pegmatite Classification are: Pegmatite Family : LCT family Pegmatite Class : Rare-Element class REL-REE subclass Subclass : allanite-monozite type Type :
Kuradawe felsic pegmatite (KFP)
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4.3 Internal anatomy of Kuradawe felsic pegmatite Many authors created the scheme for representing the internal texture and zonal distribution of minerals in the pegmatites. Most authors recognize the same textural or zonal features. The terminology suggested by Cameron et al. (1949) is the largely used today. Zoning or the lack is the basis point for starting internal anatomy. The distribution of grain size and mineralogy is homogeneous in unzoned pegmatites though they may possess a porphyritic texture and oriented direction of crystal growth (Kesler 1961, Swanson 2012). Unzoned pegmatite tends to occur in association with host rocks of the high metamorphic grade in the stability field of kyanite and spodumene (Horton et al. 1987). Zoning is the distinctive point of pegmatites detaches from other plutonic igneous rocks. It is manifested by variations in the spatial distribution of grain size, mineral assemblage, crystal habit, or rock fabric (Figure 4.4) (Vlasov, 1961). Kuradawe felsic pegmatite is zonal pegmatite. The have different mineralogical and textural in different zone. KFP are complete pegmatite because all zones formed (border zone, wall zone, intermediate zone, and core zone).
Figure (4. 4): Typical zoning sequence pegmatite modified from Vlasov (1961). From the granitic source.
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4.3.1 Border zone The border zone in the Kuradawe felsic pegmatite is a thin selvage (5 to 10 cm), that surrounds the pegmatite dikes in contact with its host rocks (Figures 4-5 and 4.6). The transition from border to wall zone is sharp, commonly occurring over a distance on the border of centimeters, and it is marked by an abrupt increase in grain size. The grain size is fine-grained (2-5 mm), and the texture is hypidiomorphic granular or bimodal if the fine-grained portion constitutes a groundmass to larger crystals of tourmaline and muscovite. The border zone of KFP consists of varying proportions of quartz, muscovite, and albite. Several accessory minerals are also present, including tourmaline, apatite, monazite, cordierite, rutile, and columbite, in the border zone muscovite and tourmaline are commonly the coarsest mineral in this zone. The abundance of black tourmaline at pegmatite borders is best explained by the infiltration of Fe and Mg into the pegmatite from the host rocks.
4.3.2 Wall zone The wall zone of Kuradawe felsic pegmatite appears as a thicker (80cm to 1 m) (Figures 4.5 and 4.6), courser-grained (1-3 cm) variant of the border zone. The wall zone of KFP characteristically contain the assemblage of albite, and quartz. Albite is most abundant and is typically intergrown with quartz. Some accessory mineral present in the wall zone like tourmaline, and columbite. In this zone tourmaline, is prismatic and very course grain. A notable trend in the major modal mineralogy of the wall zone is a decrease in the abundance of albite and an increasing in the abundance of quartz from the outer part of the wall zone toward the interior. Depend upon the position of the dikes the wall zone contacts with the intermediate zones are gradational.
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4.3.3 Intermediate zone The intermediate zone of Kuradawe felsic pegmatite appears as a thicker (1 to 2 m) (Figures 4.5 and 4.6), very courser-grained (6-12 cm). The intermediate zone of KFP divided into three subzones.
The First Intermediate subzone is distinguished by the presence of coarse-grained to very coarse-grained of potassium feldspar crystals (orthoclase). That set in a matrix consisting mainly of massive quartz and smaller amounts of albite. Muscovite and tourmaline also presence in this zone by a small quantity, this zone contacts the wall zone, the grain size of potassium feldspar decrease toward contact with other zones. Perthite was reported to compose 90% of the rock (Hanley, 1953).
The second intermediate subzone distinguished by the abundance of albite crystals. This subzone is characterized coarse to very coarse-grained of albite that set in the matrix of quartz in large amount muscovite and tourmaline in small quantity, this located between first intermediate subzone and third intermediate subzone. This subzone is the larger subzone of intermediate subzone in the KFP.
The third intermediate subzone is composed mainly of medium-grained to very coarsegrained of microcline intergrown with quartz, the general texture of this subzone is similar to the texture of first or second intermediate subzone. This subzone is more continuous than first and second intermediate subzone and almost entirely surrounds the core zone.
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4.3.4 Core zone The core zone is the innermost unit of Kuradawe felsic pegmatite dikes, whether a single mass of multiple repetition of the same mineralogy at the same structural or sequential position, regarded as the core zone. The proportions of core material to the other zones can be exceedingly variable. Monomineralic quartz cores predominant in the KFP. The core zone in the KFP appears as a thicker (nearly 2 m) (Figures 4.5 and 4.6). This zone consist of small grains of quartz with disseminated tourmaline crystals formed up to (30 to 45 cm in length).
There are at least four possibilities to explain the origin of a quartz core: 1- It forms simultaneously with the other major magmatic assemblages (Jahns, 1982). 2- It forms by deposition from a hydrothermal fluid (Burnham and Nekvasil, 1986). 3- Quartz bodies crystallize sequentially after the main feldspathic units, but they do not represent the last magmatic assemblage from pegmatite crystallization (Morgan and London, 2005). 4- Pure quartz bodies originated from an essentially pure-silica fluid whose origins cannot yet explain (London, 2008).
The Modal quartz content of the intermediate zone is similar to the bulk mode for granitic composition (Chapter two Figure 2.22) suggest the quartz mass in the core crystallize sequentially after the main feldspathic units.
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Figure (4. 5): Model for Kuradawe felsic pegmatites zones. The KFP consist of four zones, border zone, wall zone, intermediate zone, and core zone respectively from margin to center of pegmatite.
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Figure (4. 6): 3D Block diagram of a zoned Kuradawe felsic pegmatite, showing the concentric nature of zoning in steeply dipping. Lateral and vertical scales are in meters.
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4.4 Kuradawe felsic pegmatite zones evaluation Field, mineralogy, and geochemical data all approved that the KFP show clear zoning pattern (Figure 4.5), the main concern arise why those zonings exist? In order to interpret this pattern of zoning we proposed two possible scenario for this zoning:
Scenario No. 1
They could reflect slow cooling (wall zone, intermediate zone, core zone) after intrusion into the cold country rock. In this case, the KFP should exhibit chilled margin, a chilled margin (border zone) is a possible evidence for rapid cooling. The increase tourmaline and alteration muscovite to lepidolite in addition to the dominance of high-temperature minerals like cordierite and andalusite is against this proposed Scenario.
Scenario No. 2
They could reflect slow cooling in hot country rock, in this case, they should be significant interaction between the KFP and country rock. The increase tourmaline and alteration biotite to lepidolite in addition to the dominance of high-temperature minerals like cordierite and andalusite is possible evidence for this interaction especially in the border zone.
In the calculation zircon saturation thermometers maximum temperature recorded (772 o
C) in the border zone which due to huge crystallization of zircon in this zone. The
recorded temperature is beyond the granite melting limit (Chapter three figure 3.37, 3.38). The only possibility solution to this problem is that the granite underwent contact metamorphism along the border and producing a zone of cordierite-andalusite around the entire KFP body.
After a zone of thermal resistance have been formed along the border between ultramafic and KFP. Normal continuous crystallization sequence started from Ca-rich albite in wall zone (Ab92 – An8
) to pure Albite (Ab98 – An2)toward the core. In
pegmatites, branching crystals, flaring crystal, graphic crystals, and terminated crystals all 120
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show a consistent direction of growth toward the core of residual melt (London, 2008). A clear discontinuous Bowen reaction series observed through different zones from plagioclase to orthoclase and finally quartz (Figure 4.7).
Figure (4. 7): Model for temperature evaluation of Kuradawe felsic pegmatite.
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CHAPTER FIVE PETROGENESIS
5.1 Petrogenesis The rare-element class of Kuradawe felsic pegmatite display extreme fractionation and accumulation of LILE (large ion lithophile elements) like K, Rb, Sr, Cs, Ba; HFSE (high field strength elements) like Zr, Hf, Nb, Ta, REE, U, Th. All these elements are beyond the limits observed in other granitic rocks. According to the mineralogy and geochemistry feature, the Kuradawe felsic pegmatite displays the characteristic of S-type and peraluminous granites. Divers schematic different scenarios to explain how pegmatite differentiate may taken into consideration: (1) An evolving magma chamber where different generations of pegmatite dikes that cross-cut each other on the surface and evolve with different geochemical signatures (London et al., 1988). (2) Fractionation and geochemical evolution of the distance in pegmatite fields starting from its source, granitic in origin (Trueman and Černý, 1982) (3) Escape of pegmatite liquids through a filter pressing mechanisms from a rare-metal granitic magma chamber of zoned pluton (London, 2008).
5.1.1 Major element indicator
The Kuradawe felsic pegmatite occupies the field of peraluminous (Figure 3.14, and Figure 4.2) and the KFP is S-type granite (Figure 3.18). In the Harker variation plots (Figure 5.1), Kuradawe felsic pegmatite samples exhibit a nearly linear-like trend for the most major element. Al2O3, CaO, K2O, and MgO. It shows a negative correlation with silica. These chemical variation indicate the importance of
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fractional crystallization in the magmatic evolution of KFP. The fractionation phase is mainly plagioclase, biotite, and K-feldspar.
Figure (5.1): Harker variation diagram for most major oxide in the Kuradawe felsic pegmatite.
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5.1.2 Trace element indicator The trace-element contents of granitic melts change substantially as crystallization proceeds. Whether trace elements are concentrated in the dwindling fraction of melt or dispersed in the major and minor crystallizing minerals depends mostly on the compatibility of those trace elements in specific minerals versus melt, as functions of changing temperature. Trace element ratios as indicators of magmatic fractionation and the chemical evolution of the melt (London, 2008).
Kuradawe felsic pegmatite intruded with in serpentinized harzburgite and serpentinized dunite host rocks of the Mawat ophiolite complex and above the Daraban Leucogranite. The Daraban Leucogranite data are extracted from Mohammad et al., (2014).
5.1.2.1 Strontium versus the Rb/Sr ratio
Trace element (Rb, Sr) plot on the partial melting of metapelite model after Inger and Harris (1993). The linear trends observed suggesting that intra-suite variation is largely a result of various degree of fractional crystallization of alkali feldspar and plagioclase from a melt source corresponding to the average composition of the underlying metapelite, (Figure 5.2) demonstrates that the Kuradawe felsic pegmatite samples form a generally linear trend, in the Rb/Sr versus Sr plot, fractionation vectors are shown for fractional crystallization from the Daraban leucogranite.
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Figure (5.2): Strontium and Rb/Sr variation diagram for the Kuradawe felsic pegmatite. F =melt fraction; Ms (VA) =vapor absent muscovite melting; Ms (VP) vapor present muscovite melting; Bt (VA) =vapor absent biotite melting. After Inger & Harris, (1993).
5.1.2.2 Rubidium versus the K/Rb ratio The geochemical behavior of Rb is very closely related to that of K. The distinctly larger radius of Rb is mainly responsible for their mutual fractionation in igneous processes, in magma crystallizing hornblende or feldspar. The resulting igneous rocks show increasing K/Rb because K preferred to Rb in the feldspar and hornblende (Hart & Aldrich 1967, Murthy & Griffin 1970). However, this trend becomes reversed with significant biotite or K-feldspar precipitation. These two phases invariably show K/Rb rapidly decreasing decrease in products of late magmatic and postmagmatic crystallization (Show, 1968). The Rb concentration and the K/Rb ratio of the Kuradawe felsic pegmatite is controlled mainly by K-feldspar. On the diagram K/Rb vs Rb (Figure 5.3) the Kuradawe felsic pegmatite plot along a fractionation pathway that differs from the classical trends characteristic of granites, producing lithophile rare-element deposits (Černý, 1991).
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Figure (5.3): The evolution paths of KFP plotted in K/Rb vs. Rb after (Černý, 1991).
5.1.2.3 Cesium versus the K/Cs and K/Rb ratios Among the major elements, K is the only ion for which Cs can substitute. The lower electronegativity and ionization potential of Cs+ relative to those of K+ impart a more ionic character to Cs-O bonds (Černy et al. 1985). However, the behavior of Cs+ in igneous and postmagmatic events is governed by its large radius (1.67 Ao) relative to that of K+ (1.33 Ao). Thus Cs+ is admitted into potassic minerals only reluctantly, much more selectively than Rb+, and the dispersion of Cs contents in rock-forming minerals is consequently much greater than that of Rb (Ahrens 1966; Černy et al. 1985). The Cs concentration in coexisting phases decreases in the sequence biotite–muscovite–K-feldspar (Volfinger 1969, de Albuquerque 1975, Neiva 1975, 1977).
In the KFP process of Cs accumulation into residual systems continues not only from the granitic melt into rare-element pegmatites in general, but it is very strongly expressed even within zoned groups and fields of the pegmatites themselves. In addition they are 126
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decreasing toward the core of pegmatite, Cs formed from the fractional crystallization of K-feldspar in the KFP (Figure 5.4 A) (Černý et al. 1981). Cs is preferred to use K/Rb versus Cs to track the chemical evolution of pegmatite through their K-feldspar phases, three important conclusion emerge from the trend in Figure (5.4 B). First, the variations are linear if plotted on a logarithmic scale, which is consistent with fractional crystallization as the only process involved in the chemical trend. Second, the trend that are indeed continuous if all data presented attest to the continuity of the process from granite to common pegmatite to rare-element pegmatite. Thirdly, a single feldspar may record the history of crystallization that manifested throughout an entire pegmatite.
A
B
Figure (5.4): (A) The K/Cs versus Cs (B) The K/Rb versus Cs, trends from Daraban leucogranite to Kuradawe felsic pegmatite (after Černȳ et al., 1985).
5.1.2.4 Hafnium versus the Zr/Hf ratios These two elements considered together because of their chemical similarity, which arises from their high field strength elements. Zirconium and hafnium adopt a 4+ charge, zirconium separated from hafnium by the lanthanides. As a result, hafnium is substantially heavier ion than Zr, but otherwise the ionic radius and electronegativity are similar (London, 2008).
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In the peraluminous granites, the Zr/Hf ratio of melt is affected by the composition of zircon, because no other phases in these granites and their pegmatites accommodate either element to a notable degree (Černý et al. 1985). Kuradawe felsic pegmatite variation is compared with the Daraban leucogranite. The trend of Zr/Hf versus Hf in the Kuradawe felsic pegmatite are linear with identical slopes (Figure 5.5). The inverse variation in Zr and Hf arises from the fact that there is only one important host phase for each element, and their abundances in that phase must vary inversely. The fractionation trend from Kuradawe felsic pegmatite evolve from a predominance of the element of higher abundance and lower atomic weight (Zr) to those of lower abundance and higher atomic weight (Hf). Linnen and Cuney (2005) explained the fractionation trend of Zr/Hf in zircon-hafnium on the basis of differential solubility of their respective end-member phase in metaluminous to peraluminous granitic melt. Zircon has lower solubility than hafnium, the mineral component with lower solubility should be first precipitate from the melt.
Figure (5.5): Hafnium versus Zr/Hf ratio and fractionation trend from Daraban leucogranite to Kuradawe felsic pegmatite (after Linnen and Cuney, 2005).
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5.1.2.5 Zirconium versus Yttrium and Zr/Y ratio Kuradawe felsic pegmatite variation is compared with the Daraban leucogranite, relative to fractionation indices of zircon. The average trends used as a comparison for chemical change due to fractionation, the linear trend indicative of fractionation from granitic parents. In the diagrams, (Figures 5.6 A and B) KFP divided into two groups with variable Zr/Y ratio and Y. The lower group below the Draban leucogranite due to the fractionation of zircon toward the core of KFP, another group due to fractionation of Kfeldspar.
B
A
Figure (5.6): (A) Binary diagram between Zr and Y for Kuradawe felsic pegmatite (KFP) and Daraban leucogranite (DG). (B) Binary diagram between Zr and Zr/Y ratio for KFP and DG. And shown the modeled fractional crystallization trends for granitic melt. Fractional mineral vectors for acidic composition illustrated for Y - Zr and Y - Zr/Y ratio relationships (distribution coefficients from a compilation by Rollinson, (1993).
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5.1.3 Rare element indicator A fractionation process including REE-rich accessory phases such as apatite, zircon, and monazite is less expressed in the REE patterns, although these accessory minerals are mostly present in the Kuradawe felsic pegmatite. However, in (La/Lu)N versus LaN (Figure 5.7), the variation of REE contents seems to be consistent with the fractionation of monazite during the evolution of KFP.
Figure (5.7): (La/Lu)N versus LaN diagrams showing the variation of REE contents of KFP by the fractionation of accessory minerals, particularly monazite. The arrows indicate the effect of fractional crystallization of allanite (Aln), apatite (Ap), monazite (Mnz), titanite (Ttn) and zircon (Zrn) on the composition of residual liquids and point towards the melt direction governed by each of these minerals (distribution coefficients from compilation by Rollinson, (1993).
The REE abundances are quite variable across the spectrum of rocks examined. In the most primitive fine-grained members of the sequence Daraban leucogranite (DLG), the light REE (LREE) are enriched relative to the heavy REE (HREE), and the patterns are relatively smooth (Figure 5.8). However, in the pegmatitic facies, the overall patterns are subhorizontal, with a relative decrease in the LREE and an enrichment in HREE and the 130
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appearance of a negative Eu anomaly (Černý et al., 2012) (Figure 5.8). This trend expressed in the Daraban leucogranites continued in the Kuradawe felsic pegmatites. All of the above features of REE concentrations and changes during extremely fractionation are strictly comparable to data obtained in similarly differentiated suites elsewhere (Vidal et al. 1982, Searle & Fryer 1986, Yan et al. 1988, Breaks & Moore 1992, Raimbault 1998, Sweetapple & Collins 2002). This trend has never interpreted in its entirety in terms of progressive consumption of different REE by various crystallizing minerals, but it repeatedly confirmed in well-exposed and thoroughly examined differentiated suites of fertile peraluminous leucogranites (Černý & Brisbin 1981, Černý and Meintzer 1988). In our case, the precipitation of monazite in early members of the Daraban leucogranite sequence could be responsible for the low levels of the REE in the early Kuradawe felsic pegmatite, massive crystallization of plagioclase is indicated by negative Eu anomalies, which are eliminated in later generations of pegmatite by overall depletion of REE. Finally, the geochemical signatures (major, trace, and rare earth elements) of the KFP are all the more interesting because they represent the extremes of fractionation trends encountered in the final stages of granitic differentiation. Indeed, fractional crystallization from the parental granitic melt appears to be principal means by which pegmatite liquid melts acquire their trace-element signature once move away. Fractional crystallization is a mechanism commonly proposed to explain the wide compositional variations observed in some pegmatitic bodies or some pegmatitic fields, accordingly different degree of fractional crystallization of parent granitic melt accounts for different pegmatitic facies with an increasing degree of differentiation as fractionation proceeds (London 2008, Roda-Robles et al. 2012). Geochemical data of KFP indicate that the KFP derived from the fractional crystallization of granitic melt in the Daraban Leucogranite.
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Figure (5.8): Chondrite normalized REE patterns for the Kuradawe felsic pegmatite, which extend the trend of the Daraban leucogranite as visible in shaded field cover (after Sun and McDonough, 1989).
5.2 Tectonic setting The geochemical data of Kuradawe felsic pegmatite was using to indicate the tectonic setting and has been extensively suggested in the literature (e.g., Pitcher, 1987; Pearce et al., 1984; Bachelor and Bowden, 1985; Maniar and Piccoli, 1989; Barbarin, 1990, 1999; Pearce, 1996; Foerster et al., 1997). The Kuradawe felsic pegmatite considered as a collision felsic rock. The geochemical data of KFP scattered because collected in different pegmatite zones. Hence, it is likely to use the average for all samples to explain the tectonic environment of KFP. On the Trace element discrimination diagrams (Y-Nb, and Yb-Ta) of Pearce et al. (1984), the KFP samples plot either volcanic arc granites (VAG) + syn-collisional granites (syn-COLG) and within plate granites (WPG) but the average data fall in the VAG + Syn-COLG field (Figure 5.9 A). In the Ta versus Yb discrimination diagram that separates the syn-collisional and the volcanic arc granites, the average of KFP data located in the syn-COLG field (Figure 5.9 B). Moreover, in the multicationic 132
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parameters R1–R2 diagram after de la Roche et al. (1980) with the geotectonic discrimination of Bachelor and Bowden (1985) (Figure 5.10), Martin and De voit (2005) consider LCT pegmatites to be members of orogenic (calc-alkaline suites) formed in a subduction setting. In contrast, NYF pegmatites, are affiliated with anorogenic suites, formed in an extensional setting, suggest that the Kuradawe felsic pegmatite are located mostly as syn-collision and late- orogenic granites, and as related to post-collision uplift.
A
B
Figure (5.9): (A) Y-Nb discriminate diagram and (B) Yb-Ta discriminant diagram, for Kuradawe felsic pegmatite after Pearce et al. (1984). (VAG) Volcanic arc granites, (synCOLG) syn-collision granites, (WPG) within plate granites, and (ORG) Ocean Ridge Granites.
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Figure (5.10): R1 = 4Si–11(Na + K)–2(Fe + Ti) versus R2 = 6 Ca + 2Mg + Al diagram for Kuradawe felsic pegmatite, after de la Roche et al. (1980) displaying the geotectonic fields (Bachelor and Bowden, 1995).
The tectonic setting of KFP also can be indicated by the multi-element spider diagram and compared to the oceanic ridge granite (ORG) multi-element spider (Pearce et al. 1984). The multi-element spider diagram shows the concentration of K2O, Rb, Ba, Th, Ta, Nb, Ce, Hf, Zr, Sm, Y, and Yb normalization. The spider diagram of KFP is connect to the spider diagram of Syn-COLG, in which they are enrichment in K2O, Rb, Ba, Th, Ta, and Nb and depleted in Ce, Hf, Zr, Sm, Y, and Yb (Figure 5.11). The spider diagram of KFP is displayed positive anomalies in Rb, Th, and Nb and negative anomalies in Ba. The negative anomaly of Ba due to the extreme fractionation of K-feldspar and tourmaline.
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Figure (5.11): The comparison of Ocean Ridge Granites (ORG) normalized multi-element spider diagram of the Kuradawe felsic pegmatite with typical syn-collision granites (SynCOLG) and post-collision granites (Post-COLG) after Pearce et al. (1984).
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CHAPTER SIX CONCLUSIONS AND RECOMMENDATIONS
6.1 Conclusions
Based on field and petrographical, mineralogical and geochemical data, the following conclusions can be drawn:
1- Kuradawe felsic pegmatite (KFP) has a vertical symmetrical zoning from tourmaline leucogranite at the bottom to highly evolved pegmatite facies with various degree of enrichment and depletion of major, trace, and rare earth element. The entire granitic system hosted in harzburgite - dunite suite of Mawat ophiolite complex.
2- The petrographic study shows that the Kuradawe felsic pegmatite composed of essential minerals: quartz, plagioclase (albite), orthoclase + microcline, muscovite, and tourmaline. Accessory minerals are biotite, zircon, monazite, apatite, andalusite, rutile, cordierite, and columbite.
3- Based on the Petrographical, SEQXRD study, and CIPW norms of Kuradawe felsic pegmatite five mineralogical zones has identified from border to core are (quartz–albite–muscovite (Q-A-M); quartz–albite (Q-A) zone; quartz-perthitemuscovite (Q-P-M) zone; quartz-microcline (Q-MI) zone; and quartz (Q) zone).
4- The border zone of the Kuradawe felsic pegmatite affected by synchronous contact metamorphism, evidenced by typical high-temperature metamorphic minerals (cordierite and andalusite).
5- The petrographical studies reveal that rock have been affected by dynamic metamorphism evidenced by (Kink structure, deformation twinning, and mica fish).
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6- Field observation shows that the grain size is increasing toward the center of the body from the millimetric scale at border zone to centimeters scale at the core zone, the largest tourmaline crystal have been recorded (30 cm width – 40 cm length).
7- Major element data of Kuradawe felsic pegmatite display increasing of SiO2 %, but decreasing Al2O3 %, MgO %, and CaO % from border to core zone. Also, K2O % is decreasing but show a positive anomaly in the intermediate zone due to the orthoclase and microcline mineral in this zone. The Na2O % enriched in the wall zone and intermediate zone due to the albite mineral and decreasing toward border and core zone.
8- Depend on geochemical data Kuradawe felsic pegmatite are classified as peraluminous, calc-alkaline felsic pegmatite, and S-type origin.
9- The geochemical features of the Kuradawe felsic pegmatite indicate that the different members of this late igneous assemblage belong to a single magmatic sequence representing different stages of differentiation of a granitic magmatic parent. The Daraban leucogranite + Kuradawe felsic pegmatite suite represents an upward fingering-out system rooted in a deeper-seated evolving magmatic source, which probably derived by anatexis of metasedimentary rocks.
10- Anatomical study of Kuradawe felsic pegmatite shows that KFP are the complete body in the view of various zones of pegmatite. The recorded zones are; border zone of (5-10 cm); wall zone (80 cm- 1 m); intermediate zone (1-2 m); and core zone (nearly 2 m). 11- Zircon saturation thermometry suggests that the crystallization sequences of Kuradawe felsic pegmatite started and changed from the border (772 oC) toward the core of the body (534 oC). The estimated pressure of about 2-4Kbar, suggesting shallow level depth.
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12- Kuradawe felsic pegmatite belongs to LCT family, rare-element class, REL-REE subclass and allanite-monazite type.
13- The trace element signature of Daraban leucogranite and the LCT Kuradawe felsic pegmatite derived from them, are imparted mainly by participated of muscovite and feldspar in the melt forming reaction.
14- In addition to LCT nature, the Trace and REE data of Kuradawe felsic pegmatite indicate syn-collisional to late-orogenic tectonic setting.
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6.2 Recommendations
1- Boron isotope study of tourmaline to indicate the sources rocks. 2- Zircon and Monazite geochronology to prove the emplacement time. 3- Metamorphic phase equilibrium studies for border zone. 4- Thermal modeling of pegmatite and host rocks to show the cooling rate. 5- Sr-Nd isotope to indicate more about the sources rocks. 6- Analysis of fluid inclusions in tourmaline, and quartz to indicate the temperature and pressure.
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151
APPENDIX
.
Appendix I XRD diffractograms for Kuradawe felsic pegmatite samples: 1- Sample : YO17
APPENDIX
.
Appendix I 2- Sample : YO14
APPENDIX
.
Appendix I 3- Sample : YO1b
APPENDIX
.
Appendix I 4- Sample : YO12b
APPENDIX
.
Appendix I 5- Sample : YO28
APPENDIX
.
Appendix I 6- Sample : YO5b
APPENDIX
.
Appendix I 7- Sample : YO25
APPENDIX
.
Appendix I 8- Sample : YO31
APPENDIX
.
Appendix I 9- Sample : YO24
APPENDIX
.
Appendix II Table (2.5): Electron probe microanalysis data of plagioclase minerals. Border zone Oxide wt % 1
1
2
3
Wall zone 4 5
6
7
8
SiO2
66.54
68.43
65.53
67.41
68.45
68.77
68.82
67.86
69.13
TiO2
0
0
0
0
-0.01
0
0
0
0
Al 2O3
20.57
18.94
18.51
21.19
20.21
19.1
20.19
19.04
19.2
Cr2O3
0
0
0
0.03
0.01
0
0
0
0
FeO
0
0
0
0.03
0
0
0.07
0
0
CaO
1.48
0.45
0.16
0.81
0.45
0.59
0.47
0
0
Na 2O
11.22
12.16
15.67
10.73
11.23
11.39
11.26
13.1
11.67
K2O
0.18
0.02
0.13
0.67
0.09
0.15
0.1
0
0
Total
99.99
100
100
100.87
100.43
100
100.91
100
100
cation propotions based on 8 oxygen cations
apfu
apfu
apfu
apfu
apfu
apfu
apfu
apfu
apfu
Si
2.909
2.979
2.775
2.932
2.986
3.011
2.989
2.933
3.022
Ti
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Al
1.060
0.972
0.924
1.086
1.039
0.986
1.033
0.970
0.989
Cr Fe +2
0.000
0.000
0.000
0.001
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.001
0.000
0.000
0.003
0.000
0.000
Ca
0.069
0.021
0.007
0.038
0.021
0.028
0.022
0.000
0.000
Na
0.951
1.027
1.287
0.905
0.950
0.967
0.948
1.098
0.989
K
0.010
0.001
0.007
0.037
0.005
0.008
0.006
0.000
0.000
tot. cat. tot. oxy.
5.000 7.959
5.000 7.952
5.000 7.590
5.000 8.005
5.000 8.028
5.000 8.016
5.000 8.028
5.000 7.869
5.000 8.022
An
6.73
2.00
0.56
3.85
2.16
2.76
2.24
0.00
0.00
Ab
92.30
97.89
98.90
92.35
97.33
96.41
97.19
100.00
100.00
Or
0.97
0.11
0.54
3.79
0.51
0.84
0.57
0.00
0.00
APPENDIX
.
Appendix II Table (2.5): Continue.
Oxide wt %
intermediate zone 3 4 5
1
2
SiO2
69.42
68.14
69.09
71.9
TiO2
0
0
0
Al2O3
18.65
18.78
18.7
Cr2O3
0
0
0
FeO
0
0
0
CaO
0.22
0.34
0.32
Na 2O
11.71
12.57
K2O
0
Total
100
6
7
68.63
68.49
68.59
0
0
0
0
20.77
19.59
19.57
19.49
0
0.3
0.35
0.26
0.01
0.04
0.03
0.04
0.28
0.38
0.38
0.39
11.55
11.38
10.9
10.86
10.65
0.17
0.34
0.17
0.19
0.32
0.59
100
100
100
100.01
104.51 100.03
cation propotions based on 8 oxygen cations
apfu
apfu
apfu
apfu
apfu
apfu
apfu
Si
3.036
2.957
3.022
3.022
3.016
3.011
3.018
Ti
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Al
0.961
0.960
0.964
1.029
1.015
1.014
1.011
Cr Fe +2
0.000
0.000
0.000
0.000
0.010
0.012
0.009
0.000
0.000
0.000
0.000
0.001
0.001
0.001
Ca
0.010
0.016
0.015
0.013
0.018
0.018
0.018
Na
0.993
1.058
0.980
0.927
0.929
0.926
0.909
K
0.000
0.009
0.019
0.009
0.011
0.018
0.033
tot. cat. tot. oxy.
5.000 8.020
5.000 7.904
5.000 8.005
5.000 8.068
5.000 8.059
5.000 8.052
5.000 8.057
An
1.03
1.46
1.48
1.33
1.87
1.86
1.92
Ab
98.97
97.67
96.65
97.71
97.02
96.27
94.64
Or
0.00
0.87
1.87
0.96
1.11
1.87
3.45
APPENDIX
.
Appendix II Table (2.6): Electron probe microanalysis data of K-feldspar minerals.
Intermediate zone Oxide wt %
1
2
3
4
5
6
7
8
SiO2
66.20
66.20
65.82
65.38
64.55
64.52
64.55
64.10
Al2O3
16.97
16.98
18.15
17.72
17.49
18.27
18.38
18.16
Na2O MgO K2 O CaO FeO Cr2O3
0.61
0.77
0.86
0.31
0.23
1.28
1.48
1.05
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
16.06
15.98
15.03
16.48
17.59
15.30
15.06
15.56
0.15
0.07
0.13
0.11
0.14
0.14
0.15
0.15
0.00
0.00
0.00
0.00
0.00
0.06
0.04
0.03
0.00
0.00
0.00
0.00
0.00
0.44
0.35
0.28
99.99
100.00
99.99
100.00
100.00
100.01
100.01
99.33
Total
cation propotions based on 8 oxygen Cations
apfu
apfu
apfu
apfu
apfu
apfu
apfu
apfu
Si Al Na Mg K Ca Fe +2 Cr tot.cat. tot.oxy.
3.06
3.06
3.04
3.03
2.98
2.97
2.97
2.97
0.93
0.93
0.99
0.97
0.95
0.99
1.00
0.99
0.06
0.07
0.08
0.03
0.02
0.11
0.13
0.09
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.95
0.94
0.89
0.97
1.04
0.90
0.88
0.92
0.01
0.00
0.01
0.01
0.01
0.01
0.01
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.02
0.01
0.01
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
8.03
8.02
8.06
8.01
7.93
7.97
7.96
7.97
An Ab Or
0.74
0.34
0.66
0.54
0.65
0.68
0.72
0.73
5.42
6.80
7.95
2.76
1.94
11.20
12.90
9.23
93.85
92.86
91.39
96.69
97.41
88.12
86.38
90.04
APPENDIX
.
Appendix II Table (2.7): Electron probe microanalysis data of Muscovite minerals. Border zone
Wall zone
Oxide wt % SiO2
1
2
3
4
1
2
3
4
5
6
47.18
47.10
48.35
50.03
46.35
46.57
45.34
46.23
46.18
45.72
TiO2
0.19
0.88
0.24
0.00
0.92
1.13
1.45
0.03
0.37
0.24
Al2O3 FeO MnO MgO CaO Na2O
38.08
37.45
38.67
37.75
37.42
36.84
36.08
38.10
35.97
36.27
0.68
0.70
0.70
0.00
0.87
1.16
1.05
1.22
1.48
1.45
0.00
0.00
0.00
0.00
0.01
-0.01
-0.01
0.00
0.00
-0.02
0.61
0.67
0.62
0.00
0.42
0.63
0.55
0.31
0.65
0.62
0.11
0.05
0.04
0.00
0.08
0.06
0.03
0.04
0.04
0.04
1.03
0.98
1.17
1.65
1.09
0.95
0.99
1.35
1.00
1.28
K2 O
9.27
9.23
9.36
10.56
8.87
9.12
8.95
9.99
9.16
9.93
Rb2O
0.00
0.00
0.00
0.00
0.14
0.05
0.08
-0.03
0.14
0.00
Cr2O3
0.00
0.00
0.00
0.00
-0.02
-0.01
-0.01
-0.02
-0.01
0.01
Cl Li2O*
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
H2O*
4.65
4.64
4.74
4.77
4.59
4.60
4.50
4.61
4.51
4.52
101.80
101.70
103.89
104.76
100.74
101.09
99.00
101.83
99.49
100.06
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
101.80
101.70
103.89
104.76
100.74
101.09
99.00
101.83
99.49
100.06
Subtotal O=F,Cl Total
cation propotions based on 12 oxygen Cations apfu apfu apfu apfu Si 6.09 6.09 6.11 6.28 Al iv 1.91 1.91 1.89 1.72 Al vi 3.88 3.79 3.87 3.87 Ti 0.02 0.09 0.02 0.00 Cr 0.00 0.00 0.00 0.00 Fe 0.07 0.08 0.07 0.00 Mn 0.00 0.00 0.00 0.00 Mg 0.12 0.13 0.12 0.00 Ca 0.02 0.01 0.01 0.00 Na 0.26 0.25 0.29 0.40 K 1.53 1.52 1.51 1.69 Rb 0.00 0.00 0.00 0.00 OH* 4.00 4.00 4.00 4.00 F 0.00 0.00 0.00 0.00 Cl 0.00 0.00 0.00 0.00 Total 17.89 17.86 17.88 17.97 Y total 4.09 4.08 4.08 3.87 X total 1.80 1.77 1.80 2.09 Al total 5.79 5.71 5.76 5.59 Fe/Fe+Mg 0.38 0.37 0.39 0.00 LiO2 calc. from Monier & Robert (1986)
apfu
apfu
apfu
apfu
apfu
apfu
6.05
6.07
6.04
6.02
6.13
6.07
1.95
1.93
1.96
1.98
1.87
1.93
3.82
3.74
3.71
3.86
3.77
3.75
0.09
0.11
0.15
0.00
0.04
0.02
0.00
0.00
0.00
0.00
0.00
0.00
0.10
0.13
0.12
0.13
0.16
0.16
0.00
0.00
0.00
0.00
0.00
0.00
0.08
0.12
0.11
0.06
0.13
0.12
0.01
0.01
0.00
0.01
0.01
0.01
0.28
0.24
0.26
0.34
0.26
0.33
1.48
1.52
1.52
1.66
1.55
1.68
0.01
0.00
0.01
0.00
0.01
0.00
4.00
4.00
4.00
4.00
4.00
4.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
17.86
17.86
17.87
18.06
17.92
18.07
4.08
4.09
4.08
4.06
4.10
4.05
1.78
1.77
1.79
2.00
1.83
2.02
5.76
5.66
5.67
5.84
5.63
5.68
0.54
0.51
0.52
0.69
0.56
0.57
H2O calculation after Tindle and Webb (1990) European Journal of Mineralogy, vol. 2, pgs. 595-610.
APPENDIX
.
Appendix II Table (2.7): Continue. Wall zone
Intermediate zone
Oxide wt % SiO2
7
8
9
1
2
3
4
5
49.76
49.21
66.30
49.79
49.82
49.91
45.82
46.91
TiO2
0.00
0.00
0.00
0.33
0.84
0.73
0.10
0.27
Al2O3 FeO MnO MgO CaO Na2O
36.90
37.16
17.86
36.17
35.83
35.45
36.57
37.35
1.08
1.40
0.15
1.07
1.57
1.38
1.55
1.63
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.00
1.01
0.49
0.68
0.13
0.12
0.00
0.00
0.00
0.00
0.00
0.00
0.05
0.05
1.49
1.13
0.30
0.87
1.35
0.88
0.42
0.63
K2 O
10.77
11.11
15.34
10.76
10.10
10.97
9.30
10.36
Rb2O
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.07
Cr2O3
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Cl Li2O*
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
H2O*
4.74
4.73
4.75
4.75
4.74
4.73
4.48
4.61
104.74
104.74
104.70
104.75
104.74
104.73
98.42
102.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
104.74
104.74
104.70
104.75
104.74
104.73
98.42
102.01
apfu
apfu
apfu
apfu
6.30
6.32
6.13
6.10
1.70
1.68
1.87
1.90
3.64
3.62
3.91
3.83
0.08
0.07
0.01
0.03
0.00
0.00
0.00
0.00
0.17
0.15
0.17
0.18
0.00
0.00
0.00
0.00
0.09
0.13
0.03
0.02
0.00
0.00
0.01
0.01
0.33
0.22
0.11
0.16
1.63
1.77
1.59
1.72
0.00
0.00
0.00
0.01
4.00
4.00
4.00
4.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
17.93
17.95
17.82
17.95
3.97
3.96
4.11
4.06
1.96
1.99
1.70
1.89
5.34
5.29
5.77
5.73
0.64
0.53
0.87
0.88
Subtotal O=F,Cl Total
cation propotions based on 12 oxygen Cations apfu apfu apfu apfu Si 6.29 6.24 8.36 6.29 Al iv 1.71 1.76 0.00 1.71 Al vi 3.79 3.80 2.66 3.68 Ti 0.00 0.00 0.00 0.03 Cr 0.00 0.00 0.00 0.00 Fe 0.11 0.15 0.02 0.11 Mn 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.19 Ca 0.00 0.00 0.00 0.00 Na 0.37 0.28 0.07 0.21 K 1.74 1.80 2.47 1.73 Rb 0.00 0.00 0.00 0.00 OH* 4.00 4.00 4.00 4.00 F 0.00 0.00 0.00 0.00 Cl 0.00 0.00 0.00 0.00 Total 18.01 18.02 17.58 17.96 Y total 3.91 3.94 2.67 4.01 X total 2.10 2.08 2.54 1.95 Al total 5.50 5.55 2.66 5.39 Fe/Fe+Mg 1.00 1.00 1.00 0.37 LiO2 calc. from Monier & Robert (1986)
H2 O calculation after Tindle and Webb (1990) European Journal of Mineralogy, vol. 2, pgs. 595-610.
APPENDIX
.
Appendix II Table (2.8): Electron probe microanalysis data of Tourmaline minerals. Border zone Oxide wt% SiO2 TiO2 Al2O3 Cr2O3 FeO MgO CaO MnO Na2O
Wall zone
Intermediate zone
1
1
2
3
4
5
6
7
8
1
2
3
37.1
34.9
38.5
39.0
37.3
37.0
37.7
39.4
39.1
36.4
35.5
34.5
0.7
0.0
0.0
0.0
0.0
0.7
0.8
0.7
1.0
0.5
1.0
1.2
35.9
34.2
34.6
33.8
33.4
34.8
33.4
33.7
33.9
36.0
35.3
35.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
11.6
18.5
12.9
11.0
15.8
10.8
11.7
8.2
8.9
13.2
13.0
13.7
1.8
0.9
1.1
2.8
1.3
3.5
3.1
3.7
3.6
1.0
0.8
0.3
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.1
0.0
0.0
0.2
0.0
0.0
0.0
0.0
0.1
0.0
0.4
0.0
0.2
0.3
0.5
1.6
1.1
2.0
2.4
1.6
1.9
2.3
2.6
2.2
1.4
1.5
1.6
B2O3
10.9
10.5
10.9
11.0
10.7
10.9
10.9
11.2
11.1
10.8
10.6
10.5
Li2O
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
H 2O* Li2O*
3.8
3.6
3.8
3.8
3.7
3.8
3.8
3.8
3.8
3.7
3.7
3.6
0.4
0.0
0.8
0.9
0.2
0.3
0.5
1.2
1.0
0.3
0.3
0.3
Total O=F Total*
104.2
103.6
104.6
104.7
103.9
103.9
104.2
105.0
104.8
103.7
102.1
101.4
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
104.16
103.62
104.62
104.75
103.92
103.85
104.21
105.02
104.82
103.75
102.06
101.42
Structural formula based on 31 anions (O, OH, F) apfu apfu apfu apfu
Cations T: Si Al B Z: Al Mg Cr Fe3+ Y: Al Ti V Cr Fe3+ Mg Mn Fe2+ Zn Li*
∑Y X: Ca Ba Na K Rb Cs vacancy (x) OH F Cl F content Mineral Name
apfu
apfu
apfu
apfu
apfu
apfu
apfu
apfu
5.91
5.77
6.11
6.14
6.06
5.91
6.03
6.15
6.11
5.87
5.82
5.74
0.09
0.23
0.00
0.00
0.00
0.09
0.00
0.00
0.00
0.13
0.18
0.26
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.65
0.44
0.47
0.28
0.40
0.46
0.29
0.19
0.25
0.70
0.64
0.61
0.09
0.00
0.00
0.00
0.00
0.08
0.10
0.08
0.11
0.06
0.13
0.15
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.44
0.22
0.27
0.67
0.31
0.82
0.75
0.87
0.85
0.24
0.19
0.06
0.03
0.00
0.00
0.00
0.00
0.01
0.00
0.05
0.00
0.03
0.04
0.08
1.54
2.57
1.72
1.45
2.14
1.44
1.57
1.07
1.16
1.78
1.78
1.90
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.25
0.00
0.54
0.60
0.15
0.19
0.29
0.73
0.62
0.17
0.22
0.20
3.00
3.22
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
3.00
0.01
0.00
0.00
0.00
0.00
0.02
0.00
0.00
0.00
0.01
0.01
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.49
0.34
0.61
0.74
0.51
0.59
0.70
0.80
0.68
0.45
0.48
0.51
0.01
0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.02
0.01
0.01
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.49
0.66
0.39
0.26
0.49
0.37
0.30
0.20
0.30
0.54
0.50
0.46
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
4.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Foitite
Foitite
Schorl
Schorl
Schorl
Schorl
Schorl
Schorl
Schorl
Foitite
Foitite
Schorl
Note/ H2O* calculated H2O from excel sheet software
APPENDIX
.
Appendix II Table (2.9): Electron probe microanalysis data of Zircon minerals.
Intermediate zone
Wall zone Oxide wt%
1
2
3
1
SiO2
30.8
31.6
38.7
35.5
ZrO2
69.2
68.4
61.3
59.2
HfO2
0.0
0.0
0.0
5.3
Total
100
100
100
100
cation propotions based on 4 oxygen Cations Si Zr Hf Total Zr/Hf
apfu
apfu
apfu
apfu
0.54
0.55
0.68
0.66
1.17
1.16
1.05
1.06
0.00
0.00
0.00
0.03
1.71
1.71
1.74
1.75
0.00
0.00
0.00
0.03
APPENDIX
.
Appendix II Table (2.10): Electron probe microanalysis data of Monazite minerals. Border zone Oxide wt%
1
2
SiO2
1.44
1.22
P2O5 CaO Y2O3
35.77
31.11
3.15
0.32
0.00
0.57
La2O3
0.00
10.54
Ce2O3
22.57
33.41
Pr2O3
0.00
3.49
Nd2O3
13.61
15.19
Er2O3 PbO ThO2
0.00
-0.28
0.00
-0.22
19.47
5.59
UO2
0.00
0.15
Sm2O3
3.99
0.00
Total
100.00
101.09
cation propotions based on 4 oxygen Cations Si P Ca Y La Ce Pr Nd Er Pb Th U Sm Total
apfu
apfu
0.05
0.05
1.08
1.00
0.12
0.01
0.00
0.01
0.00
0.15
0.29
0.46
0.00
0.05
0.17
0.21
0.00
0.00
0.00
0.00
0.16
0.05
0.00
0.00
0.05
0.00
1.92
1.97
APPENDIX
.
Appendix II Table (2.11): Electron probe microanalysis data of Columbite minerals. Wall zone Oxide wt % FeO MnO TiO2
1
2
3
4
5
15.24
18.11
14.36
14.13
11.98
7.79
5.13
2.62
6.96
4.56
5.00
5.03
3.35
7.14
4.76
Nb2O5
70.19
70.15
75.08
66.69
73.84
Ta2O5 Sc2O3
0.00
0.00
3.10
3.02
3.26
1.77
1.58
1.50
2.06
1.60
Total O=F Total
99.99
100.00
100.01
100.00
100.00
0.00
0.00
0.00
0.00
0.00
99.99
100.00
100.01
100.00
100.00
apfu
apfu
0.65
0.55
0.33
0.21
0.30
0.20
1.67
1.84
0.05
0.05
0.10
0.08
0.00
0.00
3.09
2.93
0.33
0.28
0.03
0.03
cation propotions based on 6 oxygen Cations apfu apfu apfu Fe 0.70 0.84 0.67 Mn 0.36 0.24 0.12 Ti 0.21 0.21 0.14 Nb 1.75 1.76 1.88 Ta 0.00 0.00 0.05 Sc 0.09 0.08 0.07 F 0.00 0.00 0.00 Total 3.12 3.12 2.93 Mn/(Mn+Fe) 0.34 0.22 0.16 Ta/(Ta+Nb) 0.00 0.00 0.02 A site B site C site
0.00
0.00
0.00
0.00
0.00
1.07
1.08
0.79
0.98
0.77
2.05
2.04
2.14
2.11
2.16
APPENDIX
.
Appendix II T able (2.12): Electron probe microanalysis data of Cordierite minerals. Border zone Oxide wt %
1
2
3
4
5
6
7
SiO2
51.54
51.75
51.45
51.89
51.86
51.76
51.48
Al2 O3
32.9
32.99
33.1
32.84
32.81
32.54
32.77
FeO
2.9
2.6
2.77
2.82
2.48
3.2
2.91
MgO
12.66
12.65
12.59
12.4
12.63
12.43
12.69
Total
100
99.99
99.91
99.95
99.78
99.93
99.85
cation propotions based on 18 oxygen Cations Si Al +2
Fe Mg
XMg= Mg*100/(Mg*Fe)
apfu
apfu
apfu
apfu
apfu
apfu
apfu
5.08
5.09
5.07
5.11
5.11
5.11
5.08
3.82
3.83
3.85
3.81
3.81
3.79
3.81
0.24
0.21
0.23
0.23
0.20
0.26
0.24
1.86
1.86
1.85
1.82
1.86
1.83
1.87
88.6121 89.6611 89.0127 88.6848 90.0769 87.3796 88.6012
Table (2.13): Electron probe microanalysis data of Andalusite minerals.
Border zone Oxide wt % SiO2 Al2O3 Total
1
2
3
4
5
6
38.54
37.69
38.36
37.91
37.90
36.63
61.46
62.31
61.64
62.01
61.68
62.88
100.00
100.00
100.00
99.92
99.58
99.51
apfu
apfu
apfu
1.02
1.03
0.99
1.97
1.97
2.01
2.99
2.99
3.00
cation propotions based on 5 oxygen Cations apfu apfu apfu Si 1.04 1.02 1.03 Al 1.95 1.98 1.96 Total
2.99
2.99
2.99
APPENDIX
.
Appendix II Table (2.14): Electron probe microanalysis data of Apatite minerals. Border zone Oxide wt%
1
2
3
4
5
6
CaO P2O5
50.35
51.15
49.2
50.45
50.45
50.16
47.84
46.82
46.88
47.11
47.39
46.31
Al2O3 F Cl Total
0
0
0.66
0.2
0.12
0.5
0
0
0.69
0.56
0.31
0.78
1.81
2.03
1.6
1.68
1.73
1.68
100
100
99.03
100
100
99.43
cation propotions based on 26 oxygen Cations Ca P Al F Cl
apfu
apfu
apfu
apfu
apfu
apfu
6.7
6.8
6.3
6.5
6.6
6.4
5.0
4.9
4.7
4.8
4.9
4.7
0.0
0.0
0.5
0.2
0.1
0.4
0.0
0.0
0.6
0.5
0.3
0.7
0.1
0.1
0.1
0.1
0.1
0.1
Table (2.15): Electron probe microanalysis data of Rutile minerals. Border zone Oxide wt%
Wall zone
1
2
1
2
3
4
5
6
7
8
9
SiO2
0.0
0.0
1.1
1.4
2.0
3.1
0.1
0.2
0.3
0.1
0.0
Al2O3
2.7
0.0
0.9
0.2
1.4
1.7
0.2
0.3
0.3
0.2
0.0
TiO2 FeO Nb2O5
78.7
97.2
88.7
93.2
87.6
89.4
93.9
93.7
94.9
91.7
100.4
4.2
0.0
1.7
1.2
1.6
1.0
1.6
1.4
1.7
2.1
0.0
14.4
4.0
7.6
4.1
7.1
4.8
4.2
4.3
2.9
5.0
3.8
Total
100.0
101.1
100.0
100.0
99.7
100.0
100.0
100.0
100.0
99.1
104.2
cation propotions based on 2 oxygen Cations Si Al Ti +2
Fe Nb Total
apfu
apfu
apfu
apfu
apfu
apfu
apfu
apfu
apfu
apfu
apfu
0.00
0.00
0.03
0.03
0.05
0.07
0.00
0.01
0.01
0.00
0.00
0.07
0.00
0.03
0.01
0.04
0.05
0.01
0.01
0.01
0.01
0.00
1.35
1.93
1.65
1.77
1.59
1.60
1.80
1.80
1.81
1.76
1.93
0.16
0.00
0.07
0.05
0.07
0.04
0.07
0.06
0.07
0.09
0.00
0.15
0.05
0.09
0.05
0.08
0.05
0.05
0.05
0.03
0.06
0.04
1.74
1.98
1.86
1.91
1.82
1.81
1.93
1.93
1.93
1.91
1.98
