Geology, published online on 24 April 2015 as doi:10.1130/G36499.1

Old continental zircons from a young oceanic arc, eastern Taiwan: Implications for Luzon subduction initiation and Asian accretionary orogeny Wen-Yu Shao1, Sun-Lin Chung1,2*, Wen-Shan Chen1, Hao-Yang Lee1, and Lie-Wen Xie3 Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan Institute of Earth Sciences, Academia Sinica, Taipei 11529, Taiwan 3 Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 1 2

ABSTRACT Accretionary orogeny that involves terrain accretion and subsequent reprocessing plays a crucial role in the Phanerozoic tectonics and continental growth of Asia. This study reports zircon U-Pb and Hf isotope data from the Chimei igneous complex, eastern Taiwan, part of the intra-oceanic Luzon arc that has accreted onto the Eurasian continental margin since ca. 5 Ma. Among 292 U-Pb dates and 267 Hf isotope ratios obtained for zircon separates from six andesites, ten grains of magmatic zircons gave a mean 206Pb/238U age at 9.0 ± 0.3 Ma, with eHf(t) values from +20 to +12, which we interpret as the emplacement age of the Chimei complex. Remaining zircons, however, show inherited ages clustering at ca. 14 Ma (n = 9) and ca. 220 Ma (n = 56, the largest peak), along with much older ages of ca. 0.7 Ga, 1.9 Ga, and 2.5 Ga. Whereas the ca. 14 Ma zircons may have crystallized from the earliest magmatism of the northern Luzon arc, the Indosinian and older zircons suggest Cathaysia-type sources that we attribute to a continental fragment that split off from the Eurasian margin by opening of the South China Sea and then drifted and accreted to the western Philippine Sea plate before the Luzon subduction initiation. Consequently, magmas derived from the depleted mantle wedge evolved and picked up the continental zircons during ascent. Our study not only better integrates regional tectonics with magmatic records in Southeast Asia, but also signifies a modern example from Taiwan that highlights the importance of ribbon continents in Asian orogenesis over time and space. INTRODUCTION Asia is a major part of the largest composite continent on Earth today, which was enlarged by successive accretion of dispersed terrains and massive production of juvenile crust in the Phanerozoic (Şengör et al., 1993; Jahn, 2004). In addition to complex accretionary tectonic processes, arc-continent collision has been widely accepted to be an important mechanism for continental growth not only in Asia, but worldwide through geologic time (Şengör et al., 1993). Taiwan is situated in an active arc-continent collision zone (Fig. 1) and represents a unique natural laboratory for studying the details of ongoing orogenic processes that have built up this particular part of the continent, where the northern Luzon arc started colliding with, and accreting on to, the Eurasian continental margin at ca. 5 Ma (Teng, 1990). Here we report for the first time a combined in situ analysis of zircon U-Pb ages and Hf isotopes of the Chimei igneous complex from the Coastal Range, eastern Taiwan; i.e., the northernmost part of the Luzon arc system formed within an intra-oceanic setting by eastward subduction of the South China Sea plate beneath the Philippine Sea plate (Fig. 1). The result leads us to conclude: (1) the Chimei complex was emplaced at ca. 9 Ma and sourced from the depleted mantle wedge; (2) it contains a set of magmatic zircons that crystal*E-mail: [email protected]

nental crust origin, thus suggesting the existence of a Cathaysia-rifted fragment under the northern Luzon arc. The last point is a critical new parameter to underpin and constrain the tectonic reconstruction and geophysical modeling studies of the region, and supports the hypothesis of “ribbon continent” (Şengör, 1984), considered of central importance not only in the geologic evolution of Southeast Asia but throughout Asian orogenesis and continental growth. LUZON ARC AND CHIMEI COMPLEX The Luzon arc system is located on the western margin of the Philippine Sea plate (Fig. 1) as a result of subduction of the South China Sea plate that underwent seafloor spreading between ca. 32 and 15.5 Ma (Briais et al., 1993). The Coastal Range of eastern Taiwan, which consists mainly of Miocene volcanic sequences overlain by Plio-Pleistocene turbidites (Teng, 1990), is the northernmost portion of the northern Luzon arc. The volcanic sequences are composed essentially of basaltic to andesitic pyroclastics,

lized at ca. 14 Ma and, together with other lines of evidence, may constrain the onset time of Luzon subduction initiation; and (3) it contains abundant Indosinian and older zircons of conti-

Eurasian Continent

120°E

Taiwan

Ryukyu arc Ryukyu Trench

Coastal Range

Continental margin Manila Trench

20°N

South China Sea

Philippine Sea ~9

15°N

cm

/y

Pliocene-Pleistocene strata

Miocene volcanics

North Luzon arc

Luzon

Coastal Range, Eastern Taiwan

Chimei

ophiolitic rocks

Chimei igneous complex (Fig. DR1)

r

N

Philippine Trench

Mindoro

23.5°N

Lichi mélange

23°N

km

Palawan 10°N

Sulu Sea

0

20 121.5°E

Figure 1. Tectonic framework depicting main plates and structures around Taiwan, along with simplified geological map of Coastal Range, eastern Taiwan.

GEOLOGY, June 2015; v. 43; no. 6; p. 1–4; Data Repository item 2015168  | doi:10.1130/G36499.1  |  Published online XX Month 2015

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Geology, published online on 24 April 2015 as doi:10.1130/G36499.1

SAMPLES AND METHODS Twenty-five (25) basaltic andesite and andesite samples (SiO2 = 55–63 wt%) were collected from the Chimei complex (Fig. DR1 in the GSA Data Repository1). Bulk geochemistry data (Table DR1 in the Data Repository) show that they exhibit flat rare earth element (REE) to mildly enriched light REE (LREE) patterns [(La/Yb)N = 1–2], coupled geochemical features similar to those of intra-oceanic arc lavas, characterized by depletions in high field strength elements (HFSEs) (Nb, Ta, Ti) and enrichments in large-ion lithophile elements (LILEs) and Pb (Fig. DR2). They all display depleted mantle– type isotopic signatures, with low 87Sr/86Sr ratios (0.7039–0.7042) and high values of eNd(t) (+9.4 to +5.8) and eHf(t) (+20.7 to +16.6) (Table DR1). Analytical methods for bulk geochemistry and zircon U-Pb and Lu-Hf isotope ratios are given in the Data Depository.

60

Chimei zircons (N = 292, six samples)

Number

50 40

218 ± 3 Ma (N = 56)

30

1863 ± 10 Ma (N = 31)

726 ± 16 Ma (N = 13)

20

A

2522 ± 19 Ma (N = 13)

10 0 25

0

400

800

1200

20

14.2 ± 0.4 Ma (N = 9)

15

5 0

(Ma) 10

218 ± 3 Ma 9 (N = 56) 8

24 ± 2 Ma (N = 5) 34 ± 4 Ma (N = 4)

10

1600

B

9.0 ± 0.4 Ma (N = 11)

2000

CM-10

C

2400 18

CM-10

Relative probability

tuffs, and lava flows, and erupted mostly in an oceanic environment from the middle to late Miocene (Lai and Song, 2013). The Chimei complex is a principal igneous exposure in the central part of the Coastal Range (Fig. 1). It consists of diabase and andesitic flows and pyroclastics that experienced various degrees of hydrothermal alteration. The emplacement age of the Chimei complex has been documented rather broadly using K-Ar and Ar-Ar methods (ca. 30–9 Ma; Richard et al., 1986; Lo et al., 1994) and the zircon fission-track method (ca. 16–8 Ma; Yang et al., 1995), and interpreted to document one of the earliest magmatic events in the northern Luzon arc. A “depleted” isotopic composition, with 87Sr/86Sr of ~0.7034 and eNd(t) value of +6.3, has been reported from the complex (Chen et al., 1990), consistent with an origin in an intra-oceanic arc setting.

2800

D

16 14 12

9.0 ± 0.3 Ma 14.1 ± 0.4 Ma (N = 10; MSWD = 1.5) (N = 8; MSWD = 1.2)

0

50

100

150

200

U-Pb age ( Ma)

250

300

Figure 2. A: U-Pb age spectra of zircons from Chimei complex, eastern Taiwan. Numerical value (N) denotes number of grains. B: Age spectra of zircons younger than 300 Ma. C,D: Weighted mean 206Pb/238U ages of Miocene zircons from sample CM-10.

variable Th/U ratios (2.44–0.01) (Table DR2). Additionally, four Cenozoic populations are identified at 9.0 ± 0.4 Ma (n = 11), 14.2 ± 0.4 Ma (n = 9), 24 ± 2 Ma (n = 5), and 34 ± 4 Ma (n = 4), respectively (Fig. 2B). These younger zircons are long to short prismatic (~100–250 mm in length), euhedral to subhedral, and colorless to light yellow, and show generally homogeneous cathodoluminescence and backscattered electron images occasionally with growth zoning (Fig. DR3), suggesting an origin from magmatic crystallization. Sample CM-10, specifically, contains the most abundant grains of young zircons at 9.0 ± 0.3 Ma (2s; n = 10 and mean square of weighted

deviates [MSWD] = 1.5; Fig. 2C), 14.1 ± 0.4 Ma (n = 8 and MSWD = 1.2; Fig. 2D), and 24.0 ± 4.3 Ma (n = 3; Table DR2). The youngest ten grains, with low U (58–269 ppm) and uniform Th/U ratios (1.2–2.0), are interpreted as magmatic zircons that crystallized directly or in situ from the host magma, and thus indicate the age of the main Chimei complex (see below). Hf Isotopes Lu-Hf isotope data were obtained for 267 grains of the dated zircons; data are given in Table DR3 and plotted in Figure 3. Some smaller grains could not be analyzed for Lu-Hf isotope compositions. Most Cenozoic zircons

1  GSA Data Repository item 2015168, data tables with methods, sample locality map, zircon age diagrams, and whole rock geochemical plots, is available online at www.geosociety.org/pubs/ft2015.htm, or on request from [email protected] or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA.

Detrital zircons from Cathaysia

Chimei “old” zircons

120 100 80 60 40 20 0

Number

U-Pb Ages U-Pb ages of 292 grains of zircon separates from six Chimei samples were obtained (Fig. 2; Fig. DR3; Table DR2). The Chimei zircons, surprisingly, are overwhelmed with old, inherited zircons (Fig. 2A). The largest population is of Indosinian ages peaking at 218 ± 3 Ma (n = 56), along with many Precambrian zircons at 726 ± 16 Ma (n = 13), 1863 ± 10 Ma (n = 31), and 2522 ± 19 Ma (n = 13), respectively. The grains are generally subhedral to oval and exhibit variable but mostly high U concentrations (>400 ppm, and up to 8176 ppm), coupled with highly

εHf(t)

ZIRCON DATA

Figure 3. Plots of eHf(t) values versus U-Pb ages of Chimei (Taiwan) zircons. Shaded area represents field of detrital zircons from Cathaysia (Yu et al., 2010). Age histogram of Chimei “old” zircons is also plotted, with numbers given in lower right-hand side. DM—depleted mantle; CHUR—chondritic uniform reservoir; TDMC—crustal model age.

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Geology, published online on 24 April 2015 as doi:10.1130/G36499.1

Petrogenesis and Tectonic Interpretation The zircon data described above enable us to propose a new model, suggesting that a conti-

Y

Luzon

Se

Y

Philippine Sea plate

accreted continental fragment

D

Cretaceous granitoids

t

e ng

B

15 Ma Eastern Taiwan

bel

northern Luzon arc (Chimei complex)

a

Palawan Taiwan

ko

South C h in a

Mindoro

Yuli belt

Coas Rang tal e

Sulu Sea Manila Trench

9 Ma

accreted continental fragments

Philippine Sea

Palawan (after Hall, 2002)

30 Ma

Ta i lu

South China Sea Mindoro

0 Ma

Ra

attenuated continental crust

e

GEOLOGY  |  Volume 43  |  Number 6  | www.gsapubs.org

Manila Trench

C

Taiwan

Cathaysia

northern Luzon arc

at

Abundant Zircons of Cathaysian Affinity A prominent feature observed in this study is that an overwhelming majority of zircons from the Chimei andesites are old, inherited grains. These old zircons, moreover, show U-Pb and

Ryukyu Trench

continental margin

X Cathaysia

A

Taiwan

Cathaysia X

pl

Initiation of Luzon Arc Magmatism We argue that the older Miocene age (14.1 ± 0.4 Ma) from sample CM-10 can be used to explore earlier magmatism of the Chimei complex specifically and the northern Luzon arc in general. These zircons also have low U contents (44–269 ppm) and uniform Th/U (0.7–2.0), and high eHf(t) values indistinguishable from those of the 9 Ma population. The U concentrations and Hf isotope compositions, moreover, resemble those of magmatic zircons (ca. 9.2–6.5 Ma) from elsewhere in the Coastal Range (Fig. 3; Fig. DR4). In the latter, inherited zircons of ca. 15–10 Ma have also been observed rarely (Shao et al., 2014; Shao, 2015). These data suggest that the northern Luzon arc magmatism began from the middle Miocene, even though the arc magmas produced in the early stage are rarely exposed and are covered by younger, and more voluminous, eruptions (Lai and Song, 2013).

9 Ma

tral

Emplacement Age of Chimei Complex We argue that the emplacement age of the Chimei complex is best constrained by the ten youngest grains of zircons from sample CM-10, yielding a mean 206Pb/238U date at 9.0 ± 0.3 Ma. Given the fact that the host rocks have low Zr contents (41–77 ppm; Table DR1), the scarcity of magmatic zircons is not totally unexpected. The rocks also have low U and Th contents (Table DR1), corresponding to the low U-Th range of the magmatic zircons. This age is coeval, within analytical errors, with a zircon 206 Pb/238U age at 9.2 ± 0.4 Ma obtained from an andesitic lava flow in the southern part of the Coastal Range (Shao, 2015) and older than the main duration (ca. 8.5–6.5 Ma) of the volcanism in eastern Taiwan as constrained by zircon geochronology (Shao, 2015). Therefore, the Chimei complex is indeed one of the oldest igneous exposures in the northern Luzon arc.

nental fragment or microcontinent existed in the intra-oceanic arc. Such a model can best explain the petrogenesis of the Chimei complex specifically and the northern Luzon subduction zone in general (Fig. 4). This model, likewise, accounts for the initiation of Luzon subduction. We propose that the northern Luzon arc terrain was underlain in part with a Cathaysia-derived fragment (Fig. 4B), which was rifted from the continental margin of the South China block during opening of the South China Sea and then drifted and accreted to the western margin of the Philippine Sea (Figs. 4A and 4C). Such a tectonic framework gave rise to, or at least facilitated, the initiation of eastward subduction of the younger, and thereby intrinsically more buoyant, South China Sea plate beneath the older and presumably denser western Philippine Sea plate. The initiation of subduction must have occurred by the middle Miocene, prior to the onset (ca. 14 Ma) of the resultant arc magmatism, and accommodated the transition from an Andean-type to a western Pacific–type plate boundary along with subduction reversal in this particular part of Southeast Asia (Li et al., 2012). Consequently, parental magmas derived from the depleted mantle wedge of the northern Luzon subduction zone (Fig. 4B) picked up old zircons from the accreted Cathaysian continental crust during magma ascent and/or in the magma chamber. The degree of crustal involvement can be estimated by a binary mixing calculation, using Sr-Nd-Hf isotope data from the host rocks (Fig. DR5), which shows

Cen

DISCUSSION

Hf isotopic systematics (Fig. 3) comparable to those of detrital zircon records from the Cathaysian block, South China (Yu et al., 2010, and references therein). The dominant Indosinian-aged grains display highly heterogeneous eHf(t) values, which require an “old” continental crust component involved significantly in the formation of their host rocks, a petrogenetic scenario that has been generally proposed for Indosinian granitoids widespread in the Cathaysian Block (cf. Yu et al., 2010). Furthermore, most of the Chimei old zircons have high U contents, with means of ~1000 ppm for the Indosinian and ~380 ppm for older grains (Fig. DR4), which differ markedly from those of the Miocene zircons but, again, resemble those of Cathaysian detrital zircons. Our counterpart study elsewhere along the northern Luzon arc (Shao et al., 2014; Shao, 2015) also indicates that inherited zircons of Cathaysian affinity are abundant in other young igneous rocks. These “old” zircons, as Chimei’s, show high U contents (Fig. DR4) and variable Hf isotope ratios, in contrast to the Miocene (ca. 9.2–6.5 Ma) magmatic zircons that crystallized from host lavas and exhibit uniformly high and positive eHf(t) values (Fig. 3), coupled with low U concentrations (Fig. DR4). We argue the occurrence of old, Cathaysia-type inherited zircons to be a common feature in arc magmas over the northern Luzon subduction zone.

E as te rn

reveal very high Hf isotope ratios. In sample CM-10, the 9 Ma population (n = 9) gave eHf(t) values from +19.9 to +12.5, and the 14 Ma population (n = 6) gave eHf(t) values from +19.5 to +13.3 (Fig. 3). These are in general accord with the whole-rock eHf(t) range of +20.7 to +16.6. The older zircons, by contrast, display highly variable Hf isotope ratios (Fig. 3). For example, the Indosinian zircons reveal eHf(t) values from +16.0 to -37.6, yielding a large range of crustal model ages (TDMC) from ca. 100 Ma to 3540 Ma (Table DR3) suggestive of heterogeneous source compositions.

9 Ma

Figure 4. A: Paleogeographic construction of Southeast Asia at 9 Ma (after Hall, 2002). B: Schematic profile of the X-Y line in A depicting involvement of an accreted continental fragment in northern Luzon arc magma generation. C: Cartoon showing “ribbon continents” split off Eurasian margin and “yo-yo” journey of rifted fragment. D: Present-day major geologic units of eastern Taiwan. Pink region shows position of northern Luzon arc system.

3

Geology, published online on 24 April 2015 as doi:10.1130/G36499.1 ≤2% assimilation of older continental crust in the petrogenesis of the Chimei complex. Substantial amounts of such crustal contamination, up to ~20%, however, would be required to account for the significant isotopic variations observed over the entire northern Luzon arc (Fig. DR5). The crustal contaminant may have melted almost completely, except for zircon and other resistant accessary minerals that survived and became xenocrysts in the rocks produced. More specifically, under the Chimei complex, a massive Indosinian crustal body must have preexisted and become involved, together with other country rocks of the Cathaysian crust, in the petrogenesis. BROADER IMPLICATIONS Our new model has important implications about Taiwan orogeny. In contrast to existing models, most of which regard the Eurasian continental margin “conventionally” as a coherent plate before the Luzon arc collision, we argue for a “yo-yo” tectonic cycle (Fig. 4C) that involves the rifting of a micro-continent from Cathaysia, its drifting and accretion to the western Philippine Sea margin, and backward voyage in association with the northern Luzon arc to build up Taiwan (Fig. 4D). Several other continental blocks (e.g., Palawan and Mindoro) in the southern South China Sea were also split off the Eurasian margin during this period (Hall, 2002). In Taiwan, the accreted continent is now exposed in the eastern Central Range, as a major constituent of the Tanan’ao basement complex consisting of the Tailuko belt in the west and the Yuli belt in the east (Fig. 4D). The accretion may have occurred in tandem (Shyu et al., 2005), with separate sutures on both sides of the accreted sliver that is caught between the northern Luzon arc and preexistent Eurasian margin (Lu and Hsu, 1992). Whereas details will be presented elsewhere, we believe that our model also better explains the evolution of the Yuli belt, hosting Earth’s youngest glaucophane schist and associated rocks formed in a Miocene accretionary setting (Shao, 2015). The accretion of micro-continents and/or volcanic arcs on to continental margins is a common phenomenon throughout the geologic record, as exemplified in the Central Asian (Şengör et al., 1993; Jahn, 2004) to eastern Tethyan (Şengör, 1984; Chung et al., 2013) orogenic belts. In ancient and particularly intraoceanic arc terranes, xenocrystic zircons from unobserved continental sources have been often reported (Kröner, 2010). Discoveries of old continental zircons from young arc lavas also have been documented in localities such as East Java (Indonesia; Smyth et al., 2007) and the Solomon Islands (southwest Pacific Ocean; Tapster et al., 2014), around the complex subductionaccretion-collision domain in Southeast Asia

which may evolve to resemble Central Asia by ongoing collision with the advancing Australian continent. Our study highlights another modern example from Southeast Asia that could help better understand how old continental material may be introduced into young arc settings. Moreover, it reinforces the notion of “ribbon continent” (Şengör, 1984) that appears to have played a key role in not only the tectonic evolution of Southeast Asia, but also Asian orogenesis and continental growth over time and space.

boundary: Tectonophysics, v. 532–535, p. 271– 290, doi:10.1016/j.tecto.2012.02.011. Lo, C.-H., Onstott, T.C., Chen, C.-H., and Lee, T., 1994, An assessment of 40Ar/ 39Ar dating for the whole-rock volcanic samples from the Luzon Arc near Taiwan: Chemical Geology, v. 114, p. 157–178, doi:10.1016/0009-2541(94)90049-3. Lu, C.-Y., and Hsu, K.J., 1992, Tectonic evolution of the Taiwan mountain belt: The Petroleum Geology of Taiwan, v. 27, p. 21–46. Richard, M., Bellon, H., Maury, R.C., Barrier, E., and Juang, W.-S., 1986, Miocene to recent calc-alkaline volcanism in eastern Taiwan: K-Ar ages and petrography: Tectonophysics, v. 125, p. 87–102, doi:10.1016/0040-1951(86)90008-9. ACKNOWLEDGMENTS Şengör, A.M.C., 1984, The Cimmeride Orogenic Shao thanks the Ph.D. student fellowships from System and the Tectonics of Eurasia: GeologiNational Taiwan University and Ministry of Science cal Society of America Special Paper 195, 74 and Technology, Taiwan. This study was supported p., doi:10.1130/SPE195-p1. by MOST 103-2745-M-002-005-ASP. Reviews Şengör, A.M.C., Natal’in, B.A., and Burtman, V.S., from M.E. Bickford, S.Y. O’Reilly, W.L. Griffin, and 1993, Evolution of the Altaid tectonic collage an anonymous reviewer helped improve the paper and Paleozoic crustal growth in Eurasia: Nature, significantly. v. 364, p. 299–307, doi:10.1038/364299a0. Shao, W.-Y., 2015, Zircon U-Pb and Hf isotope conREFERENCES CITED straints on the petrogenesis of igneous rocks Briais, A., Patriat, P., and Tapponnier, P., 1993, in eastern Taiwan [unpublished Ph.D. thesis]: Updated interpretation of magnetic anomalies Taipei City, National Taiwan University, 287 p. and seafloor spreading stages in the South China (in Chinese). Sea: Implications for the Tertiary tectonics of Shao, W.-Y., Chung, S.-L., and Chen, W.-S., 2014, SE Asia: Journal of Geophysical Research, Zircon U-Pb age determination of volcanic v. 98, p. 6299–6328, doi:10.1029/92JB02280. eruptions in Lutao and Lanyu, the northern Chen, C.-H., Shieh, Y.-N., Lee, T., Chen, C.-H., and Luzon magmatic arc: Terrestrial, Atmospheric Mertzman, S.A., 1990, Nd-Sr-O isotopic eviand Oceanic Sciences, v. 25, p. 149–187, dence for source contamination and an unusual doi:10.3319/TAO.2013.11.06.01(TT). mantle component under Luzon Arc: GeochiShyu, J.B.H., Sieh, K., and Chen, Y.-G., 2005, Tanmica et Cosmochimica Acta, v. 54, p. 2473– dem suturing and disarticulation of the Taiwan 2483, doi:10.1016/0016-7037(90)90234-C. orogen revealed by its neotectonic elements: Chung, S.-L., Chiu, H.-Y., Lee, H.-Y., Shao, W.-Y., Earth and Planetary Science Letters, v. 233, Zarrinkoub, M.H., and Wu, F.-Y., 2013, Asian p. 167–177, doi:10.1016/j.epsl.2005.01.018. continental growth in the Phanerozoic: Zircon Smyth, H.R., Hamilton, P.J., Hall, R., and Kinny, Hf isotopic constraints from the central Asian P.D., 2007, The deep crust beneath island arcs: to eastern Tethyan orogenic belts, in ProceedInherited zircons reveal a Gondwana contiings, Geological Society of China and Geologinental fragment beneath East Java, Indonesia: cal Society of America Joint Meeting, “Roof of Earth and Planetary Science Letters, v. 258, the World”, Chengdu, China, 17–19 June 2013: p. 269–282, doi:10.1016/j.epsl.2007.03.044. Acta Geologica Sinica (English edition), v. 87, Tapster, S., Roberts, N.M.W., Petterson, M.G., Saunp. 298. ders, A.D., and Naden, J., 2014, From contiHall, R., 2002, Cenozoic geologic and plate tecnent to intra-oceanic arc: Zircon xenocrysts tonic evolution of SE Asia and the SW Pacific: record the crustal evolution of the Solomon Computer-based reconstructions, model and island arc: Geology, v. 42, p. 1087–1090, doi:​ animations: Journal of Asian Earth Sciences, 10.1130​/G36033.1. v. 20, p. 353–431, doi:10.1016/S1367-9120​ Teng, L.S., 1990, Geotectonic evolution of late Ceno(01)​00069-4. zoic arc-continent collision in Taiwan: TectoJahn, B.-M., 2004, The Central Asian Orogenic Belt nophysics, v. 183, p. 57–76, doi:10.1016​/0040​ and growth of the continental crust in the Pha-1951​(90)​90188-E. nerozoic, in Malpas, J., et al., eds., Aspects of the Tectonic Evolution of China: Geological Yang, T.-F., Tien, J.-L., Chen, C.-H., Lee, T., and Punongbayan, R.S., 1995, Fission-track datSociety of London Special Publication 226, p. ing of volcanics in the northern part of the Tai73–100, doi:10.1144/GSL.SP.2004.226.01.05. wan-Luzon Arc: Eruption ages and evidence Kröner, A., 2010, The role of geochronology in underfor crustal contamination: Journal of Southstanding continental evolution, in Kesky, T.M., east Asian Earth Sciences, v. 11, p. 81–93, et al., eds., The Evolving Continents: Underdoi:10.1016/0743-9547(94)00041-C. standing Processes of Continental Growth: Geological Society of London Special Publication Yu, J.-H., O’Reilly, S.Y., Wang, L.-J., Griffin, W.L., and Zhou, M.-F., 2010, Components and episodic 338, p. 179–196, doi:10.1144/SP338.9. growth of Precambrian crust in the Cathaysia Lai, Y.-M., and Song, S.-R., 2013, The volcanoes Block, South China: Evidence from U-Pb ages of an oceanic arc from origin to destruction: and Hf isotopes of zircons in Neoproterozoic sedA case from the northern Luzon arc: Journal iments: Precambrian Research, v. 181, p. 97–114, of Asian Earth Sciences, v. 74, p. 97–112, doi:​ doi:10.1016/j.precamres​.2010​.05.016. 10.1016​/j​.jseaes​.2013​.03.021. Li, Z.-X., Li, X.-H., Chung, S.-L., Lo, C.-H., Xu, S., Manuscript received 3 December 2014 and Li, W.-X., 2012, Magmatic switch-on and Revised manuscript received 3 March 2015 switch-off along the South China continental Manuscript accepted 5 March 2015 margin since the Permian: Transition from an Andean-type to a Western Pacific-type plate Printed in USA

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Geology, published online on 24 April 2015 as doi:10.1130/G36499.1

Geology Old continental zircons from a young oceanic arc, eastern Taiwan: Implications for Luzon subduction initiation and Asian accretionary orogeny Wen-Yu Shao, Sun-Lin Chung, Wen-Shan Chen, Hao-Yang Lee and Lie-Wen Xie Geology published online 24 April 2015; doi: 10.1130/G36499.1

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Notes

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