Lithos 190–191 (2014) 328–348

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Age and geochemistry of western Hoh-Xil–Songpan-Ganzi granitoids, northern Tibet: Implications for the Mesozoic closure of the Paleo-Tethys ocean

Li-Yun Zhang a,⁎, Lin Ding a, Alex Pullen b,c,QiangXua,De-LiangLiua, Fu-Long Cai a,Ya-HuiYuea, Qing-Zhou Lai a,Ren-DengShia, Mihai N. Ducea b,d,PaulKappb,AlanChapmane a Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, People's Republic of China b Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA c Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, USA d Universitatea Bucuresti, Facultatea de Geologie Geofizica, Str. N. Balcescu Nr 1., Bucuresti 010041, Romania e Department of Geological Sciences and Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA article info abstract

Article history: A geologic investigation was undertaken in the Hoh-Xil–Songpan-Ganzi (HXSG) complex, northern Tibet in Received 21 May 2013 order to better understand magma genesis and evolution during the late stages of Paleo-Tethys ocean closure. Accepted 23 December 2013 The HXSG complex is composed of vast accumulations of Middle–Upper Triassic marine gravity flow deposits Available online 3 January 2014 that were extensively intruded by igneous rocks. These early Mesozoic rocks exposed in this area record a rich history of accretionary tectonics during the amalgamation of the Tibetan Plateau terranes. Eight plutons sampled Keywords: from the western HXSG complex yield zircon U–Pb ages that range from 225 to 193 Ma. Muscovite 40Ar/39Ar ages Hoh-Xil–Songpan-Ganzi Tibet for the Hudongliang and Zhuonai Lake plutons yield ages of 210.7 ± 2.5 Ma and 212.7 ± 2.5 Ma, respectively. Granitoids These plutonic rocks can be subdivided into two geochemically distinct groups. Group 1 (221–212 Ma: Paleo-Tethys Dapeng Lake, Changhong Lake and Heishibei Lake plutons) is composed of high-K calc-alkaline rocks that

Rollback have strongly fractionated REE patterns with high (La/Yb)N ratios (91–18) and generally lack Eu anomalies (Eu*/ Eu = 1.02–0.68). Rocks in Group 1 display pronounced negative Nb–Ta and Ti anomalies on primitive mantle- normalized spidergrams. Group 1 rocks exhibit high Sr (782–240 ppm) and low Y (6.3–16.0 ppm) contents with 87 86 high Sr/Y ratios (84–20). Based on Sr–Nd–Hf isotopic data ( Sr/ Sri = 0.7079–0.7090, εNd(t) = −7.7–−4.7, εHf(t) = −5.7–−0.8) and low MgO contents (MgO = 1.10–2.18%), Group 1 rocks are geochemically similar to adakitic rocks and were probably derived from partial melting of the downgoing Paleo-Tethys oceanic slab and overlying marine sediments. Group 2 plutons (225–193 Ma: Daheishan, Yunwuling, Zhuonai Lake, Malanshan

and Hudongliang plutons) display lower P2O5 with increasing SiO2 and are medium-K to high-K I-type calc- alkaline bodies with low Sr (14–549 ppm) and high Y (22.3–10.5 ppm) contents. Group 2 rocks have variable

fractionated REE patterns ((La/Yb)N =3–38) and negative Eu anomalies (Eu*/Eu = 0.02–0.86). Together with 87 86 Sr–Nd–Hf isotopes ( Sr/ Sri = 0.7072–0.7143, εNd(t) = −6.6–−2.0, εHf(t) = −0.6–+3.0), Group 2 rocks are most likely formed by partial melting of the juvenile crustal sources. Collectively, these data suggest that the Hoh-Xil turbidites were underlain by more continental arc crust than previously thought. We propose that rollback of the subducting Paleo-Tethys oceanic slab led to partial melting of overlying continental arc fragments which developed beneath the HXSG gravity flow deposits. © 2013 Elsevier B.V. All rights reserved.

1. Introduction deformed calciclastic and siliciclastic Middle–Upper Triassic deep- water gravity flow deposits widely regarded as turbidites or flysch The Hoh-Xil–Songpan-Ganzi (HXSG) complex is located in the derived from adjacent continental landmass (Bruguier et al., 1997; northern Tibet between the Kunlun arc terrane to the north, the South Ding et al., 2013; Enkelmann et al., 2007; Gu, 1994; Nie et al., 1994; China block to the east, and the Qiangtang terrane and Yidun arc to Zhang et al., 2008c; Zhou and Graham, 1996). These deposits are vast, the south (Fig. 1) and is widely considered as a ‘remnant’ of the Paleo- with an areal exposure of N200,000 km2 and thicknesses that range Tethys Ocean (Yin and Harrison, 2000; Zhou and Graham, 1996). from 5 to 15 km (Chang, 2000; Xu et al., 1992; Zhou and Graham, Rocks exposed in the HXSG complex mainly consist of moderately 1996). These turbidites were extensively intruded by Late Triassic– Early Jurassic granitoids (Fig. 1, Hu et al., 2005; Huang et al., 2003; ⁎ Corresponding author. Tel./fax: +86 1084097104. Roger et al., 2004; Shi et al., 2009; Weislogel, 2008; Xiao et al., 2007; E-mail address: [email protected] (L.-Y. Zhang). Yuan et al., 2010; Zhang et al., 2006, 2007) and minor volcanic rocks

0024-4937/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.lithos.2013.12.019 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 329

Fig. 1. Simplified tectonic map of the Tibetan Plateau showing major terranes and Late Triassic igneous rocks. Modified after Wang et al. (2011b) and Yin and Harrison (2000) and Zircon U–Pb isotope ages for Late Triassic to Early Jurassic magmatic rocks are from references Cai et al. (2010), Ding et al. (2011), Dai et al. (2013), Fu et al. (2010), Hu et al. (2005), Kapp et al. (2003), Liu et al. (2006), Lü et al. (2006), Reid et al. (2007), Roger et al. (2003, 2004), Shi et al. (2009), Wang et al. (2011a,b), Weislogel (2008), Xiao et al. (2007), Yuan et al. (2009, 2010), Zhai et al., 2012, Zhang et al. (2006, 2007, 2008a, 2011) and this study.

were interbedded within the Late Triassic gravity flow deposits (Cai 240 Ma calcic/calc-alkaline plutonic and volcano-clastic rocks consid- et al., 2010; Wang et al., 2011b). The geodynamic significance of the ered to be the products of northward subduction of Paleo-Tethys eastern HXSG igneous rocks is widely debated (e.g. Pullen et al., 2008; oceanic lithosphere (Harris et al., 1988; Jiang et al., 1992; Matte et al., Roger et al., 2010; Şengör, 1984; Weislogel, 2008; Yuan et al., 2010; 1996; Yang et al., 1996). Harris et al. (1988) concluded that the Kunlun Zhang et al., 2006, 2007, 2008a,b). However, coeval magmas in western granitoids were derived from melting of a garnet-bearing source at HXSG complex are still poorly understood (Roger et al., 2004; Wang middle-lower crust above a subduction zone. These Permian to Triassic et al., 2011b). rocks are thought to be super imposed on an early Paleozoic arc (Jiang Models suggest that the HXSG turbidites were deposited in: (1) a et al., 1992; Şengör, 1984). Igneous rocks in the range of 230–190 Ma back-arc basin (Gu, 1994; Şengör, 1984); (2) a rift basin (Chang, 2000; exposed in the eastern Kunlun belt were likely emplaced in a post- Chen et al., 1987); (3) a remnant-ocean basin (Zhou and Graham, collisional setting (Dai et al., 2013; Ding et al., 2011; Harris et al., 1988; 1996); or (4) a Mediterranean-style rollback basin (Ding et al., 2013; Jiang et al., 2012; Liu et al., 2004). Other isotopic, paleontological and Pullen et al., 2008). Differentiating between these models and thus kinematic investigations suggest that the closure time of the northern improving our understanding of the final stages of ocean basin closure Paleo-Tethys ocean along the AKM suture did not occur later than and the initial stages of continent–continent collisions requires Middle Triassic (Bian et al., 2004; Elena et al., 2003). an improved understanding of the age, nature, and distribution of The Jinshajiang suture separates the HXSG complex from the magmatism in the HXSG terrane. To improve our understanding of the Qiangtang terrane to the south (Dewey et al., 1988). The basement of closure of the Paleo-Tethys ocean, we have analyzed samples from the Qiangtang terrane is likely composed of Cambro-Ordovician gneiss plutons which intruded into the turbidite deposits and generated zircon and siliciclastic metasedimentary mélange (Kapp et al., 2003; Li et al., U–Pb ages and muscovite 40Ar/39Ar ages. Whole-rock major and trace 1995; Xu et al., 1985). The Qiangtang terrane was part of Gondwana element abundances as well as the Sr–Nd–Hf isotopic compositions until Permian time when it began drifting northward across the Paleo- were determined to better define the magma sources and their tectonic Tethys towards Eurasia (Stampfli and Borel, 1992; Xu et al., 1985). The implications. Ganzi-Litang suture separates the eastern HXSG complex from the Yindun arc to the southwest. The Yidun arc is a micro-continent 2. Geological setting and sample description composed of Paleozoic carbonates and mafic volcanic rocks, Triassic mudstone and shale, and calc-alkaline granitoids and volcanic rocks 2.1. Geological setting (Fig. 1, Chen et al., 1987; Hou et al., 2007; Reid et al., 2007; Wang et al., 2011a). The Anyimaqin–Kunlun–Muztagh (AKM) suture separates the HXSG The northeast striking Longmen Shan thrust belt defines the eastern complex from the Kunlun arc terrane and Qaidam basin to the north limit of the HXSG complex (Fig. 1). Neoproterozoic basement rocks (Fig. 1). However, in the area of the West Qinling between the eastern similar to those of South China crop out along the Longmen Shan thrust Kunlun and Qinling-Dabie orogen, the AKM suture is widely inferred fault (Yan et al., 2003; Zhou et al., 2002, 2006). Here the Middle–Upper (e.g. Meng et al., 2005). The Kunlun arc is formed during closure of the Triassic HXSG turbidites are exposed atop the Yangtze platform rocks of Paleo-Tethys Ocean basin (Harris et al., 1988; Yang et al., 1996). The the South China block (Burchfiel et al., 1995). Adakitic and I-type eastern Kunlun terrane, north of our study area, is composed of 260– granitoids in the range of 228–197 Ma were reported in the hinterland 330 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 of the Longmen Shan thrust belt in the eastern HXSG complex (Hu et al., fourth unknown analysis to monitor instrument fractionation and 2005; Roger et al., 2004; Xiao et al., 2007; Yuan et al., 2010; Zhang et al., drift. Common lead corrections were estimated from the 204Pb counts 2006). Adakitic rocks show strongly fractionated REE patterns ((La/ (Stacey and Kramers, 1975) and the data were processed using

Yb)N =105–20) (Xiao et al., 2007; Yuan et al., 2010; Zhang et al., ISOPLOT (Ludwig, 2003). Uncertainties are reported at the ±1σ level. 2006), whereas I-type plutons yield more moderately fractionated REE The data are listed in Supplementary Table 1. patterns ((La/Yb)N b 20) (Hu et al., 2005; Xiao et al., 2007). Genesis of In-situ zircon U–Pb and Hf isotopic analyses were done using the adakitic magmas has been attributed to partial melting of thickened a Neptune MC-ICPMS and Agilent 7500a Q-ICPMS coupled with lower continental crust (South China) (Xiao et al., 2007; Yuan et al., a 193 nm laser at the Institute of Geology and Geophysics, Chinese 2010; Zhang et al., 2006, 2008b) or Paleo-Tethys subducted oceanic Academy Sciences (IGGCAS). Analytical methods and procedure follow slab (e.g. Zhang et al., 2008a). The 211 Ma A-type granite intrudes the Wu et al. (2006) and Xie et al. (2008). The TEMORA and 91500 zircon eastern HXSG complex and is interpreted to be post-collisional (Zhang standards were analyzed along with zircon crystals of unknown U–Pb et al., 2007). Based on Sr, Nd and Pb isotopic data, these rocks are age and Hf composition from our samples. TEMORA yielded a weighted thought to correlate with magmas sourced from a continental peninsula mean 176Hf/177Hf ratio of 0.282674 ± 0.000005, whereas 91500 yielded that extended into the Paleo-Tethys Ocean and was located along a ratio of 0.282305 ± 0.000004 for the Hf session. The 176Hf/177Hf ratios the western margins of the South China Block (Zhang et al., for both natural zircon standards were in good agreement with pub- 2006). In addition, the high Ba–Sr or shoshonitic granites from lished data (Black et al., 2003; Wu et al., 2006). The εHf(t) values and C two plutons (215 and 205 Ma) were reported and thought to two stage mantle depleted model ages (TDM) were calculated after have been derived from the low-degree melting of mantle in Griffin et al. (2000) using the 176Lu decay constant given in Blichert- response to fracturing and detachment of mantle lithosphere Toft and Albarede (1997). The results are given in Supplementary (Yuan et al., 2010). Tables 2 and 3. Deformation of the HXSG complex occurred during the Late Triassic– Muscovite grains were separated using conventional methods Early Jurassic continent–continent collision overlapping significant and purified by hand-picking under a binocular microscope. Mineral shortening along the Longmen Shan thrust belt (Roger et al., 2010; Xu separates for 40Ar/39Ar analysis were irradiated for 7.96 h with a et al., 1992; Yin and Harrison, 2000). Where this episode of deformation neutron dose of 1.86 × 1017 ncm−2 in the Beijing Nuclear Research has been studied in the eastern HXSG complex, it is generally character- Institute Reactor along with Fish Canyon Tuff sanidine crystals ized by tightly folded strata with vertical/sub-vertical NW–SE striking (27.8 Ma; Renne et al., 1994), and K2SO4 and CaF2 salts to monitor axial planes (Burchfiel et al., 1995; Roger et al., 2004; Xu et al., 1992). neutron flux. All samples were analyzed at the Institute of Tibetan The timing of this deformation is constrained by the emplacement Plateau Research (CAS) and were step-heated from 750 to 1450 °C. of syn- and post-kinematic granites at ~197 Ma and ~195–188 Ma, The released gas was purified with a Ti sponge and Zr–Al getters and respectively (Roger et al., 2004). then conducted on a Helix Mass spectrometer. Age calculations were Compared to the eastern margin of the HXSG complex, geologic made using the decay constants of Steiger and Jäger (1977),theformu- evolution of western HXSG area is still poorly known. The western lae of Dazé et al. (2003) and plotted using ISOPLOT (Ludwig, 2003). HXSG is located between the AKM suture and Jingshajiang suture Uncertainties in the data are reported at the ±1σ level. The data are (Fig. 1). The strongly folded Triassic turbidites were uncomfortably listed in Supplementary Table 4. covered by local Middle Jurassic strata in the western HXSG (Ding Major and trace element and Sr–Nd isotopic analyses were et al., 2013). Few studies reported that the ages of igneous rocks in the conducted at the IGGCAS. Samples for elemental and isotopic analy- Hoh-Xil area range from 217 Ma to 202 Ma (Roger et al., 2003; Liu sis were powdered to b20 μm using an agate mill. Major element et al., 2006; Lü et al., 2006; Wang et al., 2011b). These magmatic rocks abundances (wt.%) were determined on whole-rock samples by may have been derived from deep melting of the Paleozoic accretionary a Phillips PW X-ray fluorescence spectrometer (XFR-2400) and wedge complex (Bian et al., 2004; Schwab et al., 2004)orthey yielded analytical uncertainty b 5% (±1σ). Rare earth element may represent the southern extension of the Kunlun arc (or Kunlun (REE) and trace element concentrations were determined by a VG- fore-arc) (Roger et al., 2003; Wang et al., 2011b). PQ Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Uncertainties, calculated by repeated analyses of internal standards, 2.2. Sample petrography are ±5% for REE and ±5–10% for trace elements. The results are given in Supplementary Table 5. Samples from this study are from the Hoh-Xil area (i.e., western Prior to Rb–Sr and Sm–Nd whole-rock isotopic analysis, sample HXSG complex) and include stocks and plutons from the Zhuonai powders were spiked with 87Rb, 84Sr, 147Sm and 150Nd tracers and dis-

Lake, Malanshan, Daheishan, Hudongliang, Changhong Lake, Dapeng solved in Teflon bombs with HF and HNO3 at 170 °C for 168 h. Rb, Sr, Lake, Yunwuling and Heishibei Lake areas (Figs. 1 and 2). These Sm and Nd were separated by conventional ion exchange techniques volumetrically small felsic igneous rocks intrude into the Middle– and analyzed with a Finnigan Mat 262 multicollector mass spectrometer. Upper Triassic marine strata. Neither metasedimentary xenoliths nor Data for Rb, Sr, and Sm were collected using a static acquisition mode mafic enclaves were observed during our investigations. Detailed geo- whereas Nd data were collected using a dynamic multiple mass collection logic and petrologic descriptions of these plutons can be found in routine (Li et al., 2007a). Total blanks were b500 pg for Rb and Sr Table 1. and b100 pg for Sm and Nd. Sr isotope ratios were normalized to 86Sr/87Sr = 0.1194 and Nd isotope ratios to 146Nd/144Nd = 0.7219. 3. Analytical methods Three measurements of standard samples (NBS987 and La Jolla) yielded a mean value of 87Sr/86Sr = 0.710269 ± 0.000009 and Zircon crystals were separated using conventional heavy liquid and 143Nd/144Nd = 0.512115 ± 0.000011. The data are listed in magnetic techniques, mounted along with an external zircon standard Supplementary Table 5. (TEMORA, Black et al., 2003) in epoxy, polished and vacuum-coated with a 50 nm layer of carbon. Zircons were examined in transmitted 4. Results and reflected light, and cathodoluminescence (CL) images. Zircon U– Pb analyses were conducted using the sensitive high-resolution ion 4.1. Zircon geochronology and Hf isotopes microprobe (SHRIMP) at Institute of Geology, Chinese Academy of Geological Sciences and following the methodology of Williams Seven samples for zircon U–Pb geochronology yielded Late Triassic (1998). The standard zircons (TEMORA) were analyzed after every ages and one sample yielded Early Jurassic ages (Fig. 2). Most samples L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 331

Fig. 2. Simplified geologic maps for granitoid plutons from the Hoh-Xil area, western HXSG complex: (a) Malanshan and Hudongliang plutons; (b) Zhuonai Lake and Daheishan plutons; (c) Heishibei Lake plutons; and (d) Yunwuling, Dapeng Lake and Changhong Lake plutons.

yielded some older inherited ages (Supplementary Table 1 and 2). 4.1.1. Zhuonai Lake pluton Zoning consistent with these inherited cores can be observed in Zircon crystals from sample 2006K006 (Fig. 2b) are colorless and cathodoluminescence (CL) images (Fig. 3). show oscillatory zoning typical of igneous crystallization in CL images 332 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348

Table 1 Sample description of granitoids in the western HXSG complex, northern Tibet.

Pluton GPS Lithology Texture Mineral assemblage Ages (Ma) εHf(t)

Dapeng Lake N36°35.578′ Granodiorite Granitic Q(10–15) + Hb(15–20)+Pl(50–55) + Kfs(10–15) 213 ± 6† −3.3–−0.8 E86°38.135′ Changhong Lake N36°11.450′ Granite Fine-grain, porphyritic Q(20–30) + Pl(50–55)+Kfs(10–15) + Bi(5–10) 212 ± 6† −4.0–−1.1 E85°59.066′ Heishibei Lake N35°33.676′ Granite Granitic Q(25) + Kfs(35–40)+Pl(25–30) + Bi(5–10) 221 ± 1† −7.8–−1.8 E82°49.523′ Daheishan N35°29.567′ Granodiorite Granitic Q(15–20) + Hb(15–25)+Pl(20–35) + Kfs(15–20) 202 ± 1† E92°07.783′ Yunwuling N36°35.578′ Granite Granitic Q(25–30) + Kfs(40–45)+Pl(10–15) + Bi(1–5) 193 ± 10† −0.6–+3.0 E86°38.135′ Zhuonai Lake N35°26.347′ Granite Fine-grain, porphyritic Q(5–10) + Kfs(b5) + Pl(b5)+Ms(b2) + groundmass(70–80) 212 ± 4‡ E92°58.305′ 212.7 ± 2.5* Malanshan N35°47.819′ Granite Fine-grain, porphyritic Q(5–10) + Kfs(5–8) + Pl(b5)+Ms(b2) + groundmass(75–80) 213 ± 2‡ E90°52.610′ Hudongliang N35°51.345′ Granite Fine-grain, porphyritic Q(5–10) + Kfs(0–5) + Pl(5–10)+Ms(b2) + groundmass(75–80) 225 ± 3‡ E90°24.137′ 210.7 ± 2.5*

Note: Q = quartz; Pl = plagioclase; Kfs = K-feldspar; Bi = biotite; Ms = muscovite; Hb = Hornblende. The symbols † and ‡ denote zircon U–Pb dating by LA-ICP-MS and SHRIMP, respectively. Age uncertainty is at 2σ. The symbol * denotes 40Ar/39Ar dating by HELIX.

(Fig. 3a). Zircon crystals used for U–Pb analysis range from ~60–120 μm This sample yields εHf(t) values ranging from −4.0 to −1.1 (Fig. 3e) 206 C in length and length/width ratios are between 1.5:1 and 1:1. The Pb/ and T DM values ranging from 1.1 to 1.5 Ga (Supplementary Table 3). 238U ages that were generated range from 201 to 2165 Ma, however three concordant analyses ranging from 209 to 214 Ma yield a weighted 4.1.6. Dapeng Lake pluton σ mean age of 212 ± 4 Ma (2 ) with MSWD = 0.69 (Fig. 4a). The Zircon crystals separated from the Dapeng Lake pluton (2007 K361, weighted mean age is interpreted to most closely date the crystalliza- Fig. 2d) yield 206Pb/238U ages ranging from 204 to 822 Ma with a tion age of 2006K006. weighted mean age of 214 ± 7 Ma (MSWD = 2.2, Fig. 5c) when ages from inherited cores are excluded (Fig. 3g). Inherited zircon core 4.1.2. Malanshan pluton 206Pb/238U ages range from 247 to 822 Ma (Fig. 5c). Analyses yielding Zircon crystals of sample 2006K096 (Fig. 2a) are colorless, euhedral Triassic ages have low Th/U ratios (0.01–0.08). Analyses with U–Pb and exhibit oscillatory zoning in CL images (Fig. 3b). These crystals are ages clustering around 214 Ma have εHf(t) values ranging from −3.3 C typically ~150–260 μm in length with length/width ratios between to −0.8 (Fig. 3g) and T DM values ranging from 1.0 to 1.2 Ga (in 1.2:1 and 1:1. Ten concordant analyses form a cluster with a weighted Supplementary Table 3). mean 206Pb/238U age of 213 ± 2 Ma (MSWD = 0.42), interpreted as the crystallization age of this granite (Fig. 4b). 4.1.7. Yunwuling pluton Zircon grains from Yunwuling Lake pluton (2007 K351, Fig. 2d) yield 4.1.3. Hudongliang pluton 206Pb/238U ages ranging from 172 to 214 Ma and a weighted mean Zircon crystals from sample 2006K201 (Fig. 2a) show dark rims and age of 193 ± 10 Ma for 8 zircons (MSWD = 17, Fig. 5d). Zircons are light inner cores in CL images (Fig. 3c), which are typical for xenocrystic 150–250 μm in length and have length/width ratios between 3:1 and core with high-U (up to 4842 ppm) overgrown rims. Analysis of rims 1:1. Analyses clustering around the mean age yield εHf(t) values 206 238 C yields Pb/ U ages that ranged from 206.3 to 231.4 Ma with a ranging from −0.6 to +3 (Fig. 3h) and T DM values ranging from 0.86 weighted mean age of 225 ± 3 Ma (MSWD = 1.9, Fig. 4c). The age of to 1.08 Ga (Supplementary Table 3). 225 Ma is interpreted to approximate the crystallization of this granite. 206 238 Analysis of three cores yields Pb/ U ages of 648 ± 13, 279.1 ± 7.7 4.1.8. Heishibei Lake pluton and 246.4 ± 5.3 Ma, which may have been inherited zircons from Zircon crystals from the Heishibei Lake pluton (2007 K419, Fig. 2d) magma source(s). yield 206Pb/238U ages ranging from 214 to1544 Ma (Fig. 5e) and a weighted mean age of 221 ± 1 Ma for 14 grain rims (MSWD = 1.7, 4.1.4. Daheishan pluton Fig. 5f). Zircons are 150–250 μm in length and have length/width ratios Zircon grains from sample 2006 K016 (Fig. 2b) are colorless and between 5:1 and 1:1 (Fig. 3h). Analyses clustering around the mean age C euhedral and exhibit oscillatory zoning in CL images (Fig. 3d). These yield εHf(t) values ranging from −5.7 to −1.5 (Fig. 3h) and T DM values grains are 100–250 μm in length and have length/width ratios between ranging from 1.15 to 1.61 Ga (Supplementary Table 3). 3:1 and 1:1. These crystals yield Th/U ratios ranging from 0.20 to 0.60. 206 238 Pb/ U ages of 20 analyses ranging from 198 to 211 Ma with a 4.2. 40Ar/39Ar dating results weighted mean age of 202 ± 1 Ma (MSWD = 5.5, Fig. 5a), which is interpreted as the crystallization age for this pluton. Muscovite grains separated from stocks in the Zhuonai Lake and Hudongliang study areas were analyzed using 40Ar/39Ar 4.1.5. Changhong Lake pluton thermochronology to better understand the post-emplacement Zircon crystals separated from the Changhong Lake pluton thermal evolution of these igneous bodies. Muscovite grains from the (2007 K249, Fig. 2d) yielded 206Pb/238U ages that range from 186 to Zhuonai Lake pluton (2006 K006) yield a plateau age 212.7 ± 5.1 Ma 273 Ma. These crystals are 150–250 μm in length and have length/ (MSWD = 0.43, Fig. 6a), which is within error of the U–Pb zircon age width ratios between 3:1 and 1:1 (Fig. 3e). Zircon analyses yield high from the same sample (212 ± 4 Ma). Muscovite grains sampled from Th/U ratios ranging from 0.24 to 0.97. If the two youngest analyses are the Hudongliang stock (2006 K201) yield a 40Ar/39Ar plateau age of excluded based on Pb loss evidenced by U concentrations N800 ppm 210.7 ± 2.5 Ma (MSWD = 0.52, Fig. 6b), somewhat younger than the whereas older inherited cores are excluded, eight spot analyses yield a U–Pb zircon age from this sample (225 ± 3 Ma). Overlapping 40Ar/ weighted mean 206Pb/238U age of 212 ± 6 Ma (MSWD = 3.4, Fig. 5b). 39Ar and U–Pb ages and the porphyritic texture of these two samples L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 333

Fig. 3. Cathodoluminescence (CL) images of zircons from (a) 2006K006, (b) 2006K096, (c) 2006K201, (c) 2006k016, (e) 2007K249, (f) 2007K351, (g) 2007K361 and (h) 2007K419 samples, showing U–Pb isotope ages and εHf(t) values.

suggest that they were emplaced at relatively shallow crustal levels show that most rocks are high-K calc-alkaline (Fig. 7a) and plot in the (i.e. b5 km) and remained at relatively shallow levels since intrusion. fields of granite and granodiorite (Fig. 7b).

4.3.1. Dapeng Lake pluton 4.3. Whole rock geochemistry The Dapeng Lake granodiorites display a narrow range of chemi-

cal compositions, with relatively low SiO2 (61.33–62.82%) and high Granitoid samples were analyzed for whole-rock geochemistry to Al2O3 (16.30–17.33%), Fe2O3 (5.16–5.92%) and CaO (3.51–4.16%). better understand the magma genesis and the nature of the basement They have high Na2O/K2Oratios(N1), with K2O = 2.23–2.83% beneath the HXSG turbidites during Triassic time. Geochemical results (Fig. 7a) and Na2O = 3.51–4.13%, and with the total K2O+Na2O 334 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348

87 86 87 86 ranging from 6.02% to 6.65%. These samples are metaluminous to high initial Sr/ Sr compositions ( Sr/ Sri = 0.7084) and low slightly peraluminous, with A/CNK from 0.97 to 1.06 (Fig. 7c). The εNd(t) values (−5.2) with TDM = 1.25 Ga (Supplementary Table 5). granodiorites exhibit low MgO (1.65–2.18%) and Mg# (40–44). The Dapeng Lake rocks contain low Cr (7.0–21.9 ppm), Co (5.1– 4.3.2. Changhong Lake pluton 8.9 ppm) and Ni (4.1–11.8 ppm). In addition, the Dapeng Lake The Changhong Lake samples have high loss on ignition (LOI: 7.53– granodiorites that are characterized by highly fractionated rare 9.83%), probably due to high degrees of alteration (e.g. Wang et al., earth elements (REEs, (La/Yb)N =25–16), show no Eu anomalies 2011b). Their large ion lithophile elements (LILE, e.g. Ba) increase (Eu/Eu* = 0.93–0.87) and are significantly depleted in high field with increasing LOI, indicating that their abundances have been strength elements (HFSEs) such as Nb, Ta and Ti (Fig. 8a,b). They display changed by alteration (Supplementary Table 5). The Sr contents show high Sr (782–282 ppm, most N400 ppm) but low Y (12.9–16.0 ppm), no obvious trend with increasing LOI. Also, the MgO, Fe2O3,TiO2,P2O5 yielding high Sr/Y ratios (59–23, Fig. 9). The sample 2006K361 exhibits and transition, rare earth and high field strength elements exhibit no evident variation with increasing LOI (Supplementary Table 5), indicating that their contents probably have not been modified significantly by alteration. Thus, these elements are mainly used in the following discus- sion. The Changhong Lake rocks exhibit low MgO (1.10–1.55%) and Mg# (50–54) rocks. These samples show highly fractionated REE patterns

((La/Yb)N =91–62), no Eu anomalies (Eu/Eu* = 0.97–1.02) and negative Nb, Ta and Ti anomalies in multi-element diagram (Fig. 8c,d). The granites have low Cr (5.5–10.2 ppm), Co (1.8–2.7 ppm) and Ni (1.9–3.8 ppm) abundances. They display high Sr (526–240 ppm, most N 400 ppm) but low Y (6.3–6.9 ppm), yielding high Sr/Y ratios (84–38, Fig. 9). The samples exhibit high initial 87Sr/86Sr composi- 87 86 tions ( Sr/ Sri = 0.7079) and low εNd(t) values (− 5.3–− 4.7) with TDM =1.18–1.22 Ga (Supplementary Table 5).

4.3.3. Heishibei Lake pluton The Heishibei Lake granites have a narrow range of chemical

compositions, with high SiO2 (66.32–68.63%) and Al2O3 (15.61–16.03%), but low Fe2O3 (2.61–3.48%), MgO (1.13–1.35%) and CaO (1.73–2.30%). They are relatively high in alkalis, with K2O = 3.70–4.07% (Fig. 7a) and Na2O = 3.41–4.02%, and with K2O+Na2O ranging from 7.22% to 7.86%. These samples are peraluminous rocks with A/CNK from 1.07 to 1.20 (Fig. 7c). They exhibit low MgO (1.13–1.35%) and Mg# (30–51). The chondrite-normalized REE patterns of the Heishibei Lake granites are relatively uniform and show relatively high HREE/

LREE ratios ((La/Yb)N =25–19) and slightly negative Eu anomalies (Eu/Eu* = 0.73–0.68) and are significantly depleted in HFSEs such as Nb, Ta and Ti (Fig. 8e,f). They display high Sr (578–235 ppm) but low Y (11.4–13.0 ppm), yielding relatively high Sr/Y ratios (44–20, Fig. 9). The samples exhibit high initial Sr compositions 87 86 ( Sr/ Sri = 0.7086–0.7090) and low εNd(t)values(−7.7–−7.3) with TDM =1.51–1.57 Ga (Supplementary Table 5).

4.3.4. Daheishan pluton Samples from the Daheishan pluton are high-K calc-alkaline (Fig. 7a) and plotted in granodiorite field (Fig. 7b). They have high

SiO2 (62.18–64.08%), Al2O3 (15.39–16.45%) and CaO (3.67–4.85%), but low MgO (1.96–2.22%, Mg# = 45–48) contents. All rocks are metaluminous to weakly peraluminous (A/CNK = 0.87–1.02, Fig. 7c) and hornblende-bearing rocks, similar to I-type granites (Chappell and White, 1992). The chondrite-normalized REE patterns (Fig. 8g) ex-

hibit low LREE/HREE ratios ((La/Yb)N =3–18) with slightly negative Eu anomalies (Eu/Eu* = 0.72–0.91). They exhibit relatively moderate Sr (306–549 ppm) but high HREE and Y (22.3–15.3 ppm) abundances, yielding low Sr/Y ratios (14–36, Fig. 9). They are enriched in Rb, U, and Th but significantly depleted in Nb, Ta, Sr, Eu, and Ti in the multi- element diagram (Fig. 8h). Rocks show high initial 87Sr/86Sr and 87 86 low εNd(t) isotope compositions ( Sr/ Sri = 0.7112–0.7143; εNd(t) = −6.0–−4.9) with TDM =1.32–1.54 Ga (Supplementary Table 5).

4.3.5. Yunwuling pluton The Yunwuling samples are high-K calc-alkaline rocks (Fig. 7a) with

high variable SiO2 (69.13–74.72%) and alkalis (Na2O+K2O = 7.59– – – – Fig. 4. SHRIMP zircon U–Pb concordia diagrams for the (a) Zhuonai Lake, (b) Manlanshan 9.27%) but low MgO (0.36 0.64%, Mg# = 23 32), CaO (0.98 1.56%) and (c) Hudongliang plutons in the Hoh-Xil area, western HXSG complex. and P2O5 (0.07–0.17%). These samples are metaluminous to weakly L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 335

Fig. 5. LA-ICP-MS zircon U–Pb ages for the (a) Daheishan, (b) Changhong Lake, (c) Dapeng Lake, (d) Yunwuling, and (e) Heishibei Lake plutons in the Hoh-Xil area, western HXSG complex. peraluminous rocks with A/CNK = 0.93–1.11 (Fig. 7c). The chondrite- high Rb (143–165 ppm) and very low Sr abundances (21–44 ppm), of normalized REE patterns of the Yunwuling granites show low LREE/ highly evolved magmas. The granites show relatively high initial 87Sr/ 86 87 86 HREE ratios ((La/Yb)N =5–17) and significant variable negative Sr compositions ( Sr/ Sri =0.7077–0.7082) and low εNd(t) values Eu anomalies (Eu/Eu* = 0.02–0.72)(Fig. 8i). They are enriched in Rb, U, (−5.4–−5.2) with TDM = 1.41–1.43 Ga (Supplementary Table 5). and Th but significantly depleted in Nb, Sr, Eu, and Ti (Fig. 8g). They dis- play variable low Sr (68–187 ppm) but high Y (26.5–15.6 ppm) composi- 4.3.7. Hudongliang pluton tions, which yield low Sr/Y ratios (1–10, Fig. 9). The samples yielded initial The Hudongliang granites have high SiO2 (71.02–75.07%) and Al2O3 87 86 87 86 Sr/ Sr compositions ( Sr/ Sri = 0.7072–0.7084) and εNd(t) values (13.93–15.11%), and low Fe2O3 (1.40–2.56%), CaO (0.28–2.07%) and (−2.3–−2.0) with TDM =1.14–1.16 Ga (Supplementary Table 5). P2O5 (0.05–0.35%). They show moderately high Na2O/K2Oratios(N1), with K2O = 2.30–2.82% (Fig. 7a) and Na2O = 2.64–3.83%, and with 4.3.6. Malanshan pluton K2O+Na2O ranging from 5.05% to 6.06%. These samples are The Malanshan granites have extremely high SiO2 (77.30–80.08%) peraluminous (Fig. 7c) and exhibit low MgO (0.24–0.84%) and Mg# and low Fe2O3 (0.23–1.55%), MgO (0.09–0.16%), CaO (0.07–0.12%) (25–50). They show intermediate LREE/HREE ratios ((La/Yb)N = 22.5). and P2O5 (0.02–0.04%). These samples are relatively high in K2O They are enriched in Rb, U, and Th but significantly depleted in Nb, Sr, (3.62–4.21%, Fig. 7a) and are peraluminous (Fig. 7c). The granites are Eu, and Ti (Fig. 8m, n). They show high Rb (693 ppm) but low Sr enriched in LREEs ((La/Yb)N =21–38), with significant negative Eu (132 ppm) concentrations, typical of highly evolved magmas. The 87 86 87 86 anomalies (Eu/Eu* = 0.18–0.24; Fig. 8k). They are enriched in Rb, U, samples exhibit high initial Sr/ Sr compositions ( Sr/ Sri = 0.7072– and Th but significantly depleted in Nb, Ta, Sr, Eu, and Ti in the primitive 0.7095) and low εNd(t)values(−7.1–−6.1) with TDM =1.35–1.40 Ga mantle-normalized multi-element diagram (Fig. 8l). The samples have (Supplementary Table 5). 336 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348

Fig. 6. Muscovite 40Ar/39Ar age spectra diagrams for the (a) Zhuonai Lake and (b) Hudongliang plutons in the Hoh-Xil area, western HXSG complex.

4.3.8. Zhuonai Lake pluton The Zhuonai Lake granite samples have a narrow range of chemical compositions, with high SiO2 (72.45–75.37%) and Al2O3 (13.56–15.23%), and low Fe2O3 (0.87–0.76%), MgO (0.06–0.65%), CaO (0.18–1.09%) and P2O5 (0.04%). These rocks are relatively high in alkalis with K2O = 3.70–4.34% (Fig. 7a) and Na2O = 3.59–4.57%, and with K2O+ Na2O ranging from 7.54% to 8.20%. They are peraluminous (A/ CNK = 1.16–1.33) rocks (Fig. 7c) and plot in the field of granite in the

An–Or−Ab diagram (Fig. 7b). Chondrite-normalized REE patterns of Fig. 7. (a) K2O vs. SiO2 (after Peccerillo and Taylor, 1976); (b) An–Ab–Or (after Barker, Zhuonai Lake granites are relatively uniform (Fig. 8o), showing significant 1979); (c) A/NK vs. A/CNK plots for the Hoh-Xil granitoids. negative Eu anomalies (Eu/Eu* = 0.02–0.04) and high LREE/HREE ratios

((La/Yb)N =21–38). These rocks are enriched in Rb, U, and Th but Zhuonai Lake plutons plot in typical arc magmas field. Here we significantly depleted in Nb, Ta, Sr, Eu, and Ti in the primitive mantle- subdivide these plutons into adakitic (Group 1) and non-adakitic normalized multi-element diagram (Fig. 8p). They exhibit high Rb (Group 2) assemblages for further discussion. (264–225 ppm) abundances but very low Sr abundances (14–29 ppm), typical of highly evolved magmas. The granites show high initial 87Sr/ 5.1.1. Group 1 adakites (221–212 Ma) 86 87 86 Sr compositions ( Sr/ Sri = 0.7085–0.7104) and low εNd(t) values Samples from the Dapeng Lake, Changhong Lake and Heishibei Lake (−6.6–−6.5) with TDM =1.55–1.56 Ga (Supplementary Table 5). plutons are high-K calc-alkaline rocks, showing strongly depleted heavy REE patterns (Yb = 0.41–1.54 ppm, Y = 6.3–16 ppm), small to absent 5. Discussion Eu anomalies (Fig. 8a, c, e) and high Sr/Y ratios (Fig. 9). These character- istics are with affinity to adakites (Defant and Drummond, 1990). The 5.1. Petrogenesis depleted HREE and Y of Group 1 suggest the presence of garnet in the residue (Defant and Drummond, 1990; Rapp and Watson, 1995). In ad- All plutons studied here lack significant deformation at the outcrop dition, the relatively flat HREE patterns suggest that amphibole was to thin section scale, and intrude Middle–Upper Triassic strata. Samples dominant rather than garnet in the residue (Huang and He, 2010; from the Dapeng Lake, Changhong Lake and Heishibei Lake plutons have Moyen, 2009). The absence of significant Eu anomalies and high Sr con- adakitic affinities based on Sr/Y vs. Y diagram (Fig. 9) whereas the centration suggests that plagioclase was not an abundant phase in the rocks from the Daheishan, Yunwuling, Malshanshan, Hudongliang and residue. The strong depletion of Nb, Ta and Ti in the group 1 suggests L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 337 that the source has residual amphibole and/or rutile (Mahoney et al., in deep sources (N15 kb) will significantly increase Nb/Ta ratios in the 1998). Both Nb and Ta tend to be hosted in amphibole, being at equilib- melts (e.g. Xiong et al., 2005). The low Nb/Ta ratios (10–17) of Group rium with intermediate to acidic melts during anatexis (Pearce and 1 indicate a rutile-free but amphibole dominant source in the residue. Norry, 1979). However, Nb/Ta ratios seem to be hardly affected by Thus partial melting occurred below 15 kb at a depth of b50 km amphibole fractionation whereas rutile as a necessary residual phase (Fig. 11a). Adakitic melts can be generated after a range of pressures

Fig. 8. Chondrite-normalized REE patterns and primitive mantle-normalized trace element diagrams for the Hoh-Xil granitoids. (a, b): Dapeng Lake pluton (c, d) Chonghong Lake Pluton; (e, f) Heishibei Lake pluton; (g, h) Daheishan pluton; (i, j) Yunwuling pluton; (k, l) Malanshan pluton; (m, n) Hudongliang pluton and (o, p) Zhuonai Lake pluton. Chondrite-normalization data are from Boynton (1984). Primitive mantle-normalized data are from Sun and McDonough (1989). 338 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348

Fig. 8 (continued). from 10 to 20–25 kb or more (e.g. Moyen, 2009). Thus, partial melting Qu et al., 2004); (2) fractional crystallization of basaltic magmas depth for Group 1 rocks was likely between 10 and 15 kb, implying a (e.g. Castillo et al., 1999; Li et al., 2009; Macpherson et al., 2006); (3) source dominated by garnet amphibolite (Fig. 11b). The (La/Yb)N ratios partial melting of delaminated lower continental crust (Gao et al., imply that the Dapeng Lake and Heishibei Lake residues may have 2004; Wang et al., 2006, 2007; Xu et al., 2002); or (4) partial melting contained ~5% garnet whereas the Changhong Lake rocks had ~25% of a thickened lower continental crust (e.g. Atherton and Petford, garnet in the residue (Fig. 11b). 1993; Chung et al., 2003; Condie, 2005; Hou et al., 2004; Petford and Adakitic magmas may be produced through: (1) partial melting of Atherton, 1996; Wang et al., 2005; Xiao and Clemens, 2007). a subducted or stalled oceanic slab (e.g. Defant and Drummond, Basaltic magmatism has not been reported in the western HXSG 1990; Pe-piper and Piper, 1994; Defant et al., 2002; Mungall, 2002; during Middle Triassic–Early Jurassic time. It is therefore difficult to L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 339

plot close to the global sediments and far from the MORB field (Fig. 12b). Besides, melts from metasediments mixed with pure adakitic melts may make the Group 1 rocks close to the continental crust-derived adakites (Fig. 11e and f) and lowered MgO and Mg# components (Fig. 11c and d) since the marine sediments have continental affinity (Plank and Langmuir, 1998). Collectively, our data favor the possibility that the Group 1 adakites were derived from melting of the oceanic slab including both basalts and metasediments. Here, we propose that retreating subduction and melting of ocean slab during rollback of the Paleo-Tethys ocean lithosphere produced the Group 1 adakites.

5.1.2. Group 2 non-adakites (225–193 Ma)

In Group 2 non-adakites, the P2O5 compositions decrease with increasing SiO2, which is similar to the trend for I-type granites (Fig. 13a). The Daheishan rocks are amphibole-bearing and metaluminous to slightly peraluminous, typical of I-type granites

(Chappell and White, 1992). Their relatively high P2O5,Al2O3 and CaO compositions but low FeO*/MgO ratios indicate that these rocks Fig. 9. Sr/Y vs. Y diagram modified after Defant and Drummond (1990). are the least evolved magmas in Group 2 (Fig. 13a–d). Other rocks from the Yunwuling, Malshanshan, Hudongliang and Zhuonai Lake

plutons are silica-rich (SiO2 =69–80%), amphibole-free and exhibit high contents of alkalis. Their SiO2 compositions increase with decreas- argue directly for the derivation of the Group 1 rocks through high- ing P2O5, CaO and Al2O3 (Fig. 13a–c) and they exhibit high FeO*/MgO pressure fractional crystallization of basaltic magmas during magma ratios (Fig. 13d–e). These features suggest that these rocks experienced ascent (e.g. Castillo et al., 1999; Li et al., 2009; Macpherson et al., significant magmatic differentiation (Whalen et al., 1987). These rocks 87 86 2006). However, the high initial Sr/ Sri and negative εNd(t) compo- show enrichment in LREEs and significant negative Eu anomalies. All sitions of Group 1 (Fig. 10a) preclude the possibility that they were rocks invariably are depleted in Nb, Ta, Sr, Eu, and Ti but enriched in generated by melting of the mantle or fractional crystallization of Rb, K, Th and U (Fig. 8g–p). These features are consistent with the highly mantle-derived basalts. fractionated I-type granites in northeastern and southern China (Jahn The Late Triassic adakites in the eastern HXSG are proposed to have et al., 2001; Li et al., 2007b; Wu et al., 2003). In addition, most of been derived from melting of thickened mafic lower continental crust these samples plot in the highly fractionated calc-alkaline granitic (Xiao et al., 2007; Zhang et al., 2006). Adakitic melts from a lower field whereas the Daheishan rocks plot in the unfractionated M–I–S- mafic continental crust tend to be enriched in K and are distinguished granite field (Fig. 13d–e). by significantly higher compositions of strongly incompatible elements, Previous studies suggested that I-type granites are generated through such as Rb, Ba, Th and U than LREE (Chung et al., 2003; Hou et al., 2004; partial melting of intracrustal metamorphosed mafic to intermediate Wang et al., 2005; Xu et al., 2002). High Th and Th/La ratios of Group 1 igneous rocks (Chappell and Stephens, 1988). Melting of intermediate adakitic rocks are consistent with derivation from the lower continental igneous rocks such as quartz diorites yields strongly peraluminous crust and inconsistent with an origin by melting of the oceanic basalts melts (Patiño Douce, 1999), in contrast to the least evolved (SiO2 = (Fig. 11e, f). In addition, compared with experimental melts from 62–64%) and metaluminous granodiorites of the Daheishan pluton basalts and amphibolites, Group 1 rocks have low MgO and Mg# (Fig. 7b). The melting of metabasaltic sources at high temperatures is (Fig. 11c, d) as well as Cr (5.5–21.9 ppm) and Ni (1.9–15.7 ppm), capable of producing metaluminous melts (Rapp et al., 1991), but low fl re ecting no interaction between adakitic melts and mantle peridotite K2O basaltic source rocks would be unsuitable for the high-K2O (Stern and Kilian, 1996). Thus it seems unlikely that these rocks Daheishan rocks (Rapp et al., 1991; Roberts and Clemens, 1993). Thus, originated by melting a delaminated lower crust (Wang et al., 2006, melts of basaltic amphibolites tend to resemble high-K calc-alkaline 2007; Xu et al., 2002). Thus, Group 1 rocks seem to have been derived Daheishan granodiorites (Sen and Dunn, 1994). Significant negative Eu from a thickened continental mafic lower crust with the residue domi- anomalies in the Daheishan granitoids suggest plagioclase in the residue. nated by garnet amphibolite (Xiao et al., 2007; Zhang et al., 2006). High HREE and Y abundances imply that garnet was absent in the However, it seems unlikely for vast 5–15 km of marine gravity flow de- sources during melting. Group 2 rocks must have experienced significant posits to accumulate on thickened continental crust, based on a lack of fractional crystallization, as indicated by geochemical features of silica- – strong evidence for arc continent collision between the Kunlun and rich, marked depletion in Nb, Ta, Sr, Ti, Eu (Fig. 8g–p) and P2O5 Qiangtang terranes (Pullen et al., 2008) and marine deposition in both (Fig. 13a). Depletions in Nb, Ta, and Ti generally suggest the separation terranes during the Triassic time (Ding et al., 2013), Group 1 adakites of Ti-bearing phases such as ilmenite and/or rutile. Significant P2O5 may have been generated during retreating subduction of the Paleo- depletion probably demonstrates a fractionation of apatite (Bea, 1996). Tethys oceanic lithosphere (Ding et al., 2013; Pullen et al., 2008). Such Significant feldspar fractionation can explain the strong negative Eu a scenario has been postulated from far afield magmatism associated (Fig. 8) and Sr vs. Ba (Fig. 13f). The highly fractionated I-type rocks in with Carpathian lithospheric rollback (e.g. Seghedi et al., 2004). Here, Group 2 have extremely felsic compositions (most SiO2 N 69%) likely we propose that melting of the Paleo-Tethys oceanic slab including ba- acquired after a long fractionation history which makes it difficult to salts and overlying metasediments beneath the western HXSG complex discern their magma sources and melting conditions. However, for is responsible for genesis of Group 1 adakites. The evolved Sr–Nd highly evolved magmas, radiogenic isotopic ratios play an important isotope compositions of Group 1 relative to the Paleo-Tethys basaltic role in discriminating their magma sources. Isotopic data for Group 2 ophiolites (Fig. 10a) can be explained through metasedimentary rocks obtained in this study (Fig. 10a, b) indicate that samples are involvement during melting of the oceanic basalts. Then, the Sr–Nd characterized by high initial 87Sr/86Sr (0.7072–0.7143) ratios and isotope compositions of Group 1 adakites show the similarity with negative bulk-rock εNd(t)values(εNd(t) = −6.6 to −2.0). high-Mg andesites and dacites (Fig. 10a) which were thought to have However, recent zircon U–Pb–Hf–O isotopic studies suggest that I- been related to melting of metasediments (Wang et al., 2011b). Also, type granites can be generated through the reworking of sediments this is consistent with slightly negative εHf(t) values ( Fig. 12a), which modified by mantle-derived magmas (e.g. Kemp et al., 2007). Among 340 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348

87 86 Fig. 10. (a) Initial Sr/ Sr vs. εNd(t). Data of Paleo-Tethys ophiolites are from Bian et al. (2004); data of the Hoh-Xil turbidites are from She et al. (2006);(b)TDM vs. εNd (210 Ma). Data of the Neoproterozoic Bikou basalts are from Yan et al. (2004) and Wang et al. (2008b). Data of Neoproterozoic metamorphic and igneous rocks in the Songpan-Ganzi and western South China block are from references (Chen et al., 2001; Zhang et al., 2006; Zhou et al., 2006 and references therein; Zhao and Zhou, 2007). Data of Late Permian basalts from western South China block are from Xu et al. (2001). Data of Cambrian–Permian sediments in western South China block are from Shen et al. (1998) and Chen and Yang (2000).TheSr–Nd isotopic data of the Yidun, Songpan-Ganzi, Kunlun and Qiangtang Triassic igneous rocks are from references same in Fig. 1. Data of marine sediments are from Plank and Langmuir (1998). the Group 2 rocks, the Yunwuling samples exhibit highest εNd(t) values 5.2. Tectonic setting of the Late Triassic magmatism (−2.0 to −2.2) and could reflect a larger contribution of mantle- derived melts. Also, the relatively uniform and weakly positive εHf(t) The HXSG complex is a triangular tectonic unit which extends more values (Fig. 12a, εHf(t) = −0.6 to +3.0) indicate that these rocks than 2000 km along east–west trend and is broad in the east and may have been derived from juvenile crust and newly mantle-derived narrow in the west (Fig. 1). In contrast to the eastern HXSG basin, no melts in the sources for, at least, the Yunwuling pluton. Variable isotopic old basement rocks (e.g. Neoproterozoic or South China block) have εHf(t) ratios in these rocks must reflect the heterogeneous nature of been documented in the western HXSG complex. However, the origin their protoliths because zircon Hf isotope ratios of the melts are not of the Late Triassic–Early Jurassic intrusive rocks in the Hoh-Xil provides modified due to processes of partial melting or fractional crystallization valuable constraints on final stage evolution of the Paleo-Tethys ocean. from their parental magmas. Group 2 I-type rocks may have been The Hoh-Xil granitoids exhibit high initial 87Sr/86Sr and low εNd(t) generated by melting of a juvenile crust rather than through strong values (Fig. 10a, b), which are different from Late Permian basalts of fractionation crystallization of mantle-derived basalts since basaltic western South China Block (Xu et al., 2001) and Neoproterozoic Bikou magmas do not occur in the whole HXSG terrane (Fig. 1). This juvenile meta-basalts of northern South China Block (Wang et al., 2008b; Yan crust probably as an attenuated continental arc crust/lithosphere was et al., 2003, 2004). Thus, it seems unlikely that the Hoh-Xil granitoids separated from the Kunlun arc terrane during rollback of the subducting were derived from melting of the South China Block (Zhang et al., Paleo-Tethys oceanic lithosphere (e.g. Ding et al., 2013; Pullen et al., 2006), although the Sr–Nd isotope compositions of the western HXSG 2008). Here, we proposed that melting of an attenuated continental granitoids overlap with those of the eastern HXSG granitoids. Western arc juvenile crust is responsible for the genesis of Group 2 I-type HXSG granitoids also lack inherited Neoproterozoic ages in the range granites and this juvenile crust fragment was separated from the of 700–800 Ma that would suggest a South China Block related crustal Kunlun arc terrane during rollback of the subducting Paleo-Tethys source beneath the western HXSG (Supplementary Table 1 and 2). oceanic lithosphere (e.g. Ding et al., 2013; Pullen et al., 2008). Our data do not support, nor can rule out, the possibility that the L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 341

Fig. 11. (a) Zr/Sm vs. Nb/Ta (after Foley et al., 2002); (b) (La/Yb)N vs. YbN (after Defant and Drummond, 1990); (c) MgO vs. SiO2 (modified after Wang et al., 2006); (d) MgO# vs. SiO2

(modified after Wang et al., 2006 and references therein); (e) Th/La vs. K2O (modified after Zhou et al. (2006)); (f) Th vs. K2O(modified after Zhou et al. (2006)).

South China Block extends westward N1000 km as a continental their trace element signatures showing enrichment in LILE and deple- peninsula to the Hoh-Xil area. Instead, Sr, Nd and Hf isotopic composi- tion in HFSE such as Nb, Ta and Ti (Fig. 8a, b) and calc-alkaline major tions of the Hoh-Xil granitoids are similar to those of the Triassic Kunlun element characteristics typical of subduction zone magmatism (Jahn, and Yidun granitoids (Ding et al., 2011; Harris et al., 1988; Jiang et al., 2010, Fig. 7a). 2012; Liu et al., 2006) and to northern Qiangtang volcanic rocks The Permian–Triassic arc of the Kunlun terrane is thought to have (Fu et al., 2010; Wang et al., 2008a; Zhai et al., 2012; Zhang et al., been generated through subduction of north-dipping Paleo-Tethys 2011), although the northern Qiangtang igneous rocks have a wide oceanic lithosphere based on the distribution of fore-arc sediments range of Sr and Nd isotope values (Figs. 10a and 12a). Thus, it is most and geology to the north of the Kunlun terrane (Harris et al., 1988; likely that the Hoh-Xil granitoids were produced at the active margin Matte et al., 1996; Roger et al., 2003). It is also thought that south- such as continental or island arc. This conclusion is consistent with dipping subduction of the Paleo-Tethys lithosphere beneath the 342 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348

Fig. 12. (a) Initial Hf isotopic composition at the crystallization age of the zircons for the granitoids from the Hoh-Xil area. Reference lines representing meteoritic Hf evolution (CHUR) and depleted mantle (DM) are from Blichert-Toft and Albarede (1997),andGriffinetal.(2000), respectively; (b) whole-rock εNd (t) vs. zircon εHf(t) diagram after Vervoort et al. (1999).Data of Triassic granitoids from the Yidun arc are from Reid et al. (2007). northern margin of the Qiangtang terrane was coeval with the north- age of marine deposition cessation would likely be indistinguishable dipping subduction beneath the Kunlun terrane (Dewey et al., 1988; from adakitic rocks, which are N10 Ma apart (Ding et al., 2013; Hsü et al., 1995; Kapp et al., 2000; Pan et al., 2004). The north- and Enkelmann et al., 2007; Huang and Chen, 1987). Furthermore, the lack south-dipping subduction of Paleo-Tethys oceanic lithosphere beneath of bimodal magmatism makes adakite generation through high pressure the Kunlun and Qiangtang terranes during Permian–Triassic probably fractional crystallization of a basaltic magma difficult to support. The facilitated the closure of the Paleo-Tethys Ocean basin (e.g., Roger wide distribution of granitoids (Fig. 1) intruded into the HXSG complex et al., 2010; Şengör et al., 1988; Wang et al., 2011b; Yin and Nie, argues against a relatively static subduction zone beneath the complex 1993), but does not provide a geodynamic explanation for the genera- during Middle–Late Triassic time. tion of Triassic adakites and I-type granitoids within the HXSG complex. Rollback of the Paleo-Tethys oceanic lithosphere provides one Developing a geodynamic model to explain Middle–Late Triassic mechanism for satisfying the vast geographic and geochemical distribu- magmatism within HXSG is challenging. The presence of vast and thick tions of Middle–Late Triassic granitoids exposed within the HXSG marine gravity flow deposition that temporally overlap magmatism ar- complex. A growing body of evidence suggests that convergent margin gues against adakitic melt genesis from thickened continental crust or system is necessary to generate adakitic rocks similar to those identified delamination of thickened continental crust both of which would in Group 1 (e.g., Castillo et al., 1999). Geochemical data present here suggest insufficient accommodation space for the ~2.0 × 106 km3 of suggest that juvenile continental arc crust played a significant role in Middle–Upper Triassic marine sediments (Xiao et al., 2007; Yuan et al., the magma genesis of the western HXSG I-type granites of our study. 2010; Zhang et al., 2006, 2007). Continental crust of sufficient thickness This is at odds with convention suggesting that the Middle–Upper to drive delamination of the crust and mantle lithosphere would be on Triassic HXSG marine gravity flow deposits were mainly underlain by the order of ~50 km, typically have elevations exceeding the mean sea ocean crust during deposition (Şengör, 1984; Zhou and Graham, level, and would likely result in rock-, if not, surface uplift following the 1996). We argue that attenuation of continental arc crust above delamination event (Krystopowicz and Currie, 2013). If the delamination the initially northward subducting Paleo-Tethys oceanic lithosphere scenario were to be applied to the HXSG to explain adakite genesis, the created a fertile environment for adakite and I-type magmatism L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 343

Fig. 13. (a) SiO2 vs. P2O5;(b)SiO2 vs. Al2O3;(c)SiO2 vs. CaO; (d) 10000*Ga/Al vs. FeO*/MgO (after Whalen et al., 1987), FG: fractionated M-, I- and S-type granites, OGT: unfractionated M-, I- and S-type granites, Fogang highly fractionated I-type granites are from Li et al. (2007b); (e) Zr + Nb + Y + Ce vs. FeO*/MgO (after Whalen et al., 1987); (f) Sr vs. Ba. Ms: muscovite; Bt: biotite; Kfs: K-feldspar; Pl: plagioclase; Amp: amphibole; Grt: Garnet.

throughout the HXSG basin during Middle–Late Triassic time. This possibly earlier, as evidenced by Middle Triassic continental affinity model attributes attenuation of the continental upper plate to rollback UHP exposed in the Qinling-Dabie orogen (Hacker et al., 2004; Li et al., of Paleo-Tethys oceanic lithosphere beneath Kunlun arc (Ding et al., 1995; Okay et al., 1993; Ratschbacher et al., 2003). 2013; Pullen et al., 2008). Rollback of the Paleo-Tethys oceanic Mobility of the subduction zone and overlying magmatic arc in the lithosphere is thought to have began following a decrease in conver- rollback scenario suggested here explains the close spatial–temporal gence between the Gondwana affinity Qiangtang terrane, the South proximity adakitic and I-type granitoids. In this model, adakitic granitoids China Block, and North China Block following continent–continent would be generated through melting of the retreating subducting slab collisional orogenesis that started by at least Middle Triassic time, and and I-type granitoids would be produced by melting of the overlying 344 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348

attenuation of the Kunlun continental arc crust due to upwelling of asthenosphere in the subduction zone. Whereas attenuation of the conti- nental affinity back-arc regional and influx of asthenosphere towards the thinning juvenile arc crust and mantle lithosphere of the upper plate provide one possible scenario for the petrogenesis of A-type granitoids (Zhang et al., 2007) and shoshonitic magmas from the Songpan-Ganzi area (Yuan et al., 2010). In addition, attenuation of a continental affinity upper plate provides a mechanism for sufficient accommodation space for up to 15 km of marine gravity flow deposits.

5.3. Implication for the Paleo-Tethys closure

The northward subduction of the Paleo-Tethys oceanic lithosphere beneath the AKM suture started by Permian time (Figs. 14a and 15a, Bian et al., 2004; Dewey et al., 1988; Şengör, 1984). The Yidun, Songpan-Ganzi and Hoh-Xil terranes were thought to be adjacent to the Kunlun arc terrane before Early Triassic (Ding et al., 2013; Pullen et al., 2008). Northward subduction of the Paleo-Tethys oceanic lithosphere continued during Early Triassic. At the same time, the collision between the South China, North China and Qiangtang terrane may lead to rollback and retreating of the Paleo-Tethys trench beneath the Kunlun arc terrane (Figs. 14band15b, Ding et al., 2013; Pullen et al., 2008). Expansion of the back-arc basin resulted in strong attenuation Kunlun continental arc crust and possible seafloor spreading divided this atten- uated continental arc crust into at least three fragments such as the Yidun, Songpan-Ganzi and Hoh-Xil terranes (Pullen et al., 2008; Ding et al., 2013). During the retreating of the subducting Paleo-Tethys oceanic slab, gravity flow materials sourced from the adjacent landmass deposited into the fast expanding Mediterranean-style back-arc basin (Fig. 14c, Ding et al., 2013; Pullen et al., 2008). Meanwhile, Group 1 adakitic granitoids were generated above the retreating subducting Paleo- Tethys oceanic lithosphere through melting of oceanic slab and Group 2 I-type granitoids were generated by melting of garnet-absent amphib- olites of the Hoh-Xil attenuation crust inherited from the Kunlun juvenile arc, respectively (Figs. 14cand15c). Furthermore, the genera- tion of bimodal volcanic rocks in northern Qiangtang terrane (Fu et al., 2010; Wang et al., 2008a; Zhang et al., 2011) may result from the detachment of the double divergent subducted Paleo-Tethys oceanic lithosphere (Figs. 14cand15c, e.g. Soesoo et al., 1997). Due to the mobility of the subducting zone, the Hoh-Xil and Yidun arc fragments approached the western and eastern Qiangtang terrane whereas the Songpan-Ganzi arc fragment was close to the western margin of the South China Block (Fig. 14c). During latest Triassic to Early Jurassic, deformation and thickening of the Middle–Late Triassic gravity flow deposits were accompanied by continued northward motion of the Qiangtang terrane against the Kunlun terrane. Finally, the Yidun arc and Songpan-Ganzi arc collide with the western Qiangtang terrane and western margin of the South China Block, respectively. The Hoh-Xil arc fragment was locked between the Kunlun arc and the Qiangtang terrane (Figs. 14dand15d).

Fig. 14. Model for the Paleo-Tethys ocean closure and Triassic magmatism in the HXSG complex from the northern and eastern Tibet. (a) Permian: double divergent subduction of the Paleo-Tethys oceanic lithosphere beneath the Kunlun arc terrene and Qiangtang terrane and magmatism in the Kunlun arc; (b) Early Triassic: continued northward subduction of Paleo-Tethys oceanic lithosphere and resulting in several arc fragments within the Kunlun arc terrene such as Yidun, Songpan-Ganzi and Hoh-Xil; (c) Middle to Late Triassic: rollback of Paleo-Tethys oceanic lithosphere due to synchronous continent– continent collision between NCB and SCB which would decrease in convergence between Qiangtang and NCB, arc fragments such as Yidun, Songpan-Ganzi and Hoh-Xil were finally separated and drifted and arc magmatism occurred above the overlying plate, deep marine gravity flow deposited in the back-arc basin; (d) latest Triassic to Early Jurassic: deforma- tion and closure of the Paleo-Tethys ocean. KL: Kunlun arc; NCB: North China Block; SCB: South China Block; QD: Qinling-Dabie; QT: Qiangtang terrane: YD: Yidun arc: SG: Songpan-Ganzi arc; HX: Hoh-Xil arc; QQ: Qilian-Qaidam; LT: Longmenshan Thrust. L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 345

Fig. 15. Tectonic model for generation of granitoids in the Hoh-Xil area, western HXSG complex. (a) Permian: northward subduction of Paleo-Tethys; (b) Early Triassic: the attenuation Kunlun continental arc crust including the Hoh-Xil, Songpan-Ganzi and Yidun arc fragments due to rollback of the Paleo-Tethys oceanic lithosphere (Ding et al., 2013; Pullen et al., 2008); (c) Middle–Late Triassic: mobility of the Hoh-Xil arc fragment and arc magmatism due to subduction and rollback. Melting of the subducting Paleo-Tethys oceanic slab and overlying juvenile arc crust produced the Group 1 adakites and Group 2 I-type granites, respectively; gravity flow deposition coeval with adakitic and I-type granitoids (d) shortening and deformation of the HXSG complex and closure of the Paleo-Tethys ocean.

6. Conclusions supported by the Chinese Academy of Sciences (XDB05010400; KZCX2-YW-Q09-03), National Natural Science Foundation of China (1) The western Hoh-Xil–Songpan-Ganzi marine gravity flow deposits (41302162 to Zhang; 40625008 to Ding), Chinese Ministry of Science were extensively intruded by undeformed granitoid plutons and Technology (2011CB403101), U.S. National Science Foundation between 225 Ma and 193 Ma. (EAR-1118525; EAR-1008527), and Key Laboratory of Continental Colli- (2) These high-K calc-alkaline rocks from the western HXSG complex sion and Plateau Uplift Chinese Academy of Sciences (LCPU2011001). are subdivided into two groups based on their geochemistry. Group 1 (221–212 Ma: Dapeng Lake, Changhong Lake and References Heishibei Lake plutons) high-K adakitic calc-alkaline rocks were Atherton, M.P., Petford, N., 1993. Generation of sodium-rich magmas from newly probably derived from partial melting of the subducted Paleo- underplated basaltic crust. Nature 362, 144–146. Tethys oceanic slab including basalts and marine sediments. Barker, F., 1979. Trondhjemite: definition, environment and hypotheses of origin. In: Group 2 (225–190 Ma: Daheishan, Yunwuling, Zhuonai Lake, Barker, F. (Ed.), Trondhjemite. Dacite and Related Rocks. Elsevier, Amsterdam, pp. 1–12. Malanshan, and Hudongliang plutons) medium-K to high-K Bea, F., 1996. Residence of REE, Y, Th, and U in granites and crustal protoliths: implications calc-alkaline I-type granites were likely generated by melting of for the chemistry of crustal melts. Journal of Petrology 37, 521–552. the juvenile crust. We suggest that the least evolved Daheishan Bian, Q.T., Li, D.H., Pospelov, I., Yin, L.M., Li, H.S., Zhao, D.S., Chang, C.F., Luo, X.X., Gao, S.L., Astrakhantsev, O., Chamov, N., 2004. Age, geochemistry and tectonic setting of rocks were derived from partial melting of metabasaltic amphib- Buqingshan ophiolites, North Qinghai-Tibet Plateau, China. Journal of Asian Earth olites without garnet in the residue. The effect of fractionation Sciences 23, 577–596. was probably large during the petrogenesis of other highly Black, L.P., Kamo, S.L., Allen, M.C., Aleinikoff, J.N., Davis, D.W., Korsch, R.J., Foudoulis, C., 2003. TEMORA 1: a new zircon standard for Phanerozoic U–Pb geochronology. evolved I-type granites of Group 2. Chemical Geology 200, 155–170. (3) Middle to Late Triassic magmatism occurred in the Hoh-Xil– Blichert-Toft, J., Albarede, F., 1997. The Lu–Hf isotope geochemistry of chondrites and the Songpan-Ganzi complex occurred along an active margin and in evolution of the mantle-crust system. Earth and Planetary Science Letters 148, – the Yidun arc. These arc magmas are attributed to rollback and 243 258. Boynton, W.V., 1984. Cosmochemistry of the rare earth elements: meteorite studies. In: subduction of the Paleo-Tethys oceanic lithosphere. Henderson, P. (Ed.), Rare Earth Element Geochemistry. Elsevier, Amsterdam, the Netherlands, pp. 63–114. Supplementary data to this article can be found online at http://dx. Bruguier, O., Lancelot, J.R., Malavieille, J., 1997. U–Pb dating on single zircon grains fl doi.org/10.1016/j.lithos.2013.12.019. from the Triassic Songpan-Garze ysch (Central China): provenance and tectonic correlations. Earth and Planetary Science Letters 152, 217–231. Burchfiel, B.C., Chen, Z., Liu, Y., Royden, L.H., 1995. Tectonics of the Longmen Shan and Acknowledgments adjacent regions, central China. International Geology Review 37, 661–735. Cai, H.M., Zhang, H.F., Xu, W.C., Shi, Z.L., Yuan, H.L., 2010. Petrogenesis of Indosinian volcanic rocks in Songpan-Garze foldbelt of the northeastern Tibetan Plateau: new We are very grateful for constructive comments by two anonymous evidence for lithospheric delamination. Science in China Series D: Earth Science 52 reviewers and editorial handling by Nelson Eby. This study was (9), 1316–1328. 346 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348

Castillo, P.R., Janney, P.E., Solidum, R.U., 1999. Petrology and geochemistry of Camiguin Hsü, K., Pan, G., Sengör, A.M.C., 1995. Tectonic evolution of the Tibetan Plateau: a working island, southern Philippines: insights to the source of adakites and other lavas in a hypothesis based on the archipelago model of orogenesis. International Geology complex arc setting. Contributions to Mineralogy and Petrology 134, 33–51. Review 37 (6), 473–508. Chang, E.Z., 2000. Geology and tectonics of the Songpan-Ganzi fold belt, southwestern Jahn, B., Wu, F., Capdevila, R., Martineau, F., Zhao, Z., Wang, Y., 2001. Highly evolved China. International Geology Review 42, 813–831. juvenile granites with tetrad REE patterns: the Woduhe and Baerzhe granites from Chung, S.L., Liu, D.Y., Ji, J.Q., Chu, M.F., Lee, H.Y., Wen, D.J., Lo, C.H., Lee, T.Y., Qian, Q., Zhang, the Great Xing'an Mountains in NE China. Lithos 59, 171–198. Q., 2003. Adakites from continental collision zones: melting of thickened lower crust Jahn, B., 2010. Accretionary orogen and evolution of the Japanese Islands — implications beneath southern Tibet. Geology 31, 1021–1024. form a Sr–Nd isotope study of the Phanerozoic granitoids from SW Japan. American Chen, B., Wang, K., Liu, W., Cai, Z., Zhang, Q., Peng, X., Qiu, Y., Zheng, Y., 1987. Geotectonics Journal of Science 310, 1210–1249. of the Nujiang–Lancangjiang–Jinshajiang Region. Geological Publishing House, Jiang, C.F., Yang, J.S., Feng, B.G., Zhu, Z., 1992. Opening–closing Tectonics of the Kunlun Beijing, pp. 1–204. Mountains. Geological Publishing House, Beijing, pp. 1–224 (in Chinese with English Chen, Y.L., Yang, Z.F., 2000. Nd model ages of sedimentary profile from the northwest abstract). Yangtze craton, Guangyuan, Sichuan province, China and their geological implication. Jiang, Y.H., Jia, R.Y., Liu, Z., Liao, S.Y., Zhao, P., Zhou, Q., 2012. Origin of Middle Triassic high- Geochemical Journal 34, 263–270. K calc-alkaline granitoids and their potassic microgranular enclaves from the western Chen, Y.L., Luo, Z.H., Liu, C., 2001. New recognition of Kangding–Mianning metamorphic Kunlun orogen, northwest China: a record of the closure of Paleo-Tethys. Lithos 159, complexes from Sichuan, western Yangtze craton: evidence from Nd isotopic 13–30. composition. Journal of China University of Geosciences: Earth Science 26 (3), Kapp, P., Yin, A., Manning, C.E., Murphy, M., Harrison, T.M., Spurlin, M., Ding, L., Deng, X.G., 279–285. Wu, C.M., 2000. Blueschist-bearing metamorphic core complexes in the Qiangtang Chappell, B.W., White, A.J.R., 1992. I- and S-type granites in the Lachlan Fold Belt. block reveal deep crustal structure of northern Tibet. Geology 28, 19–22. Transactions of the Royal Society of Edinburgh: Earth Sciences 83, 1–26. Kapp, P., Yin, A., Manning, C.E., Harrison, T.M., Taylor, M.H., 2003. Tectonic evolution of the Chappell, B.W., Stephens, W.E., 1988. Origin of infracrustal (I-type) granite early Mesozoic blueschist-bearing Qiangtang metamorphic belt, central Tibet. magmas. Transactions of the Royal Society of Edinburgh: Earth Sciences 79 Tectonics 22, 1043–1059. (2–3), 71–86. Kemp, A.I.S., Hawkesworth, C.J., Foster, G.L., Paterson, B.A., Woodhead, J.D., Hergt, J.M., Condie, K.C., 2005. TTGs and adakites: are they both slab melts? Lithos 80, 33–44. Gray, C.M., Whitehouse, M.J., 2007. Magmatic and crustal differentiation history of Dai, J.G., Wang, C.S., Hourigan, J., Santosh, M., 2013. Multi-stage tectono-magmatic events granitic rocks from Hf–O isotopes in zircon. Science 315, 980–983. of the Eastern Kunlun Range, northern Tibet: insights from U–Pb geochronology and Krystopowicz, N.J., Currie, C.A., 2013. Crustal eclogitization and lithosphere delamination (U–Th)/He thermochronology. Tectonophysics 599, 97–106. in orogens. Earth and Planetary Science Letters 361, 195–207. Dazé, A., Leea, K.W.J., Villeneuve, M., 2003. An intercalibration study of the Fish Canyon Li, C., Chen, L.R., Hu, K., Yang, Z.R., Hong, Y.R., 1995. Study on the Paleo-Tethys Suture sanidine and biotite 40Ar/39Ar standards and some comments on the age of the Fish Zone of Lungmu Co–Shuang Hu, Tibet. Geological Publishing House, Beijing, Canyon Tuff. Chemical Geology 199, 111–127. pp. 1– 131 (in Chinese with English abstract). Defant, M.J., Drummond, M.S., 1990. Derivation of some modern arc magmas by melting Li, C.F., Chen, F.K., Li, X.H., 2007a. Precise isotopic measurements of sub-nanogram Nd of of young subducted lithosphere. Nature 347, 662–665. standard reference material by thermal ionization mass spectrometry using the Defant, M.J., Xu, J.F., Kepezhinskas, P., Wang, Q., Zhang, Q., Xiao, L., 2002. Adakites: some NdO + technique. International Journal of Mass Spectrometry 266, 34–41. variations on a theme. Acta Petrologica Sinica 18, 129–142. Li, X.H., Li, Z.X., Li, W.X., Liu, Y., Yuan, C., Wei, G.J., Qi, C.S., 2007b. U–Pb zircon, geochemical Dewey, J.F., Shackelton, R.M., Chang, C., Sun, Y., 1988. The tectonic evolution of the Tibetan and Sr–Nd–Hf isotopic constraints on age and origin of Jurassic I- and A-type granites Plateau. Philosophical Transactions of the Royal Society London A 327, 379–413. from central Guangdong, SE China: a major igneous event in response to foundering Ding, S., Huang, H., Niu, Y.L., Zhao, Z.D., Yu, X.H., Mo, X.X., 2011. Geochemistry, of a subducted flat-slab? Lithos 96, 186–204. geochronology and petrogenesis of East Kunlun high Nb–Ta rhyolites. Acta Li, J.W., Zhao, X.F., Zhou, M.F., Ma, C.Q., de Souza, Z.S., Vasconcelos, P., 2009. Late Petrologica Sinica 27 (12), 3603–3614 (in Chinese with English abstract). Mesozoic magmatism from the Daye region, eastern China: U–Pb ages, Ding, L., Yang, D., Cai, F.L., Pullen, A., Kapp, P., Gehrels, G.E., Zhang, L.Y., Zhang, Q.H., Lai, petrogenesis, and geodynamic implications. Contributions to Mineralogy and Q.Z., Yue, Y.H., Shi, R.D., 2013. Provenance analysis of the Mesozoic Hoh-Xil– Petrology 157, 383–409. Songpan-Ganzi turbidites in northern Tibet: implications for the tectonic evolution Liu, C.D., Mo, X.X., Luo, Z.H., Yu, X.H., Chen, H.W., Li, S.W., Zhao, X., 2004. Mixing events of the eastern Paleo-Tethys Ocean. Tectonics 32, 1–15. between the crust and mantle-derived magmas in Eastern Kunlun: evidence from Elena, A.K., Maurice, B., Jacques, M., 2003. Discovery of the Paleo-Tethys residual zircon SHRIMP chronology. Chinese Science Bulletin 49, 823–834. peridotites along the Anyemaqen–KunLun suture zone (North Tibet). Comptes Liu, R., Fang, Q.X., Ma, Y.Z., 2006. Formation time, petrology, geochemistry and tectonic Rendus Geoscience 335, 709–719. setting of peraluminous granites in the Yunwuridge area, Xinjiang. Xingjiang Geology Enkelmann, E., Weislogel, A., Ratschbacher, L., Eide, E., Renno, A., Wooden, J., 2007. How 24 (3), 223–228 (in Chinese with English abstract). was the Triassic Songpan-Ganzi basin filled? A provenance study. Tectonics 26, Ludwig, K.R., 2003. Isoplot 3.00. Special Publication No. 4.Berkeley Geochronology Center TC4007. http://dx.doi.org/10.1029/2006TC002078. (70 pp.). Foley, S.F., Tiepolo, M., Vannucci, R., 2002. Growth of early continental crust controlled by Lü, J.G., Wang, J.C., Chu, C.H., Li, L.Q., Liu, R., Lei, H.M., 2006. Zircon SHRIMP U–Pb dating of melting of amphibolite in subduction zones. Nature 417, 637–640. the Wolonggang Monzogranite porphyry in the western segment of the Hoh Xil belt, Fu, X.G., Wang, J., Tan, F.W., Chen, M., Chen, W.B., 2010. The Late Triassic rift-related Qinghai–Tibet Plateau and its geological significance. Geological Bulletin of China 26, volcanic rocks from eastern Qiangtang, northern Tibet (China): age and tectonic 721–724 (in Chinese with English abstract). implications. Gondwana Research 17, 135–144. Matte, P., Tapponnier, P., Arnaud, N., Bourjot, L., Avouac, J.P., Vidal, P., Liu, Q., Pan, Y., Gao, S., Rudnick, R.L., Yuan, H.L., Liu, X.M., Liu, Y.S., Xu, W.L., Ling, W.L., Ayers, J., Wang, Wang, Y., 1996. Tectonics of Western Tibet, between the Tarim and the Indus. Earth X.C., Wang, Q.H., 2004. Recycling lower continental crust in the North China craton. and Planetary Science Letters 142, 311–330. Nature 432, 892–897. Macpherson, C.G., Dreher, S.T., Thirlwall, M.F., 2006. Adakites without slab melting: high Griffin, W.L., Pearson, N.J., Belousova, E., Jackson, S.E., van Achterbergh, E., O'Reilly, S.Y., pressure differentiation of island arc magma, Mindanao, the Philippines. Earth and Shee, S.R., 2000. The Hf isotope composition of cratonic mantle: LAM-MC-ICPMS Planetary Science Letters 243, 581–593. analysis of zircon megacrysts in kimberlites. Geochimica et Cosmochimimica Acta Mahoney, J.J., Frei, R., Tejada, M.L.G., Mo, X.X., Leat, P.T., 1998. Tracing the Indian ocean 64, 133–147. mantle domain through time: isotopic results from old west Indian, east Tethyan Gu, X.X., 1994. Geochemical characteristics of the Triassic Tethys-turbidites in and south Pacificseafloor. Journal of Petrology 39, 1285–1306. northwestern Sichuan, China: implications for provenance and interpretation of the Meng, Q.R., Wang, E., Hu, J.M., 2005. Mesozoic sedimentary evolution of northwest tectonic setting. Geochimica et Cosmochimica Acta 58, 4615–4631. Sichuan Basin: implications for continued clockwise rotation of the South China Hacker, B.R., Ratschbacher, L., Liou, J.G., 2004. Subduction, collision, and exhumation in Block. Geologic Society of American Bulletin 117 (3), 396–410. the Qinling–Dabie orogeny. Geological Society of London Special Publication 226, Moyen, J.F., 2009. High Sr/Y and La/Yb ratios: the meaning of the “adakitic signature”. 157–175. Lithos 112, 556–574. Harris, N.B.W., Xu, R., Lewis, C.L., Jin, C., 1988. Plutonic rocks of the 1985 Tibet geotraverse, Mungall, J.E., 2002. Roasting the mantle: slab melting and the genesis of major Au and Au- Lhasa to Golmud. Philosophical Transactions of the Royal Society London A327, rich Cu deposits. Geology 30, 915 –918. 145–168. Nie, S., Yin, A., Rowley, D., Jin, Y., 1994. Exhumation of the Dabie shan ultra-high pressure Hou, Z.Q., Gao, Y.F., Qu, X.M., Rui, Z.Y., Mo, X.X., 2004. Origin of adakitic intrusives rocks and accumulation of the Songpan-Ganzi flysch sequence, central China. generated during mid-Miocene east–west extension in southern Tibet. Earth and Geology 22, 999–1002. Planetary Science Letters 220, 139 –155. Okay, A.I., Şengör, A.M.C., Satir, M., 1993. Tectonics of an ultrahigh-pressure metamorphic Hou, Z.Q., Zaw, K., Pan, G.T., Mo, X.X., Xu, Q., Hu, Y.Z., Li, X.Z., 2007. Sanjiang Tethyan terrane: the Dabie Shan/Tongbai Shan orogen, China. Tectonics 12, 1320–1334. metallogenesis in S.W. China: tectonic setting, metallogenic epochs and deposit Pan, G., Ding, J., Yao, D., Wang, L., 2004. Geologic map of Qinghai-Xizang (Tibet) Plateau types. Ore Geology Reviews 31, 48–87. and adjacent areas, scale 1: 1,500,000, Chengdu Cartographic Publishing House, Hu, J.M., Meng, J.R., Shi, Y.R., Qu, H.J., 2005. SHRIMP U–Pb dating of zircons from granitoid Chengdu. bodies in the Songpan-Ganzi terrane and its implications. Acta Petrologica Sinica 21, Patiño Douce, A.E., 1999. What do experiments tell us about the relative contributions of 867–880 (in Chinese with English abstract). crust and mantle to the origin of granitic magmas? In: Castro, A., Fernandez, C., Huang, M.H., Buick, I.S., Hou, L.W., 2003. Teconometamorphic evolution of the eastern Vigneresse, J.L. (Eds.), Understanding Granites. Integrating New and Classical Tibet Plateau: evidence from the central Songpan-Ganze orogenic belt, western Techniques. Geological Society, London, Special Publication, 158, pp. 55–75. China. Journal of Petrology 44, 255–278. Pearce, J.A., Norry, M.J., 1979. Petrogenetic implications of Ti, Zr, Y, and Nb variations in Huang, J.Q., Chen, B.W., 1987. The Evolution of the Tethys in China and Adjacent Regions. volcanic rocks. Contributions to Mineralogy and Petrology 69, 33–47. Geological Publishing House, Beijing 1–190. Peccerillo, A., Taylor, S.R., 1976. Geochemistry of Eocene calc-alkaline volcanic rocks from Huang,F.A.,He,Y.S.,2010.Partial melting of the dry mafic continental crust: implications the Kastamonu area, northern Turkey. Contributions to Mineralogy and Petrology 58, for petrogenesis of C-type adakites. Chinese Science Bulletin 55, 2428–2439. 63–81. L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348 347

Petford, N., Atherton, M., 1996. Na-rich partial melts from newly underplated basal- Whalen, J.B., Currie, K.L., Chappell, B.W., 1987. A-type granites: geochemical characteris- tic crust: the Cordillera Blanca Batholith, Peru. Journal of Petrology 37, tics, discrimination and petrogenesis. Contributions to Mineralogy and Petrology 1491–1521. 95, 407–419. Pe-Piper, G., Piper, D.J.W., 1994. Miocene magnesian andesites and dacites, Evia, Greece: Wang, Q., McDermott, F., Xu, J.F., Bellon, H., Zhu, Y.T., 2005. Cenozoic K-rich adakitic adakites associated with subducting slab detachment and extension. Lithos 31, volcanic rocks in the Hohxil area, northern Tibet: lower-crust melting in an 125–140. intracontinental setting. Geology 33, 465 –468. Plank, T., Langmuir, C.H., 1998. The chemical composition of subducting sediment and its Wang, Q., Xu, J.F., Jian, P., Bao, Z.W., Zhao, Z.H., Li, C.F., Xiong, X.L., Ma, J.L., 2006. consequences for the crust and mantle. Chemical Geology 145, 325–394. Petrogenesis of adakitic porphyries in an extensional tectonic setting, Dexing, South Pullen, A., Kapp, P., Gehrels, G.E., Vervort, J.D., Ding, L., 2008. Triassic continental China: implications for the genesis of porphyry copper mineralization. Journal of subduction in central Tibet and Mediterranean-style closure of the Paleo-Tethys Petrology 47 (1), 119–144. Ocean. Geology 36, 5351–5354. Wang, Q., Wyman, D.A., Xu, J., Jian, P., Zhao, Z., Li, C., Xu, W., Ma, J., He, B., 2007. Early Qu, X., Hou, Z., Li, Y., 2004. Melt components derived from a subducted slab in late Cretaceous adakitic granites in the Northern Dabie Complex, central China: orogenic ore-bearing porphyries in the Gangdese copper belt, southern Tibetan implications for partial melting and delamination of thickened lower crust. Plateau. Lithos 74, 131–148. Geochimica et Cosmochimimica Acta 71 (10), 2609–2636. Rapp, R.P., Watson, E.B., Miller, C.F., 1991. Partial melting of amphibolite/eclogite and the Wang, Q., Wyman, A., Xu, J.F., Wan, Y.S., Li, C.F., Zi, F., Jiang, Z.Q., Qiu, H.N., Chu, Z.Y., Zhao, origin of Archean trondhjemites and tonalites. Precambrian Research 51 (1–4), 1–25. Z.H., Dong, Y.H., 2008a. Triassic Nb-enriched basalts, magnesian andesites, and Rapp, R.P., Watson, E.B., 1995. Dehydration melting of metabasalt at 8–32 kbar: adakites of the Qiangtang terrane (Central Tibet): evidence for metasomatism by implications for continental growth and crust-mantle recycling. Journal of Petrology slab-derived melts in the mantle wedge. Contributions to Mineralogy and Petrology 36, 891–931. 155, 473–490. Ratschbacher, L., Hacker, B.R., Calvert, A., Webb, L.E., Grimmer, J.C., McWilliams, M.O., Wang, X.C., Li, X.H., Li, W.X., Li, Z.X., Liu, Y., Yang, Y.H., Liang, X.R., Tu, X.L., 2008b. The Ireland, T., Dong, S.W., Hu, J.M., 2003. Tectonics of the Qinling (Central China): Bikou basalts in the northwestern Yangtze block, South China: remnants of tectonostratigraphy, geochronology, and deformation history. Tectonophysics 366, 820–810 Ma continental flood basalts? The Geological Society of America Bulletin 1–35. 120, 1478–1492. Reid, A., Wilson, C.J.L., Shun, L., Pearson, N., Belousova, E., 2007. Mesozoic plutons of the Wang, B.Q., Zhou, M.F., Li, J.W., Yan, D.P., 2011a. Late Triassic porphyritic intrusions Yidun arc, SW China: U/Pb geochronology and Hf isotopic signature. Ore Geology and associated volcanic rocks from the Shangri-La region, Yidun terrane, Eastern Reviews 34, 88–106. Tibetan Plateau: adakitic magmatism and porphyry copper mineralization. Lithos Renne, P.R., Deino, A.L., Walter, R.C., Turrin, B.D., Swisher, C.C., Becker, T.A., Curtis, G.H., 127, 24–38. Sharp, W.D., Jaouni, A.R., 1994. Intercalibration of astronomical and radioisotopic Wang, Q., Li, Z.X., Chung, S.L., Wyman, D.A., Sun, Y.L., Zhao, Z.H., Zhu, Y.T., Qiu, H.N., 2011b. time. Geology 22, 783–786. Late Triassic high-Mg andesite/dacite suites from northern Hohxil, North Tibet: Roberts, M.P., Clemens, J.D., 1993. Origin of high-potassium, calcalkaline, I-type granitoids. Geochronology, geochemical characteristics, petrogenetic processes and tectonic Geology 21, 825–828. implications. Lithos 126 (1–2), 54–67. Roger, F., Arnaud, N., Gilder, S., Tapponnier, P., Jolivet, M., Brunel, M., Malavieille, J., Xu, Z., Weislogel, A.L., 2008. Tectonostatigraphic and geochronologic constraints on evolution 2003. Geochronological and geochemical constraints on Mesozoic suturing in east of the northeast Paleotethys from the Songpan-Ganzi complex, central China. central Tibet. Tectonics 27, 101–117. Tectonophysics 451, 331–345. Roger, F., Malavieille, J., Leloup, Ph.H., Calassou, S., Xu, Z., 2004. Timing of granite Williams, I.S., 1998. U–Th–Pb geochronology by ion microprobe. In: Mchinbben, M.A., emplacement and cooling in the Songpan-Garze fold belt (eastern Tibetan Plateau) Ahanks, W.C., Ridey, W.I. (Eds.), Application of Microanalytical Techniques to with tectonic implications. Journal of Asian Earth Sciences 22, 465–481. Understanding Mineralizing Process. Reviews in Economic Geology, 7, pp. 1–35. Roger, F., Jolivet, M., Malavieille, J., 2010. The tectonic evolution of the Songpan-Garzê Wu, F.Y., Jahn, B.M., Wilde, S.A., Lo, C.H., Yui, T.F., Lin, Q., Ge, W.C., Dun, D.Y., 2003. Highly (North Tibet) and adjacent areas from Proterozoic to Present: a synthesis. Journal fractionated I-type granites in NE China (I): geochronology and petrogenesis. Lithos of Asian Earth Sciences 39 (4), 254–269. 66, 241–273. Schwab, M., Ratschbacher, L., Siebel, W., McWilliams, M., Minaey, V., Lutkoy, V., Chen, F., Wu, F.Y., Yang, Y.H., Xie, L.W., Yang, J.H., Xu, P., 2006. Hf isotopic compositions of the Stanek, K., Belson, B., Frisch, W., Wooden, J.L., 2004. Assembly of the Pamirs: age standard zircons and baddeleyites used in U–Pb geochronology. Chemical Geology and origin of magmatic belts from the southern Tien Shan to the southern Pamirs 234, 105–126. and their relation to Tibet. Tectonics 23, TC4002. http://dx.doi.org/10.1029/ Xiao, L., Zhang, H.F., Clemens, J.D., Wang, Q.W., Kan, Z.Z., Wang, K.M., Ni, P.Z., Liu, X.M., 2003TC001583. 2007. Late Triassic Granitoids of the Eastern Margin of the Tibetan Plateau: Seghedi, I., Downes, H., Szakács, A., Mason, P.R.D., Thirlwall, M.F., Rou, E., Pécskay, geochronology, petrogenesis and implications for tectonic evolution. Lithos 96, Z., Márton, E., Panaiotu, C., 2004. Neogene–Quaternary magmatism and 436–452. geodynamics in the Carpathian–Pannonian region: a synthesis. Lithos 72 Xiao, L., Clemens, J.D., 2007. Origin of potassic (C-type) adakite magmas: experimental (3–4), 117–146. and field constraints. Lithos 95 (3–4), 399–414. Şengör, A.M.C., 1984. The Cimmeride orogenic system and the tectonics of Eurasia. Xie, L.W., Zhang, Y.B., Zhang, H.H., Sun, J.F., Wu, F.Y., 2008. In situ simultaneous Geological Society of America Special Paper 195, 1–82. determination of trace elements, U–Pb and Lu–Hf isotopes in zircon and baddeleyite. Şengör, A.M.C., Altiner, D., Cin, A., Ustaömer, T., Hsü, J.K., 1988. Origin and assembly of the Chinese Science Bulletin 53, 1565–1573. Tethy-side orogenic collage at the expense of Gondwana-land. Geological Society, Xiong, X.L., Adam, J., Green, T.H., 2005. Rutile stability and rutile/melt HFSE partitioning London, Special Publications 37 (1), 119–191. during partial melting of hydrous basalt: implications for TTG genesis. Chemical Sen, C., Dunn, T., 1994. Dehydration melting of a basaltic composition amphibolite at 1.5 Geology 218, 339–359. and 2.0 Gpa: implications for the origin of adakites. Contributions to Mineralogy and Xu, R.H., Schärer, U., Allègre, C.J., 1985. Magmatism and metamorphism in the Lhasa block Petrology 117, 394–409. (Tibet): a geochronological study. Journal of Geology 93, 41–57. She, Z.B., Ma, C.Q., Mason, R., Li, J.W., Wang, G.C., Lei, Y.H., 2006. Provenance of the Triassic Xu, J.F., Shinjo, R., Defant, M.J., Wang, Q., Rapp, R.P., 2002. Origin of Mesozoic adakitic Songpan-Ganzi flysch, west China. Chemical Geology 231, 159–175. intrusive rocks in the Ningzhen area of east China: partial melting of delaminated Shen, W.Z., Lu, H.P., Xu, S.J., Wang, R.C., Lin, H.F., Huang, D., Pan, J., 1998. Sm–Nd isotopic lower crust? Geology 30, 1111–1114. study on metasediments in the area of Danba, China. Scientia Geologica Sinica 33 (3), Xu, Z.Q., Hou, L.W., Wang, Z.X., Fu, X.F., Huang, M.H., 1992. Orogenic Processes of the 367–373 (in Chinese with English abstract). Songpan-Garze Orogenic Belt of China. Geological Publishing House, Beijing, Shi, Z.L., Zhang, H.F., Cai, H.M., 2009. Petrogenesis of strongly peraluminous granites in pp. 1–190 (in Chinese with English abstract). Markan area, Songpan fold belt and its tectonic implication. Journal of China Xu, Y.G., Chung, S.L., Jahn, B.M., Wu, G.Y., 2001. Petrological and geochemical constraints University of Geosciences: Earth Science 34 (4), 569–584 (in Chinese with English on the petrogenesis of the Permo-Triassic Emeishan flood basalts in southwestern abstract). China. Lithos 58, 145–168. Soesoo, A., Bons, P.D., Gray, D.R., Foster, D.A., 1997. Divergent double subduction: tectonic Yan, Q.R., Wang, Z.Q., Yan, Z., Andraw, D.H., 2003. SHRIMP U–Pb zircon dating constraints and petrologic consequences. Geology 25, 755–758. on formation time of the Bikou Group volcanic rocks. Geological Bulletin of China 22, Stacey, J.C., Kramers, J., 1975. Approximation of terrestrial lead isotope evolution by a 456–460 (in Chinese with English abstract). two-stage model. Earth and Planetary Science Letters 26, 207–221. Yan, Q.R., Andrew, D.H., Wang, Z.Q., Yan, Z., Peter, A.D., Wang, T., Liu, D.Y., Song, B., Jiang, Stampfli, G.M., Borel, G.D., 1992. A plate tectonic model for the Paleozoic and Mesozoic C.F., 2004. Geochemical and tectonic setting of the Bikou volcanic terrane on the constrained by dynamic plate boundaries and restored synthetic oceanic isochrons. northern margin of the Yangtze plate. Acta Petrologica et Mineralogica 23, 2–11 Earth and Planetary Science Letters 196, 17–33. (in Chinese with English abstract). Steiger, R.H., Jäger, E., 1977. Subcommission on geochronology: convention on the use of Yang, J.S., Robinson, P.T., Jiang, C.F., Xu, Z.Q., 1996. Ophiolites of the Kunlun Mountains, decay constants in geo- and cosmochronology. Earth and Planetary Science Letters China and their tectonic implications. Tectonophysics 258, 215–231. 36, 359–362. Yin, A., Harrison, T.M., 2000. Geologic evolution of the Himalayan–Tibetan orogen. Annual Sun, S.S., McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: Review of Earth and Planetary Sciences 28, 211–280. implications for mantle composition and processes. In: Saunders, A.D., Norry, M.J. Yin, A., Nie, S., 1993. An indentation model for the North and South China collision and the (Eds.), Magmatism in the Ocean Basin. Blackwell Scientific Publications, Geological development of the Tanlu and Honam fault systems, eastern Asian. Tectonics 12, Society Special Publication, 42, pp. 313–346. 801–813. Stern, C.R., Kilian, R., 1996. Role of the subducted slab, mantle wedge and continental Yuan, C., Sun, M., Xiao, W.J., Wilde, S., Li, X.H., Liu, X.H., Long, X.P., Xia, X.P., Ye, K., Li, J.L., crust in the generation of adakites from the Austral Volcanic Zone. Contributions to 2009. Garnet-bearing tonalitic porphyry from East Kunlun, Northeast Tibetan Mineralogy and Petrology 123, 263–281. Plateau: implications for adakite and magmas from the MASH Zone. International Vervoort, J., Patchett, P.J., Blichert-Toft, J., Albarede, F., 1999. Relationships between Lu–Hf Journal of Earth Sciences 98 (6), 1489–1510. and Sm–Nd isotopic systems in the global sedimentary system. Earth and Planetary Yuan, C., Zhou, M.F., Sun, M., Zhao, Y.J., Wilde, S., Long, X.P., Yan, D.P., 2010. Triassic Science Letters 168, 79–99. granitoids in the eastern Songpan Ganzi Fold Belt, SW China: magmatic response to 348 L.-Y. Zhang et al. / Lithos 190–191 (2014) 328–348

geodynamics of the deep lithosphere. Earth and Planetary Science Letters 290 (3–4), Zhang, K.J., Li, B., Wei, Q.G., Cai, J.X., Zhang, Y.X., 2008c. Proximal provenance of the western 481–492. Songpan-Ganzi turbidite complex (Late Triassic, Eastern Tibetan Plateau): implications Zhai, Q.G., Jahn, B.M., Su, L., Wang, J., Mo, X.X., Lee, H.Y., Wang, K.L., Tang, S., 2012. Triassic for the tectonic amalgamation of China. Sedimentary Geology 208, 36–44. arc magmatism in the Qiangtang area, northern Tibet: zircon U–Pb ages, geochemical Zhang, K.J., Tang, X.C., Wang, Y., Zhang, Y.X., 2011. Geochronology, geochemistry, and Nd and Sr–Nd–Hf isotopic characteristics, and tectonic implications. Journal of Asian isotopes of early Mesozoic bimodal volcanism in northern Tibet, western China: Earth Sciences 63, 162–178. constraints on the exhumation of the central Qiangtang metamorphic belt. Lithos Zhang, H.F., Zhang, L., Harris, N., Jin, L.L., Yuan, H.L., 2006. U–Pb zircon ages, geochemical 121 (1–4), 167–175. and isotopic compositions of granitoids in Songpan–Garze fold belt, eastern Zhao, J.H., Zhou, M.F., 2007. Geochemistry of Neoproterozoic mafic intrusions in the Tibetan Plateau: constraints on petrogenesis and tectonic evolution of the basement. Panzhihua district (Sichuan Province, SW China): implications for subduction-related Contribution to Mineralogy and Petrology 152, 75–88. metasomatism in the upper mantle. Precambrian Research 152, 27–47. Zhang, H.F., Parrish, R., Zhang, L., Xu, W.C., Yuan, H.L., Gao, S., Crowley, Q.G., 2007. A-type Zhou, D., Graham, S.A., 1996. The Songpan-Ganzi complex of the western Qinling Shan as granite and adakitic magmatism association in Songpan-Garze fold belt, eastern a Triassic remnant ocean basin. In: Yin, A., Harrison, T.M. (Eds.), The Tectonic Tibetan Plateau: implication for lithospheric delamination. Lithos 97, 323–335. Evolution of Asia. Cambridge University Press, Cambridge, pp. 281–299. Zhang, C.Z., Li, B., Cai, J.X., Tang, X.C., Wei, Q.G., Zhang, Y.X., 2008a. A-type granite and Zhou, M.F., Yan, D.P., Kennedy, A.K., 2002. SHRIMP U–Pb zircon geochronological and adakitic magmatism association in Songpan-Garze fold belt, eastern Tibetan Plateau: geochemical evidence for Neoproterozoic arc magmatism along the west margin of implication for lithospheric delamination: comment. Lithos 103, 562–564. Yangtze Block, South China. Earth and Planetary Science Letters 198, 51–67. Zhang, H.F., Parrish, R., Zhang, L., Xu, W.C., Yuan, H.L., Gao, S., Crowley, Q.G., 2008b. Reply Zhou, M.F., Yan, D.P., Wang, C.L., Qi, L., Kennedy, A., 2006. Subduction-related origin of the to the comment by Zhang et al. on: “First finding of A-type and adakitic magmatism 750 Ma Xuelongbao adakitic complex (Sichuan Province, China): implications for the association in Songpan-Garze fold belt, eastern Tibetan Plateau: Implication for tectonic setting of the giant Neoproterozoic magmatic event in South China. Earth lithospheric delamination”. Lithos 103, 565–568. and Planetary Science Letters 248, 286–300.