Age and Origin of High Ba–Sr Appinite–Granites at the Northwestern

Available online at www.sciencedirect.com

Gondwana Research 13 (2008) 126–138 www.elsevier.com/locate/gr

Age and origin of high Ba–Sr appinite–granites at the northwestern margin of the Tibet Plateau: Implications for early Paleozoic tectonic evolution of the Western Kunlun orogenic belt ⁎ Hai-Min Ye a, Xian-Hua Li b, Zheng-Xiang Li c, Chuan-Lin Zhang a,

a Nanjing Institute of Geology and Mineral Resources, China Geological Survey, Nanjing 210016, China b Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China c Institute of Geoscience Research (TIGeR), Department of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth WA 6845, Australia Received 10 May 2007; received in revised form 3 August 2007; accepted 5 August 2007 Available online 7 September 2007

Abstract

The Buya appinite–granite is a typical high Ba–Sr granite emplaced at the northern West Kunlun orogenic belt along the northwestern margin of the Tibetan Plateau. The granite is dated at ca. 430 Ma using the SHRIMP U–Pb zircon method. It consists of alkaline feldspar granites with coeval appinite enclaves. The granite possesses high SiO2 (69.77–72.69%), K2O (4.44–5.10%) and total alkalinity (K2O+Na2O=8.80–9.92%), Sr (655–1100 ppm), Ba (1036–1433 ppm) and LREE, and low HREE and HFSE contents and insignificant negative Eu anomalies. Consequently, # the samples have very high Sr/Y (74–141) and (La/Yb)N (37–96) ratios. On the other hand, they have low MgO (or Mg ), Cr and Ni contents and low radiogenic Nd isotopes (ɛNd(T)=−8.4 to −10.4). The high Ba–Sr and other geochemical signatures of the granite also appear in the appinite enclaves except that the appinite enclaves have relatively higher abundances in these elements and higher ɛNd(T) values (−5.7 to −6.7). Elemental and isotope compositions suggest that the appinites were derived from partial melting of an enriched lithospheric mantle source probably induced by upwelling of the asthenosphere due to the delamination of a subducted slab. The granite was likely derived from partial melting of the mafic lower crust (with residual garnet), associated with involvement of minor LILE-enriched appinitic magma, followed by crystal fractionation of hornblende, biotite, apatite and allanite. In combination with previous investigations on the evolution of the Western Kunlun, we suggest that the Buya high Ba–Sr plutons represent the end of an early Paleozoic crust thickening event after a terrane accretion on southern Tarim craton, and the beginning of a post-orogenic collapse phase in the Paleozoic West Kunlun orogenic belt. © 2007 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Keywords: Buya high Ba–Sr appinite–granite; Geochronology; Geochemistry; Petrogenesis; Tectonic implications; West Kunlun orogenic belt

1. Introduction

The geologic and tectonic evolution of the North China Craton and surrounding crustal blocks have been the focus of various important investigations and debates on the structural, magmatic and metamorphic histories and supercontinent genesis (Santosh et al., 2006; Kusky et al., 2007 and references therein). While many of the studies focused on the Paleoproterozoic evolution of the North China Craton, the Paleozoic and Mesozoic evolution of the region is also critical to the understanding the evolution of the East and Southeast Asian continental lithosphere (cf. Metcalfe, 2006). In this context, the

⁎ Corresponding author. Tel.: +86 25 84897946; fax: +86 25 84600446. Fig. 1. Major tectonic units of the Tibet Plateau. The West Kunlun orogen is on E-mail address: [email protected] (C.-L. Zhang). the northern periphery of the Tibet Plateau.

1342-937X/$ - see front matter © 2007 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.gr.2007.08.005 H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138 127

Fig. 2. (a) Tectonic units of the West Kunlun orogen in which the Paleozoic and Mesozoic granites are shown (NKT: the North Kunlun Terrane, SKT: the South Kunlun Terrane, KTT: the Karakorum–Tianshuihai Terrane; ①: the ca. 470 Ma Yierba I-type granodiorite pluton (Yuan et al., 2002); ② the Yixiekegou volcanic series, a member of the Kudi ophiolite; ③ the ca. 405 Ma North Kudi A-type granite (Yuan et al., 2002); ④ the Kudi gneiss (Xiao et al., 2005); ⑤ ultramafic–mafic complex, a member of the Kudi ophiolite; ⑥ the ca. 505 Ma Kangxiwa gneissic granodiorite pluton (Zhang et al., 2007a,b); ⑦ the Kangxiwa gneiss (Zhang et al., 2007a,b). (b) Geological map of the Buya appinite–granites consisting more than ten stocks along an east–west-trending zone, sharing similar color, texture and petrography;

Pt2kl—the Mesoproterozoic Kalakashi Group; Pt2al—the Mesoproterozoic Ailiankate Group; Pz2–Mz—lower Paleozoic to Mesozoic strata. (c) A detailed map showing the structure of one pluton from the Buya appinite–granites (the appinite enclaves are not shown in scale).

Western Kunlun Orogen (WKO), a 1000 km long early temporal framework of the early Paleozoic tectonic evolution in Paleozoic mountain belt located along the northern periphery the WKO. of the Tibetan plateau, connected with the Pamir syntaxis to the west and the Altyn-East Kunlun Orogen to the east (Fig. 1)isof 2. Regional geology and petrography considerable importance in understanding the reconstruction of paleo-Asia because it occupies a key tectonic position between The WKO was formed by multiple stages of terrane accretions the Tarim block to the north and the Tethyan domain to the south along the southwestern margin of the Tarim craton (Dewey et al., (Gao and Reiner, 2000; Xiao et al., 2001; Wang et al., 2001; Xiao et al., 2005; Yang et al., 2007). Previous studies have identified three types of the early Paleozoic granites in the WKO, i.e., the oceanic ridge granites (e.g., the Aoyitake granites, Jiang et al., 1999), subduction-related granites (e.g., the ca. 471 Ma Yierba granites, Yuan et al., 2002) and the post-orogenic A-type granites (e.g., the ca. 405 Ma north Kudi A-type granites) (Yuan et al., 2002). However, the petrotectonic in the WKO needs further investigations because little is known for the magmatic rocks during much of the Ordovician and Silurian time (Yuan et al., 1999; Jiang et al., 1999; Xiao et al., 1999; Yuan et al., 2002; Jiang et al., 2002; Xiao et al., 2002, 2005). In this contribution we report the petrography, age, elemental and Nd isotopic geochemistry of the early Paleozoic Buya high Ba–Sr granites in the WKO along the northern periphery of the Tibet Plateau, with the aims of (1) characterizing its Fig. 3. Photo of an appinite enclave in the Buya granite indicating magma mingling petrogenesis and (2) reconstructing a more detailed spatio- between the appinite and the granite. The diameter of the coin is about 2 cm. 128 H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138

Table 1 SHRIMP U–Pb zircon data for the Buya granite (sample KL018) Spots U (ppm) Th (ppm) Th/U f 206 206Pb 238U± 207Pb/235U± 207Pb/206Pb± Age Age 206Pb/238U± 207Pb/206Pb± 18-3.1 1344 165 0.12 1.1 0.1144 0.0031 1.087 0.033 0.0689 0.0008 698 18 896 23 18-5.1 3594 739 0.21 1.2 0.0730 0.0031 0.546 0.029 0.0542 0.0015 454 18 380 62 18-6.1 3876 587 0.15 1.2 0.0619 0.0023 0.510 0.027 0.0597 0.0019 387 14 592 72 18-8.1 2496 427 0.17 1.1 0.0723 0.0041 0.546 0.037 0.0548 0.0017 450 25 402 69 18-8.2 1975 168 0.08 1.8 0.0969 0.0043 0.813 0.082 0.0608 0.0052 596 25 633 194 18-9.1 3962 767 0.19 3.9 0.0631 0.0023 0.472 0.020 0.0542 0.0009 395 14 380 39 18-11.2 1047 299 0.29 1.1 0.1468 0.0069 1.320 0.095 0.0652 0.0032 883 39 781 107 18-14.1 2542 729 0.29 1.4 0.0691 0.0020 0.591 0.094 0.0620 0.0095 430 12 675 365 18-15.1 683 161 0.24 3.5 0.1131 0.0047 0.835 0.240 0.0535 0.0150 691 27 351 796 18-16.1 769 554 0.72 1.0 0.1596 0.0044 1.497 0.055 0.0680 0.0015 955 24 869 46 18-20.1 1278 269 0.21 2.0 0.0710 0.0024 0.549 0.023 0.0561 0.0011 442 14 456 44 18-22.1 1152 322 0.28 1.0 0.0658 0.0031 0.426 0.050 0.0470 0.0048 411 19 48 227 18-23.1 1199 436 0.36 7.0 0.0695 0.0045 0.536 0.121 0.0559 0.0113 433 27 449 449 18-26.1 1245 279 0.22 1.0 0.0691 0.0053 0.549 0.117 0.0562 0.0123 431 29 452 461 18-27.1 2195 534 0.24 2.1 0.0699 0.0041 0.529 0.241 0.0631 0.0037 437 21 684 175 f 206: percentage of common 206Pb in total 206Pb.

1988; Pan and Wang, 1994; Xiao et al., 1999, 2002, 2005; Zhang minor amount of biotite (2–5%) and hornblende (b1%). et al., 2007a)(Fig. 1), i.e., the late Mesoproterozoic to early Accessory minerals include apatite, zircon, titanite, allanite, and Neoproterozoic orogenic belt in northern Kunlun (also known as Ti–Fe oxides. Porphyritic alkali-feldspar granites in widths of the northern Kunlun Terrane, NKT) possibly related to the 20–50 m occur on the peripheries of several plutons which assembly of the Rodinia supercontinent (Zhang et al., 2003a,b, gradually change into massive, even-grained alkali-feldspar 2007a), the early Paleozoic (the “Caledonian-aged” in most granite (Fig. 2c). The porphyritic granites have slightly higher Chinese literatures) southern Kunlun orogenic belt (also known as proportion of orthoclase. Large orthoclase phenocrysts, usually the southern Kunlun Terrane, SKT), and the late Paleozoic to several centimeters in size, show well-developed perthite Mesozoic Karakorum–Tianshuihai orogenic belt (or the Kar- exsolution, and contain inclusions such as plagioclase, anhedral akorum–Tianshuihai Terrane; Xiao et al., 1999, 2002, 2005) quartz, biotite and hornblende. Appinite enclaves in dimensions (Fig. 2a). of 20–30 cm×20–30 cm are common in the periphery belts of The Buya granites, located to the south of Hetian City in the several plutons (Figs. 2c, 3). The appinites are composed of NKT (Fig. 2b), consist of about ten plutons sharing similar plagioclase (40–55%, An≈30), pyroxene (1–2%), hornblende petrographic features. All the plutons intrude into the Mesopro- (40–45%), biotite (1–5%) and quartz (1–2%). Variable amounts terozoic metamorphic rocks (the Kalakashi Group or the Ailian- of hornblende formed at the expense of pyroxene. Hornblende kate Group) and were unconformably covered by the Lower shapes from euhedral to anhedral, sometimes with enclosing Carboniferous strata (Zhang et al., 2007a). The main rock types biotite. Large orthoclase phenocrysts are present in the matrix of are alkali-feldspar granite or K-feldspar granite consisting of appinites (Fig. 3). Minor and accessory minerals are ubiquitous, orthoclase (30–40%), perthite (35–45%), quartz (30–35%) and especially euhedral titanite and apatite but also zircon and allanite.

Table 2 Hornblende 40Ar/39Ar geochronology data for the Buya granite (sample KL018) 40 39 (36 39 37 39 38 39 40 39 a39 − 14 39 T (°C) ( Ar/ Ar)m Ar/ Ar)m ( Ar/ Ar)m ( Ar/ Ar)m Ar/ Ar Ar (10 mol) Ar(Cum)(%) Age (Ma) ±1σ (Ma) 500 65.4 0.1621 1.4218 0.0616 17.6329 24.4 0.43 342.0 66 600 30.3 0.0759 1.3911 0.0421 7.9367 12.8 0.66 162.0 31 700 27.3 0.0466 3.4392 0.0271 13.8356 32.5 1.23 273.6 9.1 800 28.3 0.0328 2.2682 0.0251 18.7691 41.5 1.97 362.0 9.0 900 20.7 0.0097 0.6579 0.0167 17.8757 159 4.78 346.3 3.8 980 20.9 0.0073 1.6290 0.0165 18.8537 166 7.72 363.5 4.1 1060 22.1 0.0074 3.4226 0.0166 20.2479 208 11.39 387.6 4.2 1100 23.2 0.0078 7.3991 0.0164 21.5578 411 18.68 410.0 4.4 1130 22.7 0.0049 7.8483 0.0215 21.9315 1887 52.09 416.4 4.1 1160 22.9 0.0036 7.5774 0.0169 22.4785 1410 77.07 425.7 4.1 1190 22.7 0.0042 8.1442 0.0172 22.2086 532 86.50 421.1 4.7 1220 22.8 0.0047 8.5656 0.0177 22.1686 391 93.42 420.4 4.2 1270 23.8 0.0079 7.8592 0.0168 22.1927 198 96.93 420.8 4.9 1400 26.9 0.0182 6.5591 0.0160 22.0767 173 100.00 418.9 5.1 Items with subscript m represent analyzed isotope ratios. a40Ar/39Ar is the ratios between the radiogenic 40Ar and 39Ar. H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138 129

3. Analytical methods (CL) images to study their inner structures. Measurements of U, Th and Pb isotopes were conducted using the SHRIMP II ion A ∼5 kg granite sample (KL18, at the same location of the microprobe at the Beijing SHRIMP Center, Chinese Academy of chemical sample KL18-3) was collected from the Buya granites Geological Sciences, using operating and data processing pro- (79°57′32″ E, 36°28′25″ N) for geochronological analysis. cedures similar to those described in Williams (1988). However, Mineral separation was carried out first using conventional due to the extremely high uranium contents of the zircons, the magnetic and density techniques to concentrate the non-mag- acceptable analytical results are slightly scattered (Table 1 and netic, heavy fractions. A representative selection of zircons was detailed discussions later in the paper). To further constrain the then extracted by hand-picking under a binocular microscope. crystallization age of the pluton, a hornblende fraction was Zircon grains, together with TEMORA zircon standard selected from the same sample (KL018) for 40Ar/39Ar analysis at (206Pb/238U=0.06683 corresponding to 417 Ma), were cast the Ar–Ar Geochronological Laboratory in the Chinese into an epoxy mount, which was then polished to section the Academy of Geological Sciences (detailed analytical procedures crystals for analysis. Zircons were documented with transmitted can be found in Wang et al., 1992). The analytical results are and reflected light micrographs as well as cathodoluminescence listed in Table 2.

Table 3 Major and trace elements compositions of the Buya granite Sample 27y-1 27y-2 27y-4 27y-5 27y-6 27y-7 KL18-3 KL19-1 KL19-2 KL20-1 KL20-2 KL21-1 KL21-2 KL21-4 Major elements (%)

SiO2 72.10 72.68 72.20 71.99 72.15 72.77 71.87 72.23 71.18 72.09 71.92 54.70 69.77 55.39 TiO2 0.21 0.20 0.20 0.19 0.18 0.17 0.15 0.21 0.21 0.14 0.16 0.90 0.37 0.80 Al2O3 15.40 14.83 15.49 15.29 15.09 15.06 14.93 14.88 15.59 15.20 15.12 14.01 14.29 14.60 Fe2O3 1.16 1.24 1.18 1.18 1.20 1.09 1.47 1.41 1.37 1.21 1.20 7.68 2.91 7.67 MnO 0.03 0.03 0.03 0.03 0.02 0.02 0.02 0.02 0.01 0.01 0.01 0.15 0.04 0.15 CaO 0.84 0.89 0.90 1.04 0.82 0.88 0.87 0.80 0.86 0.69 0.63 7.84 1.99 6.90 MgO 0.30 0.28 0.25 0.24 0.35 0.26 0.17 0.27 0.22 0.08 0.11 6.14 1.06 5.93

K2O 4.79 4.92 4.77 4.73 5.10 4.49 4.44 4.98 5.23 4.83 4.64 2.56 5.04 2.46 Na2O 4.58 4.58 4.43 4.66 4.30 4.31 4.84 4.33 4.49 4.58 5.08 3.79 3.98 4.26 P2O5 0.05 0.04 0.04 0.04 0.04 0.03 0.02 0.04 0.05 0.01 0.02 0.98 0.13 0.60 LOI 0.68 0.39 0.36 0.49 0.58 0.38 0.70 0.14 0.21 0.55 0.59 0.70 0.31 0.43 Total 100.13 100.08 99.85 99.88 99.81 99.45 99.48 99.29 99.44 99.40 99.48 99.43 99.89 99.18 Mg# 34 31 30 29 37 32 19 28 24 11 15 61 42 61

Trace elements (ppm) La 51.4 46.3 36.6 35.5 44.6 29.8 27.3 48.7 47.7 24.8 24.1 161 68.0 74.6 Ce 88.1 82.7 61.2 59.3 81.2 53.8 44.9 78.4 77.2 45.7 43.9 296 114 143 Pr 9.20 9.19 7.57 7.16 8.76 6.28 5.47 9.69 9.24 4.83 4.65 35.63 14.52 17.36 Nd 29.0 29.6 26.8 25.8 27.9 20.7 19.5 33.3 33.8 15.2 14.7 119.8 55.4 60.3 Sm 4.45 4.91 4.33 4.23 4.39 3.43 3.53 4.92 5.11 2.32 2.45 18.08 9.48 9.68 Eu 0.90 0.95 0.75 0.74 0.93 0.70 0.59 0.86 0.87 0.44 0.42 3.82 1.81 2.01 Gd 2.40 2.51 2.14 1.91 2.46 1.83 1.91 2.12 2.01 1.18 1.26 9.22 5.12 6.01 Tb 0.30 0.34 0.28 0.27 0.31 0.23 0.26 0.27 0.29 0.15 0.18 1.14 0.70 0.76 Dy 1.46 1.66 1.29 1.19 1.49 1.17 1.28 1.15 1.21 0.85 0.89 5.08 3.34 3.58 Ho 0.27 0.30 0.22 0.20 0.25 0.20 0.22 0.18 0.18 0.16 0.15 0.76 0.55 0.60 Er 0.67 0.77 0.56 0.53 0.60 0.49 0.60 0.45 0.49 0.34 0.34 1.95 1.36 1.56 Tm 0.10 0.10 0.08 0.07 0.09 0.07 0.08 0.06 0.06 0.05 0.05 0.22 0.17 0.19 Yb 0.55 0.70 0.49 0.43 0.56 0.43 0.53 0.27 0.36 0.26 0.28 1.33 1.04 1.22 Lu 0.08 0.10 0.08 0.06 0.08 0.07 0.08 0.05 0.05 0.04 0.04 0.19 0.15 0.16 Rb 206 207 207 181.59 288.3 216 193 219 256 261 204 176 215 160 Sr 719 756 775 784 809 727 867 685 655 671 725 1009 1100 856 Ba 1253 1209 1189 1122 1433 1036 1265 1057 1148 1044 1567 674 1407 620 Th 24.5 26.7 21.5 24.3 22.3 21.2 28.3 24.1 28.1 20.9 22.2 45.6 27.8 24.1 Ta 1.33 1.46 1.30 1.33 1.39 1.55 1.30 0.94 1.12 1.11 1.15 1.30 1.35 1.03 Nb 18.7 22.7 19.2 20.7 16.0 14.1 16.9 10.7 12.3 12.0 15.6 21.2 18.9 15.6 Zr 147 148 141 149 171 134 143 151 158 122 131 197 216 165 Hf 4.22 4.89 4.33 4.63 4.83 4.19 4.04 4.03 4.28 3.79 4.12 5.00 5.82 4.28 Y 8.36 9.72 7.08 7.24 8.04 6.55 8.27 5.63 5.75 4.91 5.15 21.46 14.82 14.46 Ga 23.1 23.9 24.2 24.8 30.2 23.3 22.7 21.2 23.3 23.7 24.7 22.0 21.5 20.2 U 7.53 9.78 7.29 7.73 6.19 6.99 7.38 3.25 4.15 4.88 6.00 8.88 4.19 5.89 Cr 6.47 7.41 9.85 11.00 13.13 10.03 15.88 12.27 11.29 6.52 6.96 152 34.8 179 Ni 0.74 0.20 13.68 13.72 9.00 4.36 15.14 14.42 14.49 0.84 1.71 82.1 23.2 51.6 ⁎KL21-1 and KL21-4 are appinites, KL21-2 is the porphyritic alkalis-feldspar granite, and the others are even-grained alkali-feldspar granites. 130 H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138

Fourteen granite and appinite samples were analyzed for major corresponding to the La Jolla standard of 0.511860 (Tanaka and trace elements, and seven of the fourteen samples and two et al., 2000). Sm–Nd isotopic data are listed in Table 4. additional samples from the wall-rocks (the Kalakashi Group) were analyzed for Sm–Nd isotopic compositions. All the analyses 4. Results were carried out at the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. The major-element oxides were 4.1. Geochronology obtained using a Rigaku ZSX100e X-ray fluorescence (XRF) on fused glass beads following the analytical procedures similar to Zircon grains are mostly euhedral, 150–250 μm long, with those described by Li et al. (2006). Analytical precision is length to width ratios of 2–4. However, cracks and metamicti- between 1% and 5%. Trace elements were analyzed using a PE zation are seen in almost all zircons due to their high uranium Elan ICP-MS following the procedure described by Li et al. contents (Table 1, with the excluded spots having uranium up to (2000). About 50 mg sample power from each sample was 9000 ppm). A few zircons have kept blurry original euhedral dissolved in high-pressure Teflon bombs using an HF+HNO3 concentric zoning under CL. Twenty-eight analyses were mixture. An internal standard solution containing single element conducted on 26 zircons. Though we have very carefully Rh was used for monitoring signal drift during ion counting. The avoided the cracks and the intense metamict areas on the USGS standards BCR-1, W-2 and G-2 and the Chinese National zircons, about half of the analyzed results are rejected due to standards GSR-1 and GSR-3 were used for calibrating element very high common lead (20–40%). The remaining 15 analyses concentrations of the unknowns. In-run analytical precisions for have relatively lower common lead, U concentrations ranging most elements were generally better than 2–5%. The analytical between 683 ppm and 3962 ppm, Th between 161 ppm and results of major and trace elements are listed in Table 3. 739 ppm, and Th/U ratios between 0.17 and 0.36 except for spot Nd isotopes were determined using a Micromass Isoprobe 18-8.2 (Th/U=0.08). Among them, 7 analyses gave concordant multi-collector ICP-MS (MC-ICP-MS) following the procedure U–Pb results within analytical errors, and their weighted mean described by Li et al. (2004). Samples were taken up in 2% of 206Pb/238U ratios yields an age of 430±12 Ma (95% con- HNO3, and the aqueous solutions were introduced into the MC- fidence interval) (Fig. 4a). Two spots on the relatively crack-free ICPMS using a Meinhard glass nebulizer with an uptake rate of centers (spots 8.2 and 11.2) and other two on the rim of the less 0.1 ml/min. The inlet system was washed out for 5 min between metamict zircons (spots 3.1 and 16.1) yield relatively older analyses using high-purity 5% HNO3 followed by a blank ages. However, it is difficult to identify whether they are in- solution of 2% HNO3 from which the sample solutions were herited cores or xenocrysts due to their blurry CL images. prepared. The Isoprobe MC-ICPMS was operated in a static The hornblende separated from the same granite sample is mode. Measured 143Nd/144Nd ratios were normalized to fresh and of high purity (N99%). The apparent 39Ar/40Ar ages at 146Nd/144Nd=0.7219. The reported 143Nd/144Nd ratios are high temperature stages (1100–1600 °C) representing 81.3% adjusted relative to the Shin Etsu JNdi-1 standard of 0.512115, of total 39Ar released are indistinguishable within errors, with a

Table 4 Sm–Nd isotope compositions of the Buya granite and related rocks in West Kunlun 147 144 143 144 Sample Sm (ppm) Nd (ppm) Sm/ Nd Nd/ Nd±2σm TDM (Ga) T2DM (Ga) ɛNd(T) Granitic samples from the Buya granites (ca. 430 Ma) KL20-1 2.32 15.18 0.093 0.511863±0.000010 1.62 2.02 −9.56 KL21-2 9.48 55.37 0.104 0.511954±0.000008 1.66 1.93 −8.39 2027Y-1 4.45 28.99 0.093 0.511918±0.000013 1.55 1.94 −8.50 2027Y-2 4.91 29.57 0.101 0.511875±0.000009 1.72 2.04 −9.76 2027Y-4 4.33 26.75 0.098 0.511834±0.000010 1.73 2.09 −10.41

Appinites in the Buya pluton (ca. 430 Ma) KL21-1 18.08 119.79 0.092 0.512005±0.000011 1.43 1.80 −6.72 KL21-4 9.68 60.32 0.098 0.512075±0.000009 1.41 1.72 −5.67

Wall-rocks (the Kalakashi Group, T=1000 Ma) KL-1 5.5 30.93 0.108 0.511675±0.000009 2.12 2.31 −5.19 KL-2 6.08 34.52 0.107 0.511620±0.000008 2.18 2.37 −6.11

Metamorphosed basaltic rocks from the Ailiankate Group (Zhang et al., 2003a) 2.12–3.20 6.97–11.07 0.148–0.194 0.512538–0.512886 1.42–2.00 1.34–1.98 4.44–6.04

Neoproterozoic mafic dykes and basalts in the NKT (Zhang et al., 2004a) 1.81–5.03 8.05–20.9 0.126–0.143 0.512101–0.512472 1.31–2.02 1.35–1.86 −4.49–2.91

2.3–2.4 Ga granitic intrusive complex in the NKT (Zhang et al., 2007b) 3.42–18.47 18.66–124.5 0.075–0.116 0.510541–0.511271 2.76–3.15 2.71–3.17 −0.92 to −4.71 H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138 131

U–Pb age and hornblende 39Ar/40Ar age results, we suggest that the Buya granites were crystallized at ca. 430 Ma.

4.2. Major and trace elements

The Buya granite samples have relatively constant SiO2 contents of between 69.8% and 72.7%, and variably low contents of TiO2 (0.14–0.37%), P2O5 (0.01–0.13%), MgO (0.08–1.06%), CaO (0.63–1.99%), Fe2O3 (1.09–2.91), Cr (b35 ppm) and Ni (b23 ppm). Their A/CNK values range from 0.91 to 1.11, indicating a metaluminous to weakly peraluminous nature (Fig. 5a). They are rich in total alkalis (Na2O+K2O=8.80– 9.92% and Na2O/K2O=0.8–1.1) that decrease with increasing SiO2 and plot into the alkaline granite field on the TAS diagram (Fig. 5b). They have total REE contents ranging from 106 ppm to 275 ppm and intensive fractionation between LREE and HREE with (La/Yb)N =37–96 but insignificant to medium negative Eu anomalies (δEu=0.70–0.89) (Fig. 6a). The granite samples are enriched in Sr (655–1100 ppm) and Ba (1044–1567 ppm) and depleted in Nb, Ta, P and Ti, with very high Sr/Y ratios (71–141). On the trace element spidergram of Sun and McDonough (1989), all the granite samples show negative anomalies in Nb, Ta, P and Ti (Fig. 6b). Two appinite samples are also enriched in total alkalis with Na2O+K2O between 6.35% and 6.72% and Na2ONK2O

Fig. 4. (a) U–Pb zircon concordia diagram for the Buya appinite–granites. The concordant age of 430±12 Ma is interpreted as the crystallization age of the granite. (b) and (c): 40Ar/39Ar incremental heating age spectrum of hornblendes from the Buya granite and reverse isochronal age of the main spectrum.

weighted mean of 420.6±3.6 Ma (Fig. 4b). This age is con- sistentwiththereverse39Ar/36Ar vs. 40Ar/36Ar isochron age of 420±7.5 Ma with an initial 40Ar/36Ar value of 279±52 comparable with the atmospheric 40Ar/39Ar ratio of 295.5 (Fig. 4c). Therefore, the hornblende 39Ar/40Ar age of ∼420 Ma Fig. 5. SiO2 vs. K2O+ Na2O classification diagram (a), and A/NK vs. A/CNK constrains the minimum age for the crystallization of the granite plot (b) (Maniar and Piccoli, 1989) showing the weakly metaluminous to weakly ∼ considering the Ar blocking temperature of 500 °C in peraluminous nature of the Buya granite. A=Al2O3,N=Na2O, K=K2O, hornblende (Dodson, 1973). Combining the zircon SHRIMP C=CaO (all in molar proportions). 132 H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138

(Table 3). They have higher TiO2,P2O5,Fe2O3, MgO, REE and 5. Discussions most other trace elements than those of the granite samples. Their REE and trace element patterns are similar to but lies on 5.1. Petrogenesis of the appinite top of those of the granite samples with insignificant negative anomalies of Eu and P (Fig. 6a, b). The appinite samples are high in Mg# (∼61), Cr (150– 180 ppm) and Ni (52–80 ppm) contents (Table 3), similar to the 4.3. Sm–Nd isotope compositions Cenozoic magnesian andesites and the Archaean high-Mg diorites (e.g. Yogodzinski et al., 1994; Smithies and Champion, Sm–Nd isotope compositions as well as the calculated ɛNd(T) 2000; Wu et al., 2003). These features argue against the appinite and Nd model ages TDM and T2DM for the Buya granite and their being derived solely from partial melting of any crustal Precambrian wall-rocks, using the same formulation of Li et al. materials though they possess pronounced negative initial (2003), are presented in Table 4. The granite samples have a ɛNd values (−6.5). On the other hand, they have high Sr (860– narrow range of 147Sm/144Nd (0.0930–0.1010) and 143Nd/144Nd 1000 ppm), Ba (620–670 ppm), total REE (320–650 ppm) (0.511834–0.511954) ratios, corresponding to ɛNd(T )values contents and high Sr/Y (47–60) and (La/Yb)N (44–87) ratios, (T=430 Ma) ranging from −10.4 to −8.4. Their 147Sm/144Nd sharing the characteristics of adakitic rocks (Yogodzinski et al., ratios are clearly lower than the average continental crust value of 1994). Although the interaction between the subducted slab- 0.118 (Jahn and Condie, 1995), indicating significant fraction- derived melts and the mantle wedge above the slab, a typical ation between Sm and Nd. Therefore, the two-stage Nd model genesis for adakites, could properly explain the high Mg#, high ages (T2DM), in the range of 1.9 Ga to 2.0 Ga, are thought to be Cr and Ni contents, and high Sr/Y and (La/Yb)N ratios of these more reliable than the single-stage model ages (TDM)ofbe- appinites (e.g., Yogodzinski et al., 1994; Kelemen, 1995; Stern tween 1.55 and 1.73 Ga (Li et al., 2003). Two appinite samples and Kilian, 1996), such a model is inconsistent with their Nd have constant 147Sm/144Nd (0.092–0.098) and 143Nd/144Nd isotope composition because slab-derived magnesian andesites (0.512005–0.512075) ratios, corresponding to higher ɛNd(T) (or diorites) always possess MORB-like Nd isotopic composi- (−5.7 to −6.7) and younger T2DM (∼1.4 Ga) ages than those of tions (Defant and Drummond, 1990). the granite samples. An alternative model for the genesis of the appinites is that they are generated by partial melting of an enriched lithospheric mantle with a garnet-bearing residue (Hirose, 1997) to account for their magnesian appinitic characteristic and unradiogenic Nd isotope compositions. Moreover, their high Ba/Nb (31–40) and Th/Yb (19–34) ratios and significantly negative anomalies of Nb and Ta relative to La (Nb/La=0.13–0.21) (Fig. 6b) strongly argue for the case that the enrichment of their mantle source resulted from metasomatism by the subduction-related materials (possibly some matured sediments included) rather than pure slab-derived fluid or fluid from the asthenospheric mantle (Pearce, 1983; Hofmann et al., 1986; Weaver, 1991; Aldanmaz et al., 2000). Crystal fractionation of pyroxene and olivine and crustal assimilation could diminish both the Cr and Ni contents and the Mg# quickly. Hence, considering the high Mg# (∼61), Cr (150– 180 ppm) and Ni (52–80 ppm) contents of the appinites, their chemical compositions likely represent their primary magma, indicating a low degree of partial melting that is consistent with their high total alkalis (N6.0%).

5.2. Petrogenesis of the Buya granites

Chemical compositions of the Buya granites exclude that they belong to S- and M-types. Their ferroan and alkaline affinities share some characteristics of the A-type granites (Frost et al., 2001). Nevertheless, A-type granites generally contain high Zr and other HFSE due to the high-temperature, low- pressure partial melting of their source rocks. On the contrary, the Buya granites have low Zr contents (134–216 ppm), high Fig. 6. Chondrite-normalized REE patterns (a) and primitive mantle-normalized Sr/Y and (La/Yb)N ratios indicating a high-pressure partial incompatible-element spidergrams (b) for the granites and appinites. The melting, which is inconsistent with that of the A-type granites. normalization values are from Sun and McDonough (1989). Their high LREE, LILE and low HREE and HFSE contents and H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138 133

related high Sr/Y and (La/Yb)N ratios are similar with those of adakites or adakitic rocks (Defant et al., 2002; Wang et al., 2006), however, their high alkali contents is in contrast with the calc-alkaline characteristics of those adakitic rocks. “High Ba–Sr granites” (Tarney and Jones, 1994)are becoming widely recognized in recent years (e.g., Fowler and Henney, 1996; Fowler et al., 2001; Qian et al., 2002; Chen et al., 2004). They could be calc-alkaline or alkaline in composition with the trace elemental affinities to adakitic rocks (Tarney and Jones, 1994; Chen et al., 2004; Hou et al., 2004). Thus, it is quiet plausible to classify the Buya granites as the high Ba–Sr granites based on their petrography and elemental geochemistry. The petrogenesis of the high Ba–Sr granites are still matters for debate. Different petrogenic mechanisms have been proposed, including the subduction of ocean plateau, underplating of high Ba–Sr mafic magma, lithospheric enrichment by carbonatitic melts, mixing between mafic magma from enriched mantle and crust-derived granitic melts and crystal fractionation from the enriched mantle-derived appinite accompanied by minor crustal contamination (e.g., Tarney and Jones, 1994; Fowler et al., 2001; Qian et al., 2002; Chen et al., 2004, 2005). Although the granites and appinites share similar REE and trace elements distribution patterns (Fig. 6), the sharp contacts (Fig. 3), mismatch on the volumes and Nd isotope compositions, and a “chemical composition gap” between them demonstrate that the granites were unlikely formed by crystal fractionation of the appinitic magmas (Rapp et al., 2002; Macpherson et al., 2006). Moreover, REE distribution patterns (Fig. 6a), high alkalis, Sr/Y and (La/Yb)N ratios (Fig. 7) and unradiogenic Nd isotope compositions of the granites preclude their derivation from partial melting of either the metamorphic clastic rocks of the regional Mesoproterozoic Kalakashi Group or the Paleoproterozoic intrusive complex (Table 4)(Zhang et al., 2006; 2007b), or the subducted slab or ocean plateau (Defant and Drummond, 1990; Kay and Kay, 1993; Stern and Kilian, 1996; Martin et al., 2005). Several lines of evidence should be taken into account in the discussion of the genesis of the granites: (1) Numerous studies (Rapp and Watson, 1995; Rapp et al., 1999; Tate and Johnson, 2000; Petford et al., 1996; Petford and Gallagher, 2001; Rapp et al., 2002; Wang et al., 2006) have demonstrated that mafic

Fig. 7. Sr/Y vs. Y, (La/Yb)N vs. YbN diagrams after Defant and Drummond (1990) and Sr/Yvs. Mg# diagram showing the fractional crystallization trends of the Buya granites (after Chen et al., 2004, 2005, see details in the text). Fig. 8. Nd isotope evolution trends of the Buya granite and related rocks in the NKT (see details in the text). 134 H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138

among the analyzed granite samples, sample KL21-2, which was collected from the proximal location of the appinite enclaves (Fig. 2c), has the highest TiO2,Fe2O3, MgO, CaO, P2O5 and lowest SiO2 contents (Table 3). In addition, its REE and most trace element contents are transitional between those of granites and appinites (Fig. 6); (3) Despite being collected from different plutons, all the studied granite samples have high # SiO2 and alkalis contents and low Mg (10–42), Cr (7–35 ppm) and Ni (0.2–23 ppm) contents in comparison with those high Ba–Sr granites formed by magma mixing between mafic and silicic end members (Fowler and Henney, 1996; Fowler et al., 2001; Chen et al., 2004, 2005; Qian et al., 2002), further reflecting relatively minor addition of the appinitic melts into Fig. 9. Mg# vs. initial Nd values showing the crystal fractionation effect. the granitic magma (Qian et al., 2002; Chen et al., 2004; Wang et al., 2006). Thus, all of the above evidences suggest that the crustal rocks can melt to produce liquids with high Sr/Yand (La/ Buya granites was most likely generated by partial melting of Yb)N ratios at sufficient depth (≥40 km, i.e. ≥1.2 GPa) where the mafic lower crust at high pressure leaving a residual garnet garnet is stable within the residual assemblage (e.g., residues of (e.g., Atherton and Petford, 1993; Muir et al., 1995; Petford et garnet–amphibolite, amphibole-bearing ecolgite and/or ecol- al., 1996) with involvement of minor amount of the appinitic gite), a model consistent with the low Mg#, Cr, Ni contents and magma. Mesoproterozoic Nd modal ages of the Buya granites; (2) In the North Kunlun Terrane, basaltic rocks include the Magma mingling between the appinitic and granitic melts is Mesoproterozoic metamorphic basaltic rocks of the Ailiankate clearly seen on outcrops (Fig. 3), similar to many high Ba–Sr Group and possible Neoproterozoic underplated mafic rocks granites from the British Caledonian province (Fowler and (Table 4)(Zhang et al., 2003a, 2004a, 2006). However, Nd Henney, 1996; Fowler et al., 2001) and North China (Chen et isotopic compositions of these mafic rocks are inconsistent with al., 2004, 2005). Nevertheless, their sharp contact indicates that those of the Buya granite (Fig. 8), and older mafic lower crust they possibly mingled to each other at a semi-solidification state components such as the mafic enclaves from the 2.3–2.4 Ga and material exchange between them was minor except the intrusive complex (Zhang et al., 2007b) were possibly a major porphyritic granites on the periphery of several plutons, e.g., source for the Buya and neighboring granites.

Fig. 10. Trace elements bivaration diagrams showing the fractional crystallization of allanite, apatite, hornblende and oxides (see details in the text). H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138 135

Table 5 Geochronological data of rocks related to the Caledonian event in the West Kunlun orogen Rock type Target mineral Analyzed method Age (Ma) References Gabbro dykes from the Kudi Zircon SHRIMP 525±2.5 Zhang et al. (2004b) ophiolite Quartz-bearing gabbro in the Kudi ophiolite Zircon SHRIMP 510±4 Xiao et al. (2003) Gabbro in the Kudi ophiolite Zircon SHRIMP 502±1 Xiao et al. (2003) Andesite in Yixieke Zircon SHRIMP 492±9 Xiao et al. (2005) Granodiorite in Kangxiwa Zircon SHRIMP 505±10 Zhang et al. (2007a) Gabbro in the Qimanyute ophiolite Zircon TIMS 526±1 (single spot) Han et al. (2002) The 128 granodiorite (arc-type) Zircon TIMS 471±5 Yuan et al. (2002) The Kudi shear zone Hornblende Ar–Ar 452±5 Zhou et al. (2000) The Kudi shear zone Biotite Ar–Ar 428±2 Zhou et al. (2000) The Kudi gneiss Zircon SHRIMP 398–1345 Xiao et al. (2005) The Kangxiwa gneiss (in the SKT) Zircon SHRIMP 420–450 (metamorphic ages) Xu et al. (2004) The Waqia gneiss (in the SKT) Zircon SHRIMP 400–460 (metamorphic ages) Zhang et al. (2007a) North Kudi A-type granite Zircon TIMS, SHRIMP 408±7, 404±3.1 (Xiao et al., 2005; Yuan et al., 2002) Gabbro in north Kudi Zircon SHRIMP 403±7 Xiao et al. (2005) The Buya high Ba–Sr granite Zircon SHRIMP 430±12 This study Hornblende Ar–Ar 422±6

The granitic rocks are characterized by constant initial ɛNd significant correlation between Sr and Ba and the minor values but variable Mg# values (Fig. 9), suggesting that its negative Eu anomaly of the granite has been observed, chemical compositions are mostly controlled by crystal plagioclase and alkali-feldspar crystal fractionation must have fractionation. On Sr/Y vs. Y and (La/Yb)N vs. YbN diagrams been insignificant. Of the minor or accessory minerals, P2O5 (Fig. 7a, b), the data follow the fractionation trend of pyroxene would monitor apatite, TiO2 titanite, Zr zircon and Ce allanite. and hornblende but not plagioclase (Chen et al., 2005), which Among them, positive correlations between Sm and P2O5,Nd was also evidenced by the negative correlation between Sr/Y and Ce, Rb and Rb/Sr have been observed (Fig. 10a,b,c). Those ratios and Mg# (Fig. 7c) because both minerals could reduce variations, combining the pronounced P and Ti troughs in the Mg# and increase Sr/Y ratios at the same time (Chen et al., trace elements distribution patterns (Fig. 6b), suggest that 2004, 2005). Considering their high SiO2 contents and the fact apatite and allanite crystal fractionation associated with minor that no pyroxene has been observed in thin sections, amount of oxides might be responsible for variations in most fractionation of hornblende, rather than pyroxene, was likely trace elements. dominant in the magmatic evolution. Plot of Cr vs. Ni exhibits a Concluded on the above analyses, the granites were most trend of biotite and oxides crystal fractionation (Fig. 10d). As no likely generated by partial melting of the mafic lower crust at high pressure, with minor addition of the appinitic magma from an enriched mantle and followed by crystal fractionations of hornblende, biotite and accessory minerals such as allanite, apatite and oxides.

Fig. 11. Spectrum of metamorphic zircon 206Pb/238U ages from paragneisses in the SKT and the Kudi area (original data are from Xu et al., 2004; Xiao et al., 2005; Zhang et al., 2007a,b), indicating the four stages of the early Paleozoic evolution of the Western Kunlun Terrane: I—ca. 500–460 Ma subduction stage; II—ca. 460–450 Ma collision stage; III—460–450–430 Ma crustal thickening stage; IV—ca. 430–400 Ma post-collision collapse (crustal thinning) stage. The ca. 430 Ma Buya high Ba–Sr granites represents the beginning of post-collision Fig. 12. Rb vs. (Y+Nb) plot after Pearce et al. (1984) and Pearce (1996), the ca. collapse. 405 Ma North Kudi A-type granite samples are also plotted (in grey cycle). 136 H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138

5.3. Tectonic interpretations

Controversies exist on the early Paleozoic tectonic evolution of the West Kunlun orogen (Sengör and Okurogullari, 1991; Jiang et al., 1992; Zhang et al., 1998; Jiang et al., 1999; Pan, 2000; Jiang et al., 2002; Xiao et al., 2002, 2005; Zhang et al., 2007a). Available ages from relevant igneous and metamorphic rocks there are listed in Table 5. The metamorphic age spectrum of paragneisses in the South Kunlun Terrane (SKT), using the data obtained by both the SHRIMP U–Pb zircon and the LA-ICP-MS U–Pb zircon methods (Xu et al., 2004; Xiao et al., 2005; Zhang et al., 2007a), is given in Fig. 11. The metamorphic age spectrum exhibits apices at ca. 500 Ma, ca. 450 Ma, 430 Ma and 400 Ma. As the early Paleozoic ophiolites in north belt of the WKO were dated Fig. 13. Cartoon showing the petrogenesis model of the Buya granites (see at 502–526 Ma (Table 5), it is convincible to deduce that ocean details in the text). ①—lithospheric mantle enriched by subducted materials; ridge extension was occurring till at ca. 500 Ma. The subduction ②—mafic magma rich in LREE and LILE derived from partial melting of the ③— of oceanic crust continued to at least ca. 470 Ma (the age of the enriched lithospheric mantle; magma mixing between the mafic magma from the enriched lithospheric mantle and the silicic magma from partial melting volcanic-arc Yierba grandiorite pluton; Yuan et al., 2002). The ca. of the lower crust; ④—Buya high Ba–Sr granites. 450 Ma 39Ar/40Ar hornblende age from the Kudi shearing zone makes it plausible that the NKT and the SKT amalgamated at this time and dextral east–west shearing deformation developed along 430 Ma through slab delamination (Figs. 11, 13). The ca. the Kudi suture zone (Zhou et al., 2000; Xiao et al., 2005). 405 Ma North Kudi A-type granites might represent an There is a consensus that high Ba–Sr granites are generally advanced post-orogenic extension stage. emplaced in extensional or non-compressional tectonic settings, which might be related to different tectonic settings, such as 6. Conclusions lithospheric extension and late- to post-orogenic gravitational collapse following an episode of crustal thickening (Fowler Based on the data and discussions above, we draw the and Henney, 1996; Fowler et al., 2001; Chen et al., 2004). In Rb following conclusions. (1) the Buya high Ba–Sr appinite–gra- vs. Nb+Y diagram of Pearce et al. (1984) and Pearce (1996) nites in the NKT was crystallized at ca. 430 Ma, the granitic (Fig. 12), the samples from the Buya granites are plotted at the rocks were likely derived from partial melting of the mafic boundary syn-collisional granites and volcanic-arc granites, lower crust at high pressure with a garnet gneiss residue and sharing the characteristics of the post-orogenic granites. In with minor addition of the appinitic magma, flowed by crystal combination with their alkaline affinities and the ca. 450 Ma fractionation of hornblende, biotite and accessory minerals like amalgamation between the NKT and the SKT, the Buya granites apatite, allanite and oxides. The appinite enclaves mingled in were most likely formed at post-orogenic tectonic environment. the granites were derived from low-degree partial melting of an Post-orogenic extension is always triggered by the delami- enriched lithospheric mantle metasomatized by the subduction nation of the subducted slab (Sylvester, 1998). Thus, we suggest, materials; (2) a plausible model for the formation of the Buya at ca. 430 Ma, the subducted slab may have begun to delaminate appinite–granites could be described as: subducted-slab dela- down into the asthenosphere, inducing an asthenospheric up- mination led to the upwelling of the asthenosphere, which welling (Fig. 13). Such an upwelling could have caused partial induced partial melting of the pre-metasomatized lithospheric melting of the lithospheric mantle previously metasomatized by mantle to form the alkaline appinitic magma, and underplating subducted materials, forming appinitic magma enriched in of the appinitic magma triggered partial melting of the mafic LREE and LILE. The underplating of such appinitic magma lower crust to form the silicic magma, the two end members under the lower crust could have triggered partial melting of the mingled to each other and then emplaced into the upper crust; mafic lower crust, forming a silicic magma. Mingling between (3) combining the results of this study and previous studies, we the appinitic magma and the silicic magma, followed by crystal suggest that the NKT and the SKT was amalgamated at ca. fractionation of mafic minerals (hornblende) and accessory 450 Ma, crust thickened during ca. 450–430 Ma, and slab minerals like apatite and allanite, may have led to the formation delamination occurred at ca. 430 Ma, with the Buya appinite– of the high Ba–Sr Buya granites (Fig. 13). granite representing the beginning of the “post-orogenic” stage. The high Ba–Sr Buya granites and the North Kudi A-type granites were crystallized at ca. 430 Ma (this study) and ca. Acknowledgements 405 Ma (Yuan et al., 2002), respectively. Thus, late early Paleozoic granites, combining with metamorphic ages reported We thank Y. Liu, S. Li and X. Liang for helping with major, in this area (Zhou et al., 2000; Xu et al., 2004; Xiao et al., 2005; trace elements and Nd isotope analyses, and Dr. P. Jian and Dr. W. Zhang et al., 2007a)(Fig. 11), suggest that after the Chen for assistance with SHRIMP and 39Ar/40Ar data acquisition. amalgamation between the NKT and the SKT by ca. 450 Ma, This work was supported by National Science Foundation of post-orogenic (or orogenic clappsing) stage started at ca. China (40421303, 40772123) and the Programme of Excellent H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138 137

Young Scientists of the Ministry of Land and Resources (granted Kelemen, P.B., 1995. Genesis of high Mg andesites and the continental crust. – to C. L. Zhang). This is TIGeR publication 73. Contributions to Mineralogy and Petrology 120, 1 19. Kusky, T., Li, J.H., Santosh, M., 2007. The Paleoproterozoic North Hebei Orogen: North China's collisional suture with the Columbia supercontinent. References Gondwana Research 12, 4–28. Li, X.H., Sun, M., Wei, G.J., Liu, Y., Lee, C.Y., Malpas, J.G., 2000. Aldanmaz, E., Pearce, J.A., Thirlwall, M.F., Mitchell, J.G., 2000. Petrogenetic Geochemical and Sm–Nd isotopic study of amphibolites in the Cathaysia evolution of late Cenozoic, post-collision volcanism in western Anatolia, Block, SE China: evidence for extremely depleted mantle in the Turkey. Journal of Volcanology and Geothermal Research 102, 67–95. Paleoproterozoic. Precambrian Research 102, 251–262. Atherton, M.P., Petford, N., 1993. Generation of sodium rich magmas from Li, X.H., Li, Z.X., Ge, W., Zhou, H., Li, W., Liu, Y., Wingate, M.T.D., 2003. newly underplated basaltic crust. Nature 362, 144–146. Neoproterozoic granites in South China: crustal melting above a mantle Chen, B., Jahn, B.M., Arakawa, Y., Zhai, M.G., 2004. Petrogenesis of the plume at ca. 825 Ma? Precambrian Research 122, 45–83. Mesozoic intrusive complexes from the southern Taihang Orogen, North Li, X.H., Liu, D.Y., Sun, M., Li, W.X., Liang, X.R., Liu, Y., 2004. Precise Sm– China Craton: elemental and Sr–Nd–Pb isotopic constraints. Contributions Nd and U–Pb isotopic dating of the super-giant Shizhuyuan polymetallic to Mineralogy and Petrology 148, 489–501. deposit and its host granite, Southeast China. Geological Magazine 141, Chen, B., Tian, W., Zhai, M.G., Arakawa, Y., 2005. Zircon U–Pb 225–231. geochronology and geochemistry of the Mesozoic magmatism in the Li, X.H., Li, Z.X., Wingate, M.T.D., Chung, S.L., Liu, Y., Lin, G.C., Li, W.X., Taihang Mountains and other places of the North China craton, with 2006. Geochemistry of the 755 Ma Mundine Well dyke swarm, implications for petrogenesis and geodynamic setting. Acta Geologica northwestern Australia: part of a Neoproterozoic mantle superplume beneath Sinica 21, 13–24 (in Chinese with English abstract). Rodinia? Precambrian Research 146, 1–15. Defant, M.J., Drummond, M.S., 1990. Derivation of some modern arc magmas Macpherson, C.G., Dreher, S.T., Thirlwall, M.F., 2006. Adakites without slab by melting of young subducted lithosphere. Nature 347, 662–665. melting: high pressure differentiation of island arc magma, Mindanao, the Defant, M.J., Xu, J.F., Kepezhinskas, P., Wang, Q., Zhang, Q., Xiao, L., 2002. Philippines. Earth and Planetary Science Letters 243, 581–593. Adakites: some variations on the theme. Acta Petrologica Sinica 18, 129–142. Maniar, P.D., Piccoli, P.M., 1989. Tectonic discrimination of granites. Dewey, J.F., Shackleton, R., Chang, C.F., 1988. The tectonic evolution of the Geological Society of America Bulletin 101, 635–643. Tibetan Plateau. Philosophical Transactions of the Royal Society of London, Martin, H., Smithies, R.H., Rapp, R., Moyen, J.F., Champion, D., 2005. An Series A: Mathematical and Physical Sciences 327, 379–413. overview of adakite, tonalite–trondhjemite–granodiorite (TTG) and sanu- Dodson, M.H., 1973. Closure temperature in cooling geochronological and kitoid: relationships and some implications for crustal evolution. Lithos 79, petrological system. Contributions to Mineralogy and Petrology 40, 1–24. 259–274. Metcalfe, I., 2006. Paleozoic and Mesozoic tectonics and paleogeography of Fowler, M.B., Henney, P.J., 1996. Mixed Caledonian appinite magmas: East Asian crustal fragments: the Korean Peninsula in context. Gondwana implications for lamprophyre fractionation and high Ba–Sr granite genesis. Research 9, 24–46. Contributions to Minerlogy and Petrology 126, 199–215. Muir, R.J., Weaver, S.D., Bradshaw, J.D., Eby, G.N., Evans, J.A., 1995. Fowler, M.B., Henney, P.J., Darbyshire, D.P.F., Greenwood, P.B., 2001. Geochemistry of the Cretaceous separation point batholith, New Zealand: Petrogenesis of high Ba–Sr granites: the Rogart pluton, Sutherland. Journal granite magmas formed by melting of mafic lithosphere. Journal of of Geological Society, London 158, 521–534. Geological Society, London 152, 689–701. Frost, B.R., Arculus, R.J., Barnes, C.G., Collins, W.J., Ellis, D.J., Frost, C.D., Pan, Y.S., 2000. Geological Evolution of the Karakorum–Kunlun Mountains 2001. A geochemical classification of granitic rock suites. Journal of (in Chinese). Science Press, Beijing, pp. 324–392. Petrology 42, 2033–2048. Pan, Y.S., Wang, Y., 1994. Tectonic evolution along the geotraverse from Gao, J., Reiner, K., 2000. Eclogite occurrences in the southern Tianshan high- Yecheng to Shiquanhe (in Chinese). Acta Geologica Sinica 68, 295–307. pressure belt, Xinjiang, Western China. Gondwana Research 3, 33–38. Pearce, J.A., 1983. Role of sub-continental lithosphere in magma genesis at active Han, F.L., Cui, J.T., Ji, W.H., Li, H.P., Hao, J.W., 2002. Discovery of the continental margins. In: Hawkesworth, C.J., Norry, M.J. (Eds.), Continental Qimanyute ophiolite in the Western Kunlun and its geological significance. Basalts and Mantle Xenoliths, Shiva. Cheshire, UK, pp. 230–249. Geological Bulletin of China 21, 573–578 (in Chinese with English Pearce, J.A., 1996. Sources and settings of granitic rocks. Episodes 19, abstract). 120–125. Hirose, K., 1997. Melting experiments on lherzolite KLB-1 under hydrous Pearce, J.A., Harris, N.B.W., Tindle, A.G., 1984. Trace element discrimination conditions and generation of high-magnesian appinitic melts. Geology 25, diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology 42–44. 25, 956–983. Hofmann, A.W., Jochum, K.P., Seufert, M., White, W.M., 1986. Nb and Pb in Petford, N., Gallagher, G., 2001. Partial melting of mafic (amphibolitic) lower oceanic basalts: new constrains on mantle evolution. Earth and Planetary crust by periodic influx of basaltic magma. Earth and Planetary Science Science Letters 79, 33–45. Letters 193, 483–499. Hou, Z.Q., Gao, Y.F., Qu, X.M., Mo, X.X., 2004. Origin of adakitic intrusives Petford, N., Atherton, M.P., Halliday, A.N., 1996. Rapid magma production generated during mid-Miocene east–west extension in southern Tibet. Earth rates, underplating and remelting in the Andes: isotopic evidence from and Planetary Science Letters 220, 139–155. northern-central Peru (90–110s). Journal of Southern America Earth Sciences Jahn, B.M., Condie, K.C., 1995. Evolution of the Kaapvaal Craton as viewed 9, 69–78. from geochemical and Sm-Nd isotopic analyses of intracratonic pelites. Qian, Q., Chung, S.L., Li, Y.T., Wen, D.R., 2002. Geochemical characteristics Geochimica et Cosmochimica Acta 59, 2239–2258. and petrogenesis of the Badaling high Ba–Sr granites: a comparison of Jiang, C.F., Yang, J.S., Feng, B.G., 1992. Opening and Closing Tectonics of igneous rocks from North China and Dabie–Sulu Orogen. Acta Geologica Kunlun Mountains. Geological Publishing House, Beijing, pp. 47–68. Sinica 18, 275–292 (in Chinese with English abstract). Jiang, Y.H., Rui, X.J., Hou, J.R., Guo, K.Y., Yang, W.Z., 1999. Tectonic type of Rapp, R.P., Watson, E.B., 1995. Dehydration melting of metabasalt at 8– Caledonian granites and tectonic significance in the West Kunlun Mts. Acta 21 kbar: implications for continental growth and crust–mantle recycling. Petrologica Sinica 15, 105–115 (in Chinese with English abstract). Journal of Petrology 36, 891–931. Jiang, Y.H., Jiang, S.Y., Ling, H.F., Zhou, X.R., Rui, X.J., Yang, W.Z., 2002. Rapp, R.P., Shimizu, N., Norman, M.D., Applegate, G.S., 1999. Reaction Petrology and geochemistry of shoshonitic plutons from the western Kunlun between slab-derived melts and peridotites in the mantle wedge: orogenic belt, Xinjiang, northwestern China: implications for granite experimental constraints at 3.8 GPa. Chemical Geology 160, 335–356. geneses. Lithos 63, 165–187. Rapp, R.P., Xiao, L., Shimizu, N.M., 2002. Experimental constraints on the Kay, R.W., Kay, S.M., 1993. Delamination and delamination magmatism. origin of potassium-rich adakites in east China. Acta Petrologica Sinica 18, Tectonophysics 219, 177–189. 293–311. 138 H.-M. Ye et al. / Gondwana Research 13 (2008) 126–138

Santosh, M., Sajeev, K., Li, J.H., 2006. Extreme crustal metamorphism during Xiao, X.C., Wang, J., Su, L., Song, S.G., 2003. A further discussion of the Küda Columbia supercontinent assembly: evidence from North China Craton. ophiolite, West Kunlun, and its tectonic significance. Geology Review 22, Gondwana Research 10, 256–266. 745–750 (in Chinese with English abstract). Sengör, A.M.C., Okurogullari, A.H., 1991. The role of accretionary wedges in Xiao, W.J., Windley, B.F., Liu, D.Y., Jian, P., Liu, C.Z., Yuan, C., Sun, M., 2005. the growth of continents: Asiatic examples from Argand to plate tectonics. Accretionary tectonics of the Western Kunlun Orogen, China: a Paleozoic– Eclogae Geologicae Helvetiae 84, 535–597. Early Mesozoic, long-lived active continental margin with implications for Smithies, R.H., Champion, D.C., 2000. The Archaean high-Mg diorite suite: the growth of Southern Eurasia. The Journal of Geology 113, 687–705. links to tonalite–trondhjemite–granodiorite magmatism and implications for Xu, Z.Q., Qi, X.X., Liu, F.L., 2004. The Kangxiwar Caledonian khondalite the early Archaean crustal growth. Journal of Petrology 41, 1653–1671. series in West Kunlun, China, and its geological significance. Acta Stern, G.R., Kilian, R., 1996. Role of the subducted slab, mantle wedge and Geologica Sinica 78, 733–743 (in Chinese with English abstract). continental crust in the generation of adakites from the Austral Volcanic Yang, S., Li, Z.L., Chen, H.L., Santosh, M., Dong, C.W., Yu, X., 2007. Permian Zone. Contributions to Mineralogy and Petrology 123, 263–281. bimodal dyke of Tarim Basin; NW China: geochemical characteristics and Sun, S.S., McDonough, W.F., 1989. Chemical and isotopic systematics of tectonic implications. Gondwana Research 12, 113–120. oceanic basalt: implication for mantle composition and Processes. In: Yogodzinski, G.M., Volynets, O.N., Koloskov, A.V., 1994. Magnesian andesites Saunders, A.D., Morry, M.J. (Eds.), Magmatism in the Ocean Basin: and the subduction component in a strongly calc-alkaline series at Piip Geological Society. London Special Publication, vol. 42, pp. 528–548. Volcano, far western Aleutians. Journal of Petrology 35, 163–204. Sylvester, P.J., 1998. Post-collisional alkaline granites. The Journal of Geology Yuan, C., Sun, M., Li, J.L., 1999. Ages and possible source of the two granite 97, 261–280. plutons in middle of Western Kunlun. Chinese Science Bulletin 44, 534–537. Tanaka, T., et al., 2000. JNdi-1: a neodymium isotopic reference in consistency Yuan, C., Sun, M., Zhou, M.F., Zhou, H., Xiao, W.J., Li, J.L., 2002. Tectonic with LaJolla neodymiu. Chemical Geology 168, 279–281. evolution of the Western Kunlun: geochronologic and geochemical Tarney, J., Jones, C.E., 1994. Trace element geochemistry of orogenic igneous constraints from Kudi granites. International Geological Review 44, rocks and crustal growth models. Journal of Geological Society, London 653–669. 151, 855–868. Zhang, Y.Q., Zhu, B.Q., Xie, Y.W., 1998. The uplifting rates for the western Tate, M.C., Johnson, S.E., 2000. Subvolcanic and deep-crustal tonalite genesis Qinghai–Xizang Plateau: interpretation of 40Ar–39Ar dating data for the beneath the Mexican Peninsular Ranges. The Journal of Geology 108, granites in the area from Yecheng to Shiquanhe (in Chinese). Acta 721–728. Petrologica Sinica 14, 11–22 (in Chinese with English abstract). Wang, S.S., Hu, S.L., Sang, H.Q., Qiu, Y., 1992. Develop of the hornblende Zhang, C.L., Dong, Y.G., Zhao, Y., 2003a. Geochemistry of Mesoproterozoic standard BSP21 for Ar–Ar age determination. Acta Petrologica Sinica 8, volcanics in West Kunlun: evidence for the plate tectonic evolution. Acta 103–127 (in Chinese with English abstract). Geologica Sinica 78, 532–542. Wang, Z.Q., Jiang, C.F., Yan, Q.R., Yan, Z., 2001. Accretion and collision Zhang, C.L., Zhao, Y., Guo, K.Y., Dong, Y.G., 2003b. Grenville orogeny in orogeneses in the West Kunlun Mountains, China. Gondwana Research 4, north of the Qinghai–Tibet Plateau: first evidence from isotopic dating. 843–844. Chinese Journal Geology 38, 535–538 (in Chinese with English abstract). Wang, Q., Xu, J.F., Jian, P., Bao, Z.W., Zhao, Z.H., Li, C.F., Xiong, X.L., Ma, J.L., Zhang, C.L., Shen, J.L., Guo, K.Y., 2004a. Geochemistry of the Neoproterozoic 2006. Petrogenesis of adaktic porphyries in an extensional tectonic setting, mafic dyke swarm and basalt in south of Tarim Plate and its tectonic Dexing, south China: implications for the genesis of porphyry copper significance. Acta Petrologica Sinica 20, 473–482 (in Chinese with English mineralization. Journal of Petrology 47, 119–144. abstract). Weaver, B.L., 1991. The origin of ocean island basalt and end-member Zhang, C.L., Yu, H.F., Shen, J.L., Dong, Y.G., Ye, H.M., Guo, K.Y., 2004b. composition: trace and isotopic constraints. Earth and Planetary Science Zircon SHRIMP age determination of the giant-crystal gabbro and basalt in Letters 104, 381–397. Küda, West Kunlun: dismembering of the Küda Ophiolite. Geological Williams, I.S., 1988. U–Th–Pb geochronology by ion microprobe. Applications Review 50, 639–643 (in Chinese with English abstract). of microanalytical techniques to understanding mineralizing processes. Zhang, C.L., Li, Z.X., Li, X.H., Wang, A.G., Guo, K.Y., 2006. Neoproterozoic Review of Economic Geology 7, 1–35. bimodal intrusive complex in southwestern Tarim block of NW China: age, Wu, X.Y., Xu, Y.G., Ma, J.L., Xu, J.F., Wang, Q., 2003. Geochemistry and geochemistry and Nd isotope and implications for the rifting of Rodinia. petrogenesis of the Mesozoic high-Mg diorites from western Shangdong. International Geological Review 48, 112–128. Geotectonica et Metallogenia 27, 228–236 (in Chinese with English Zhang, C.L., Lu, S.N., Yu, H.F., Ye, H.M., 2007a. Tectonic evolution of the abstract). West Kunlun Orogen in north of Qinghai–Tibet Plateau: evidences from Xiao, W.J., Hou, Q.L., Li, J.L., 1999. Tectonic facies and the archipelago- zircon SHRIMP and LA-ICP-MS U–Pb ages. Science in China (D-Series) accretion process of the West Kunlun, China. Science in China (D-Series) 50, 825–835. 43, 135–143 (supp.). Zhang, C.L., Li, Z.X., Li, X.H., Yu, H.F., Ye, H.M., 2007b. An early Xiao, W.J., Windley, B.F., Fang, A.M., Yuan, C., Wang, Z.H., Hao, J., Hou, Q.L., Paleoproterozoic high-K intrusive complex in southwestern Tarim Block, 2001. Palaeozoic–Early Mesozoic accretionary tectonics of the Western NW China: age, geochemistry, and tectonic implications. Gondwana Kunlun Range, NW China. Gondwana Research 4, 826–827. Research 12, 101–112. Xiao, W.J., Windley, B.F., Hao, J., 2002. Arc-ophiolite obduction in the western Zhou, H., Chu, Z.Y., Li, J.L., Hou, Q.L., Wang, Z.H., Fang, A.M., 2000. Kunlun range (China): implications for the Palaeozoic evolution of central 40Ar/39Ar dating of ductile shear zone in Kuda, West Kunlun, Xinjiang. Asia. Journal of Geological Society, London 159, 517–528. Chinese Journal Geology 35, 233–239 (in Chinese with English abstract).