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Precambrian Research 257 (2015) 47–64

Contents lists available at ScienceDirect

Precambrian Research

jo ur nal homep ag e: www.elsev ier .com/ locate /precamres

he 600–580 Ma continental rift basalts in North Qilian Shan,orthwest China: Links between the Qilian-Qaidam block and SEustralia, and the reconstruction of East Gondwana

in Xua, Shuguang Songa,b,∗, Li Suc, Zhengxiang Lid, Yaoling Niub, Mark B. Allenb

MOE Key Laboratory of Orogenic Belt and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, ChinaDepartment of Earth Sciences, Durham University, Durham DH1 3LE, UKGeological Lab Center, China University of Geosciences, Beijing 100083, ChinaARC Center of Excellence for Core to Crust Fluid Systems (CCFS) and The Institute for Geoscience Research (TIGeR), Department of Applied Geology, Curtinniversity, Perth 6845, Australia

r t i c l e i n f o

rticle history:eceived 5 September 2014eceived in revised form2 November 2014ccepted 25 November 2014vailable online 4 December 2014

a b s t r a c t

We report a sequence of thick, well-preserved basaltic lavas interlayered with shallow marine dolomiticcarbonates, mudstones and siltstones of the Zhulongguan Group, in the western segment of the North Qil-ian orogen, northwest China. Two new zircon SIMS ages show that this sequence formed at ∼600–580 Ma.The mafic volcanics can be subdivided into tholeiitic and alkaline basalts, and have compositions sim-ilar to present-day ocean island basalt (OIB) or continental flood basalts. The occurrence, geochemicalfeatures and age data suggest that the Zhulongguan basalts originated at a continental rift setting in the

eywords:hulongguan basaltsontinental riftingate Neoproterozoic

latest Neoproterozoic, within the north margin of the Qilian-Qaidam block. This volcanic-sedimentaryformation exhibits close affinity to the passive continental margin in southeastern Australia. Our obser-vations favor a link of the Qilian-Qaidam block with SE Australia (also south China) during the breakupof Rodinia, thereby filling a void in existing reconstructions of the region.

ilian-Qaidam blockreakup of East Gondwana

. Introduction

Intraplate magmatism, especially continental flood basaltsnduced by mantle plumes or superplumes, plays an importantole in reconstructing the framework of supercontinents (Whitend McKenzie, 1989; Hill et al., 1992; Saunders et al., 1996; Lit al., 1999, 2008b; Ernst et al., 2008). There is a complete spec-rum of within-plate magmatism from extensive sub-alkaline floodasalt provinces to rift volcanism with more alkaline provincesWilson, 1989). Syn-rift sedimentation often proceeds into con-inental breakup, when rifting ceased (i.e. the drift stage) and aew ocean spreading center was created (e.g. Powell et al., 1994).herefore, comparison of geochemical fingerprints of key magmaticvents, together with lithostratigraphic correlation of contempo-

ary rift successions, may help to establish the configuration ofncient continental masses (Li et al., 2008b; Ernst et al., 2008).

∗ Corresponding author at: MOE Key Laboratory of Orogenic Belt and Crustal Evo-ution, School of Earth and Space Sciences, Peking University, Beijing 100871, China.el.: +86 10 62767729.

E-mail address: sgsong@pku.edu.cn (S. Song).

ttp://dx.doi.org/10.1016/j.precamres.2014.11.017301-9268/© 2014 Elsevier B.V. All rights reserved.

© 2014 Elsevier B.V. All rights reserved.

The transition of the tectonic regime from the assembly of theNeoproterozoic supercontinent Rodinia to its breakup is thought tohave occurred in the period of 0.9–0.86 Ga, which corresponds toa magmatic quiescence in South China (Li et al., 2003, 2010a,b,c).Multiple episodes of anorogenic magmatism during 850–720 Maare widely distributed in South China, Tarim, North America, India,South Korea, Southern Africa, and Australia (Powell et al., 1994;Park et al., 1995; Wingate et al., 1998; Preiss, 2000; Frimmel et al.,2001; Lee et al., 2003; Li et al., 1999, 2003, 2008a,b, 2010a,b,c; Linget al., 2003; Wang and Li, 2003; Xu et al., 2005; Lu et al., 2008; Ernstet al., 2008). They are believed to be associated with the breakup ofRodinia, induced by mantle plumes or a superplume (Li et al., 1999,2003, 2008b; Wang et al., 2007, 2008, 2009, 2010; Ernst et al., 2008).In addition, there are geological records suggesting the separationof microcontinents from the eastern Australia-east Antarctica con-tinental margin during the 600–550 Ma interval (Crawford, 1992;Veevers et al., 1997; Crawford et al., 1997; Wingate et al., 1998;Foden et al., 2001; Direen and Crawford, 2003; Meffre et al., 2004;Fergusson et al., 2009).

In the Qilian-Qaidam block between South China and Tarim,within-plate magmatic rocks of 850–750 Ma have also beenrecognized, including mafic-ultramafic intrusions, mafic dykes,continental flood basalts, and anorogenic granites, and they were

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nterpreted to be correlated with the fragmentation of Rodinia (Lit al., 2005; Tseng et al., 2006; Lu et al., 2008; Song et al., 2010;ung et al., 2013).

The Early Paleozoic North Qilian Orogen (NQO) is located athe northeastern margin of the Tibetan Plateau, NW China, withinhe tectonically active Qilian Shan. It formed by the closure of aeoproterozoic to Early Paleozoic ocean and recorded a completeilson Cycle from the continental breakup to collision of the

ilian and Alxa basement blocks (for details, see Song et al., 2013nd references therein). The Qilian block is itself separated fromhe larger Qaidam block by the Early Paleozoic North Qaidam UHPelt, and they are suggested to be of Yangtze affinity on the basis ofeso- to Neoproterozoic intrusions relevant to the amalgamation

f Rodinia supercontinent (Guo et al., 1999; Wan et al., 2001,006; Song et al., 2012; Tung et al., 2007, 2013). However, theeological evolution of the Qilian-Qaidam block, especially itselation with South China, Tarim and position in Rodinia duringhe late Neoproterozoic, are still not constrained. The sparseutcrop of within-plate magmatism hinders a direct comparisonith other fragments of Rodinia. This may be attributed to the

uperimposed tectonic modification, the subduction of passiveontinental margins or their deep burial during the later stages ofhe orogeny (Yin et al., 2008; Song et al., 2014).

In this paper, we present new field observations, SIMS U–Pbircon ages, elemental and Sr–Nd isotopic data, and mineralompositions for the basalts interbedded with shallow marineedimentary rocks in the northern margin of the Qilian-Qaidamlock. A better understanding of this volcanic sequence willnable a useful comparison with the volcanic passive marginn southeastern Australia and the Late Precambrian formationn South China. Such studies will not only provide insightsnto the development history of the North Qilian Orogen dur-ng the Precambrian, but may also reveal the relationship of theilian-Qaidam block, South China and Australia in the context ofodinia.

. Geological setting

The Qilian-Qaidam block in the northern Tibetan Plateau isresently surrounded by three Precambrian cratons, i.e. the Northhina Craton (NCC) to the east, the Tarim Craton (TC) to the north-est and the South China Craton (SCC) to the southeast (Fig. 1a).

t consists of the North Qilian oceanic suture zone, the Qilianlock, the North Qaidam UHP belt and the Qaidam block, fromorth to south. The North Qilian oceanic suture zone (namelyorth Qilian Orogen) extends NW–SE for ∼1000 km (Fig. 1b). In

he northwest, it is offset by a sinistral strike-slip Altyn Taghault (ATF) for up to 400 km and in direct contact with the Dun-uang block (Zhang et al., 2001). In the northeast, the Alxa (alsonown as Alashan) block is bounded by the Longshoushan FaultLF), and considered to be the westernmost component of NCCue to the similar Archean-Paleoproterozoic gneisses in the twoegions (Zhao and Cawood, 2012; Zhang et al., 2013a,b). How-ver, the ∼827 Ma Jinchuan Cu–Ni-bearing ultramafic rocks and00–900 Ma granitoids implied that the Alxa block may be a frag-ent of Rodinia, with affinities to the Qilian and South China

locks in the Upper Proterozoic (Li et al., 2005; Song et al., 2013).he Qilian block in the south is bounded on its northeast side byhe North Margin Fault (NMF) and has a Precambrian basementhich has the affinity with the Yangtze block, i.e. the northernart of the larger South China block (Wan et al., 2001, 2006; Lu

t al., 2008; Song et al., 2010, 2012, 2013; Tung et al., 2007, 2013).

Paleoproterozoic terrane, namely the Quanji Massif, was rec-gnized in the south part of the Qilian block, which consists ofaleoproterozoic granitic gneisses and mafic granulite with ages

arch 257 (2015) 47–64

of 2470–1800 Ma (Zhang et al., 2001; Chen et al., 2007, 2009a; Luet al., 2008).

Further south is the North Qaidam UHP metamorphic belt, rep-resenting a continent–continental collision zone along the northernmargin of the Qaidam Basin (e.g. Song et al., 2004a, 2014 andreferences therein). The UHP belt is mainly consisted of graniticgneisses, pelitic gneisses, with eclogites and garnet peridotites.It is believed that the continental crust including orthogneisses(1000–900 Ma) had subducted into depth of 200 km and exhumedwith enclosed UHPM rocks in the period of 460–400 Ma (Songet al., 2012). Two episodes of orogeny during the Grenville andCaledonian age, involved progression from oceanic subduction tocontinental collision, have been confirmed by Song et al. (2013,2014). The Qaidam Basin to the south is covered by a Mesozoicto Cenozoic sediments and underlain mainly by Precambrian crys-talline basement (Wan et al., 2006). The basement rocks mainlyexposed in the North Qaidam UHPM belt and south margin of theQaidam block (Song et al., 2014).

Previous works have reached a consensus that the Qilian andQaidam blocks have close affinities with South China according tothe orogenic and rifting events related to the assembly and breakupof Rodinia, respectively (Guo et al., 1999; Lu et al., 2008; Song et al.,2012, 2013; Tung et al., 2007, 2013). Further Wan et al. (2001,2006) emphasized that the high-grade basement of the North Qil-ian orogenic belt has similar Nd isotopic compositions with thoseof the North Qaidam UHPM belt. Thus the Qilian and Qaidam blocksform one integrated terrane, i.e. the Qilian-Qaidam block during thePrecambrian.

The North Qilian Orogen (NQO) is one of the best pre-served oceanic-type cold subduction belts in China, resultingfrom closing of the ancient Qilian Ocean between Alxa and theQilian-Qaidam block during the Early Paleozoic (Xiao et al., 1978;Wu et al., 1993; Feng and He, 1996; Zhang et al., 2007; Songet al., 2004b, 2006, 2007, 2009, 2013; Xiao et al., 2009; Chenet al., 2014). It consists dominantly of Middle-Late Proterozoichigh-grade metamorphic basement, Late Proterozoic low-grademetamorphic volcanic and sedimentary successions, Early Paleo-zoic subduction-related rock associations (ophiolite complexes,high-pressure/low-temperature metamorphic rocks, arc-relatedvolcanics and intrusions), Silurian flysch and Devonian molasse for-mations, and later sedimentary cover (Fig. 1b). The present-dayhigh topography of the NQO results from the India-Asia colli-sion and Tibetan plateau uplift in the late Cenozoic (Yin et al.,2008).

Precambrian fragments in the northern margin of the Qilianblock have been juxtaposed with arc rocks during the Early Paleo-zoic collision-accretion process (Fig. 1b). In the western segment,the stratigraphic succession contains a pre-Sinian group, Sinianvolcanic-sedimentary sequence and Early Paleozoic cover strata(Fig. 2b).

The 900–1000 Ma orthogneisses constitute the oldest and majorcomponent of the Precambrian basement of the Qilian-Qaidamblock (Guo et al., 1999; Wan et al., 2001; Li et al., 2007; Song et al.,2012; Tung et al., 2007, 2013). In addition, within-plate magmatism(850–750 Ma) including diabasic dyke swarms, mafic-ultramaficintrusions, anorogenic granitoids, and the remnants of continen-tal flood basalts, have been recognized (Li et al., 2005; Tseng et al.,2006; Lu et al., 2008; Song et al., 2010; Tung et al., 2013).

The Zhulongguan Group mainly crops out in the northwesternpart of the Qilian block with total area of more than 1000 km2 and athickness of about 3–7 km (Fig. 2a). The volcano-sedimentary suc-cession belt is controlled by regional-scale faults and extends along

the main axis of the NQO. This group consists predominantly ofthe low-grade metamorphic volcanic layers interbedded with shal-low marine dolomitic limestone, terrigenous and pyroclastic rocksand iron-bearing quartzite (Xia et al., 2000), which constitute a

X. Xu et al. / Precambrian Research 257 (2015) 47–64 49

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ig. 1. (a) Tectonic location of the Qilian-Qaidam blocks in NW China (after Song et Altyn Tagh Fault, LF – Longshoushan Fault, NMF – North Margin Fault of the Qilian

ulti-cycle volcanic-sedimentary succession (Fig. 2b). This group isectonically juxtaposed with the Aoyougou ophiolite (495–504 Ma,iang et al., 2007; Song et al., 2013; Fig. 2c) and intruded by a 430 Madakite pluton (Chen et al., 2012).

The overlying sequences, namely the Jingtieshan and Dali-gou groups, are faulted against the Zhulongguan Group andre dominantly constituted of sandstones, siltstones, mudstones,olomites interbedded with mafic volcanic and iron ore layersFig. 2b), which were considered as the middle and upper part ofhe Zhulongguan Group (Xia et al., 2000). The Baiyanggou Groupn the uppermost Sinian succession is recognized as a suite ofhick coarse clastic rocks, including tillitic and sandy conglom-rates. The pebbles from the basal tillite are derived from thenderlying Jingtieshan and Daliugou Group, which indicates rapidccumulation during the rifting stage (Zuo et al., 1999). The Earlyaleozoic complex is dominantly consisted of Cambrian to Ordovi-ian arc-related volcanic and sedimentary rocks and Silurian flyschormation.

The regional importance of these Late Precambrian rocks isometimes downplayed, such that the entire Qilian Shan is referredo as an accretionary orogenic belt without significant Precambrianrust (e.g. S engör, 1990; Xiao et al., 2009). However, the extent,hickness, continuity and stratigraphy of the Precambrian succes-ion, the absence of major metamorphism and presence of ∼1 Gaontinental basement, all point to a microcontinental terrane(s) ofufficient size to be considered in regional and global plate recon-tructions.

. Petrography of the Zhulongguan basalts

Samples were collected from three sections in the Zhu-ongguan Group (see localities in Fig. 2a). Two representative

13); (b) simplified geological map of the Qilian-Qaidam region. Abbreviations: ATFk.

sections, rock assemblages and field relations are shown inFig. 2c.

In the Aoyougou valley (Section 1), four layers of mafic vol-canic lavas are interbedded with Precambrian carbonate layers;they constitute multiple eruption–deposition cycles. The basalticlavas can reach up to 300 m in thickness. They are weakly alteredand have massive (locally pillow), vesicular/amygdaloidal struc-tures (Fig. 3b and d). Some of them are porphyritic with abundantplagioclase and augite phenocrysts in a usually intersertal-textured groundmass filled with plagioclase laths, chloritisedglass and Fe–Ti oxides. Most of these lavas show ophitic texturewith euhedral plagioclase skeletons and subhedral augite grains(Fig. 3g).

Massive basalt samples (11QL-65 and 66) come from the lowerpart of the Zhulongguan Group near Qiqing village (Section 2in Fig. 2). The volcanic interlayers are 100–300 m in thickness,interbedded with volcanic breccias, tuffs, siliceous slates, silt-stone/sandstone, and limestone. In thin sections, they mainlyconsist of clinopyroxene, plagioclase and minor alteration minerals(actinolite–chlorite).

The rest of the samples were collected from the Jiugeqingyangsection (Fig. 2). These basaltic lavas are accompanied by iron orebeds, sandstone, tuff, volcanic breccia, shale and pelite. The volcani-clastic sample (13QL-18) consists of detrital components includingrock fragments (basaltic glass) and mineral clasts (clinopyroxeneand olivine) (Fig. 3h). Some of basaltic samples show ophitic texturesimilar to some of the Aoyougou section while the others con-tain abundant altered clinopyroxene and plagioclase phenocrysts

with the groundmass glass replaced by secondary chlorite, epi-dote and calcite (Fig. 3e and f). The clinopyroxene phenocrystsare commonly subhedral to anhedral with a diopside composition(Wo46–48En38–42Fs12–16).

50 X. Xu et al. / Precambrian Research 257 (2015) 47–64

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. Analytical methods

Zircons were separated from 11QL-65 and 13QL-18 by usingtandard density and magnetic separation techniques. Zirconrains, together with the standard zircon Plésovice and Qinghu,ere embedded in an epoxy mount and then polished down to

xpose the inner structure for analysis. The CL examination wasone by using a FEI QUANTA650 FEG Scanning Electron Microscope

SEM) under conditions of 15 kV/120 nA in the School of Earth andpace Science, Peking University, Beijing.

Measurements of U–Th–Pb isotopes were conducted using aameca IMS-1280 SIMS in the Institute of Geology and Geophysics,

(b) Stratigraphic column of the Qiqing area, showing the Precambrian basement,omplex. (c) Two cross-sections of the Zhulongguan Group with sample localities.

Chinese Academy of Sciences in Beijing. The instrument descriptionand analytical procedure is given in Li et al. (2009). The primary O2

−

ion beam spot is about 20–30 mm in size. Analysis of the standardzircon Plésovice was interspersed with analysis of unknowns. Eachmeasurement consists of 7 cycles. Pb/U calibration was performedrelative to zircon standard Plésovice (337 Ma, Sláma et al., 2008);U and Th concentrations were calibrated against zircon standard91,500 (Wiedenbeck et al., 1995). A long-term uncertainty of 1.5%

(1� RSD) for 206Pb/238U measurements of the standard zircons waspropagated to the unknowns (Li et al., 2010a,b,c), despite that themeasured 206Pb/238U error in a specific session is generally 1% (1�RSD). Measured compositions were corrected for common Pb using

X. Xu et al. / Precambrian Research 257 (2015) 47–64 51

Fig. 3. Field and photomicrographs of the Zhulongguan basalts. (a) Tholeiitic basalt conformably contacting dolomitic limestones. (b) The massive basalt with amygdalae. (c)The thick basaltic lava layers with siltstone. (d) The thick pillow lavas. (e, f) Clinopyroxene phenocrysts in alkaline basalts (12QL-101). (g) The intersertal and ophitic textureshowing pyroxene grains within the plagioclase skeletons in tholeiitic basalt (12QL-106). (h) Basaltic glass and detrital minerals (olivine and clinopyroxene) in volcaniclasticsample (13QL-18).

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on-radiogenic 204Pb. Corrections are sufficiently small to be insen-itive to the choice of common Pb composition, and an averagef present-day crustal composition (Stacey and Kramers, 1975) issed for the common Pb assuming that the common Pb is largelyurface contamination introduced during sample preparation. Dataeduction was carried out using the Isoplot/Ex v. 2.49 programLudwig, 2001). Uncertainties on individual analyses in data tablesre reported at 1� level; Concordia U–Pb ages are quoted with 95%onfidence interval.

In order to monitor the external uncertainties of SIMS U–Pb zir-on dating calibrated against Plésovice standard, an in-house zircontandard Qinghu was alternately analyzed as an unknown togetherith other unknown zircons. The measurements on Qinghu zir-

on yield Concordia ages of 160.2 ± 0.8 Ma and 159.3 ± 1.9 Ma,hich are identical within error with the recommended value of

59.5 ± 0.2 Ma (Li et al., 2013a).Bulk-rock major element oxides (SiO2, TiO2, Al2O3, FeO, MnO,

gO, CaO, Na2O, K2O, and P2O3) were determined using inductivelyoupled plasma-atomic emission spectroscopy (ICP-OES) at Chinaniversity of Geosciences, Beijing. The analytical uncertainties areenerally less than 1% for most elements with the exception of TiO2∼1.5%) and P2O5 (∼2.0%). The loss on ignition was measured bylacing 1 g of powder in the furnace at 1000 ◦C for several hoursefore cooled in a desiccator and reweighted. The trace elementnalysis for Zhulongguan basalt samples were accomplished onn Agilent-7500a inductively coupled plasma mass spectrometerICP-MS) at China University of Geosciences, Beijing. The detailednalytical procedures follow Song et al. (2010). The relative differ-nce between measured and recommended values for two USGSock reference materials (BCR-1 and BHVO-1) indicates that analyt-cal accuracy is better than 5% for most elements, ranging between0% and 13% for Cu, Sc, Nb, Er, Th, and U, and between 10% and 15%or Ta, Tm, and Gd.

The bulk-rock Sr–Nd isotope analyses are accomplished atOE Key Laboratory of Orogenic Belts and Crustal Evolution,

eking University. About 300 mg unknown samples and ∼200 mgtandard samples (BCR-2) were dissolved by using HF + HNO3n Teflon vessels and heated at 140 ◦C for a week in order toe completely dissolved. The pure Sr and Nd were obtainedy passing through conventional cation columns (AG50W and507) for analysis using a multi-collector inductively coupledlasma mass spectrometer (MC-ICP-MS) of the type VG AXIOM.ass fractionation corrections for Sr and Nd isotopic ratios were

ormalized to 86Sr/88Sr = 0.1194 and 146Nd/144Nd = 0.7219, respec-ively. Repeated analyses for the Nd and Sr standard samplesJNdi and NBS987) yielded 143Nd/144Nd = 0.512120 ± 11 (2�) and7Sr/86Sr = 0.710250 ± 11 (2�), respectively.

. Results

.1. U–Pb zircon age

One basalt (11QL-65) and one volcaniclastic sample (13QL-18)ere selected for SIMS zircon U–Pb dating. Sample 11QL-65 comes

rom the lower half of the succession, and sample 13QL-18 fromear the top (Fig. 2). The results are listed in Table 1 and illus-rated on concordia plots in Fig. 4B and D. Zircon grains from1QL-65 show mostly irregular and fragmentation tabular shapesith length up to 100 �m and length-width ratios up to 2. The CL

mages (Fig. 4A) display slight to dark luminescence and homoge-eous structure with straight and wide growth bands, which areimilar to zircons from mafic volcanic and gabbroic rocks (Song

t al., 2010). The CL images of zircons from 13QL-18 are similar tohose from 11QL-65. As shown in Fig. 4C, these grains are mainlyrregular crystals, indicating that they are directly derived from thehulongguan basalts.

arch 257 (2015) 47–64

The zircons of the basalt sample (11QL-65) have variousabundances of Th (43–2158 ppm) and U (90–1340 ppm) withrelatively high Th/U ratios (0.47–1.6). Eleven analyses yield appar-ent 206Pb/238U ages of 571–626 Ma and form a concordia ageof 600 ± 7 Ma (MSWD = 0.14) (Fig. 4B); the other three spotsgive distinctly older 207Pb/206Pb apparent ages of 1471 ± 25 Ma,1994 ± 13 Ma and 2520 ± 9 Ma, respectively. The uniform CL imagesand U–Pb ages suggest that the first group of zircons was crystal-lized from a basaltic magma and could represent the eruption timeof Zhulongguan basaltic lava, whereas the old zircons (1.5–2.5 Ga)may be derived from the Precambrian basement. Similarly, the ura-nium content in zircons from sample 13QL-18 varies in a large rangefrom 92 to 818 ppm and Th from 50 to 1041 ppm with Th/U ratiosof 0.42–1.27. One spot (#10) was excluded for its high commonPb (f206 = 1.16), and other nine analyses yield 206Pb/238U apparentages ranging from 567 to 597 Ma and a weighted average age of583 ± 7 Ma (MSWD = 1.4), the same as the concordia U–Pb age of583 ± 3 Ma (n = 9, MSWD = 0.72). In conclusion, the Zhulongguangbasalts were formed at ∼600–580 Ma.

5.2. Geochemistry

5.2.1. Whole-rock major and trace elementsFifteen basalt samples (see localities in Fig. 2) were analyzed for

major and trace elemental compositions (Table 2). All the analy-ses are plotted on an anhydrous basis (Fig. 5). Of these samples,5 plot in the alkaline field and 10 in the subalkaline basalt fieldon the Nb/Y versus Zr/TiO2 diagram (Fig. 5a). All the subalkalinebasalts belong to the tholeiitic series in the FeOt/MgO versus TiO2plot (Fig. 5b). The tholeiitic samples have low Ti/Y ratios (<500),whereas alkaline samples show high Ti/Y ratios (>500) based onthe classification of Xu et al. (2001). All of the mafic rocks are sodicseries (Na2O > K2O).

The tholeiitic basalts have relatively high SiO2 (48–56%), Fe2O3T(13.5–17.8%), Y (34.8–46.8 ppm) and HREE, but low MgO (3.1–6.0%),Mg# (31–45) and compatible elements. The low contents of MgO, Cr(12–83 ppm) and Ni (20–64 ppm) are far from the expected com-position of melts in equilibrium with the mantle peridotite (Cox,1980; Wilson, 1989), indicating significant fractional crystallizationand/or crustal contamination.

The alkaline basalts show a relative narrow compositionalvariation with lower SiO2 (49–52%), TiO2 (1.5–3.2%) and Fe2O3T(11.7–15.5%). The higher MgO (6.7–11.1%), Mg# (53–69), Cr (up to622 ppm) and Ni (up to 280 ppm) imply less evolved features. Sam-ple 11QL-65 has the highest MgO (11.1%), Mg# (69), Cr (622 ppm)and Ni (280 ppm) which is similar to the picritic or primitive high-Mg (e.g. Mg# > 65 and/or MgO > 9 wt.%) magma.

On primitive-mantle normalized multiple trace elements dia-grams, the alkaline basalts have the uniform “humped” distributionpatterns characterized by variable enrichment in Rb, Ba, Pb, Nb, Ta,Nd and Ti, and depletion in Th, U, Sr, P and Y, which are akin tothose of the high-Ti picritic basalts in Deccan Traps of India (Mellusoet al., 2006; Fig. 6c). On the contrary, the tholeiitic basalts displayuniform negative anomalies of HFSE (Nb* = 0.3–0.9; Niu and Batiza,1997), various depletion of Sr, P, Eu, and positive anomalies of mostincompatible elements including Th, U and Ti with a large variationin Rb and Ba. The composition of the tholeiites is similar to the low-Ti basalts in several large igneous provinces, such as Emeishan inSouth China (Xu et al., 2001; Fig. 6d).

As shown in Fig. 6a and b, all the samples exhibit consistent LREEenrichment ((La/Yb)n = 5.4–7.2, 2.3–4.5 for the alkaline and tholei-itic basalts, respectively). Most alkaline samples shows positive

anomalies of Eu (Eu/Eu* = 1.03–1.70, except for 12QL-109), whereasthe latter has the uniform Eu depletion (Eu/Eu* = 0.77–0.94). Thesefeatures are consistent with the observation that the tholeiiticbasalts are more evolved than the alkaline group. In summary, the

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Table 1SIMS zircon U–Pb data for the Zhulongguan basalt (11QL-65) and volcaniclastic rock (13QL-18).

Spot# U ppm Th ppm Th/U f206 (%) 207Pb206Pb

±1� (%) 207Pb235U

±1? (%) 206Pb238U

±1� (%) 207/206 Age (Ma) ±1� 207/235 Age (Ma) ±1� 206/238 Age (Ma) ±1�

11QL-651 227 116 0.51 0.20 0.0922 1.33 3.26 2.01 0.257 1.51 1471 25 1472 16 1473 202 740 851 1.15 0.03 0.0602 1.64 0.82 2.23 0.099 1.50 611 35 610 10 610 93 158 103 0.66 0.00 0.0653 2.76 0.87 3.14 0.097 1.50 784 57 636 15 595 94 278 200 0.72 0.09 0.0608 2.31 0.78 2.75 0.093 1.50 632 49 583 12 571 85 198 127 0.64 0.00 0.0588 2.73 0.79 3.12 0.097 1.52 559 58 589 14 597 96 817 984 1.20 0.23 0.0590 1.48 0.78 2.13 0.096 1.52 566 32 587 10 592 97 440 215 0.49 0.05 0.1226 0.76 5.99 1.68 0.354 1.51 1994 13 1974 15 1955 258 379 122 0.32 0.04 0.1662 0.55 10.66 1.61 0.465 1.51 2520 9 2494 15 2463 319 1271 1763 1.39 0.08 0.0600 1.06 0.82 1.83 0.099 1.50 605 23 607 8 607 9

10 1340 2158 1.61 0.06 0.0596 1.28 0.84 1.97 0.102 1.50 590 28 619 9 626 911 801 595 0.74 0.17 0.0584 1.63 0.80 2.23 0.099 1.52 546 35 596 10 609 912 97 52 0.54 0.38 0.0602 5.51 0.80 5.71 0.096 1.50 611 115 597 26 594 913 90 43 0.47 0.83 0.0603 8.84 0.82 8.97 0.098 1.53 614 180 606 42 604 914 290 209 0.72 0.17 0.0591 2.34 0.80 2.78 0.098 1.50 570 50 597 13 604 9

13QL-181 380 325 0.85 0.00 0.05868 0.73 0.78453 1.67 0.0970 1.50 555 16 588 8 597 92 381 308 0.81 0.05 0.06004 0.91 0.80147 1.75 0.0968 1.50 605 20 598 8 596 93 92 50 0.55 0.00 0.05988 1.49 0.78667 2.11 0.0953 1.50 599 32 589 10 587 84 413 343 0.83 0.36 0.05964 0.99 0.78620 1.85 0.0956 1.56 591 21 589 8 589 95 188 123 0.66 0.45 0.06056 1.66 0.76781 2.24 0.0919 1.50 624 35 579 10 567 86 159 82 0.52 0.13 0.05872 1.17 0.75873 1.90 0.0937 1.50 557 25 573 8 577 87 217 90 0.42 0.02 0.05850 1.35 0.77238 2.02 0.0958 1.50 549 29 581 9 590 98 297 331 1.11 0.00 0.05924 0.95 0.76865 1.79 0.0941 1.52 576 21 579 8 580 89 818 1041 1.27 0.01 0.05930 0.53 0.76770 1.60 0.0939 1.51 578 12 578 7 579 8

10 224 124 0.55 1.16 0.05616 2.77 0.71487 3.24 0.0923 1.68 459 60 548 14 569 9

f206 is the percentage of common 206Pb in total 206Pb. All error is 1sigma (1�).

54 X. Xu et al. / Precambrian Research 257 (2015) 47–64

e zirco

Ztfl

5

wsob1

tvoftIaS(

ufbiott

Fig. 4. (A and B) Cathodoluminescence images of representativ

hulongguan basalts show immobile trace elements characteris-ics similar to the present-day OIB and/or at least some continentalood basalts, such as the Emeishan and Deccan lavas.

.2.2. Whole-rock Sr–Nd isotopic dataFive alkaline and seven tholeiitic basalts were analyzed for

hole-rock Sr–Nd isotopic composition. The results are pre-ented in Table 3 and illustrated in Fig. 7. The initial valuesf the Sr–Nd isotope were calculated at 600 Ma. The alkalineasalts have low 87Sr/86Sr ratios (0.70736–0.70848) and high43Nd/144Nd ratios (0.512656–0.512733). In spite of the devia-ion from the mantle array due to the high initial Sr isotopicalues, the positive εNd values (4.1–5.3) are similar to thosef modern plume-related basalts and high-Ti basalts in severalamous LIPs (Fig. 7A). It is notable that they are also iden-ical to that of picritic and upper basaltic volcanics on Kingsland, Tasmania (εNd(579 Ma) = +3.5 to +4.8; Meffre et al., 2004)nd the high-Nb basalts of Mt Arrowsmith and Wright in Newouth Wales (εNd(586Ma) = +3.7 to +4.7; Crawford et al., 1997)Fig. 7B).

On the contrary, the tholeiitic basalts have low 143Nd/144Nd val-es ranging from 0.512312 to 0.512695 and high 87Sr/86Sr valuesrom 0.70865 to 0.71977. The extremely high Sr isotopic values maye attributed to the alteration of sea water. In general, the Sr–Nd

sotopic characteristics of the tholeiitic basalts are alike to thosef low-Ti basalts from Emeishan, Deccan and Siberia (Fig. 7A). Allholeiitic samples show similar Sm–Nd isotopic compositions tohose of Eastern Australia volcanics (Meffre et al., 2004) (Fig. 7B).

ns; (C and D) Concordia plot for sample 11QL-65 and 13QL-18.

6. Discussion

6.1. Petrogenesis

Primary melt composition not only reflects the pressure andtemperature conditions during partial melting, but also the com-positions of source from which they derived (Putirka, 2005; Putirkaet al., 2007; Herzberg et al., 2007; Herzberg and Asimow, 2008; Niuand O’Hara, 2008; Lee et al., 2009; Humphreys and Niu, 2009; Niuet al., 2011; Wang et al., 2012). Nevertheless, magmas are the inte-grated products of the dynamic melting regime and complicatedmelt transport process (Wilson, 1989; Niu and O’Hara, 2008). Thuswe need to evaluate the effect of later shallow level processes suchas fluid alteration and AFC (assimilation and fractional crystalliza-tion) process on the elemental abundance and isotopic ratios, priorto an analysis of the potential mantle source. The elemental mobil-ity can been estimated by the correlation between Zr (immobile inthe fluids alteration) and other elements (Wang et al., 2008). For theZhulongguan basalts, the high field strength elements (Nb, Ta, Ti,Zr, Hf), REE, V, Th, U and Sr are essentially immobile during meta-morphism and alteration. On the other hand, CaO, Na2O, K2O, Ba,Rb and Pb show no linear relation with zirconium. Therefore thesemobile elements must be excluded to discuss rock classificationand petrogenesis.

6.1.1. Fractional crystallizationThe Zhulongguan basalts show a large variation in MgO, Mg# and

compatible trace elements, suggesting that they have undergone

X. Xu et al. / Precambrian Research 257 (2015) 47–64 55

Table 2Whole-rock major and trace element data for the Zhulongguan basalts.

Sample Alkaline basalts Tholeiitic basalts

11QL-65 11QL-66 12QL-101 12QL-107 12QL-109 09AY-01 09AY-07 09AY-09 09AY-10 09AY-11

Major elements (wt.%)SiO2 50.01 49.29 46.82 47.47 46.59 46.90 51.22 54.08 52.05 54.14TiO2 1.49 1.92 2.26 1.92 2.96 2.80 2.76 3.09 2.68 2.88Al2O3 10.86 13.90 14.45 13.45 12.98 12.50 11.83 13.15 12.18 11.76Fe2O3T 11.35 12.84 13.29 12.00 14.30 14.60 16.09 12.98 17.12 15.75MnO 0.17 0.20 0.17 0.30 0.20 0.17 0.15 0.27 0.16 0.16MgO 10.70 6.99 6.41 7.36 7.46 2.80 5.70 4.54 4.54 3.73CaO 9.20 7.12 7.41 4.23 3.67 8.10 5.32 4.39 6.28 6.83Na2O 1.94 2.30 3.10 2.70 3.65 1.58 2.85 1.99 1.58 2.04K2O 0.45 2.27 1.17 1.70 0.13 1.14 0.82 1.68 0.87 0.71P2O5 0.18 0.28 0.33 0.26 0.33 0.22 0.21 0.25 0.20 0.23LOI 3.14 2.28 4.73 8.62 7.69 9.10 2.95 3.46 2.23 1.68Mg# 68.7 55.9 52.9 58.8 54.9 30.9 45.2 44.9 38.2 35.5Total 99.48 99.39 100.13 100.00 99.98 99.91 99.89 99.88 99.90 99.89

Trace elements (ppm)Sc 31.3 28.7 33.3 33.6 31.7 41.7 40.3 48.2 40.0 40.7V 250 235 413 300 463 477 496 563 479 467Cr 623 140 65 171 31 61 12 14 13 12Co 48 37 49 44 52 43 40 72 37 41Ni 280 69 71 75 44 54 21 26 20 19Rb 14.32 19.39 19.20 20.70 2.89 41.74 14.33 45.52 28.10 10.57Sr 221 314 252 290 276 187 149 152 163 162Y 17.2 21.8 21.4 24.3 29.7 37.2 40.1 42.2 34.9 42.7Zr 107 131 119 117 158 155 164 203 154 183Nb 31.7 32.9 33.3 28.8 42.9 13.4 12.7 14.3 11.9 13.8Ba 279 9474 1864 1654 228 107 157 289 156 223La 11.8 15.7 18.7 17.3 20.3 14.7 20.8 20.7 17.7 22.3Ce 24.9 32.7 41.9 37.7 46.0 33.8 45.1 47.6 40.2 48.8Pr 3.25 4.19 5.45 4.65 6.00 4.46 5.66 6.12 5.07 6.17Nd 14.2 18.1 23.4 19.2 26.0 19.0 23.2 24.8 20.8 25.2Sm 3.41 4.27 5.43 4.54 6.22 4.84 5.64 5.93 5.06 5.94Eu 1.18 2.59 2.26 1.77 2.04 1.33 1.58 1.95 1.45 1.68Gd 3.58 5.07 5.51 5.03 6.58 5.71 6.34 6.80 5.76 6.88Tb 0.549 0.717 0.794 0.770 0.994 0.930 1.025 1.065 0.911 1.099Dy 3.33 4.28 4.62 4.76 5.97 6.17 6.54 6.63 5.77 6.90Ho 0.644 0.827 0.883 0.964 1.182 1.340 1.335 1.347 1.183 1.437Er 1.80 2.24 2.32 2.64 3.18 3.91 4.01 3.84 3.45 4.21Tm 0.243 0.302 0.302 0.355 0.427 0.570 0.574 0.520 0.501 0.594Yb 1.55 1.92 1.87 2.26 2.68 3.78 3.78 3.27 3.33 3.96Lu 0.226 0.273 0.267 0.325 0.383 0.550 0.565 0.471 0.481 0.580Hf 2.70 3.10 3.04 2.86 4.07 3.62 3.80 4.21 3.61 4.28Ta 1.21 1.50 2.19 1.59 2.74 0.76 0.72 0.78 0.68 0.81Pb 1.31 1.14 1.66 4.11 1.69 5.87 6.63 7.53 4.98 7.35Th 1.26 1.45 1.73 2.08 2.11 3.21 4.93 5.63 4.61 5.56U 0.279 0.368 0.428 0.499 0.507 0.850 1.709 1.494 1.164 1.414Ti/Y 651 622 663 506 669 408 384 413 409 368

Sample Tholeiitic basalts

09AY-11 09AY-12 09AY-13 12QL-104 12QL-105 12QL-106

Major elements (wt.%)SiO2 54.14 51.59 51.50 50.58 45.99 51.82TiO2 2.88 2.14 2.65 2.63 3.05 2.70Al2O3 11.76 12.73 12.02 11.72 11.26 11.53Fe2O3T 15.75 14.03 16.05 14.99 16.92 16.13MnO 0.16 0.26 0.23 0.17 0.26 0.17MgO 3.73 4.99 4.65 4.85 5.63 4.75CaO 6.83 7.84 8.99 5.67 8.24 7.98Na2O 2.04 2.37 1.40 2.49 2.91 1.89K2O 0.71 1.71 0.93 0.53 0.28 0.58P2O5 0.23 0.18 0.23 0.29 0.32 0.29LOI 1.68 2.04 1.24 6.07 5.28 2.26Mg# 35.5 45.3 40.3 43.0 43.7 40.7Total 99.89 99.88 99.90 100.00 100.16 100.09

Trace elements (ppm)Sc 40.7 41.8 40.2 47.6 46.1 45.6V 467 383 459 525 528 492Cr 12 59 52 72 80 83Co 41 43 44 47 50 49Ni 19 50 42 60 60 64Rb 10.57 42.44 18.06 33.58 12.03 18.75Sr 162 212 196 166 121 134Y 42.7 34.8 41.2 42.4 46.8 40.1

56 X. Xu et al. / Precambrian Research 257 (2015) 47–64

Table 2Whole-rock major and trace element data for the Zhulongguan basalts.

Sample Tholeiitic basalts

09AY-11 09AY-12 09AY-13 12QL-104 12QL-105 12QL-106

Zr 183 146 166 207 212 194Nb 13.8 11.2 14.2 19.9 21.3 19.1Ba 223 311 174 73 118 104La 22.3 14.2 16.1 14.1 16.0 13.8Ce 48.8 32.5 37.1 37.6 40.0 35.7Pr 6.17 4.23 4.81 5.40 5.65 5.06Nd 25.2 17.8 20.8 24.8 26.0 23.3Sm 5.94 4.46 5.28 6.93 7.27 6.54Eu 1.68 1.28 1.58 2.15 2.20 1.96Gd 6.88 5.24 6.27 8.05 8.55 7.58Tb 1.099 0.847 1.028 1.299 1.393 1.232Dy 6.90 5.38 6.69 8.32 8.87 7.91Ho 1.437 1.105 1.393 1.718 1.859 1.637Er 4.21 3.23 4.08 4.85 5.24 4.64Tm 0.594 0.469 0.582 0.677 0.729 0.650Yb 3.96 3.16 3.91 4.45 4.73 4.26Lu 0.580 0.461 0.574 0.645 0.688 0.622Hf 4.28 3.14 3.74 5.38 5.53 5.10Ta 0.81 0.62 0.79 1.36 1.53 1.27Pb 7.35 4.00 4.32 3.50 3.17 3.06Th 5.56 3.39 3.43 2.81 2.77 2.50U 1.414 0.879 0.907 0.727 0.685 0.662Ti/Y 368 360 368 409 399 423

FeOt/MgO

TiO

2

Tholeiit

ic se

ries

Calc-Alakline series

0

1

10 2 3 4 5

2

3

4

0.01

0.01

0.1

0.1

1

1

10

10

0.001

Nb/Y

Zr/

TiO

*0

.00

01

2

SubAlkalineBasalt

Andesite/Basalt

Andesite

Rhyodacite/Dacite

Alkaline Basalt

Bsn/Nph

TrachyAnd

Trachyte

Rhyolite

Com/Pant Phonolite

Tholeiitic basalts

Alkaline basaltsa b

Fig. 5. (a) Nb/Y versus Zr/TiO2 × 0.0001 diagram (Winchester and Floyd, 1976). (b) FeOt/MgO versus TiO2 diagram (Miyashiro, 1974).

Table 3Whole-rock Sr–Nd isotopic data for the Zhulongguan basalts.

Rb (ppm) Sr (ppm) 87Rb/86Sr 87Sr/86Sr 2� ISr Sm (ppm) Nd (ppm) 147Sm/144Nd 143Nd/144Nd 2� εNd (T)

Alkaline basalts11QL-65 14.32 221.0 0.1831 0.707389 0.000010 0.70582 3.41 14.18 0.1527 0.512696 0.000015 4.511QL-66 19.39 313.8 0.1745 0.707357 0.000009 0.70586 4.27 18.12 0.1494 0.512690 0.000009 4.612QL-101 19.20 251.8 0.2154 0.708482 0.000016 0.70664 5.43 23.36 0.1476 0.512656 0.000019 4.112QL-107 20.70 290.2 0.2015 0.708023 0.000012 0.70630 4.54 19.25 0.1495 0.512663 0.000019 4.112QL-109 2.89 275.6 0.0296 0.707594 0.000019 0.70734 6.22 25.96 0.1520 0.512733 0.000018 5.3

Tholeiitic basalts09AY-01 41.74 187.0 0.6305 0.712885 0.000019 0.70749 4.84 18.98 0.1618 0.512491 0.000019 -0.209AY-09 45.52 151.7 0.8478 0.719766 0.000017 0.71251 5.93 24.82 0.1517 0.512322 0.000018 -2.709AY-10 28.10 163.2 0.4864 0.715721 0.000224 0.71156 5.06 20.83 0.1540 0.512312 0.000019 -3.109AY-12 42.44 211.6 0.5665 0.714250 0.000011 0.70940 4.46 17.78 0.1593 0.512448 0.000018 -0.812QL-104 33.58 166.5 0.5697 0.712088 0.000019 0.70721 6.93 24.76 0.1776 0.512680 0.000017 2.312QL-105 12.03 121.4 0.2798 0.710405 0.000013 0.70801 7.27 26.04 0.1771 0.512695 0.000015 2.612QL-106 18.75 134.4 0.3941 0.708646 0.000018 0.70527 6.54 23.34 0.1778 0.512686 0.000015 2.4

Note: (1) ISr = 87Sr/86Sr − 87Rb/86Sr × (e�T − 1), where �Rb = 1.42 × 10−11 year−1 (Steiger and Jäger, 1977).(2) εNd (T) = {[143Nd/144Nd − 147Sm/144Nd × (e�T − 1)]/[(143Nd/144Nd)CHUR(0) − (147Sm/144Nd)CHUR(0) × (e�T − 1)] − 1} × 10,000, where �Sm = 6.54 × 10−12 year−1;(143Nd/144Nd)CHUR(0) = 0.512638; (147Sm/144Nd)CHUR(0) = 0.1967 (Lugmair and Marti, 1978).(3) T = 600 Ma, crystallization age of the Zhulongguan Group basalts.

X. Xu et al. / Precambrian Research 257 (2015) 47–64 57

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Ro

ck

/Ch

on

dri

teR

ock

/Ch

on

dri

tec

Alkaline basalts

Deccan high-Ti priciteOIB

Rb Ba Th U Nb Ta La Ce Pb Pr Sr P Nd Zr Hf SmEu Ti Gd Tb Dy Y Ho Er TmYb Lu1

10

100

1000

1

10

100

1000

Ro

ck

Pri

mit

i ve

man

t le

a

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Tholeiitic basalts

Upper continental crust

OIB

Emeishan low-Ti basalts

1

10

100

1000

b

Alkaline b asalts

Deccan h igh-Ti pricite

OIB

d

1

10

100

1000

Rb Th Nb La Pb Sr Nd Hf Eu Gd Dy Ho TmBa U Ta Ce Pr P Zr Sm Ti Tb Y Er Yb Lu

Ro

ck

Pri

mit

i ve

man

tle

Upper c ontinental c rust

OIB

Emeishan low-Ti b asalts

Fig. 6. (a, b) Chondrite-normalized REE diagrams. (c, d) Primitive mantle-normalized spidergrams for the Zhulongguan basalts. The normalization values and the ocean-islandb ntal cM

sc(mc

F(Er

asalt (OIB) are from Sun and McDonough (1989). The values of the upper contineelluso et al. (2006), and the Emeishan low-Ti basalts are from Xu et al. (2001).

ignificant fractional crystallization or crustal contamination, espe-

ially the tholeiitic basalts. The correlations between Ni, V and CrFig. 8) suggest that the magma primary to the Zhulongguan basalts

ight experience varying degree of clinopyroxene- and olivine-ontrolled fractionation. For the alkaline basalts, the weak Eu and

ig. 7. (A) Sr–Nd isotopic compositions for the Zhulongguan basalts. Plotted for comparWhite and Duncan, 1996), and EMI and EMII member (Hart, 1988). The CFBs for comparisomeishan (t = 250 Ma; Xu et al., 2001), and Deccan (t = 66 Ma; Melluso et al., 2006). (B) Nocks on King Island of Tasmania and isochron results are from Meffre et al. (2004); Mt W

rust are from Rudnick and Gao (2003). Data for the Deccan high-Ti picrite is from

Sr anomalies imply minor fractionation crystallization of plagio-

clase. For tholeiitic basalts, the fractionation of plagioclase explainsthe negative Eu (Eu/Eu* = 0.77–0.94) and Sr (Sr/Sr* = 0.29–0.70;see Niu and O’Hara, 2009) anomalies. Collectively, the Zhulong-guan tholeiitic basalts mainly underwent crystal fractionation of

ison are: the modern depleted upper mantle (N-MORB) (Zimmer et al., 1995), OIBn include low-Ti and high-Ti basalts from Siberian (t = 248 Ma; Sharma et al., 1992),d–Sm isochron diagram for the Zhulongguan basalts. The data for mafic volcanicright volcanics in western New South Wales from Crawford et al. (1997).

58 X. Xu et al. / Precambrian Research 257 (2015) 47–64

Ni

1 10 100 1000

1

10

100

1000

cpxol

1 10 100 1000

V

1

10

100

1000

cpx

ol

hb

Tholeiitic basalts

Alkaline basalts

A B

F ne fra

oet

6

mht1TW

tcsaFa(vsitc

iN(cclcnrponl

bpbcHs

Cr

ig. 8. (A) Ni and (B) V versus Cr diagrams mainly showing olivine and clinopyroxe

livine + clinopyroxene + plagioclase, whereas the alkaline basaltsxperienced dominantly clinopyroxene and olivine fractionationo a limited extent.

.1.2. Crustal contaminationIn general, intraplate continental basalts display greater ele-

ental and isotopic diversity than oceanic counterparts, whichave been attributed to varying degrees of interaction betweenhe continental lithospheric and asthenospheric sources (Wilson,989; Arndt and Christensen, 1992; Hawkesworth et al., 1995;urner and Hawkesworth, 1995; Xu et al., 2001; Li et al., 2013b;ang et al., 2008, 2014).Nb–Ta and neighboring elements (Th, U and La) are not frac-

ionated from each other during partial melting or fractionalrystallization (Hofmann, 1988), but the enrichment of mantleource and the crustal contamination can significantly increase LILEnd LREE contents and decrease HFSE/LILE or HFSE/LREE ratios.or alkaline basalts, the higher Nb/Th (14–25), Nb/U (57–113)nd Nb/La (1.6–2.7) ratios than those of the primitive mantleNb/Th = 8.4; Nb/U = 34; Nb/La = 1.04; Sun and McDonough, 1989)alues reflect the primary signature of the mantle sources withoutignificant crustal contamination (Fig. 9b and d). The recognitions also supported by a positive anomaly in Ti (Fig. 6c). Likewise,heir high and positive εNd(T) values (Fig. 7a–c) imply insignificantrustal contamination for alkaline lavas.

However, some tholeiitic basalts exhibits crust-like character-stics with obvious enrichment in Th, U, LREE and depletion inb, Ta (La/Nb > 1), although a few show no visible HFSE depletion

La/Nb < 1) ascribing to less/no contamination (Fig. 9b and d). Theontents of Th and U are suggested to be enriched in the upperontinental crust but depleted in the lower continental crust andithospheric mantle (Rudnick and Gao, 2003). Therefore the high Thontent (>2.5 ppm) and Th–U positive anomaly indicate contami-ation with upper crustal materials (Figs. 6d and 9d). Given theelatively wide range of εNd(T) (−3.1 to −0.2), we consider that therimary magma must have experienced significant contaminationf upper crustal rocks with low Nd isotopic values although we can-ot preclude the assimilation of the metasomatized subcontinental

ithospheric mantle.Indeed, Fig. 9 shows a general trend toward more crustal contri-

ution from alkaline to tholeiitic basalts. Trace-element ratio–ratiolots (Fig. 10) for these basalts show good hyperbolic correlations

etween Lu/Hf and Hf/Yb, Lu/Hf and Zr/Yb, also indicating crustalontamination in the form of a binary mixing (Wang et al., 2008).owever these appearances could not been interpreted as the

imple comagmatic evolution with the AFC process on account

Cr

ctionation for alkaline and tholeiitic basalts. The vectors are from Li et al. (2010a).

of the enrichment of LREE (Fig. 9c). Hence, it seems impossiblethat the tholeiitic rocks are derived directly from the alkali lavas.This conclusion is consistent with the different Nd isotopic valuesin the alkaline (+4 to +5) and some of tholeiitic rocks (+2 to +3)without obvious assimilations. In summary, the magma primitiveto the tholeiite basalts is more depleted in trace elements andderived from a more depleted source than the magma primitive tothe alkaline basalts.

6.1.3. Tectonic settingMantle source compositions and melting conditions determine

the compositions of the basaltic magmas (Cox, 1980; Xu et al.,2001; Niu and O’Hara, 2008; Li et al., 2013b; and reference herein).The enrichment in HFSE and LREE of the alkaline basalts maybe directly derived from the asthenospheric mantle such as theOIB-like source or small degree partial melting of a normal-typeMORB source; but the lower εNd(T) (+4 to +5) values than that ofthe contemporaneous depleted upper mantle (εNd(600 Ma) = +8.7)precludes the latter. Of the alkaline basalts, 11QL-65 is the least-evolved with the highest MgO (11.1 wt.%), Mg-number (68.7) andcompatible element content (Cr = 623 ppm; Ni = 280 ppm). We cal-culated the major element composition of the primary magmafor this sample according to the procedure of Lee et al. (2009).Because of the MgO content (>9%), the low pressure fractiona-tion is corrected by incrementally adding olivine. The final primarymagma contains ∼50.9% SiO2, ∼16.4% MgO, and ∼10.8% FeOt, whichis a picritic composition and corresponds to a melt temperatureof ∼1448 ◦C (under anhydrous melting condition). The poten-tial temperature (Tp = 1493 ◦C) of the mantle source is obtainedin terms of the equation of Tp (◦C) = 1463 + 12.74MgO–2924/MgO(Herzberg and O’Hara, 2002). The Tp is obviously higher than thatof the modern mid-ocean ridge basalts (1280–1400 ◦C) and closeto that of the Hawiian picrites (1500–1600 ◦C) (Putirka, 2005;Putirka et al., 2007; Herzberg et al., 2007; Herzberg and Asimow,2008; Lee et al., 2009 and reference herein), indicating an anoma-lously hot mantle source. Extremely high La/Sm (2.1–2.5) andSm/Yb (2.2–3.2) ratios may suggest that they originated from thegarnet-bearing mantle reservoir and experienced the low degreeof partial melting (e.g. Niu et al., 2011). As a result, the primarymagma of the alkaline suite is possibly generated from the par-tial melting of the asthenospheric mantle caused by a mantleplume.

For tholeiite basalts, the relatively low degree of fractionationbetween HREE and LREE may imply a higher degree of meltingand shallower source than the lavas of the alkaline suite (Niuet al., 2011). Overall, the ratios of Zr/Y (4–6.2) and Zr/Sm (21–34)

X. Xu et al. / Precambrian Research 257 (2015) 47–64 59

AFC

FC

FC

0 2 4 6 8 10 12-10

-5

0

5

10

εN

d (

T)

MgO

0 0.5 1.0 1.5 2.0 2.5 3.0-5

-3

-1

1

3

5

7

εN

d (

T)

Nb/La

Crust

al conta

min

ation

Primary mantle

0 1 2 3 4 5-5

-3

-1

1

7

3

5

La/Sm

εN

d (

T)

Crustal contam

ination

Primary m antle

Upper c rust

Crusta

l conta

min

ation

0 0.5 1.0 1.5 2.0 2.5 3.0

Nb/La

0

5

10

15

20

25

30

Nb

/Th

Tholeiitic b asalts

Alkaline basalts a b

c d

F �Nd (T1 paris

aa(dl

Fc

ig. 9. Plots of (a) MgO versus �Nd (T); (b) Nb/La versus �Nd (T); (c) La/Sm versus

989) and upper continental crust (Rudnick and Gao, 2003) are also plotted for com

re similar to many intra-plate basalts (Zr/Y > 3.5, Zr/Sm ≈ 30), but

re distinct from those of island arc rocks (Zr/Y < 3.5, Zr/Sm < 20)Fig. 11a; Wilson, 1989). All tholeiitic and alkaline basalts areropped into continental flood basalts or ocean-island and alka-

ine basalts field in the Ti–V diagram (Fig. 11b). In addition, the

R² = 0 .9878

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.05 0.10 0.15 0.20

Lu/Hf

Hf/

Yb

Tholeiitic basalts

Alkaline b asalts

A

ig. 10. Trace-element ratio-ratios plots of Hf/Yb and Zr/Y against Lu/Hf for the Zhulonontamination with crust materials (Niu and Batiza, 1997).

); (d) Nb/La versus Nb/Th. The ratios of the primary mantle (Sun and McDonough,on.

clinopyroxene phenocrysts of the Zhulongguan basalts show a clear

rifted-related trend (Fig. 11c).

The coexistence of high-Ti and low-Ti groups is recognizedwidely in continental flood basalt provinces, such as the Parana andthe Karoo (Gibson et al., 1995), Deccan Traps (Melluso et al., 2006),

R² = 0 .9397

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

0.05 0.10 0.15 0.20

Lu/Hf

Zr/

Y

B

gguan basalts. The linear or hyperbolic curves are reflective of binary mixing or

60 X. Xu et al. / Precambrian Research 257 (2015) 47–64

Fig. 11. Discrimination plots for the Zhulongguan basalts. (a) Zr versus Zr/Y diagram after Pearce and Norry (1979); (b) Ti versus V plot after Shervais (1982). The fields of arctholeiitic, MORB, continental flood basalts, ocean-island and alkali basalts were drawn by Rollinson (1993) according to Shervais (1982); (c) Alz (percentage of tetrahedrals uan b

SENtab

6

smaeesCa

rCmsts2dr5SNtOe

6Q

ihp(PCeP

ites occupied by Al) versus TiO2 in clinopyroxenes (Loucks, 1990) for the Zhulongg

iberian Traps (Hawkesworth et al., 1995; Sharma et al., 1992),meishan (Xu et al., 2001), South China (Wang et al., 2008), andorth Qaidam (Song et al., 2010). In conclusion, the Zhulongguan

holeiitic (low-Ti) and alkaline (high-Ti) basalts are likely formed inn extension-related within-plate environment probably inducedy a mantle plume, rather than the supra-subduction zone.

.2. Continental rifting and Qilian-Ocean formation

The formation history of the Qilian Ocean has not been well con-trained so far, due to the lack of the bimodal volcanics or intraplateagmatism that could indicate the break-up phase. Based on the

norogenic granitic intrusions with ages of 750–800 Ma (Tsengt al., 2006; Tung et al., 2013) and relic cores in zircons from someclogites (Zhang et al., 2007), Song et al. (2013) inferred that theeafloor spreading of the Paleo-Qilian Ocean, as separating Southhina, Qilian-Qaidam and Tarim blocks from Rodinia, might startedt least from ∼710 Ma and closed at ∼445 Ma.

This study is the first report on the presence of ∼600–580 Maift volcanism in the north margin of the Qilian-Qaidam block, NWhina. The association of alkaline-tholeiitic lavas with shallow-arine facies sedimentary layers in the Zhulongguan Group is

trongly akin to an extensive mafic volcanic passive margin prioro the continental break-up, e.g. the seaward-dipping reflectorequences (SDRS) in southeastern Australia (Direen and Crawford,003; Meffre et al., 2004). The similar isochron results in Fig. 7Bemonstrate that the Zhulongguan basalts resemble the volcanicocks in Australia at the end of the Precambrian. The oldest50 Ma ophiolite in the North Qilian Orogen (Shi et al., 2004;ong et al., 2013) and the Marlborough terrane of the northernew England Fold Belt (Bruce et al., 2000) may also support that

he opening of the Paleo-Qilian Ocean (a branch of Proto-Pacificcean) may occurred immediately after the ca. 600–580 Ma riftingvent.

.3. Implications for the palaeogeographic position of theilian-Qaidam block in Rodinia

In the last decades, much attention had been paid to the geolog-cal evolution of the Rodinia supercontinent. However, its breakupistory remains controversial because of the continuity and com-lexity of widespread rifting associated with episodic plume pulsesHoffman, 1991; Powell et al., 1993, 1994; Veevers et al., 1997;

reiss, 2000; Wang and Li, 2003; Li et al., 1999, 2003, 2008b;awood, 2005; Ernst et al., 2008). It had been proposed that thearly rift events (820–750 Ma) that widely occurred in the rim ofroto-Pacific Ocean were followed by the initial breakup of Rodinia

asalts.

(Powell et al., 1994; Park et al., 1995; Wingate et al., 1998; Li et al.,1995, 1999, 2003, 2008b; Meffre et al., 2004; Cawood, 2005). Sim-ilarly, anorogenic magmatism during this time interval has beenalso reported in the Qilian and Qaidam region (Li et al., 2005; Tsenget al., 2006; Lu et al., 2008; Chen et al., 2009b; Song et al., 2010;Tung et al., 2013). Combined with the comparable Grenville-ageorogeny, the recognition demonstrates the strong affinity betweenthe Qilian-Qaidam (including Quanji Massif) and South China, evenTarim blocks (Wan et al., 2001, 2006; Lu et al., 2008; Chen et al.,2009b; Tung et al., 2007, 2013; Song et al., 2010, 2012, 2014).

The relatively late stage of intraplate magmatic events(∼600 Ma) have been documented in Australia, Tarim, and SouthChina (Table 4). This may represent a long duration fragmenta-tion of Rodinia and the waning stage of plume volcanism (Xu et al.,2013). In north margin of Tarim (present orientation), ca. 615 Malayered basalts are thought to have been generated in an intra-continental rift environment (Xu et al., 2009, 2013). During lateNeoproterozoic to Early Paleozoic, South China received depositionof thick, platform-type carbonates, phosphorite and black shales byrapid subsidence (Wang and Li, 2003), but without lava flows (Shuet al., 2011). Only two volcanic ash beds with ages of 621 ± 7 Ma and555 ± 6 Ma were recognized in the terminal Proterozoic Doushan-tuo Formation (Zhang et al., 2005), which means that the SouthChina was far away from the volcanic eruption centers.

In western New South Wales of Australia, the transitional alka-line basalt-rhyolite suite with zircon SHRIMP age of 586 ± 7 Maoccurs together with marine sedimentary rocks, which has beendemonstrated to represent a continental rift setting (Crawford et al.,1997). On King Island, a thick (>900 m) sequence of late Neoprotero-zoic volcanic and intrusive rocks plus shallow marine carbonatesand siltstones was formed; the upper tholeiitic basalts and picritegave a Sm–Nd isochron age of 579 ± 16 Ma (Meffre et al., 2004)(Fig. 7b). In western Tasmania, a typical rift succession of tholei-itic basalts plus shallow water carbonates, including the RockyCape dyke swarm (590 ± 8 Ma), suggests a latest Precambrian pas-sive continental margin (Crawford, 1992). Direen and Crawford(2003) concluded that the late Neoproterozoic (600–580 Ma) pas-sive margin volcanic rocks occurred along three elongate belts inthe Delamerian Orogen of southeastern Australia, the WonomintaBlock of western New South Wales, the Gleneleg Zone of west-ern Victoria and the King Island-western Tasmania, respectively. Inaddition, the phase of intra-basin fluid flow with a high 87Sr/86Srvalue of 0.7180 in the Adelaide Geosyncline was terminated at

∼586 Ma, which may indicate the onset of a new phase of exten-sion in Australian eastern margin (Foden et al., 2001). Furthermore,mafic schists associated with psammitic rocks at ca. 600 Ma fromthe Anakie Inlier in northeastern Australia were also suggested to

X. Xu et al. / Precambrian Research 257 (2015) 47–64 61

Table 4Compilation of intraplate magmatic records during the late Neoproterozoic in east margin of proto-Gondwana.

Location Rock association Age and method Tectonic setting Reference

Southeast AustraliaMt Wright and Arrowsmith Alkaline basalt-rhyolite

and interbeded marinesedimentary

586 ± 7 Ma (SHRIMP) Continental rift Crawford et al. (1997)

Western Tasmania Picrite, alkaline to tholeiiticbasalts, dolerite dykes,dolomitic limestone

588 ± 8 Ma and 600 ± 8 Ma(K-Ar dates)

An attenuated, riftedpassive continentalmargin

Crawford and Berry (1992)

Tasmania (King Island) Picrite lavas, tholeiite,siliciclastics andcarbonates

579 ± 16 Ma (Sm–Nd isochronage)

Passive continentalmargin

Meffre et al. (2004)

Western Victoria and South Australia Tholeiitic to transitionalalkaline basalts,limestones, volcaniclasticand picritic lavas

Ca. 589–501 Ma Rift Direen and Crawford (2003)

Qilian-QaidamThe western segment of North Qilian Alkaline and tholeiitic

basalts, volcaniclastic,dolomitic limestone,sandstone, siltstone,iron-ore layer

600–583 Ma (Zircon SIMS) Continental rift This study

South ChinaYangtze Gorge (Doushantuo Formation) Volcanic ash, shale,

limestone555.2 ± 6.1 Ma and 621 ± 7 Ma(SIMS)

? Zhang et al. (2005)

TarimWE Tarim (Aksu area) Transitional basalts,

sandstone, siltstone,dolostone

615.2 ± 4.8 Ma, 614.4 ± 9.1 Ma(SHRIMP)

The waning stage ofplume

Xu et al. (2013)

NE Tarim (Quruqtagh area) Basaltic and andesiticlavas, pyroclastic, siltstone

615 ± 6 Ma (SHRIMP) Related to the Rodinianbreakup

Xu et al. (2009)

be

amatnO1te(rbgoiow2

GStoa2StUgbr

assembly and breakup of different parts of a supercontinent are notonly recognized in the cycle of the Gondwana, but also exist in theevolution of the Rodinia supercontinent (Ernst et al., 2008).

AK

QR

AI

WA

GZ

KT

Australia

South ChinaQilian-Qaidam

Tarim

Proto-PacificOcean

EastAntarctica

Passive continental margin

Middle oceanic ridgeRifting-related volcanic-sedimentary sequence (ca. 600-580 Ma)

600-550 Ma

NQ

?

Fig. 12. Reconstruction of the East Gondwana at ca. 600–580 Ma (modified afterFergusson et al., 2009). Relative positions of Australia, East Antarctica, and SouthChina are based on the proposal by Li et al. (1999, 2003, 2008b). The Tarim had been

and sandstone

e developed in a passive continental margin setting (Fergussont al., 2009).

These magmatism during the latest Neoproterozoic describedbove apparently record the simultaneous rifting on the easternargin of Australia–Antarctica and imply the uniform affinities

mong these blocks before continental drifting. It is worth notinghat the rifting-related records slightly predates the second conti-ental breakup around 550 Ma in the periphery of the Proto-Pacificcean (Bond et al., 1984, 1985; Meert et al., 1994; Powell et al.,994; Veevers et al., 1997). The Yushigou ophiolite (550 Ma) ofhe North Qilian and the Marlborough terrane (562 Ma) of east-rn Australia may represent the initial opening of oceanic basinBruce et al., 2000; Shi et al., 2004; Song et al., 2013). Overall,enewed rifting related to the opening of the marginal sea coulde indicated by the 615–580 Ma magmatism occurred in east mar-in of proto-Gondwana (Table 4), which may record the separationf the Chinese blocks from there. The protracted history of rift-ng can be interpreted by the process of episodically separatingf microcontinents such as the Qilian-Qaidam, which faced theide proto-Pacific Ocean (Powell et al., 1994; Direen and Crawford,

003; Fergusson et al., 2009).Fig. 12 illustrates the configuration of the eastern proto-

ondwana at ca. 600–580 Ma. The palaeogeographic positions ofouth China, East Antarctica and Laurentia are in general consis-ent with the proposal by Li et al. (1999, 2003, 2008b), althoughther configuration models about Tarim and South China have beenlso suggested (Lu et al., 2008; Li et al., 2013a,b,c; Zhang et al.,013a,b; Yao et al., 2014). The original unity between Australia,outh China, Qilian-Qaidam, and Tarim blocks was suggested byhe plume-related radial dyke swarms (∼825 Ma) (Lu et al., 2008).

ntil 600 Ma South China was far from both Laurentia and Australiaiven by the lack of rift magmatism. At that time, the Qilian-Qaidamlock, as a connection between Australian and South China, beganifting and dispersal into the Proto-Pacific Ocean. Considering the

compression of the Pan-African orogeny (500–700 Ma) in the inte-rior of Gondwanaland (Hoffman, 1991; Veevers, 2003; Li et al.,2008b), it seems appropriate to put these blocks at the externalmargin of continent in the extensional regime. The simultaneous

tentatively placed in close to the eastern Australia (Lu et al., 2008). The 600–580 Mapassive margin volcanics include: WA = Mt Wright and Arrowsmith in western NewSouth Wales; GZ = Glenelg Zone in western Victoria; KT = King Island-Tasmania;NQ = North Qilian; AI = Anakie Inlier in northeastern Australia; AK = Aksu area in WETarim; QR = Quruqtagh area in NE Tarim (also see Table 4).

6 n Rese

A

wycRca4

A

i2

R

A

B

B

B

C

C

C

C

C

C

CC

C

D

E

F

F

F

F

2 X. Xu et al. / Precambria

cknowledgements

We thank Xianhua Li and his laboratory group for helpingith SIMS dating, G.Z. Li and W.P. Zhu for Sr–Nd isotopic anal-

ses. We also thank Editors and Reviewers for their constructiveomments. This study was supported by the Major State Basicesearch Development Program (2015CB856105), Basic geologi-al survey program of China Geological Survey (1212011121258)nd National Natural Science Foundation of China (Grant Nos.1372060, 40825007, 41121062, 41130314).

ppendix A. Supplementary data

Supplementary data associated with this article can be found,n the online version, at http://dx.doi.org/10.1016/j.precamres.014.11.017.

eferences

rndt, N.T., Christensen, U., 1992. The role of lithospheric mantle in continen-tal flood volcanism: thermal and geochemical constraints. J. Geophys. Res. 97,10967–10981.

ond, G.C., Nickeson, P.A., Kominz, M.A., 1984. Breakup of a supercontinent between625 Ma and 555 Ma: new evidence and implications for continental histories.Earth Planet. Sci. Lett. 70, 325–345.

ond, G.C., Christie-Blick, N., Kominz, M.A., Devlin, W.J., 1985. An early Cambrian riftto post-rift transition in the Cordillera of western North America. Nature 315,742–745.

ruce, M.C., Niu, Y., Harbort, T.A., Holcombe, R.J., 2000. Petrological, geochemicaland geochronological evidence for a Neoproterozoic ocean basin recorded inthe Marlborough terrane of the northern New England Fold Belt. Aust. J. EarthSci. 47, 1053–1064.

awood, P.A., 2005. Terra Australis Orogen: Rodinia breakup and development ofthe Pacific and Iapetus margins of Gondwana during the Neoproterozoic andPaleozoic. Earth Sci. Rev. 69, 249–279.

hen, N.S., Wang, Q.Y., Chen, Q., Li, X.Y., 2007. Components and metamorphism ofthe basements of the Qaidam and Oulongbuluke micro-continental blocks, anda tentative interpretation of paleocontinental evolution in NW-Central China.Earth Sci. Front. 14, 43–55 (in Chinese with English abstract).

hen, N.S., Gong, S.L., Sun, M., Li, X.Y., Xia, X.P., Wang, Q.Y., Wu, F.Y., Xu, P.,2009a. Precambrian evolution of the Quanji Block, northeastern margin of Tibet:insights from zircon U–Pb and Lu–Hf isotope compositions. J. Asian Earth Sci. 35,367–376.

hen, D.L., Liu, L., Sun, Y., 2009b. Geochemistry and zircon U–Pb dating and its impli-cations of the Yukahe HP/UHP terrane, the North Qaidam, NW China. J. AsianEarth Sci. 35, 259–272.

hen, Y.X., Xia, X.H., Song, S.G., 2012. Petrogenesis of Aoyougou high-silica adakitein the North Qilian Orogen, NW China: evidence for decompression melting ofoceanic slab. Chin. Sci. Bull. 57, 2289–2301.

hen, Y.X., Song, S.G., Niu, Y.L., Wei, C.J., 2014. Melting of continental crust duringsubduction initiation: a case study from the Chaidanuo peraluminous granite inthe North Qilian suture zone. Geochim. Cosmochim. Acta 132, 311–336.

ox, K.G., 1980. A model for flood basalt volcanism. J. Petrol. 21, 629–650.rawford, A.J., Berry, R.F., 1992. Tectonic implications of Late Proterozoic–Early

Palaeozoic igneous rock associations in western Tasmania. In: Fergusson, C.L.,Glen, R.A. (Eds.), The Palaeozoic Eastern Margin of Gondwanaland: Tectonicsof the Lachlan Fold Belt, Southeastern Australia and Related Orogens. Tectono-physics, 214, pp. 37–56.

rawford, A.J., Stevens, B., Fanning, M., 1997. Geochemistry and tectonic setting ofsome Neoproterozoic and Early Cambrian volcanic in Western New South Wales.Aust. J. Earth Sci. 44, 831–852.

ireen, N.G., Crawford, A.J., 2003. Fossil seaward-dipping reflector sequences pre-served in southeastern Australia: a 600 Ma volcanic passive margin in easternGondwanaland. J. Geol. Soc. 160, 985–990.

rnst, R.E., Wingate, W.T.D., Buchan, K.L., Li, Z.X., 2008. Global record of 1600–700 MaLarge Igneous Provinces (LIPs): implications for the reconstruction of the pro-posed Nuna (Columbia) and Rodinia supercontinents. Precambrian Res. 160,159–178.

eng, Y.M., He, S.P., 1996. Geotectonics and Orogeny of the Qilian Mountains. Geo-logical Publish House, Beijing, pp. 135 (in Chinese).

ergusson, C.L., Offler, R., Green, T.J., 2009. Late Neoproterozoic passive margin ofEast Gondwana: geochemical constraints from the Anakie Inlier, central Queens-land, Australia. Precambrian Res. 168, 301–312.

oden, J., Barovich, K., Jane, M., Halloran, G.O., 2001. Sr-isotopic evidence for Late

Neoproterozoic rifting in the Adelaide Geosyncline at 586 Ma: implications fora Cu ore forming fluid flux. Precambrian Res. 106, 291–308.

rimmel, H.E., Zartman, R., Späth, E., 2001. The Richtersveld igneous complex, SouthAfrica: U–Pb zircon and geochemical evidence for the beginning of Neoprotero-zoic continental breakup. J. Geol. 109, 493–508.

arch 257 (2015) 47–64

Gibson, S.A., Thompson, R.N., Dickin, A.P., Leonardos, O.H., 1995. High-Ti and low-Timafic potassic magmas: key to plume-lithosphere interactions and continentalflood-basalt genesis. Earth Planet. Sci. Lett. 136, 149–165.

Guo, J.J., Zhao, F.Q., Li, H.K., 1999. Jinningian collisional granite belt in the easternsector of the Central Qilian Massif and its implication. Acta Geosci. Sin. 20, 10–15(in Chinese with English abstract).

Hart, S.R., 1988. Heterogenous mantle domains: signature, genesis and mixingchronologies. Earth Planet. Sci. Lett. 90, 273–296.

Hawkesworth, C.J., Lightfoot, P.C., Fedorenko, V.A., Blake, S., Naldrett, A.J., Doherty,W., Gorbachev, N.S., 1995. Magma differentiation and mineralisation in theSiberian continental flood basalts. Lithos 34, 61–88.

Herzberg, C., Asimow, P.D., 2008. Petrology of some oceanic island basalts:PRIMELT2. XLS software for primary magma calculation. Geochem. Geophys.Geosyst. 9, Q09001.

Herzberg, C., O’Hara, M.J., 2002. Plume-associated ultramafic magmas of Phanero-zoic age. J. Petrol. 43, 1857–1883.

Herzberg, C., Asimow, P.D., Arndt, N., Niu, Y., Lesher, C.M., Fitton, J.G., Saun-ders, A.D., 2007. Temperature in ambient mantle and plumes: constraintsfrom basalts, picrites, and komatiites. Geochem. Geophys. Geosyst., Q02006,http://dx.doi.org/10.1029/2006GC001390.

Hill, R.I., Campbell, I.H., Davies, G.F., Griffiths, R.W., 1992. Mantle plumes and conti-nental tectonics. Science 256, 186–193.

Hoffman, P.F., 1991. Did the breakout of Laurentia turn Gondwanaland inside-out?Nature 252, 1409–1412.

Hofmann, A.W., 1988. Chemical differentiation of the Earth: the relationshipbetween mantle, continental crust, and oceanic crust. Earth Planet. Sci. Lett.90, 297–314.

Humphreys, E.R., Niu, Y.L., 2009. On the composition of ocean island basalts (OIB):the effects of lithospheric thickness variation and mantle metasomatism. Lithos112, 118–136.

Lee, S.R., Cho, M., Cheong, C.S., Kim, H., Wingate, M.T.D., 2003. Age, geochemistry, andtectonic significance of Neoproterozoic alkaline granitoids in the northwesternmargin of the Gyeonggi massif, South Korea. Precambrian Res. 122, 297–310.

Lee, C.T.A., Luffi, P., Plank, T., Dalton, H., Leeman, W.P., 2009. Constraints on thedepths and temperatures of basaltic magma generation on Earth and other ter-restrial planets using new thermobarometers for mafic magmas. Earth Planet.Sci. Lett. 279, 20–33.

Li, Z.X., Zhang, L.H., Powell, C.M., 1995. South China in Rodinia: part of the missinglink between Australia–East Antarctica and Laurentia? Geology 23, 407–410.

Li, Z.X., Li, X.H., Kinny, P.D., Wang, J., 1999. The breakup of Rodinia: did itstart with a mantle plume beneath South China? Earth Planet. Sci. Lett. 173,171–181.

Li, Z.X., Li, X.H., Kinny, P.D., 2003. Geochronology of Neoproterozoic syn-rift magma-tism in the Yangtze Craton, South China and correlations with other continents:evidence for a mantle superplume that broke up Rodinia. Precambrian Res. 122,85–109.

Li, X.H., Su, L., Chung, S.L., Li, Z.X., Liu, Y., Song, B., Liu, D.Y., 2005. Formation of theJinchuan ultramafic intrusion and the world’s third largest Ni–Cu sulfide deposit:associated with the ∼825 Ma south China mantle plume? Geochem. Geophys.Geosyst. 6, Q11004, http://dx.doi.org/10.1029/2005GC001006.

Li, H.K., Lu, S.N., Xiang, Z.Q., Zhou, H.Y., Li, H.M., Liu, D.Y., Song, B., Zheng, J.K., Gu,Y., 2007. SHRIMP U–Pb geochronological research on detrital zircons from theBeidahe complex-group in the western segment of the North Qilian Mountains,Northwest China. Geol. Rev. 53, 132–140 (in Chinese with English abstract).

Li, X.H., Li, W.X., Li, Z.X., Liu, Y., 2008a. 850–790 Ma bimodal volcanic and intrusiverocks in northern Zhejiang, South China: a major episode of continental riftmagmatism during the breakup of Rodinia. Lithos 102, 341–357.

Li, Z.X., Bogdanova, S.V., Collins, A.S., Davidson, A., De Waele, B., Ernst, R.E., Fitzsi-mons, I.C.W., Fuck, R.A., Gladkochub, D.P., Jacobs, J., Karlstrom, K.E., Lu, S.,Natapov, L.M., Pease, V., Pisarevsky, S.A., Thrane, K., Vernikovsky, V., 2008b.Assembly, configuration, and break-up history of Rodinia: a synthesis. Precam-brian Res. 160, 179–210.

Li, X.H., Liu, Y., Li, Q.L., Guo, C.H., Chamberlain, K.R., 2009. Precise deter-mination of Phanerozoic zircon Pb/Pb age by multi-collector SIMS with-out external standardization. Geochem. Geophys. Geosyst. 10, Q04010,http://dx.doi.org/10.1029/2009GC002400.

Li, X.H., Li, W.X., Li, Q.L., Wang, X.C., Liu, Y., Yang, Y.H., 2010a. Petrogenesis and tec-tonic significance of the ∼850 Ma Gangbian alkaline complex in South China:evidence from in situ zircon U–Pb dating, Hf–O isotopes and whole-rock geo-chemistry. Lithos 114, 1–15.

Li, Q.L., Li, X.H., Liu, Y., Tang, G.Q., Yang, J.H., Zhu, W.G., 2010b. Precise U–Pb and Pb–Pbdating of Phanerozoic baddeleyite by SIMS with oxygen flooding technique. J.Anal. At. Spectrom. 25, 1107–1113.

Li, W.X., Li, X.H., Li, Z.X., 2010c. Ca. 850 Ma bimodal volcanic rocks in northeasternJiangxi Province, South China: initial extension during the breakup of Rodinia.Am. J. Sci. 310, 951–980.

Li, X.H., Tang, G.Q., Gong, B., Yang, Y.H., Hou, K.J., Hu, Z.C., Li, Q.L., Liu, Y., Li, W.X.,2013a. Qinghu zircon: a working reference for microbeam analysis of U–Pb ageand Hf and O isotopes. Chin. Sci. Bull. 58, 4647–4654.

Li, Z.X., Evans, D.A.D., Halverson, G.P., 2013b. Neoproterozoic glaciations in a revisedglobal palaeogeography from the breakup of Rodinia to the assembly of Gond-

wanaland. Sediment. Geol. 294, 219–232.

Li, X.W., Mo, X.X., Yu, X.H., Ding, Y., Huang, X.F., Wei, P., He, W.Y., 2013c. Geochrono-logical, geochemical and Sr–Nd–Hf isotopic constraints on the origin of theCretaceous intraplate volcanism in West Qinling, Central China: implicationsfor asthenosphere–lithosphere interaction. Lithos 177, 381–401.

n Rese

L

L

L

L

L

M

M

M

M

N

N

N

N

P

P

P

P

P

P

P

R

R

S

S

S

S

S

S

S

S

S

X. Xu et al. / Precambria

ing, W.L., Gao, S., Zhang, B.R., Li, H.M., Liu, Y., Cheng, J.P., 2003. Neoproterozoic tec-tonic evolution of the northwestern Yangtze craton, South China: implicationsfor amalgamation and break-up of the Rodinia Supercontinent. Precambrian Res.122, 111–140.

oucks, R.R., 1990. Discrimination of ophiolitic from nonophiolitic ultramafic-maficallochthons in orogenic belts by the Al/Ti ratio in clinopyroxene. Geology 18,346–349.

u, S.N., Li, H.K., Zhang, C.L., Niu, G.H., 2008. Geological and geochronological evi-dence for the Precambrian evolution of the Tarim Craton and surroundingcontinental fragments. Precambrian Res. 160, 94–107.

udwig, K.R., 2001. Users Manual for Isoplot/Ex rev. 2.49. Berkeley GeochronologyCentre, pp. 56, Special Publication 1.

ugmair, G.W., Marti, K., 1978. Lunar initial 143Nd/144Nd: differential evolution ofthe lunar crust and mantle. Earth Planet. Sci. Lett. 39, 349–357.

eert, J.G., van der Voo, R., Payne, T.W., 1994. Paleomagnetism of the Catoctin vol-canic province: a new Vendian-Cambrian apparent polar wander path for NorthAmerica. J. Geophys. 99, 4625–4641.

effre, S., Direen, N.G., Crawford, A.J., Kamenetsky, V., 2004. Mafic volcanic rockson King Island, Tasmania: evidence for 579 Ma break-up in east Gondwana.Precambrian Res. 135, 177–191.

elluso, L., Mahoney, J.J., Dallai, L., 2006. Mantle sources and crustal input asrecorded in high-Mg Deccan Traps basalts of Gujarat (India). Lithos 89, 259–274.

iyashiro, A., 1974. Volcanic rock series in island arcs and active continental mar-gins. Am. J. Sci. 274, 321–355.

iu, Y.L., Batiza, R., 1997. Trace element evidence from seamounts for recycledoceanic crust in the eastern equatorial Pacific mantle. Earth Planet. Sci. Lett.148, 471–483.

iu, Y.L., O’Hara, M.J., 2008. Global correlations of ocean ridge basalt chemistry withaxial depth: a new perspective. J. Petrol. 49, 633–664.

iu, Y.L., O’Hara, M.J., 2009. MORB mantle hosts the missing Eu (Sr, Nb, Ta andTi) in the continental crust: new perspectives on crustal growth, crust-mantledifferentiation and chemical structure of oceanic upper mantle. Lithos 112, 1–17.

iu, Y.L., Wilson, M., Humphreys, E.R., O’Hara, M.J., 2011. The origin of intra-plateocean island basalts (OIB): the lid effect and its geodynamic implications. J.Petrol. 52, 1443–1468.

ark, J.K., Buchan, K.L., Harlan, S.S., 1995. A proposed giant radiating dyke swarmfragmented by the separation of Laurentia and Australia based on paleomag-netism of ca. 780 Ma mafic intrusions in western North America. Earth Planet.Sci. Lett. 132, 129–139.

earce, J.A., Norry, M.J., 1979. Petrogenetic implications of Ti, Zr, Y and Nb variationsin volcanic rocks. Contrib. Mineral. Petrol. 69, 33–47.

owell, C.M., Li, Z.X., McElhinny, M.W., Meert, J.G., Park, J.K., 1993. Paleomagneticconstraints on the Neoproterozoic breakup of Rodinia and the mid-Cambrianformation of Gondwanaland. Geology 21, 889–892.

owell, C.M., Preiss, W.V., Gatehouse, C.G., Krapez, B., Li, Z.X., 1994. South Aus-tralian record of a Rodinian epicontinental basin and its mid-Neoproterozoicbreakup (∼700 Ma) to form the Palaeo-Pacific Ocean. Tectonophysics 237,113–140.

reiss, W.V., 2000. The Adelaide Geosyncline of South Australia and its significancein Neoproterozoic continental reconstruction. Precambrian Res. 100, 21–63.

utirka, K.D., 2005. Mantle potential temperatures at Hawaii, Iceland, and themid-ocean ridge system, as inferred from olivine phenocrysts: evidencefor thermally driven mantle plume. Geochem. Geophys. Geosyst., Q05L08,http://dx.doi.org/10.1029/005GC000915.

utirka, K.D., Perfit, M., Ryerson, F.J., Jackson, M.G., 2007. Ambient and excess man-tle temperatures, olivine thermometry, and active vs. passive upwelling. Chem.Geol. 241, 177–206.

ollinson, H.R., 1993. Using Geochemical Data: Evaluation, Presentation, Interpre-tation. Longman Geochemistry Society, London, pp. 184–186.

udnick, R.L., Gao, S., 2003. Composition of the continental crust. Treatise Geochem.3, 1–64.

aunders, A.D., Tarney, J., Kerr, A.C., Kent, R.W., 1996. The formation and fate of largeoceanic igneous provinces. Lithos 37, 81–95.

¸ engör, A.M.C., 1990. Plate tectonics and orogenic research after 25 years – a Tethyanperspective. Earth Sci. Rev. 27, 1–201.

harma, M., Basu, A.R., Nesterenko, G.V., 1992. Temporal Sr-, Nd- and Pb-isotopicvariations in the Siberian flood basalts: implications for the plume-source char-acteristics. Earth Planet. Sci. Lett. 113, 365–381.

hervais, J.W., 1982. Ti–V plots and the petrogenesis of modern and ophiolitic lavas.Earth Planet. Sci. Lett. 59, 101–118.

hi, R.D., Yang, J.S., Wu, C.L., 2004. First SHRIMP dating for the formation of the LateSinian Yushigou Ophiolite North Qilian Mountains. Acta Geol. Sin. 78, 649–657(in Chinese with English abstract).

hu, L.S., Faure, M., Yu, J.H., Jahn, B.M., 2011. Geochronological and geochemical fea-tures of the Cathaysia block (South China): new evidence for the Neoproterozoicbreakup of Rodinia. Precambrian Res. 187, 263–276.

láma, J., Kosler, J., Condon, D.J., Crowley, J.L., Gerdes, A., Hanchar, J.M., Horstwood,M.S.A., Morris, G.A., Nasdala, L., Norberg, N., Schaltegger, U., Schoene, B., Tubrett,M.N., Whitehouse, M.J., 2008. Plesovice zircon – a new natural reference materialfor U–Pb and Hf isotopic microanalysis. Chem. Geol. 249, 1–35.

ong, S.G., Zhang, L.F., Niu, Y.L., 2004a. Ultra-deep origin of garnet peridotite from

the North Qaidam ultrahigh-pressure belt, Northern Tibetan Plateau, NW China.Am. Mineral. 89, 1330–1336.

ong, S.G., Zhang, L.F., Niu, Y.L., Song, B., Zhang, G.B., Wang, Q.J., 2004b. Zircon U–PbSHRIMP ages of eclogites from the North Qilian Mountains, NW China and theirtectonic implication. Chin. Sci. Bull. 49, 848–852.

arch 257 (2015) 47–64 63

Song, S.G., Zhang, L.F., Niu, Y.L., Su, L., Song, B., Liu, D.Y., 2006. Evolution from oceanicsubduction to continental collision: a case study of the Northern Tibetan Plateauinferred from geochemical and geochronological data. J. Petrol. 47, 435–455.

Song, S.G., Zhang, L.F., Niu, Y., Wei, C.J., Liou, J.G., Shu, G.M., 2007. Eclogite andcarpholite-bearing metasedimentary rocks in the North Qilian suture zone, NWChina: implications for Early Palaeozoic cold oceanic subduction and watertransport into mantle. J. Metamorphic Geol. 25, 547–563.

Song, S.G., Niu, Y.L., Zhang, L.F., Wei, C.J., Liou, J.G., Su, L., 2009. Tectonic evolutionof Early Paleozoic HP metamorphic rocks in the North Qilian Mountains, NWChina: new perspectives. J. Asian Earth Sci. 35, 334–353.

Song, S.G., Su, L., Li, X.H., Zhang, G.B., Niu, Y.L., Zhang, L.F., 2010. Tracing the 850-Ma continental flood basalts from a piece of subducted continental crust in theNorth Qaidam UHPM belt, NW China. Precambrian Res. 183, 805–816.

Song, S.G., Su, L., Li, X.H., Niu, Y.L., Zhang, L.F., 2012. Grenville-age orogenesis in theQaidam-Qilian block: the link between South China and Tarim. Precambrian Res.220–221, 9–22.

Song, S.G., Niu, Y.L., Su, L., Xia, X.H., 2013. Tectonics of the North Qilian orogen, NWChina. Gondwana Res. 23, 1378–1401.

Song, S.G., Niu, Y.L., Su, L., Zhang, C., Zhang, L.F., 2014. Continental orogenesis fromocean subduction, continent collision/subduction, to orogen collapse, and oro-gen recycling: the example of the North Qaidam UHPM belt, NW China. EarthSci. Rev. 129, 59–84.

Stacey, J.S., Kramers, J.D., 1975. Approximation of terrestrial lead isotope evolutionby a two-stage model. Earth Planet. Sci. Lett. 26, 207–221.

Steiger, R.H., Jäger, E., 1977. Subcommission on geochronology: convention on theuse of decay constants in geo- and cosmochronology. Earth Planet. Sci. Lett. 36,359–362.

Sun, S.S., McDonough, W.F., 1989. Chemical and Isotopic Systematics of OceanicBasalts: Implications for Mantle Composition and Processes. Geological Society,London, pp. 313–345, Special Publications 42.

Tseng, C.Y., Yang, H.Y., Wan, Y.S., Liu, D.Y., Wen, D.J., Lin, T.C., Tung, K.A., 2006. Findingof Neoproterozoic (∼775 Ma) magmatism recording in metamorphic complexesfrom the North Qilian orogen: evidence from SHRIMP zircon U–Pb dating. Chin.Sci. Bull. 51, 963–970.

Tung, K.A., Yang, H.J., Yang, H.Y., Liu, D.Y., Zhang, J.X., Wan, Y.S., Tseng, C.Y.,2007. SHRIMP U–Pb geochronology of the zircons from the Precambrian base-ment of the Qilian Block and its geological significances. Chin. Sci. Bull. 52,2687–2701.

Tung, K.A., Yang, H.Y., Liu, D.Y., Zhang, J.X., Yang, H.J., Shau, Y.H., Tseng, C.Y., 2013.The Neoproterozoic granitoids from the Qilian block, NW China: evidence for alink between the Qilian and South China blocks. Precambrian Res. 235, 163–189.

Turner, S., Hawkesworth, C., 1995. The nature of the sub-continental mantle: con-straints from the major-element composition of continental flood basalts. Chem.Geol. 120, 295–314.

Veevers, J.J., 2003. Pan-African is Pan-Gondwanaland: oblique convergence drivedrotating during 650–500 Ma assembly. Geology 31, 501–504.

Veevers, J.J., Walter, M.R., Scheibner, E., 1997. Neoproterozoic tectonics ofAustralia–Antarctica and Laurentia and the 560 Ma birth of the Pacific Oceanreflect 400 m.y. Pangean supercycle. J. Geol. 105, 225–242.

Wan, Y.S., Xu, Z.Q., Yang, J.S., Zhang, J.X., 2001. Ages and compositions of the Pre-cambrian high-grade basement of the Qilian terrane and its adjacent areas. ActaGeol. Sin. 75, 375–384.

Wan, Y.S., Zhang, J.X., Yang, J.S., Xu, Z.Q., 2006. Geochemistry of high-grade meta-morphic rocks of the North Qaidam Mountains and their geological significance.J. Asian Earth Sci. 28, 174–184.

Wang, J., Li, Z.X., 2003. History of Neoproterozoic rift basins in South China: impli-cations for Rodinia break-up. Precambrian Res. 122, 141–158.

Wang, X.C., Li, X.H., Li, W.X., Li, Z.X., 2007. Ca. 825 Ma komatiitic basalts in SouthChina: first evidence for >1500 ◦C mantle melts by a Rodinian mantle plume.Geology 35, 1103–1106.

Wang, X.C., Li, X.H., Li, W.X., Li, Z.X., Liu, Y., Yang, Y.H., Liang, X.R., Tu, X.L.,2008. The Bikou basalts in the northwestern Yangtze block, South China:remnants of 820–810 Ma continental flood basalts? Geol. Soc. Am. Bull. 120,1478–1492.

Wang, X.C., Li, X.H., Li, W.X., Li, Z.X., 2009. Variable involvements of mantle plumesin the genesis of mid-Neoproterozoic basaltic rocks in South China: a review.Gondwana Res. 15, 381–394.

Wang, X.C., Li, X.H., Li, Z.X., Liu, Y., Yang, Y.H., 2010. The Willouran basic province ofSouth Australia: its relation to the Guibei large igneous province in South Chinaand the breakup of Rodinia. Lithos 119, 569–584.

Wang, X.C., Li, Z.X., Li, X.H., Li, J., Liu, Y., Long, W.G., Zhou, J.B., Wang, F., 2012. Temper-ature, pressure, and composition of the mantle source region of Late Cenozoicbasalts in Hainan Island, SE Asia: a consequence of a young thermal MantlePlume close to subduction zones? J. Petrol. 53, 177–233.

Wang, X.C., Li, Z.X., Li, J., Pisarevsky, S.A., Wingate, M.T.D., 2014. Genesis of the 1.21 GaMarnda Moorn large igneous province by plume–lithosphere interaction. Pre-cambrian Res. 241, 85–103.

White, W.M., Duncan, R.A., 1996. Geochemistry and geochronology of the SocietyIslands: new evidence for deep mantle recycling. Geophys. Monogr. Ser. 95,183–206.

White, R.S., McKenzie, D.P., 1989. Magmatism at rift zones: the generation of volcanic

continental margins and flood basalts. J. Geophys. Res. 94, 7685–7730.

Wiedenbeck, M., Alle, P., Corfu, F., Griffin, W.L., Meier, M., Oberli, F., Vonquadt, A.,Roddick, J.C., Speigel, W., 1995. Three natural zircon standards for U–Th–Pb,Lu–Hf, trace-element and REE analyses. Geostand. Newslett. 19, 1–23.

Wilson, M., 1989. Igneous Petrogenesis. Unwin Hyman, London.

6 n Rese

W

W

W

X

X

X

X

X

X

X

X

4 X. Xu et al. / Precambria

inchester, J.A., Floyd, P.A., 1976. Geochemical magma type discrimination: appli-cation to altered and metamorphosed basic igneous rocks. Earth Planet. Sci. Lett.28, 459–469.

ingate, M.T.D., Campbell, I.H., Compston, W., Gibson, G.M., 1998. Ion micro-probe U–Pb ages for Neoproterozoic basaltic magmatism in south-centralAustralia and implications for the breakup of Rodinia. Precambrian Res. 87,135–159.

u, H.Q., Feng, Y.M., Song, S.G., 1993. Metamorphism and deformation of blueschistbelts and their tectonic implications, north Qilian Mountains, China. J. Metamor-phic Geol. 11, 523–536.

ia, L.Q., Xia, Z.C., Zhao, J.T., Xu, X.Y., Yang, H.Q., Zhao, D.H., 2000. Determination ofthe features of the Proterozoic continental flood basalts in the western sector ofNorth Qilian Mountains. Sci. Chin. (Ser. D) 30, 1–8 (in Chinese).

ia, X.H., Sun, N., Song, S.G., Xiao, X.C., 2012. Age and Tectonic Setting of theAoyougou-Erzhihaladaban Ophiolite in the Western North Qilian Mountains,NW China. Acta Sci. Nat. Univ. Pekinensis 48, 757–769 (in Chinese).

iang, Z.Q., Lu, S.N., Li, H.K., Li, H.M., Song, B., Zheng, J.K., 2007. SHRIMP U–Pb zirconage of gabbro in Aoyougou in the western segment of the North Qilian Moun-tains, China and its geological implications. Geol. Bull. Chin. 26, 1686–1691 (inChinese with English abstract).

iao, X.C., Chen, G.M., Zhu, Z.Z., 1978. A preliminary study on the tectonics ancientophiolites in the Qilian Mountain, northwest China. Acta Geol. Sin. 4, 279–295(in Chinese with English abstract).

iao, W.J., Windley, B.F., Yong, Y., Yan, Z., Yuan, C., Liu, C.Z., Li, J.L., 2009. Early Paleo-zoic to Devonian multiple-accretionary model for the Qilian Shan, NW China. J.Asian Earth Sci. 35, 323–333.

u, Y.G., Chung, S.L., Jahn, B.M., Wu, G.Y., 2001. Petrologic and geochemical con-straints on the petrogenesis of Permian–Triassic Emeishan flood basalts insouthwestern China. Lithos 58, 145–168.

u, B., Jian, P., Zheng, H.F., Zou, H.B., Zhang, L.F., Liu, D.Y., 2005. U-Pb zir-con geochronology and geochemistry of Neoproterozoic volcanic rocks inthe Tarim Block of northwest China: implications for the breakup of

Rodinia supercontinent and Neoproterozoic glaciations. Precambrian Res. 136,107–123.

u, B., Xiao, S.H., Zou, H.B., Chen, Y., Li, Z.X., Song, B., Liu, D.Y., Zhou, C.M., Yuan,X.L., 2009. SHRIMP zircon U–Pb age constraints on Neoproterozoic Quruqtaghdiamictites in NW China. Precambrian Res. 168, 247–258.

arch 257 (2015) 47–64

Xu, B., Zou, H.B., Chen, Y., He, J.Y., Wang, Y., 2013. The Sugetbrak basalts fromnorthwestern Tarim Block of northwest China: geochronology, geochemistryand implications for Rodinia breakup and ice age in the Late Neoproterozoic.Precambrian Res. 236, 214–226.

Yao, W.H., Li, Z.X., Li, W.X., Li, X.H., Yang, J.H., 2014. From Rodinia to Gondwanaland:A tale of detrital zircon provenance analyses from the southern Nanhua Basin,South China. Am. J. Sci. 314, 278–313.

Yin, A., Dang, Y.Q., Wang, L.C., Jiang, W.M., Zhou, S.P., Chen, X.H., Gehrels, E.G.,McRivertte, M.W., 2008. Cenozoic tectonic evolution of Qaidam basin and itssurrounding regions (Part 1): The southern Qilian Shan-Nan Shan thrust beltand northern Qaidam basin. Geol. Soc. Am. Bull. 120, 813–846.

Zhang, J.X., Wan, Y.S., Xu, Z.Q., Yang, J.S., Meng, F.C., 2001. Discovery of basic granuliteand its formation age in Delingha area, North Qaidam Mountains. Acta Petrol.Sin. 17, 453–458 (in Chinese with English abstract).

Zhang, S.H., Jiang, G.P., Zhang, J.M., Song, B., Kennedy, M.J., Blick, N.C., 2005. U–Pbsensitive high-resolution ion microprobe ages from the Doushantuo Forma-tion in South China: Constraints on late Neoproterozoic glaciations. Geology33, 473–476.

Zhang, J.X., Meng, F.C., Wan, Y.S., 2007. A cold Early Palaeozoic subduction zone inthe North Qilian Mountains, NW China: petrological and U–Pb geochronologicalconstraints. J. Metamorphic Geol. 25, 285–304.

Zhang, J.X., Gong, J.H., Yu, S.Y., Li, H.K., Hou, K.J., 2013a. Neoarchean-Paleoproterozoicmultiple tectonothermal events in the western Alxa block, North China Cratonand their geological implication: evidence from zircon U–Pb ages and Hf isotopiccomposition. Precambrian Res. 235, 36–57.

Zhang, S.H., Evans, D.A.D., Li, H.Y., Wu, H.C., Jiang, G.Q., Zhao, D.J., Raub, Q.L., T.D.Yang T.S., 2013b. Paleomagnetism of the late Cryogenian Nantuo Formation andpaleogeographic implications for the South China Block. J. Asian Earth Sci. 72,164–177.

Zhao, G., Cawood, P.A., 2012. Precambrian geology of China. Precambrian Res.222/223, 13–54.

Zimmer, M., Kröner, A., Jochum, K.P., Reischmann, T., Todt, W., 1995. The Gabal

Gerf complex: A Precambrian N-MORB ophiolite in the Nubian shield, NE Africa.Chem. Geol. 123, 29–51.

Zuo, G.C., Wu, M.B., Mao, J.W., Zhang, Z.C., 1999. Structural evolution of Early Paleo-zoic tectonic belt in the west section of northern Qilian area. Acta Geol. Gansu8, 6–13 (in Chinese).