oe

i c

chemese

Available online 23 June 2010

Keywords:Zircon LuHf isotopeGranitoid

ult Zone (JSFZ) in Zhejiang Province has been proposed to represent a suture

2006, 2008; Zheng et al., 2007) was based on geochronological data

Gondwana Research 19 (2011) 244259

Contents lists available at ScienceDirect

Gondwana

w.The South China Craton (SCC) is one of the most important cratonsin Asia. Its evolutionary history is critical for the understanding of theassembly and breaking-up of the supercontinents Rodinia andGondwana and has attracted numerous studies (e.g. Li et al., 1999;Yao et al., 1999; Zhang et al., 1999; Wang and Mou, 2001; Li et al.,2002a; Zhou et al., 2007; Rino et al., 2008; Santosh et al., 2009; Su etal., 2009; Wang et al., 2009). This craton comprises the Yangtze Blockin the northwest and the Cathaysia Block in the southeast (Fig. 1a),but the timing of the amalgamation of these two blocks is controversy.Two major groups favour either a Grenvillian (ca. 1.10.9 Ga) or aNeoproterozoic collision time (ca. 0.870.82 Ga), respectively. The

for metamorphic and intrusive rocks, e.g. the 866 Ma KAr age ofglaucophanes from blueschists and its PT path (Ma and Wang, 1994;Shu et al., 1994; Zhao and Cawood, 1999), the 828 Ma mac/ultramac rocks and the 825 Ma S-type granite intruding the SibaoGroup (Li et al., 1999). Active tectonic events and erosion subsequentto the collision further complicate the issue. These include anintraplate orogenic activity (Wuyi-Yunkai orogen in the easternSCC) at ca. 460415 Ma after the Neoproterozoic rifting (Wang et al.,2007b; Li et al., 2010), and vigorous magmatic activity that took placefrom the Early Permian to the Late Cretaceous, possibly associatedwith the subduction of the paleo-Pacic Plate under the eastern ankformer interpretation is mainly based on struisotopic geochronological data for the ophsuture (Shui, 1988; Chen and Jahn, 1998; Ye e

Corresponding author. Tel.: +852 2859 2195; fax: +E-mail address: minsun@hku.hk (M. Sun).

1342-937X/$ see front matter 2010 International Adoi:10.1016/j.gr.2010.06.004latter suggestion (e.g. Zhao and Cawood, 1999; Wang et al., 2004,1. IntroductionZhejiang ProvinceMesozoicSouth Chinaacross the fault zone were conducted to constrain the nature of the fault zone. Twelve Cretaceous granitoidbodies were sampled from the NW and SE sides of the fault zone, respectively, with composition ranging fromdiorite to granite (SiO2=56.276.6 wt.%). These granitoids yielded UPb ages ranging from 135100 Ma, witha systematic variation in zircon Hf isotopic compositions (Hf(t)=+6.9 to 7.0 in the NW side vs. +1.9 to12.9 in the SE side). The TDM2 values for the granitoids from the NW side are 0.34 to 1.33 Ga, with two peaksat ca. 876 and 1170 Ma respectively,whereas those from the SE side are 0.70 to 1.62 Ga,with a single peak at ca.1126 Ma. The Hf isotopic disparity for the two sidesmay indicate a fundamental difference in the lower crustalcompositions of the Yangtze and Cathaysia blocks, supporting that the JSFZ is possibly a suture zone betweenthe two blocks. Our results together with the available geological data suggest that the Mesoproterozoicmaterials are important for both the Yangtze and Cathaysia basement and the Neoproterozoic magmaticactivities were important in the Yangtze Block, possibly related to the break-up of the Rodinia supercontinent,but less signicant in the Cathaysia Block. This may imply that the two blocks have not completely juxtaposedin the Neoproterozoic.

2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.Received in revised form 8 June 2010Accepted 10 June 2010

analysis and whole-rock major- and trace-element measurement of early to middle Cretaceous felsic rocksReceived 18 March 2010 between the Yangtze and Cathaysia blocks in South China. In this study, in-situ zircon UPb and Hf isotopic

Article history: The JiangshanShaoxing FaZircon UPb and Hf isotopic study of MesSouth China: Geochemical contrast betwe

Jean Wong a, Min Sun a,, Guangfu Xing b, Xian-hua La Department of Earth Sciences, The University of Hong Kong, Hong Kong SAR, Chinab Institute of Geology and Mineral Resources, Nanjing, Chinac Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geod State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chin

a b s t r a c ta r t i c l e i n f o

j ourna l homepage: wwctural interpretation andiolitic rocks along thet al., 2007), whereas the

852 2517 6912.

ssociation for Gondwana Research.zoic felsic rocks from eastern Zhejiang,n the Yangtze and Cathaysia blocks,d, Guochun Zhao a, Kenny Wong a, Fuyuan Wu d

istry, Chinese Academy of Sciences, Guangzhou 510640, ChinaAcademy of Sciences, P.O. Box 9825, Beijing 100029, China

Research

e lsev ie r.com/ locate /grof the South China Craton (e.g. Jahn et al., 1976, 1990; Hs et al., 1990;Li et al., 2006;Wong et al., 2009). Widespread of these later magmaticrocks on the surface together with massive Quaternary sedimentarycover make the exposed Precambrian outcrops very limited andhinder the study of eld relationships between the two continentalblocks.

Another critical issue is which fault system, i.e. the JiangshanShaoxing Fault Zone (JSFZ) or the JiangshanXiangshan Fault Zone

Published by Elsevier B.V. All rights reserved.

245J. Wong et al. / Gondwana Research 19 (2011) 244259(JXFZ), represents the suture zone between the Yangtze andCathaysia blocks (e.g. Zhu et al., 1993; Liu et al., 2003). This studyreports zircon UPb and Hf isotopic data for eleven plutonic samplesand one rhyolite collected across the JSFZ from Zhejiang Province.Our data show contrasting Hf isotopic characteristics across the JSFZand thus may reect a systematic difference in the lower crustalcompositions between two continental blocks. Our results alsoindicate that Neoproterozoic magmatic activity was crucial for theYangtze Block but not so for the Cathaysia Block, which may have agreat implication for the evolutionary history of the South ChinaCraton.

Fig. 1. (a) Simplied geological map of the South China Craton (modied after Wang et al.,Cathaysia Block in the south. (b) Simplied local geological map of Zhejiang Province show2. Geological background

2.1. Regional geology

The South China Craton (SCC) comprises the Yangtze Block in thenorthwest and the Cathaysia Block in the southeast and is separatedfrom the North China Craton by the QinlingDabie Mountains(Fig. 1a). The basement rocks of the Yangtze Block, ranging fromArchean to Proterozoic, are mainly exposed in Kongling andDahongshan areas (e.g. Hutchison, 1989; Ames et al., 1996; Qiuet al., 2000; Zhang et al., 2006; Greentree and Li, 2008). Zheng, J.P.

2006). The South China Craton is composed of the Yangtze Block in the north and theing sample localities (after BGMRZP, 1989).

xing

.1E

.8E

.4E

.3E.4E9.79.7

.9E

.7E

.8E

.8E

.5E

246 J. Wong et al. / Gondwana Research 19 (2011) 244259et al. (2006) proposed that an Archean basement was probablywidelydistributed under the Yangtze Block, based on the 2.92.8 Ga UPbages and 2.63.5 Ga Hf model ages of xenocrystic zircons fromlamproite diatremes. The Precambrian rocks on the Cathaysia Block,however, mostly give Proterozoic ages (e.g. Chen and Jahn, 1998;Wanet al., 2007; Xu et al., 2007; Yu et al., 2007). Representative exposures,which occur in the northeastern and southwestern parts of the block,include the ca. 1.8 Ga granitoids and metavolcanic rocks of the Baducomplex in southwestern Zhejiang and northeastern Fujian (e.g. Li,1997; Li and Li, 2007) and the ca. 1.43 Ga granites in the Baobancomplex in Hainan Island (Ma et al., 1998; Li et al., 2002b).

In the eastern part of the craton lies the northeastsouthwesttrending JSFZ, a deep-seated structure running from the continentalshelf outside Hangzhou Gulf in eastern Zhejiang to Jiangshan Countyin southwestern Zhejiang, and extending to Jiangxi Province wherethe fault is locally known as the PingxiangGuangfeng Fault. The JSFZhas been considered to be the surcial manifestation of the YangtzeCathaysia suture, mainly based on the differences in lithology and agedata of the basement rocks in the two sides of the fault zone, i.e. theShuangxiwu Group and the Chencai Group on the Yangtze andCathaysia blocks, respectively (BGMRZP, 1989). The ShuangxiwuGroup to the northwest of the JSFZ is a sequence of deformed volcanicand sedimentary rocks terminated by an angular unconformity (e.g.Zhou and Zhu, 1993). The volcanic rocks, which exhibit calc-alkalineafnities, have been interpreted to represent an early Neoproterozoiccontinental arc (e.g. Shui, 1987; Li et al., 2009). The Chencai Group is ametamorphic complex exposed mainly to the southeastern margin ofthe JSFZ, consisting of gneiss, amphibolite, greenschist and marble

Table 1Summary of sample localities of the Mesozoic plutonic rocks along the JiangshanShao

Samples Sample/pluton name Location Sample localities (GPS)

NW domain06ZFR08 Baijuhuajian Fuyong 29628.5 N, 118391007ZSQ01 Shuangqiao Quzhou 29855.8 N, 118514506ZHC01 Eshan/Hengcunfu Tonglu 29480.6 N, 119342306ZZS01 Zhongshan/Hengcunfu Tonglu 294550.1 N, 11931006ZFC01 Fungcun/Huajiatang Tonglu 294719 N, 119474206ZMJ02 Majian Zhuji 294413.8 N, 11958106ZMJ05 Majian Zhuji 294413.8 N, 119581

SE domain06ZHG01 Honggong Honggong 29338.8 N, 118402606ZBZ01 Beizhang NW Chengzhou 29232 N, 12134.5E07ZLHT02 Longhuangtong Tiantai 291355.8 N, 12115606ZXJ05 Xiaojiang Xiaojiang 292346.1 N, 12162006ZXJ01 Xiaojiang Xiaojiang 292346.1 N, 12154507ZLL01 Lianglong Yuyoa 291322.4 N, 121459(Xiao and He, 2005; Li et al., 2010). Origin of this medium- to high-grade metamorphic complex is still controversial, but it likelyrepresents a relic of Mesoproterozoic to Neoproterozoic island arc(e.g. Cheng, 1993; Kong et al., 1994). Structural evidence suggests thatthe Chencai complex and its adjacent rock units weremetamorphosedand reworked in the late Paleozoic to early Triassic (Xiao and He,2005) and new age constraints on these metamorphic rocks suggestthat the complex experienced metamorphism and reworked in ca.460415 Ma after the Neoproterozoic rifting (Li et al., 2010).

Several other lines of evidence have also been used to support thatthe JSFZ is a suture zone. These include the occurrence of (1) potentialrelics (mac and ultramac rocks) of ophiolitic suite in the fault zone(Zhang et al., 1984), (2) different metal ore deposits in two sides ofthe JSFZ, i.e. gold, silver and lead deposits to the northwest of the JSFZand copper and molybdenum to the southeast and these differenceshave been attributed to the fundamental differences in the nature ofthe underlying basements (BGMRZP, 1989; Zhou and Zhu, 1993).Furthermore, some magmatism, as exemplied by the ca. 0.91 GaTaohong tonalite and Xiqiu granodiorite plutons (Ye et al., 2007) andthe ca. 0.970.89 Ga Shuangxiwu Group volcanic rocks and associatedtonalites and granodiorites (Li et al., 2009), proximal to the fault zonehas been interpreted to result from a convergent tectonic environ-ment, which probably indicate the commencement of the suturing.Geophysical data conrm a change in seismic proles along the faultzone (Hu, 2001; Zhang et al., 2005), but the nature of the fault zoneremains ambiguous because geophysical data can be interpreted indifferent ways. Therefore it is still a matter of debate whether the JSFZis a surface structure representing lateral movement or is a suturezone marking the collision between the two continent blocks. Analternative fault system, the JiangshanXiangshan Fault Zone (JXFZ),has also been proposed by others to represent the suture zonebetween the two blocks (e.g. Liu et al., 2003), based on that themantledomains beneath the two sides of the JXFZ may be different, aconclusion drawn from Pb isotopic data of Neoproterozoic andPhanerozoic basaltic rocks (Zhu et al., 1993). Therefore, furtherstudies are necessary for understanding the characteristics of the twodifferent continental blocks, the suture position and the amalgam-ation history of the SCC.

2.2. Sampling and local geology

A total of 29 igneous rocks were collected from 12 plutons ineastern Zhejiang Province, across the JSFZ. Our published data for anadditional pluton, a 126 Ma porphyritic granite in Baijuhuajian (Wonget al., 2009) near the JSFZ, are discussed with samples of this study.Sample localities and previous age data reported by others aresummarized in Table 1.

Fault Zone in Zhejiang Province.

Rock type Ages (Ma) from literature(with dating method)

Porphyritic granite 125.6 (zircon UPb) Wong et al., 2009K-feldspar granite nil nilGranodiorite 161176 (whole rock RbSr) BGMRZP, 1989Monzonite 135 (zircon UPb) Grifn et al., 2002Granite nil nil

E Porphyry nil nilE Rhyolite nil nil

Quartz syenitic porphyry 124 (Biotite ArAr) Chen et al., 1991bMonzogranite 98.5 (Biotite KAr) BGMRZP, 1989K-feldspar granite 110 (Biotite ArAr) Chen et al., 1991bK-feldspar granite 79.9 (KrAr) BGMRZP, 1989Quartz diorite nil nilQuartz diorite 101 (Biotite ArAr) Chen et al., 1991bAmong the 29 analysed samples, 10 samples were collected fromve plutons and one associated rhyolite in the area to the northwest ofthe JSFZ (NW domain) (Fig. 1b). The other 19 samples were collectedfrom ve plutons to the southeast of the fault (SE domain). Most of theselected plutons intruded Proterozoic sedimentary strata or MiddleJurassic to Early Cretaceous volcanic rocks (BGMRZP, 1989), and aregenerally fresh and coarse- to medium-grained. Their mineralogyincludes K-feldspar, plagioclase, quartz, biotite, with lesser amountsof muscovite, hornblende and opaque phases.

2.2.1. NW domainSampleswere collected along awesteast traverse in an area to the

west of the fault zone. Sample 06ZFR- and 07ZFR- series were from theBaijuhuajian porphyritic granite, which has been recognized recentlyas a 126 Ma A-type granite (Wong et al., 2009). Sample 07ZSQ- serieswere collected from a K-feldspar granite in Shuangqiao (Fig. 1b),which is located in the northeast of the Baijuhuajian porphyriticgranite in Furong County. These two plutons intruded a volcanic basinlled by the Upper Jurassic Suichang Formation, composed of

247J. Wong et al. / Gondwana Research 19 (2011) 244259porphyritic rhyolite, silicic tuff and ignimbrites (BGMRZP, 1989).Samples 06ZHC01 and 06ZZS01 were collected from Eshan granodi-orite and Zhangshan monzonite intrusions in Tongli County, respec-tively. These two intrusions are components of a large batholithknown as the Hengcunfu pluton (BGMRZP, 1989). The Eshangranodiorite crops out in the central part of the batholith, whereasthe Zhangshan monzonite is exposed along the western margin of thebatholith. Further to the east, sample 06ZFC01 was collected from agranite in Fungcun as part of the Huajiatang pluton. A granite sample06ZMJ02 and a rhyolitic sample 06ZMJ05 were collected from thetown of Majian. The Majian granite contains ne- to medium-grainedquartz and K-feldspar and was covered by the columnar-jointedrhyolite which belongs to the Huangjian Formation. The aforemen-tioned intrusive rocks intruded the Early Cretaceous (using thegeological timescale of Ogg et al., 2008) Huangjian Formation(assigned as Upper Jurassic in BGMRZP, 1989) that consists ofintermediate to acidic volcanic rocks.

2.2.2. SE domainSamples from 6 plutons were collected from an area to the

southeast of the JSFZ. In the western part, samples 06ZHG01 and06ZHG02 were collected from a large K-feldspar granite plutonknown as the Honggong pluton in Jiangshan County. This pluton cropsout in an area of 487 km2. In the eastern part, sample 06ZBZ01 wascollected from the Beizhang monzogranite. Samples 07ZLHT- serieswere collected from a road which cuts across the Longhuangtong K-feldspar granite pluton. Samples 06ZXJ01 and 06ZXJ05 have composi-tions of quartz diorite and K-feldspar granite, respectively, collectedfrom the Xiaojiang pluton. Samples 07ZLL- series were collected fromthe Lianglong quartz diorite. All these plutonic rocks intruded theEarly Cretaceous Moshishan volcanic sequence that consists of macto acidic volcanic rocks (BGMRZP, 1989). The Honggong granite,Lianglong quartz diorite, and Longhuangtong K-feldspar granite havebeen dated at ca. 124 Ma, 101 Ma and 110 Ma by Ar-Ar geochronol-ogy, respectively (Chen et al., 1991b). The Beizhangmonzogranite andXiaojiang K-feldspar granite have been reported with KAr ages at ca.98.5 Ma and 79.9 Ma, respectively (BGMRZP, 1989).

3. Analytical methods

3.1. Whole-rock major and trace elemental analysis

All the samples were crushed for whole-rock geochemical analysesin the Department of Earth Sciences at the University of Hong Kong.Major oxide concentrations were determined by wavelength-disper-sive X-ray uorescence spectrometry (XRF) on fused glass beads usinga Philips PW 2400 spectrometer with matrix correction followingNorrish and Hutton (1969). Trace element compositions wereanalyzed by inductively-coupled plasma mass spectrometry (ICP-MS) of nebulized solutions using a VG Plasma-Quad Excell ICP-MSfollowing the analytical procedures described by Qi et al. (2000).Standard reference materials used for both major and trace elementalanalyses were BHVO-2 (basalt), JGB-2 (gabbro), G2 and G3 (granites),and a Chinese national rock standard GSR-1 (granite). The results areshown in Supplementary Table 2. The precisions for the major andtrace elemental analyses are better than 5% and 10% respectively.

3.2. Zircon UPb geochronology

Zircons were separated by heavy-liquid and magnetic methodsand up to 100 selected grains were handpicked under a binocularmicroscope. The selected grains were thenmounted on adhesive tape,enclosed in epoxy resin, and polished to about half their thickness.Transmitted and reected light images of the grains were photo-graphed, and cathodoluminescence (CL) images of the zircons were

taken using a Mono CL3 detector (manufactured by Gatan, U.S.A.)attached to an ElectronMicroprobe (manufactured by JXA-8100, JEOL,Japan) at the Guangzhou Institute of Geochemistry, Chinese Academyof Sciences, in order to examine the structure and morphology of thezircons.

For the two samples with small size of zircon grains, i.e. samples07ZSQ01 and 06ZZS01, age results were obtained using the WAconsortium SHRIMP II ion microprobe housed at the Curtin Universityof Technology, Perth, Australia. The instrumental performance andanalytical procedures have been described by Nelson (1997). Samplemounts were cleaned and gold-coated before measurements. Frag-ments of the Sri Lankan gem zircon standard CZ3 (Pidgeon et al.,1994) were incorporated in the mount as reference to monitor theisotopic ratios, using 206Pb/238U ratio of 0.09143 equivalent to an ageof 564 Ma, and were repeatedly analyzed after every three or fourunknown analyses. The measured 204Pb is considered to be originatedfrom the gold coating and assumed to have the same isotopiccomposition of Broken Hill common Pb (204Pb/206Pb=0.0625, 207Pb/206Pb=0.9618, 208Pb/206Pb=2.2285) (Cumming and Richards,1975), which was used for common Pb correction. The U and Thdecay constants recommended by Steiger and Jger (1977) were usedto calculate the ages of the samples. Pb/U ratios of the unknownsamples were corrected using the ln(Pb/U)/ln(UO/U) relationship asmeasured in the standard CZ3. The analytical data were then reduced,calculated and plotted using the Squid 1.0 (Ludwig, 2001) andIsoplotEx 3.0 programs (Ludwig, 2003). The error assessment forSHRIMP analyseswas described in details by Stern and Amelin (2003).Detailed analytical data are shown in Supplementary Table 3 with 1error and uncertainties in weighted mean ages are quoted at the 95%condence level (2).

For other samples, the UPb isotope compositions of zircons wereanalyzed using LA-ICPMS at the University of Hong Kong and theInstitute of Geology and Geophysics, the Chinese Academy of Sciences(IGGCAS), Beijing. Data for ve samples were obtained using a VGPlasmaQuad Excel inductively coupled plasma-mass spectrometer(ICP-MS) equipped with a Nd:YAG 213 laser ablation system(Microprobe2, NewWave Research, USA) installed in the Departmentof Earth Sciences, the University of Hong Kong. The laser systemprovides a beam of 213 nm UV light from a frequency-quintupled Nd:YAG laser. A beam diameter of ca. 40 m, with repetition rate of 10 Hzand energy of 0.61.3 mJ per pulse were used for most of the analyses.The instrument was tuned with total U signals ranging from 3104 to100104 counts, depending on U contents. Typical ablation cycle wasabout 2 min for each analysis, including 3060 s of ablation time and50 s of measurement of instrumental background, resulting in pits2040 m deep. The ablated sample materials were transported byhelium carrier gas from the laser-ablation cell via amixing chamber tothe ICPMS after mixing with Ar gas. Detailed instrumental settingsand analytical procedures were described by Xia et al. (2004). Zirconstandards 91500 (Wiedenbeck et al., 1995) and CN92 (Feng et al.,1993; Xia et al., 2004) were analyzed with the unknowns as anindependent control on reproducibility and instrument stability.

UPb age data for four more samples were determined by anAgilgent 7500a quadruple (Q)-ICPMS attached with a Geolas laser-ablation system equipped with a 193 nm Ar-F-excimer laser inIGGCAS, Beijing. Details of experimental conditions and data collec-tion can be referred to Wu et al. (2006) and Xie et al. (2008). Ablationwas performed in a He carrier gas to increase the transport efciencyof the ablationmaterial. Then the He carrier gas inside the ablation cellwas combined with Ar gas in mixing chamber before entering the ICPto keep the excitation in stable and optimum conditions. Gas lineswere all purged for over 1 h before each analytical session to makesure that 204Pb is less than 50 cps in the gas blank. The measurementswere performed using time resolvedmode and the dwell time was setat 6 ms for Si, Ti, Nb, Ta, Zr and REE, 15 ms for 204Pb, 206Pb, 207Pb and208Pb and 10 ms for 232Th and 238U. Raw counts rates were collected

for age determination. Time for background and data acquisition for

02) from SE Domain are categorized into syenite although one of themis marginal between syenite and diorite. Other samples are granites orrhyolite (Majian 06ZMJ05 from the NW domain) showing variablemajor oxides contents with SiO2 from 68.0 to 77.7 wt.%, moderate tohigh Al2O3 and K2O from 11.5 to 15.1 wt.% and 0.96 to 2.01 wt.%respectively. They contain normative quartz from 14 to 42 wt.%. Mostof them have moderate ACNK values ranging from 0.97 to 1.06 andpossess normative corundum from 0 to 0.79 wt.%, showing ametaluminous afnity. The Baijuhuajian granite (06ZFR and 07ZFRseries) is an A-type granite (Wong et al., 2009), in contrast to mostother granites in this study that show I-type signatures. TheJiuhuashan granite (07ZSQ series) contains relative high ACNK valuesfrom 0.93 to 1.22 and possesses normative corundum from 0 to 3.21%.These features are similar to S-type granites. However, absence ofmuscovite and biotite indicates that the Jiuhuashan granite is differentfrom typical S-type granite (Wong, 2007). Moreover, P2O5 contents ofthis granite decrease with an increase of SiO2 contents, and Y and Th

rhyolitic sample (06ZMJ05), to the northwest of the JSFZ, are mostly

248 J. Wong et al. / Gondwana Research 19 (2011) 244259each spot analysis is ca. 20 s and 60 s, respectively. Low 202Hg isdetected in the gas blank, which is negligible in the data process. 29Siand NIST SRM 610 were used as internal standard and externalstandard, respectively, for calibration of U, Th and Pb concentrations.

Data reduction, isotope ratios and apparent age calculations forresults obtained by LA-ICPMS were carried out with the GLITTER 4.0software (van Achterbergh et al., 2001). Zircon standard 91500 andIsoplotEx 3 software (Ludwig, 2003) were used for data calculation.UPb ages of zircons were calculated using the U decay constants of238U=1.551251010 year1 and 235U=9.84541010 year1

(Steiger and Jger, 1977). Individual analyses are presented with 1error and in the concordia diagrams, and uncertainties in age resultsare quoted at 95% level (2).

3.3. Zircon LuHf isotopic compositions

The Neptune MC-ICPMS in IGGCAS was employed for Hf isotopicmeasurements. Detailed analytical procedures were described by Xu,P. et al. (2004) and Wu et al. (2006). Hf isotopic data reported in thisstudy were obtained from the zircon grains with UPb data, oncondition of beam diameter of 32 m, pulse rates of 8 Hz and energydensity of 15 J/cm2. Each analytical spot was subject to 200 ablationcycles. Atomic masses 172, 173, 175 to 180 and 182 weresimultaneously measured in static-collection mode. The obtained176Hf/177Hf ratios were normalized to the 179Hf/177Hf value of 0.7325(Patchett et al., 1982), using an exponential correction law for massbias (Russel et al., 1978). Isobaric interference of 176Yb on 176Hf wascorrected against the 176Yb/172Yb ratio of 0.5886 (Chu et al., 2002) andYb/Hf at 0.8725 (Xu et al., 2004). Interference of 176Lu on 176Hf wascorrected by measuring the intensity of the interference-free 175Luisotope and using a recommended 176Lu/175Lu ratio of 0.02655 (Chu etal., 2002). External calibration was made by measuring zirconstandard 91500 with the unknowns during the analyses to evaluatethe reliability of the analytical data, which yielded a weighted mean176Hf/177Hf ratio of 0.2823080.000025. This value is in goodconsistency with the recommended value of 0.282305 (Wu et al.,2006).

Initial 176Hf/177Hf ratios were calculated using themeasured 176Lu/177Hf ratios and the 176Lu decay constant of 1.8651011 yr1

reported by Scherer et al. (2001). Hf(t) values were calculatedusing the chondritic 176Hf/177Hf values of 0.282772 and 176Lu/177Hf of0.0332 reported by Blichert-Toft and Albrede (1997). Assuming thatthe depleted mantle reservoir has a linear growth from 176Hf/177Hf=0.279718 at 4.55 Ga to 0.283250 at present, with 176Lu/177Hfvalue of 0.0384 (Grifn et al., 2004), the depleted mantle Hf modelages (TDM) were calculated using the measured 176Lu/177Hf ratios ofzircon. The mantle extraction model age (TDM2) was calculated byprojecting initial 176Hf/177Hf ratios of the zircon to the depletedmantlemodel growth line using 176Lu/177Hf value (0.015) for averagecontinental crust (Grifn et al., 2002). The discussion in this study isbased on TDM2. Hf isotope results are reported with 2 error.

4. Results

4.1. Geochemistry

Major- and trace-element compositions of samples in this studyare presented in Supplementary Table 2. The QAP diagram dividesthese samples into three major rock types: diorite, granodiorite andgranite (Fig. 2). The diorites, including samples from Zhongshan(06ZZS01) of the NW domain, Xiaojiang (06ZXJ01) and Lianglong(07ZLL series) of the SE domain, show varying SiO2 contents from 56.2to 62.1 wt.% and have higher TiO2, Al2O3, MgO, CaO, P2O5, Cr and Vthan other samples. The Eshan sample (06ZHC01) fromNWDomain isclassied as granodiorite and contains 65.3 wt.% of SiO2 and its TiO2

content is lower than the diorites. The Honggong samples (06ZHG01,euhedral, prismatic, transparent and colourless, ranging from 70 to220 m in length and having width-to-length ratios of 1:1 to 1:3.Grain sizes of zircons from the monzonite sample 06ZZS01 and thegranodiorite 06ZHC01 are relatively small, ranging from 80 to 120 min length, with width-to-length ratios of 1:1 to 1:4. These zircons areeuhedral to subhedral, transparent and colourless, mainly prismatic.In CL images, zircon crystals from all samples exhibit well developedconcentric zoning and no inherited cores were observed, excludingthe zircons from the granodiorite 06ZHC01 (Fig. 4). All the zirconsfrom different samples show different Th and U concentrations,ranging from 14 to 623 ppm and 9 to 775 ppm, respectively, and their

Fig. 2. Modal QAPF classication diagram for the igneous rocks around the JSFZ (afterdecrease with increasing Rb, which represent a typical I-type graniteevolution trend and hence the granite is also considered to be an I-type granite (Wong, 2007). The diorites have relatively low REEcontents and show LREE enriched patterns with weak negative Euanomaly (Fig. 3), whereas the granites have at REE patterns withvariable LREE abundances and pronounced Eu negative anomalies(Fig. 3), implying fractionation of feldspar. The Baijuhuajian (06ZFRand 07ZFR series) (Wong et al., 2009) and Longhuangtang graniticsamples (07ZLHT series) with SiO2 more than 74.1 wt.% show strongnegative Eu anomaly, implying an important role of feldsparfractionation.

4.2. Zircon UPb age results

4.2.1. Samples from the NW domainAll the UPb age results are presented in Supplementary Table 3

and are shown on the concordia diagrams (Fig. 5a and b). Zircons fromgranitoid samples (07ZSQ01, 06ZFC01 and 06ZMJ02) and oneStreckeisen and Le Maitre, 1979).

249J. Wong et al. / Gondwana Research 19 (2011) 244259Th/U ratios are all greater than unity (0.371.25), indicating amagmatic origin.

4.2.1.1. Sample 07ZSQ01. A total of 12 zircons from the Shuangqiao K-feldspar granite sample (07ZSQ01) were analyzed by SHRIMP and8 zircons from the same sample were analyzed by LA-ICPMS. For thedata measured by SHRIMP, all analyses are nearly concordant andcluster as a single population with a weighted mean 206Pb/238U age of132.42.5 Ma (MSWD=0.6). The results yielded by LA-ICPMS alsoshow similar concordant 206Pb/238U age (1385 Ma) and one old corewith 978.539 Ma was found.

4.2.1.2. Sample 06ZHC01. For the Eshan granodiorite sample 06ZHC01,13 analyses were conducted using LA-ICPMS. Among the 13 zirconanalyses, two cores are signicantly older and nearly concordant, with206Pb/238U ages of 7839 and 8249Ma, respectively. Since thecountry sedimentary rocks were deposited in the early Paleozoic toTriassic, and zircons from the enclaves in Tonglu complex also givesimilar TDM ages (0.750.8 Ga and 0.85 Ga, respectively; Grifn et al.,2002), these old cores are possibly inherited from the magma source.

Fig. 3. Chondrite-normalized REE diagram for the sampled igneous rocks from (a to c) theMcDonough (1989).The other eleven analyses yielded a single population mean 206Pb/238Uage of 134.81.4 Ma (MSWD=1.2), which may represent thecrystallization age of the pluton (Fig. 5a).

4.2.1.3. Sample 06ZZS01. The Zhongshan monzonite sample 06ZZS01was collected from the same pluton as with the Eshan granodioritesample 06ZHC01, and 15 zircons were analyzed by SHRIMP. Allanalyses are concordant and cluster as a single population with aweighted mean 206Pb/238U age of 130.12.2 Ma (MSWD=0.17),representing the crystallization age of the pluton (Fig. 5a).

4.2.1.4. Sample 06ZFC01. A total of 29 zircons from the Fungcun granitesample 06ZFC01 were analyzed using LA-ICPMS. All analyses areconcordant and cluster as a single population to provide a weightedmean 206Pb/238U age of 121.21.7 Ma (MSWD=0.75) and this isconsidered to record the emplacement age of the pluton (Fig. 5a).

4.2.1.5. Sample 06ZMJ02 and 06ZMJ05. Ten zircons from the Majiangranitic sample (06ZMJ05) were analyzed using LA-ICPMS. Theanalyses are nearly concordant and give a single population with a

NW domain and from (d to f) the SE domain. Normalization values are from Sun and

250 J. Wong et al. / Gondwana Research 19 (2011) 244259weighted mean 206Pb/238U age of 129.71.1 Ma (MSWD=1.1),which represents the crystallization age of the rock body (Fig. 5a).Refer to the associated rhyolite, twenty-four zircons from the Majianrhyolite sample (06ZMJ05) were analyzed using LA-ICPMS. Theanalyses are nearly concordant and give a single population withweighted mean 206Pb/238U age of 132.21.7 Ma (MSWD=3), whichrepresents the crystallization age of the rock body (Fig. 5a). This ageoverlaps within error with that for the granite from the same locality.

4.2.2. Samples from the SE domainZircons from the granitoid samples (06ZHG01, 06ZBZ01,

07ZLHT02 and 06ZXJ05) from areas southeast to the JSFZ are mostlyeuhedral, prismatic, transparent and colourless, ranging from 70 to220 m in length and having width-to-length ratios of 1:1 to 1:3. Inthe CL images (Fig. 4), zircon grains from all granitoid samples showtypical magmatic zoning without inherited cores. Zircons from twoquartz diorite sample, which are the Xiaojiang sample 06ZXJ01 andthe Lianglong sample 07ZLL01 are euhedral to subhedral, prismatic orelongated, ranging from 50 to 200 m in length, with width-to-length

Fig. 4. CL images of representative zircon grains from studied igneous rocks along the Jiangsample.ratios of 1:2 to 1:3. The grains are transparent, colourless and displayweak concentric zoning without inherited cores (Fig. 4). All thezircons have Th concentrations from 17 to 864 ppm and U from 12 to1210 ppm, leading to a wide range of Th/U ratios from 0.2 to 2.66(Supplementary Table 3), indicating a magmatic origin.

4.2.2.1. Sample 06ZBZ01. Eighteen zircon grains from the Beizhangmonzogranite sample 06ZBZ01 were analyzed using LA-ICPMS. Theanalyses are nearly concordant and give a population with a weightedmean 206Pb/238U age of 119.93.1 Ma (MSWD=13), which isinterpreted to be the crystallization age of the pluton (Fig. 5b).

4.2.2.2. Sample 07ZLHT02. It is a K-feldspar granite collected from theinterior part of the Longhuangtong pluton. A total of 13 zircons fromthis sample were analyzed by the LA-ICPMS. The data are nearlyconcordant and give a single age population with a weighted mean206Pb/238U age of 114.63.8 Ma (MSWD=3.3) (Fig. 5b).

shan-Shaoxing Fault Zone. * Age represents the weighted mean 206Pb/238U age of the

4.2.2.3. Sample 06ZXJ01. For the quartz diorite sample 06ZXJ01 whichintruded into the K-feldspar granite 06ZXJ05, 25 zircons were analyzedusing LA-ICPMS. The analyses are discordant. Nevertheless, the 206Pb/

238U ratios are quite consistent (0.01713 to 0.01869) and give aweighted mean 206Pb/238U age of 114.31.2 Ma (MSWD=3.3). Theage thus may indicate the crystallization age of the pluton (Fig. 5b).

rock

251J. Wong et al. / Gondwana Research 19 (2011) 244259Fig. 5. Concordia diagrams of zircon and histograms of Hf(t) values from studied igneous206 238the mean values of each sample are Pb/ U ages in Ma.s from (a) the NWdomain (Yangtze Block) and (b) the SE domain (Cathaysia Block). All

Fig. 5 (continued).

252 J. Wong et al. / Gondwana Research 19 (2011) 244259

4.2.2.4. Sample 07ZLL01. Twenty-nine zircons from the Lianglongquartz diorite 07ZLL01 were analyzed by LA-ICPMS. The analyses arenearly concordant and give a single population with a weighted mean206Pb/238U age of 100.11.7 Ma (MSWD=0.78), which representsthe crystallization age of the pluton (Fig. 5b).

4.2.2.5. Sample 06ZHG01 and 06ZXJ05. In this study, zircons from theHonggong K-feldspar granitic sample 06ZHG01 and the Xiaojiang K-feldspar granite sample 06ZXJ05 were analyzed by the LA-ICPMS atHKU. Because the 207Pb/235U ratios are varied in a large range, the Ar

Ar age of ca. 124 Ma reported for the Honggong granite (Chen et al.,1991b) and the KAr age of ca. 79.9 Ma reported for the Xiaojiang K-feldspar (BGMRZP, 1989) are employed to calculate the epsilon Hfvalues and model ages.

In summary, all zircons from the plutonic bodies of this study havehighly variable Th and U, but their Th/U ratios are all higher than 0.1,supporting amagmatic origin. Combinedwith the previously reportedages for the Honggong (124 Ma) and Xiaojiang granites (79.9 Ma)(BGMRZP, 1989; Chen et al., 1991b), our results indicate that theigneous rocks from the SE side of the JSFZ were emplaced between

gtz

253J. Wong et al. / Gondwana Research 19 (2011) 244259Fig. 6.Histogramsof Hf(t) valuesof eachstudied igneous rock from(a) theNWdomain(Yan

domain (Cathaysia Block).eBlock), including theBaijuhuajianporphyritic granitebyWonget al. (2009)and (b) theSE

pattern also appears on the histogram of TDM2 ages at ca. 876 and1170 Ma (Fig. 7).

4.3.2. Samples from the SE domainA total of 158 spot analyses of zircon grains from six plutons in the

SE domain were conducted for Hf isotopic analysis and results arepresented in the histograms of Hf(t) (Fig. 6b).

4.3.2.1. Sample 06ZHG01. Twenty-four zircons from the Honggong K-feldspar granitic sample 06ZHG01 yield Hf(t) values from 8.8 to0.8 with one exception of 12.9. The TDM2 ages of these zirconsvary from 1008 to 1618 Ma.

4.3.2.2. Sample 06ZBZ01. Similarly, twenty-one zircon grains from theBeizhang monzogranite sample 06ZBZ01 give Hf(t) values from6.2to 1.9 with three exceptions of 12.4, 9.9 and 9.3. The TDM2ages of these zircons vary from 1062 to 1589 Ma.

254 J. Wong et al. / Gondwana Research 19 (2011) 244259124 and 79.9 Ma, whereas those from the NW side of the fault wereemplaced, from 135 to 121 Ma. Inherited cores are absent for samplesfrom the SE side of the fault but are rarely observed for samples fromthe NW side of the fault.

4.3. Hf isotope compositions

Most of the Lu-Hf isotope analyses were performed on spot withinthe same internal structure domains that were analyzed for U/Pbisotopic compositions. In addition, some small zircons without UPbdata were also analyzed for LuHf isotope composition. Their initial Hfisotopic ratios were calculated using the weighted mean 206Pb/238Uages of the pluton obtained from zircons of the same sample. The LuHf isotopic data for all zircon grains are listed in SupplementaryTable 4 and graphically presented on Fig. 6a and b. The total analysesfor each sample, the values of the initial Hf isotopic ratios and modelages are also summarized in Supplementary Table 4.

4.3.1. Samples from the NW domain

4.3.1.1. Sample 07ZSQ01. A total of 146 zircon grains from sixrepresentative samples in the NW domain were analyzed. TheShuangqiao K-feldspar granite sample 07ZSQ01 give negative initialHf(t) values (7 to1.2) and TDM2 age from 1037 to 1330 Ma. Onezircon core of this sample gives 206Pb/238U age of 979 Ma and yieldspositive initial Hf(t) values of +1 and TDM2 age of 1624 Ma.

4.3.1.2. Sample 06ZHC01. For the Eshan granodiorite sample 06ZHC01,the two old cores with 206Pb/238U ages of 7839 and 8249 Ma aretoo small for Hf isotope analysis after the UPb age analysis. A total of21 zircons without core-rim structure were analyzed for Hf isotopes,yielding Hf(t) value from 6.9 to 0.5 with one positive value of+2.1. Their TDM2 ages range from 1003 to 1328 Ma, with one of869 Ma.

4.3.1.3. Sample 06ZZS01. Sixteen zircon grains of the Zhangshanmonzonite sample 06ZZS01were analyzed and gave 176Hf/177Hf ratiossimilar to the granodiorite sample 06ZHC01, and their Hf(t) valuesvary from6.2 to0.3 with one exception of +0.7. Crustal Hf modelages for the zircons of this sample are from 987 to 1287 Ma with oneexception of 941 Ma.

4.3.1.4. Sample 06ZFC01. Thirty-two zircons from the Fungcun granitesample 06ZFC01 were analyzed and their Hf(t) values and TDM2 agesrange from 4.9 to +5.7 and from 678 to 1212 Ma, respectively.

4.3.1.5. Sample 06ZMJ02 and 06ZMJ05. Twenty-four zircon grains ofthe Majian granite sample 06ZMJ02 show varied Hf(t) values from4.0 to +6.8 with one exception of +9.1. The TDM2 ages of thesezircons range from 509 to 1174. The Majian rhyolite sample(06ZMJ05) also shows a wide range of zircon Hf isotope compositions,giving Hf(t) values from1.5 to+6.9 with one of 12.4. The TDM2 agesof the zircons range from 344 to 1050 Ma.

In summary, the Shuangqiao K-feldspar granite sample 07ZSQ01give negative zircon Hf(t) values, ranging from 7 to 1.2. Zirconsfrom this sample also yield older TDM2 ages from 1037 to 1330 Ma. Incontrast, zircons from other samples of the NW domain show a widerange of Hf(t) values from negative to positive values, ranging from7 to +6.9, with two outliers of +9.1 and +12.4 from the twoMajian samples, and their TDM2 ages are from 872 to 1193 Ma. Thedominant Neoproterozoic TDM2 ages may suggest that the magmasource was predominated by Neoproterozoic materials. All analyzedzircons from the NW domain show a relatively wide range on thehistograms of both Hf(t) values and TDM2 ages (Figs. 6a and 7a). Two

peaks of Hf(t) values appear at ca.4.5 and+1 (Fig. 7) and two-peak4.3.2.3. Sample 07ZLHT02. A total of 34 zircons from the sample07ZLHT02 were analyzed and their Hf(t) values vary from 6.9 to2.3 and one exception of 11.5. The TDM2 ages of these zirconsrange from 1076 to 1539 Ma.

4.3.2.4. Sample 06ZXJ05. Twenty-four zircon grains from the XiaojiangK-feldspar granite sample 06ZXJ05 were analyzed and also giverelatively narrow Hf(t) values from 5.7 to 0.5 with one positivevalue of +4.5. These zircons show TDM2 ages from 982 to 1213 Ma,except for the two zircons with positive Hf(t) values and TDM2 ages of949 and 693 Ma.

4.3.2.5. Sample 06ZXJ01. Twenty-two zircons were analyzed for thequartz diorite sample 06ZXJ01. Their Hf(t) values are mainly negativefrom7.1 to0.2, with two positive values of +0.7 and+1.9. Thesezircons show TDM2 ages from 944 to 1278 Ma, excluding the two agesof 840 and 899 Ma.

4.3.2.6. Sample 07ZLL01. Thirty-three zircons from the Lianglongquartz diorite 07ZLL01were analyzed for Hf isotope compositions andall give negative Hf(t) values from 6.5 to 2.2. The TDM2 ages ofthese zircons range from 1070 to 1288 Ma.

In summary, the zircons from the SE domain yielded Hf(t) valuesmostly less than zero, from 0.1 to 9.9, with outliers of 11.5,12.4 and12.9. Three positive Hf(t) values are obtained, but theyare mostly near zero. The TDM2 ages of all zircons range from 702 to1618 Ma. Overall, our data from the SE domain show single peak onFig. 6 (continued).

255J. Wong et al. / Gondwana Research 19 (2011) 244259the Hf(t) and TDM2 histograms, i.e. around 4 and ca. 1126 Ma,respectively (Fig. 7).

5. Discussion

5.1. Nature of the lower crust underneath the SE and NW domains

Acidic magmas are generally formed as a result of partial meltingof the lower crust, thus their chemical and isotopic compositions canbe used to trace the nature of their magma sources in the lower crust.Because zircons contain very high Hf content and extremely low Lu(176Lu decays to 176Hf), and they are very resistant to secondary

Fig. 6 (contprocesses such as alteration or weathering after they crystallized inthe magma, zircon Hf isotopic compositions can provide insightfulinformation for their parental magma. Acidic rocks from the SEdomain all give consistent zircon Hf(t) values, with a peak value ataround 4 (Figs. 6b and 7), implying that the precursor magmascame from a similar ancient source. Because almost all these zirconsgive Meso- to Neoproterozoic crustal model ages (1618 to 840 Ma,excluding one of 702 Ma), with a peak at ca. 1126 Ma (Fig. 7), weinterpret that the lower crust of the SE domain is relatively uniform,comprising predominately of Mesoproterozoic materials.

In contrast, the acidic rocks from the NW domain have variablezircon Hf isotopic compositions, implying that the magmas possibly

inued).

256 J. Wong et al. / Gondwana Research 19 (2011) 244259came from a heterogeneous lower crust. Zircons with negative Hf(t)values dominate two granitic rocks (06ZSQ01 and 06ZHC01),suggesting a derivation from an ancient lower crust. The zircon Hfmodel ages of these two samples range from 1624 to 1037 Ma and1328 to 869 Ma, respectively, implying magma genesis related tomelting of Mesoproterozoic materials in the lower crust.

On the other hand, zircons from the other samples of the NWdomain, including the previously reported Baijuhuajian granite(Wong et al., 2009), are dominated by positive Hf(t) values, in accordwith the interpretation that their parental magmaswere derived frommore juvenile materials. These source materials were isotopicallymore enriched than the depletedmantle given that the Hf(t) values ofthe NW domain are lower than the depleted mantle evolution curve(ca. +16 in Late Cretaceous; Figs. 6a and 7). The calculated zircon Hfmodel ages peak at ca. 876 and 1170 Ma, possibly implying thatextraction of melt from the mantle and input into the lower crust inthe Meso- and Neoproterozoic. This interpretation is supported by thefact that Neoproterozoic inherited zircons (824.49.4 and 783.49.1 Ma) are found in sample 06ZHC01 from this domain (Supple-lementary Table 3).

To summarize, the pool of all the Hf data for the NWdomain showstwo Hf(t) peaks at 4.5 and +1 and two Hf model age peaks at ca.876 and 1170 Ma, demonstrating that Meso- and Neoproterozoicmaterials are important components within the lower crust of the NWdomain.

5.2. The signicance of Neoproterozoic igneous activity

Our study identies two Hf model age peaks (ca. 876 and 1170Ma)for the NW domain and one (ca. 1126 Ma) for the SE domain,

Fig. 7. Histograms of Hf(t) and TDM2 values of the studied igneous rocks along the JiangshanWong et al. (2009) are plotted with the samples from the NW domain.respectively. These ndings are consistent with the occurrences ofNeoproterozoic magmatism in the Yangtze and Cathaysia blocks.Detailed geological and geochronological studies indicate that Neopro-terozoic rocks are distributed mainly in two regions on the YangtzeBlock, i.e. the PanxiHannan region along the western and northernmargin of the Yangtze Block (Zhou et al., 2006) and the Jiangnanorogenic belt between the Yangtze and Cathaysia blocks (Fig. 1a). Theformer includes the ca. 825820 Ma granitoids in Bendong, Sanfang andYuanbaoshan in northern Guangxi (Li, 1999), the ca. 820 Ma Eshan K-feldspar porphyritic granite in Central Yunnan (Li et al., 1999), the ca.768751 Ma TTG and 825795 Ma intrusive rocks along the KangdianRift and in Panzhihua region in western Sichuan (Zhou et al., 2002; Liet al., 2003).

The latter region, the Jiangnan orogenic belt, also known as theJiangnan Oldland and Jiangnan Fold Belt, is a ca. 1500 km long NEE-trending belt along the southeastern margin of the Yangtze Block andbounded by the northeasternmargin of the Cathaysia Block (Guo et al.,1980; Chen et al., 1991a; Xu and Zhou, 1992; Zhou and Zhu, 1993; Shuand Charvet, 1996; Wang et al., 2004). The orogen belt consists ofvoluminous Proterozoic volcanic and sedimentary rocks, whichunderwent regional metamorphism, and is unconformably overlainby sedimentary rocks of Sinian age (latest Proterozoic) (Shu andCharvet, 1996). Neoproterozoicmagmatism has been identied in thisbelt along the southeasternmargin of the Yangtze Block. Examples arethe ca. 1.0 Ga Zhangshudun ultramac complex (Chen et al., 1991a),the ca. 0.97 Ga Xiwan adakitic granite (Li and Li, 2003), the ca. 0.880.80 Ga Shuangqiaoshan volcanic rocks (Wang et al., 2008) and the ca.0.83 Ga Guangfeng bimodal volcanic rocks (Li et al., 2008) innortheastern Jiangxi, the ca. 0.83 and ca. 0.78 Ga volcanic and graniticrocks in the Shi'ershan area of southern Anhui and northern Zhejiang

Shaoxing Fault Zone. The Hf(t) and TDM2 values of Baijuhuajian porphyritic granite by

257J. Wong et al. / Gondwana Research 19 (2011) 244259(Zheng et al., 2008), the ca. 0.970.89 Ga Shuangxiwu volcanic arcsequences (Li et al., 2009) and the ca. 0.78 Ga Daolingshan A-typegranite (Wang et al., 2010) in the northern Zhejiang. In contrast, rareNeoproterozoic igneous rocks occur on the Cathaysia Block and arefound only at the northeasternmargin of this block, e.g. the ca. 0.82 GaMamianshan bimodal volcanic rocks in Fujian (Li et al., 2005) and the0.90.83 Ga Chencai complex in Zhejiang (Li et al., 2010). Our resultsindicate that the lower crusts of the NWand SE domains are consistentwith the exposed basement rocks of the Yangtze and Cathaysia blocks,and thus support the view that the JSFZ is possibly a suture betweenthe two continental blocks in South China.

5.3. Tectonic implications for the amalgamation of the Yangtze andCathaysia blocks

Debate exists on the tectonic evolutionary history of the South ChinaCraton. One of the hottest topics is when the Yangtze and Cathaysiablocks amalgamated, i.e. at ca. 1.1 Ga to0.9 Ga (e.g. Shui, 1988; ChenandJahn, 1998; Ye et al., 2007) or after ca. 0.9 Ga (e.g. Zhao and Cawood,1999; Zhou et al., 2002; Wang et al., 2004, 2006, 2008; Zheng et al.,2007). According to previously published detrital zircon age data for themetasedimentary rocks in South China (e.g. Grimmer et al., 2003; Xu etal., 2007; Yu et al., 2008), ca. 1.0 Ga old detrital zircons are common forsamples from both blocks. Assuming that the two continents wereunited at or earlier than ca. 1.0 Ga, the connected area is expected toshare any younger detrital zircon age record. However, variance of thedetrital zircon age data between the Yangtze and Cathaysia blocks afterca. 1.0 Ga has been found, indicating that the time of collision probablybe later (Wang et al., 2007a; Yu et al., 2008). Likewise, Zhao and Cawood(1999) interpreted that the peakmetamorphic age at 866 Ma (KAr ageof glaucophanes from blueschists in NE Jiangxi; Ma and Wang, 1994)was possibly related to the collision time. The UPb zircon ages of ca.825 Ma obtained from the S-type granite intruding the Sibao Group inwestern Jiangnan belt (Li et al., 1999) may record the timing ofexhumation of the metamorphosed terranes. Data of this study suggestthat Mesoproterozoic materials exist in the lower crust of both theYangtze and Cathaysia blocks, but those Neoproterozoic materials areimportant components for the Yangtze, not so for the Cathaysiabasement (Fig. 7). This means that either the magmatic activity in theNeoproterozoic did not extend to the Cathaysia Block, or alternativelythe twoblockswere separated, at least in thepresent northern region, inthe Neoproterozoic.

6. Conclusions

Zircon UPb ages and Hf isotopic compositions for a series ofMesozoic granitic rocks across the JSFZ show systematic differencesbetween the NW and SE domains of the fault zone. Acidic rocks in theNW domain have Hf(t) values ranging from7.0 to +6.9 and thesein the SE domain from12.9 to+1.9. The TDM2model ages in the NWdomain are 334 to 1330 Ma, with two peaks at ca. 876 and 1170 Marespectively, whereas those for the SE domain are 702 to 1618 Ma,with a single peak at ca. 1126 Ma. This Hf isotopic disparity indicates asignicant difference in the lower crust of the two domains. Our studysupports the idea that the JSFZ represents the suture zone betweenthe Yangtze and Cathaysia blocks. The Neoproterozoic magmaticactivity was important for the Yangtze Block, possibly due to theamalgamation and break-up of the Rodinia supercontinent. Similarmagmatism was less signicant for the Cathaysia Block, and this mayhave important tectonic implications for the amalgamation of theYangtze and Cathaysia blocks.

Acknowledgements

The authors appreciate the great efforts of Prof. M. Santosh, Dr.

Wenjiao Xiao, Dr. Jianbo Zhou and an anonymous reviewer for theirconstructive reviews to improve the quality of this paper. Weacknowledge Dr. George S.-K. Ma for the scientic discussion,Longming Li for eld work, Xiao Fu, Lily Chiu, Liang Qi, Liewen Xie,Yueheng Yang, Xiaoping Xia and Jiangfeng Gao for laboratoryassistance. This study was supported by research grants from theResearch Grant Council of Hong Kong (HKU 7041/05P), the ChineseMinistry of Land and Resources (200811015), the Chemical Geody-namics Joint Laboratory between HKU and Guangzhou Institute ofGeochemistry.

Appendix A. Supplementary data

Supplementary data associated with this article can be found, inthe online version, at doi:10.1016/j.gr.2010.06.004.

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Zircon UPb and Hf isotopic study of Mesozoic felsic rocks from eastern Zhejiang,South China: Geochemical contrast between the Yangtze and Cathaysia blocksIntroductionGeological backgroundRegional geologySampling and local geologyNW domainSE domain

Analytical methodsWhole-rock major and trace elemental analysisZircon UPb geochronologyZircon LuHf isotopic compositions

ResultsGeochemistryZircon UPb age resultsSamples from the NW domainSample 07ZSQ01Sample 06ZHC01Sample 06ZZS01Sample 06ZFC01Sample 06ZMJ02 and 06ZMJ05

Samples from the SE domainSample 06ZBZ01Sample 07ZLHT02Sample 06ZXJ01Sample 07ZLL01Sample 06ZHG01 and 06ZXJ05

Hf isotope compositionsSamples from the NW domainSample 07ZSQ01Sample 06ZHC01Sample 06ZZS01Sample 06ZFC01Sample 06ZMJ02 and 06ZMJ05

Samples from the SE domainSample 06ZHG01Sample 06ZBZ01Sample 07ZLHT02Sample 06ZXJ05Sample 06ZXJ01Sample 07ZLL01

DiscussionNature of the lower crust underneath the SE and NW domainsThe significance of Neoproterozoic igneous activityTectonic implications for the amalgamation of the Yangtze and Cathaysia blocks

ConclusionsAcknowledgementsSupplementary dataReferences