Full Terms & Conditions of access and use can be found athttp://www.tandfonline.com/action/journalInformation?journalCode=tigr20

Download by: [Universite de Lorraine] Date: 29 September 2015, At: 06:22

International Geology Review

ISSN: 0020-6814 (Print) 1938-2839 (Online) Journal homepage: http://www.tandfonline.com/loi/tigr20

Element mobility in mafic and felsic ultrahigh-pressure metamorphic rocks from the Dabie UHPOrogen, China: insights into supercritical liquids incontinental subduction zones

Jian Huang & Yilin Xiao

To cite this article: Jian Huang & Yilin Xiao (2015) Element mobility in mafic and felsic ultrahigh-pressure metamorphic rocks from the Dabie UHP Orogen, China: insights into supercriticalliquids in continental subduction zones, International Geology Review, 57:9-10, 1103-1129,DOI: 10.1080/00206814.2014.893213

To link to this article: http://dx.doi.org/10.1080/00206814.2014.893213

Published online: 28 Feb 2014.

Submit your article to this journal

Article views: 105

View related articles

View Crossmark data

Citing articles: 4 View citing articles

Element mobility in mafic and felsic ultrahigh-pressure metamorphic rocks from the Dabie UHPOrogen, China: insights into supercritical liquids in continental subduction zones

Jian Huanga,b* and Yilin Xiaoa*aCAS Key Laboratory of Crust–Mantle Materials and Environments, School of Earth and Space Sciences, University of Science

and Technology of China, Hefei, PR China; bDepartment of Geochemistry, Geoscience Centre of the University of Göttingen, Göttingen,Germany

(Received 8 October 2013; accepted 7 February 2014)

Geochemical analyses of minerals and whole rocks for major and trace elements as well as Sr-Nd-O isotopes on samplesalong a profile across the boundary between amphibolite retrogressed from ultrahigh pressure (UHP) eclogite and its countryrock granitic gneiss from the South Dabie low-T/UHP zone, China, are studied to assess the process that controls elementmobility under extreme metamorphic conditions. Directly at the contact with the granitic gneiss, the amphibolite has higherconcentrations of K, Al, LILEs, REEs, HFSEs, Th, and U, slightly lower concentrations of SiO2, MgO, and CaO, but verysimilar FeOt and transitional metal element contents relative to the other amphibolites further away from the boundary.Consistently, δ18O values of the amphibolite display a progressive increase towards the boundary, indicating fluid-assistedO-isotope exchange across the contacts of different lithologies at local scales. These can neither be attributed to amphibolite-facies retrogression of eclogite, which is known to have no significant effect on their major and trace elements, nor to Si-richmetasomatism from partially melted granitic gneiss, which should increase the silica content of the amphibolite at thecontact. Therefore, neither of the two processes is viable here. We thus propose that the variations observed here werecaused by metasomatism of supercritical liquids that were generated at pressure higher than that of the second criticalendpoint in the granitic gneiss–H2O system. This interpretation is supported by multiphase solid inclusions of K-feldspar + quartz + calcite + zircon ± amphibole ± clinozoisite ± garnet ± apatite within garnet in the amphibolite.

Keywords: UHP metamorphism; eclogite; gneiss; element mobility; fluids

1. Introduction

It is widely accepted that fluids released from deeplysubducted rocks play a key role in metasomatism andpartial melting of the mantle wedge in the generation ofisland arc magmas with their characteristic enrichment oflarge ion lithosphile elements (LILEs) and light rare earthelements (LREEs) relative to high field strength elements(HFSEs) (e.g. McCulloch and Gamble 1991). Such fluidsare also involved in the formation and preservation of(ultra-)high pressure [(U)HP] rocks (e.g. Hermann et al.2006) and even intermediate–deep earthquakes (Davies1999). A number of previous studies have shown that aconsiderable removal of LILEs and/or LREEs from meta-basites is coupled with dehydration of the subducted slab(e.g. Kogiso et al. 1997; Becker et al. 2000; Gao et al.2007), whereas other studies suggest that aqueous fluidsliberated at the blueschist to eclogite facies transition arediluted and hence are unable to result in significant releaseof trace elements from mafic rocks during subduction (e.g.Spandler et al. 2003; Hermann et al. 2006; Miller et al.2007). This contrast between dehydration and trace ele-ment mobility principally concerns the type and composi-tion of fluid involved and the degree and mechanism of

element transport with respect to open or closed systemsduring prograde metamorphism.

Three distinct types of fluids (i.e. aqueous fluids,hydrous melts, and supercritical liquids) have been experi-mentally identified under subduction-zone metamorphicconditions (e.g. Manning 2004; Kessel et al. 2005a;Hack et al. 2007). In the silicate–H2O system, only aqu-eous fluids coexist with the solid silicate below the water-saturated solidus, and hydrous melts do not appear untilthe P-T values increase passing the solidus. With a furtherincrease of P and T at passing of the liquidus, the silicatebecomes completely molten and thus only hydrous meltsare present. At high pressure, the wet solidus terminates ata second critical endpoint, which is defined as the inter-section between the wet solidus and the critical curve (e.g.Boettcher and Wyllie 1969; Manning 2004; Hermannet al. 2006; Zheng et al. 2011b). At pressures higherthan that of the second critical endpoint, hydrous meltsand aqueous fluids become completely miscible and con-verge into one single phase known as supercritical liquids.In addition to experimental results, direct evidence forcomplete miscibility between silicate materials and H2Owas also found in various types of natural rocks (e.g.Navon et al. 1988; Hwang et al. 2001; Stöckhert et al.

*Corresponding authors. Email: jianhuang@ustc.edu.cn (J. Huang) or ylxiao@ustc.edu.cn (Y. Xiao)

International Geology Review, 2015Vol. 57, Nos. 9–10, 1103–1129, http://dx.doi.org/10.1080/00206814.2014.893213

© 2014 Taylor & Francis

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

2001; Ferrando et al. 2005; Frezzotti et al. 2007).Because hydrous melts and silica-rich supercritical liquidscan dissolve more trace elements (including nominallyimmobile elements) than aqueous fluids, they may play acritical role in controlling the mobility, transport, andfractionation of elements within the crust and upper man-tle (e.g. Bureau and Keppler 1999; Manning 2004; Kesselet al. 2005a; Hermann et al. 2006; Hack et al. 2007;Zheng et al. 2011b).

The Dabie–Sulu orogenic belt represents the largestUHP terrain recognized in the world to date. (U)HP meta-morphic rocks from this belt present an excellent naturallaboratory in which to study the nature of fluid phases andelement mobility in continental collision zones. Abundanthydrous minerals (e.g. epidote, zoisite, phengite, magne-site, talc, and Ti-clinohumite; Liou et al. 1998) and fluid-related (U)HP veins within metamorphic rocks from thisregion have been recognized (e.g. Castelli et al. 1998;Franz et al. 2001; Li et al. 2004; Xiao et al. 2006a,2011; Zheng et al. 2007; Zhang et al. 2008; Zong et al.2010; Sun et al. 2011; Guo et al. 2012; Huang et al. 2012;Sheng et al. 2012). P-T estimations have suggested thatthe peak temperature (Tmax) of the Dabie–Sulu UHP meta-morphic rocks occurred during ‘hot’ exhumation, not atthe peak pressure (Pmax) (e.g. Carswell et al. 1999; Zonget al. 2011; Xia et al. 2012). In response to ‘hot’ exhuma-tion, partial melting has been proposed to occur duringinitial exhumation of the deeply subducted continentalcrust (e.g. Hermann et al. 2006; Zheng et al. 2011b). Infact, post-peak metamorphic ages of granitic leucosomeand pegmatite within biotite-bearing orthogneiss (Liuet al. 2010), petrographic and geochemical studies oneclogites and granitic gneisses (Zhao et al. 2007a; Xiaet al. 2008), and discovery of quartzfeldspathic inclusionswithin omphacite and garnet in UHP eclogites (Gao et al.2012, 2013) all suggest that the Dabie–Sulu UHP meta-morphic rocks were subjected to partial melting duringexhumation.

Extensive fluid inclusion studies on the Dabie–SuluUHP metamorphic rocks have shown that pre- and syn-UHP metamorphic fluids are NaCl-dominated high-sali-nity fluids with/without N2 or CH4, and that CO2 andlow-salinity aqueous fluids (or pure water) formed duringpost-peak metamorphism (Xiao et al. 2000, 2001, 2002;Fu et al. 2003; Zhang et al. 2005, 2011). Recently, find-ings of primary multiphase solid (MS) inclusions withinUHP minerals (e.g. kyanite and garnet) suggest that high-density supercritical silicate-rich liquids were presentunder UHP conditions (Ferrando et al. 2005; Frezzottiet al. 2007). This is also indicated by studies of UHPveins within eclogites and different types of zircons ingranitic gneisses (Zhang et al. 2008; Xia et al. 2010).

Although supercritical liquids have been suggested toform during subduction-zone metamorphism on the basisof experimental studies and hypothesized in natural rocks

by some studies (e.g. Hermann et al. 2006; Zheng et al.2011b), direct studies of their effect on element mobility innatural UHP metamorphic rocks to date are very sparse.This is because the occurrence and chemical traces of suchfluids may represent a transient effect during the evolutionof UHP terrains, leaving little evidence in the rocks afterexhumation. In the present study, we carried out a com-bined investigation of petrology, mineral chemistry, majorand trace elements, and Sr-Nd-O isotopes on UHP eclogite(retrogressed to amphibolite) and granitic gneiss from theSouth Dabie low-T/UHP Zone (SDZ). The results enhanceunderstanding of the nature and action of supercriticalliquids and the associated element mobility under UHPmetamorphic conditions.

2. Geological background

The Dabie–Sulu orogenic belt in east-central China wasformed in response to Triassic subduction and continentalcollision of the South China Block beneath the NorthChina Block (e.g. Li et al. 1999; Liu et al. 2011 andreferences therein). The occurrence of coesite and micro-diamond in eclogite and its country rocks (e.g. gneiss,marble, and peridotite) within the metamorphic belt isindicative of UHP metamorphism (e.g. Okay et al. 1989;Xu et al. 1992). The Dabie terrane lies in the western partof the orogenic belt and consists of several fault-boundedrock units that can be subdivided – from north to south –into five major lithotectonic zones (Zheng et al. 2005): (1)the Beihuaiyang low-T/low-P greenschist-facies zone; (2)the North Dabie high-T/UHP granulite-facies zone; (3) theCentral Dabie medium-T/UHP eclogite-facies zone; (4)the South Dabie low-T/UHP eclogite-facies zone; and (5)the Susong low-T/high-P blueschist-facies zone. The UHPmetamorphic event occurred between 242 ± 2 and227 ± 2 Ma, and the protolith of the meta-igneous rocksformed in the middle Neoproterozoic, mainly from 780 to740 Ma (e.g. Zheng 2008 and references therein).

The SDZ, often referred as the Huangzhen–Zhujiachong area in the literature, is tectonically sand-wiched between the northern Central Dabie mid-T/UHPzone and the southern Susong low-T/HP zone (Figure 1).This zone is mainly composed of gneiss, eclogite, andamphibolite (Shi and Wang 2006). Eclogite and amphibo-lite occur as blocks or boudins in the gneisses and range insize from metres to hundreds of metres (Shi and Wang2006). In early studies, no coesite and diamond werefound in this zone. Metamorphic conditions were esti-mated to be 650–700°C and 1.8 GPa by one school(Castelli et al. 1998), but 570–650°C and 1.8–2.5 GPaby another (Carswell et al. 1997; Franz et al. 2001). Thuslow-T eclogite, also termed ‘cold’ eclogite, was so calledbecause of the apparent low temperatures relative to theCentral Dabie mid-T eclogites (Carswell et al. 1997).However, coesite inclusions in zircon from granitic gneiss

1104 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

(Liu et al. 2001) and quartz pseudomorphs after coesite ingarnet from eclogite (Li et al. 2004) have since beenidentified, demonstrating that both the ‘cold’ eclogite andits country rock gneiss also underwent UHP metamorph-ism. In consideration of the occurrence of coesite, therecalculated peak metamorphic conditions for eclogite are~3.3 GPa and ~670°C (Li et al. 2004). Therefore, the SDZhas been redefined as a low-T/UHP eclogite-facies zone.More recent studies have indicated that the peak tem-perature could reach ~750°C at ~2.0 GPa in response tothe ‘hot’ exhumation of the deeply subducted continentalcrust (Xia et al. 2008; Zheng et al. 2011a).

Li et al. (2004) carried out multi-geochronologicalstudies of eclogite from the SDZ, obtaining two groupsof metamorphic ages at 242 ± 3 Ma and 222 ± 4 Ma fromSHRIMP zircon U-Pb dating, and ages of 236 ± 4 Ma and230 ± 7 Ma from mineral Sm-Nd and Rb-Sr isochrondating, respectively. Two groups of granitic gneiss withdifferent petrographic and geochemical features in theSDZ have been recognized (Xia et al. 2008). Group Igneisses are located in the northern part of the SDZ,whereas Group II gneisses occur in the southern part. Asdocumented by Xia et al. (2008), Group I gneisses arelepidoblastic with a metasomatic relict texture and onlyexperienced metamorphic dehydration; in contrast, GroupII gneisses are leucogranitic with a granoblastic textureand suffered from dehydration melting during ‘hot’ exhu-mation. Zircon U-Pb dating for the two gneiss groupsyields two age clusters at 778 ± 13 Ma and 223 ± 4 Ma,

respectively, corresponding to formation of the porotlith inthe Neoproterozoic and metamorphic modification in theTriassic (Xia et al. 2009).

3. Sample description and petrology

Granitic gneiss and amphibolite investigated in thisstudy were drilled out from an outcrop near theTaihu–Mamiao–Jiutian road at Zhujiachong in theSDZ (Figure 2). The amphibolite occurs as a massiveblock tens of metres in size and has a sharp contactwith its gneiss host. The gneiss has a S-dipping folia-tion that is nearly parallel to the boundary betweengneiss and amphibolite, and no evidence for veiningwas found (Figure 2). A total of 10 samples weretaken from a ~1.8 m profile perpendicular to the folia-tion and boundary. Among these 10 samples, five aregneiss (P1–P5), the other five being amphibolite (P6–P10). Samples P1 (gneiss) and P10 (amphibolite) definethe start and end points of the profile, respectively. Thedistance to the contact was measured for each sampleby ruler, and their mineral abundances (vol.%) wereestimated using a petrographic microscope (Table 1).

3.1. Granitic gneiss

The granitic gneiss is composed of quartz + plagioclase + K-feldspar + mica (muscovite and biotite) + chlorite + epidote-group minerals (e.g. epidote, clinozoisite and

Figure 1. Sketch map of simplified geology in the southeastern part of the Dabieshan (modified after Li et al. 2004). Insert indicates thelocation of the study area at the eastern end of the Qinling–Dabie orogenic belt between the North China Craton and the Yangtze Craton.

International Geology Review 1105

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

zoisite) + rutile + titanite + zircon ± magnetite ± ilmenite(Figure 3(a)). Fine-grained (<250 μm) garnet was onlyfound in one gneiss sample (P5) at the contact with theamphibolite. Biotite was pervasively subjected to partialchloritization, and some phengitic muscovite grains werepartially transformed into biotite and chlorite.Heterogranular rutile and zircon occur in the matrix oras inclusions in quartz, plagioclase, mica, and eventitanite.

3.2. Amphibolite

Li et al. (2004) demonstrated that all (garnet-)amphibolitesfrom the SDZ formed from retrogression of early UHPeclogites. In this study, omphacite is completely replacedby symplectite of amphibole and plagioclase, indicatingthat the amphibolite is a retrograded UHP eclogite.Amphibolite P6 at the contact is mainly composed ofamphibole + plagioclase + biotite + muscovite + quartz,with accessary minerals of rutile, titanite, ilmenite, and

Figure 2. Outcrop photograph of the sampled felsic and mafic rocks with locations where samples in this study were drilled out. The reddashed line denotes the boundary between felsic and mafic rocks (granitic gneiss versus amphibolite retrogressed from previous eclogite).The scale bar indicates the approximate size of the sample profile.

Table 1. Mineral assemblages and estimated volume contents (%) of the studied gneiss and amphibolites in the SDZ, central-easternChina.

Sample DTC (cm) Amp Qtz Pl Kfs Ms Bi Grt Rt Mag Ttn Ilm Zrn Ep Czo/Zo Chl Sym

gneissP1 −70.5 – 60 26 T 2 8 – T 1 1 T T T T 1 –P2 −57.5 – 60 25 T 1 10 – T 1 T T T 1 T T –P3 −37.5 – 55 30 T 1 6 – T 1 T T T T T 4 –P4 −20.5 – 60 30 T 1 6 – T T T 2 T T T T –P5 −4 – 60 25 T 2 8 T T – 1 – T T T 3 –amphiboliteP6 2 50 5 25 – 3 8 – 3 – T T T – – – 2P7 13 20 2 2 T 2 2 15 3 – 1 2 T T T – 50P8 37 30 1 3 – 1 5 15 2 – – 2 T T 1 – 40P9 74.5 30 2 3 – T 5 10 1 – T 2 T T 1 – 45P10 107.5 30 1 2 – 1 3 10 1 – T 2 T T 3 – 45

Notes: Amp, amphibole; Qtz, quartz; Pl, plagioclase; Kfs, K-feldspar; Ms, muscovite; Bi, biotite; Grt, garnet; Rt, rutile; Mag, magnetite; Ttn; titanite; Ilm,ilmenite; Zrn, zircon; Ep, epidote; Czo/Zo; clinozoisite/zoisite; Chl, chlorite; Sym, symplectite (amphibole and plagioclase after omphacite). T denotestrace, and DTC denotes distance to the contact between gneiss and amphibolite.

1106 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

zircon. The other four amphibolites are mainly made up ofgarnet, aligned hornblende, plagioclase, mica (muscoviteand biotite), and quartz with accessory minerals of rutile,ilmenite, titanite, zircon, epidote, and clinozoisite/zoisite(Figure 3(b)). Garnet is replaced by a symplectitic coronaof amphibole + plagioclase (Figure 3(c)), and rutile isrimmed by, or entirely retrogressed to, titanite or ilmenite(Figure 3(d)). Abundant mineral inclusions of plagioclase,amphibole, rutile, clinozoisite, and paragonite with tracesof apatite and chlorite in garnet were identified by petro-graphic observations, laser Raman analysis, back-scattered

electron (BSE) imaging, and SEM-EDS analysis (Figure 3(c)). In addition, the coexistence of MS inclusions such asK-feldspar + quartz + calcite + zircon + amphibole +clinozoisite and K-feldspar + quartz + calcite + zircon +garnet + apatite was also found in garnet (Figure 3(e)and (f)). The inclusions have similar mineral assemblagesand are surrounded by radial cracks in the host garnet,suggesting that they are primary and likely originate froman early-trapped fluid or melt (Ferrando et al. 2005). Theminerals within inclusions such as K-feldspar, calcite,apatite, garnet, quartz, and zircon (spectrum not shown)

Figure 3. Photomicrographs of the investigated granitic gneiss and amphibolite (retrogressed from previous eclogite). (a) Cross-polarized light image of gneiss (sample P1). It is mainly composed of quartz, plagioclase, biotite, and muscovite, with accessoryminerals including epidote, K-feldspar, chlorite, magnetite, rutile, titanite, ilmenite, and zircon (not shown). (b) Plane-polarized lightimage of garnet-amphibolite (sample P7). It mainly contains amphibole, garnet, plagioclase, rutile, ilmenite, and symplectite (amphi-bole + plagioclase). (c) BSE image of symplectitic plagioclase and amphibole after garnet, which contains inclusions of plagioclase,amphibole, and rutile (sample P7). (d) BSE image of rutile rimmed by titanite (sample P7). (e)–(f) BSE image of MS inclusions in garnetfrom amphibolite (sample P7): K-feldspar + quartz + calcite + zircon + garnet + apatite (e); K-feldspar + quartz + calcite + zircon + amphi-bole + clinozoisite (f). The small pit in calcite was caused by the EMP beam.

International Geology Review 1107

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

were further confirmed by laser Raman spectrometry(Figure A1).

4. Analytical methods

4.1. Mineral chemistry and Raman analysis

Electron microprobe (EMP) analyses were performed atthe University of Göttingen using a JEOL JXA 8900superprobe equipped with wavelength-dispersive spectro-meters (WDSs) and an energy-dispersive spectrometer(EDS). Operating conditions were an accelerating voltageof 15.0 kV and beam current of 10 nA. In most cases, theelectron beam diameter was set to 10 µm, except for somevery fine-grained mineral inclusions analysed using a dia-meter of 1–5 µm. The counting time was 15 s for all thedetermined elements (i.e. Si, Na, K, Ti, Fe, Al, Mg, Ca,Cr, Mn, Cl, and Ba). Both silicates and pure oxides wereused as standards: olivine for SiO2 and MgO, wollastonitefor CaO, synthetic TiO2 crystal for TiO2, anorthite forAl2O3, synthetic Cr2O3 crystal for Cr2O3, haematite forFeO, rhodonite for MnO, barite for BaO, albite for Na2O,sanidine for K2O, and synthetic NaCl crystal for Cl.

Laser Raman analyses were carried out at theUniversity of Science and Technology of China (USTC)to further identify some small mineral inclusions hosted bygarnet. The minerals were analysed using a ThermoScientific DXR Raman spectrometer with 1~3 mW and532 nm Nd (YVO4 DPSS) laser excitation at room tem-perature. The beam size was set to ~0.6 μm.

4.2. Whole-rock major and trace elements

For whole-rock analyses, the investigated samples werefirst crushed in a corundum jaw crusher to 60 mesh, andthen about 60 g of each crushed sample was powdered inan agate ring mill to less than 200 mesh. Major elementswere analysed by wet-chemistry methods (following theNatural Standard Method: GB/T14506.1~14‒1993) at theLangfang Laboratory of Regional Geological ExplorationBureau of Hebei Province (China). Al2O3, MgO, CaO,and FeO were determined by titration; SiO2, TiO2,Fe2O3, and P2O5 were measured in solution by spectro-photometry; K2O and Na2O were measured by flamephotometry; and MnO was measured by atomic-absorp-tion spectrometry. Loss of ignition (LOI) was determinedby gravimetric methods using an electronic balance.Analytical uncertainties for the majority of major elementswere better than 1%. For trace element determination,~50 mg of bulk rock powders were precisely weighedinto a Teflon bomb and moistened with a few drops ofultra-pure water. After adding a mixture of 1.5 ml ultra-pure HNO3 + 1.5 ml ultra-pure HF + 0.01 ml ultra-pureHClO4 acid, the solution was heated and evaporated todryness at ~110°C. Then, 1.5 ml ultra-pure HNO3 + 1.5 ml

ultra-pure HF were added again, and the sealed bomb washeated for 48 h in an oven at 190°C. Again, the solutionwas evaporated to dryness followed by the addition of3 ml ultra-pure HNO3, and then to the state of wet salt.The resultant salt was re-dissolved by adding 3 ml 50%HNO3 and then heated for at least 12 h with closed caps inthe oven at 150°C. The final solution was diluted to ~80 gusing ultra-pure water before analysis. An internal stan-dard solution of single-element Rh was used with a dilu-tion factor of 1/1250 in 2% HNO3. Analyses were carriedout using an ELAN DRCII inductively coupled plasmamass spectrometer (ELAN DRCII ICP-MS) at the USTC.Analytical procedures were as described in detail by Houand Wang (2007). The results for two USGS standards(AGV-2 and BHVO-2) determined during the course ofthe analyses are presented in Table A1 (see Appendix forTables A1 to A3 and Figures A1 and A2). Precision(relative standard deviation, RSD) is better than 5% formost elements, except for Pb in BHVO-2, which has asomewhat lower precision of 14%. Accuracy, as indicatedby relative error (RE) between measured and recom-mended values, is better than 10%, with many elementsagreeing to within 3% of the recommended values.Exceptions are Th, U, Ta, and Ni in AGV-2 (which differby up to 16% for Th, 16% for U, 15% for Ta, and 22% forNi) and Pb in BHVO-2, which differs by up to 58%. Thislarge difference may be due to the low concentration of Pbin BHVO-2; the correspondence between measured andrecommended reference values is better for AGV-2, whichhas a higher concentration of Pb. Our studied sampleshave concentrations of Pb similar to that in AGV-2(Tables 2 and A1). This leads us to conclude that the Pbvalues for our studied samples are accurate to ~10%.

4.3. Whole-rock Sr-Nd-O isotopes

Whole-rock Sr and Nd isotopic analyses were accomplishedby TIMS (Finnigan MAT 262) at the USTC. About 100–150 mg whole-rock powder was completely dissolved in amixture of HF-HClO4 for Sr-Nd isotopic analyses.Strontium and light rare earth elements (LREEs) were sepa-rated on quartz columns by conventional ion exchangechromatography with a 5 ml resin bed of AG 50W-X12,200–400 mesh. Samarium and Nd were further isolatedfrom other REE on quartz columns using 1.7 ml Teflon®

powder coated with HDEHP® as the cation exchange med-ium. The Sr-Nd isotopic ratios were measured by aFinnigan MAT-262 mass spectrometer. Strontium wasloaded with a Ta-HF activator on a single W filament, andNd was loaded as phosphates and measured in a Re double-filament configuration. The 87Sr/86Sr and 143Nd/144Nd ratioswere normalized against 87Sr/86Sr = 0.1194 and 143Nd/144Nd = 0.7219. During the course of data acquisition, theNBS-987 internal Sr isotope standard gave a 87Sr/86Sr ratioof 0.710250 ± 0.000015 (2σ), very close to the reported

1108 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Table 2. Bulk rock major and trace element concentrations of the studied gneiss and amphibolites in the SDZ, central-eastern China.

Rock Gneiss Amphibolite

Sample P1 P2 P2* P3 P3* P4 P5 P6 P6* P7 P8 P9 P10 P10*

Major element (wt.%)SiO2 71.6 72.6 65.6 68.7 72.1 46.9 49.8 50.0 49.8 48.4TiO2 0.35 0.32 0.46 0.57 0.40 1.17 0.88 1.07 0.92 1.07Al2O3 14.4 13.5 16.7 14.3 13.4 19.6 15.9 15.8 16.0 16.6Fe2O3 0.88 0.53 1.52 2.16 0.89 2.84 3.23 2.93 3.48 3.31FeO 1.87 1.99 2.06 2.25 2.01 8.26 7.11 7.47 6.44 7.98MnO 0.076 0.074 0.084 0.099 0.079 0.38 0.27 0.23 0.18 0.19MgO 1.67 1.50 2.04 1.61 2.04 6.75 8.88 8.71 8.15 8.65CaO 1.12 1.12 1.55 3.13 1.83 6.18 7.95 8.99 9.13 8.27Na2O 5.67 5.46 6.29 4.35 4.51 3.52 4.01 3.05 3.63 3.19K2O 1.47 1.44 1.33 1.29 1.11 2.24 0.64 0.35 0.64 1.00P2O5 0.03 0.03 0.07 0.21 0.06 0.13 0.27 0.34 0.58 0.21LOI 0.92 0.98 1.73 1.30 1.20 2.18 1.44 1.59 1.61 1.76H2O+ 0.66 0.68 1.30 0.96 1.04 1.53 0.78 0.84 0.86 1.24H2O– 0.13 0.12 0.20 0.27 0.14 0.24 0.10 0.17 0.12 0.19Total 100.1 99.6 99.5 100.0 99.6 100.1 100.4 100.5 100.5 100.6A/CNK 1.11 1.08 1.15 1.00 1.12 1.01 0.73 0.73 0.69 0.78Mg# 52.8 52.0 51.5 40.6 56.4 52.7 61.2 60.6 60.3 58.5

Trace element (ppm)Li 8.70 6.34 7.82 9.18 5.96 0.00 8.85 30.3 29.5 6.63 4.45 4.35 13.0 12.0Be 1.27 1.15 1.24 1.45 1.46 1.23 1.16 1.14 1.11 0.95 0.99 0.88 0.66 0.64Sc 13.3 11.3 11.5 14.5 12.8 14.1 12.5 37.8 37.5 30.1 33.8 31.0 34.2 33.1V 20.4 19.5 19.8 28.4 28.2 64.7 28.8 181 171 216 242 245 228 224Cr 4.13 1.84 2.41 1.60 2.57 12.9 3.38 224 218 228 213 194 224 220Co 4.10 3.66 3.53 5.72 5.60 5.87 5.91 38.3 36.2 44.9 44.4 42.6 44.5 43.8Ni 2.11 5.47 3.23 2.36 3.59 6.16 2.32 73.5 69.5 126.0 122 107 91.0 89.8Cu 4.55 6.14 4.91 4.55 4.17 9.57 198 10.3 9.11 7.90 43.3 19.9 11.9 11.8Zn 41.4 43.4 43.2 54.2 76.0 59.2 49.3 148 110 179 193 122 87.4 86.1Ga 15.6 14.2 14.5 17.7 17.3 18.3 15.6 20.6 20.0 17.2 19.2 19.7 17.7 17.4Rb 24.1 21.3 20.9 24.2 23.9 21.8 22.7 48.4 48.5 12.2 9.0 12.7 21.9 21.8Sr 84.7 76.6 77.4 136 135 566 481 466 469 194 393 475 459 463Y 32.0 29.5 30.6 35.1 34.2 32.6 42.3 34.9 35.4 18.6 21.9 19.3 21.7 21.6Zr 213 202 212 216 213 222 202 139 149 99 117 101 107 108Nb 6.42 5.94 6.23 6.30 6.13 5.74 6.07 4.72 4.42 2.86 3.37 2.73 3.02 3.01Cs 0.82 0.75 0.78 0.86 0.84 0.76 0.42 1.58 1.61 0.25 0.00 0.13 0.71 0.69Ba 824 851 886 881 870 886 1210 1714 1734 347 220 364 514 512La 25.4 19.8 20.5 32.5 31.8 30.9 28.4 25.9 26.5 11.6 13.4 14.7 15.8 15.8Ce 53.3 42.7 44.5 64.1 62.8 63.7 58.0 55.6 56.0 25.3 29.0 32.0 33.6 33.5Pr 6.62 5.34 5.54 7.95 7.78 7.84 7.19 7.15 7.26 3.34 3.80 4.21 4.31 4.29Nd 26.8 21.9 22.7 31.5 30.8 31.1 29.0 30.1 30.5 14.5 16.4 18.3 18.3 18.2Sm 5.42 4.51 4.72 6.25 6.10 6.08 6.01 6.17 6.23 3.19 3.53 4.05 3.79 3.79Eu 1.47 1.23 1.28 1.68 1.64 1.78 1.90 2.37 2.36 1.21 1.31 1.54 1.47 1.46Gd 5.28 4.42 4.64 6.16 6.08 5.92 6.26 6.32 6.30 3.43 3.68 4.08 3.81 3.80Tb 0.78 0.68 0.71 0.87 0.86 0.80 0.96 0.92 0.91 0.52 0.55 0.54 0.55 0.54Dy 4.97 4.38 4.69 5.38 5.32 4.85 6.15 5.58 5.59 3.12 3.50 3.14 3.38 3.34Ho 1.03 0.92 0.97 1.10 1.08 0.96 1.26 1.09 1.10 0.61 0.70 0.60 0.69 0.67Er 3.13 2.81 2.99 3.36 3.29 2.89 3.84 3.16 3.14 1.78 2.04 1.77 2.00 1.95Tm 0.46 0.40 0.44 0.48 0.47 0.40 0.56 0.43 0.43 0.24 0.28 0.24 0.27 0.26Yb 3.26 2.86 3.06 3.36 3.31 2.74 3.93 2.86 2.84 1.65 1.95 1.67 1.80 1.76Lu 0.50 0.44 0.48 0.51 0.50 0.41 0.60 0.43 0.42 0.25 0.29 0.25 0.27 0.26Hf 4.75 4.31 4.72 4.71 4.66 4.66 4.36 2.89 3.01 2.04 2.34 1.99 2.12 2.05Ta 0.30 0.26 0.28 0.29 0.29 0.30 0.28 0.24 0.22 0.15 0.18 0.15 0.16 0.16Pb 11.4 5.9 13.7 14.5 12.1 17.1 12.0 21.2 16.4 6.8 8.7 12.4 14.7 11.8Th 3.59 3.21 3.44 3.79 3.75 4.73 2.92 1.87 1.86 0.85 1.18 0.84 1.00 0.97U 0.73 0.60 0.64 0.75 0.75 1.06 0.46 0.37 0.35 0.17 0.19 0.18 0.19 0.17∑LREE 124 99.9 104 150 147 147 137 134 135 62.6 71.1 78.9 81.1 80.8(La/Sm)N 3.03 2.83 2.80 3.36 3.37 3.28 3.05 2.71 2.75 2.35 2.45 2.34 2.69 2.69(La/Yb)N 5.59 4.97 4.81 6.94 6.89 8.09 5.18 6.50 6.69 5.04 4.93 6.31 6.30 6.44Eu/Eu* 0.84 0.84 0.84 0.83 0.82 0.91 0.95 1.16 1.15 1.12 1.11 1.16 1.18 1.18

Note: Pdigital* denotes the replicated analysis of the same sample; A/CNK denotes the mole ratio of Al2O3/(CaO + Na2O + K2O); Eu/Eu* = EuN/(SmN ×GdN)

0.5, where the subscript N for each element denotes normalized by chondrite from Sun and McDonough (1989).

International Geology Review 1109

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

value of 0.710253 ± 0.000032 (2σ, Chen et al. 2007a), andthe La Jolla internal Nd isotope standard yielded a 143Nd/144Nd = 0.511876 ± 0.000010 (2σ), equivalent to the refer-ence value within uncertainty (0.511865 ± 0.000008, 2σ,Roddick et al. 1992). During the course of Nd model ageand initial 86Sr/87Sr ratio calculations, whole-rock Sm-Ndand Rb-Sr concentrations were derived from the ICMPSmeasurements mentioned above. Single-stage Nd modelages (TDM1) were calculated relative to the depleted mantlewith 147Sm/144Nd and 143Nd/144Nd ratios of 0.2137 and0.51315, respectively (DePaolo 1988). Two-stage Ndmodel ages (TDM2) were obtained at different ages of mag-matism relative to the average continental crust with a147Sm/144Nd ratio of 0.118 (Jahn and Condie 1995), assum-ing a protolith age of 780 Ma and a metamorphic age of230 Ma (Li et al. 2004; Xia et al. 2009).

Whole-rock oxygen isotope analysis was conductedusing the CO2 laser fluorination technique at theUniversity of Göttingen. About 0.5–1.5 mg whole-rockpowder was loaded in a nickel holder with eighteen2 mm-deep holes. After pumping for ~2 h, the whole-rock powder was melted by gradually increasing the CO2

laser intensity, and then the molten samples were evacu-ated overnight before loading the sample chamber with F2.The molten samples were reacted with F2 during heatingof the CO2 laser to obtain O2. Oxygen was purified in away similar to the UV laser method as described byWiechert et al. (2002), collected in a molecular sieve,and transferred to the Finnigan Deltaplus for the measure-ment of 18O/16O ratios. The results are reported in theconventional δ notation relative to the standard meanocean water (SMOW). The average δ18O value(12.35 ± 0.12‰, 1σ, n = 4, this standard deviation istaken as our uncertainty) of Dörentrup quartz standardanalysed in this study is indistinguishable from the pre-viously reported value (12.10 ± 0.14‰, 1σ; Wiechert et al.2002) obtained using the same method.

5. Results

5.1. Mineral chemistry

Major element compositions of the representative mineralsare presented in Table A2.

5.1.1. Garnet

Subhedral garnet in the gneiss P5 is relatively homoge-neous in major elements and displays a composition of~Prp22Grs13Alm59Sps6. Elongated garnet in the amphibo-lite shows a well-defined zonation. Pyrope increases(Prp14.9 to Prp28.6), while grossular and almandinedecrease (Grs29.5 to Grs20.1, Alm55.5 to Alm48.6) fromcore to rim, corresponding to a process of progressivemetamorphism.

5.1.2. Amphibole

Amphibole was only observed in the amphibolite. Theanalysed amphiboles belong to magnesio-hornblendeaccording to the classification of Leake et al. (1997).There are two types of amphibole according to theirtexture: the first was formed earlier and is enclosed ingarnet; the second was formed late and occurs as rims ofporphyroblastic garnet and retrogressive symplectite (orproduct) of pre-existing omphacite. The first type has12.5–17.7 wt.% Al2O3, 10.9–16.1 wt.% MgO, and 1.81–2.49 wt.% Na2O, whereas those in the second type are6.47–19.8 wt.%, 8.37–16.3 wt.%, and 1.04–2.47 wt.%,respectively.

5.1.3. Epidote-group minerals

Based on their optical properties and chemical composi-tions, epidote-group minerals such as epidote and clino-zoisite were found in both rock types, while zoisite wasadditionally found in the amphibolite. Epidote and clino-zoisite in the gneiss show slightly different contents inAl2O3 (Ep: 24.5–25.4 wt.%; Czo: 27.1–29.9 wt.%) andFeO (Ep: 10.6–11.4 wt.%; Czo: 5.35–8.54 wt.%). Thesame minerals in the amphibolite show similar Al2O3

ranges (Ep: 25.9–28.7 wt.%; Czo: 28.5–30.5 wt.%) andFeO ranges (Ep: 10.6–11.4 wt.%; Czo: 4.87–8.54 wt.%).The contents of Al2O3 and FeO in zoisite from the amphi-bolite range from 32.1 to 33.5 wt.% and 1.29–2.46 wt.%,respectively.

5.1.4. Feldspar

Plagioclase in both the gneiss and amphibolite is the maintype of feldspar with minor K-feldspar. K-feldspar in theamphibolite was only found as inclusions in garnet. EMPanalyses show that plagioclase in the gneiss has a compo-sition of ~Ab97An3 to ~Ab80An20, and in the amphibolite~Ab85An15 to ~Ab65An35. K-feldspar in the gneiss hasK2O contents of 15.1–16.9 wt.% and Al2O3 contents of18.5–19.2 wt.%, with higher Ba contents in the rim than inthe core (Table 3). K-feldspar inclusions within garnet inthe amphibolite have K2O contents of ~16.2 wt.% andAl2O3 contents of ~18.5 wt.%.

5.1.5. Mica

White mica occurs as phengitic muscovite in the gneissand as paragonite in the amphibolite. Phengitic muscovitedisplays K2O contents between 9.31 and 10.9 wt.% andNa2O contents between 0.15 and 1.33 wt.%, with a XSi-content cluster from 3.1 to 3.3. The BSE images andquantitative analysis on a phengitic muscovite grainshow a pronounced zoning pattern, with high Si and lowBa contents in the core and lower Si and higher Ba

1110 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

contents in the middle and the rim (Figure A2). Paragonitein the matrix and grains that are enclosed within garnethave similar Na2O contents (7.15–7.62 wt.%), but theformer has higher K2O contents (~1.0 wt.%) than the latter(~0.19 wt.%).

Biotite was found both in the gneiss and in the amphi-bolite. They have high contents of MgO (9.97–15.0 wt.%)and K2O (8.33–9.95 wt.%), with a XSi-content clusterfrom ~2.6 to 2.8 and XMg [Mg/(Mg + Fe total)] from 0.52to 0.66. The BaO and TiO2 contents in biotite range from0.35 to 1.25 wt.% and 1.56–3.25 wt.%, respectively.

5.1.6. Titanite

Concentrations of FeO and Al2O3 in titanite are from 0.28to 0.74 wt.% and from 0.93 to 1.9 wt.%, respectively. Allthe titanites analysed here have XAl [XAl = Al/(Al + Ti + Fe3+)] ranging from 0.034 to 0.073 and canbe classified as low-Al titanite (XAl < 0.25, Oberti et al.1991).

5.2. Whole-rock major and trace elements

Major and trace element compositions of the investigatedfelsic and mafic rocks are reported in Table 2 and plotted inFigures 4 and 5. The gneiss has a relatively narrow range ofSiO2 contents (67.1–73.6 wt.%, normalized by eliminatingLOI; same hereafter), with TiO2 (0.32–0.58 wt.%), Al2O3

(13.7–17.1 wt.%), FeOT (2.61–4.67 wt.%), MgO (1.52–2.09 wt.%), CaO (1.13–3.17 wt.%), and Na2O + K2O(5.71–7.79 wt.%) (Table 2). These features are equivalent

to the Group I gneisses that have higher contents of MgO(0.24–1.84 wt.%) and CaO (0.75–3.69 wt.%), but are rela-tively lower in SiO2 (65.9–73.9 wt.%) and Na2O + K2O(4.94–7.47 wt.%) when compared with Group II gneisses(Xia et al. 2008). The amphibolite shows minor variationsin SiO2 contents from 47.9 to 50.5 wt.%, with TiO2 from0.89 to 1.19 wt.%, Al2O3 from 16.0 to 20.0 wt.%, FeOT

from 10.4 to 11.8 wt.%, MgO from 6.89 to 8.97 wt.%, CaOfrom 6.31 to 9.23 wt.%, and K2O + Na2O from 3.44 to5.88 wt.% (Table 2).

Chondrite-normalized REE patterns show that all thegneisses display LREE enrichment (Figure 4(a)), with (La/Sm)N = 2.8–3.5 and (La/Yb)N = 4.8–8.1, and slightlynegative Eu anomalies with Eu/Eu* = 0.81–0.95 (Eu/Eu* = EuN/(SmN × NdN)

1/2). The amphibolite is enrichedin LREE with (La/Sm)N = 2.3–2.7 and (La/Yb)N = 4.9–6.7, and has slightly positive Eu anomalies with Eu/Eu* = 1.1–1.2 (Figure 4(b)). In particular, amphiboliteP6 has much higher REE contents relative to the others(Figure 4(b)).

The trace element patterns of the gneiss reveal signifi-cant enrichment in LILEs (e.g. K, Rb, Ba, Th, U, and Pb),but relative depletion in HFSEs (e.g. Nb, Ta, and Ti) and P(Figure 4(c)). These characteristics are very similar to theNeoproterozoic granite from Wulian region in the Suluorogenic belt (Huang et al. 2006). All amphibolites areconsistently enriched in LILEs and depleted in HFSEs(Figure 4(d)). However, amphibolite P6 at the transitionto gneiss has the highest degree of LILE enrichment. Forexample, amphibolite P6 has much higher contents of K2O(2.24 wt.%), Rb (48.4 ppm), Ba (1713 ppm), and Pb

Figure 4. Chondrite- and primitive mantle-normalized diagrams for the granitic gneiss (a, b) and the amphibolite (c, d). Chondrite andprimitive values are from Sun and McDonough (1989).

International Geology Review 1111

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

(21.2) when compared with the other amphibolites (0.35–1.0 wt.% K2O, 9.0–21.9 ppm Rb, 219–514 ppm Ba, and6.8–14.7 ppm Pb).

Thus, compared with the other amphibolites, amphibo-lite P6 at the transition to gneiss has much higher LILEs(e.g. K, Rb, Sr, Ba, Pb, Th, and U), HFSEs (e.g. Zr, Hf, Nb,Ta, and Ti), and REEs, slightly lower SiO2, MgO, and CaO,but very similar Cr and Ni contents (Table 2 and Figure 5).

5.3. Whole-rock Sr-Nd-O isotopes

Results for Sr, Nd, and O isotopic analyses are listed inTable 3. Whole-rock 87Rb/86Sr ratios for the gneiss andamphibolite range from 0.11 to 0.82 and from 0.07 to0.30, respectively. Initial 87Sr/86Sr ratios vary significantlyfrom 0.7004 to 0.7057 at t1 = 780 Ma, but show a narrowrange of 87Sr/86Sr ratios ranging from 0.7064 to 0.7070 att2 = 230 Ma (i.e. the time of final metamorphic equilibra-tion) (Figure 6).

The gneiss has whole-rock 147Sm/144Nd and 143Nd/144Nd ratios ranging from 0.1182 to 0.1253 and from0.5119 to 0.5121, respectively. The εNd(t) values for thegneiss range from –7.1 to –3.1 at t1 = 780 Ma and from–12.3 to –8.5 at t2 = 230 Ma, respectively (Figure 6). Thiscorresponds to two-stage Nd model ages (TDM2) of 1.70–2.03 and 1.69–2.00 Ga.

The amphibolite has whole-rock 147Sm/144Nd and143Nd/144Nd ratios ranging from 0.1239 to 1338 andfrom 0.5121 to 0.5122, respectively, with εNd(t) values

from –4.1 to –2.4 at t1 = 780 Ma and from –9.1 to –6.8at t2 = 230 Ma, respectively. Single-stage Nd model agesfor the amphibolite vary from 1.74 to 1.92 Ga.

Oxygen isotopic compositions range from +0.59 to+1.29‰ in the gneiss and are from –1.11 to –2.21‰ inthe amphibolite (Table 3). As illustrated in Figure 7, thegneiss shows a slight decrease, while the amphibolite dis-plays a progressive increase in δ18O values towards itslithological boundary.

5.4. Estimated bulk compositions of MS inclusions

Regarding the modal abundance (roughly estimated fromBSE images), densities (Deer et al. 1992), and composi-tions of minerals (determined by EMP) in the inclusions,the bulk compositions of the MS inclusions have beenestimated. Two representative MS inclusions were selectedfor this estimation (Table A3). The results indicate highlyvariable bulk compositions of the inclusions, with SiO2

contents ranging from 39.9 to 41.8 wt.%, TiO2 from <0.01to 0.30 wt.%, Al2O3 from 9.04 to 13.3 wt.%, FeO from0.31 to 8.1 wt.%, MgO from 0.03 to 7.8 wt.%, CaO from12.8 to 25.2 wt.%, Na2O from 0.08 to 1.53 wt.%, and K2Ofrom 3.02 to 7.8 wt.% (Figure 8).

6. Discussion

Our geochemical data show that the amphibolite directlyin contact with the granitic gneiss has higher

Figure 5. Variations of selected major and trace elements across the boundary of different lithologies. The dash-dot line denotes theboundary between the granitic gneiss and amphibolite.

1112 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Table

3.Rb-Sr,Sm-N

d,andO

isotop

iccompo

sitio

nsof

thestud

iedgn

eiss

andam

phibolite

intheSDZ,central-easternChina.

Rb

Sr

87Rb/

87Sr/

I Sr(t1)

I Sr(t2)

Sm

Nd

147Sm/

143Nd/

ε Nd(t1)

ε Nd(t2)

TDM1

TDM2(G

a)δ1

8O

Sam

ple

(ppm

)(ppm

)86Sr

86Sr

780Ma

230Ma

(ppm

)(ppm

)144Nd

144Nd

780Ma

230Ma

(Ga)

t1(780

Ma)

t2(230

Ma)

(‰)

Gneiss

P1

24.09

84.73

0.82

2817

0.70

9535

0.70

0371

0.70

6843

5.42

26.8

0.12

2282

0.5118

94−7.1

−12

.32.09

2.03

2.00

1.28

9P2

21.27

76.59

0.80

3710

0.70

9631

0.70

0680

0.70

7002

4.51

21.9

0.12

4517

0.51

2056

−4.2

−9.2

1.86

1.79

1.75

0.76

5P3

24.19

135.93

0.51

5020

0.70

8035

0.70

2299

0.70

6350

6.25

31.5

0.1199

680.51

2088

−3.1

−8.5

1.72

1.70

1.69

0.94

4P4

21.77

565.89

0.1113

350.70

6972

0.70

5732

0.70

6608

6.08

31.1

0.1182

060.51

2056

−3.5

−9.1

1.74

1.74

1.74

0.58

9P5

22.67

480.89

0.13

6430

0.70

6825

0.70

5306

0.70

6379

6.01

29.0

0.12

5306

0.51

2066

−4.1

−9.1

1.86

1.78

1.74

0.77

7Amph

ibolite

P6

48.39

465.93

0.30

0565

0.70

7195

0.70

3847

0.70

6212

6.17

30.1

0.12

3941

0.51

2123

−2.8

−7.9

1.74

−1.113

P7

12.19

193.93

0.18

1913

0.70

6893

0.70

4867

0.70

6298

3.19

14.5

0.13

3021

0.51

2132

−3.5

−8.0

1.92

−1.42

0P8

8.99

392.93

0.06

6214

0.70

6316

0.70

5579

0.70

6099

3.53

16.4

0.13

0145

0.51

2153

−2.8

−7.5

1.81

−1.89

5P9

12.69

474.93

0.07

7328

0.70

6422

0.70

5561

0.70

6169

4.05

18.3

0.13

3814

0.51

2193

−2.4

−6.8

1.82

−2.20

8P10

21.89

458.93

0.13

8039

0.70

6618

0.70

5081

0.70

6166

3.79

18.3

0.12

5223

0.51

2063

−4.1

−9.1

1.87

−1.65

1

Notes:(1)I Sr(t)=(87Sr/86Sr)sample−(87Rb/

86Sr)sample*(eλ

t –1),where

λ=1.42

×10

−12year

–1;t 1=78

0Ma,

t 2=23

0Ma.

(2)Mod

eages

(TDM1)werecalculated

relativ

eto

thedepleted

mantle.Tw

o-stagemod

elages

(TDM2)werecalculated

relativ

eto

theaveragecontinentalcrustat

t 1=78

0Maandt 2=230Ma,respectiv

ely.

Average

continentalcrust:

147Sm/144Nd=0.118(JahnandCon

die19

95).Depletedmantle:147Sm/144Nd=0.2137

,143Nd/

144Nd=0.5131

5(D

ePaolo

1988).

(3)The

results

ofO

isotop

esarereported

intheconventio

nalδno

tatio

nrelativ

eto

thestandard

meanoceanwater

(SMOW).

International Geology Review 1113

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

concentrations of K, Al, LILEs, REEs, HFSEs, Th, and U,slightly lower concentrations of SiO2, MgO, and CaO,higher δ18O values, but very similar FeOt and transitionalmetal element contents relative to the other amphibolitesfurther away from the boundary (Figure 5 and Tables 2and 3). These geochemical variations were mainly causedby metasomatism of supercritical liquids derived from theadjacent granitic gneiss under UHP conditions, rather thanby protolith heterogeneity and other metasomatic agents(i.e. aqueous fluids and hydrous melts). In the followingsections, we will discuss these in detail.

6.1. Protolith heterogeneity

Numerous geochronological and geochemical studies havedemonstrated that the protoliths of the Dabie–Sulu eclo-gites and granitic gneisses are the mid-Neoproterozoicbimodal igneous rocks that formed in rift tectonic zonesalong the northern margin of the South China Block (e.g.Jahn et al. 2003; Zheng et al. 2004). The protolith ages ofthe metagranites and metabasites in the SDZ have beenconstrained at ~780 Ma (Xia et al. 2009; Xia et al. 2010).The studied granitic gneisses display enrichment of LILEsand LREEs but depletion of HFSEs and HREEs(Figure 4), suggesting that their protolith has the geochem-ical nature of evolved continental crust (e.g. Huang et al.2006). Negative εNd(t = 780) values of −7.1 to −3.1 andTDM ages of 1.70–2.03 for the gneisses in this study(Table 3), together with similar negative εHf(t = 780 Ma)

values of –8.3 to –2.2 and Hf model ages of 1.82–2.23 Gafor gneiss-hosted zircon from the same area (Xia et al.2009), suggest that the South Dabie gneisses are ulti-mately derived from Paleoproterozoic continental crust.The studied amphibolites have εNd(t = 780) values of –4.1to –2.4 and Nd mode ages of 1.74–1.92, indicatingthat their protoliths involved components of the middlePaleoproterozoic crust. This is consistent with a SHRIMPdiscordia upper-intercept age of 1817 ± 102 Ma obtainedfor eclogite from the same area (Li et al. 2004).

Differentiation of mantle-derived magmas will resultin lower contents of MgO and CaO, but higher contentsof SiO2 in the residual magmas (Niu 2005). Continentalcrust has lower MgO and CaO but higher SiO2 contentsthan mantle-derived magmas (Rudnick and Gao 2003).Thus, magma differentiation and/or crustal contaminationduring igneous processes in the Neoproterozoic shouldresult in a negative correlation between MgO (or CaO)and SiO2 in the eclogites/amphibolites. This is inconsis-tent with the observations that along the profile, theamphibolite P6 has lower contents of SiO2 (46.9 wt.%),MgO (6.75 wt.%), and CaO (6.18 wt.%) than otheramphibolites (Figure 5). Thus, the observed variationsin composition of the amphibolite P6 are probably notrelated to protolith heterogeneity, but rather should be theresult of geochemical modification during

Figure 6. Plot of the initial Sr-Nd for the investigated gneissand amphibolite at t1 = 780 Ma (a) and t2 = 230 Ma (b),respectively. MORB and OIB data are from Stracke et al.(2003) and recalculated back to 780 Ma and 230 Ma,respectively.

Figure 7. Profile of whole-rock oxygen isotope across theboundary of different lithologies. The dash–dot line denotes theboundary between the granitic gneiss and amphibolite. Error barsrepresent two standard deviations.

1114 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

metamorphism. This is also supported by a significantvariation in initial 87Sr/86Sr ratios from 0.7004 to 0.7056at t = 780 Ma (protolith age), but a very limited range ofinitial 87Sr/86Sr ratios from 0.7061 to 0.7070 att = 230 Ma (metamorphism age, Figure 6). This alsoargues for compositional modification that resulted in asecondary homogenization of the Rb-Sr isotopic systemduring metamorphism.

If geochemical modification took place during TriassicUHP metamorphism, then element mobility should occurat prograde and/or retrograde stages of metamorphism inassociation with aqueous fluids, hydrous melts, and/orsupercritical liquids during subduction and exhumationof the continental crust (e.g. Zheng 2009; Zhang et al.2011; Zheng et al. 2011b and references therein). In thisregard, it is critical to discriminate which kind of agent is

responsible for the observed compositional variations atthe described lithological contact.

6.2. Aqueous fluids

Aqueous fluids cannot be the metasomatic agent causingthe observed geochemical variations at the contactbetween the granitic gneiss and amphibolite. This isbecause aqueous fluids released during metamorphic dehy-dration are surprisingly dilute with low concentrations oftotal dissolved solutes (TDS) (Hermann et al. 2006), andthey only contain the TDS of ≤5.5–17 wt.% at P ≤ 2.2–5.0 GPa and T ~600–800°C (Manning 2004; Kessel et al.2005b; Spandler et al. 2007; Hermann and Spandler2008). Considering the peak metamorphic conditions ofthe SDZ (~3.3 GPa and ~670°C, Li et al. 2004) and the

Figure 8. The P-T evolution of the South Dabie UHP metamorphic rocks and the positions of the second critical endpoints in thesystems granite + H2O and basalt + H2O. The P-T path of the South Dabie low-T/UHP rocks is revised after Li et al. (2004) and Xia et al.(2010). Wet solidus for the system granite-H2O is after Huang and Wyllie (1981), and that for the system basalt-H2O is after Mibe et al.(2011). The position of the second critical endpoint in the system granite + H2O is after Hermann et al. (2006) and that in the systembasalt + H2O is after Mibe et al. (2011). The critical curve for the system granite + H2O was experimently determined by Bureau andKeppler (1999). The curves (1), (2), and (3) (dashed lines) for phengite dehydration melting are taken from Auzanneau et al. (2006),Vielzeuf and Holloway (1988), and Hermann (2002), respectively. Phg (X, Y) denotes phengite (SiO2, Na2O/K2O) that is indicative ofdifferent compositions of starting materials. Although by following the lines (1) and (2), phengite dehydration melting was supposed totake place at high P-T conditions (e.g. point C) and low P-T conditions (point D), no evidence for dehydration melting was found inmetamorphic rocks from the northern part of the SDZ (Xia et al. 2010; this study). U-shaped red and blue lines represent the field foroccurrence of supercritical liquids in the felsic- and basaltic rock–H2O systems, respectively. Under UHP conditions (e.g. path A→B) inthe SDZ, a supercritical liquid is likely to be present in the granitic gneiss and would then separate into two liquid phases (hydrous meltand aqueous fluid) in response to decompression during exhumation of the deeply subducted continental crust.

International Geology Review 1115

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

general topology of element solubility isopleths (Hacket al. 2007), the estimated maximum TDS in the aqueousfluids should be less than ~8 wt.%. Such low TDS con-tents could not cause the significant increase in K2O(~240%), Al2O3 (~20%), and TiO2 (~20%) at the amphi-bolite P6 (Figure 5).

There is also a clear indication that significant trans-port of major and trace elements by such aqueous fluids isunlikely (e.g. Hermann et al. 2006; Spandler et al. 2007).Element mobility might be significantly enhanced bychannelized fluid flow with very high fluid/rock ratios(e.g. Ague 2003; John et al. 2004, 2008; Hermann et al.2006; Penniston-Dorland et al. 2008; Spandler et al.2011), or processes at the slab–wedge interface (e.g.Bebout 2007). In the present study, no veins were foundin the outcrop where the samples were collected, suggest-ing that very high fluid/rock ratios are not expected fortransporting fluid-immobile elements (i.e. HFSEs andHREEs). Limited fluid activity during UHP metamorph-ism has been evidenced by heterogeneous structural OHcontents of UHP eclogite-facies minerals (e.g. garnet,omphacite, kyanite, and rutile) from the Dabie orogenand the occurrence of highly variable salinity inclusionsin these minerals (Xiao et al. 2000, 2006b; Xia et al. 2005;Sheng et al. 2007). Additional arguments arise fromhighly variable and anomalously low δ18O values of–11‰ to –2‰ for zircon and other minerals from theDabie–Sulu UHP eclogites and their associated gneiss(e.g. Yui et al. 1995; Zheng et al. 1996, 2004; Rumbleet al. 2003), which have been interpreted as havingresulted from high-T meteoric-hydrothermal alterationduring the emplacement of their igneous protolith undercold climatic conditions in the Neoproterozoic. 18O-deple-tion is also observed in eclogite and gneiss from the SDZ,with garnet δ18O values of –6.3‰ to 6.0‰ (Zheng et al.1999, 2007; Li et al. 2004; Xia et al. 2008). The gneissand amphibolite investigated here also have low δ18Ovalues (0.59 ~ 1.29‰ in gneiss; –2.21 ~ –1.66‰ inamphibolite, Figure 7), which is typical for the Dabie–Sulu UHP metamorphic rocks but much less than those innormal metamorphic rocks (with bulk δ18O > 5.6‰, Hoefs2009). The preservation of these unusual signatures andtheir heterogeneities over small spatial distances (metres)again argues for limited fluid activity during metamorphicprocesses, which would have erased these differences.This observation also reinforces the case that the UHPcomplex, comprising eclogite and gneiss, represents asubducted and exhumed coherent slab during continentalcollision (e.g. Xiao et al. 2006b; Zhao et al. 2007b).

In contrast to the UHP peak conditions, a relativelyhigher fluid activity may be derived from the decomposi-tion of hydrous minerals and the exsolution of structuralhydroxyl and molecular water from nominally anhydrousminerals in response to a profound decrease in pressureduring exhumation (e.g. Zheng et al. 2003; Zheng 2009).

This is suggested to be responsible for syn-exhumationmagmatism, quartz veining, and widespread amphibolite-facies retrogression in the Dabie–Sulu orogenic belt (e.g.Zheng et al. 2011b). In this study, complete retrogressionof eclogite to amphibolite, partial retrogression of garnetto amphibole (and/or plagioclase) and rutile to titanite(and/or ilmenite), and abundant symplectite after clino-pyroxene also show relatively high fluid activity duringexhumation of the deeply subducted continental crust(Figure 3(b)–(d)). As shown in Figure 7, the graniticgneiss displays a slight decrease, while the amphibolitehas a progressive increase in δ18O values towards itslithological boundary, indicating the occurrence of fluid-assisted O-isotope exchange across the contacts of differ-ent lithologies at local scales during amphibolite-faciesretrogression (Zhao et al. 2007b). This also suggests thatfluids for retrogression of eclogite at the point of contactlargely came from the gneiss and that the contact betweendifferent lithologies is the most favourable site for fluidactivity (Chen et al. 2007b). Although this amphibolite-facies retrogression could result in mineral O-isotopedisequilibria between some minerals (e.g. Zheng et al.1999; Xiao et al. 2006b), it gives rise to no significantchange in trace element compositions of bulk rocks (Sassiet al. 2000; Zhao et al. 2007a). The rims of a phengiticmuscovite in this study have higher Ba contents thancores (Figure A2), indicating that the retrograded aqueousfluids are enriched in Ba. Thus, such aqueous fluids maypartly account for the increase of Ba in the amphiboliteP6 (Figure 5). However, complete re-equilibration of theRb-Sr system occurred under peak metamorphic condi-tions at ~230 Ma (Figure 6) and was preserved duringsubsequent exhumation. This is indicative of no distur-bance and redistribution of Rb and Sr during amphibolite-facies retrogression. In addition, petrographical observa-tions indicate that the amphibolite P6 was subject to almostthe same intensity of retrogression (represented by the totalabundance of amphibole + symplectite, Table 1) as theother four amphibolites, but the former has consistentlyhigher concentrations of LILEs (e.g. Rb, Ba, K), REEs,and HFSEs (e.g. Nb) (Figures 4 and 5). All these resultsindicate that amphibolite-facies retrogression is unlikely toresult in significant mobility of trace elements and toexplain the large variations in K2O (~240%), Al2O3

(~20%), TiO2 (~20%), LILEs, and especially HFSEs andHREEs of the amphibolite P6 at the contact (Figure 5 andTable 2). Therefore, the aqueous fluids released duringmetamorphic dehydration and amphibolite-facies retrogres-sion cannot significantly modify the element compositionsof the UHP metamorphic rocks.

6.3. Hydrous melts

Hydrous melts produced by dehydration melting ofphengite in the Dabie–Sulu UHP metamorphic felsic

1116 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

and mafic rocks during exhumation have been widelyidentified (e.g. Wallis et al. 2005; Zhao et al. 2007a;Xia et al. 2008; Zheng et al. 2011b; Gao et al. 2012,2013). Experimental results show that such melts havea much greater capacity to carry and transport traceelements than aqueous fluids (e.g. Kessel et al. 2005a;Spandler et al. 2007; Hermann and Rubatto 2009).Thus, hydrous melts could have significantly increasedLILE, LREE, and HFSE contents in the amphibolite P6adjacent to the boundary to the gneiss (Figure 5). Tofurther test this hypothesis, we need to consider thecompositions of the gneisses. Xia et al. (2008) identi-fied two types of gneisses (Group I and Group II) inthe SDZ. Group II gneisses are thought to have experi-enced dehydration melting due to the breakdown ofphengitic muscovite during ‘hot’ exhumation withoutconsiderable escape of felsic melts from the hostgneiss, while Group I gneisses only suffered frommetamorphic dehydration (Xia et al. 2008). Group IIgneiss has extremely low contents ofFeO + MgO + TiO2 (1.04–2.08 wt.%), high SiO2

contents of 75.3–78.2 wt.%, high total alkali(Na2O + K2O) contents (7.52–8.92 wt.%), and veryhigh 87Sr/86Sr ratios of 0.7441–1.148. Gneisses studiedhere are similar to Group I gneisses, they have rela-tively higher contents of FeO + MgO + TiO2 (4.29–6.37 wt.%), and are much lower in SiO2 (65.6–72.6 wt.%), Na2O + K2O (5.62–7.62 wt.%), and 87Sr/86Sr ratios (0.7068–0.7096) relative to Group IIgneisses (Tables 2 and 3). All these features suggestthat the gneisses investigated in this study would havenot been subjected to dehydration melting during con-tinental collision and exhumation.

Meanwhile, experimental studies on felsic rocks in therange 1.5–5.0 GPa and 750–1050°C have shown thathydrous melts have high contents of SiO2 (69.5–76.8 wt.%) and Na2O + K2O (6.25–12.3 wt.%) but lowcontents of FeO (0.48–2.51 wt.%), MgO (0.19–1.1 wt.%),and CaO (0.27–2.51 wt.%) (Huang and Wyllie 1981;Patiño Douce 2005; Auzanneau et al. 2006; Spandleret al. 2007; Hermann and Spandler 2008; Hermann andRubatto 2009). Metasomatism of mafic rocks (e.g. eclogiteor amphibolite) by such hydrous melts would give rise toincreases in SiO2 and total alkali contents but decreases inFeO, MgO, and CaO contents. However, these features arenot observed for the amphibolite P6 at the contact (Table 2and Figure 5). This again suggests that amphibolite P6 didnot suffer from the overprint of hydrous melts.

Therefore, based on arguments discussed above, thelarge variations in composition of the amphibolite P6 atthe contact can be related to neither protolith heterogeneitynor metasomatism of aqueous fluids and hydrous melts.This demands an alternative process and a different fluidagent to explain the observed major and trace elementvariations.

6.4. Supercritical liquids

Important to understanding the role of fluid phases inmetamorphic rocks is the recognition of a second criticalendpoint (defined as the intersection between the wetsolidus and critical curve, Boettcher and Wyllie 1969) athigh pressure in the silicate–H2O system. At pressureshigher than that of the second critical endpoint, aqueousfluids and hydrous melts become completely miscible andconverge into one single phase known as supercriticalliquids (e.g. Bureau and Keppler 1999; Manning 2004;Hermann et al. 2006). It has been experimentally recog-nized that supercritical liquids have a much higher capa-city than aqueous fluids and hydrous melts to dissolvevarious types of solutes, including silicates and conven-tionally fluid-immobile elements such as HFSEs andHREEs (e.g. Kessel et al. 2005a; Hayden and Manning2011). The presence of supercritical liquids has beenrecognized in natural felsic and mafic rock systemsunder crustal and mantle conditions (Zheng et al. 2011band references therein). Geochemical analyses of coesite-bearing hydrous veins derived from dehydration of theirsurrounding UHP eclogites in the South Sulu UHP zonesuggest that the vein-forming fluids are not only rich inLREEs and LILEs, but also have high concentrations ofnominally immobile elements such as HREEs and HFSEs(Zhang et al. 2008). The minerals in these veins wereinterpreted as having crystallized from a supercriticalliquid that formed during peak UHP metamorphism.Therefore, the existence and transport capacity of super-critical liquids must be taken into account in the study ofUHP metamorphic rocks.

Experimental results show that the second critical end-point is situated at ~2.6 GPa and ~700°C in the granite–H2O system but at ~3.4–5.5 GPa and ~800–1000°C in thebasalt–H2O system (Kessel et al. 2005b; Hermann et al.2006; Mibe et al. 2011). Thus, a contrasting behaviour offluid supercriticality is expected to occur for the differentlithologies. Figure 8 delineates the P-T path representativeof the UHP lithological units in the SDZ. Also shown areexperimental data available for the wet solidi and the posi-tions of the second critical endpoints in the granite–H2Oand basalt–H2O systems. For the low-T/UHP metamorphicrocks in the SDZ, the P-T regime falls in the P-T region forsupercriticality of a fluid phase in the granite–H2O systemin the stability of coesite, but is beyond the P-T region forfluid supercriticality in the basalt–H2O system (Figure 8).This suggests that under UHP conditions, the supercriticalliquids would readily form in the granitic gneisses (e.g.path A→B, Figure 8), but were unlikely to be present inthe eclogites. The granitic gneiss-derived supercriticalliquids might have metasomatized the adjacent eclogiteunder UHP conditions and resulted in the observed geo-chemical variations in the amphibolite P6 at the contact(Figure 5). This is also evidently reflected by the trace

International Geology Review 1117

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

element distribution patterns (especially negative P anom-aly) of the amphibolite P6, which is similar to those ofgranitic gneiss (Figure 4(d)).

During ‘hot’ exhumation, the P-T regime will fallbelow the second critical endpoint during decompressionfrom mantle depths to lower crustal levels (Figure 8), andthus the supercritical liquids will separate into two immis-cible liquid phases (an aqueous fluid and a hydrous melt).MS inclusions ofK-feldspar + quartz + calcite + zircon±gar-net ± apatite ± amphibole ± clinozoisite (Figures 3(e) and(f)) are likely to have crystallized from the pre-existingsupercritical fluids as the pressure decreased (Hermannet al. 2006). As zircon is enriched in Zr and Hf, garnetin HREEs and Y, apatite in REEs and P, and amphibole inMREEs (Hermann 2002; Liang et al. 2009), the occur-rence of REE-HFSE-rich mineral inclusions in garnet maybe a mineralogical record of exsolving the very high con-centrations of trace elements from the pre-existing super-critical liquids during the decompression exhumation (Xiaet al. 2010). The phase separation of supercritical liquidshas been advocated to explain the local occurrence offelsic veinlets between coarse-grained metamorphic miner-als and epidote + titanite + zircon aggregations in theSouth Dabie low-T/UHP granitic gneisses (Xia et al.2010). Another hint for the garnet-hosted mineral inclusionsprecipitating from supercritical liquids is their estimated bulkcompositions. They have highly variable contents of FeO(0.31‒8.07 wt.%), MgO (0.03‒7.78 wt.%), K2O (3.02‒7.81 wt.%), and Na2O (0.08‒1.53wt.%) (Table A3). It isunlikely that these compositions represent hydrous melts,because calculated compositions are unrealistic for silicatemelts. Complex brines with varying amounts of elementshave been advocated to explain inclusions with differentsolid phases + a fluid (e.g. Philippot and Selverstone 1991;Svensen et al. 2001). However, high SiO2 and Al2O3 (up to13.3 wt.%, Table A3) rule out this explaination, since noaqueous fluid is able to dissolve such high levels of silica oralumina (e.g. Ferrando et al. 2005). Therefore, we interprettheMS inclusions in garnet as direct textural evidence for thepresence of a supercritical liquid in the UHP metamorphicrocks. Similar MS inclusions have been related to super-critical liquids at other localities in the Dabie–Sulu orogenicbelt (Ferrando et al. 2005; Frezzotti et al. 2007; Zhang et al.2008; Gao et al. 2012).

Theoretically, before phase separation at pressure abovethe second critical endpoint in the rock–H2O system, therock may coexist with a single supercritical liquid that canvary continuously in composition from dilute aqueous tosilicate melt-like fluids (see Figure 4(c), Ferrando et al.2005). Results obtained from experiments and studies ofnatural rocks also show that supercritical liquids have widecompositional variations and that the total dissolved solutesin such liquids vary highly, ranging from 18.4 to 89.3 wt.%(Ferrando et al. 2005; Kessel et al. 2005b; Zhang et al.2008). For example, on the basis of a detailed petrological

observation and chemical data of minerals in UHP hydrousveins within eclogites from the South Sulu UHP zone,Zhang et al. (2008) suggested that the supercritical liquidscomprise mainly SiO2 (up to 70 wt.%) + Al2O3 (up to13 wt.%) + CaO (~3 wt.%) + H2O (~30–70 wt.%) withvarying amounts of MgO, FeO, Na2O, CO2 and SO4,whereas based on geochemical analyses of primary MSinclusions in kyanite and garnet, the calculated averagecompositions of the supercritical liquids are 24–26 wt.%SiO2, ~1–21 wt.% TiO2, 20–30 wt.% Al2O3, ~1–9 wt.%FeOtotal, ~1–2 wt.% MgO, 7–9 wt.% CaO, ~3 wt.% Na2O,~1–5 wt.% K2O, ~1–2 wt.% P2O5, and ~7–18 wt.% H2O,with traces of BaO, ZnO, MnO, Cl, and F (Ferrando et al.2005). Our estimated bulk compositions of the representa-tive MS inclusions in this study (Table A3) cannot, how-ever, be exactly representative of the chemical nature of theoriginal supercritical liquids. Apart from uncertainties incalculation, such liquids will interact to different degreeswith the surrounding minerals at a local scale, and alsobecause the minerals in the MS inclusions might precipitatefrom a reactive mobile fluid.

It has been argued above that enrichment in LILEs,REEs, HFSEs, Th, and U in the amphibolite P6 at thecontact with gneiss is not attributed to protolith heteroge-neity, nor the overprint by aqueous fluids or hydrousmelts. Thus, supercritical liquids are likely to explain theobserved chemical and isotopic changes. An importantsource for mobilization of these trace elements is thedecomposition of accessory mineral phases. It is widelyaccepted that phengite is the major host for LILEs, allanitefor LREEs, Th, and U, garnet for HREEs, rutile for Ti, Nb,and Ta, and zircon for Zr and Hf (e.g. Hermann 2002;Spandler et al. 2003). Supercritical liquids that occurred inthe granitic gneiss may have completely or partly dis-solved these accessary minerals and are thus enriched inLILEs, REEs, HFSEs, Th, and U. This may explain theabsence of allanite in the granitic gneiss. Therefore, meta-somatism of such supercritical liquids could lead to theobserved geochemical variations at the contact.

7. Conclusions

Our study of petrology, mineral chemistry, major and traceelements, and Sr-Nd-O isotopes in UHP eclogite (retro-gressed to amphibolite) and gneiss from the SDZ hasshown that supercritical liquids may have been involvedin explaining the observed element mobility. Considerablechanges in δ18O values and concentrations of major andtrace elements at the contact between felsic and maficrocks suggest that the contact between different lithologiesis the most favourable place for fluid activity, consistentwith the studies of Xiao et al. (2006b), Chen et al.(2007b), and Zhao et al. (2007b). Petrological and geo-chemical results indicate the occurrence of a supercriticalliquid at the boundary between felsic and mafic rocks from

1118 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

the SDZ. In comparison of experimentally determined P-Tregions for liquid supercriticality in the felsic- and mafic-rock–H2O systems with the P-T path for the South Dabielow-T/UHP metamorphic rocks, we suggest that the super-critical liquids formed at the peak UHP metamorphicconditions in the granitic gneiss and subsequently metaso-matized the adjacent eclogite, causing an increase in majorand trace element concentrations at the contact. The super-critical liquids may separate into two liquid phases: ahydrous melt and an aqueous fluid at decreasing pressureduring initial ‘hot’ exhumation of the deeply subductedcontinental crust.

AcknowledgementsWe are grateful to Drs J. Hermann, S. Penniston-Dorland, andG. Wörner, Z.-M. Zhang, and two anonymous reviewers for theirsuggestions and comments that greatly helped improvement ofthe presentation. Thanks are due to A. Kronz for helping withdetermination of mineral major element concentrations by EMP.R. Przybilla, J.-H. He, and P. Xiao are thanked for assistanceduring whole-rock O-Sr-Nd isotope analyses.

FundingThis work was financially supported by grants from the NaturalScience Foundation of China [41090372], [41303015], [41172067],[41273037]; and the Hundred Talent Program me from CAS. J.Huang is partly supported by the China Scholarship Council.

ReferencesAgue, J.J., 2003, Fluid infiltration and transport of major, minor,

and trace elements during regional metamorphism of carbo-nate rocks, Wepawaug schist, Connecticut, USA: AmericanJournal of Science, v. 303, p. 753‒816.

Auzanneau, E., Vielzeuf, D., and Schmidt, M.W., 2006,Experimental evidence of decompression melting duringexhumation of subducted continental crust: Contributions toMineralogy and Petrology, v. 152, p. 125‒148.

Bebout, G., 2007, Metamorphic chemical geodynamics of sub-duction zones: Earth and Planetary Science Letters, v. 260, p.373‒393.

Becker, H., Jochum, K.P., and Carlson, R.W., 2000, Trace ele-ment fractionation during dehydration of eclogites fromhigh-pressure terranes and the implications for elementfluxes in subduction zones: Chemical Geology, v. 163, p.65‒99.

Boettcher, A.L., and Wyllie, P.J., 1969, The system CaO-SiO2-CO2-H2O–III. Second critical end-point on the melting curve:Geochimica et Cosmochimica Acta, v. 33, p. 611‒632.

Bureau, H., and Keppler, H., 1999, Complete miscibility betweensilicate melts and hydrous fluids in the upper mantle, experi-mental evidence and geochemical implications: Earth andPlanetary Science Letters, v. 165, p. 187‒196.

Carswell, D.A., O’Brien, P.J., Wilson, R.N., and Zhai, M.G.,1997, Thermobarometry of phengite-bearing eclogites inthe Dabie Mountains of central China: Journal ofMetamorphic Geology, v. 15, p. 239‒252.

Carswell, D.A., and Zhang, R.Y., 1999, Petrographic character-istic and metamorphic evolution of ultrahigh-pressure

eclogites in plate-collision belts: International GeologyReview, v. 41, p. 871‒889.

Castelli, D., Rolfo, F., Compagnoni, R., and Xu, S.T., 1998,Metamorphic veins with kyanite, zoisite and quartz in theZhu-Jia-Chong eclogite, Dabie Shan, China: The Island Arc,v. 7, p. 159‒173.

Chen, J.F., Zheng, Y.F., Zhao, Z.F., Li, B., Xie, Z., Gong, B., andQian, H., 2007a, Relationships between O isotope equili-brium, mineral alteration and Rb–Sr chronometric validityin granitoids: Implications for determination of cooling rate:Contributions to Mineralogy and Petrology, v. 153, p. 251‒271.

Chen, R.X., Zheng, Y.F., Gong, B., Zhao, Z.F., Gao, T.S., Chen,B., and Wu, Y.B., 2007b, Oxygen isotope geochemistry ofultrahigh-pressure metamorphic rocks from 200–4000 mcore samples of the Chinese Continental Scientific Drilling:Chemical Geology, v. 242, p. 51‒75.

Davies, J.H., 1999, The role of hydraulicfractures and intermedi-ate-depth earthquakes in generating subduction-zone mag-matism: Nature, v. 398, p. 142‒145.

Deer, W., Howie, R.A., and Zussman, J., 1992, An introductionot the rock-forming minerals (second edition): London,Longman.

DePaolo, D.J., 1988, Neodymium isotope geochemistry: Anintroduction: New York, Springer-Verlag, 181 p.

Ferrando, S., Frezzotti, M.L., Dallai, L., and Compagnoni, R.,2005, Multiphase solid inclusions in UHP rocks (Su-Lu,China): Remnants of supercritical silicate-rich aqueous fluidsreleased during continental seduction: Chemical Geology, v.223, p. 68‒81.

Franz, L., Romer, R.L., Klemd, R., Schmid, R., Oberhansli, R.,Wagner, T., and Dong, S.W., 2001, Eclogite-facies quartzveins within metabasites of the Dabie Shan (eastern China):Pressure-temperature-time-deformation path, composition ofthe fluid phase and fluid flow during exhumation of high-pressure rocks: Contributions to Mineralogy and Petrology,v. 141, p. 322‒346.

Frezzotti, M.L., Ferrando, S., Dallai, L., and Compagnoni, R.,2007, Intermediate alkali-alumino-silicate aqueous solutionsreleased by deeply subducted continental crust: Fluid evolu-tion in UHP OH-rich topaz-kyanite quartzites from Donghai(Sulu, China): Journal of Petrology, v. 48, p. 1219‒1241.

Fu, B., Touret, J.L.R., Zheng, Y.F., and Jahn, B.M., 2003, Fluidinclusions in granulites, granulitized eclogites and garnetclinopyroxenites from the Dabie-Sulu terranes, easternChina: Lithos, v. 70, p. 293‒319.

Gao, J., John, T., Klemd, R., and Xiong, X.M., 2007,Mobilization of Ti-Nb-Ta during subduction: Evidencefrom rutile-bearing dehydration segregations and veinshosted in eclogite, Tianshan, NW China: Geochimica etCosmochimica Acta, v. 71, p. 4974‒4996.

Gao, X.Y., Zheng, Y.F., and Chen, Y.X., 2012, Dehydrationmelting of ultrahigh-pressure eclogite in the Dabie orogen:Evidence from multiphase solid inclusions in garnet: Journalof Metamorphic Geology, v. 30, p. 193‒212.

Gao, X.Y., Zheng, Y.F., Chen, Y.X., and Hu, Z.C., 2013, Traceelement composition of continentally subducted slab-derivedmelt: Insight from multiphase solid inclusions in ultrahigh-pressure eclogite in the Dabie orogeny: Journal ofMetamorphic Geology, v. 31, p. 453‒468.

Guo, S., Ye, K., Chen, Y., Liu, J.B., Mao, Q., and Ma, Y.G.,2012, Fluid-rock interaction and element mobilization inUHP metabasalt: Constraints from an omphacite-epidotevein and host eclogites in the Dabie orogeny: Lithos, v.136‒139, p. 145‒167.

International Geology Review 1119

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Hack, A.C., Thompson, A.B., and Aerts, M., 2007, Phase relationsinvolving hydrous silicate melts, aqueous fluids, and minerals:Reviews in Mineralogy and Geochemistry, v. 65, p. 129‒185.

Hayden, L.A., and Manning, C.E., 2011, Rutile solubility insupercritical NaAlSi3O8-H2O fluids: Chemical Geology, v.284, p. 74‒81.

Hermann, J., 2002, Experimental constraints on phase relationsin subducted continental crust: Contributions to Mineralogyand Petrology, v. 143, p. 219‒235.

Hermann, J., and Rubatto, D., 2009, Accessory phase control onthe trace element signature of sediment melts in subductionzones: Chemical Geology, v. 265, p. 512‒526.

Hermann, J., Spandler, C., Hack, A., and Korsakov, A.V., 2006,Aqueous fluids and hydrous melts in high-pressure and ultra-high pressure rocks: Implications for element transfer insubduction zones: Lithos, v. 92, p. 399‒417.

Hermann, J., and Spandler, C.J., 2008, Sediment melts at sub-arcdepths: An experimental study: Journal of Petrology, v. 49, p.717‒740.

Hoefs, J., 2009, Stable isotope geochemistry (6th edition): BerlinHeidelberg New York, Springer, 291 p.

Hou, Z.H., and Wang, C.Z., 2007, Determination of 35 traceelements in geological samples by inductively coupledplasma mass spectrometry: Journal of University of Scienceand Technology of China (in Chinese with English Abstract),v. 37, p. 940‒944.

Huang, J., Xiao, Y.L., Gao, Y.J., Hou, Z.H., and Wu, W.P., 2012,Nb–Ta fractionation induced by fluid-rock interaction insubduction-zones: Constraints from UHP eclogite- andvein-hosted rutile from the Dabie orogen, Central-EasternChina: Journal of Metamorphic Geology, v. 30, p. 821‒842.

Huang, J., Zheng, Y.-F., Zhao, Z.-F., Wu, Y.-B., Zhou, J.-B., andLiu, X.M., 2006, Melting of subducted continent: Elementand isotopic evidence for a genetic relationship betweenNeoproterozoic and Mesozoic granitoids in the Sulu oro-geny: Chemical Geology, v. 229, 227–256. doi:10.1016/j.chemgeo.2005.11.007

Huang, W.L., and Wyllie, P.J., 1981, Phase relationships of S-type granite with H2O to 35 kbar: Muscovite granite fromHarney Peak, South Dakota: Journal of GeophysicalResearch, v. 86, p. 10515‒10529.

Hwang, S.L., Shen, P., Chu, H.T., Yui, T.F., and Lin, C.C., 2001,Genesis of microdiamonds from melt and associated multi-phase inclusions in garnet of ultrahigh-pressure gneiss fromErzgebirge, Germany: Earth and Planetary Science Letters, v.188, p. 9–15. doi:10.1016/S0012-821X(01)00314-4

Jahn, B.M., and Condie, K.C., 1995, Evolution of the KaapvaalCraton as viewed from geochemical and Sm–Nd isotopicanalyses of intracratonic pelites: Geochimica etCosmochimica Acta, v. 59, p. 2239‒2258.

Jahn, B.M., Rumble, D., and Liou, J.G., 2003, Geochemistry andisotope tracer study of UHP metamorphic rocks, in:Carswell, D.A., and Compagnoni, R., eds., Ultrahigh pres-sure metamorphism: European Mineralogical Union Notes inMineralogy, v. 5, p. 365‒414.

Jochum, K.P., and Nehring, F., 2006, BHVO-2 and AGV-2:GeoReM preferred values: GeoReM. http://georem.mpch-mainz.gwdg.de/ (accessed 1 November 2013).

John, T., Klemd, R., Gao, J., and Garbe-Schönberg, C.D., 2008,Trace-element mobilization in slabs due to non steady-statefluid-rock interaction: Constraints from an eclogite-faciestransport vein in blueschist (Tianshan, China): Lithos, v.103, p. 1‒24.

John, T., Scherer, E.E., Haase, K., and Schenk, V., 2004, Traceelement fractionation during fluid-induced eclogitization in a

subducting slab: Trace element and Lu-Hf-Sm-Nd isotopesystematics: Earth and Planetary Science Letters, v. 227, p.441‒456.

Kessel, R., Schmidt, M.W., Ulmer, P., and Pettke, T., 2005a,Trace element signature of subduction-zone fluids, meltsand supercritical liquids at 120–180 km depth: Nature, v.437, p. 724‒727.

Kessel, R., Ulmer, P., Pettke, T., Schmidt, M.W., and Thompson,A.B., 2005b, The water-basalt system at 4 to 6 GPa: Phaserelations and second critical endpoint in a K-free eclogite at700 to 1400°C: Earth and Planetary Science Letters, v. 237,p. 873‒892.

Kogiso, T., Tatsumi, Y., and Nakano, S., 1997, Trace elementtransport during dehydration processes in the subductedoceanic crust: 1. Experiments and implications for the originof ocean island basalts: Earth and Planetary Science Letters,v. 148, p. 193‒205.

Leake, B.E., Woolley, A.R., Arps, C.E.S., Birch, W.D., Gilbert, M.C., Grice, J.D., Hawthorne, F.C., Kato, A., Kisch, H.J.,Krivovichev, V.G., Linthout, K., Laird, J., Mandarino, J.,Maresch, W.V., Nickel, E.H., Rock, N.M.S., Schumacher, J.C.,Smith, D.C., Stephenson, N.C.N., Ungaretti, L., Whittaker, E.J.W., and Youzhi, G., 1997, Nomenclature of amphiboles; reportof the subcommittee on amphiboles of the international miner-alogical association commission on new minerals and mineralnames: Mineralogical Magazine, v. 61, p. 295‒321.

Li, S.G., Jagoutz, E., Lo, C.H., Chen, Y.Z., Li, Q.L., and Xiao,Y.L., 1999, Sm/Nd, Rb/Sr, and 40Ar/39Ar isotopic systema-tics of the ultrahigh-pressure metamorphic rocks in theDabie-Sulu Belt, Central China: A retrospective view:International Geology Review, v. 41, p. 1114–1124.doi:10.1080/00206819909465195

Li, X.P., Zheng, Y.F., Wu, Y.B., Chen, F.K., Gong, B., and Li,Y.L., 2004, Low-T eclogite in the Dabie terrane of China:Petrological and isotopic constraints on fluid activity andradiometric dating: Contributions to Mineralogy andPetrology, v. 148, p. 443‒470.

Liang, J.L., Ding, X., Sun, X.M., Zhang, Z.M., Zhang, H., andSun, W.D., 2009, Nb/Ta fractionation observed in eclogitesfrom the Chinese continental scientific drilling project:Chemical Geology, v. 268, p. 27–40. doi:10.1016/j.chemgeo.2009.07.006

Liou, J.G., Zhang, R.Y., Ernst, W.G., Rumble, D., andMaruyama, S., 1998, High-pressure minerals from deeplysubducted metamorphic rocks: Reviews in Mineralogy andGeochemistry, v. 37, p. 33‒96.

Liu, F.L., and Liou, J.G., 2011, Zircon as the best mineral for P-T-time history of UHP metamorphism: A review on mineralinclusions and U-Pb SHRIMP ages of zircons from theDabie-Sulu UHP rocks: Journal of Asian Earth Sciences, v.40, p. 1‒39.

Liu, F.L., Robinson, P.T., Gerdes, A., Xue, H.M., Liu, P.H., andLiou, J.G., 2010, Zircon U-Pb ages, REE concentrations andHf isotope compositions of granitic leucosome and pegmatitefrom the north Sulu UHP terrane in China: Constraints on thetiming and nature of partial melting: Lithos, v. 117, p. 247‒268.

Liu, J.B., Ye, K., Maruyama, S.N., Cong, B.L., and Fan, H.R.,2001, Mineral inclusions in zircon from gneisses in theultrahigh-pressure zone of the Dabie Mountains, China:Journal of Geology, v. 109, p. 523‒535.

Manning, C.E., 2004, The chemistry of subduction-zone fluids:Earth and Planetary Science Letters, v. 223, p. 1‒16.

McCulloch, M.T., and Gamble, J.A., 1991, Geochemical andgeodynamical constraints on subduction zone magmatism:Earth and Planetary Science Letters, v. 102, p. 358‒374.

1120 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Mibe, K., Kawamoto, T., Matsukage, K.N., Fei, Y., and Ono, S.,2011, Slab melting versus slab dehydration in subduction-zonemagmatism: Proceedings of the National Academy ofSciences, v. 108, p. 8177–8182. doi:10.1073/pnas.1010968108

Miller, C., Zanetti, A., Thöni, M., and Konzett, J., 2007,Eclogitisation of gabbroic rocks: Redistribution of trace ele-ments and Zr in rutile thermometry in an Eo-Alpine subductionzone (Eastern Alps): Chemical Geology, v. 239, p. 96‒123.

Navon, O., Hutcheon, I.D., Rossman, G.R., and Wasserburg,G.J., 1988, Mantle-drived fluids in diamond micro-inclu-sions: Nature, v. 335, p. 784‒789.

Niu, Y., 2005, Generation and evolution of basaltic magmas:Some basic concepts and a new view on the origin ofMesozoic-Cenozoic basaltic volcanism in Eastern China:Geological Journal of China Universities, v. 11, p. 9‒46.

Oberti, R., Smith, D.C., Rossi, G., and Caucia, F., 1991, Thecrystal-chemistry of high-aluminium titanites: EuropeanJournal of Mineralogy, v. 3, p. 777‒792.

Okay, A.I., Xu, S.T., and Sengor, A.M.C., 1989, Coesite from theDabie Shan eclogites, central China: European Journal ofMineralogy, v. 1, p. 595‒598.

Patiño Douce, A.E., 2005, Vapor-Absent melting of Tonalite at15–32 kbar: Journal of Petrology, v. 46, p. 275‒290.

Penniston-Dorland, S.C., and Ferry, J.M., 2008, Element mobi-lity and scale of mass transport in the formation of quartzveins during regional metamorphism of the Waits RiverFormation, east-central Vermont: American Mineralogist, v.93, p. 7–21. doi:10.2138/am.2008.2461

Philippot, P., and Selverstone, J., 1991, Trace-element-rich brinesin eclogitic veins: Implications for fluid composition andtransport during seduction: Contributions to Mineralogyand Petrology, v. 106, p. 417‒430.

Roddick, J.C., Sullivan, R.W., and Dudás, F.Ö., 1992, Precisecalibration of Nd tracer isotopic compositions for Sm/1bNdstudies: Chemical Geology, v. 97, p. 1–8. doi:10.1016/0009-2541(92)90132-O

Rudnick, R.L., and Gao, S., 2003, Composition of the continen-tal crust: Treatise on Geochemistry, v. 3, p. 1–64.doi:10.1016/B0-08-043751-6/03016-4

Rumble, D., Liou, J.G., and Jahn, B.M., 2003, Continental crustsubduction and ultrahigh pressure metamorphism: Treatiseon Geochemistry, v. 3, p. 293–319. doi:10.1016/B0-08-043751-6/03158-3

Sassi, R., Harte, B., Carswell, D.A., and Yu, J.H., 2000, Traceelement distribution in Central Dabie eclogites:Contributions to Mineralogy and Petrology, v. 139, p. 298‒315.

Sheng, Y.M., Xia, Q.K., Dallai, L., Yang, X.Z., and Hao, Y.T.,2007, H2O contents and D/H ratios of nominally anhydrousminerals from ultrahigh-pressure eclogites of the Dabie oro-gen, eastern China: Geochimica et Cosmochimica Acta, v.71, p. 2079‒2103.

Sheng, Y.M., Zheng, Y.F., Chen, R.X., Li, Q.L., and Dai, M.N.,2012, Fluid action on zircon growth and recrystallizationduring quartz veining within UHP eclogite: Insights fromU-Pb ages, O-Hf isotopes and trace elements: Lithos, v.136‒139, p. 126‒144.

Shi, Y., and Wang, Q., 2006, Variation in peak P-T conditionsacross the upper contact of the UHP terrane, Dabieshan,China: Gradational or abrupt: Journal of MetamorphicGeology, v. 24, p. 803‒822.

Spandler, C., Hermann, J., Arculus, R., and Mavrogenes, J.,2003, Redistribution of trace elements during prograde meta-morphism from lawsonite blueschist to eclogite-facies:Implications for deep subduction-zone processes:

Contributions to Mineralogy and Petrology, v. 146, p. 205‒222.

Spandler, C., Mavrogenes, J., and Hermann, J., 2007,Experimental constraints on element mobility from sub-ducted sediments using high-P synthetic fluid/melt inclu-sions: Chemical Geology, v. 239, p. 228‒249.

Spandler, C., Pettke, T., and Rubatto, D., 2011, Internal andexternal fluid sources for eclogite-facies veins in theMonviso meta-ophiolite, Western Alps: Implications forfluid flow in subduction zones: Journal of Petrology, v. 0,p. 1–30. doi:10.1093/petrology/egr025

Stöckhert, B., Duyster, J., Trepmann, C., and Massonne, H.J.,2001, Microdiamond daughter crystals precipitated fromsupercritical COH+ silicate fluids included in garnet,Erzgebirge, Germany: Geology, v. 29, p. 391‒394.

Stracke, A., Bizimis, M., and Salters, V.J.M., 2003, Recyclingoceanic crust: Quantitative constraints: GeochemistryGeophysics Geosystems, v. 4, p. 8003.

Sun, S.S., and McDonough, W.F., 1989, Chemical and isotopicsystematics of oceanic basalts: Implications for mantle com-position and processes: Geological Society London SpecialPublications, v. 42, p. 313‒345.

Sun, X.M., Xu, L., Sun, W.D., Zhai, W., Liang, Y.H., Tang, Q.,Liang, J., Zhang, Z.M., Shen, K., Wang, F.Y., Ling, M.X.,and Zartman, R.E., 2011, Channelized fluids in subductedcontinental crust: Constraints from δD–δ 18O of quartz andfluid inclusions in quartz veins from the Chinese continentalscientific drilling project: International Geology Review, v.53, p. 1443–1463. doi:10.1080/00206811003625334

Svensen, H., Jamtveit, B., Banks, D.A., and Austrheim, H., 2001,Halogen contents of eclogite-facies fluid inclusions andminerals: Caledonides, western Norway: Journal ofMetamorphic Geology, v. 19, p. 165‒178.

Vielzeuf, D., and Holloway, J.R., 1988, Experimental determina-tion of the fluid-absent melting relations in the pelitic system:Contributions to Mineralogy and Petrology, v. 98, p. 257‒276.

Wallis, S., Tsuboi, M., Suzuki, K., Fanning, M., Jiang, L., andTanaka, T., 2005, Role of partial melting in the evolution ofthe Sulu (eastern China) ultrahigh-pressure terrane: Geology,v. 33, p. 129‒132.

Wiechert, U., Fiebig, J., Przybilla, R., Xiao, Y.L., and Hoefs, J.,2002, Excimer laser isotope-ratio-monitoring mass spectro-metry for in situ oxygen isotope analysis: Chemical Geology,v. 182, p. 179‒194.

Xia, Q.K., Sheng, Y.M., Yang, X.Z., and Yu, H.M., 2005,Heterogeneity of water in garnets from UHP eclogites, east-ern Dabieshan, China: Chemical Geology, v. 224, p. 237‒246.

Xia, Q.X., Zheng, Y.F., and Hu, Z.C., 2010, Trace elements inzircon and coexisting minerals from low-T/UHP metagranitein the Dabie orogen: Implications for action of supercriticalfluid during continental subduction-zone metamorphism:Lithos, v. 114, p. 385‒412.

Xia, Q.X., Zheng, Y.F., Lu, X.N., Hu, Z.C., and Xu, H.J., 2012,Formation of metamorphic and metamorphosed garnets inthe low-T/UHP metagranite during continental collision inthe Dabie orogeny: Lithos, v. 136‒39, p. 73‒92.

Xia, Q.X., Zheng, Y.F., Yuan, H., and Wu, F.Y., 2009,Contrasting Lu-Hf and U-Th-Pb isotope systematics betweenmetamorphic growth and recrystallization of zircon fromeclogite-facies metagranites in the Dabie orogen, China:Lithos, v. 112, p. 477‒496.

Xia, Q.X., Zheng, Y.F., and Zhou, L.G., 2008, Dehydration andmelting during continental collision: Constraints from

International Geology Review 1121

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

element and isotope geochemistry of low-T/UHP graniticgneiss in the Dabie orogeny: Chemical Geology, v. 247, p.36‒65.

Xiao, Y.L., Hoefs, J., Hou, Z.H., Simon, K., and Zhang, Z.M.,2011, Fluid/rock interaction and mass transfer in continentalsubduction zones: Constraints from trace elements and iso-topes (Li, B, O, Sr, Nd, Pb) in UHP rocks from the Chinesecontinental scientific drilling program, Sulu, East China:Contributions to Mineralogy and Petrology, v. 162, p. 797‒819.

Xiao, Y.L., Hoefs, J., Van den Kerkhof, A.M., Fiebig, J., andZheng, Y.F., 2000, Fluid history of UHP metamorphism inDabie Shan, China: A fluid inclusion and oxygen isotopestudy on the coesite-bearing eclogite from Bixiling:Contributions to Mineralogy and Petrology, v. 139, p.1–16. doi:10.1007/s004100050570

Xiao, Y.L., Hoefs, J., Van den Kerkhof, A.M., and Li, S.G.,2001, Geochemical constraints of the eclogite and granulitefacies metamorphism as recognized in the Raobazhai com-plex from North Dabie Shan, China: Journal of MetamorphicGeology, v. 19, p. 3‒19.

Xiao, Y.L., Hoefs, J., Van den Kerkhof, A.M., Simon, K., Fiebig,J., and Zheng, Y.F., 2002, Fluid evolution during HP andUHP metamorphism in Dabie Shan, China: Constraints frommineral chemistry, fluid inclusions and stable isotopes:Journal of Petrology, v. 43, p. 1505‒1527.

Xiao, Y.L., Sun, W.D., Hoefs, J., Simon, K., Zhang, Z.M., Li,S.G., and Hofmann, A.W., 2006, Making continental crustthrough slab melting: Constraints from niobium-tantalumfractionation in UHP metamorphic rutile: Geochimica etCosmochimica Acta, v. 70, p. 4770‒4782.

Xiao, Y.L., Zhang, Z.M., Hoefs, J., and van den Kerkhof, A.M.,2006b, Ultrahigh-pressure metamorphic rocks from theChinese continental scientific drilling project: II Oxygenisotope and fluid inclusion distributions through verticalsections: Contributions to Mineralogy and Petrology, v.152, p. 443‒458.

Xu, S.T., Okay, A.I., Ji, S.Y., Sengor, A.M.C., Wen, S., Liu, Y.C.,and Jiang, L.L., 1992, Diamond from the Dabie-Shan meta-morphic rocks and its implication for tectonic setting:Science, v. 256, p. 80‒82.

Yui, T.F., Rumble, D., and Lo, C.H., 1995, Unusually low δ18Oultra-high-pressure metamorphic rocks from the SuluTerrain, eastern China: Geochimica et Cosmochimica Acta,v. 59, p. 2859‒2864.

Zhang, Z.M., Shen, K., Liou, J.G., Dong, X., Wang, W., Yu, F.,and Liu, F., 2011, Fluid–rock interactions during UHP meta-morphism: A review of the Dabie–Sulu orogen, east-centralChina: Journal of Asian Earth Sciences, v. 42, p. 316‒329.

Zhang, Z.M., Shen, K., Sun, W.D., Liu, Y.S., Liou, J.G., Shi, C.,and Wang, J.L., 2008, Fluids in deeply subducted continentalcrust: Petrology, mineral chemistry and fluid inclusion of UHPmetamorphic veins from the Sulu orogen, eastern China:Geochimica et Cosmochimica Acta, v. 72, p. 3200‒3228.

Zhang, Z.M., Shen, K., Xiao, Y.L., van den Kerkhof, A.M.,Hoefs, J., and Liou, J.G., 2005, Fluid composition and evo-lution attending UHP metamorphism: Study of fluid inclu-sions from drill cores, southern Sulu Belt, Eastern China:International Geology Review, v. 47, 297–309. doi:10.2747/0020-6814.47.3.297

Zhao, Z.F., Chen, B., Zheng, Y.F., Chen, R.X., and Wu, Y.B.,2007b, Mineral oxygen isotope and hydroxyl contentchanges in ultrahigh-pressure eclogite-gneiss contacts fromChinese Continental Scientific Drilling Project cores: Journalof Metamorphic Geology, v. 25, p. 165‒186.

Zhao, Z.F., Zheng, Y.F., Chen, R.X., Xia, Q.X., and Wu, Y.B.,2007a, Element mobility in mafic and felsic ultrahigh-pres-sure metamorphic rocks during continental collision:Geochimica et Cosmochimica Acta, v. 71, p. 5244‒5266.

Zheng, Y.F., 2008, A perspective view on ultrahigh-pressuremetamorphism and continental collision in the Dabie-Suluorogenic belt: Chinese Science Bulletin, v. 53, p. 3081‒3104.

Zheng, Y.-F., 2009, Fluid regime in continental subductionzones: Petrological insights from ultrahigh-pressure meta-morphic rocks: Journal of the Geological Society, v. 166,763–782. doi:10.1144/0016-76492008-016R

Zheng, Y.F., Fu, B., Gong, B., and Li, L., 2003, Stable isotopegeochemistry of ultrahigh pressure metamorphic rocks from theDabie-Sulu orogen in China: Implications for geodynamics andfluid regime: Earth-Science Reviews, v. 62, p. 105‒161.

Zheng, Y.F., Fu, B., Gong, B., and Li, S.G., 1996, Extreme O-18depletion in eclogite from the Su-Lu terrane in East China:European Journal of Mineralogy, v. 8, p. 317‒323.

Zheng, Y.F., Fu, B., Xiao, Y., Li, Y.L., and Gong, B., 1999,Hydrogen and oxygen isotope evidence for fluid-rock inter-actions in the stages of pre- and post-UHP metamorphism inthe Dabie Mountains: Lithos, v. 46, p. 677‒693.

Zheng, Y.F., Gao, T.S., Wu, Y.B., Gong, B., and Liu, X.M.,2007, Fluid flow during exhumation of deeply subductedcontinental crust: Zircon U-Pb age and O-isotope studies ofa quartz vein within ultrahigh-pressure eclogite: Journal ofMetamorphic Geology, v. 25, p. 267‒283.

Zheng, Y.F., Gao, X.Y., Chen, R.X., and Gao, T., 2011a, Zr-in-rutile thermometry of eclogite in the Dabie orogen:Constraints on rutile growth during continental subduction-zone metamorphism: Journal of Asian Earth Sciences, v. 40,p. 427‒451.

Zheng, Y.F., Wu, Y.B., Chen, F.K., Gong, B., Li, L., and Zhao,Z.F., 2004, Zircon U-Pb and oxygen isotope evidence for alarge-scale 18O depletion event in igneous rocks during theNeoproterozoic: Geochimica et Cosmochimica Acta, v. 68,p. 4145‒4165.

Zheng, Y.F., Xia, Q.X., Chen, R.X., and Gao, X.Y., 2011b,Partial melting, fluid supercriticality and element mobilityin ultrahigh-pressure metamorphic rocks during continentalcollision: Earth-Science Reviews, v. 107, p. 342‒374.

Zheng, Y.F., Zhou, J.B., Wu, Y.B., and Xie, Z., 2005, Low-grademetamorphic rocks in the Dabie-Sulu orogenic belt: Apassive-margin accretionary wedge deformed during conti-nent seduction: International Geology Review, v. 47, p.851‒871.

Zong, K.Q., Liu, Y.S., Gao, C.G., Hu, Z.C., and Gao, S., 2011,Garnet-spinel-corundum-quartz-bearing titanohematite veinsin eclogite from the Sulu ultrahigh-pressure terrane: Imprintof a short-lived, high-temperature metamorphic stage:Journal of Asian Earth Sciences, v. 42, p. 704‒714.

Zong, K.Q., Liu, Y.S., Hu, Z.C., Kusky, T., Wang, D.B., Gao,C.G., Gao, S., and Wang, J.Q., 2010, Melting-induced fluidflow during exhumation of gneisses of the Sulu ultrahigh-pressure terrane: Lithos, v. 120, p. 490‒510.

1122 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Appendix

Figure A1. Laser Raman spectrum for representative mineralinclusions hosted by garnet in the amphibolite.

Figure A2. Negative correlation of BaO (wt.%) versus SiO2

(wt.%) in a phengitic muscovite (BSE image) from the graniticgneiss (sample P5).

International Geology Review 1123

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Table A1. Results of trace elements for AGV-2 (andesite) and BHVO-2 (basalt) standards analysed by solution ICP-MS.

AGV-2 (n = 3) BHVO-2 (n = 2)

USGS Stand. Isotope Ave. 1σ RSD (%) Ref. RE (%) Ave. 1σ RSD (%) Ref. RE (%)

Li 7 11.2 0.26 2.4 11 1.6 4.86 0.04 0.73 4.8 1.1Be 9 2.36 0.15 6.2 2.3 2.6 1.06 0.08 7.4 1.0 5.5Sc 45 12.8 0.51 4.0 13 −1.8 31.6 0.57 1.8 32 −1.3V 51 119 4.2 3.5 122 −2.7 319 2.8 0.89 317 0.63Cr 53 13.9 0.58 4.1 16 −13 281 1.7 0.62 280 0.44Co 59 16.0 0.58 3.6 16 0.2 44.8 0.68 1.5 45 −0.49Ni 60 15.5 0.70 4.5 20 −22 119 0.66 0.55 119 0.39Cu 65 50.8 1.3 2.5 53 −4.2 129 2.1 1.7 127 1.2Zn 66 85.1 2.8 3.3 86 −1.0 106 0.20 0.19 103 3.0Ga 71 21.2 0.61 2.9 20 5.9 22.1 0.06 0.29 22 0.66Rb 85 67.8 0.75 1.1 66.3 2.2 9.06 0.06 0.62 9.11 −0.55Sr 88 655 6.0 0.92 661 −1.0 388.4 3.6 0.94 396 −1.9Y 89 19.4 0.06 0.30 19 2.3 26.0 0.21 0.82 26 −0.19Zr 90 233 1.2 0.50 230 1.4 171 1.5 0.87 172 −0.61Nb 93 13.6 0.06 0.42 14.5 −6.0 17.8 0.08 0.44 18.1 −1.4Cs 133 1.11 0.02 1.9 1.2 −7.8 0.10 0.01 7.4 0.10 −5.0Ba 135 1072 16.5 1.5 1130 −5.1 124.7 3.3 2.6 131 −4.8La 139 35.4 0.47 1.3 37.9 −6.7 14.5 0.36 2.5 15.2 −4.3Ce 140 65.2 0.92 1.4 68.6 −5.0 36.2 1.0 2.8 37.5 −3.5Pr 141 7.65 0.13 1.7 7.84 −2.5 5.16 0.15 2.9 5.35 −3.6Nd 146 28.6 0.45 1.6 30.5 −6.4 23.8 0.71 3.0 24.5 −2.9Sm 147 5.15 0.10 2.0 5.49 −6.1 5.95 0.18 3.1 6.07 −2.0Eu 151 1.51 0.02 1.1 1.53 −1.3 2.02 0.07 3.5 2.07 −2.4Gd 157 4.78 0.06 1.3 4.52 5.7 6.10 0.19 3.1 6.24 −2.3Tb 159 0.60 0.01 0.96 0.64 −5.7 0.92 0.04 3.9 0.92 −0.54Dy 161 3.34 0.07 2.0 3.47 −3.7 5.28 0.21 3.9 5.31 −0.66Ho 165 0.61 0.01 0.94 0.65 −5.6 0.97 0.04 4.4 0.98 −1.0Er 166 1.73 0.04 2.3 1.81 −4.6 2.54 0.11 4.2 2.54 −0.20Tm 169 0.23 0.01 2.5 0.26 −10 0.33 0.01 4.3 0.33 0.00Yb 172 1.53 0.05 2.9 1.62 −5.3 2.03 0.07 3.5 2.0 1.5Lu 175 0.23 0.01 2.5 0.247 −5.5 0.28 0.01 5.1 0.274 2.2Hf 180 4.73 0.18 3.8 5 −5.5 4.47 0.21 4.6 4.36 2.4Ta 181 0.74 0.03 4.1 0.87 −15 1.14 0.05 4.4 1.14 −0.44Pb 208 11.6 0.66 5.6 13.2 −12 2.53 0.36 14 1.60 58Th 232 5.15 0.38 7.3 6.1 −16 1.16 0.06 5.5 1.22 −5.3U 238 1.57 0.13 8.0 1.86 −16 0.40 0.02 5.4 0.403 −2.0

Notes: n, number of analyses, Ave., average of measured values; Ref., reference values; RSD, relative standard deviation; RE, relative error betweenmeasured and reference values. Reference values are derived from http://georem.mpch-mainz.gwdg.de/sample_query_pref.asp and Jochum and Nehring(2006).

1124 J. Huang and Y. Xiao

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Table

A2.

Chemistryof

representativ

emineralsin

thestud

iedgraniticgn

eiss

andam

phibolite

from

theSDZ.

Sam

ple

P5

P7

P7

P8

P10

P6

P7

P7

P8

P10

P1

P2

P3

P4

P5

P6

P7

P7

P10

mineral

Grt

Grt

Grt(in)

Grt

Grt

Amp

Amp

Amp(in)

Amp

Amp

Pl

Pl

Pl

Pl

Pl

Pl

Pl

Pl(in)

Pl

n5

71

54

105

53

68

517

510

15

11

SiO

238

.338

.837

.85

38.7

38.7

48.8

46.4

46.0

49.6

46.0

65.9

65.4

65.5

63.9

63.4

64.6

61.6

61.07

62.1

TiO

2bd

0.14

0.14

bd0.09

0.26

0.24

0.47

0.36

0.27

bdbd

bdbd

bdbd

bd<0.08

bdAl 2O3

21.9

22.3

21.43

22.3

22.2

8.5

11.9

15.1

10.2

12.1

21.7

21.9

21.9

23.2

23.1

22.8

24.9

25.47

24.7

Cr 2O3

bdbd

<0.08

bdbd

bdbd

bdbd

0.14

bdbd

bdbd

bdbd

bd<0.08

bdFeO

27.5

23.8

25.67

25.3

25.7

12.1

13.4

12.3

11.1

14.0

0.08

0.07

0.09

bd0.16

0.06

0.27

0.48

170.20

MnO

2.93

1.64

0.61

910.72

0.97

0.41

0.29

0.18

0.26

0.25

bdbd

bdbd

bdbd

bd<0.06

bdMgO

5.66

6.07

4.34

7.15

4.01

14.1

12.8

12.0

15.2

12.1

bdbd

bdbd

bdbd

bd<0.05

bdCaO

4.59

8.16

9.55

6.44

9.99

10.6

10.5

9.52

9.38

11.1

1.95

2.16

2.27

3.64

3.62

3.23

5.46

5.98

5.34

Na 2O

bd0.04

<0.04

bdbd

1.49

1.62

2.31

1.65

1.86

10.8

10.7

10.6

9.93

9.86

9.96

8.68

8.45

8.86

K2O

bdbd

<0.03

bdbd

0.11

0.23

0.12

0.17

0.33

0.12

0.15

0.15

0.19

0.09

0.03

0.04

0.03

780.05

BaO

bdbd

<0.11

bdbd

bdbd

bdbd

bd0.08

bd0.06

0.14

0.27

bdbd

<0.14

bdCl

bdbd

<0.02

bdbd

0.02

bdbd

bdbd

bdbd

0.04

0.03

0.03

bdbd

<0.02

bdwt-total

100.9

100.8

99.60

100.6

101.6

96.3

97.3

97.7

97.7

97.9

100.5

100.4

100.5

100.9

100.1

100.7

100.9

101.49

101.3

Si

2.97

62.97

62.97

22.97

22.98

37.01

06.62

46.47

56.85

56.60

62.87

32.85

72.85

82.78

62.78

52.82

42.70

42.67

092.71

6Ti

0.00

00.00

80.00

80.00

00.00

50.02

80.02

60.04

90.03

70.02

90.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

000.00

0Al

2.00

72.01

21.98

32.01

32.011

1.43

52.00

32.50

01.66

32.05

21.116

1.12

61.12

61.19

31.19

41.17

71.28

71.31

281.27

4Cr

0.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.01

60.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

000.00

0Fe3

+0.04

10.02

80.05

80.04

40.01

20.79

40.98

60.92

61.29

60.67

20.05

60.07

30.06

40.08

60.08

10.02

20.04

60.06

410.04

9Fe2

+1.74

61.49

81.62

71.57

81.64

10.65

40.611

0.51

80.00

01.011

0.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

0Mn

0.19

30.10

70.04

10.04

70.06

30.05

00.03

50.02

20.03

10.03

10.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

000.00

0Mg

0.65

60.69

40.50

80.81

80.46

03.02

82.71

52.51

03.13

42.58

40.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

000.00

0Ca

0.38

20.67

10.80

30.52

90.82

41.62

91.60

91.43

61.39

11.70

70.09

10.10

10.10

60.17

00.17

00.15

10.25

70.28

020.25

0Na

0.00

00.00

70.00

00.00

00.00

00.41

50.44

90.63

10.44

30.51

70.911

0.90

50.89

80.84

00.84

00.84

40.73

90.71

650.75

1K

0.00

00.00

00.00

00.00

00.00

00.01

90.04

20.02

20.03

10.06

00.00

70.00

80.00

80.011

0.00

50.00

20.00

20.00

210.00

3Ba

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncCl

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

nc∑Cation

8.0

8.0

8.0

8.0

8.0

15.1

15.1

15.1

14.9

15.3

5.1

5.1

5.1

5.1

5.1

5.0

5.0

5.0

5.0

Oxy

gen

1212

1212

1223

2323

2323

88

88

88

88

8Ab

Prp

0.22

00.23

40.17

10.27

50.15

40.90

30.89

20.88

70.82

30.82

70.84

70.74

00.71

740.74

8An

Grs

0.12

80.22

60.27

00.17

80.27

60.09

00.10

00.10

50.16

70.16

80.15

20.25

70.28

050.24

9Or

Alm

0.58

70.50

40.54

60.53

10.54

90.00

70.00

80.00

80.01

00.00

50.00

20.00

20.00

210.00

3Sps

0.06

50.03

60.01

40.01

60.02

1And

0.02

00.01

30.02

80.02

20.00

6

(Con

tinued)

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Table

A2.

(Con

tinued).

Sam

ple

P3

P5

P5

P7

P1

P2

P3

P4

P5

P6

P7

P7

P8

P9

P1

P2

P3

P5

P10

P7

mineral

Kfs

Kfs

Kfs

Kfs

(in)

Bi

Bi

Bi

Bi

Bi

Bi

Bi

Bi(in)

Bi

Bi

Ms

Ms

Ms

Ms

Ms

Ms(in)?

n1

cr

24

26

44

62

13

25

76

81

1SiO

264

.463

.563

.84

64.9

37.2

37.2

37.0

37.0

36.5

37.1

36.3

37.2

36.2

36.5

46.0

46.1

46.2

46.8

44.1

47.74

TiO

2bd

bdbd

bd2.26

2.67

2.88

2.41

2.26

1.67

1.62

0.77

1.68

1.69

1.27

0.98

1.21

0.36

0.34

0.14

19Al 2O3

18.7

18.52

19.24

18.5

16.7

16.4

16.6

17.3

17.4

17.2

18.7

20.4

18.8

18.6

29.3

29.2

29.4

31.0

37.1

35.63

Cr 2O3

bdbd

bdbd

bdbd

0.11

bdbd

0.10

0.07

bdbd

bdbd

bd0.06

bdbd

0.02

07FeO

bd0.14

32bd

0.33

16.9

17.0

17.4

16.7

16.0

14.0

13.7

9.94

14.0

14.0

4.52

4.39

4.20

2.70

1.61

1.63

MnO

bdbd

bdbd

0.65

0.63

0.59

0.52

0.33

0.11

0.06

bd0.08

0.11

0.08

0.07

bd0.12

bdbd

MgO

bdbd

bdbd

11.7

11.2

10.8

11.5

11.6

14.8

14.1

17.9

14.0

14.3

2.09

2.18

2.07

2.13

0.59

1.07

67CaO

bdbd

bd0.06

0.24

0.11

bd0.18

0.75

bdbd

0.23

0.08

0.06

bd0.06

bd0.09

bd0.24

95Na 2O

0.14

0.19

210.28

10.16

0.06

0.06

0.05

bd0.21

0.37

0.40

0.88

0.46

0.40

0.27

0.31

0.35

0.79

2.03

4.2

K2O

16.9

15.77

15.08

16.2

9.61

9.46

9.52

9.54

8.79

8.81

8.73

3.39

8.81

8.83

10.6

10.4

10.4

9.81

7.79

4.8

BaO

0.15

1.57

3.09

0.39

0.61

0.48

0.65

0.58

0.87

0.75

1.17

bd0.63

0.94

0.99

1.25

1.40

0.98

2.77

bdCl

bdbd

bd0.02

0.01

0.02

bd0.04

0.03

0.02

bdbd

bdbd

bd0.01

bd0.03

bdbd

wt-total

100.2

99.695

310

1.53

110

0.5

95.7

95.1

95.5

95.7

94.5

94.9

94.7

90.7

94.8

95.5

95.2

94.9

95.3

94.6

96.3

95.65

Si

2.97

52.99

73.00

33.00

22.69

82.73

22.70

92.68

82.68

62.68

12.62

42.86

22.62

32.62

13.119

3.13

53.13

63.14

62.93

13.07

7Ti

0.00

00.00

00.00

00.00

00.12

30.14

70.15

90.13

20.12

50.09

10.08

80.04

50.09

20.09

10.06

50.05

00.06

20.01

80.01

70.00

7Al

1.01

71.03

01.06

71.00

91.42

51.41

61.43

01.47

91.51

21.46

71.59

11.84

71.60

71.57

72.34

42.33

72.35

12.45

72.90

32.70

6Cr

0.00

00.00

00.00

00.00

00.00

00.00

00.00

70.00

00.00

00.00

60.00

40.00

00.00

00.00

00.00

00.00

00.00

30.00

00.00

00.00

1Fe3

+0.03

90.00

00.00

00.00

00.79

90.67

20.70

40.74

20.62

90.68

50.71

70.00

00.64

40.71

40.33

10.34

80.30

30.27

00.27

70.20

5Fe2

+0.00

00.00

60.00

00.01

30.22

40.37

00.35

90.27

10.35

40.16

20.10

90.63

90.20

40.12

90.00

00.00

00.00

00.00

00.00

00.00

0Mn

0.00

00.00

00.00

00.00

00.04

00.03

90.03

70.03

20.02

00.00

70.00

40.00

00.00

50.00

70.00

40.00

40.00

00.00

70.00

00.00

0Mg

0.00

00.00

00.00

00.00

01.27

31.23

11.19

11.25

41.28

11.60

01.53

12.07

11.52

41.54

10.211

0.22

10.20

90.21

30.05

90.10

3Ca

0.00

00.00

00.00

00.00

30.01

90.00

90.00

00.01

40.05

90.00

00.00

00.01

90.00

60.00

50.00

00.00

40.00

00.00

70.00

00.01

7Na

0.01

30.01

80.02

60.01

50.00

80.00

90.00

80.00

00.02

90.05

20.05

70.13

20.06

40.05

60.03

60.04

10.04

60.10

30.26

20.52

5K

0.99

50.94

90.90

50.95

80.88

80.88

50.88

90.88

40.82

60.81

20.80

50.33

30.81

30.80

80.92

00.90

40.90

10.84

20.66

10.39

5Ba

ncnc

ncnc

0.01

70.01

40.01

90.01

70.02

50.02

10.03

30.00

00.01

80.02

7nc

ncnc

ncnc

ncCl

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

∑Cation

5.0

5.0

5.0

5.0

7.5

7.5

7.5

7.5

7.5

7.6

7.5

7.9

7.6

7.5

7.0

7.0

7.0

7.1

7.1

7.1

Oxy

gen

88

88

1111

1111

1111

1111

1111

1111

1111

1111

Ab

0.01

30.01

80.02

80.01

5An

0.00

00.00

00.00

00.00

3Or

0.98

70.98

20.97

20.98

2

(Con

tinued)

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Table

A2.

(Con

tinued).

Sam

ple

P7

P7

P8

P10

P1

P2

P4

P5

P7

P8

P10

P7

P7

P8

P10

P7

P8

P10

P5

P6

mineral

Pg

Pg(in)

Pg

Pg

Ep

Ep

Ep

Ep

Ep(in)

Ep

Ep

Clz

Clz

(in)

Clz

Clz

Zo

Zo

Zo

Rt

Rt

n2

24

31

13

21

52

44

46

14

23

3SiO

244

.845

.546

.046

.538

.038

.138

.438

.038

.738

.439

.038

.438

.738

.539

.039

.439

.039

.5bd

bdTiO

20.10

0.83

0.11

0.08

0.10

0.09

bdbd

0.19

0.08

0.28

0.14

0.17

0.11

0.13

bd0.07

bd97

.698

.2Al 2O3

39.1

40.6

40.2

40.3

25.4

24.5

28.9

28.6

28.5

27.2

24.3

29.6

29.1

29.6

29.5

33.1

32.7

33.0

bdbd

Cr 2O3

bdbd

0.07

bdbd

bdbd

bd0.09

0.10

bdbd

0.09

0.09

0.08

bdbd

bdbd

0.17

FeO

0.39

0.73

0.61

0.49

10.6

11.4

6.60

5.59

7.35

8.69

10.9

5.35

6.45

5.74

5.92

1.29

1.60

1.88

0.60

0.50

MnO

bdbd

bdbd

0.48

0.56

0.29

0.15

0.07

0.26

0.19

bd0.13

bd0.14

bdbd

bdbd

bdMgO

0.20

0.35

0.10

0.14

bdbd

0.14

0.19

0.09

0.11

2.73

0.26

0.24

0.22

0.26

bd0.06

0.13

bdbd

CaO

0.32

0.54

0.34

0.33

23.1

23.0

22.9

22.6

23.3

23.1

19.6

22.7

22.9

22.4

22.9

24.3

24.0

24.1

0.13

0.05

Na 2O

7.25

7.45

7.32

7.28

bdbd

0.09

bdbd

bd1.32

bdbd

bdbd

bdbd

bd0.12

bdK2O

0.90

0.19

0.82

0.78

bdbd

bdbd

bdbd

0.30

bdbd

bdbd

bdbd

bdbd

0.05

BaO

bdbd

bd0.10

bdbd

bdbd

bd0.11

bdbd

bdbd

bdbd

bdbd

bd0.21

Cl

bdbd

bd0.02

bdbd

bdbd

bdbd

bd0.01

bdbd

bdbd

bdbd

0.03

bdwt-total

93.1

96.2

95.5

95.8

97.6

97.5

97.0

95.0

98.3

97.8

97.7

96.4

97.8

96.5

97.7

98.1

97.4

98.6

98.3

99.1

Si

2.92

42.85

52.92

02.93

52.98

12.99

82.98

23.01

22.98

62.98

43.05

02.99

72.98

53.00

23.00

12.99

02.97

82.98

20.00

00.00

0Ti

0.00

50.03

90.00

50.00

40.00

60.00

50.00

00.00

00.011

0.00

50.01

60.00

80.01

00.00

70.00

80.00

00.00

40.00

00.98

80.99

1Al

3.00

82.99

93.00

63.00

02.34

82.27

12.64

62.66

72.58

42.48

72.24

52.72

12.65

22.71

72.67

82.95

52.94

72.93

80.00

00.00

0Cr

0.00

00.00

00.00

30.00

00.00

00.00

00.00

00.00

00.00

60.00

60.00

00.00

00.00

60.00

50.00

50.00

00.00

00.00

00.00

00.00

2Fe3

+0.14

30.29

30.17

50.16

80.67

70.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.02

70.01

7Fe2

+0.00

00.00

00.00

00.00

00.01

70.74

80.42

90.37

00.47

40.56

40.71

20.34

90.41

60.37

50.38

10.08

20.10

20.119

0.00

00.00

0Mn

0.00

00.00

00.00

00.00

00.03

20.03

80.01

90.01

00.00

40.01

70.01

30.00

00.00

90.00

00.00

90.00

00.00

00.00

00.00

00.00

0Mg

0.02

00.03

30.01

00.01

30.00

00.00

00.01

70.02

30.01

00.01

20.31

90.03

00.02

80.02

60.03

00.00

00.00

70.01

40.00

00.00

0Ca

0.02

20.03

60.02

30.02

21.93

81.94

01.90

71.91

81.92

51.92

51.64

41.89

51.89

51.86

81.88

81.97

41.96

21.94

70.00

20.00

1Na

0.91

60.90

50.89

90.89

20.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

30.00

0K

0.07

50.01

60.06

60.06

30.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

1Ba

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

Cl

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

∑Cation

7.1

7.2

7.1

7.1

8.0

8.0

8.0

8.0

8.0

8.0

8.0

8.0

8.0

8.0

8.0

8.0

8.0

8.0

1.0

1.0

Oxy

gen

1111

1111

1313

1313

1313

1313

1313

1313

1313

22

(Con

tinued)

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Table

A2.

(Con

tinued).

Sam

ple

P7

P7

P8

P10

P1

P4

P7

P7

P8

P10

P1

P2

P3

P5

mineral

Rt

Rt(in)

Rt

Rt

Ttn

Ttn

Ttn

Ilm

Ilm

Ilm

Chl

Chl

Chl

Chl

N2

23

21

12

22

11

13

3SiO

2bd

0.1

bdbd

30.4

30.7

29.9

bdbd

0.3

27.6

27.8

27.4

28.6

TiO

298

.997

.998

.998

.936

.637

.937

.949

.249

.450

.70.07

bd0.13

0.50

Al 2O3

bdbd

0.23

bd1.65

1.20

1.11

bdbd

0.17

18.1

17.1

18.1

18.0

Cr 2O3

0.13

bd0.13

0.11

bdbd

bdbd

0.09

bdbd

bdbd

bdFeO

0.36

0.95

0.62

0.39

0.68

0.37

0.26

46.8

47.2

43.1

22.3

23.5

24.4

22.7

MnO

bdbd

0.06

bd0.21

bdbd

0.88

1.60

1.11

0.78

0.77

0.70

0.37

MgO

bdbd

bdbd

bdbd

bd0.16

0.33

0.16

18.3

17.1

15.9

16.9

CaO

0.07

0.17

0.11

0.21

27.4

28.4

28.4

bd0.06

0.06

bd0.12

0.13

0.16

Na 2O

bdbd

0.04

bd0.04

bdbd

bd0.04

bdbd

bdbd

bdK2O

bdbd

bdbd

bdbd

bdbd

bdbd

bdbd

0.09

1.21

BaO

bdbd

0.18

bdbd

bdbd

bdbd

0.19

bdbd

0.20

0.22

Cl

bdbd

bdbd

bdbd

bdbd

bdbd

bd0.01

bd0.03

wt-total

99.5

99.0

99.9

99.5

97.0

98.6

97.5

97.1

98.5

95.8

87.1

86.4

86.8

87.2

Si

0.00

00.00

10.00

00.00

01.01

21.00

70.99

40.00

00.00

00.00

95.78

55.93

75.86

06.03

9Ti

0.99

40.98

60.98

50.99

20.91

70.93

70.94

60.95

90.94

51.00

50.01

20.00

00.02

10.08

0Al

0.00

00.00

00.00

40.00

00.06

50.04

60.04

40.00

00.00

00.00

54.45

84.30

14.56

34.49

5Cr

0.00

10.00

00.00

10.00

10.00

00.00

00.00

00.00

00.00

20.00

00.00

00.00

00.00

00.00

0Fe3

+0.011

0.02

60.02

60.01

60.07

80.06

60.07

60.08

10.111

0.00

00.00

00.00

00.00

00.00

0Fe2

+0.00

00.00

00.00

00.00

00.00

00.00

00.00

00.93

40.89

20.94

93.90

04.19

74.36

54.00

9Mn

0.00

00.00

00.00

10.00

00.00

60.00

00.00

00.01

90.03

40.02

50.13

80.14

00.12

60.06

6Mg

0.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

60.01

30.00

65.70

85.42

55.06

55.31

2Ca

0.00

10.00

20.00

20.00

30.97

81.00

01.00

90.00

00.00

20.00

20.00

00.02

80.02

90.03

5Na

0.00

00.00

00.00

10.00

00.00

20.00

00.00

00.00

00.00

20.00

00.00

00.00

00.00

00.00

0K

0.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.00

00.02

40.32

6Ba

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

Cl

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

ncnc

∑Cation

1.0

1.0

1.0

1.0

3.1

3.1

3.1

2.0

2.0

2.0

20.0

20.0

20.1

20.4

Oxy

gen

22

22

55

53

33

2828

2828

Note:

(1)n,

numberof

analyses;bd,below

detectionlim

it;nc,notcalculated.(2)i,mineral

inclusions

ingarnet.(3)Ab,

albite;An,

anorthite;Or,orthoclase;Prp,pyrope;Grs,grossular;Alm

,almandine;Spe,spessartine;

And,

andradite.(4)In

therow

forrock

type,G

andA

representgneiss

andam

phibolite,respectiv

ely.

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15

Table A3. Approximate estimation of modal abundance of minerals in multi-phase solid inclusions (MS) in garnet from the amphiboliteP7 and estimated bulk compositions of the MS.

Mineral assemblage and volume content (vol.%)

Comment Qtz Amp Clz Grt Kfs CC Zrn Ap

MS1 8.5 0.4 50 40.5 0.3 0.3MS2 0.15 60 0.4 21.5 18 0.01Density 2.65 3.3 3.16 3.9 2.56 2.75 4.6 3.2

Estimated bulk compositions of multi-phase solid inclusions (MS)wt.% MS1 MS2SiO2 39.9 41.8TiO2 T 0.30Al2O3 9.04 13.3Cr2O3 ‒ ‒FeO 0.31 8.07MnO 0.004 0.12MgO 0.03 7.78CaO 25.2 12.8Na2O 0.08 1.53K2O 7.81 3.02BaO 0.19 0.07Cl 0.01 ‒H2O ‒ ‒

Note: ‘‒’ not estimated; T, trace; mineral density is taken from Deer et al. (1992).

International Geology Review 1129

Dow

nloa

ded

by [

Uni

vers

ite d

e L

orra

ine]

at 0

6:22

29

Sept

embe

r 20

15