[The Journal of Geology, 2014, volume 122, p. 77–97] � 2014 by The University of Chicago.All rights reserved. 0022-1376/2014/12201-0005$15.00. DOI: 10.1086/674423

77

Paleo-Pacific Subduction in the Interior of Eastern China: Evidencefrom Adakitic Rocks in the Edong-Jiurui District

Yi-Zeng Yang,1 Qun Long,1 Wolfgang Siebel,2 Ting Cheng,1

Zhen-Hui Hou,1 and Fukun Chen1,*

1. Chinese Academy of Sciences Key Laboratory of Crust-Mantle Materials and Environments, School of Earthand Space Sciences, University of Science and Technology of China, Hefei, 230026, China;

2. Department of Geosciences, Universitat Tubingen, 72074 Tubingen, Germany

A B S T R A C T

The Edong-Jiurui district is located more than 1000 km from the current Pacific subduction zone. It is part of thewell-known middle and lower Yangtze River Cu-Fe-Au belt in central eastern China. Cu mineralization in this areais spatially and temporally associated with Late Mesozoic magmatic rocks. These rocks exhibit geochemical featuresof adakites, but their origin is not yet fully understood. To explore the relationship between Cu mineralization andMesozoic magmatism, we report geochemical, Sr-Nd-Pb isotopic, and zircon U-Pb age data from adakitic rocks inthe Edong-Jiurui area. Zircon U-Pb ages point to a protracted period of magmatic activity from 151 to 139 Ma. Thistime span coincides with the Cu mineralization (146–137 Ma) in the middle and lower Yangtze River belt. Adakiticfeatures of the rocks are displayed by high contents of SiO2, Al2O3, Na2O, and Sr; enrichment of light rare earthelements (REEs) and large-ion lithophile elements; depletion of heavy REEs; positive Sr and negative Nb, Ta, and Tianomalies; and high Sr/Y and La/Yb ratios. We favor a model of melt segregation from a plagioclase-free and garnet-bearing residue. Compared to non-Cu-bearing Mesozoic adakitic rocks in the Dabie terrane, adakitic rocks in theEdong-Jiurui area have higher initial �Nd values (�3.4 to �6.3), Pb isotopic ratios, and Th contents and lower Pb/Cevalues. Altogether, these features indicate that the melts were probably derived from subducted ocean mixed withmarine sediment.

Online enhancements: appendix tables and supplementary table.

Introduction

The middle and lower Yangtze River belt (MLYRB)is one of the largest metallogenic provinces in east-ern China, hosting numerous copper, iron, gold,and molybdenum deposits. The genesis of the poly-metallic mineralization, particularly the origin ofcopper, is strongly debated (e.g., Chang et al. 1991;Shu et al. 1992; Chen and Jahn 1998; Wang et al.2003, 2004a, 2004b, 2006a, 2006b, 2007b; Mao etal. 2006; Xie et al. 2007, 2008, 2011b, 2012b; Li etal. 2008, 2009b; Yang and Zhang 2012). In theEdong-Jiurui district, western MLYRB, there is aclose spatial and temporal relationship betweenmagmatic rocks and mineralization (Xie et al. 2007,2008, 2011b; Li et al. 2008, 2009b; Yang and Zhang

Manuscript received April 22, 2013; accepted October 13,2013; electronically published January 3, 2014.

* Author for correspondence; e-mail: fkchen@ustc.edu.cn.

2012). Almost all MLYRB magmatic rocks haveadakitic features (Wang et al. 2003, 2007b; Xie etal. 2008, 2009, 2012a; Ling et al. 2009; Sun et al.2012a, 2012b). Also, previous zircon dating studiessuggest that magmatic rocks related to Cu miner-alization intruded earlier than those related to Fedeposits (Xie et al. 2007, 2008, 2011b).

Different models have been proposed for the or-igin of the ore-related magmatic rocks in theMLYRB. These include partial melting of delami-nated Yangtze lower crust (Zhang et al. 2001; Xuet al. 2002; Wang et al. 2007b) and assimilation andfractional crystallization of mantle-derived melts(Chen and Jahn 1998; Mao et al. 2006; Xie et al.2008, 2011b; Li et al. 2009b). It has also been sug-gested that the melts were produced through slabmelting in response to ridge subduction and finally

78 Y . - Z . Y A N G E T A L .

modified by enriched mantle components andcrustal material (Ling et al. 2009, 2011; Liu et al.2010; Sun et al. 2010). However, these differentmodels have not been tested for plausibility for themagmatic rocks in the Edong-Jiurui district, whichis hundreds of kilometers west of the eastern partof the MLYRB. In this study, we present geochro-nological and geochemical data of 21 magmaticrocks and two mafic dikes from this area. The find-ings pertain to a better understanding of the adak-itic character and the intrusion-related origin ofcopper mineralization in the MLYRB.

Geological Background

The Edong-Jiurui area is well known for its re-markable skarn, porphyry, and strata-bound Cu-Fe-Au-Mo polymetallic ore deposits in the MLYRB (fig.1). Mineralization is sited in a number of large Me-sozoic calc-alkaline intrusions. The Cu-relatedmagmatic rocks include gabbro/diorites, granodi-orites, quartz granodiorites, and granite porphyries.Rocks impregnated with abundant iron formedlater and mainly comprise mafic dikes, quartz mon-zonites, granites, and volcanic rocks (Mao et al.2006; Xie et al. 2007; Li et al. 2008). Altogether,more than 20 Cu-related igneous bodies are knownfrom the Edong-Jiurui district; among them are theYangxin pluton, which hosts the Baishazhen de-posit, the Wushan and Chengmenshan plutons(Yang et al. 2011a), and the Fengshandong, Tong-shankou, and Tonglushan plutons (Xie et al. 2007,2008, 2011b; Li et al. 2008, 2009b; Li et al. 2010b).Igneous bodies that host economic iron depositsinclude the Lingxiang, Jinshandian, and Echengplutons. Some skarn Fe-Cu deposits occur on themargins of the Tieshan and Tonglushan plutons.On the basis of U-Pb zircon ages, the formationtime of ore-related magmas comprises two periods:152–136 Ma for granitoids hosting Cu mineraliza-tion and 135–122 Ma for Fe-hosting igneous bodies(Li et al. 2008, 2009b, 2010b; Xie et al. 2008), fol-lowed by A-type granites at ∼127 Ma (Li et al. 2011,2012). The age of copper mineralization was alsodetermined by Re-Os dating of molybdenite andthat of Fe mineralization by K-Ar dating of albite(Wu and Zou 1997; Sun et al. 2003; Mao et al. 2006;Xie et al. 2007; Li et al. 2008). The dating resultsshow that the ages of Cu mineralization (146–137Ma) and Fe mineralization (140–121 Ma; Sun et al.2003; Mao et al. 2006; Xie et al. 2007; Li et al.2010b) are almost indistinguishable from the agesof the host rocks.

Sedimentary units of the Edong-Jiurui districtconsist of Ordovician to Middle Triassic shallow-

marine clastics and carbonates, Late Triassic to Ce-nozoic continental deposits, and Cretaceous vol-canic rocks that overlie older Precambrianbasement units (e.g., Xie et al. 2011b; Yang et al.2011a). The pre-Triassic strata were intenselyfolded during the Middle Triassic collision betweenthe Yangtze and North China cratons. Late Cre-taceous–Tertiary clastic sediments are restricted tothe western Edong district (Shu et al. 1992). TheCretaceous volcanic rocks constitute a typical bi-modal suite, with mafic rocks similar to Phaner-ozoic Nb-enriched basalts and andesites. SHRIMPzircon U-Pb ages show that the volcanic activitylasted from 130 to 125 Ma (Xie et al. 2011a).

The Dabie orogen lies to the north of the MLYRBand is part of the 2000-km-long Qinling-Dabie-Suluorogen formed during the Triassic subduction/col-lision of the Yangtze and North China blocks (Liet al. 2000; fig. 1). Early Cretaceous intrusive ig-neous rocks consist of intermediate to felsic gran-itoid plutons, with a few mafic intrusions in theDabie orogen. Adakitic rocks generally formed inthe early stage (143–130 Ma), whereas the granitoidplutons younger than 130 Ma do not have high Sr/Y and La/Yb ratios (Ma et al. 2004; Wang et al.2007a; Xu et al. 2007; He et al. 2011). The Tian-tangzhai adakitic intrusion is the biggest pluton,with an outcrop area of more than 400 km2; it ex-hibits high SiO2 and K2O contents, low Mg# values,and enriched Sr-Nd-Pb isotopic characteristics, andthis intrusion is recognized from partial melting ofthickened lower continental crust (Wang et al.2007a; Xu et al. 2012a). The Meichuan adakitic in-trusion has slightly lower SiO2 content, higher Mg#value, and higher Cr and Ni contents than the Tian-tangzhai intrusion, and hence this intrusion is in-terpreted as the product of partial melting of de-laminated lower continental crust mixing withfertile mantle material (Zhang et al. 2010; Xu et al.2012b).

Analytical Methods

Rock samples were broken in a jaw crusher andpowdered to less than 200-mesh particle size beforemajor- and trace-element analyses. Major-elementoxides of whole rock were measured with an X-rayfluorescence spectrometer at Institute of Geologyand Geophysics, Chinese Academy of Sciences,Beijing, and analytical procedures are described inGao et al. (1995). Repeated analyses of every fivesamples for major-element oxides show that rela-tive standard derivations for major-element oxidesare within 5%. Trace-element contents were ana-lyzed on an Agilent 7500a inductively coupled

Figure 1. a, Distribution of ore deposits in the middle-lower Yangtze River belt (after Pan and Dong 1999; Xie etal. 2008). b, Geological map of the Edong-Jiurui district, showing distribution of late Mesozoic igneous rocks, Cu-Fe-Au-Mo deposits, and sample localities (after 1 : 200,000 geological map of China). TLF p Tancheng-Lujiang fault;XGF p Xiangfan-Guangji fault; YCF p Yangxing-Changzhou fault.

80 Y . - Z . Y A N G E T A L .

plasma mass spectrometer (ICP-MS) at the Key Lab-oratory of Crust-Mantle Materials and Environ-ments, Hefei. The analytical precision is generallybetter than 5% (2j).

Rb-Sr, Sm-Nd, and Pb isotopic analyses were per-formed at the Laboratory for Radiogenic IsotopeGeochemistry, Hefei. Sr and Nd isotopic ratioswere corrected for mass fractionation relative to

and , re-86 88 146 144Sr/ Sr p 0.1194 Nd/ Nd p 0.7219spectively. During this study, analyses on standardsolutions of NBS987 and La Jolla yielded mean val-ues of (2j; ) for 87Sr/86Sr0.710232 � 0.000026 n p 5and (2j; ) for 143Nd/0.511830 � 0.000012 n p 4144Nd. Precision of the measured Pb isotopic ratiosis better than 0.01%. For more details, see Chen etal. (2000, 2007).

Zircons were imaged for internal structures bythe cathodoluminescence (CL) technique, with aCAMECA SX-50 microprobe at Institute of Geol-ogy and Geophysics, Chinese Academy of Sciences,Beijing. Operating conditions were a 15-kV accel-erating voltage and a 19-nA beam current. The CLimages were used as a guide to find appropriatespots for the laser ablation (LA-)ICP-MS analysis.U-Pb dating by the LA-ICP-MS technique was per-formed at the Key Laboratory of Crust-Mantle Ma-terials and Environments, Hefei. Zircon 91500 wasused as an external calibration standard for age cal-culation, and NIST610 was analyzed twice for ev-ery 10 analyses for concentration calculations of U,Th, and Pb. Further analytical details are given inLiu et al. (2007). U-Pb isotopic ratios were calcu-lated with the Glitter software, version 4.0, and U-Pb calculation was performed with the Isoplot pro-gram (Ludwig 2003). All errors are quoted as 2j.

Analytical Results

For the analysis of the Cu-related adakitic rocks,samples least affected by hydrothermal fluids werechosen. Under the microscope, the granitoids ex-hibit a uniform mineral assemblage, consisting ofvariable amounts of plagioclase, hornblende,quartz, K-feldspar, and biotite. Common accessoryminerals include titanite, apatite, and zircon. Darkminerals, present in almost all the samples, aremagnetite, chalcopyrite, and pyrite. Thin-sectionmicrophotographs of representative samples areshown in figure 2.

Sample FK10-155 is from the Wushan pluton (fig.2a) and displays a porphyritic texture, with phe-nocrysts forming 30–40 vol% of the rock. Majorphenocryst phases are plagioclase (55–65 vol%), bi-otite (30–40 vol%), minor hornblende (5–10 vol%),and K-feldspar (∼5 vol%), set in a very fine-grained

matrix composed of quartz (20–30 vol%), horn-blende (10–15 vol%), plagioclase (30–40 vol%), K-feldspar (10–15 vol%), and biotite (10–15 vol%).

Sample FK10-160 (Xiachaohu pluton; fig. 2b) hasa medium-grained texture and mainly comprisesplagioclase (65–75 vol%), hornblende (15–25 vol%),and minor K-feldspar (5–10 vol%). Plagioclaseshows subhedral, zonal texture and albite twins.Huge crystals of titanite (1500 mm) are frequent inthis rock.

Sample FK10-163 comes from the Fengshandongpluton (fig. 2c) and shows a porphyritic texture withphenocrysts (40–50 vol%) of plagioclase (50–60vol%), biotite (15–25 vol%), and hornblende (10–20 vol%), surrounded by a very fine-grained matrixcomposed of quartz (55–65 vol%) and plagioclase(45–55 vol%).

Sample FK10-172, which comes from the Yang-xin pluton (fig. 2d), is composed of plagioclase (45–55 vol%), hornblende (20–30 vol%), quartz (10–15vol%), and K-feldspar (10–15 vol%). Plagioclasegenerally forms subhedral crystals with polysyn-thetic twins, whereas hornblende and quartz grainsare xenomorphic.

Sample FK10-182 (fig. 2e), collected from a me-dium-grained, equigranular quartz monzonite ofthe Tonglushan pluton, is dominated by plagioclase(55–65 vol%), hornblende (15–25 vol%), K-feldspar(10–15 vol%), quartz (5–15 vol%), and rare pyrox-ene (!1 vol%). Large crystals of titanite are embed-ded in the matrix.

Sample FK10-192, from the Tongshankou pluton(fig. 2f), is a granodiorite, characterized by a por-phyritic texture. The sample contains phenocrysts(25–35 vol%) of plagioclase (65–75 vol%), horn-blende (10–20 vol%), and K-feldspar (10–15 vol%),surrounded by a very fine-grained matrix of plagio-clase (60–70 vol%), K-feldspar (10–20 vol%), quartz(10–20 vol%), biotite (5–10 vol%), and hornblende(∼5 vol%). The matrix of this sample also containslarge crystals of titanite.

Sample FK10-158, a porphyritic mafic dike in-truding the Xiachaohu pluton (fig. 2g), is gabbroicto dioritic in composition and is mainly composedof plagioclase (30–40 vol%), hornblende (35–45vol%), pyroxene (10–20 vol%), and biotite (10–15vol%). The most abundant minerals among thephenocrysts are subhedral hornblende and euhedralpyroxene.

Zircon U-Pb Ages

Zircon U-Pb isotopic data of seven samples aresummarized in table 1 (detailed analytical resultscan be obtained in table S1, available online). U-Pb

Journal of Geology P A L E O - P A C I F I C S U B D U C T I O N I N E A S T E R N C H I N A 81

Figure 2. Photomicrographs showing mineralogical and textural relationships in Cu-related adakitic rocks in theEdong-Jiurui district: Wushan (a), Xiaochaohu (b), Fengshandong (c), Yangxin (d), Tonglushan (e), Tongshankou (F),and mafic dike intruding the Wushan pluton (g).

concordia diagrams and representative CL imagesof zircons are shown in figure 3. Zircons from allsamples are colorless or transparent, have similarsubhedral to euhedral prismatic morphology, andshow typical oscillatory magmatic zoning patterns(fig. 3). U and Th contents are relatively low (Th:7.1–109 ppm; U: 8.2–86 ppm). Th/U ratios rangefrom 0.18 to 2.26, a common range for magmaticzircon. Weighted mean 206Pb/238U ages are

Ma ( , ) for the Wu-148.4 � 2.7 n p 18 MSWD p 2.1shan granodiorite, Ma ( ,149.1 � 2.1 n p 17

) for the Xiachaohu monzodiorite,MSWD p 0.87Ma ( , ) for the150.6 � 2.1 n p 22 MSWD p 0.64

Fengshandong granodiorite, Ma (139.5 � 1.4 n p, ) for the Yangxin monzonite,20 MSWD p 0.79

Ma ( , ) for the144.2 � 1.9 n p 25 MSWD p 1.8Tonglushan quartz monzonite, and Ma145.1 � 0.9

( , ) for the Tongshankoun p 25 MSWD p 1.8quartz monzonite.

Whole-Rock Geochemistry

Major- and trace-element contents are given in ta-ble A1 (tables A1–A4 available online), and theHarker variation diagrams are shown in figure 4.SiO2 varies from 54.2 to 74.5 wt%, Al2O3 from 11.6to 16.7 wt%, MgO from to 0.8 to 6.8 wt%, andTiO2 from 0.37 to 0.93 wt%. Al2O3, Fe2O3, CaO,and P2O5 decrease with increasing silica contents(fig. 4), as would be expected for fractional crystal-lization trend. The data also indicate a mainly sub-alkaline to high-K calc-alkaline composition (fig.5d). In the A/NK ( )-versus-A/Al O /[Na O � K O]2 3 2 2

CNK ( ) diagram, theAl O /[CaO � Na O � K O]2 3 2 2

82 Y . - Z . Y A N G E T A L .

Table 1. Sample Localities and Zircon U-Pb Age Data Obtained by the LA-ICP-MS Technique for the Cu-RelatedAdakitic Rocks and Mafic Dikes in the Edong-Jiurui Area

Sample Sample localityLatitude,longitude Rock type

No.analyses

U(ppm)

Th(ppm)

Th/Uratio Age (Ma)

FK10-155 Wushan 29�44′49′′N,115�38′40′′E

Granodiorite 18 33–86 19–66 .58–1.41 148.4 � 2.7

FK10-160 Xiachaohu 29�49′38′′N,115�29′58′′E

Monzodiorite 17 16–50 19–49 .75–1.02 149.1 � 2.1

FK10-161 Xiachaohu 29�49′38′′N,115�29′58′′E

Gabbroic diorite 20 15–38 10–31 .75–1.02 144.3 � 2.4

FK10-163 Fengshandong 29�49′14′′N,115�27′05′′E

Granodiorite 22 21–53 11–33 .41–.81 150.6 � 2.1

FK10-173 Yangxin 29�56′46′′N,115�02′51′′E

Monzonite 21 11–30 11–35 .60–1.35 139.5 � 1.4

FK10-182 Tonglushan 30�05′23′′N,114�56′11′′E

Quartz monzonite 25 26–62 9.4–117 .18–1.87 144.2 � 1.9

FK10-187 Tongshankou 30�00′15′′N,114�49′52′′E

Quartz monzonite 33 10–40 43–109 .20–.37 145.1 � .9

samples show metaluminous affinity (fig. 5f), andin the -versus-SiO2 diagram (fig. 5c),K O � Na O2 2

they are classified as monzodiorite, granodiorite,quartz monzodiorite, and granite. The rocks alsoshow a large variation in their Mg# (molar;

), ranging from 27 to 60, with100 # Mg/(Mg � Fe)an average of 47 (fig. 5e). Among the trace elements,the most notable features include high Sr (361–997ppm), low Y (10.5–22.4 ppm), and low Yb (0.87–1.93 ppm) concentrations, enrichment in large ionlithophile elements (LILEs; Rb, Ba, Sr) and light rareearth elements (LREEs), and depletion in high-field-strength elements (HFSEs; Nb, Ta, Zr, Hf). All sam-ples have high Sr/Y (135; fig. 5a) and high La/Yb(124) ratios (fig. 5b), and their geochemical featuresare similar to those of high-silica adakites (HSAs;Defant and Drummond 1990; Martin et al. 2005;Xie et al. 2008). All Edong-Jiurui samples possesssimilar chondrite-normalized rare earth elementpatterns without significant negative Eu anomaliesand also possess similar primitive mantle–normal-ized trace-element patterns (fig. 6), consistent withthose in the eastern MLYRB (e.g., Wang et al. 2003,2004a, 2004b, 2006a, 2006b, 2007b; Ling et al.2009; Liu et al. 2010). Compared to high-magne-sium adakitic rocks (HMAs) and low-magnesiumadakitic rocks (LMAs) from the Dabie Mountains,magmatic rocks of the Edong-Jiurui district havelower SiO2 content; higher CaO, Fe2O3, Al2O3, TiO2,and P2O5 contents; and lower Sr/Y ratios, as wellas lower Cr and Ni contents (fig. 4).

Sr-Nd-Pb Isotopic Composition

Whole-rock Rb-Sr and Sm-Nd isotopic data for themagmatic rocks from the Edong-Jiurui district aregiven in table A2, and Pb isotopic data are given in

table A3. The rocks have relatively constant Ndand Sr isotopic composition, with initial �Nd valuesbetween �3.4 and �6.3 and initial 87Sr/86Sr ratiosbetween 0.7053 and 0.7069 (fig. 7). Sm-Nd modelages (TDM) vary from 1.07 to 1.29 Ga. The Sr-Ndisotopic features are very similar to those of otherEarly Cretaceous mafic igneous rocks in the Luzongarea of the Tongling-Anqing district of the MLYRB(fig. 1a; Wang et al. 2006a; Liu et al. 2010), but showdistinctly higher �Nd(t) values and lower initial 87Sr/86Sr ratios than the adakitic rocks of the DabieMountains, shown in figure 7 (Wang et al. 2007a;Huang et al. 2008; Zhang et al. 2010; Ling et al.2011; Xu et al. 2012a, 2012b). With respect toworldwide Cenozoic slab-derived adakites, theEdong-Jiurui Cu-related rocks are shifted towardhigher Sr and lower Nd isotope ratios (fig. 7). TheEdong-Jiurui Cu-related rocks show little variationin 206Pb/204Pb (17.84–18.17), 207Pb/204Pb (15.52–15.63), and 208Pb/204Pb (38.03–38.44) ratios. Theseisotope ratios are significantly higher than those ofadakitic rocks from the Dabie Mountains (fig. 8).All samples from the Edong-Jiurui district plotabove the Northern Hemisphere Reference Line,between the Pacific mid-ocean ridge basalts(MORBs) and marine sediments/upper crust (Hof-mann 2003).

Discussion

Crystallization Ages. Zircon U-Pb ages newlypresented in this study vary between 151 and 139Ma. When published zircon U-Pb age data (tableA4; fig. 9) from the Edong-Jiurui district are in-cluded, this time period widens insignificantly, to152–136 Ma. From the existing age data, it becomesobvious that magmatism and Cu mineralization oc-

Journal of Geology P A L E O - P A C I F I C S U B D U C T I O N I N E A S T E R N C H I N A 83

Figure 3. Zircon U-Pb ages of adakitic rocks in the Edong-Jiurui district.

curred contemporaneously during Late Jurassic toEarly Cretaceous times. In numerous studies, it hasbeen pointed out that Late Mesozoic intrusionshave played a key role during the formation of por-phyry-skarn Cu deposits in the MLYRB (Sun et al.2003; Mao et al. 2006; Zhou et al. 2007; Xie et al.2007, 2011b; Li et al. 2008; Ling et al. 2009, 2011).Thus, if magmatic-hydrothermal activity is ac-cepted as the driving force for the ore deposits, thisindicates a rather protracted period of mineraliza-tion in the Edong-Jiurui district.

Recently, U-Pb zircon LA-ICP-MS ages were re-ported for mafic dikes in the Wushan deposit (Yanget al. 2011a). Their formation time indicates thatthe magmatism in this area lasted from 148 to 143Ma; a late-stage dike that yielded an age of

Ma might represent the end of magma-142.6 � 1

tism in the Wushan ore deposit. Our zircon U-Pbage of a mafic dike from the Xiachaohu Cu-bearingintrusion ( Ma; fig. 3) closely matches144.3 � 2.4this time period and possibly marks the termina-tion of magmatism and mineralization in the Xia-chaohu area. Interestingly, in the eastern part ofthe MLYRB (Tongling-Anqing district), there is lit-tle evidence for magmatic activity before 145 Ma,and mafic dikes of ∼143 Ma seem to be absent.These observations demonstrate that magmatismdeclined earlier in the Edong-Jiurui area than in theTongling-Anqing area.

A summary of zircon U-Pb ages for Cu-relatedmagmatic rocks is given in table A4. Frequencydistribution plots of zircon ages of the ore-relatedmagmatic rocks from different parts of the MLYRBshow that the peak intrusion intensity in the Tong-

Figure 4. Trace-element composition of adakitic rocks in the Edong-Jiurui district, compared with that of the Tian-tangzhai low-Mg adakitic and the Meichuan high-Mg adakitic rocks in the Dabie orogen. A color version of thisfigure is available online.

Journal of Geology P A L E O - P A C I F I C S U B D U C T I O N I N E A S T E R N C H I N A 85

Figure 5. Major-element composition of adakitic rocks in the Edong-Jiurui district, compared with that of theTiantangzhai low-Mg adakites and the Meichuan high-Mg adakites in the Dabie orogen. a, Sr/Y versus Y classification;b, (La/Yb)N versus Yb classification; c, Total alkali versus SiO2; d, K2O versus SiO2; e, Mg# versus SiO2; f, A/NK( ) versus A/CNK ( ). A color version of this figure is available online.Al O /[Na O � K O] Al O /[CaO � Na O � K O]2 3 2 2 2 3 2 2

ling-Anqing area (∼140 Ma; fig. 9d) outlasted thatin the Edong-Jiurui area (∼145 Ma; fig. 9c) by ∼5m.yr. If mineralization was directly related to ig-neous activity, this implies a gradual shift of theore-forming fluids from west (Edong-Jiurui) to east(Tongling-Anqing) in the MLYRB. The U-Pb zirconages of the Fe-related intrusions, such as theEcheng, Tieshan, Wangbaoshan, Jinshandian, andLingxiang diorite to quartz-diorite plutons from theEdong-Jiurui district, vary between 141 and 121 Ma

(fig. 9a), indicating that the hydrothermal activityrelated to Fe mineralization clearly postdates thedeposition of the Cu minerals.

Geochemical and Isotopic Characteristics. The Cu-related magmatic rocks in the Edong-Jiurui districthave diagnostic features of adakites (HSAs; Martin2005). These include high SiO2, Na2O, Al2O3, andSr contents, low MgO, Y, and Yb contents, and highSr/Y and La/Yb ratios. Like adakites, they alsoshow enrichment of LILEs (Rb, Ba, Sr) and LREEs,

86 Y . - Z . Y A N G E T A L .

Figure 6. Trace-element diagrams for the Tiantangzhai low-Mg adakitic, Meichuan high-Mg adakitic, and Edong-Jiurui adakitic rocks.

depletion of HFSEs (Nb, Ta, Zr, Hf, Ti), and no dis-cernible negative Eu anomaly. To account for theadakitic characteristics of Mesozoic rocks from theMLYRB and the Dabie Mountains, several differentmodels have been invoked. These include (1) partialmelting of delaminated Yangtze lower continentalcrust (Zhang et al. 2001; Wang et al. 2007b), (2)assimilation and fractional crystallization pro-cesses of fertile mantle material (Chen and Jahn1998; Mao et al. 2006; Xie et al. 2008, 2011b; Li etal. 2009b), and (3) partial melting of an oceanicridge basalt whereby the melt was modified by ma-terial from an enriched-mantle source and/or bycontinental crust (Ling et al. 2009, 2011; Liu et al.2010; Sun et al. 2010).

The Cu-related adakitic rocks in the Edong-Jiuruidistrict define a trend in geochemical composition(fig. 4), possibly indicating fractional crystallization.Sr and Eu concentrations in the Edong-Jiurui plutonsdecrease with increasing silica (fig. 10), suggestingfeldspar fractionation during magma evolution. Frac-tionation trends are also seen in the La/Sm-versus-La and initial 87Sr/86Sr-versus-1/Sr diagrams (fig. 11).Assimilation of country rocks by the magma cannotbe observed based on �Nd(t) values, and initial 87Sr/86Sr ratios show no obviously linear with the recip-rocal of their concentration (fig. 11a).

Contamination by continental crust is unavoid-able, as the adakitic melts must transport at least30 km of the continental crust, but there is no evi-

dence for a large extent of crust contamination dur-ing the formation of the Cu-related adakitic rocksin the Edong-Jiurui area. Such contaminationwould produce positive Zr-Hf anomalies (e.g., Sunand McDonough 1989), but there are no or onlyslightly negative Zr-Hf anomalies of the Cu-relatedplutons in the Edong-Jiurui area (fig. 6). In addition,the confirmed fact that few inherited zircons havebeen reported is also evidence. The fractional crys-tallization process is common during magmaticevolutions, but the basic rocks cannot be the originof the Cu-related rocks in the Edong-Jiurui area.First, some geochemical characteristics of the gran-itoids are consistent with derivation from maficprotolith, but basic rocks make up a minor part ofthe igneous rocks of the Edong-Jiurui district. Sec-ond, recent high-precision U-Pb zircon dating con-firmed that basaltic igneous rocks were formed inthe late stage (Yang et al. 2011a), so it is inconsis-tent with a fractional crystallization trend. Third,geochemical features typical of adakitic rocks (e.g.,Sr/Y ratio) remain nearly unchanged with increasesin major oxides, such as SiO2 and TiO2 (fig. 4f). Tosummarize, fractional crystallization from maficprecursor rocks cannot account for the adakiticcharacters of the Cu-related rocks in the Edong-Jiurui area and their geochemical features shouldbe produced in the source area.

Comparison with Dabie Adakites. On the basis oftrace-element composition, it has been suggested

Journal of Geology P A L E O - P A C I F I C S U B D U C T I O N I N E A S T E R N C H I N A 87

Figure 7. Initial �Nd value versus initial 87Sr/86Sr ratio of adakitic rocks in the Edong-Jiurui district. Fields for Cenozoicslab-derived adakites (Defant and Kepezhinskas 2001), Dabie high-Mg adakitic rocks (Xu et al. 2012b), Dabie low-Mg adakitic rocks (Xu et al. 2012a), and Early Cretaceous mafic igneous rocks in the middle-lower Yangtze Riverbelt (MLYRB; Yan et al. 2008; Liu et al. 2010) are shown for comparison. The field for mafic dikes in the MLYRB isbased on data from Wang et al. (2004b) and Li et al. (2008). The field for mid-ocean ridge basalt (MORB) and marinesediments is after Hofmann (1988, 2003), that for the Yangtze lower crust is after Jahn et al. (1999), and that for theYangtze upper crust is after Chen and Jahn (1998). A color version of this figure is available online.

that adakites in the Dabie orogen (Tiantangzhai,Meichuan) are different from the ore-related mag-matic rocks in the MLYRB (Liu et al. 2010; Ling etal. 2011; Sun et al. 2012a, 2012b). It has been arguedthat the Tiantangzhai LMAs were derived fromthickened Yangtze lower continental crust,whereas the Meichuan HMAs have been inter-preted as products of partial melting of delaminatedYangtze lower continental crust and mantle peri-dotite (Zhang et al. 2010; He et al. 2011; Xu et al.2012a, 2012b).

Compared to the Dabie adakites, Cu-relatedadakitic rocks in the Edong-Jiurui district showlarger variation in major-element content and Mg#(27–60) as well as lower Cr and Ni contents andlower Sr/Y ratios (fig. 4). As seen in the MgO-versus-SiO2 diagram (fig. 12), the magmatic rocksin the Edong-Jiurui district extend to lower SiO2

abundances. Almost all Edong-Jiurui rocks plot in

the field of adakites related to slab melting andmantle wedge interaction, as defined by Defant andKepezhinskas (2001). This strongly argues againsta crustal origin. In the Nb/Ta-versus-Zr/Sm dia-gram (fig. 13a), the Edong-Jiurui rocks plot in orclose to the area of Cenozoic adakites that origi-nated from slab melting (Condie 2005). On theother hand, the Dabie adakitic rocks have com-positional features in common with Archean to-nalite-trondhjemite-granodiorite (fig. 12).

It is widely accepted that the adakitic characteris indicative of garnet in the slab or mantle wedgesource, but other minerals, such as amphibole, canalso produce high Sr/Y and La/Yb ratios. The Tian-tangzhai LMAs and Meichuan HMAs originatedfrom a source in which garnet was a residual min-eral phase. On the basis of the (Dy/Yb)N-versus-(La/Yb)N relationship (fig. 13b), the adakitic characterof the Edong-Jiurui rocks can likewise be attributed

88 Y . - Z . Y A N G E T A L .

Figure 8. a, b, Pb isotopic composition of adakitic rocks in the Edong-Jiurui district, including three analyses ofmafic rocks from Xie et al. (2011b). c, Th/Yb-versus-Th/Sm diagram. d, Pb/Ce-versus-207Pb/204Pb diagram. Data forglobal subducting sediment (GLOSS) and mid-ocean ridge basalt (MORB) are from Rehkamper and Hofmann (1997)and Plank and Langmuir (1998); data for N-type MORB are from Sun and McDonough (1989); data for Dabie adakiticrocks are from Zhang et al. (2002). Ave. crust p average continental crust; HMA p high-magnesium adakitic rocks;LCC p lower continental crust; NHRL p Northern Hemisphere Reference Line (Hart 1984); BSE p bulk silicateEarth. A color version of this figure is available online.

to residual amphibole in the source. The Cu-relatedmagmatic rocks in the Edong-Jiurui area fall in thefield of garnet amphibolites (fig. 13c, 13d), with Yconcentrations between 10.5 and 22.4 ppm, Zr/Smratios between 23 and 36, and Sm/Yb ratios be-tween 3.6 and 5.7. The Tiantangzhai LMAs and theMeichuan HMAs have lower Y contents (Tian-tangzhai LMAs: 7.3–19 ppm; Meichuan HMAs:3.7–12.3 ppm), consistent with derivation from adry residual eclogite-facies protolith (e.g., Rapp etal. 1999; Kay and Mpodozis 2001).

Origin of the Cu-Related Adakitic Rocks. The Cu-related adakitic rocks from the Edong-Jiurui districthave features in common with adakites from slabmelting and are different from those of the DabieMountains. Their depletion in Zr and Hf relative

to Nd and Sm (fig. 6) is difficult to explain by min-eral fractionation alone. The more likely explana-tion is that these features reflect source informa-tion. Zr/Hf ratios of the Edong-Jiurui rocks (37.4–43.4) are close to those of MORBs (40.1; Kelemenet al. 2004), slightly higher than those in the prim-itive mantle (36.3), and very different from thosein continental crust (∼11; Sun and McDonough1989). Their siderophile element concentrations,such as Cr and Ni, differ from those in the primitivemantle but are in the range of those in MORBs.

In the primitive mantle–normalized element pat-terns, the Edong-Jiurui rocks exhibit considerableenrichment in LILEs and negative Nb-Ta anomalies(fig. 6), similar to magmas generated in a subduc-tion zone tectonic setting. Ling et al. (2009) have

Journal of Geology P A L E O - P A C I F I C S U B D U C T I O N I N E A S T E R N C H I N A 89

Figure 9. a, Statistic graphs of the time of Cu and Fe mineralization in the Edong-Jiurui district. The compilationincludes Re-Os ages on molybdenite for Cu deposits and 40Ar-39Ar ages on albite for Fe deposits. Data are from Maoet al. (2006), Xie et al. (2007), and Li et al. (2008). b, Statistic graphs of the time of Cu-related magmatic rocks andFe-related magmatic rocks in the Edong-Jiurui district. Data are from Xie et al. (2011b) and references therein. c, d,Statistic graphs of Cu-related magmatic rocks in the Edong-Jiurui and Tongling-Anqing areas, respectively. Data arein table A4, available online. A color version of this figure is available online.

proposed that slab-derived fluids and partial meltsfrom subducted sediments have metasomatized thesource region of the magmas in the MLYRB (Li etal. 2009b; Liu et al. 2010). Slab-derived fluids havehigh concentrations of Ba, Rb, Sr, U, and Pb,whereas partial melts of subducted sediments areenriched in Th and LREEs (Hawkesworth andKemp 2006). Lavas from modern arc settings withsediment transfer typically show Th/Yb ratios of atleast 2, whereas fluid-dominated arcs are charac-terized by Th/Yb ratios of less than 1 (Woodheadet al. 2001; Nebel et al. 2007). Thus, high Th/Ybratios in the Edong-Jiurui rocks (3.9–19.1) providesome evidence that the granitoids contain a recy-cled sediment component.

The Pb/Ce ratio is not significantly changed bymagmatic processes such as partial melting andfractional crystallization (Miller et al. 1994). Also,this ratio is a particularly useful indicator of thepresence of sediments or average crust (White andDuncan 1996). Sediments have 2-orders-of-magni-tude-higher concentrations of Pb (typically 20 ppmor more) than the mantle (!1 ppm), so addition ofeven small amounts of sediments to mantle shiftsthe Pb/Ce toward higher ratios. Consequently, con-tinental crust has higher Pb/Ce (∼0.2–0.25; Taylorand McLennan 1985; Miller et al. 1994; Rudnickand Gao 2003) than oceanic crust (∼0.04; Sun andMcDonough 1989). Sediments also have higher207Pb/204Pb ratios than average continental crust (fig.

90 Y . - Z . Y A N G E T A L .

Figure 10. Sr-versus-SiO2 (a) and Eu-versus-SiO2 (b) content diagrams for the adakitic rocks in the Edong-Jiuruidistrict. A color version of this figure is available online.

Figure 11. Initial 87Sr/86Sr ratio–versus-1/Sr (#105) (a) and La/Sm-versus-La (b) diagrams for Cu-related adakitic rocksin the Edong-Jiurui district. Additional 87Sr/86Sr data are from Wang et al. (2004b), Xie et al. (2008), and Li et al.(2009b).

8d). In the Pb/Ce-versus-207Pb/204Pb diagram (fig.8d), the Edong-Jiurui rocks are displaced from theDabie adakitic rocks toward lower Pb/Ce ratios andhigher 207Pb/204Pb ratios. Note that lower continen-tal crust would have higher Pb/Ce ratios and lower207Pb /204Pb ratios. On the basis of their isotope char-acteristics, the Edong-Jiurui rocks can be charac-terized as a mixture of MORB and marine sedimentcomposition. Upper-crustal material assimilationcan also produce these characters (fig. 8c), but arecent study on the magmatic d18O versus initial87Sr/86Sr of these adakitic rocks, for comparisonwith Setouchi lavas (Shimoda et al. 1998; Bindemanet al. 2005), shows a coherent positive correlationin the field for source contamination (Li et al. 2013),

illustrating that upper crust has just a limited con-tribution during the formation of the Cu-relatedrocks in the Edong-Jiurui area. Similar conclusionscan be drawn from the Nb/U ratios (2.7–8.5; tableA1). In the �Nd-versus-87Sr/86Sr diagram (fig. 7), theEdong-Jiurui rocks and mafic dikes display similarisotopic features and also plot between the fieldsof MORB and marine sediments.

When slab melts migrate upward to the litho-spheric mantle, the melts should interact withmantle peridotite. It has been proved that the SiO2

content of slab melts decreases significantly oncethe degree of the interaction exceeds about 15%(Rapp et al. 1999), but even a small degree of in-teraction can increase Mg# values dramatically,

Journal of Geology P A L E O - P A C I F I C S U B D U C T I O N I N E A S T E R N C H I N A 91

Figure 12. MgO-versus-SiO2 diagram for adakitic rocks in the Edong-Jiurui district and low- and high-Mg adakiticrocks in the Dabie orogen. Symbols are as in figure 4. TTG p tonalite-trondhjemite-granodiorite. A color version ofthis figure is available online.

while decreasing SiO2 slightly. This relationship be-tween SiO2 contents and Mg# cannot be observedin the Edong-Jiurui adakitic rocks (fig. 5e). Theirlow Cr and Ni contents (fig. 4g, 4h) also indicate asmall degree of interaction of mantle peridotitewith most of the adakitic melts in the Edong-Jiuruiarea.

In conclusion, the origin of the magmatic rocksfrom the Edong-Jiurui district is best explained bymelting of the down-going slab. When the meltsmoved upward to the earth’s surface, the assimi-lation and fractional crystallization processes ofboth continental crust contamination and slab-melt interaction with lithospheric mantle shouldhave disturbed the Cu-related rocks in the Edong-Jiurui area only a little. During the transition fromamphibolite facies to eclogite facies, the release ofwater triggered melting of the slab, and these meltsand associated fluids transported the metals, whichconstitute the mineralization in the MLYRB.

Geodynamic Model. The term adakite was intro-duced for rocks derived by partial melting of sub-ducting oceanic crust (Defant and Drummond1990). Experimental work has shown that adakite-like melts are produced by partial melting of am-phibolites (metabasalt) in the garnet stability fieldunder water-saturated conditions or by dehydrationmelting of amphibolites (Beard and Lofgren 1989,1991; Wolf and Wyllie 1991; Winther and Newton1992; Sen and Dunn 1994; Rapp et al. 1999; Castillo2012). However, there is still controversy surround-ing the issues of the origin of the “adakitic signa-ture” and the geotectonic background and viableproduction modes for adakites (Muir et al. 1995;Barnes et al. 1996; Martin et al. 2005; Ickert et al.2009).

Beginning in the early Jurassic, eastern Chinagradually became an active continental margin, as-sociated with subduction of the paleo–Pacific Plate(Zhu 1998; Sun et al. 2007; Ling et al. 2009). The

92 Y . - Z . Y A N G E T A L .

Figure 13. Nb/Ta-versus-Zr/Sm diagram (a), Dy/Yb N-versus-La/Yb N diagram (b), Zr/Sm-versus–Y content plot (c),and Sm/Yb-versus–Y content plot (d) for adakitic rocks from the Edong-Jiurui district and the Tiantangzhai low-Maand Meichuan high-Ma adakitic rocks in the Dabie orogen. Arrows indicate the influence of residual hornblende andpressure on the composition of the adakitic magmas. Lines in c and d are from Hou et al. (2011). Amph p amphibole;Grt p garnet. A color version of this figure is available online.

Edong-Jiurui district is located in the west of theMLYRB. The plutons form a curved belt along thesouthern margin of the Dabie orogenic belt thatwould be consistent with a northwest-directed sub-duction system (fig. 1a). The geochemical and iso-topic signatures of the Cu-related magmatic rockscan be best interpreted as melting of MORB-typebasalts and sediments from the paleo–Pacific slab.A compilation of geochronological results includ-ing magmatic rocks from the western (Edong-Jiurui) and eastern (Tongling-Anqing) parts of theMLYRB shows that the focus of magmatic activitymoved from west to east between 145 and 140 Ma(fig. 9). This shift can be accounted for by a changein subduction angle of the paleo–Pacific slab (fig.14).

The Sr-Nd isotopic composition of the adakiticrocks in the study area is clearly more primitive

than that of the HMAs and LMAs in the Dabieorogenic belt, which are, in turn, geochemicallymore akin to the Yangtze lower crust (fig. 7). Thus,it seems likely that the Dabie HMAs and LMAsformed in a completely different tectonic setting,probably related to postorogenic extension of theDabie crust.

On the basis of these observations, the followingtectonic model is proposed for the petrogenesis ofthe Edong-Jiurui adakites (fig. 14). During the Ju-rassic, oceanic crust from the paleo–Pacific Platewas subducted beneath the Yangtze block (Zhouand Li 2000; Li and Li 2007). In an early stage oflow-angle/flat subduction (fig. 14a), adakitic meltswere produced from the down-going slab (Gutscheret al. 2000). The melts had high water content andoxygen fugacity that prevailed in the melts, givingrise to the release of significant amount of copper-

Figure 14. Tectonic model for the formation of the adakitic rocks in the Edong-Jiurui district. a, Flat (low-angle)subduction of the hot and buoyant paleo–Pacific Plate beneath the Yangtze (South China) craton resulted in meltingof the plate and overlying sediments and production of adakites around 155–140 Ma. b, Increasing subduction anglecaused an eastward shift of magmatism from the Eong-Jiurui area toward the Tongling-Anqing area around 140–135Ma. c, Between 135 and 120 Ma, a phase of extension caused pressure release in the crust and lithospheric mantle.The lithospheric mantle beneath the Edong-Jiurui area was metasomatized by the adakitic melts, and finally, hydro-thermal solutions associated with the magmas mobilized iron in high concentration, giving rise to the Fe ore deposits.MLYRB p middle-lower Yangtze River belt; MORB p mid-ocean ridge basalt.

94 Y . - Z . Y A N G E T A L .

and gold-bearing sulfides from the subductingmetabasalts or surrounding mantle. These ele-ments contributed to the mineralization in theEdong-Jiurui area, which started around 152 Ma.As the subducting slab changed from amphibolitefacies to eclogite facies, its density increased andit became less buoyant (fig. 14b). The subductionangle increased and shortened the arc-trench dis-tance, resulting in a shift of the magmatic activityfrom west to east into the Tongling-Anqing areaaround 145–140 Ma. The geodynamic environmentof the MLYRB changed from compression to exten-sion, causing pressure release in the crust and litho-spheric mantle during the Early Cretaceous (Changet al. 1991; Li et al. 2008; fig. 14c). Melting of apreviously metasomatized subcontinental litho-spheric mantle gave rise to Fe-rich magmatism inareas of weakened crust (Jinniu, Huaining, Luzong,and Ningwu basins) within the MLYRB.

Conclusions

Adakites with copper-style mineralization of theEdong-Jiurui district formed between 152 and 139Ma, during subduction-related magmatism. Thechronological results exhibit a shift in the peak ofmagmatism from west (∼145 Ma, Edong-Jiurui area)to east (∼140 Ma, Anqing-Tongling area). The ada-

kitic rocks show little evidence of contaminationby ancient arc crust and portray a magmatic frac-tional crystallization trend. It is concluded that theadakitic character bears the fingerprint of thesource area. A garnet-amphibolite source rock isenvisaged for the Edong-Jiurui adakites, whereasthe Tiantangzhai LMAs and the Meichuan HMAsin the Dabie orogen contain material from theYangtze lower continental crust. The adakitic rocksin the Edong-Jiurui area were derived from theyoung and newly subducted paleo–Pacific slab andoverlying sediments during amphibolite–eclogitefacies transition. Igneous rocks that host iron orebodies are younger (135–120 Ma) and formed afterrollback of the paleo–Pacific Plate by partial melt-ing of the lithospheric mantle metasomatized byslab-derived fluids or adakitic melts.

A C K N O W L E D G M E N T S

This study was supported by the National NaturalScience Foundation of China (41090372, 41372072,and 40973042) and by the Chinese Academy of Sci-ences Visiting Professorship for Senior Interna-tional Scientists (grant 2011T2S39). Thanks are dueto P. Xiao and J.-F. He for help with analysis ofisotope data and to F.-Y. Wang for fruitfuldiscussions.

R E F E R E N C E S C I T E D

Barnes, C. G.; Petersen, S. W.; Kistler, R. W.; Murray, R.;and Kays, M. A. 1996. Source and tectonic implica-tions of tonalite-trondhjemite magmatism in theKlamath Mountains. Contrib. Mineral. Petrol. 123:40–60.

Beard, J. S., and Lofgren, G. E. 1989. Effect of water onthe composition of partial melts of greenstones andamphibolites. Science 144:195–197.

———. 1991. Dehydration melting and water-saturatedmelting of basaltic and andesitic greenstones and am-phibolites at 1, 3 and 6.9 kb. J. Petrol. 32:465–501.

Bindeman, I. N.; Eiler, J. M.; Yogodzinski, G. M.; Tat-sumi, Y.; Stern, C. R.; Grove, T. L.; Portnyagin, M.;Hoernle, K.; and Danyushevsky, L. V. 2005. Oxygenisotope evidence for slab-derived in modern and an-cient subduction zones. Earth Planet. Sci. Lett. 235:480–496.

Castillo, P. R. 2012. Adakite petrogenesis. Lithos 134–135:304–316.

Chang, Y. F.; Liu, X. P.; and Wu, Y. C. 1991. The copper-iron belt of the lower and middle reaches of the Chang-jiang River. Beijing, Geological Publishing (in Chinesewith English abstract).

Chen, F.; Hegner, E.; and Todt, W. 2000. Zircon ages andNd isotopic and chemical compositions of ortho-gneisses from the Black Forest, Germany: evidence for

a Cambrian magmatic arc. Int. J. Earth Sci. 88:791–802.

Chen, F.; Li, X. H.; Wang, X. L.; Li, Q. L.; and Siebel, W.2007. Zircon age and Nd-Hf isotopic composition ofthe Yunnan Tethyan belt, southwestern China. Int. J.Earth Sci. 96:1179–1194.

Chen, J. F., and Jahn, B. M. 1998. Crustal evolution ofsoutheastern China: Nd and Sr isotopic evidence. Tec-tonophysics 284:101–133.

Condie, K. C. 2005. TTGs and adakites: are they bothslab melts? Lithos 80:33–44.

Defant, M. J., and Drummond, M. S. 1990. Derivation ofsome modern arc magmas by melting of young sub-ducted lithosphere. Nature 347:662–665.

Defant, M. J., and Kepezhinskas, P. 2001. Evidence sug-gests slab melting in arc magmas. EOS: Trans. Am.Geophys. Union 82:62–69.

Gao, S.; Zhang, B.; Gu, X.; Xie, Q.; Gao, C.; and Guo, X.1995. Silurian–Devonian provenance changes of SouthQinling basins: implications for accretion of the Yang-tze (South China) to the North China Craton. Tec-tonophysics 250:183–197.

Gutscher, M. A.; Maury, R.; Eissen, J.; and Bourdon, E.2000. Can slab melting be caused by flat subduction?Geology 28:535–538.

Journal of Geology P A L E O - P A C I F I C S U B D U C T I O N I N E A S T E R N C H I N A 95

Hart, S. R. 1984. A large-scale isotopic anomaly in theSouthern Hemisphere mantle. Nature 309:753–757.

Hawkesworth, C. J., and Kemp, A. I. S. 2006. Using haf-nium and oxygen isotopes in zircons to unravel therecord of crustal evolution. Chem. Geol. 226:144–162.

He, Y. S.; Li, S. G.; Hoefs, J.; Huang, F.; Liu, S. A.; andHou, Z. H. 2011. Post-collisional granitoids from theDabie orogen: new evidence for partial melting of athickened continental crust. Geochim. Cosmochim.Acta 75:3815–3838.

Hofmann, A. W. 1988. Chemical differentiation of theEarth: the relationships between mantle, continentalcrust, and oceanic crust. Earth Planet. Sci. Lett. 90:297–314.

———. 2003. Sampling mantle heterogeneity throughoceanic basalts: isotopes and trace elements. In Carl-son, R. W., ed. Treatise on geochemistry. Vol. 2. Themantle and core. London, Elsevier, p. 61–101.

Hou, Z.; Zhang, H.; Pan, X.; and Yang, Z. 2011. PorphyryCu(-Mo-Au) deposits related to melting of thickenedmafic lower crust: examples from the eastern Tethyanmetallogenic domain. Ore Geol. Rev. 39:21–45.

Huang, F.; Li, S. G.; Dong, F.; He, Y. S.; and Chen, F. 2008.High-Mg adakitic rocks in the Dabie orogen, centralChina: implications for foundering mechanism oflower continental crust. Chem. Geol. 255:1–13.

Ickert, R. B.; Thorkelson, D. J.; Marshall, D. D.; and Ull-rich, T. D. 2009. Eocene adakitic volcanism in south-ern British Columbia: remelting of arc basalt above aslab window. Tectonophysics 464:164–185.

Jahn, B. M.; Wu, F. Y.; Lo, C. H.; and Tsai, C. H. 1999.Crust-mantle interaction induced by deep subductionof the continental crust: geochemical and Sr-Nd iso-topic evidence from post-collisional mafic-ultramaficintrusions of the northern Dabie complex, centralChina. Chem. Geol. 157:119–146.

Kay, S. M., and Mpodozis, C. 2001. Central Andean oredeposits linked to evolving shallow subduction sys-tems and thickening crust. GSA Today 11:4–9.

Kelemen, P. B.; Hanghoj, K.; and Greene, A. R. 2004. Oneview of the geochemistry of subduction-related mag-matic arcs, with an emphasis on primitive andesiteand lower crust. In Rudnick, R. L., ed. Treatise ongeochemistry. Vol. 3. The crust. Amsterdam, Elsevier,p. 593–659.

Li, H.; Ling, M. X.; Li, C. Y.; Zhang, H.; Ding, X.; Yang,X. Y.; Fan, W. M.; Li, Y. L.; and Sun, W. D. 2012. A-type granite belts of two chemical subgroups in centraleastern China: indication of ridge subduction. Lithos150:26–36.

Li, H.; Zhang, H.; Ling, M. X.; Wang, F. Y.; Ding, X.; Zhou,J. B.; Yang, X. Y.; Tu, X. L.; and Sun, W. D. 2011.Geochemical and zircon U-Pb study of the Huang-meijian A-type granite: implications for geologicalevolution of the Lower Yangtze River belt. Int. Geol.Rev. 53:499–525.

Li, J. W.; Zhao, X. F.; Zhou, M. F.; Ma, C. Q.; de Souza,Z. S.; and Vasconcelos, P. 2009b. Late Mesozoic mag-matism from the Daye region, eastern China: U-Pb

ages, petrogenesis, and geodynamics implications.Contrib. Mineral. Petrol. 157:383–409.

Li, J. W.; Zhao, X. F.; Zhou, M. F.; Vasconcelos, P.; Ma,C. Q.; Deng, X. D.; Zhao, Y. X.; and Wu, G. 2008.Origin of the Tongshankou porphyry-skarn Cu-Mo de-posit, eastern Yangtze craton, eastern China: geochro-nological, geochemical, and Sr-Nd-Hf isotopic con-straints. Mineral Depos. 43:319–336.

Li, S. G.; Jagoutz, E.; Chen, Y. Z.; and Li, Q. L. 2000. Sm-Nd and Rb-Sr isotopic chronology and cooling historyof ultrahigh pressure metamorphic rocks and theircountry rocks at Shuanghe in the Dabie Mountains,central China. Geochim. Cosmochim. Acta 64:1077–1093.

Li, X. H.; Li, W. X.; Wang, X. C.; Li, Q. L.; Liu, Y.; Tang,G. Q.; Gao, Y. Y.; and Wu, F. Y. 2010b. SIMS U-Pbzircon geochronology of porphyry Cu-Au-(Mo) depos-its in the Yangtze river metallogenic belt, easternChina: magmatic response to early Cretaceous lith-ospheric extension. Lithos 119:427–438.

Li, X. H.; Li, Z. X.; Li, W. X.; Wang, X. C.; and Gao, Y.2013. Revisiting the “C-type adakites” of the LowerYangtze River Belt, central eastern China: in-situ zir-con Hf -O isotope and geochemical constraints. Chem.Geol. 345:1–15.

Li, Z. X., and Li, X. H. 2007. Formation of the 1300-km-wide intracontinental orogen and postorogenic mag-matic province in Mesozoic South China: a flat-slabsubduction model. Geology 35:179–182.

Ling, M. X.; Wang, F. Y.; Ding, X.; Hu, Y. H.; Zhou, J. B.;Zartman, R. E.; Yang, X. Y.; and Sun, W. D. 2009.Cretaceous ridge subduction along the lower Yangtzeriver belt, eastern China. Econ. Geol. 104:303–321.

Ling, M. X.; Wang, F. Y.; Ding, X.; Zhou, J. B.; and Sun,W. D. 2011. Different origins of adakites from the Da-bie Mountains and the Lower Yangtze River belt ineastern China: geochemical constraints. Int. Geol.Rev. 53:727–740.

Liu, S. A.; Li, S. G.; He, Y. S.; and Huang, F. 2010. Geo-chemical contrasts between early Cretaceous ore-bearing and ore-barren high-Mg adakites in central-eastern China: implications for petrogenesis andCu-Au mineralization. Geochim. Cosmochim. Acta74:7160–7178.

Liu, X. M.; Gao, S.; Diwu, C. R.; Yuan, H. L.; and Hu, Z.C. 2007. Simultaneous in-situ determination of U-Pbage and trace elements in zircon by LA-ICP-MS in 20-mm spot size. Chin. Sci. Bull. 52:1257–1264.

Ludwig, K. R. 2003. Isoplot/Ex, version 3: a geochrono-logical toolkit for Microsoft Excel. Special publication1a. Berkeley, CA, Berkeley Geochronology Center.

Ma, C. Q.; Yang, K. G.; Ming, H. L.; and Lin, G. C. 2004.The timing of tectonic transition from compressionto extension in Dabieshan: evidence from Mesozoicgranites. Sci. China (D) 47:453–462.

Mao, J. W.; Wang, Y. T.; Lehmann, B.; Yu, J. J.; Du, A. D.;Mei, Y. X.; Li, Y. F.; Zhang, W. S.; Stein, H. J.; andZhou, T. F. 2006. Molybdenite Re-Os and albite 40Ar/39Ar dating of Cu-Au-Mo and magnetite porphyry sys-

96 Y . - Z . Y A N G E T A L .

tems in the Yangtze River valley and metallogenicimplications. Ore Geol. Rev. 29:307–324.

Martin, H.; Smithies, R. H.; Rapp, R.; Moyen, J. F.; andChampion, D. 2005. An overview of adakite, tonalite-trondhjemite-granodiorite (TTG), and sanukitoid: re-lationships and some implications for crustal evolu-tion. Lithos 79:1–24.

Miller, D. M.; Goldstein, S. L.; and Langmuir, C. H. 1994.Cerium/lead and lead isotope ratios in arc magmasand the enrichment of lead in the continents. Nature368:514–520.

Muir, R. J.; Weaver, S. D.; Bradshaw, J. D.; Eby, G. N.;and Evans, J. A. 1995. The Cretaceous SeparationPoint batholith, New Zealand: granitoid magmasformed by melting of mafic lithosphere. J. Geol. Soc.Lond. 152:689–701.

Nebel, O.; Munker, C.; Nebel-Jacobsen, Y. J.; Kleine, T.;Mezger, K.; and Mortimer, N. 2007. Hf-Nd-Pb isotopeevidence from Permian arc rocks for the long-termpresence of the Indian-Pacific mantle boundary in theSW Pacific. Earth Planet. Sci. Lett. 254:377–392.

Pan, Y., and Dong, P. 1999. The Lower Changjiang (Yang-tze River) metallogenic belt, east China: intrusion-and wall rock-hosted Cu-Fe-Au, Mo, Zn, Pb, Ag de-posits. Ore Geol. Rev. 15:177–242.

Plank, T., and Langmuir, C. H. 1998. The chemical com-position of subducting sediments and its conse-quences for the crust and mantle. Chem. Geol. 145:325–394.

Rapp, R. P.; Shimizu, N.; Norman, M. D.; and Applegate,G. S. 1999. Reaction between slab-derived melts andperidotite in the mantle wedge: experimental con-straints at 3.8 GPa. Chem. Geol. 160:335–356.

Rehkamper, M., and Hofmann, A. W. 1997. Recycledocean crust and sediments in Indian Ocean MORB.Earth Planet. Sci. Lett. 147:93–106.

Rudnick, R. L., and Gao, S. 2003. Composition of thecontinental crust. In Rudnick, R. L., ed. Treatise ongeochemistry. Vol. 3. The crust. Amsterdam, Elsevier,p. 1–64.

Sen, C., and Dunn, T. 1994. Dehydration melting of abasaltic composition amphibolite at 1.5 and 2.0 GPa:implications for the origin of adakites. Contrib. Min-eral. Petrol. 117:394–409.

Shimoda, G.; Tatsumi, Y.; Nohda, S.; Ishizaka, K.; andJahn, B. M. 1998. Setouchi high-Mg andesites revis-ited: geochemical evidence for melting of subductingsediments. Earth Planet. Sci. Lett. 160:479–492.

Shu, Q. A.; Chen, P. L.; and Cheng, J. R. 1992. Geologyof iron-copper deposits in eastern Hubei Province,China. Beijing, Ministry of the Metallurgic Industry(in Chinese with English abstract).

Sun, S. S., and McDonough, W. 1989. Chemical and iso-topic systematics of oceanic basalt: implications formantle composition and processes. In Saunders, A. D.,and Norry, M. J., eds. Magmatism in the ocean basins.Geol. Soc. Spec. Publ. 42:313–345.

Sun, W. D.; Ding, X.; Hu, Y. H.; and Li, X. H. 2007. Thegolden transformation of the Cretaceous plate sub-

duction in the west Pacific. Earth Planet. Sci. Lett.262:533–542.

Sun, W. D.; Ling, M. X.; Chung, S. L.; Ding, X.; Yang, X.Y.; Liang, H. Y.; Fan, W. M.; Goldfarb, R.; and Yin, Q.Z. 2012a. Geochemical constraints on adakites of dif-ferent origins and copper mineralization. J. Geol. 120:105–120.

Sun, W. D.; Ling, M. X.; Yang, X. Y.; Fan, W. M.; Ding,X.; and Liang, H. Y. 2010. Ridge subduction and por-phyry copper gold mineralization. Sci. China (D) 53:475–484.

Sun, W. D.; Xie, Z.; Chen, J. F.; Zhang, X.; Chai, Z. F.;Du, A. D.; Zhao, J. S.; Zhang, C. H.; and Zhou, T. F.2003. Os-Os dating of copper and molybdenum de-posits along the middle and lower reaches of the Yang-tze River, China. Econ. Geol. 98:175–180.

Sun, W. D.; Yang, X. Y.; Fan, W. M.; and Wu, F. Y. 2012b.Mesozoic large scale magmatism and mineralizationin south China: Preface. Lithos 150:1–5.

Taylor, S. R., and McLennan, S. M. 1985. The continentalcrust: its composition and evolution. Oxford,Blackwell.

Wang, Q.; Wyman, D. A.; Xu, J.; Jian, P.; Zhao, Z.; Li, C.;Xu, W.; Ma, J.; and He, B. 2007a. Early Cretaceousadakitic granites in the Northern Dabie Complex,central China: implications for partial melting and de-lamination of thickened lower crust. Geochim. Cos-mochim. Acta 71:2609–2636.

Wang, Q.; Wyman, D. A.; Xu, J. F.; Zhao, Z. H.; Jian, P.;Xiong, X. L.; Bao, Z. W.; Li, C. F.; and Bai, Z. H. 2006a.Petrogenesis of Cretaceous adakitic and shoshoniticigneous rocks in the Luzong area, Anhui Province(eastern China): implications for geodynamics and Cu-Au mineralization. Lithos 89:424–446.

Wang, Q.; Wyman, D. A.; Xu, J. F.; Zhao, Z. H.; Jian, P.;and Zi, F. 2007b. Partial melting of thickened or de-laminated lower crust in the middle of eastern China:implications for Cu-Au mineralization. J. Geol. 115:149–161.

Wang, Q.; Xu, J. F.; Jian, P.; Bao, Z. W.; Zhao, Z. H.; Li,C. F.; Xiong, X. L.; and Ma, J. L. 2006b. Petrogenesisof adakitic porphyries in an extensional tectonic set-ting, Dexing, south China: implications for the genesisof porphyry copper mineralization. J. Petrol. 47:119–144.

Wang, Q.; Xu, J. F.; Zhao, Z. H.; Bao, Z. W.; Xu, W.; andXiong, X. L. 2004a. Cretaceous high-potassium intru-sive rocks in the Yueshan-Hongzhen area of eastChina: adakites in an extension al tectonic regimewithin a continent. Geochem. J. 38:417–434.

Wang, Q.; Zhao, Z. H.; Bao, Z. W.; Xu, J. F.; Liu, W.; Li,C. F.; Bai, Z. H.; and Xiong, X. L. 2004b. Geochemistryand petrogenesis of the Tongshankou and Yinzu ada-kitic intrusive rocks and the associated porphyrycopper-molybdenum mineralization in southeast Hu-bei, east China. Resour. Geol. 54:137–152.

Wang, Q.; Zhao, Z. H.; Xu, J. F.; Li, X. H.; Bao, Z. W.;Xiong, X. L.; and Liu, Y. M. 2003. Petrogenesis andmetallogenesis of the Yanshanian adakite-like rocks

Journal of Geology P A L E O - P A C I F I C S U B D U C T I O N I N E A S T E R N C H I N A 97

in the eastern Yangtze Block. Sci. China (D) 46:164–176.

White, W. M., and Duncan, R. A. 1996. Geochemistryand geochronology of the Society Islands: new evi-dence for deep mantle recycling. In Basu, A., and Hart,S. R., eds. Earth processes: reading the isotopic code.Am. Geophys. Union Monogr. 95:183–206.

Winther, T. K., and Newton, R. C. 1992. Experimentalmelting of anhydrous low-K tholeiite: evidence on theorigin of Archaean cratons. Bull. Geol. Soc. Den. 39:213–228.

Wolf, M. B., and Wyllie, P. J. 1991. Dehydration-meltingof solid amphibolite at 10 kbar: textural development,liquid interconnectivity and applications to the seg-regation of magmas. Mineral. Petrol. 44:151–179.

Woodhead, J. D.; Hergt, J. M.; Davidson, J. P.; and Eggins,S. M. 2001. Hafnium isotope evidence for conservativeelement mobility during subduction zone processes.Earth Planet. Sci. Lett. 192:331–346.

Wu, L. S., and Zou, X. Q. 1997. Re-Os isotopic age studyon the Chengmenshan Cu deposit in Jiangxi Province.Miner. Depos. 16:376–381 (in Chinese with Englishabstract).

Xie, G. Q.; Mao, J. W.; Li, L. R.; and Bierlein, F. 2008.Geochemistry and Nd-Sr isotopic studies of Late Me-sozoic granitoids in the southeastern Hubei province,Middle-Lower Yangtze River belt, eastern China: pet-rogenesis and tectonic setting. Lithos 104:216–230.

Xie, G. Q.; Mao, J. W.; Li, R. L.; Qu, W. J.; Pirajno, F.; andDu, A. D. 2007. Re-Os molybdenite and Ar-Ar phlog-opite dating of Cu-Fe-Au-Mo (W) deposits in south-eastern Hubei, China. Mineral. Petrol. 90:249–270.

Xie, G. Q.; Mao, J. W.; Li, X. W.; Duan, C.; and Yao, L.2011a. Late Mesozoic bimodal volcanic rocks in theJinniu basin, middle-lower Yangtze River belt (YRB),east China: age, petrogenesis and tectonic implica-tions. Lithos 127:144–164.

Xie, G. Q.; Mao, J. W.; and Zhao, H. J. 2011b. Zircon U-Pb geochronological and Hf isotopic constraints onpetrogenesis of Late Mesozoic intrusions in the south-east Hubei Province, Middle-Lower Yangtze River belt(MLYRB), east China. Lithos 125:693–710.

Xie, J. C.; Chen, S.; Rong, W.; Li, Q. Z.; Yang, X. Y.; andSun, W. D. 2012a. Geochronology, geochemistry andtectonic significance of Guniujiang A-type granite inAnhui Province. Acta Petrol. Sin. 28:4007–4020 (inChinese with English abstract).

Xie, J. C.; Yang, X. Y.; Sun, W. D.; and Du, J. G. 2012b.Early Cretaceous dioritic rocks in the Tongling region,eastern China: implications for the tectonic settings.Lithos 150:49–61.

Xie, J. C.; Yang, X. Y.; Sun, W. D.; Du, J. G.; Xu, W.; Wu,L. B.; Wang, K. Y.; and Du, X. W. 2009. Geochrono-logical and geochemical constraints on formation ofthe Tongling metal deposits, middle Yangtze metal-logenic belt, east-central China. Int. Geol. Rev. 51:388–421.

Xu, H. J.; Ma, C. Q.; and Ye, K. 2007. Early Cretaceousgranitoids and their implications for collapse of the

Dabie orogen, eastern China: SHRIMP zircon U-Pbdating and geochemistry. Chem. Geol. 240:238–259.

Xu, H. J.; Ma, C. Q.; Zhang, J. F.; and Ye, K. 2012a. EarlyCretaceous low-Mg adakitic granites from the Dabieorogen, eastern China: petrogenesis and implicationsfor destruction of the over-thickened lower continen-tal crust. Gondwana Res. 23:190–207.

———. 2012b. Generation of Early Cretaceous high-Mgadakitic host and enclaves by magma mixing, Dabieorogen, eastern China. Lithos 142–143:182–200.

Xu, J. F.; Shinjo, R.; Defant, M. J.; Wang, Q.; and Rapp,R. P. 2002. Origin of Mesozoic adakitic intrusive rocksin the Ningzhen area of east China: partial melting ofdelaminated lower continental crust? Geology 30:1111–1114.

Yan, J.; Chen J. F.; and Xu X. S. 2008. Geochemistry ofCretaceous mafic rocks from the lower Yangtze region,eastern China: characteristics and evolution of the lith-ospheric mantle. J. Asian Earth Sci. 33:177–193.

Yang, S. Y.; Jiang, S. Y.; Li, L.; Yan, S.; Sun, M. Z.; Bian,L. Z.; Xiong, Y. G.; and Cao, Z. Q. 2011a. Late Me-sozoic magmatism of the Jiurui mineralization districtin the middle-lower Yangtze River metallogenic belt,eastern China: precise U-Pb ages and geodynamic im-plications. Gondwana Res. 20:831–843.

Yang, W., and Zhang, H. F. 2012. Zircon geochronologyand Hf isotopic composition of Mesozoic magmaticrocks from Chizhou, the lower Yangtze region: con-straints on their relationship with Cu-Au minerali-zation. Lithos 150:37–48.

Zhang, C.; Ma, C. Q.; and Holtz, F. 2010. Origin of high-Mg adakitic magmatic enclaves from the Meichuanpluton, southern Dabie orogen (central China): im-plications for delamination of the lower continentalcrust and melt-mantle interaction. Lithos 119:467–484.

Zhang, H. F.; Gao, S.; Zhong, Z. Q.; Zhang, B. R.; Zhang,L.; and Hu, S. H. 2002. Geochemical and Sr-Nd-Pbisotopic compositions of Cretaceous granitoids: con-strains on tectonic framework and crustal structureof the Dabieshan ultrahigh-pressure metamorphicbelt, China. Chem. Geol. 186:281–299.

Zhang, Q.; Wang, Y.; and Qian, Q. 2001. The character-istics and tectonic-metallogenic significances of theadakites in Mesozoic period from eastern China. ActaPetrol. Sin. 17:236–244 (in Chinese with Englishabstract).

Zhou, T. F.; Song, M. Y.; Fan, Y.; Yuan, F.; Liu, J.; Wu,M. A.; Qian, C. C.; and Lu, S. M. 2007. Chronologyof the Bajiatan intrusions in the Luzong basin, Auhui,and its significance. Acta Petrol. Sin. 23:2379–2386(in Chinese with English abstract).

Zhou, X. M., and Li, W. X. 2000. Origin of Late Mesozoicigneous rocks in southeastern China: implications forlithosphere subduction and underplating of maficmagmas. Tectonophysics 326:269–287.

Zhu, J. 1998. Mesozoic granitoid types and metallogenyof the east China circum-Pacific continental margin.Resour. Geol. 48:265–272.