Journal of Asian Earth Sciences 135 (2017) 243–256

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Journal of Asian Earth Sciences

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Origin of allanite in gneiss and granite in the Dabie orogenic belt,Central East China

http://dx.doi.org/10.1016/j.jseaes.2016.12.0171367-9120/� 2016 Elsevier Ltd. All rights reserved.

⇑ Corresponding author.E-mail address: ylxiao@ustc.edu.cn (Y. Xiao).

Haihao Guo a,b, Yilin Xiao a,⇑, Lijuan Xu a,c, He Sun a, Jian Huang a, Zhenhui Hou a

aCAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, ChinabBayerisches Geoinstitut, University of Bayreuth, 95440 Bayreuth, Germanyc State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China

a r t i c l e i n f o

Article history:Received 13 May 2016Received in revised form 2 December 2016Accepted 10 December 2016Available online 16 December 2016

Keywords:AllaniteUHP metamorphismTrace elementsU-Th-Pb systematicsDabie-Sulu

a b s t r a c t

Allanite is a common accessory mineral phase, representing an important carrier of rare earth elements,Th, U, Sr and other trace elements in most continental rocks. As Th and U can be incorporated into theallanite lattice, the mineral is a good geochronological tool for constraining geological events.Moreover, the trace element features dEu, Th/U ratio and common lead content of allanite are indicatorsof the forming conditions. Allanite and coexisting epidote-group minerals are abundant in ultrahigh-pressure (UHP) metamorphic rocks from the Dabie-Sulu orogen in central East China. However, if theseminerals formed in the Neoproterozoic as magmatic phases, or in the Triassic as metamorphic phases is amatter of long-standing controversy. We report major and trace element analyses of whole rocks, allaniteand coexisting epidote-group minerals, together with U-Th-Pb isotopic compositions of allanite in UHPgneiss from the Dabie-Sulu orogen, and allanite in the adjacent Jingshan granite. The granite is emplacedalong the southeastern margin of the North China Craton and considered a product of partial melting ofthe subducted Dabie-Sulu gneiss. Trace elements (low Th/U and La/Sm, high dEu and high Sr) and highcommon lead concentrations indicate a metamorphic origin of allanite-epidote in the UHP gneiss. Onthe other hand, coarse-grained allanite from the Jingshan granite shows a corrosion core and a magmaticrim with common 208Pb up to 70% in the core and less than 30% in the rim. The allanite cores are of peri-tectic and the rims of magmatic origin with ages of �160 Ma, consistent with the granite crystallizationage. In combination with previous studies, we conclude that the allanite of the Jingshan granite has formfrom the subducted and remolten Dabie-Sulu gneiss. Allanite records Triassic UHP metamorphic ages aswell as Jurassic peritectic-magmatic ages as a part of the evolution of the Dabie-Sulu orogen.

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1. Introduction

Allanite ([Ca, REE]2[Fe, Al]3Si3O12[OH]) is a common accessorymineral from the epidote-group which widely occurs in metamor-phic and magmatic rocks (e.g., Gieré and Sorensen, 2004). Itschemical exchange with clinozoisite (REE3+ + Fe2+ M Ca2+ + Al3+)and epidote (REE3++ Fe2+ M Ca2+ + Fe3+) make it suitable as a sinkfor rare earth elements (REE) (Dollase, 1971). Meanwhile, allaniteis also a potential carrier of Sr2+, Pb2+, Th4+, U4+, Mn3+, Mn2+, Cr3+,Ti4+, Zr4+, Ba2+, etc. by chemical isomorphism (Deer et al., 1986).The high degree of chemical flexibility of allanite makes it a goodrecorder of trace element signatures of specific magmatic, meta-morphic and ore-forming processes (e.g., Janots et al., 2008; Palet al., 2011; Vlach and Gualda, 2007). Additionally, high concentra-

tions of Th and U in allanite make it a good tool for both U-Pb andTh-Pb geochronology. However, Th-Pb geochronology is preferabledue to the high Th/U ratios (up to 1000) and excess 230Th(t1/2 = 75400y) which may decay into 206Pb (Darling et al., 2012).The latter has a negative effect on the U-Pb system, especially forjuvenile allanite crystals. Previous allanite geochronology wasbased on high-precision isotope dilution (ID)-TIMS analysis(Barth et al., 1994; Von Blanckenburg, 1992), which requires mul-tiple allanite grains. However, this method may be inaccurate dueto (1) the difficulty of requires allanite separates from intergrowthswith epidote and clinozoisite (Liu et al., 1999; Romer and Xiao,2005), and (2) the presence of mineral inclusions such as quartz,zircon, apatite, monazite in the allanite grains (Romer and Xiao,2005; Wang et al., 2006). Therefore in-situ analytical methodolo-gies, such as dating of allanite by SHRIMP (Catlos et al., 2000;Gregory et al., 2007) and LA-ICPMS (Darling et al., 2012; Gregoryet al., 2007; Smye et al., 2014) have been developed in order toavoid these problems.

244 H. Guo et al. / Journal of Asian Earth Sciences 135 (2017) 243–256

Allanite is stable at magmatic, metamorphic and hydrothermalconditions for a wide range of pressures (P) and temperatures (T)(e.g., Chen and Zhou, 2014; Guo et al., 2014; Hermann, 2002).The stability of allanite at (U)HP metamorphic conditions has beendemonstrated experimentally (Hermann, 2002) and empirically(Spear, 2010). The combination of isotopic ages, chemical composi-tions and stability conditions make allanite an important tool fore.g., the age determination of incipient melting in high-grademetamorphic rocks (Gregory et al., 2012), exploring yo-yo subduc-tion by allanite and zircon geochronology (Rubatto et al., 2011) andbuilding P-T-t paths of orogens (Janots et al., 2009). Overall, under-standing the origin of allanite/epidote is the key to a number ofgeological applications.

Allanite and epidote-group minerals are abundant in the Dabie-Sulu orogen and have been previously investigated by Liu et al.(1999), Nagasaki and Enami (1998) and Yang and Enami (2003).Sr isotopes in allanite-epidote in eclogite drill cores studied inthe frame of the Chinese Continent Scientific Drilling Program(CCSD) show a large variation, which was assumed the result ofmetamorphic reactions during subduction (Romer and Xiao,2005). Furthermore, age dating of allanite and epidote from theCCSD by electron microprobe analysis revealed Mid-Neoproterozoic as well as Triassic ages (Wang et al., 2006). There-fore the origin of the allanite from this area is still a matter ofdiscussion.

In order to constrain the origin of allanites in the Dabie-Suluorogen and their relationship with the different rock types, allan-ites and epidotes from gneissic rocks in the Dabie-Sulu orogenand from the granite of Jingshan in the south-eastern margin ofthe North China Craton were investigated in the present study.We also used X-ray fluorescence, electron microprobe and LA-ICPMS to analyze major and trace elements of both bulk rock andallanite-epidote minerals and their U-Th-Pb isotope signatures.

Fig. 1. A sketch map of general geology in the Dabie–Sulu orogenic belt, central-east China (after Huang et al., 2012), with sample localities.

2. Geologial settings and samples

The Dabie-Sulu orogen in central East China formed during theTriassic by the northward subduction of the South China Blockbeneath the North China Block (e.g., Li et al., 1993, 2000; Zhenget al., 2003, 2009). Occurrences of coesite and diamond inclusionsin eclogite, gneiss, and marble (e.g., Okay, 1993; Schertl and Okay,1994; Wang et al., 1989; Xu et al., 1992, 2003) are indicative ofUHP metamorphism in the orogenic belt. The orogen (Fig. 1) con-sists of a series of fault-bounded metamorphic units and has beendivided into five metamorphic zones from north to south (e.g.,Zheng et al., 2005). The Sulu orogen is situated in the eastern partof the Dabie orogen with an offset of �500 km to the northeastalong the Tan-Lu fault relative to the Dabie orogen (Fig. 1). TheSulu orogen is bounded by the Jiashan-Xiangshui fault in the southand the Wulian-Yantai fault in the north, and is segmented into anumber of slices by several faults subparallel to the Tan-Lu fault(Xu et al., 2006).

Gneiss is widely spread over the Dabie-Sulu orogen. The occur-rences of coesite inclusions in zircon (e.g., Liu et al., 2001) demon-strate that the gneiss, together with other metamorphic rocks likeeclogite, granulite and amphibolite, underwent UHP metamor-phism. Zircon U-Pb dating revealed Mid-Neoproterozoic ages forthe gneiss protolith and Triassic ages for the UHP metamorphicevent (e.g., Liu et al., 2001, 2004; Xia et al., 2009, 2010).

Bengbu, located �150 km north of the Dabie orogen, is anuplifted region on the south-eastern margin of the North ChinaCraton, with the Tan-Lu fault zone to the east and the Hefei basinto the south (Fig. 1). Voluminous Mesozoic granitoids intruded intothe Wuhe Complex basement in the Late Jurassic and in the Earlyto Mid-Early Cretaceous. The Jingshan intrusion is located in the

western part of the Bengbu region and consists predominantly ofgarnet-bearing leucogranite (Guo and Li, 2009; Xu et al., 2013).Previous studies identified Neoproterozoic igneous zircons and Tri-assic metamorphic zircons in the Jurassic leucogranites (Xu et al.,2005; Yang et al., 2010), which are similar to those observed inthe Dabie-Sulu UHP metamorphic rocks, suggesting that the crus-tal material of the South China Block must have been subducted orinjected into the Bengbu area (Xu et al., 2005; Yang et al., 2010; Liet al., 2014). A complex mineral assemblage with 3 types of garnetwas reported for the Jurassic Jingshan leucogranite (Yang et al.,2010; Liu et al., 2012; Xu et al., 2013). The garnets are peritecticor magmatic in origin, based on their chemistry, oxygen isotopeand U-Pb dating of zircon inclusions (Xu et al., 2013).

The origin of allanite and epidote in the Dabie-Sulu orogen is amatter of discussion. Some authors suggest that allanite is igneousand the surrounding epidote metamorphic in origin (e.g., Liu et al.,1999), while others suggest a metamorphic origin of both minerals(e.g., Romer and Xiao, 2005). In spite of evidence that the Bengbuleucogranite is genetically linked to the Dabie-Sulu gneiss, the ori-gin of allanite in the leucogranite (Xu et al., 2013) remains unclear.The allanite may have been inherited from the protolith gneiss (Xuet al., 2005; Yang et al., 2010) or formed during Late Jurassic mag-matism (Xu et al., 2013).

For the purpose of investigating the origin of allanite in theDabie-Sulu orogen, and the relationship between the Jingshanand Dabie-Sulu orogen, fourteen representative samples were col-lected for the study. The objects of this study include 4 gneiss sam-ples from Shima (SM) in South Dabie, 3 gneiss samples fromShuanghe (SH) in Central Dabie, 4 gneiss samples from Fangshan

Table 1Mineral assemblage and modal contents (vol.%) of studied samples.

Sample location Sample no. Petrology Mineral assemblage and modal contents (vol.%)

Shuanghe 10-SH-13 Gneiss Qtz 25, Kf 40, Plg 30, Bt <5, Aln&Ep tiny10-SH-14 Gneiss Qtz 35, Kf 35, Plg 25, Bt <5, Aln&Ep tiny10-SH-15 Gneiss Qtz 30, Kf 40, Plg 25, Bt <5, Aln&Ep tiny

Shima 10-SM-2 Gneiss Qtz 15, Kf 50, Plg 30, Bt + mica <5, Aln&Ep tiny10-SM-3 Gneiss Qtz 25, Kf 40, Plg 30, Bt + mica <5, Aln&Ep tiny10-SM-6 Gneiss Qtz 20, Kf 45, Plg 30, Bt <5, Aln&Ep tiny10-SM-19C Gneiss Qtz 15, Kf 20, Plg 15, Grt25, Bt 25, Aln&Ep tiny

Fangshan FS-03-1 Gneiss Qtz 30, Kf 30, Plg 35, Bt <5, Aln&Ep tinyFS-03-2 Gneiss Qtz 40, Kf 20, Plg 35, Bt <5, Aln&Ep tiny12SL-FS8 Gneiss Qtz 30, Kf 30, Plg 35, Bt, Amp <5, Aln&Ep tiny12SL-FS14 Gneiss Qtz 35, Kf 30, Plg 30, Bt, Amp <5, Aln&Ep tiny

Jingshan 09JS-4 Granite Qtz 25, Kf 40, Plg 30, Bt + mica <5, Aln tiny09JS-6 Granite Qtz 15, Kf 10, Plg 10, Bt 50, Grt 5, Aln&Ep tiny09JS-r Granite Qtz 15, Kf 10, Plg 10, Bt 50, Grt 5, Aln&Ep tiny

Abbreviations: Qtz-quartz, Kf-K-feldspar, Plg-plagioclase, Bt-biotite, Amp-amphibole, Aln-allanite, Ep-epidote.

Fig. 2. Polarized microscopy photographs and back-scattered electron (BSE) images of allanite and epidote in this study, (a and b)-Shima, Dabie, (c–f)-Shuanghe, Dabie, (g–j)-Fangshan, Sulu, (k and l)-Jingshan. (a) Allanite in the core and epidote in the rim, (b) Epidote surrounds allanite and fluid inclusion (FI) in the allanite, (c) (d) Allanite in thecore and epidote in the rim, quartz as inclusions in allanite, (e and f) A small quantity of epidote as rims of allanite, (g and h) Allanite-epidote grain in biotite gneiss, (i and j)Allanite as an inclusion in an epidote cryst and the epidote shows a prismatic shape, (k and l) Big allanite in granite and the core is corroded with magmatic zoning in the rim.Abbreviations: Qtz, quartz; Kf, K-feldspar; Plg, plagioclase; Bt, biotite; Amp, amphibole; Aln, allanite; Ep-epidote.

H. Guo et al. / Journal of Asian Earth Sciences 135 (2017) 243–256 245

246 H. Guo et al. / Journal of Asian Earth Sciences 135 (2017) 243–256

(FS) in the Sulu orogen, and 3 granite samples from Jingshan (JS)along the south-eastern margin of the North China Craton(Fig. 1). Mineral assemblages and other petrological features ofthe samples are listed in Table 1 and shown in Fig. 2. In the samplesfrom Shima, quartz and feldspar (K-feldspar and plagioclase) arepresent in >90% modal abundance. Allanite is usually rimmed byepidote with grain size of 200–300 lm (Fig. 2a). Mineral inclusionsof mainly quartz and feldspar and fluid inclusions can be found inthe allanite or epidote crystals (Fig. 2b). In the samples fromShuanghe, allanite is rimmed by a thin layer of epidote with graindiameters (d) ranging from a few to hundred micrometers. Inclu-sions in allanite mostly consist of quartz and iron oxides(Fig. 2c–f). In the sample from Fangshan, allanite is surroundedby large epidote grains (d � 100 lm) (Fig. 2g–j). In the sample fromJingshan, two types of allanite have been observed: coarse-grainedallanite (d > 1 mm) showing chemical zoning (Fig. 2k and l), andfine-grained allanite (d < 100 lm) with a very thin epidote rims.

3. Analytical methods

3.1. Whole rock analysis

Fresh rock samples were crushed in steel jaw crushers and pow-dered to grain sizes <200 mesh in an agate mill. The fine-grainedrock powders were subsequently synthetized into glass withlithium tetraborate as a flux. Major elements were determinedusing X-ray fluorescence (XRF-1800). Trace elements were ana-lyzed using a Perkin-Elmer ELAN DCR-II inductively coupledplasma source mass spectrometer (ICP-MS) at the CAS Key Labora-tory of Crust-Mantle Materials and Environments, University ofScience and Technology of China, Hefei (USTC). The procedureswere described in Hou and Wang (2007).

3.2. Mineral chemistry

Major element concentrations and backscattered electron (BSE)images were determined by electron microprobe (EMP) using aJXA-8900RL Jeol Superprobe equipped with wavelength-dispersive spectrometers (WDS) and an energy dispersive spec-trometer (EDS) at the Geowissenschaftliches Zentrum Göttingen(GZG). The machine was operated at 15 kV accelerating voltageusing12 nA beam current with a 5 lm beam diameter. BSE imagesof minerals were taken by the scanning electron microscope (SEM)using a XL-30 ESEM in Environment SEM Lab at USTC. The voltageand beam current were 20 kV accelerating and 18 nA, using a 16–17 mm working distance (WD). Detailed analytical procedureswere presented in Xiao et al. (2011).

In situ trace element concentrations of minerals were deter-mined using a 193 nm Excimer Laser (Coherent, USA) coupled toan Elan DRC-II (Perkin Elmer, Canada) quadrupole ICPMS at the

Table 2LA-ICPMS instrument parameters and experimental conditions.

Laser system ICP-MS

Model GeoLas Pro Model

Type ArF Excime TypeWavelength 193 nm Forward power (WEnergy density 10 J cm�2 Plasma gas flow (ARepetition rate 5–10 Hz Auxiliary gas flowHe carrier gas speed 0.3 L min�1 Make-up (Ar)Laser warm up �30 s Scanning modeAblation time �40 s Geochronology isotAblation style Single spotWash out time >120 s Trace elements isoLaser spot diameter 30–60 lm

University of Science and Technology of China (USTC). Instrumen-tal parameters and working conditions of both the laser and ICPMSsystems are listed in Table 2. NIST SRM 610 glass was used asexternal standard, referring to the preferred values listed on theGeoReM database (http://georem.mpch-mainz.gwdg.de/). SiO2

concentrations determined by EMPA were used as internalstandardization.

3.3. Allanite U-Th-Pb isotope by LA-ICPMS

Allanite U-Th-Pb isotope measurements were done by LA-ICPMS at the USTC. The instrumental parameters and working con-ditions of both laser and ICPMS systems are listed in Table 2. Zircon91500 was used as an external standard, which was measured oncewith every 4 unknown sample analysis spots. The allanite U-Th-Pbdating without a matrix-matched standard (e.g., Zircon 91500,NIST 610 glass) have been applied for accurate geochronology(e.g., Darling et al., 2012; Guo et al., 2014; McFarlane, 2016). Theprocedures and age calculations in this study were described inGuo et al. (2014). 232Th/206Pbc and 208Pb/206Pbc isochron (206Pbc

is common 206Pb amount) (Gregory et al., 2007), as well as207Pb/235U and 206Pb/238U Tera-Wasserburg regression (Jacksonet al., 2004; Tera and Wasserburg, 1972) were applied for age cal-culation. In this study 204Pb (e.g., Storey et al., 2006, 2007) and207Pb corrections (e.g., Gregory et al., 2007; Li et al., 2012) wereapplied to correct for common 208Pb. Model terrestrial Pb isotopeevolution curves (Stacey and Kramers, 1975) were used for thecommon-Pb correction. The common 204Pb correction is moreproblematic due to interference of 204Hg in the carrier gas. The204Pb concentration was corrected by subtracting the 204Hg contri-bution from the total 204Pb signal based on measured 202Hg iso-topes and the 204Hg/202Hg natural atomic abundance of 0.22983(Rosman and Taylor, 1999).

The common 208Pb concentration (f208) is calculated as follows:

f 208 ¼208Pbc

208PbTotal¼ ð208Pb=204PbÞc

ð208Pb=204PbÞmð1Þ

The common 206Pb concentration (f206) is acquired (Williams,1998):

f 206 ¼206Pbc

206PbTotal¼ ð207Pb=206PbÞm � ð207Pb=206PbÞ�

ð207Pb=206PbÞc � ð207Pb=206PbÞ� ð2Þ

where (207Pb/206Pb)m is the measured ratio, (207Pb/206Pb)⁄ is theexpected radiogenic ratio for the inferred age and (207Pb/206Pb)c isthe common Pb composition.

The uncertainty of f 206 is f 206err

¼ f 206 �ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffið207Pb=206PbÞ2merr

� ð1þ f 2206Þqð207Pb=206PbÞm � ð207Pb=206PbÞ� ð3Þ

PerkinElmer/SCIEX, Elan DRCII

Quadruple) 1350 Wr) 15 L min�1

(Ar) 1.21 L min�1

0.7 L min�1

Peak hoppingope measured 204Pb,206Pb,207Pb,208Pb, 235U,238U,232Th,29Si,202Hg

tope measured 7Li � 238U listed in Table 5

H. Guo et al. / Journal of Asian Earth Sciences 135 (2017) 243–256 247

232Th206Pbc

and 208Pb206Pbc

(206Pbc is the common 206Pb amount) are asfollows:

232Th206Pbc

¼ ð232Th=206PbÞmf 206

ð4Þ

208Pb206Pbc

¼ ð208Pb=206PbÞmf 206

ð5Þ

The common 208Pb amount (f208) can be calculated via f206:

f 208 ¼208Pbc

208PbTotal¼ f 206 �

ð208Pb=206PbÞcð208Pb=206PbÞm

ð6Þ

The 232Th206Pbc

and 208Pb206Pbc

isochron equation is achieved by a combina-tion of Eqs. (4) and (5):

208Pb206Pbc

¼208Pbc206Pbc

þ232Th206Pbc

ðek232t � 1Þ ð7Þ

Table 3Bulk rock major and trace element concentrations of studied samples.

Sample 10-SM-2 10-SM-19C 10-SM-6 10-SM-3 10-SH-13 10-SH-14 10-

Major element (%)SiO2

TiO2

Al2O3

Fe2O3

MnOMgOCaONa2OK2OP2O5

Trace element (ppm)Li 1.9 1.1 14.0 1.0 4.1 1.3 3.7Be 1.9 1.6 1.0 4.1 2.2 2.6 3.4B 3.5 3.7 4.0 3.9 3.0 3.5 3.6Sc 3.3 2.9 76 5.5 7.2 6.6 9.6Ti 758 686 21752 780 1706 1046 216V 6.1 10 189 4.4 13 3.6 6.7Cr 3.4 2.3 153 7.5 3.4 3.1 2.8Co 0.7 0.6 36 0.6 1.8 0.3 1.4Ni 1.8 0.9 12 1.8 2.4 3.3 2.3Cu 5.1 2.6 175 4.8 10 5.8 8.8Zn 36 69 97 59 71 84 95Ga 20 23 15 27 22 25 24Rb 46 51 38 4 36 42 42Sr 43 63 32 33 51 177 114Y 54 67 144 90 60 56 78Zr 256 628 34 755 330 585 391Nb 8 18 45 18 12 14 15Cs 0.3 0.1 0.5 0.1 0.4 0.2 0.5Ba 2240 200 79 24 1844 1972 107La 31 38 0.9 61 41 52 58Ce 48 77 1.4 127 61 101 114Pr 8 10 0.3 16 11 13 14Nd 32 35 1.5 56 39 44 54Sm 6.9 8.9 1.9 13 8.6 9.0 12Eu 0.9 1.1 1.1 1.8 1.4 0.9 2.0Gd 6.7 8.6 5.8 13 7.8 8.1 11Tb 1.2 1.5 1.9 2.1 1.3 1.2 1.8Dy 7.4 9.6 16.0 12.8 8.2 7.4 11Ho 1.7 2.1 4.1 2.8 1.8 1.6 2.4Er 5.6 6.3 13.6 8.6 5.8 5.1 7.3TmYb 5.5 6.1 13 7.7 5.8 5.2 7.3Lu 1 1.06 2.3 1.3 1.1 0.98 1.4Hf 7.4 13.7 0.8 15 7.0 13 8.7Ta 0.7 1.4 1.7 1.4 0.61 0.73 0.67Pb 16 20 0.7 20 37 14 10Th 6.3 10 0.1 14 5.3 8.4 7.6U 1.5 2.6 0.1 2.6 1.2 1.7 1.5

for which the decay coefficient is k232 = 4.9475 � 10�7/Ma, the slope

is given as ðek232t � 1Þ and the intercept is the208Pbc206Pbc

ratio.Radiogenic 208Pb over 232Th is calculated using Eqs. (1) and (6):

208Pb�

232Th¼ ð1� f 208Þ �

208Pb232Th

� �m¼ ek232t � 1 ð8Þ

Single-spot ages of allanite were calculated using equation (8)and isotope data were plotted using the ISOPLOT program(Ludwig, 2003) to represent the ages.

4. Results

4.1. Whole-rock major and trace element geochemistry

All the studied samples have high SiO2 concentrations with fea-tures of metaluminous to peraluminous (Table 3; Fig. 3). The totalalkaline contents (ALK = Na2O + K2O, in wt%) vary from 7.06 to 9.23

SH-15 FS-03-2 FS-03-1 12SL-FS14 12SL-FS8 09-JS-4 09-JS-2 09-JS-r

73.9 76.3 72.8 74.7 70.40.27 0.15 0.13 0.05 0.2212.3 12.2 14.5 14.3 14.52.4 1.3 1.1 0.4 2.60.07 0.03 0.06 0.01 0.210.28 0.1 0.23 0.06 0.461.1 0.7 1.5 1.2 1.64.8 3.9 4.7 5.2 4.02.9 3.5 3.6 3.6 4.10.07 0.03 0.01 0.06

3.8 3.0 2.8 9.0 0.9 6.4 462.6 3.7 1.9 5.0 1.3 0.9 2.110 111.6 1.7 1.3 3.0 3.4 2.0 4.9

5 852 1028 191 549 12403.8 2.8 3.0 3.5 33 35 9310.2 3.5 5.4 3.70.7 0.7 0.6 1.0 0.3 0.7 1.55.2 1.1 24 13 1.0 1.6 2.438 17 6.5 3.7 2.2 1.7 3.087 118 7 37 10528 29 21 21 42 70 5632 39 124 66 12 10 2211 31 15 47169 113 45 76 111 141 188549 557 424 556 238 526 51412 15 14 14 11 10 160.2 0.2 0.5 0.6 0.7 1.4 2.2

7 186 359 2040 1197 454 1591 130023 75 42 66 2.1 8 744 144 79 120 3.8 13 116 17 10 16 0.5 1.4 1.322 60 37 61 2.1 5.5 5.06.1 12 8.4 12 0.8 1.1 1.20.9 1.5 1.0 2.1 0.2 0.3 0.37.6 12 7.5 11 1.1 1.2 1.51.8 2.0 1.3 1.9 0.2 0.2 0.315 14 8.4 12 1.4 1.4 1.94.3 3.2 1.7 2.6 0.3 0.3 0.416 11 5.0 7.9 0.8 1.0 1.5

0.8 1.3 0.13 0.16 0.2417.5 11.1 5.2 8.7 1.1 1.5 2.03.4 2.1 0.77 1.4 0.17 0.21 0.3113 13 11 12 2.0 1.8 1.83.1 0.83 0.99 0.7 1.3 0.46 1.68.1 8.9 2.1 30 48 46 494.4 13 10 11 2.2 2.6 3.01.5 2.0 1.6 2.6 2.4 2.6 5.8

Fig. 3. Diagrams of studied samples, (a) Total alkalis vs. SiO2 diagram, (b) A/CNK-A/NK diagram, (c) and (d) Chondrite and primitive mantle normalized trace elementsdiagrams. MD: monzodiorite, MZ: monzonite, GD: gabbrodiorite. Data of SM and SH come from Hu et al. (2006), partial data of FS come from Hu et al. (2010). Normalizedvalues are from Sun and McDonough (1989).

248 H. Guo et al. / Journal of Asian Earth Sciences 135 (2017) 243–256

for Shima and Shuanghe (Dabie), from 7.36 to 10.10 for Fangshan(Sulu), and from 8.10 to 8.71 for Jingshan. All samples except oneshow LREE-rich patterns with negative Eu anomalies, while sam-ples from Dabie and Sulu (Shima, Shuanghe and Fangshan) showmuch higher total REE concentrations than the samples from Jing-shan. Almost all rocks are characterized by enrichment of large ionlithophile elements (LILE, e.g., Rb, Cs, Th, U and Pb) and depletion ofhigh field strength elements (HFSE, e.g., Nb, Ta and Ti) (seeTable 3).

Fig. 4. (a) Total Al vs. REE atoms per formula unit (a.p.f.u) diagram for allanite andepidote, (b) REE + Fe2+ + Mg + Mn vs. Ca + Al + Fe3+ (a.p.f.u) diagram.

4.2. Major and trace element geochemistry of allanite and epidote

Electron microprobe data show that the chemical compositionsof the epidote-group minerals vary over a large range (Fig. 4;Table 4). For samples from the Dabie-Sulu orogen (Shima,Shuanghe and Fangshan), the epidote-group minerals contain29.4–37.5 wt.% SiO2, 12.2–23.0 wt.% CaO, and 0.1–20.5 wt.% REEoxides. The corresponding maximum contents of SrO and ThOare 2.90 wt.% and 1.95 wt.%, respectively. In the epidote-groupminerals from Jingshan, SiO2 ranges from 30.5 to 37.4 wt.%, with11.2 to 24.3 wt.% CaO, up to 14.4 wt.% REE oxides, a maximum of0.64 wt.% SrO and 1.23 wt.% ThO2. As shown in Fig. 4a, we can clas-sify the mineral group into allanite and epidote, according to thenumbers of REE + Th atoms per formula unit as suggested byGieré and Sorensen (2004). The fitting of the line (Fig. 4b) showsthe possible isomorphism in the epidote-group minerals: REE+ Fe2+ = Ca + Fe3+; REE + Fe2+ = Ca + Al3+; REE + Mg (Mn) = Ca+ Fe3+(Al3+) (Dollase, 1971).

All allanites are highly enriched in light rare earth elements(LREE) (Fig. 5). The (La/Yb)N values range from 140 to 270 inallanite, and from 1.5 to �65 in epidote. Note that (La/Yb)N isnormalized according to the chondrite data from Sun andMcDonough (1989). Three types of REE patterns were

Table 4Representative allanite and epidote compositions by electron microprobe of studied samples. – is under the detection.

Sample SM SH FS JS

Mineral Aln Aln Ep Aln Aln Ep Aln Aln Ep Aln Aln Ep

K2O 0.01 0.01 – – – – 0.01 – – 0.01 0.01 0.01Na2O 0.14 0.14 – 0.1 0.19 – 0.2 0.24 0.02 0.03 0.04 –CaO 13.3 13.4 22.5 13.8 13.8 22.3 13.4 13.5 22.5 14.4 14.6 22.6La2O3 4.1 3.9 0.01 3.92 3.87 0.05 4.5 4.6 0.01 4.0 3.5 0.04FeO 8.2 7.7 12 8.4 8.6 13.6 8.7 8.6 14.5 13.7 13.9 12.5Y2O3 0.08 0.19 0.7 0.33 0.37 0.04 0.15 0.13 0.22 0.19 0.19 0SiO2 34.1 34.3 36.9 34.6 34.4 37.3 33.8 33.8 37.3 34.5 34.2 37.5TiO2 0.11 0.08 0.07 0.12 0.17 0.02 0.07 0.11 0.09 0.44 0.48 0.23CeO2 9.0 8.4 – 8.3 8.0 0.0 9.3 9.3 – 7.2 7.0 –Sm2O3 0.3 0.37 0.02 0.31 0.42 – 0.27 0.26 – 0.17 0.19 –SrO 1.6 1.67 0.15 0.61 0.63 0.55 0.49 0.49 0.02 0.04 0.03 0.36Al2O3 22.7 23.1 23.4 22.5 22.6 21.9 22.5 22.4 21.5 18.2 18.0 22.9ThO2 0.51 0.36 – 0.43 0.44 0.02 0.56 0.54 – 0.53 0.57 –Pr2O3 0.87 0.99 0.04 0.91 0.93 0.03 0.9 1.04 – 0.58 0.74 –Gd2O3 0.16 0.19 0.06 0.25 0.18 – 0.21 0.17 0.06 0.13 0.1 –MgO 0.03 0.03 – 0.04 0.04 – 0.02 0.05 0.02 0.52 0.53 0.01Nd2O3 3.3 3.3 0.09 3.3 3.2 0.03 3.3 3.2 – 0.08 0.07 –Dy2O3 0.2 0.17 0.18 0.69 0.65 0.25 0.13 0.11 0.19 2.24 2.2 –Total 98.8 98.2 96.1 98.5 98.3 96.1 98.5 98.6 96.4 98.1 97.5 96.7

Atoms per formula unit (a.p.f.u) calculated by cations equal to 8K 0.001 0.001 – – – – 0.001 – – 0.001 0.001 0.00Na 0.02 0.02 – 0.02 0.03 – 0.04 0.04 0.003 0.005 0.007 0.00Ca 1.27 1.27 1.94 1.31 1.31 1.94 1.28 1.29 1.95 1.37 1.39 1.94La 0.13 0.13 0.00 0.13 0.13 0.001 0.15 0.15 0.0003 0.13 0.11 0.00Fe 0.61 0.57 0.81 0.62 0.63 0.92 0.65 0.64 0.98 1.02 1.03 0.83Y 0.004 0.01 0.03 0.02 0.02 0.002 0.007 0.006 0.01 0.009 0.009 0.00Si 3.04 3.05 2.97 3.07 3.05 3.02 3.02 3.01 3.01 3.05 3.04 3.00Ti 0.01 0.01 0.004 0.01 0.01 0.001 0.005 0.007 0.01 0.03 0.03 0.01Ce 0.28 0.26 – 0.26 0.25 0.001 0.29 0.29 – 0.22 0.22 0.00Sm 0.01 0.01 0.0005 0.01 0.01 – 0.01 0.01 – 0.01 0.01 0.00Sr 0.08 0.09 0.01 0.03 0.03 0.03 0.03 0.03 0.001 0.002 0.002 0.02Al 2.38 2.42 2.22 2.35 2.36 2.09 2.37 2.36 2.04 1.90 1.88 2.16Th 0.01 0.01 – 0.01 0.01 0.0003 0.01 0.01 – 0.01 0.01 0.00Pr 0.03 0.03 0.001 0.03 0.03 0.001 0.03 0.03 – 0.02 0.02 0.00Gd 0.005 0.01 0.002 0.01 0.01 – 0.01 0.01 0.002 0.00 0.00 0.00Mg 0.005 0.003 – 0.005 0.005 – 0.003 0.007 0.003 0.07 0.07 0.00Nd 0.10 0.10 0.003 0.10 0.10 0.001 0.10 0.10 – 0.002 0.002 0.00Dy 0.01 0.00 0.005 0.02 0.02 0.01 0.004 0.003 0.005 0.07 0.07 0.00total 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 7.91 7.91 7.97

H. Guo et al. / Journal of Asian Earth Sciences 135 (2017) 243–256 249

recognized in in the epidote-group minerals SM and SH consist-ing of an allanite core, epidote around allanite, and epidote inmatrix (Fig. 5a and b). Allanite cores are charactered by theenrichment of LREE with a slight negative Eu anomaly, whileepidote rims around allanite have lower REE concentration thanthe allanite with an enrichment of LREE and a negative Euanomaly. Epidote in the matrix is usually coarse-grained andshows low REE concentrations and the absence of negative Euanomalies (Fig. 5a and b).

4.3. Allanite U-Th-Pb geochronology

As best example the U-Th-Pb isotopic compositions of allanitefrom Shima (Dabie) were investigated in detail (Table 6). Highcommon lead contents in the mineral allows application of the204Pb correction method (Williams, 1998). The common208Pb ranges from 0.74 to 0.93 (Table 6 and Fig. 6). The232Th/206Pbc-208Pb/206Pbc isochron ages concentrate around210 ± 75 Ma (Fig. 7a). The U-Pb age corresponding to the lowerintersection point in the Tera-Wasserburg diagram is180 ± 71 Ma (Fig. 7b). In this case, the common Pb correction afterStacey and Kramers (1975) is not well constrained (e.g. Cenki-Toket al., 2014; Janots and Rubatto, 2014) and therefore the Th-Pbaverage ages are not shown.

The U-Th-Pb isotope data of allanite from Jingshan (see thegrain in Fig. 2k and l) are listed in Table 7. The 232Th/206Pbc-208Pb/206Pbc isochron age is 159 ± 10 Ma (Fig. 8a), whereas theU-Pb age corresponding to the lower intersection point in theTera-Wasserburg diagram is 159 ± 18 Ma (Fig. 8b). The 208Pbcontent in the corrosion core is relatively high (about 50–70%),but much lower in the magmatic rim (<30%, Fig. 6). The average208Pb-232Th age found for the rim after 207Pb correction is154 ± 3 Ma (Fig. 8c), with a majority age of around 150–160 Ma(Fig. 8d).

5. Discussion

5.1. The origin of allanite from the gneiss of the Dabie-Sulu orogenicbelt

Zirconology studies in gneiss of the Dabie-Sulu orogen havedistinguished 3 types of zircon formed during differentgeological stages: (1) magmatic zircon in the Neoproterozoic(c.a. 770–780 Ma), (2) metamorphic zircon in the Triassic(c.a. 220–230 Ma) and (3) anatexis zircon with an age of�214 Ma during retrograde metamorphism (Chen et al., 2013;Xia et al., 2009, 2010; Zheng, 2008). The observation that allaniteis always characterized by a rim of epidote (e.g., Liu et al., 1999;Romer and Xiao, 2005; Wang et al., 2006) implies that epidote

Fig. 5. REE pattern of allanite and epidote for studied samples.

250 H. Guo et al. / Journal of Asian Earth Sciences 135 (2017) 243–256

must have formed after the allanite. There are two possible scenar-ios: (1) allanite formed in the Neoproterozoic and epidote duringTriassic metamorphism, or (2) both allanite and epidote formedduring Triassic metamorphism.

Common lead concentrations and trace elements of allaniteare indicators of its origin (Gregory et al., 2009, 2012). Com-mon 208Pb in the allanites from Shima is up to 90% (Fig. 6),indicating metamorphic origin (Gregory et al., 2009; Janots

Fig. 6. Commom208Pb (f208) in allanite from gneiss in Dabie and granite in Jingshan.Magmatic source: CAP allanite (Barth et al., 1994); Tara allanite stone (Gregoryet al., 2007); AVC allanite (Barth et al., 1994); Siss allanite (Von Blanckenburg,1992); Bona allanite (Von Blanckenburg, 1992); BC allanite (Gregory et al., 2007);GOL06 allanite the, BEM1 allanite, VAM1 allanite (Gregory et al., 2012); Xinfengallanite (Guo et al., 2014). Migmatitic source: PE13 allanite (Gregory et al., 2009);VAM2 allanite, GOL06 allanite, BEL1 allanite, VAL1 allanite, VAL2 allanite (Gregoryet al., 2012). Metamorphism (Subsolidus) source: PE13 allanite (Gregory et al.,2009); MF161 allanite, APi0413 allanite (Janots et al., 2009); WS2 allanite(Gabudianu Radulescu et al., 2009); the La-VdT-2 allanite (Rubatto et al., 2008).

and Rubatto, 2014). At eclogite-faces conditions, feldsparbreaks down and releases lead (Gregory et al., 2009), whichis incorporated by the growing allanite. In the diagram plotsof La/Sm vs. Th/U and La/Sm vs. dEu (dEu = Eu/Eu⁄ and Eu⁄ = -ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiSm � Gd

p), all allanites and epidotes from Dabie-Sulu orogen

indicate metamorphic origin, whereas allanites from Jingshanare both magmatic and metamorphic in character (Fig. 9a). Ithas been shown that fluid has less differentiation ability forLa (LREE) and Sm (MREE) than magmatic melt, whereas themobility of U in the fluid is higher than that in the melt(Gregory et al., 2012). Janots and Rubatto (2014) found thatsubsolidus (greenschist facies) allanite shows high Th/U values(>100) in samples with mineral assemblages indicative of highoxygen fugacity (U[VI] present). These values restrict the possi-bility of distinguishing magmatic vs. metmorphic origin. How-ever, in our study we found that the metamorphic epidote-group minerals are characterized by low La/Sm and low Th/U. Furthermore, plagioclase is relatively enriched in Sr andEu and these elements are released during decompositionunder eclogite-facies conditions (Gregory et al., 2009). There-fore, allanite and epidote formed under UHP conditions, duringwhich feldspar is not stable, shows relatively high Eu/Eu⁄

ratios and Sr concentrations. The weak negative Eu anomalyand high Sr concentrations (Fig. 9) in allanite indicate meta-morphic origin. Nearly all the epidote-group minerals have Srcontents higher than 1000 ppm, except for some epidote fromShaunghe and Fangshan. Moreover, the Sr contents in allanitefrom the Dabie-Sulu orogen, which may exceed one percent,confirm the metmorphic origin (Fig. 9b).

Meanwhile, the high common lead concentrations in allanitefrom Shima (Dabie) result in high uncertainty of the geochronolog-ical results. Nevertheless, the less-precise ages around 200 Ma,clearly distinguished from the Neoproterozoic ages for the gneiss.These results suggest that the allanite must have formed in Triassictimes.

Fig. 8. Diagrams of allanite (the crystal in Fig. 2k and l) ages for granite of Jingshan, a, b for the whole crystal, c, d for the rim of the crystal: (a) 232Th/206Pbc and 208Pb/206Pbc

isochronal age; (b) Tera-Wasserburg regression age; (c) 207Pb corrected 208Pb-232Th weighted age; (d) Histogram of ages.

Fig. 7. Ages of allanite from Shima gneiss in Dabie orogen: (a) 232Th/206Pbc and 208Pb/206Pbc isochronal age (206Pbc is common 206Pb); (b) Tera - Wasserburg regression age.

H. Guo et al. / Journal of Asian Earth Sciences 135 (2017) 243–256 251

5.2. The origin of allanite from the Jingshan granite

The mineral assemblage of the Jingshan granite is character-ized by K-feldspar, quartz and plagioclase with variable amountsof biotite, garnet, allanite, epidote, and accessory zircon, apatite,titanite, and magnetite (Yang et al., 2010; Liu et al., 2012; Xuet al., 2013). The protolith of the Jingshan granite could be

recognized as a biotite gneiss from the Dabie-Sulu orogen, basedon evidence from zirconology (Li et al., 2014; Xu et al., 2005;Yang et al., 2010).

Petrographic observations and back-scattered electronimages show allanite from Jingshan with corrosion cores andzoned magmatic rims (Fig. 2k and l). Common 208Pb concentra-tions are up to 70% in the core and less than 30% in the rim.

Fig. 9. (a) La/Sm and Th/U, La/Sm and Eu/Eu⁄ diagrams for studied samples (XFallanite derived from Guo et al. (2014); DM derived from Hermann (2002); PEderived from Gregory et al. (2009); La-VdT-2 derived from Rubatto et al. (2008);other data derived from Gregory et al. (2012); note that the data in Gregory et al.(2012) are in average and the area in the diagram is not categorical). (b) Srconcentration in epidote-group minerals from this study and referrences. (Seeabove-mentioned references for further information.)

252 H. Guo et al. / Journal of Asian Earth Sciences 135 (2017) 243–256

High common lead in the cores restrict accurate dating, butthe rims yield consistent ages of 154 ± 3 Ma, in agreement withpreviously reported zircon ages (Xu et al., 2005, 2013; Li et al.,2014). The trace elements in the cores and the rims show sim-ilar patterns (Fig. 5d and Fig. 9). The La/Sm, Th/U and Eu/Eu⁄

ratios plot between the fields for metamorphic and magmaticallanite (Fig. 9a). Moreover, the Sr concentration in all samplesis less than 1000 ppm (Table 5 and Fig. 9b), i.e. much lowerthan typical metamorphic allanite (e.g., Nagasaki and Enami,1998; Hermann, 2002; Rubatto et al., 2008) and comparablewith magmatic allanite (e.g., Guo et al., 2014; Rao and Babu,1978; Hoshino et al., 2007). In view of the above observations,

the corrosion cores of the Jingshan allanite are probably peri-tectic and the rims are magmatic in origin. The isochron andTera-Wasserburg regression ages of the whole grain, as wellas the average single spot age of the Jingshan allanite rim bothare consistent with 160 Ma and are in accordance with the ageof the granite (Guo and Li, 2009; Xu et al., 2013; Yang et al.,2010; Li et al., 2014). The common lead rich allanite cores andrelatively common lead depleted rims indicate similar Jurassicages (Fig. 8) and are consistent also with the age of garnetfrom the Jingshan granite (Xu et al., 2013).

5.3. Implications for the Dabie-Sulu orogen evolution

The collision between the North China Craton (NCC) and theYangtz Craton (YZ) can be divided into (Fig. 10): (1) a progrademetamorphic stage (220–245 Ma), (2) a retrograde metamorphicstage (185–220 Ma), and (3) a magmatic stage which affectedthe south-eastern NCC (150–161 Ma). Allanite in eclogite(Romer and Xiao, 2005; Wang et al., 2006; Gao et al., 2013),gneiss (Liu et al., 1999; Xia et al., 2008) and granite (Xuet al., 2013) may have grown during more than one stages(Fig. 10).

Allanite-epidote crystals in eclogite from the CCSD (Romerand Xiao, 2005; Wang et al., 2006) probably formedthroughout the entire metamorphic cycle, as evidenced bygarnet inclusions and initial Pb-Sr(-Nd) isotopic hetero-geneities in the allanite-epidote grains. In this study wedemonstrated that allanite from the UHP gneiss must be ofmetamorphic origin based on U-Th-Pb geochronology, traceelement characteristics and common lead concentrations. Thisfinding argues against a magmatic origin as suggested by Liuet al. (1999).

Allanite from the Jingshan granite formed as the result ofJurassic magmatism and is assumed not to be a relict of thesubducted gneiss, contrary to the formation of zircon (Xuet al., 2005, 2013; Yang et al., 2010). Nevertheless, the highcommon 208Pb and trace element characteristics of the Jingshanallanite might have been inherited from the re-molten sub-ducted gneiss from the Yangtz Craton (YZ). The zircon in Jing-shan granite inherited the residue zircon of Neoproterozoicmagmatism and Triassic metamorphism (Wang et al., 2013),but the allanite did not. This implies that the allanite in thesubducted gneiss was remolten at 700–710 �C (Li et al., 2014),but grew again during the emplacement of the Jingshan granite,and inherited the trace element content of the gneissic allanitefrom the Dabie-Sulu orogen. Allanite did not record age infor-mation from Triassic metamorphism in its protolith due to itslower stability than zircon, but the peritectic and magmaticprocesses during the initial stage of granite formation couldbe recorded. The appearance of allanite-epidote in the originalrocks makes it a potential tool to track the subduction processand related magmatism.

6. Conclusions

Systematic petrological, geochronological and geochemicalinvestigations on allanites from both gneiss and granite in the cen-tral East China lead us to draw the following conclusions:

(1) High Sr, low La/Sm and Th/U, high Eu/Eu⁄ and commonlead characteristics of allanite demonstrate a metamor-phic origin of the allanite-epidote in gneiss from theDabie-Sulu UHP metamorphic belt. Large allanite grainsin the Jingshan granite show a corrosion core and a mag-matic rim, with common 208Pb of up to 70% in the former

Table 5Representative Allanite and epidote trace elements for studied samples (in ppm, – below the detection limit, n.a. – not analyzed).

Sample SM SH FS JS

2-2.1 2-2.2 2-2.9 2-2.10 Aln Aln Ep Ep 1 2 8 9 1 2 6 7

Li 2.1 1.7 0.3 0.6 2.5 0.7 7.0 32.7 8.9 7.0 9.1 5.2 5.2 5.1 7.9 6.2Sc n.a. n.a. n.a. n.a. 24 44 3030 1608 21 55 98 38 229 235 242 192V 32 31 46 40 8 7 1584 757 27 37 56 25 85 123 125 174Cr 3.9 19 4.5 14 0.7 0.9 – – 27 18.8 6.1 19.3 16.9 9.2 21.1 121Co 3.2 2.6 – 0.1 0.4 0.8 57 – 2.8 2.4 0.5 0.4 1.3 2.1 2.9 5.3Ni 5.7 – – – 0 0 – – 4.4 3.2 – 15 – 14.6 – –Cu – 1.2 – – – 0.93 – – 123 54 115 60 – – – 1.7Zn 100 84 11 19 573 605 90 48 310 311 343 176 352 249 216 229Ga 753 633 71 87 2106 2046 240 106 598 1496 1634 469 1289 1773 1505 1554Rb – – – 0.1 0.07 0.14 – – 0.12 0.9 1.12 0.15 – 0.39 – 0.11Sr 8765 9217 4137 5056 7779 6705 204 254 2589 7767 7816 2424 434 392 406 500Y 431 562 748 968 1204 976 1961 566 2319 3865 4106 1952 1332 1951 1802 1415Zr 2.4 2.6 5.9 5 3.9 3.1 217 227 32 76 364 20,356 5.1 8.8 8.6 8.5Nb – – – – – 0.05 – – 0.59 1.29 2.23 2.03 – – – –Cs – – – – – – – – – – – – – – – –Ba 86 88 13 16 80 70 8 6 387 1197 1404 256 – – 1.4 4.2La 15,997 13,226 413 703 40,257 39,786 2893 837 10,442 31,410 34,341 9007 22,897 32,328 29,439 32,182Ce 34,186 23,254 907 1485 67,422 66,233 5362 1585 25,423 79,149 79,633 18,625 40,267 57,358 52,486 54,433Pr 3023 2340 113 182 7504 7306 693 181 2847 7067 7726 2100 4032 5816 5285 5144Nd 10,867 8525 506 770 25,137 24,194 2866 699 11,724 26,785 28,003 7876 14,470 19,777 18,237 16,726Sm 1282 1140 124 180 2393 2155 633 137 2036 3748 3870 1128 2081 2780 2471 2058Eu 154 137 20 30 261 230 268 55 346 554 582 193 257 280 271 237Gd 668 672 140 214 1187 1010 630 129 1305 2225 2205 754 1262 1728 1521 1272Tb 53 57 25 37 98 80 269 59 130 218 216 82 107 150 130 105Dy 161 196 142 204 355 283 667 158 526 870 887 388 390 569 488 404Ho 17 23 28 37 48 39 377 102 76 128 140 66 54 79 72 54Er 26 33 59 79 92 75 400 127 148 270 304 145 92 153 138 117Tm 2.1 2.0 8.0 10.1 8.5 7.3 295 105 16 32 37 16 9 14 13 10Yb 11 12 52 67 49 45 294 115 89 209 252 114 43 72 84 57Lu 1.2 1.2 7.8 8.8 6 6 234 96 14 37 47 21 6 9 10 9Hf 0.28 – 0.34 0.16 – 0.15 994 753 0.82 0.5 3.15 374 0.06 0.07 0.44 0.24Pb 551 533 262 319 790 853 248 270 800 1125 2380 1463 170 162 134 106Th 3942 3035 109 205 5175 5167 363 103 1498 5582 7403 2059 6083 7995 6106 4642U 232 243 32 51 101 61 195 40 507.3 688.2 744 377 327 124 90 66

Table 6Allanite isotope ratios, common lead content and ages from Shima.

No. Measured value 204Pbcorrection

207Pb/206Pb 1r 208Pb/206Pb 1r 207Pb/235U 1r 206Pb/238U 1r 208Pb/232Th 1r 232Th/206Pb 1r f208 1r

2.1 0.87966 0.020693 2.546 0.065 138.080 3.99 1.13183 0.02122 0.05294 0.00185 48.13 1.264 0.81 0.012.2 0.86717 0.019910 2.406 0.061 93.179 2.65 0.77490 0.01482 0.06206 0.00218 39.26 1.068 0.87 0.012.3 0.86709 0.020437 2.502 0.064 137.354 4.04 1.14474 0.02174 0.05132 0.00178 48.91 1.293 0.78 0.012.4 0.87275 0.020326 2.507 0.064 117.891 3.43 0.97390 0.01919 0.05223 0.00183 48.25 1.293 0.81 0.022.5 0.83356 0.019865 2.139 0.055 48.077 1.40 0.41480 0.00805 0.13294 0.00472 16.11 0.431 0.91 0.022.6 0.84277 0.019883 2.194 0.057 58.294 1.65 0.50084 0.00930 0.09242 0.00322 23.73 0.622 0.91 0.012.7 0.85704 0.019919 2.297 0.058 75.537 2.15 0.63553 0.01279 0.07774 0.00270 29.65 0.782 0.89 0.012.8 0.86423 0.019915 2.316 0.059 112.493 3.28 0.94445 0.01811 0.07949 0.00278 29.13 0.764 0.90 0.012.9 0.88081 0.020174 2.292 0.058 151.138 4.31 1.23210 0.02295 0.09490 0.00330 24.21 0.631 0.88 0.012.10 0.86262 0.020313 2.302 0.060 85.220 2.45 0.71549 0.01402 0.07988 0.00278 28.84 0.772 0.84 0.022.11 0.81835 0.019010 2.127 0.054 43.811 1.25 0.38627 0.00757 0.09145 0.00318 23.23 0.606 0.93 0.012.12 0.81362 0.019022 2.099 0.054 36.906 1.05 0.32568 0.00608 0.09899 0.00349 21.30 0.565 0.89 0.012.13 0.87316 0.020567 2.248 0.058 123.576 3.57 1.02019 0.01915 0.10109 0.00351 22.30 0.584 0.91 0.012.14 0.85544 0.019420 2.301 0.058 109.821 3.11 0.92804 0.01762 0.07949 0.00276 28.93 0.753 0.88 0.012.15 0.84812 0.019732 2.256 0.058 88.088 2.55 0.75379 0.01489 0.08282 0.00290 27.41 0.727 0.86 0.012.16 0.86595 0.019971 2.302 0.058 115.204 3.54 0.96371 0.02091 0.07791 0.00271 29.66 0.770 0.88 0.022.17 0.87565 0.020618 2.448 0.063 206.627 6.45 1.70167 0.03714 0.06453 0.00226 38.10 1.003 0.83 0.012.18 0.86533 0.019945 2.265 0.058 102.879 3.16 0.85079 0.01734 0.10062 0.00352 22.56 0.596 0.89 0.022.19 0.87333 0.020061 2.273 0.058 165.866 4.73 1.36849 0.02535 0.09295 0.00323 24.56 0.637 0.89 0.022.20 0.87660 0.020133 2.309 0.058 166.889 4.84 1.36901 0.02660 0.08709 0.00304 26.58 0.688 0.89 0.013.1 0.88363 0.020716 2.465 0.063 140.857 4.04 1.15441 0.02211 0.06507 0.00227 38.09 1.027 0.84 0.013.2 0.88093 0.020376 2.456 0.062 211.825 6.30 1.73201 0.03415 0.06436 0.00223 38.36 0.998 0.77 0.013.3 1.88093 1.020376 3.456 0.065 211.825 6.30 2.73201 0.03415 0.06436 0.00199 38.36 0.998 0.84 0.013.4 2.88093 2.020376 4.456 0.056 211.825 6.30 3.73201 0.03415 0.06436 0.00485 38.36 0.998 0.90 0.013.5 3.88093 3.020376 5.456 0.059 211.825 6.30 4.73201 0.03415 0.06436 0.00309 38.36 0.998 0.89 0.023.6 4.88093 4.020376 6.456 0.058 211.825 6.30 5.73201 0.03415 0.06436 0.00269 38.36 0.998 0.84 0.013.7 5.88093 5.020376 7.456 0.060 211.825 6.30 6.73201 0.03415 0.06436 0.00297 38.36 0.998 0.87 0.013.8 6.88093 6.020376 8.456 0.058 211.825 6.30 7.73201 0.03415 0.06436 0.00367 38.36 0.998 0.87 0.013.9 7.88093 7.020376 9.456 0.078 211.825 6.30 8.73201 0.03415 0.06436 0.00199 38.36 0.998 0.74 0.033.10 8.88093 8.020376 10.456 0.071 211.825 6.30 9.73201 0.03415 0.06436 0.00168 38.36 0.998 0.80 0.013.11 9.88093 9.020376 11.456 0.056 211.825 6.30 10.73201 0.03415 0.06436 0.00435 38.36 0.998 0.93 0.013.12 10.88093 10.020376 12.456 0.059 211.825 6.30 11.73201 0.03415 0.06436 0.00260 38.36 0.998 0.83 0.01

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Table 7Allanite isotope ratios, common lead content and ages from Jingshan.

No. Measured value 204Pb correction 204Pb correction

207Pb/206Pb

1r 208Pb/206Pb 1r 207Pb/235U

1r 206Pb/238U

1r 208Pb/232Th

1r 232Th/206Pb 1r f208 1r 208Pb⁄/232Th

1r Age 1r f206 1r f208 1r Age 1r

4 0.680 0.0211 6.6456 0.1829 9.986 0.4005 0.1079 0.0026 0.0106 0.0004 627.75 21.72 0.251 0.004 0.00792 0.00027 159 5.4 0.791 0.034 0.247 0.013 160 5.92 0.688 0.0236 6.512 0.1775 9.326 0.3711 0.1012 0.0025 0.0105 0.0003 618.26 21.61 0.253 0.003 0.00784 0.00026 158 5.3 0.801 0.038 0.256 0.014 157 6.027 0.700 0.0226 6.6324 0.1825 10.012 0.3971 0.1043 0.0024 0.0103 0.0003 638.04 21.85 0.236 0.003 0.00786 0.00026 158 5.3 0.817 0.037 0.256 0.013 154 5.826 0.713 0.0248 6.7432 0.1843 9.726 0.4038 0.1011 0.0024 0.0101 0.0003 662.44 22.59 0.232 0.004 0.00772 0.00026 155 5.3 0.833 0.041 0.257 0.014 151 5.828 0.732 0.0259 6.9009 0.2019 9.914 0.4142 0.1013 0.0025 0.0102 0.0003 677.52 24.67 0.235 0.003 0.00780 0.00026 157 5.3 0.857 0.043 0.258 0.015 152 5.95 0.727 0.0242 6.712 0.1892 9.523 0.3846 0.0965 0.0023 0.0107 0.0004 626.91 21.67 0.265 0.003 0.00785 0.00027 158 5.4 0.851 0.04 0.263 0.014 158 6.13 0.736 0.0238 6.7548 0.1837 11.922 0.4943 0.1185 0.003 0.0108 0.0004 627.01 21.69 0.232 0.003 0.00826 0.00028 166 5.6 0.862 0.039 0.265 0.014 159 6.130 0.725 0.0238 6.4316 0.1768 9.761 0.3862 0.0992 0.0022 0.0102 0.0003 627.31 21.92 0.237 0.003 0.00778 0.00026 157 5.3 0.848 0.039 0.274 0.015 149 5.829 0.712 0.0243 6.0206 0.1639 10.588 0.4354 0.1095 0.0028 0.0106 0.0004 564.55 19.62 0.219 0.003 0.00830 0.00028 167 5.6 0.832 0.04 0.287 0.016 153 6.16 0.738 0.0253 5.9207 0.164 11.530 0.473 0.1145 0.0027 0.0111 0.0004 531.27 18.48 0.296 0.004 0.00783 0.00027 158 5.4 0.865 0.042 0.303 0.017 156 6.422 0.745 0.0246 5.9391 0.1902 14.664 0.588 0.146 0.0038 0.0108 0.0004 548.82 20.67 0.248 0.004 0.00809 0.00027 163 5.5 0.873 0.041 0.305 0.017 150 6.324 0.782 0.0265 5.8921 0.1602 14.542 0.6087 0.1382 0.0039 0.0109 0.0004 545.79 19.37 0.304 0.004 0.00757 0.00026 152 5.2 0.92 0.045 0.324 0.018 148 6.431 0.698 0.0233 5.0083 0.1376 11.154 0.4995 0.1167 0.0032 0.0114 0.0004 437.02 15.20 0.349 0.004 0.00743 0.00026 150 5.2 0.814 0.038 0.338 0.018 152 6.61 0.675 0.0212 4.4365 0.1153 9.375 0.3676 0.1017 0.0022 0.0122 0.0004 364.91 12.38 0.389 0.004 0.00744 0.00025 150 5.1 0.786 0.034 0.368 0.018 155 6.925 0.781 0.026 5.1047 0.1496 16.032 0.6393 0.1519 0.0038 0.0122 0.0004 419.85 15.19 0.383 0.005 0.00750 0.00026 151 5.2 0.919 0.044 0.374 0.021 153 7.323 0.833 0.0254 4.5784 0.1294 22.146 0.8733 0.1951 0.0047 0.0136 0.0005 335.16 11.85 0.465 0.007 0.00726 0.00026 146 5.3 0.984 0.045 0.446 0.024 151 8.320 0.823 0.0236 3.607 0.0925 22.739 0.8681 0.2022 0.0043 0.0163 0.0005 220.95 7.39 0.529 0.008 0.00767 0.00029 154 5.8 0.971 0.041 0.559 0.028 145 1015 0.700 0.0196 2.9597 0.0713 9.827 0.5928 0.1004 0.0039 0.0172 0.0007 176.45 6.02 0.605 0.012 0.00680 0.00033 137 6.6 0.817 0.032 0.573 0.026 148 118 0.665 0.0185 2.7953 0.0674 7.756 0.3444 0.0837 0.002 0.0172 0.0006 161.57 5.20 0.567 0.007 0.00743 0.00028 150 5.6 0.773 0.029 0.574 0.026 147 107 0.820 0.0228 3.4899 0.0869 24.562 0.9284 0.2166 0.0044 0.0174 0.0006 199.64 6.61 0.566 0.006 0.00756 0.00027 152 5.5 0.967 0.04 0.575 0.028 149 119 0.802 0.0217 3.3944 0.0816 23.026 0.8683 0.2084 0.0042 0.0175 0.0006 192.62 6.26 0.541 0.006 0.00803 0.00029 162 5.8 0.945 0.038 0.578 0.027 148 1116 0.792 0.0224 3.2366 0.0815 20.022 0.7594 0.1848 0.0037 0.0178 0.0006 181.43 5.99 0.531 0.007 0.00834 0.00030 168 6.2 0.933 0.038 0.599 0.029 144 1118 0.723 0.0206 2.879 0.0712 10.831 0.4157 0.1088 0.0024 0.0187 0.0006 153.95 5.06 0.611 0.008 0.00727 0.00028 146 5.7 0.845 0.034 0.61 0.029 147 1221 0.834 0.0243 3.3087 0.0918 36.129 1.3942 0.3163 0.0069 0.0183 0.0006 182.90 7.58 0.547 0.006 0.00829 0.00031 167 6.2 0.985 0.043 0.618 0.032 141 1319 0.808 0.023 3.1462 0.0791 25.528 0.9799 0.2326 0.0052 0.0183 0.0006 172.91 5.74 0.597 0.007 0.00736 0.00028 148 5.6 0.952 0.04 0.628 0.031 137 1213 0.828 0.0228 3.2104 0.0758 25.754 0.9886 0.2254 0.0044 0.0184 0.0006 174.56 5.62 0.603 0.008 0.00730 0.00028 147 5.7 0.977 0.04 0.632 0.03 136 1212 0.826 0.0229 3.0889 0.0749 26.004 0.9876 0.2291 0.0047 0.0198 0.0007 156.55 5.12 0.601 0.008 0.00790 0.00031 159 6.2 0.974 0.04 0.655 0.031 137 1317 0.696 0.0198 2.5567 0.0623 10.875 0.5853 0.1127 0.0038 0.0208 0.0007 122.80 3.99 0.687 0.01 0.00651 0.00030 131 6.0 0.812 0.032 0.66 0.031 142 1414 0.669 0.0182 2.3554 0.0584 7.880 0.3339 0.0849 0.0019 0.0208 0.0007 112.53 3.62 0.674 0.008 0.00679 0.00030 137 6.0 0.778 0.029 0.686 0.031 132 1411 0.818 0.0226 2.9189 0.0703 25.234 0.9598 0.2233 0.0046 0.0233 0.0008 125.55 4.34 0.731 0.009 0.00627 0.00030 126 6.0 0.965 0.039 0.687 0.033 147 1610 0.840 0.0236 2.8445 0.0697 33.026 1.2763 0.2882 0.006 0.0236 0.0008 120.16 3.97 0.685 0.01 0.00744 0.00034 150 6.9 0.992 0.042 0.724 0.035 131 1732 0.856 0.0247 2.7572 0.0699 38.271 1.655 0.327 0.0096 0.0299 0.0011 92.42 3.11 0.724 0.008 0.00825 0.00038 166 7.7 1.012 0.044 0.763 0.038 143 24

The first 16 data are the rim of allanite and the last 16 data are the core of allanite.

254H.G

uoet

al./Journalof

Asian

EarthSciences

135(2017)

243–256

Fig. 10. Mesozoic tectonic model and allanite growth of Dabie-Sulu orogen and theeastern North China Craton (modified from Yang et al., 2010). (a) Progrademetamorphism period (220–245 Ma): thickness of the northeasten NCC was causedby subduction of the YC beneath the NCC, allanite may form in the eclogite (Romerand Xiao, 2005; Wang et al., 2006) and gneiss (this study) during this period. (b)Retrograde metamorphism period (180–220 Ma): the break-off of the subductionzone and the quick exhumation of ultrahigh pressure metamorphic rocks due tofloatation. Fluid exsolution happened during this period, with allanite formationmainly in the retrograde metamorphism stage. (c) Formation of granitoids in thenortheasten NCC (Bengbu, 150–161 Ma): the upwelling of asthenosphere andpartial melting and the exhumated YC slab, allanite formed from the remelted YCcrust material (Xu et al., 2013; this study). M-moho; NCC-the North China Craton;YC-the Yangtze Craton; NW-northwest; SE-southeast; UHPM-ultrahigh pressuremetamorphic rocks.

H. Guo et al. / Journal of Asian Earth Sciences 135 (2017) 243–256 255

and less than 30% in the latter, indicating a combinationof peritectic and magmatic origin during Jurassic magma-tism for this mineral.

(2) Although high common lead concentrations in metamor-phic allanite limit the accurate geochronology, a Triassicmetamorphism age for the gneissic allanite was firstreported in this study, which provides important informa-tion for solving the controvery regarding the origin ofallanites in the Dabie-Sulu orogen and may have impor-tant implications for the interpretation of any geochemi-cal data from the allanites.

(3) In combination with previous studies, allanite-epidote for-mation may have involved all the metamorphic processesof the Dabie-Sulu orogen as well as the magmatism aftercontinental subduction. So far, allanite may not provide asmuch age information as zircon. Nevertheless, the presentstudy shows that, if high precision geochronology of highcommon lead allanite is achieved, allanite may play animportant role as a supplement to other accessory minerals(e.g., zircon) in tracking the subduction process and relatedmagmatism.

Acknowledgments

We thank J. Tian for help using the SEM in the EnvironmentSEM Lab at USTC, and Drs. E. Posner and AM van den Kerkhof forEnglish polishing. We are grateful to Prof. MF Zhou and two anony-mous reviewers for their thoughtful comments that significantly

improved the manuscript. The study was financially supportedby grants of NSFC – China (41172067, 41473033 and 41273037)for Yilin Xiao, and the China Scholarship Council (CSC) programfor Haihao Guo.

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