(Volume)38, (Number)4, (SUM)143 (Pages)939~953, 2014, 11(November, 2014) 大地构造与成矿学 Geotectonica et Metallogenia A : U-Pb Hf 李艳军 1, 魏俊浩 1 1,, 陈华勇 2, 李欢

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1 (Volume)38, (Number)4, (SUM)143 (Pages)939~953, 2014, 11(November, 2014) 大地构造与成矿学 Geotectonica et Metallogenia A : U-Pb Hf 李艳军 1, 魏俊浩 1 1,, 陈华勇 2, 李欢 1 1,, 陈冲 3, 侯本俊 (1., ; 2., ; 3., ; 4., ) 4 摘要 :, Hf, LA-ICP-MS U-Pb 103±1 Ma(MSWD=0.5),,, SiO %~74.98%, K 2 O+Na 2 O=7.56%~8.08%, A/CNK=1.06~1.10, Zr Hf U Th, Ba Sr REE Eu (δeu=0.13~0.25), LREE HREE A Hf ε Hf (t)= 2.7~0.6, T DM2 =925~1095 Ma Hf,, 关键词 : A ; U-Pb ; ; ; 中图分类号 : P597 文献标志码 : A 文章编号 : (2014) , (, 2001) 4, A ( 1,, 2001),, Rb-Sr Ar-Ar 60~104 Ma (, 2002;, 2006; Qu et al., 2002), (, 2001; Qu et al., 2002), Rb-Sr Ar-Ar 93±5 Ma 63.9±0.2 Ma (, 2006), Ar-Ar 75.2±0.3 Ma (Qu et al., 2002) 60.6±0.4 Ma (, 2006), 收稿日期 : ; 改回日期 : 项目资助 : ( : ) ( ) ( : CUG110832, CUG ) 第一作者简介 : (1982 ),,, liyanjun21023@163.com

2 940 第 38 卷,,, Nb Ta Ga Y, Sr Eu (Qu et al., 2002), : S (, 2003;, 2006); A (, 2001;, 2002;, 2008; Qu et al., 2002), (, 2001; Qu et al., 2002), Sn-Ag- Pb-Zn,, 5 km, (, 2003;, 2006;, 2008; Qu et al., 2002) ( 2b), 1.5 km 2, LA-ICP-MS U-Pb Hf,,, 1 地质概况及岩石学特征 ( 1),, (T 3 q) (T 3 t) (T 3 lm), ( 2a), NNW NW NEE ( 2a) NNW,,,,,, NW NNW, NEE,, NNW, NW,, NNW ( 2a), (, 2002;, 1. ; 2. ; 3. ; 4. ; 5. ; 6. ; 7. ; 8. ; 9. ; 10. ; 11. ; 12. ; 13. ; (, 2001 ) Fig.1 Simplified geological and tectonic map of the Yidun island arc belt 2003;, 2006;, 2008; Qu et al., 2002), ( 3),,,, 3~10 mm, 15%;,, 3~13 mm, 10%;,, 3~12 mm, 10%

第 4 期李艳军等 : 义敦岛弧带夏塞早白垩世 A 型花岗岩成因 : 锆石 U-Pb 年代学地球化学及 Hf 同位素制约 941 1. ; 2. ; 3. ; 4. ; 5. ; 6. ; 7. ; 8. ; 9. ; 10. A ; 11. ; 12. ; 13. Ag-Pb-Zn ; 14. ; 15. Fig.

3 第 4 期李艳军等 : 义敦岛弧带夏塞早白垩世 A 型花岗岩成因 : 锆石 U-Pb 年代学地球化学及 Hf 同位素制约 ; 2. ; 3. ; 4. ; 5. ; 6. ; 7. ; 8. ; 9. ; 10. A ; 11. ; 12. ; 13. Ag-Pb-Zn ; 14. ; 15. Fig.2 2 (a) (, 2004) (b) Simplified geological map showing the distribution of ore deposits in the Yidun island arc belt (a) and geological map of the Xiasai Silver-polymetallic deposit (b) (a) ; (b) Qr. ; Q. ; Pl. ; Bi. Fig.3 3 Micrographs taken under transmitted light of the phenocryst minerals and groundmass from the Xiasai granite, (20%±) (20%±) (20%±) (5%±);,, 1~4 mm;, 1~4 mm;,,, 1~3 mm;,,, 1~3 mm, 5% A (

4 942 第 38 卷, 2001; Qu et al., 2002) 2 分析方法 U-Pb XSG-5,,, (GPMR) (CL),, GPMR (LA-ICP-MS), 32 μm, U-Th-Pb He U-Th-Pb 91500, 29 Si, NIST610, Liu et al. (2010) ICPMSDataCal (Liu et al., 2010), Pb 206 Pb/ 238 U, 2σ 5, 100 g, 200 (XSG-7 ) PANalytical Axios Max ME-XRF06, Li 2 B 4 O 7 -LiBO 2,,, 1000 ;, X P 2 O %, 0.01%, 5% ME-MS81, LiBO 2, 1000,, Perkin Elmer Elan 9000 (ICP-MS), 10% Hf GPMR Neptune Plus MC-ICP-MS, 193 nm ArF GeoLas 2005, / Hf, 44 μm, 8Hz, Hu et al. (2012) 179 Hf/ 177 Hf = Yb/ 171 Yb= (Blichert-Toft et al., 1997) 179 Hf/ 177 Hf 173 Yb/ 171 Yb ICPM- SDataCal (Liu et al., 2010) ε Hf 176 Lu a 1 (Scherer et al., 2001), 176 Hf/ 177 Hf= Lu/ 177 Hf= (Blichert-Toft and Albarède, 1997); Hf (T DM2 ) 176 Hf/ 177 Hf = Lu/ 177 Hf = (Vervoort and Blichert-Tolf, 1999), 176 Lu/ 177 Hf=0.015 (Griffin et al., 2000) 3 分析结果 3.1 U-Pb,,, 100~200 μm, 300 μm, ~5.. 1 CL ( 4a):, ( XS );, (XS ) (XS-5-05), 18, U Th ~ μg/g ~ μg/g, Th/U 0.15~0.53( 1), Th/U (<0.1, Hoskin and Black, 2000; Griffin et al., 2004),, ( 4b), 207 Pb,, (Yuan et a1., 2003) XS-5-05 XS-5-07, Pb/ 238 U 100±3 Ma ~107±3 Ma, 206 Pb/ 238 U 103±1 Ma (MSWD=0.5) ( 4c), Rb-Sr Ar-Ar (, 2002;, 2006; Qu et al., 2002), U-Pb (104.5±2.4 Ma,, 2008), SiO %~74.98%, K 2 O+Na 2 O=7.56%~8.08%,

第 4 期李艳军等 : 义敦岛弧带夏塞早白垩世 A 型花岗岩成因 : 锆石 U-Pb 年代学地球化学及 Hf 同位素制约 943 Na 2 O=7.56%~8.08%, K 2 O/Na 2 O=1.44~1.74, ( 5a) Al 2 O 3 (12.98%~ 13.89%), CaO (1.07%~1.60%), A/CNK= 1.06~1.10, ( 5b) P 2 O 5 0.

5 第 4 期李艳军等 : 义敦岛弧带夏塞早白垩世 A 型花岗岩成因 : 锆石 U-Pb 年代学地球化学及 Hf 同位素制约 943 Na 2 O=7.56%~8.08%, K 2 O/Na 2 O=1.44~1.74, ( 5a) Al 2 O 3 (12.98%~ 13.89%), CaO (1.07%~1.60%), A/CNK= 1.06~1.10, ( 5b) P 2 O %~0.12%, SiO 2 TiO %~0.38%, FeO T 1.87%~2.80%, MgO 0.41%~0.62% CIPW,, A (, 2001; Qu et al., 2002) ~ μg/g ( μg/g), (HREE) 28.01~42.89 μg/g, (LREE) ~ μg/g, LREE/HREE 4.55~9.13 ( 2), LREE, HREE (La/Yb) N =4.11~10.73,, 206 Pb/ 238 U, Hf, ε Hf (t) Fig.4 4 (a) U-Pb (b) (c) Cathodoluminescence (CL) images of the representative zircons from the Xiasai granite (a), U-Pb concordia (b) and weighted age diagrams for the zircon grains from the Xiasai granite (c) 1. ; 2. ; 3. ; 4. ; 5. :, 2001 Qu et al., SiO 2 -K 2 O (a) ( Collins et al., 1982) A/CNK-A/NK (b) ( Maniar and Piccoli, 1989) Fig.5 SiO 2 -K 2 O (a) and A/CNK-A/NK (b) diagrams for the Xiasai granite

6 944 第 38 卷

7 第 4 期李艳军等 : 义敦岛弧带夏塞早白垩世 A 型花岗岩成因 : 锆石 U-Pb 年代学地球化学及 Hf 同位素制约 945 表 2 夏塞岩体主量元素 (%) 微量及稀土元素(μg/g) 分析结果 Table 2 Major (%) and trace element and REE(μg/g) compositions of the Xiasai granites A XSG-2 XSG-4 XSG-5 XSG-6 XSG-7 XSG-7-2 SiO TiO A1 2 O FeO T MnO MgO CaO K 2 O Na 2 O P 2 O LOI Total Na 2 O+K 2 O K 2 O/Na 2 O A/CNK Ga Rb Sr Y Zr Nb Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Th U Ga/Al Zr+Nb+Ce+Y Nb/Ta ΣREE LREE HREE LREE/HREE δeu (La/Yb) N (Gd/Yb) N : A/CNK=Al 2 O 3 /(Na 2 O+K 2 O+CaO) A (2001) Qu et al. (2002)

8 946 第 38 卷, (Gd/Yb) N, 0.92~ 1.42 Eu, δeu=0.13~0.25 ( 0.20) LREE HREE ( 6a), A (, 2001; Qu et al., 2002), (LILE) (HFSE), Rb Th U Ta Ba Nb Sr P Ti ( 6b) Ga, Ga/Al ~ 3.24, Zr Nb Ce Y, Zr+Nb+Ce +Y=368.70~ μg/g( 2) A (, 2001; Qu et al., 2002) 3.4 Hf U-Pb, LA-MC-ICP-MS Lu-Hf, 3 XS-5-03 XS-5-04, Lu/ 177 Hf ~ , Hf Hf/ 177 Hf ~ , ε Hf (t)= 2.7~0.6 ( 3, 7a), Hf t DM2 =925 ~1095 Ma ( 3), Table 3 表 3 夏塞岩体 LA-MC-ICPMS 锆石 Hf 同位素分析结果 LA-MC-ICPMS zircon Lu-Hf isotopic compositions of the Xiasai granite (Ma) 176 Yb/ 177 Hf ±2σ 176 Lu/ 177 Hf ±2σ 176 Hf/ 177 Hf ±2σ ε Hf (t) t DM2 f Lu/Hf XS XS XS XS XS XS XS XS XS XS XS XS XS A (2001) Qu et al. (2002) 6 (a) (b) ( Sun & McDonough, 1989) Fig.6 Chondrite-normalized REE patterns (a) and primitive mantle-normalized trace element diagram (b) for the Xiasai granites

9 第 4 期李艳军等 : 义敦岛弧带夏塞早白垩世 A 型花岗岩成因 : 锆石 U-Pb 年代学地球化学及 Hf 同位素制约讨论 4.1 A A Loiselle and Wones (1979), (alkaline) (anhydrous) (anorogenic), 30, A (2009) A, : (1), ; (2) ( Fe) ; (3),, FeO T /MgO Ga/Al, HFSE Y(Ce), Ba Sr Eu P Ti,, A,, 7 ε Hf (t) (a) t-ε Hf (t) (b) Fig.7 Histogram of zircon ε Hf (t) values and t-ε Hf (t) diagram for the Xiasai granites, HFSE, Ba Sr, REE Eu (2009) A Ga/Al 10 4 (2.86~3.24) 5 I S M A I S M A : (2001) Qu et al. (2002) 8 ( Whalen et al., 1987) Fig.8 Petrogenesis discrimination diagrams for the Xiasai granites

10 948 第 38 卷 Zr+Nb+Ce+Y (368.70~ μg/g) Whalen et al. (1987) A ( 2.60 μg/g 350 μg/g) 10 4 Ga/Al-Zr Ce K 2 O/MgO K 2 O+Na 2 O A ( 8) S A, (King et al., 1997) S,, S A (King et al., 1997), S P 2 O 5 ( 0.14%), Na 2 O ( 2.81%), P 2 O 5 (Chappell and White, 1992), A, A/CNK 1.06~1.10,, P 2 O 5 (0.06%~0.12%), Na 2 O (2.82%~3.16%), P 2 O 5 SiO 2 S, S I A, FeO T Zr I A (Whalen et al., 1987; King et al., 1997;, 2000;, 2009) A (FeO T ), 1.00%, (>800 ), I 1.00%, ( 764 ) (, 2000;, 2009) FeO T 1.87%~2.80%, Watson et al. (2006) Ti T Zr 800~1100 ( 1), A Zr 183~224 μg/g, King et al. (1997) Lachlen A (301 μg/g),, A Zr, King et al. (1997) A Zr 200 μg/g Rb Sr 386~424 μg/g 71.7~107 μg/g,, A A, 9 (, 2009), (, 1996, 2000; Yang et al., 2006) (K 2 O 4.54%~5.13%, 2),, ( 6), Nb/Ta 4.53~7.14 ( 2),, (, 1986) (2011) (2012) 1680±13 Ma SHRIMP U-Pb 1722±25 Ma LA-ICP-MS U-Pb,, ε Hf (t)= 2.7~0.6 ( 3), ε Hf (t)-t, Hf t DM2 =925~1095 Ma,, ( 7b) T Zr (800~1100 ), A, ( 5 6), Sm-Nd ε Nd (103 Ma)= 5.9~ 5.0( 4), (Qu et al., 2002) : (1) ; (2), A, Bryansky A/CNK 0.92~0.99 (Litvinovsky et al., 2002), A/CNK<1 (Li et al., 2004), A (2001, 2004),, 表 4 义敦岛弧带早白垩世 A 型花岗岩 Sm-Nd 同位素组成 Table 4 Sm-Nd isotope compositions of the early Cretaceous A-type granites in the Yidun island arc belt 147 Sm/ 144 Nd 143 Nd/ 144 Nd ε Nd (t) LX LX LX C C D030B D030B DM DM : Sm-Nd Qu et al. (2002), U-Pb 103 Ma

11 第 4 期李艳军等 : 义敦岛弧带夏塞早白垩世 A 型花岗岩成因 : 锆石 U-Pb 年代学地球化学及 Hf 同位素制约 949 A, Ba Sr P Ti Eu P Ti, Nb Ta, Nb Ta (Foley et al., 2000) Eu Sr-Ba ( 9a), Sr Ba, Sr Ba,, (Wu et al., 2003), La-(La/Yb) N ( 9b),, 4.2,, (, 2001) (238~210 Ma), ; 208 Ma,,, ; (138~73 Ma),, A ;,, (, 2001) Rb-Sr Ar-Ar 60~104 Ma (, 2002;, 2006; Qu et al., 2002), LA-ICP-MS U-Pb 103±1 Ma (MSWD=0.5), U-Pb (104.5±2.4 Ma,, 2008), (2001), A ( 5 6), A ( 8) Ga/Al R 1 Nb-Y-3 Ga ( 10), PA A2, A (Eby, 1992; Hong et al., 1996) Y/Nb 1.40~2.32, 1.2, (Eby, 1992) Y+Nb-Rb ( 11a), (Pearce, 1996; Förster et al., 1997) Rb/30- Hf-Ta 3 ( 11b),,, Pl. ; Kf. ; Bi. ; Hb. ; Zr. ; Sph. ; Ap. ; Allan. 9 Sr-Ba (a) La-(La/Yb) N (b) ( D Rollinson, 1993) Fig.9 Sr vs Ba (a) and La vs (La/Yb) N (b) diagrams for the Xiasai granites

12 950 第 38 卷 5 AA. ; PA. : (2001) Qu et al. (2002) 10 Ga/Al R 1 (a, 据 Hong et al., 1996) Nb-Y-3 Ga (b, 据 Eby, 1992) Fig.10 Ga/Al 10 4 vs R 1 (a) and Nb-Y-3 Ga (b) diagrams for the Xiasai granites 5 :, 2001 Qu et al., Y+Nb-Rb (a) Rb/30-Hf-Ta 3 (b) (a Pearce, 1996; b Harris et al., 1986) Fig.11 Y+Nb-Rb (a) and Rb/30-Hf-Ta 3 (b) diagrams for the Xiasai granites 5 结论 (1) LA-ICP-MS U-Pb 103±1 Ma, (2) Hf A,, (3), 致谢 : 论文承蒙中国科学院广州地球化学研究所彭头平副研究员及另外两位匿名审稿专家的审阅, 他们的宝贵意见和建议显著提高了本文质量, 野外工作过程中得到了四川夏塞银业有限责任公司全体领导与员工的帮助, 在此一并表示感谢参考文献 (References):,, , 24(2): ,,,,,,,,, :., 75(4): ,,,,,,, , 78(1): ,, A., 33(3): , , 5(3): , 22(2):

13 第 4 期李艳军等 : 义敦岛弧带夏塞早白垩世 A 型花岗岩成因 : 锆石 U-Pb 年代学地球化学及 Hf 同位素制约 951,,, , 32(1): ,, , 19(2): ,,, , 23(4): ,,,,, : LA-ICP-MS U-Pb., 36(3): ,, A., 19(4): ,,, : : ,, , 25(2): ,,,,,,,,, SHRIMP., 31(3): ,,,,, ( ), 35(1): Blichert-Toft J and Albarède F The Lu-Hf isotope geochemistry of chondrites and the evolution of the mantle-crust system. Earth and Planetary Science Letters, 148(1 2): Blichert-Toft J, Chauvel C and Albarède F Separation of Hf and Lu for high-precision isotope analysis of rock samples by magnetic sector-multiple collector ICP-MS. Contributions to Mineralogy and Petrology, 127(3): Chappell B W and White A J R I- and S-type granites in the Lachlan Fold Belt. Transactions of the Royal Society of Edinburgh: Earth Sciences, 83: Collins W J, Beams S D, White A J R and Chappell B W Nature and origin of A-type granites with particular reference to southeastern Australia. Contributions to Mineralogy and Petrology, 80(2): Eby G N Chemical subdivision of the A-type granitoids: Petrogenetic and tectonic implications. Geology, 20(7): Foley S F, Barth M G and Jenner G A Rutile/melt partition coefficients for trace elements and an assessment of the influedce of rutile on the trace element characteristics of subduction zone magmas. Geochimica et Cosmochimica Acta, 64(5): Förster H J, Tischendorf G and Trumbull R B An evaluation of the Rb vs. (Y+Nb) discrimination diagram to infer tectonic setting of silicic igneous rocks. Lithos, 40(2 4): Griffin W L, Belousova E A and Shee S Archean Crustal Evolution in the Northern Yilgarn Craton: U-Pb and Hf-isotope evidence from detrital zircons. Precambrian Research, 131(3 4): Griffin W L, Pearson N J, Belousova E, Jackson S E, van Achterbergh E, O Reilly S Y and Shee S R The Hf isotope composition of cratonic mantle: LAM-MC- ICPMS analysis of zircon megacrysts in kimberlites. Geochimica et Cosmochimica Acta, 64(1): Harris N B W, Pearce J A and Tindle A G Geochemical characteristics of collision-zone magmatism. Geological Society, London, Special Publications, 19: Hong D W, Wang S G, Han B F and Jin M Y Postorogenic alkaline granites from China and comparisons with anorogenic alkaline granites elsewhere. Journal of Southeast Asian Earth Sciences, 13(1): Hoskin P W O and Black L P Metamorphic zircon formation by solid-state recrystallization of protolith igneous zircon. Journal of Metamorphic Geology, 8(4): Hu Z C, Liu Y S, Gao S, Liu W G, Zhang W, Tong X R, Lin L, Zong K Q, Li M, Chen H H, Zhou L and Yang L Improved in situ Hf isotope ratio analysis of zircon using newly designed X skimmer cone and Jet sample cone in combination with the addition of nitrogen by laser ablation multiple collector ICP-MS. Journal of Analytical Atomic Spectrometry, 27: King P L, White A J R and Chappell B W Characterization and origin of aluminous A type granites of the Lachlan Fold Belt, southeastern Australia. Journal of Petrology, 38(3): Li X H, Chung S L, Zhou H W, Lo C H, Liu Y and Chen C H Jurassic intraplate magmatism in southern Hunan-eastern Guangxi: 40 Ar/ 39 Ar dating, geochemistry, Sr-Nd isotopes and implications for the tectonic evolution of SE China. Geological Society, London,

14 952 第 38 卷 Special Publications, 226(1): Litvinovsky B A, Jahn B M, Zanvilevich A N, Saunders A, Poulain S, Kuzmin D V, Reichow, M K and Titov A V Petrogenesis of syenite-granite suites from the Bryansky Complex (Transbaikalia, Russia): Implications for the origin of A-type granitoid magmas. Chemical Geology, 189(1 2): Liu Y S, Gao S, Hu Z C, Gao C G, Zong K Q and Wang D B Continental and Oceanic Crust Recycling-induced Melt-peridotite Interactions in the Trans-North China Orogen: U-Pb Dating, Hf Isotopes and Trace Elements in Zircons of Mantle Xenoliths. Journal of Petrology, 51(1 2): Loiselle M and Wones D Characteristics and origin of anorogenic granites. Geological of Society of America, 1979, 11(7): 468. Maniar P D and Piccoli P M Tectonic discrimination of granitoids. Geological Society of American Bulletin, 101: Pearce J A Source and settings of granitic rocks. Episodes, 19(4): Qu X M, Hou Z Q and Zhou S G Geochemical and Nd, Sr Isotopic Study of the Post-Orogenic Granites in the Yidun Arc Belt of Northern Sanjiang Region, Southwestern China. Resource Geology, 52(2): Rollinson H R Using geochemical data: evaluation, presentation, interpretation. Essex: Longman Scientific & Technical: Scherer E, Munker C and Mezger K Calibration of the lutetium-hafnium clock. Science, 293: Sun S S and McDonough W F Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes. Geological Society, London, Special Publications, 42: Vervoort J D and Blichert-Toft J Evolution of the depleted mantle: Hf isotope evidence from juvenile rocks through time. Geochimica et Cosmochimica Acta, 63(3 4): Watson E B, Wark D A and Thomas J B Crystallization Thermometers for Zircon and Rutile. Contributions to Mineralogy and Petrology, 151(4): Whalen J B, Currie K L and Chappell B W A-type granites: Geochemical characteristics, discrimination and petrogenesis. Contributions to Mineralogy and Petrology, 95(4): Wu F Y, Jahn B M, Wilde S A, Lo C H, Yui T F, Lin Q, Ge W C and Sun D Y Highly fractionated I-type granites in NE China (I): Geochronology and petrogenesis. Lithos, 66(3 4): Yang J H, Wu F Y, Chung S L, Wilde S A and Chu M F A hybrid origin for the Qianshan A-type granite, northeast China: Geochemical and Sr-Nd-Hf isotopic evidence. Lithos, 89(1 2): Yuan H L, Wu F Y, Gao S, Liu X M, Xu P and Sun D Y Determination of U-Pb age and rare earth element concentrations of zircons from Cenozoic intrusions in northeastern China by laser ablation ICP-MS. Chinese Science Bulletin, 48: Petrogenesis of the Xiasai Early Cretaceous A-type Granite from the Yidun Island Arc Belt, SW China: Constraints from Zircon U-Pb Age, Geochemistry and Hf Isotope LI Yanjun 1, WEI Junhao 1, CHEN Huayong 1, 2, LI Huan 1, CHEN Chong 1, 3 and HOU Benjun 4 (1. Faculty of Earth Resources, China University of Geosciences, Wuhan , Hubei, China; 2. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou , Guangdong, China; 3. Wuhan Center, China Geological Survey, Wuhan , Hubei, China; 4. Xiasai Mining Co. Ltd., Sichuan Province, Ganzi , Sichuan, China) Abstract: Many Late Mesozoic granites distribute in the Yidun island arc belt, SW China. However, in situ zircon U-Pb ages and Hf isotopic data of these granites have rarely been reported so far. As lately reported granite from the central segment of the Yidun island arc belt, the Xiasai granite has a close genetic relationship with the Xiasai Ag-Pb-Zn

15 第 4 期李艳军等 : 义敦岛弧带夏塞早白垩世 A 型花岗岩成因 : 锆石 U-Pb 年代学地球化学及 Hf 同位素制约 953 polymetallic deposit. This paper presents (1) laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb age for the Xiasai granite to determine precisely the time of the magmatism, (2) geochemical and Hf isotope data for the Xiasai granite to constrain the petrogenesis and tectonic setting. The LA-ICP-MS analyses of zircon from the Xiasai granite yielded a weighted mean 206 Pb/ 238 U age of 103±1 Ma (MSWD=0.5), indicating that it was emplaced in the Early Cretaceous. Petrography and chemical compositions of the granites show that they belong to high-k calc-alkaline series and are characterized by high silicon, enrichment of alkaline and iron but depletion in calcium and magnesium. Their SiO 2 and K 2 O+Na 2 O contents are 72.94%-74.98% and 7.56%-8.08%, respectively. The A/CNK values vary from 1.06 to 1.10, show a weak peraluminous affinity. The granitic rocks are enriched in high field strength elements (e.g. Zr and Hf) and large ion lithophile elements (e.g. U and Th) but depleted in Ba, Sr, P, and Ti. REEs are characterized by significant negative Eu anomalies (δeu= ) and exhibit right-inclined patterns with LREE enrichment but HREE depletion. Mineralogy and geochemistry of the rocks show an affinity to aluminous A-type granite, similar to other Late Cretaceous A-type granites such as the Rongyicuo, Lianlong and Ruorolong granites in the Yidun island arc belt. Zircon Hf isotopic compositions of the Xiasai granite are characterized by ε Hf (t) values varying from 2.7 to 0.6 and the two-stage model ages (T DM2 ) of 925 Ma to 1095 Ma, implying that different source materials have contributed to the magma genesis. Integrated geological, geochemical and isotopic data suggest that the Xiasai A-type granite is most likely generated via a two-stage process, including formation of parental magma by mixing of an asthenosphere-derived magma and a crustal-derived felsic magma in the deep crust, followed by intensive magmatic differentiation of the parental magma. These granites are likely to have been generated in a post-collisional extensional tectonic setting related to arc-continent collision during the Early Cretaceous. Keywords: aluminous A-type granite; zircon U-Pb dating; petrogenesis; post-collisional extension; Yidun island arc belt 大地构造与成矿学 2015 年起变更为双月刊 , lhzd@public.tpt.tj.cn EI ddgz@gig.ac.cn ddgz02@163.com

GeologicalScienceandTechnologyInformation Vol.37 No.3 May 2018 doi: /j.cnki.dzkq ,,,. [J].,2018,37(3):13-20.,,, (, )

37 3 2018 5 GeologicalScienceandTechnologyInformation Vol.37 No.3 May 2018 doi:10.19509/j.cnki.dzkq.2018.0302,,,. [J].,2018,37(3):13-20.,,, (, 510080) : SN NWW U-Pb (148.6±4.1)Ma(MSWD=1.3) (85.7±2.0)Ma(MSWD=1.4)