(Volume)38, (Number)1, (SUM)140 (Pages)168~180, 2014, 2(February, 2014) 大地构造与成矿学 Geotectonica et Metallogenia 1, 2, 蔡永丰 3 2, 4 1,, 王岳军, 刘汇川 3, 马莉燕 5 1

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1 (Volume)38, (Number)1, (SUM)140 (Pages)168~180, 2014, 2(February, 2014) 大地构造与成矿学 Geotectonica et Metallogenia 1, 2, 蔡永丰 3 2, 4 1,, 王岳军, 刘汇川 3, 马莉燕 5 1,, 邢晓婉 3, 刘雷 (1., ; 2., ; 3., ; 4., ; 5., ; 6., ) 6 摘要 :,, U-Pb, SiO %~49.03%, FeO t (11.56%~ 13.09%) MgO(6.83%~11.57%) TiO 2 (1.71%~2.22%), (K 2 O+Na 2 O) 1.61%~2.26%, Na 2 O/K 2 O 1.88~9.25, ((La/Yb) N =6.55~7.52), 112~130 μg/g Sr P, Eu (δeu=0.97~1.03); Nb Ta, Nb 14.28~18.43 μg/g, Nb 814±12 Ma, (~814 Ma) Nb, 关键词 : U-Pb ; ; ; ; 中图分类号 : P595; P597 文献标志码 : A 文章编号 : (2014) , NW-SE,,, ( 1), (, 1993;, 1996;, 2000;, 2002;, 2005;, 1998; Trung et al., 2006; Jian et al., 2009; Wang et al., 2010b; Qi et al., 2012), (Tapponnier et al., 1990; Leloup et al., 1995), (, 1989;, 1991; Leloup et al., 1993, 1995, 2001),, 收稿日期 : ; 改回日期 : 项目资助 : ( : , , ) 第一作者简介 : (1986 ),,, caiyongfeng@gig.ac.cn

2 第 1 期蔡永丰等 : 哀牢山新元古代斜长角闪岩的形成时代地球化学特征及其大地构造意义 169 (, 1993;, 2003;, 2004; Lepvrier et al., 2004;, 2004; Lan et al., 2000;, 2008;, 1987;, 2000; Zhang and Scharer, 1999; Wang et al., 2001; Qi et al., 2012),, U-Pb,, 1 ( Leloup et al., 1995; Wang et al., 2010a; Zhao et al., 2011; Lin et al., 2012 Fig.1 Simplified geotectonic map showing the Ailaoshan zone and surrounding areas 1 区域地质背景与样品描述, NW-SE, 500 km, 20~30 km, ( 1, 2a),,, (, 1981;, 1987;, 1996;, 2008),, ;,,, Rb-Sr Sm-Nd K-Ar, (, 1990;, 1990;, 1996;, 2001), (, 1990;, 1996;, 2000),, 1965, 1973 (, 1990) 3800 km 2,

170 第 38 卷,, NE (, 1990;, 1996) ( 2b), GPS N23 02 38.3, E102 45 33.3,,,, 0.2 m,,,, (1~5 mm), ( 3) (55%) (30%) (8%) (5%), ;,, 0.1~2 mm,,, ;, 0.5~2.5 mm,, ;, 0.1~1 mm, 2 分析方法 2.

3 170 第 38 卷,, NE (, 1990;, 1996) ( 2b), GPS N , E ,,,, 0.2 m,,,, (1~5 mm), ( 3) (55%) (30%) (8%) (5%), ;,, 0.1~2 mm,,, ;, 0.5~2.5 mm,, ;, 0.1~1 mm, 2 分析方法 2.1, (2002) (1996) Rigaku ZSX100e X PE Elan 6000 (ICP-MS) 1%, 5% 2.2 U-Pb U-Pb (10HH-67A) Plésovice TEMORA Qinghu, Fig.2 2 Schematic geological maps of the Ailaoshan zone and distribution of the amphibolites in the Yuanyang area

第 1 期蔡永丰等 : 哀牢山新元古代斜长角闪岩的形成时代地球化学特征及其大地构造意义 171 3 (Am. ; Pl. ; Bt. ; Qtz. ) Fig.

1 U-Pb 10HH-67A U-Pb 1,,, 80~120 µm, ( 4), Th/U (0.10~1.20), 0.2( 1), 10HH-67A 26, 10 814±12 Ma(MSWD=1.01) 206 Pb/ 238 U ( 4),, 4 1150 Ma 1146 Ma 2087 Ma 2740 Ma 207 Pb/ 206 Pb,, (Wang et al.

4 第 1 期蔡永丰等 : 哀牢山新元古代斜长角闪岩的形成时代地球化学特征及其大地构造意义 (Am. ; Pl. ; Bt. ; Qtz. ) Fig.3 Photomicrographs of the representative amphibolites along the Ailaoshan zone, 10HH-67A U-Pb VGPQ-Excel ICP-MS, 213 nm Nd-YAG, Xia et al. (2004) Isoplot3.0 (Ludwig, 2001), 1σ 3 分析结果 3.1 U-Pb 10HH-67A U-Pb 1,,, 80~120 µm, ( 4), Th/U (0.10~1.20), 0.2( 1), 10HH-67A 26, ±12 Ma(MSWD=1.01) 206 Pb/ 238 U ( 4),, Ma 1146 Ma 2087 Ma 2740 Ma 207 Pb/ 206 Pb,, (Wang et al., 2012 ), , SiO %~49.03%,, ( 5a), MgO 6.83%~11.57%, FeO t 11.56%~13.09%, TiO %~2.22%, Al 2 O %~14.47%; (K 2 O+Na 2 O) 1.61%~2.26%, Na 2 O/K 2 O 1.88~9.25; Ni 100~130 μg/g, Cr 103~556 μg/g Mg # 52~68, Mg # (Wilson, 1989), ( REE=112~130 μg/g), (PM) (7.43 μg/g), (N-MORB=39.11 μg/g, E-MORB=49.09 μg/g), (OIB= μg/g) ( 6a), 4 U-Pb Fig.4 U-Pb concordia diagram and CL images for zircons in the amphibolite along the Ailaoshan zone

5 172 第 38 卷表 1 牢山带斜长角闪岩锆石 U-Pb 同位素测试结果 Table 1 Zircon U-Pb dating results for the amphibolite along the Ailaoshan zone (μg/g) (Ma) Th/U 232 Th 238 U 207 Pb/ 206 Pb ±1σ 207 Pb/ 235 U ±1σ 206 Pb/ 238 U ±1σ 207 Pb/ 206 Pb ±1σ 206 Pb/ 238 U ±1σ 10HH-67A, 10HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A HH-67A 表 2 哀牢山带斜长角闪岩的主量元素 (%) 和微量元素 (μg/g) 分析结果 Table 2 Major (%) and trace element (μg/g) compositions of the Neoproterozoic amphibolites along the Ailaoshan zone 10HH-67A 10HH-67D 10HH-67F 10HH-69A 10HH-69E 10HH-67A 10HH-67D 10HH-67F 10HH-69A 10HH-69E SiO Nb TiO Cs Al 2 O Ba Fe 2 O La MgO Ce CaO Pr K 2 O Nd Na 2 O Sm MnO Eu P 2 O Gd LOI Tb Total Dy Mg # Ho Sc Er V Tm Cr Yb Co Lu Ni Hf Ga Ta Rb Pb Sr Th Y U Zr REE

6 第 1 期蔡永丰等 : 哀牢山新元古代斜长角闪岩的形成时代地球化学特征及其大地构造意义 Nb/Y-Zr/TiO 2 (Winchester and Floyd,1977) Nb-Nb/U (Kepezhinaskas et al., 1996) Fig.5 Plots of Nb/Y vs. Zr/TiO 2 and Nb vs. Nb/U for the amphibolites along the Ailaoshan zone 6 ( Sun and McDonough, 1989) Fig.6 Chondrite-normalized REE pattern and primitive mantle-normalized trace element spidergram for the amphibolites along the Ailaoshan zone, (La/Yb) N 6.55~7.52, (Gd/Yb) N 1.90~2.23, Eu (δeu=0.97~1.03) Sr P, Ti Nb (14.3~18.4 μg/g), Nb (<2 μg/g, Martin et al., 2005); Nb/La 0.76~1.14, Nb/U 25.5~38.2, Sajona et al. (1994) Nb, Nb ( 5b) Nb/Ta 14~16, Zr/Hf 34~39, (Nb/Ta=17, Zr/Hf=36; Sun and McDonough, 1989) REE Nb ( 6a, b), OIB E-MORB 4 讨论 4.1, Al Ca Mg (HFSE) Nb Ta Ti Zr Hf Y REE ; (LFSE) K Na Cs Rb Sr Ba K 2 O Na 2 O, Th Rb Sr, Na 2 O/K 2 O K 2 O/Rb,,, ( Wang et al., 2003, 2004;, 2013) Nb/Y 0.71~0.78,, Zr/TiO 2 - Nb/Y (Winchester and Floyd, 1977), ( 5a) LILE REE, Zr Nb P 2 O 5, (Nb/Th) N Nb/U, Zr/Nb, Nb ( Sajona et al., 1994; Zhang et al., 2012; Wang et al., 2013)( 6a, b),

7 174 第 38 卷 OIB, N-MORB(Sun and McDonough, 1989; Martin et al., 2005) Nb (Stern and Hanson, 1991; Shimoda et al., 1998), (Defant et al., 1991; Viruete et al., 2007) (Qi et al., 2012), Nb Woodhead et al. (1993) Gamble et al. (1994) V Ti Zr Nb Nb 2 μg/g(pearce and Peate, 1995; Martin et al., 2005) Nb 2 μg/g(14.3~18.4 μg/g)( 2), Nb,, Nb ( );,,, Nb( ) Ti/V 32.98~41.60, 37.16, MORB Ti/V (Woodhead et al., 1993) Ti, V, Ti/V, MORB Ti; MORB ; Ti/V (Woodhead et al., 1993; Pearce and Parkinson, 1993) Ti Nb, Zr/Nb MORB, Ti/V, MORB ( Woodhead et al., 1993),,,, ( 6), LREE, Nb Ta Zr Hf,, (Gamble et al., 1994; Gribble et al., 1996) Huang et al. (2000) MgO 6%, FeO t, FeO t, 2, MgO 6%, FeO t 11.56%~13.09%, FeO t (12%~17%, Pearce and Peate, 1995), FeO t (11%~14%),,,, MORB /, / / (Pearce and Peate, 1995; Gribble et al., 1996; Wang et al., 2007; Fan et al., 2010; Zhang et al., 2012), MORB, /, MORB (Gribble et al., 1996) (~814 Ma) ( 7), 820~730 Ma (Zhao et al., 2011); (800~1000 Ma) ( 800~830 Ma) (Zhou et al., 2006;, 2007) 4.2 (2012) 748~801 Ma(SHRIMP U-Pb ), Qi et al. (2012) 761±11 Ma(LA-ICP-MS U-Pb ) 842~833 Ma(SHRIMP U-Pb ) (, 2008), ; 770±5 Ma(LA-ICP-MS U-Pb, ε Hf (t) 1.4~2.2)(Lin et al., 2012); 828±6.2 Ma (SHRIMP U-Pb,, 2012),

8 第 1 期蔡永丰等 : 哀牢山新元古代斜长角闪岩的形成时代地球化学特征及其大地构造意义 Ti/10000-V (a, Shervais, 1982) Th/Nb-Ce/Nb (b, Sandeman et al., 2006; Taylor and Martinez, 2003) Fig.7 Plots of Ti/10000 vs. V and Th/Nb vs. Ce/Nb for the amphibolites along the Ailaoshan zone 769±7 Ma (LA-ICP-MS U-Pb, Qi et al., 2012), (Li et al., 1999, 2003; Zhu et al., 2008; Zhou et al., 2002; Munteanu et al., 2010; Zhao and Zhou, 2007; Wang et al., 2008; Zheng et al., 2007; Wu et al., 2006; Zhao and Guo, 2012; Zhao and Cawood, 2012; Dong et al., 2011, 2012; Zhou et al., 2012) (795±11)~(797±10) Ma 824±14 Ma 764±9 Ma 864±8 Ma(SHRIMP U-Pb, Zhou et al., 2002); 759±11 Ma 775±8 Ma(SHRIMP U-Pb, Li et al., 2003); 813±14 Ma 820±13 Ma (SHRIMP U-Pb, Sinclair, 2001); 746±10 Ma(SHRIMP U-Pb, Zhao and Zhou, 2007); 752±11 Ma(SHRIMP U-Pb, Li et al., 2003); (761±14)~ (825±12) Ma(SHRIMP U-Pb, Zhu et al., 2008); ( ) ( ) ( ) (815±24)~(827±14) Ma(SHRIMP U-Pb,, 2007); 839±8 Ma(LA-ICP-MS U-Pb,, 2007), 3 (Li et al., 1999; Zhu et al., 2008; Zhou et al., 2002; Munteanu et al., 2010; Zhao and Zhou, 2007; Zhao et al., 2011; Wang et al., 2008; Zheng et al., 2007; Wu et al., 2006), (Zhou et al., 2002;, 2002;, 2009) Zhou et al. (2002), (, 2009), (, 2002; Zhou et al., 2002; Zhao et al., 2011) 814±12 Ma,, 1000 km ( 1a)(Zhou et al., 2002; Zhao et al., 2011;, 2002), (~814 Ma) 5 结论 U-Pb 814±12 Ma,,, Nb

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10 第 1 期蔡永丰等 : 哀牢山新元古代斜长角闪岩的形成时代地球化学特征及其大地构造意义 177,, ( ). : : ,,,,,, W-Sn A., 37(3): ,,,, , 24(2): Defant M J, Richerson P M, DeBoer J Z, Stewart R H, Maury R C, Bellon H, Jackson T E and Restrepo J F Andesite and dacite genesis via contrasting processes: The geology and geochemistry of E1 Valle volcano, Panama. Contributions to Mineralogy and Petrology, 106: Dong Y P, Liu X M, Santosh M, Chen Q, Zhang X N, Li W, He D F and Zhang G W Neoproterozoic accretionary tectonics along the northwestern margin of the Yangtze Block, China: Constraints from zircon U-Pb geochronology and geochemistry. Precambrian Research, 196: Dong Y P, Liu X M, Santosh M, Zhang X N, Chen Q, Yang C and Yang Z Neoproterozoic subduction tectonics of the northwestern Yangtze Block in South China: Constraints from zircon U-Pb geochronology and geochemistry of mafic intrusions in the Hannan Massif. Precambrian Research, 189: Fan W M, Wang Y J, Zhang A M, Zhang F F and Zhang Y Z Permian arc-back-arc basin development along the Ailaoshan tectonic zone: Geochemical, isotopic and geochronological evidence from the Mojiang volcanic rocks, Southwest China. Lithos, 119(3 4): Gamble J A, Wright I C, Woodhead J D and McCulloch M T Arc and backarc geochemistry in the southern Kermadec arc-ngatoro Basin and off shore Taupo Volcanic Zone, SW Pacific. Geological Society, London, Special Publications, 81: Gribble R F, Stern R J, Bloomer S H, Stüben D, O Hearn T and Newman S MORB mantle and subduction components interact to generate basalts in the southern Mariana Trough back-arc basin. Geochimica et Cosmochimica Acta, 60: Huang Y, Hawkesworth C, Smith I, Calsterena P V and Black P Geochemistry of late Cenozoic basaltic volcanism in Northland and Coromandel, New Zealand: Implications for mantle enrichment processes. Chemical Geology, 164: Jian P, Liu D Y, Kröner A, Zhang Q, Wang Y Z, Sun X M and Zhang W Devonian to Permian plate tectonic cycle of the Paleo-Tethys Orogen in southwest China (I): Geochemistry of ophiolites, arc/back-arc assemblages and within-plate igneous rocks. Lithos, 113: Kepezhinaskas P K, Defant M J and Drummond M S Progressive enrichment of island-arc mantle by meltperidotite interaction from Kamchatka adakites. Geochimica et Cosmochimica Acta, 60: Lan C Y, Chung S L, Shen J S, Lo C H, Wang P L, Hoa T T, Thanh H H and Mertzman S A Geochemical and Sr-Nd isotopic characteristics of granitic rocks from northern Vietnam. Journal of Asian Earth Science, 18: Leloup P H, Arnaud N, Lacassin R, Kienast J R, Harrison T M, Trinh P T, Replumaz A and Tapponnier P New constraints on the structure, thermochronology and timing of the Ailao Shan-Red River shear zone, SE Asia. Journal of Geophysical Research, 106: Leloup P H and Kienast J R High-temperature metamorphism in a major strike-slip shear zone: The Ailao Shan Red River, People s Republic of China. Earth and Planetary Science Letters, 118: Leloup P H, Lacassin R, Tapponnier P, Scharer U, Zhong D L, Liu X H, Zhang L S, Ji S C and Trinh P T The Ailao Shan-Red River shear zone (Yunnan, China): Tertiary transform boundary of Indochina. Tectonophysics, 251: Lepvrier C, Maluski H, Tich V V, Leyreloup A, Thi P T and Vuong N V The Early Triassic Indosinian orogeny in Vietnam (Truong Son Belt and Kontum Massif): Implications for the geodynamic evolution of Indochina. Tectonophysics, 393: Li Z X, Li X H, Kinny P D and Wang J The breakup of Rodinia: Did it start with a mantle plume beneath South China. Earth and Planetary Science Letters, 173: Li Z X, Li X H, Kinny P D, Wang J, Zhang S and Zhou H Geochronology of Neoproterozoic syn-rift magmatism in the Yangtze Craton South China and correlations with other continents: Evidence for a mantle superplume that broke up Rodinia. Precambrian

11 178 第 38 卷 Research, 122: Lin T H, Chung S L, Chiu H Y, Wu F Y, Yeh M W, Searle M P and Iizuka Y Zircon U-Pb and Hf isotope constraints from the Ailao Shan-Red River shear zone on the tectonic and crustal evolution of southwestern China. Chemical Geology, 291: Ludwig K R Users manual for Isoplot/Ex rev Berkeley Geochronology Centre Special Publication, No. 1a: 56. Martin H, Smithies R H, Rapp R, Moyen J F and Champion D An overview of adakite, tonalite-trondhjemite-granodiorite (TTG), and sanukitoid: Relationships and some implications for crustal evolution. Lithos, 79(1 2): Munteanu M, Wilson A, Yao Y, Harris C, Chunnett G and Luo Y The Tongde dioritic pluton (Sichuan, SW China) and its geotectonic setting: Regional implications of a local-scale study. Gondwana Research, 18: Pearce J A and Parkinson I J Trace element models for mantle melting: Application to volcanic arc petrogenesis. The Geological Society, London, Special publications. 76: Pearce J A and Peate D W Tectonic implications of the composition of volcanic arc magmas. Annual Reviews of Earth and Planetary Sciences, 23: Qi X X, Zeng L S, Zhu L H, Hu Z C and Hou K J Zircon U-Pb and Lu-Hf isotopic systematics of the Daping plutonic rocks: Implications for the Neoproterozoic tectonic evolution of the northeastern margin of the Indochina block, Southwest China. Gondwana Research, 21: Sajona F G, Bellon H, Maury R C, Pubellier M, Cotton J and Rangin C Magmatic response to abrupt changes in tectonic setting: Pliocene-Quaternary calc-alkaline lavas and Nb-enriched basalts of Leyte and Mindanao (Philippines). Tectonophysics, 237: Sandeman H A, Hanmer S, Tella S, Armitage A A, Davis W J and Ryan J J Petrogenesis of Neoarchaean volcanic rocks of the MacQuoid supracrustal belt: A back-arc setting for the northwestern Hearne subdomain, western Churchill Province, Canada. Precambrian Research, 144(1 2): Shervais J W Ti-V Plots and the Petrogenesis of Modern and Ophiolitic Lavas. Earth and Planetary Science Letters, 59: Shimoda G, Tatsumi Y, Nohda S, Ishizaka K and Jahn B M Setouchi high-mg andesites revisited: Geochemical evidence for melting of subducting sediment. Earth and Planetary Science Letters, 160: Sinclair J A Petrology, geochemistry, and geochronology of the Yanbian ophiolite suite, South China: Implications for the western extension of the Sibao Orogen. Honours Thesis, The University of Western Australia, Perth: 69. Stern R A and Hanson G N Archean high-mg granodiorite: A derivative of light rare earth elementenriched monzodiorite of Mantle Origin. Journal of Petrology, 32(1): Sun S S and McDonough W F Chemical and isotopic systematics of oceanic basalts: Implications for mantle composition and processes, Magmatism in the Ocean Basins. Geological Society Special Publication, 42: Tapponnier P, Lacassin R, Leloup P H, Scharer U, Zhou D, Wu H, Liu X, Ji S, Zhang L and Zhong J The Ailao Shan/Red River metamorphic belt: Tertiary left-lateral shear between Indochina and South China. Nature, 343: Taylor B and Martinez F Back-arc basin basalt systematics. Earth and Planetary Science Letters, 210: Trung N M, Tsujimori T and Itaya T Honvang serpentinite body of the Song Ma fault zone, Northern Vietnam: A remnant of oceanic lithosphere within the Indochina-South China suture. Gondwana Research, 9(1 2): Viruete J E, Contreras F, Stein G, Urien P, Joubert M, Pérez-Estaun A, Friedman R and Ullrich T Magmatic relationships and ages between adakites, magnesian andesites and Nb-enriched basalt-andesites from Hispaniola: Record of a major change in the Caribbean island arc magma sources. Lithos, 99: Wang J H, Yin A, Harrison T M, Grove M, Zhang Y Q and Xie G H A tectonic model for Cenozoic igneous activities in the eastern Indo-Asian collision zone. Earth and Planetary Science Letters, 188: Wang L J, Yu J H, Griffin W L and O Reilly S Y Early crustal evolution in the western Yangtze Block: Evidence from U-Pb and Lu-Hf isotopes on detrital zircons from sedimentary rocks. Precambrian Research,

12 第 1 期蔡永丰等 : 哀牢山新元古代斜长角闪岩的形成时代地球化学特征及其大地构造意义 : Wang Q, Wyman D A, Li Z X, Bao Z W, Zhao Z H, Wang Y X, Jian P, Yang Y H and Chen L L. 2010a. Petrology, geochronology and geochemistry of ca. 780 Ma A-type granites in South China: Petrogenesis and implications for crustal growth during the breakup of supercontinent Rodinia. Precambrian Research, 178: Wang X L, Zhao G C, Zhou J C, Liu Y S and Hu J Geochronology and Hf isotopes of zircon from volcanic rocks of the Shuangqiaoshan Group South China: Implications for the Neoproterozoic tectonic evolution of the eastern Jiangnan orogen. Gondwana Research, 14: Wang Y J, Fan W M, Guo F, Peng T P and Li C W Geochemistry of Mesozoic mafic rocks around the Chenzhou-Linwu fault in South China: Implication for the lithospheric boundary between the Yangtze and the Cathaysia Blocks. International Geology Review, 45(3): Wang Y J, Fan W M, Zhang Y H, Guo F, Zhang H F and Peng T P Geochemical, 40 Ar/ 39 Ar geochronological and Sr-Nd isotopic constraints on the origin of Paleoproterozoic mafic dikes from the southern Taihang Mountains and implications for the ca Ma event of the North China Craton. Precambrian Research, 135: Wang Y J, Zhang A M, Fan W M, Peng T P, Zhang F F, Zhang Y H and Bi X W. 2010b. Petrogenesis of late Triassic post-collisional basaltic rocks of the Lancangjiang tectonic zone, southwest China, and tectonic implications for the evolution of the eastern Paleotethys: Geochronological and geochemical constraints. Lithos, 120: Wang Y J, Zhang A M, Fan W M, Zhang Y H and Zhang Y Z Origin of paleosubduction-modified mantle for Silurian gabbro in the Cathaysia Block: Geochronological and geochemical evidence. Lithos, 160: Wang Y J, Zhao G C, Fan W M, Peng T P, Sun L H and Xia X P LA-ICP-MS U-Pb zircon geochronology and geochemistry of Paleoproterozoic mafic dykes from western Shandong Province: Implications for back-arc basin magmatism in the Eastern Block, North China Craton. Precambrian Research, 154: Wilson M Igneous petrogenesis, London: Unwin Hyman: Winchester J A and Floyd P A Geochemical discrimination of different magma series and their differenttiation products using immobile elements. Chemical Geology, 20: Woodhead J, Eggins S and Gamble J High field strength and transition element systematics in island arc and back-arc basin basalts: Evidence for multi-phase melt extraction and a depleted mantle wedge. Earth and Planetary Science Letters, 114: Wu R X, Zheng Y F, Wu Y B, Zhao Z F, Zhang S B, Liu X M and Wu F Y Reworking of juvenile crust: Element and isotope evidence from Neoproterozoic granodiorite in South China. Precambrian Research, 146: Xia X P, Sun M, Zhao G C, Li H M and Zhou M F Spot zircon U-Pb isotope analysis by ICP-MS coupled with a frequency quintupled (213 nm) Nd-YAG laser system. Geochemical Journal, 38: Zhang A M, Wang Y J, Fan W M, Zhang Y Z and Yang J Earliest Neoproterozoic (ca. 1.0 Ga) arc-back-arc basin nature along the northern Yunkai Domain of the Cathaysia Block: Geochronological and geochemical evidence from the metabasite. Precambrian Research, 220: Zhang L S and Scharer U Age and origin of magmatsm along the Cenozoic Red River shear belt. Contribuions to Mineralogy and Petrology, 134: Zhao G C and Cawood P A Precambrian geology of China. Precambrian Research, 222: Zhao G C and Guo J H Precambrian geology of China: Preface. Precambrian Research, 222: Zhao J H and Zhou M F Geochemistry of Neoproterozoic mafic intrusions in the Panzhihua district (Sichuan Province, SW China): Implications for subduction related metasomatism in the upper mantle. Precambrian Research, 152: Zhao J H, Zhou M F, Yan D P, Zheng J P and Li J W Reappraisal of the ages of Neoproterozoic strata in South China: No connection with the Grenvillian orogeny. Geology, 39: Zheng Y F, Zhang S B, Zhao Z F, Wu Y B, Li Y B, Li X H, Li Z X and Wu F Y Contrasting zircon Hf and O isotopes in the two episodes of Neoproterozoic granitoids in South China: Implications for growth and reworking of continental crust. Lithos, 96(1 2): Zhou J B, Wilde S A, Liu F L and Han J Zircon U-Pb and Lu-Hf isotope study of the Neoproterozoic Haizhou

13 180 第 38 卷 Group in the Sulu orogen: Provenance and tectonic implications. Lithos, 136: Zhou M F, Kennedy A K, Sun M, Malpas J and Lesher C M Neo-proterozoic arc-related mafic intrusions in the northern margin of South China: Implications for accretion of Rodinia. Journal of Geology, 110: Zhou M F, Ma Y X, Yan D P, Xia X P, Zhao J H and Sun M The Yanbian terrane (Southern Sichuan Province, SW China): A neoproterozoic are assemblage in the western margin of the Yangtze block. Precambrian Research, 144(1 2): Zhu W G, Zhong H, Li X H, Deng H L, He D F, Wu K W and Bai Z J SHRIMP zircon U-Pb geochronology, elemental, and Nd isotopic geochemistry of the Neoproterozoic mafic dykes in the Yanbian area, SW China. Precambrian Research, 164(1 2): Geochronological and Geochemical Characteristics of the Neoproterozoic Amphibolite from Ailaoshan Zone, Western Yunnan and its Tectonic Implications CAI Yongfeng 1, 2, 3, WANG Yuejun 2, 4, LIU Huichuan 1, 3, MA Liyan 5, XING Xiaowan 1, 3 and LIU Lei 6 (1. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou , Guangdong, China; 2. Department of Earth Sciences, Sun Yat-Sen University, Guangzhou , Guangdong, China; 3. University of Chinese Academy of Sciences, Beijing , China; 4. Guangdong Provincial Key Laboratory of Mineral Resources & Geological Processes, Guangzhou , Guangdong, China; 5. College of Geosciences, Guilin University of Technology, Guilin , Guangxi, China; 6. Geological Exploration Center of China Building Material Industry, Ningxia General Team, Yinchuan , Ningxia, China) Abstract: Some small-sized outcrops of metabasic rocks (e.g., amphibolite, metagabbro and metadiabase) occur mainly as lens, pods and fragments in the Ailaoshan Complex along the Ailaoshan zone, which were previously mapped as Proterozoic basement. These rocks provide possibility for better understanding the tectonic setting of the SW margin of the Yangtze Block in South China, however, their formation time, petrogenesis and tectonic implications are poorly documented so far. The petrological, geochemical and zircon U-Pb geochronological data for the plagioclase amphibolites in the Ailaoshan Complex are reported in this paper. Geochemical analyses show that the amphibolites have SiO 2 contents ranging from 46.85% to 49.03% and with relatively high FeO t (11.56%~13.09%), MgO (6.83%~ 11.57%) and TiO 2 contents (1.71%~2.22%), K 2 O+Na 2 O vary from 1.61% to 2.26% with Na 2 O/K 2 O ratios of 1.88~9.25. The rocks are characterized by enriched LREE ((La/Yb) N =6.55~7.52) and Nb (Nb=14.28~18.43 μg/g). On primitive mantle-normalized trace element diagrams, the rocks show no obvious Nb and Ta anomalies and significant Sr-P depletion, displaying geochemical characteristics similar to those of the Yunkai (South China) back-arc basin basalt. Zircon U-Pb dating of the amphibolite vields a mean age of 814±12 Ma. In conjunction with other geological observations, it is proposed that there was an Early Neoproterozoic (~814 Ma) arc-back-arc setting along the Ailaoshan zone in the SW margin of the Yangtze Block. Keywords: Ailaoshan zone; Early Neoproterozoic; amphibolite; U-Pb geochronology; back-arc basin

NE NW NE NW 6 NE NW NE ~ 85 1 ~ 4 NW NE 702 NE NW 1 NE30 ~ 50 SE 50 ~ 60 1a I II I 73 m 3. 5 m g /t II 62 m 60 ~ 100

NE NW NE NW 6 NE NW NE ~ 85 1 ~ 4 NW NE 702 NE NW 1 NE30 ~ 50 SE 50 ~ 60 1a I II I 73 m 3. 5 m g /t II 62 m 60 ~ 100 34 2 2015 6 GLOBAL GEOLOGY Vol. 34 No. 2 Jun. 2015 1004 5589 2015 02 0385 11 1 1 2 2 1 1 1. 130061 2. 702 157021 σ < 3. 3 Rb Ba K Pb LILE Nb Ta P Ti HFSE LREE HREE Nb /Ta 14. 7 Zr /Hf 26. 23 ~ 38. 37 P618.