西藏冈底斯带查隆花岗岩地球化学特征、锆石U-Pb年龄及其成矿意义
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摘要
查隆花岗岩位于中冈底斯带火山岩浆弧,主要岩性为黑云花岗闪长岩、花岗闪长岩,其中中细粒花岗闪长岩锆石~(206)Pb/~(238)U年龄为89.88±0.55Ma(95%置信度,n=24,MSWD=0.43),中粒黑云花岗闪长岩锆石~(206)Pb/~(238)U年龄为86.6±1.0Ma(95%置信度,n=30,MSWD=0.64)。岩石化学特征表明,查隆花岗岩为高钾钙碱性的偏铝质I型花岗岩,稀土元素配分曲线呈右倾型,岩浆经过一定程度的分异;微量元素Ti、Nb、P相对亏损。该岩体为雅鲁藏布江洋壳单向俯冲作用的结果,形成于火山弧环境,为具有壳幔混合特征的中酸性岩浆的产物。与该岩体密切相关的查隆磁铁矿成因类型为矽卡岩型-热液叠加改造型,与区域上发现的矿床有极其相似的成矿地质背景。
The Chalong granite is located in volcanic magma arc of the Mid-Gangdise belt. The granite petrologically consists of biotite granodiorite and granodiorite; the zircon U-Pb age of fine-grained granodiorite is 89.88 ± 0.55 Ma(95% conf., n=24,MSWD=0.43) and that of medium-grained biotite granodiorite is 86.6 ± 1.0 Ma(95% conf., n=30, MSWD=0.64). Their petrochemical characteristics indicate that they are high-K calc alkaline peraluminous "I" type granite. The REE distribution curves are right-inclines, and the magma experienced differentiation to some extent. The trace elements Ti, Nb and P are relatively deficient. The intrusive rock resulted from the unidirectional subduction of the Yarlung Zangbo River crust, was formed in the volcanic arc environment, and was the product of intermediate acid magma with crust mantle mixing Characteristics. The genetic type of Chalong magnetite mineral deposit closely related to the intrusive rock is skarn hydrothermal superimposition type. Chalong magnetite mineral deposit has a similar metallogenic geological background to the discovered deposits in the area.
The Chalong granite is located in volcanic magma arc of the Mid-Gangdise belt. The granite petrologically consists of biotite granodiorite and granodiorite; the zircon U-Pb age of fine-grained granodiorite is 89.88 ± 0.55 Ma(95% conf., n=24,MSWD=0.43) and that of medium-grained biotite granodiorite is 86.6 ± 1.0 Ma(95% conf., n=30, MSWD=0.64). Their petrochemical characteristics indicate that they are high-K calc alkaline peraluminous "I" type granite. The REE distribution curves are right-inclines, and the magma experienced differentiation to some extent. The trace elements Ti, Nb and P are relatively deficient. The intrusive rock resulted from the unidirectional subduction of the Yarlung Zangbo River crust, was formed in the volcanic arc environment, and was the product of intermediate acid magma with crust mantle mixing Characteristics. The genetic type of Chalong magnetite mineral deposit closely related to the intrusive rock is skarn hydrothermal superimposition type. Chalong magnetite mineral deposit has a similar metallogenic geological background to the discovered deposits in the area.
引文
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[16]李华亮,杨绍,李德威,等.冈底斯西北缘晚白垩世石英二长岩的年代学、地球化学、构造环境及成矿意义[J].大地构造与成矿学,2014,38(3):694-705.
[17]王力圆,郑有业,高顺宝,等.西藏吉瓦地区中冈底斯带岗在岩体晚白垩世的岩浆作用及构造意义[J].中南大学学报,2014,45(8):2740-2751.
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[19]李永军,赵仁夫,李注苍,等.岩浆混合花岗岩微量元素成因图解尝试-以西秦岭温泉岩体为例[J].长安大学学报,2003,25(3):7-15.
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[27]Panino Douce Alberto E.What do experiments tell us about therelative contributions of crust and mantle to the origin of graniticmagmas.Understanding Granites:Integrating New and ClassicalTechniques[J].Geological Society,London,Special Publications,1999,168:55-75.
[28]莫宣学.青藏高原地质研究的回顾与展望[J].中国地质,2010,37(4):841-853.
[29]莫宣学.岩浆作用与青藏高原演化[J].高校地质学报,2011,17(3):351-367.
[30]朱弟成,潘桂棠,王立全,等.西藏冈底斯带中生代岩浆岩的时空分布和相关问题的讨论[J].地质通报,2008,27(9):1535-1536.
(1)秦臻,杨克俭,于恒彬,等.西藏1∶5万许如错东加亚寺幅等4幅区域地质矿产调查报告.2016.
[2]朱弟成,潘桂棠,莫宣学,等.冈底斯中北部晚侏罗世-早白垩世地球动力学环境:火山岩约束[J].岩石学报,2006,22(3):534-546.
[3]莫宣学,董国臣,赵志丹,等.西藏冈底斯带花岗岩的时空分布特征及地壳生长演化信息[J].高校地质学报,2005,11(3):281-290.
[4]王成善,刘志飞,李祥辉,等.西藏日喀则弧前盆地与雅鲁藏布江缝合带[M].北京:地质出版社,1999:1-237.
[5]Harris.N B W,Inger S,Xu R.Chalong Plutonism in central Tibet:an example of post-collision magmatism[J].Journal of Volcanology and Geothermal Reserch,1990,44:21-32.
[6]Anderson T.Correction of common Pb in U-Pb analyses that do not report 204Pb[J].Chemcal Geology,2002,192(1/2):59-79.
[7]Ludwig K R.Isoplot/Exversion 2.49.A Geochronological Toolkit for Microsoft Excel[C]//Berkeley:Berkeley Geochronology Center Special Publication.2003,1:1-56.
[8]Middlemost E.Naming materials in the magma/igneous rock system[J].Annual Review of Earth&Planeary Sciences,1994,37(3/4):215-224.
[9]Rickwood P C.Boundary lines within petrologic diagrams which use oxides for major and minor element[J].Lithos,1989,22:246-263.
[10]Maniar P D,Piccoli P M.Tectionic discrimination in of granitoids[J].Geological Society,Am.Bull.,1989,1:635-643.
[11]Sun S S,Macdonough W F.Chemical and isotopic systematics of ocean basalts:Implations for mantle composition and processes[C]//Saunders A D,Norry M J.Magmatism in the Ocean Basins.Geological Society,London,Special Publications,1989,42(1):313-345.
[12]刘建兵,那晓红,张忠,等.冈底斯带门巴区晚白垩世花岗岩年代学、地球化学及构造背景[J].世界地质,2012,31(4):638-647.
[13]管琪,朱弟成,赵志丹,等.西藏南部冈底斯带东段晚白垩世埃达克岩:新特提斯洋脊俯冲的产物?[J].岩石学报,2010,26(7):2165-2179.
[14]陈炜,马昌前,边秋绢,等.西藏冈底斯带中段以东得明顶地区晚白垩世花岗岩类锆石U-Pb年代学和地球化学证据[J].矿物岩石,2010,30(1):83-92.
[15]苟正彬,汪雄武,张强,等.西藏冈底斯谢通门-桑日地区查隆花岗岩类形成的大地构造背景及找矿意义[J].矿床地质,2010,29:1085-1086.
[16]李华亮,杨绍,李德威,等.冈底斯西北缘晚白垩世石英二长岩的年代学、地球化学、构造环境及成矿意义[J].大地构造与成矿学,2014,38(3):694-705.
[17]王力圆,郑有业,高顺宝,等.西藏吉瓦地区中冈底斯带岗在岩体晚白垩世的岩浆作用及构造意义[J].中南大学学报,2014,45(8):2740-2751.
[18]侯云岭,黄柏鑫,贾小川,等.西藏扎布耶茶卡北部早白垩世侵入岩锆石U-Pb年龄、地球化学特征及其地质意义[J].地质通报,2017,36(10):1783-1799.
[19]李永军,赵仁夫,李注苍,等.岩浆混合花岗岩微量元素成因图解尝试-以西秦岭温泉岩体为例[J].长安大学学报,2003,25(3):7-15.
[20]赵振华.微量元素地球化学原理[M].北京:科学出版社,1997:1-495.
[21]Barth M G,Mc Donough W F,Rudnick R L.Tracking the budget of Nb and Ta in the continental crust[J].Chemical Geology,2000,165(3):197-213.
[22]Pf?nder J A,Münker C,Stracke A,et al.Nb/Ta and Zr/Hf in ocean island basalts-implications for crust-mantle differentiation and the fate of Niobium[J].Earth and Planetary Science Letters,2007,254(1):158-172.
[23]Wolf M B,London D.Apatite dissolution into peraluminous haplogranitic melts:an experimental study of solubilities and mechanisms[J].Geochimica et Cosmochimica Acta,1994,58(19):4127-4145.
[24]Hofmann A W.Nb in Hawaiian magmas:constraints on source composition and evolution[J].Chemical Geology,1986,57(1):17-30.
[25]Rutter J M,Wyllie P.Metlting of vapour-absent tonalite at10 kbar to simulate dehydration-melting in the deep crust[J].Nature,1988,331:159-160.
[26]Rapp R P,Watson E B.Dehydration melting of metabasaltmantle recycling[J].Journal of Petrology,1995,36:891-931.
[27]Panino Douce Alberto E.What do experiments tell us about therelative contributions of crust and mantle to the origin of graniticmagmas.Understanding Granites:Integrating New and ClassicalTechniques[J].Geological Society,London,Special Publications,1999,168:55-75.
[28]莫宣学.青藏高原地质研究的回顾与展望[J].中国地质,2010,37(4):841-853.
[29]莫宣学.岩浆作用与青藏高原演化[J].高校地质学报,2011,17(3):351-367.
[30]朱弟成,潘桂棠,王立全,等.西藏冈底斯带中生代岩浆岩的时空分布和相关问题的讨论[J].地质通报,2008,27(9):1535-1536.
(1)秦臻,杨克俭,于恒彬,等.西藏1∶5万许如错东加亚寺幅等4幅区域地质矿产调查报告.2016.