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2016年3月，第22卷，第1期，081-091页 March 2016, Vol.22, No.1, pp. 081091
D0I: 10.16108/j.issn10067493.2015194
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高校地质学报
Geological Jourmal of China Universities
西藏冈底斯中段桑桑花岗质岩体锆石U-Pb年龄与 Hf同位素组成及其对岩石成因和构造演化的制约
王睿强，邱检生“，喻思斌，赵姣龙
内生金属矿床成矿机制研究国家重点实验室，南京大学地球科学与工程学院，南京210023
摘要：以西裁冈底斯中段西侧桑桑花岗质岩体为对象，进行了系统的年代学、元素地球化学和结石H同位素组成研究，据此闸明了岩体成因，并探讨了其构造意义。错石LA-ICP-MSU-Pb定年表明，桑桑花岗质岩体的成岩年龄为49-54Ma。化
P:0<0.20%）属铸碱性I型花岗岩类。岩体富Cs、Rb、Ba、
学组成上，岩体具有亚碱、准铝、贫磷的特征（A/NKC<1.10， Th、U、K、Pb和轻土，贫Nb、Ta、P与Ti，
，表现出弧岩浆岩的地球化学特征。岩体的错石s()值变化较大，散布于正值
与负值之间（=-4.24~+5.49），指示其形成存在不同来源物质的贡献。综合分析表明，桑桑花岗质若体起源于初生地壳的部分熔融，但在成若过程中有古老地壳组分的参与。结合区域地质背景，笔者认为这一古老地壳组分最可能来自印亚硅撞过
程中冲下插的印度地壳，由此说明印度-欧亚大陆硅撞的起始时间应早于54Ma。关键词：花岗质岩体；Hf同位素组成；岩石成因；印度-欧亚大陆碰撞；日喀则桑桑中图分类号：P588.12
文献标识码：A
文章编号：10067493（2016）01008111
ZirconU-PbAges andHf Isotopic Compositions of theSangsang GraniticPlutonintheMiddleSegmentof theGangdeseBelt:
ConstraintsonthePetrogenesisandTectonicEvolution
WANG Ruiqiang, QIU Jiansheng", YU Sibin, ZHAO Jiaolong
State Key Laboratory for Mineral Deposits Research,
School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
Abstract: To better understand the petrogenesis and tectonie implications of the Sangsang granitic pluton located in the westerm part of the middle segment of the Gangdese belt, we have conducted an integrated study of the geochronology, elemental geochemistry, and zircon Hf isotopic compositions of the granitic pluton. Zirecon LAICP-MS UPb dating for the Sangsang granitic rocks yields ages of 4954 Ma, indicating that they were emplaced during Eocene. Chemically, all the rncks are subalkaline, metaluminous and poor in phosphorus (A/NKC<1.10, P,O,<0.20%), thus can be grouped into cale-alkaline I-type granites. They are enriched in Cs, Rb, Ba, Th, U, K, Pb and LREE, and depleted in Nb, Ta, P, Ti, showing the geochemical characteristics of arc: magmatic rocks. The granitic rocks have variable xircon (r) values which are scattered from positive to negative values (=4.24~ + 5.49), implying that different source components have contributed to magma genesis. The integrated petrologic, elemental and isotopic compositions suggest that the Sangsang granitic rocks were mainly originated by partial melting of juvenile crust, with some ancient crustal materials involved in their
收稿日期：20150926；修四日期：20151007
基金项目：中国地质调查局工作项目（12120114057401)；国家自然科学基金项目（41572041）联合资助作者简介：王睿强，男，博土酬究生，若石学专业；E-mail:vickwrq2008@163.com
*通讯作者：邱检生，男，教授，主要从事火或若若石学方面的研究；E-mail:jiu@nju.anluen
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