西藏冈底斯带鸡公村地区辉长岩年代学与地球化学:对新特提斯洋演化的启示  

GEOCHRONOLOGY AND GEOCHEMISTRY STUDY OF GABBROFROM JIGONGCUN AREA,GANGDISE BELT,TIBET:IMPLICATIONS FOR THE EVOLUTION OF THE NEO-TETHYAN OCEAN

作　　者：白云 张志[2] 李光明[2] 杨毅 杨成业[3] 连廷仁 BAI Yun;ZHANG Zhi;LI Guangming;YANG Yi;YANG Chengye;LIAN Tingren(Sichuan Water Conservancy College,Chengdu,Sichuan 611231,China;Chengdu Center of China Geological Survey,Chengdu,Sichuan 610081,China;College of Engineering,Xizang University,Lhasa Tibest 850000,China;Litai Mining Co.,Ltd.of Tibet,Lhasa Tibest 850012,China)

机构地区：[1]四川水利职业技术学院,四川成都611231 [2]中国地质调查局成都地质调查中心,四川成都610081 [3]西藏大学工学院,西藏拉萨850000 [4]西藏利泰矿业有限公司,西藏拉萨850012

出　　处：《矿物岩石》2023年第1期15-27,共13页Mineralogy and Petrology

基　　金：西藏科技计划重点研发项目(编号:XZ202201ZY0020G);科技部国家重点研发计划(项目编号:2021YFC2901903);国家自然科学基金(项目批准号:41702080);四川水利职业技术学院2022年度校级科研项目(编号:KY2022-02)。

摘　　要：西藏冈底斯成矿带鸡公村地区发育有强烈的基性岩浆活动,但其成因尚未得到系统约束。LA-ICP-MS锆石U-Pb年代学结果显示,鸡公村地区辉长岩成岩年龄为48.2±0.3 Ma,形成于始新世,与区内发育的Mo-Re成矿作用(22 Ma)没有成因联系。岩石地球化学分析结果显示,这些辉长岩具有高w(Al_(2)O_(3))(17.78%~18.63%)、w(K_(2)O)(0.90%~1.76%),低TiO2特征,且相对富集LILEs(Ba,Sr,Rb等),相对亏损HFSEs(Zr,Ta,Nb等),显示弧岩浆特征。锆石εHf(t)值在10.0~13.4之间,全岩(^(87)Sr/^(86)Sr)ⅰ同位素值在0.7044~0.7048之间,εNd(t)值在1.6~2.2之间。这些岩石地球化学与同位素特征指示鸡公村地区辉长岩起源于被俯冲流体交代的岩石圈地幔。结合区域构造演化,本次研究认为鸡公村地区辉长岩形成于新特提斯洋壳板片断离背景,上涌的软流圈地幔致使前期形成的被俯冲流体交代的岩石圈地幔发生部分熔融,进而形成鸡公村地区广泛发育的基性岩浆活动。The basic magmatic activity in Jigongcun area of Gangdisi metallogenic belt,Tibet,is studied by means of geochemistry and geochronology to constrain and reveal the petrogenesis and formation age of these basic magmatic rocks.LA-ICP-MS zircon U-Pb dating data show that the gabbro in Jigongcun area was formed in the Eocene with an age of 48.2±0.3 Ma,which has no correlation with the formation of Mo-Re mineralization(22 Ma).Geochemical analysis results indicate that these gabbro rocks have high content of w(Al_(2)O_(3))(17.78%to 18.63%),w(K_(2)O)(0.90% to 1.76%),low content of TiO2,relatively enriched LILEs(Ba,Sr,Rb,etc.),and relatively depleted HFSEs(Zr,Ta,Nb,etc.),which are in-dicative of arc magmatic characteristics.In addition,the εHf(t)values of zircon are in the range of 10.O to 13.4,the whole rock^(87)Sr/^(86)Sr,is in the range of 0.7044 to 0.7048,and the εNd(t)values are in the range of 1.6 to 2.2.Combined with regional tectonic evolution,it is considered that the gabbro rocks in Jigongcun area were formed due to the detachment of the Neo-Tethys oceanic crust plate,and the upflow-ing asthenosphere mantle caused partial melting of the lithospheric mantle metasomatized by subducted fluid in the early stage,thus forming the widely developed basic magmatic rocks in Jigongcun area.

关 键 词：年代学 地球化学 新特提斯洋 冈底斯成矿带 鸡公村 

分 类 号：P581[天文地球—岩石学] P585[天文地球—地质学]