西藏刘琼村北始新世石英闪长岩的成因及其地质意义  

Genesis and geological significance of Eocene quartz diorite in north of Liuqiong village,Tibet

作　　者：邓科 袁仁华 董玉杰 张泽国 陈守关 辛堂 DENG Ke;YUAN Renhua;DONG Yujie;ZHANG Zeguo;CHEN Shouguan;XIN Tang(The 5th Geological Brigade of Tibet,Golmud 816099,Qinghai,China)

机构地区：[1]西藏自治区地质矿产勘查开发局第五地质大队,青海格尔木816099

出　　处：《地质找矿论丛》2022年第4期347-356,共10页Contributions to Geology and Mineral Resources Research

基　　金：中国地质调查局“冈底斯—喜马拉雅铜矿资源基地调查”项目(编号:DD20160015-09)资助。

摘　　要：本文以西藏刘琼村北始新世石英闪长岩为研究对象,通过岩石学、岩石地球化学方法及锆石同位素年代测定,分析了岩浆起源、岩石成因及形成的构造环境。LA-ICP-MS锆石U-Pb定年结果显示,岩体形成于始新世(53.74 Ma~55.94 Ma)。岩石属准铝质钙碱性系列,富集大离子亲石元素(K、U、Rb、Ba)和轻稀土(LREE),亏损高场强元素(Nb、Ta、Ti、Zr)和重稀土(HREE),无明显Eu异常。锆石ε_(Hf)(t)值为+10~+14.9,单阶式Hf模式年龄(t_(DM1))集中在192.9~341.8之间,表明岩浆源区来自于亏损地幔中新增生出来的年轻地壳,具S型花岗岩地球化学特征,推断其形成于同碰撞构造环境,表明始新世时期冈底斯南缘处于新特提斯洋与拉萨地块同碰撞构造环境背景之下。An Eocene quartz dioxide body occurs in north of Liuqiong village.It is studied in respects of petrology,petro geochemistry and isotropic chronology to discuss source of its magma,genesis and tectonic setting.The U-Pb dating of zircon LA-ICP-MS is 53.74 Ma-55.94 Ma corresponding to Eocene.It belongs to quasi-aluminous calc-alkaline series enriched in large-ion lithophile elements(K,U,Rb,Ba)and LREE,depleted in high field strong elements(Nb,Ta,Ti,Zr)and HREE without EU depletion.ε_(Hf)(t)value of zircon is+10-+14.9,and the single-stage Hf model age(t_(DM1)) is concentrated between 192.9-341.8 indicating that the magma source region is the newly accredited young crust in the depleted mantle and the diorite is characteristic of S type granite.It is infered that the diorite is formed under the syn-collisional environment and in Eocene the South margin of Gangdise continent is under collisional setting of the new Tethys and Lhasa block.

关 键 词：石英闪长岩 锆石U-PB定年 LU-HF同位素 亏损地幔 同碰撞构造 西藏 

分 类 号：P597.1[天文地球—地球化学]