西藏尼雄岩体岩石地球化学特征及其成因探讨  

Geochemistry and genesis of the Nyixung rock body in northern Tibet

作　　者：吴旭铃[1] 陈振华 

机构地区：[1]中国地质大学资源学院,湖北武汉430074 [2]江西省地质调查院,江西南昌330201

出　　处：《中国地质》2005年第1期122-127,共6页Geology in China

基　　金：中国地质调查局1:25万<措麦区>幅区域地质调查及<西藏措勤-昂仁地区铁铜矿评价>部分成果。

摘　　要：尼雄岩体分布于西藏自治区措勤县木质顶、尼雄、沙松、日阿一带,出露面积180.14km2,由4个深成岩体组成,平面形态呈不规则椭圆形、圆形串珠状分布,岩石类型有苏长岩、花岗闪长岩、二长花岗岩、花岗岩。根据野外地质调查资料和室内的岩石学、岩石化学等特征的综合研究成果,发现该岩体各单元之间呈脉动式侵入接触,接触界线清晰,且含有较多暗色闪长质微粒包体;稀土总量较低,K、Rb、Ba、Th元素相对富集,Cr、Ti、Nb、Sr、Zr、P元素相对亏损。研究显示尼雄岩体形成于活动陆缘火山弧,构造环境,与雅鲁藏布江大洋板块向北俯冲消减作用有关,为大陆弧花岗岩。The Nyixung rock body is distributed along the Muzhidin-Nyixung-Shasong-Ria zone in Coqên County, Tibet, covering an area of 180.14 km2. It consists of four plutons, which are irregularly elliptical and circular in plan view and occur as a string of beads. The rock types are norite, granodiorite, monzogranite and granite. On the basis of the information obtained through field geological survey and indoor integrated petrological and petrochemical studies, it has been found that there is a clear and sharp pulsatory intrusive contact between various rock units of the rock body and a number of dark dioritic microinclusions are present. The rocks are characterized by a relatively low total REE content, relative enrichment in K, Rb, Ba and Th and relative depletion in Cr, Ti, Nb, Sr and P. Study suggests that the Nyixung rock body formed in an active continental-margin volcanic arc tectonic environment, which is related to northward subduction of the Yarlung Zangbo oceanic plate. So the rock body is believed to be continental arc granite.

关 键 词：岩石地球化学 成因探讨 花岗岩 俯冲 大洋板块 深成岩体 包体 亏损 特征 总量 

分 类 号：P59[天文地球—地球化学]