冈底斯地区林子宗群火山岩岩石地球化学特征及地球动力学意义  

Geochemical characteristics and geodynamic significance of the Linzizong Group volcanic rocks in the Gangdise area

作　　者：贾建称[1] 温长顺[1] 王根厚[1] 高春光[1] 杨国东[1] 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083

出　　处：《中国地质》2005年第3期396-404,共9页Geology in China

基　　金：中国地质调查局地质大调查项目(20001300009181)和(200313000001)联合资助。

摘　　要：错卧莫—惩香错火山-沉积盆地位于西藏冈底斯陆块中部南缘。盆地内火山-沉积地层称古新世—渐新世林子宗群,岩石地球化学数据分析表明:这套火山岩系属钙碱性系列,轻稀土富集,不同程度表现出负Eu、负Ce、负Nb异常。微量元素K、Rb、Th、Ce富集,Sr、Ba,尤其是Nb、P、Ti亏损。初步认为这套火山-沉积岩系形成于俯冲造弧的构造背景中,是来自于俯冲带的地幔源区基性分异岩浆与陆壳重熔的酸性岩浆在不同的时间段内,按不同的比例混合形成的。同时,俯冲板块上深海沉积物与基性岩浆混合作用也是不容忽视的因素。在综合分析基础上,笔者认为印度板块与欧亚板块的碰撞启动时间在45Ma以后。The Cuowomo-Chengxiangcuo volcano-sedimentary basin is located on the south-central edge of the Gangdise block, Tibet. Volcano-sedimentary rocks in this basin are caUed the Linzizong Group, which is Paleocene-Eocene in age. Geochemical analysis indicates that the Linzizong volcanic rocks belong to a calcalkaline series, exhibiting enrichment in LREE, different degrees of negative Eu, Ce and Nb anomalies and enrichment in the trace elements K, Rb, Th and Ce and depletion in the trace elements Sr and Ba, especially in Nb, P and Ti. Therefore, the authors tentatively suggest that the Linzizong volcanic rocks formed in a tectonic environment of subduction and arc making and resulted from mixing of basic differentiated magma and crustal anatectic acid magma in different proportions and in different time intervals. In addition, mixing between abyssal sediments on the subducted plate and basic magma is also a factor that can not be negligible. On the basis of an integrated analysis, the authors suggest that the collision between the India plate and Eurasian plate was initiated after 45 Ma。

关 键 词：冈底斯地区 林子宗群火山岩 岩石地球化学 壳幔混合作用 印度-亚洲板块俯冲 

分 类 号：P588.14[天文地球—岩石学]