西秦岭天水阴崖沟早古生代草滩沟群火山岩地球化学特征及其地质意义  

Geochemical characteristics of the Yinaigou Early Paleozoic Caotangou Group volcanic rocks in Tianshui of West Qinling Mountains and their geological significance

作　　者：胥晓春 裴先治[1,2] 刘成军[1] 李瑞保[1,2] 李佐臣[1,2] 魏博[1] 王元元[1] 刘图杰 任厚州 陈伟男[1] 陈有炘[1] 

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]西部矿产资源与地质工程教育部重点实验室,陕西西安710054

出　　处：《中国地质》2014年第3期851-865,共15页Geology in China

基　　金：国家自然科学基金项目(41172186;40972136);中央高校基本科研业务费专项资金项目(CHD2011TD020;2013G1271091;2013G1271092);教育部高等学校博士学科点专项科研基金项目(20110205110004);中国地质调查局地质调查项目(200013000154)联合资助

摘　　要：天水阴崖沟草滩沟群中发育有变质火山岩,其岩石类型主要为变玄武岩、变安山岩、变英安岩和变流纹岩;研究区变火山岩主体属于拉斑系列,其原始岩浆来源于富集地幔;变火山岩的微量元素特征表现为富集大离子亲石元素Cs、Ba、Th和U,而相对亏损高场强元素Nb、Ta、P、Ti和Y;微量元素构造环境判别显示其形成于俯冲消减带之上的岛弧环境;结合已有年代学资料,显示天水—武山洋在晚奥陶世已经存在并开始俯冲,形成阴崖沟草滩沟群岛弧火山岩;同时从岩石组成、形成时代及地球化学特征来看,阴崖沟草滩沟群火山岩与东秦岭丹凤岩群火山岩相似,这为确定天水一武山构造带是早古生代商丹古缝合带的西延部分提供了证据。There are volcanic rocks of Caotangou Group in Yinaigou,Tianshui.The main rock types of these metamorphic volcanic rocks are metabasalt,metaandesite,metadacite and metarhyolite.These metamorphic volcanic rocks of the study area basically belong to tholeiitic basalt,whose primary magma was derived from an enriched mantle source.The metamorphic volcanic rocks of Caotangou Group are characterized by high content of LILE （Cs,Ba,Th and U） and low content of HFSE （Nb,Ta,P,Ti and Y）.The tectonic environment discrimination by trace elements reveals that metamorphic volcanic rocks were formed in an island arc setting above the subduction zone.Combined with the chronological data,the authors hold that the Tianshui-Wushan oceanic basin already existed in Early Paleozoic and began subducting then,leading to the formation of Caotangou Group island arc in Yinaigou,which was similar to things of Danfeng Group in west Qinling from the viewpoints of rock assemblage,forming time and geochemical characteristics.The results obtained by the authors provide evidence for the study of Tianshui-Wushan tectonic zone which served as the west extensional part of the Shangdan paleo-suture zone in Early Paleozoic.

关 键 词：草滩沟群 早古生代 岛弧环境 地球化学 天水地区 西秦岭 

分 类 号：P588.14[天文地球—岩石学]