南秦岭西乡群孙家河组火山岩形成构造背景及其大地构造意义的讨论  

TECTONIC SETTING AND IMPLICATION OF THE SUNJIAHE VOLCANIC ROCKS,XIXIANG GROUP, IN SOUTH QINLING

作　　者：赖绍聪[1] 杨瑞瑛[2] 张国伟[1] 

机构地区：[1]西北大学地质系,西安710069 [2]中国科学院高能物理研究所,北京100080

出　　处：《地质科学》2001年第3期295-303,共9页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金秦岭重点项目(编号 :4 9732 0 80 );中国科学院LNAT核分析技术联合开放实验室(编号 :97B0 0 6);陕西省教委专项科研

摘　　要：西乡群孙家河组火山岩形成于晚泥盆 早石炭世 ,组内火山熔岩主要为一套亚碱性玄武岩和安山岩 ,具有高Ba及显著的Nb、Ta亏损 ,其Th Yb、Ta Yb、Th Ta、Nb La和Ti Zr、Ti Y等不活动痕量元素组合指示其形成于大陆边缘弧 (活动陆缘 )环境。这套火山岩在区域上可能与勉略带相联 ,指示南秦岭泥盆The Sunjiahe volcanic rocks of Xixiang group are composed of subalkaline basalt and andesite. Both of them exhibit the typical geochemical features of high content of Ba, remarkable depletion of Nb and Ta. In addition, the Th/Yb Ta/Yb and Ti/Zr Ti/Y ratios of the basalt indicate that the volcanic rocks in the studied area occurred in a typical tectonic setting of an island arc. It is proposed that the occurrence of the volcanic rocks might be related to subduction of an ancient oceanic crust represented by the Mianlue suture zone and developed during Carbono\|Devonian in south Qinling.

关 键 词：孙家河组 火山岩 构造环境 西乡群 大地构造 地球化学 微量元素 

分 类 号：P588.14[天文地球—岩石学] P595[天文地球—地质学]