西秦岭天水地区关子镇中基性岩浆杂岩体锆石U-Pb年龄及其地质意义  

Zircons U-Pb ages of the Guanzizhen intermediate-basic igneous complex in Tianshui area, West Qinling, and their geological significance.

作　　者：裴先治[1] 李勇[1] 陆松年[2] 陈志宏[2] 丁仨平 胡波[1] 李佐臣[1] 刘会彬[1] 

机构地区：[1]长安大学地球科学与国土资源学院 [2]中国地质调查局天津地质矿产研究所 [3]甘肃省地质调查院,甘肃兰州730050

出　　处：《地质通报》2005年第1期23-29,共7页Geological Bulletin of China

基　　金：国家自然科学基金重点项目(40234041);教育部科学技术研究重点项目(104175);中国地质调查局地质调查项目(200013000154)资助。

摘　　要：西秦岭天水关子镇地区新确定的流水沟变质中基性岩浆杂岩体主要由变质辉长岩-辉长闪长岩-闪长岩组成,地球化学特征显示其形成于岛弧构造环境。变质中基性岩浆杂岩的TIMS法锆石U-Pb同位素年龄为(507.5±3.0)Ma,表明西秦岭北带岛弧型岩浆岩的形成时代为晚寒武世,反映以关子镇蛇绿岩为代表的古洋盆的俯冲作用和形成火山-岩浆岛弧的时限可能为晚寒武世或稍早。The Liushuigou meta-intermediate-basic igneous complex defined recently in the Guanzizhen area, Tianshui City, West Qinling, is mainly composed of metagabbro-metagabbro diorite-metadiorite. Its geochemical characteristics indicate that the complex formed in an island-arc environment. The TIMS single-zircon U-Pb age for the meta-intermediate-basic igneous complex is 507.5±3.0 Ma, which indicates that the formation age of island-arc-type magmatic rocks in the north zone of the West Qinling are Late Cambrian, and that the timing of subduction of the paleo-ocean basin represented by the Guanzizhen ophiolite and formation of the volcanic-magmatic island arc is Late Cambrian to Early Ordovician.

关 键 词：西秦岭 天水地区 中基性岩浆杂岩体 岛弧型 锆石U-PB年龄 早古生代 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学]