西秦岭北缘新元古代花岗质片麻岩的LA-ICP-MS锆石U-Pb年龄及其地质意义  

Zircons LA-ICP-MS U-Pb Dating of Neoproterozoic Granitoid Gneisses in the North Margin of West Qinling and Geological Implication

作　　者：裴先治[1] 丁仨平 张国伟[2] 刘会彬[1] 李佐臣[1] 李王晔[3] 刘战庆[1] 孟勇[1] 

机构地区：[1]长安大学地球科学与国土资源学院,西安710054 [2]西北大学大陆动力学国家重点实验室,西北大学地质学系,西安710069 [3]中国科学技术大学地球与空间科学学院,合肥230026

出　　处：《地质学报》2007年第6期772-786,共15页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40572121;40234041);教育部科学技术研究重点项目(编号104175);中国地质调查局地质调查项目(编号200013000154)资助成果

摘　　要：西秦岭造山带北缘古元古界变质杂岩中新识别出新元古代元龙花岗质片麻岩和新阳花岗质片麻岩。花岗质片麻岩中锆石Th/U比值较高,阴极发光图象显示锆石内部发育振荡环带,具岩浆成因特点。LA-ICP-MS锆石U-Pb同位素206Pb/238U加权平均年龄分别为914.7±7.6Ma(MSWD=4.8)、978.5±4.8Ma(MSWD=1.5)和935.5±3.1Ma(MSWD=1.3),表明花岗岩岩体形成于新元古代,反映了新元古代早期西秦岭北缘存在一次俯冲碰撞事件,与Rodinia超大陆的汇聚事件具有一致性。The Xinyang and Yuanlong Neoproterozoic granitoid gneisses was identified from the Paleoproterozoic Qinling complex in the north margin of the Western Qinling orogen. Zircons from the granitoid gneisses have higher Th/U ratios and the clear oscillatory zonings in internal CL images, indicating that they are igneous in origin. The acquired 206pb/238U weighted average ages of LA-ICP-MS zircon U-Pb isotope is 914.7±7. 6 Ma（MSWD=4.8）, 978. 5±4.8 Ma（MSWD=1.5）and 935. 5±3. 1Ma（MSWD=1.3）, indicating that the granitoid gneisses was formed in the Neoproterozoic, and there was a thermal event （subduction and collision） in the north margin of the western Qinling Orogen during the early Neoproterozoic age, which was presumed to be the response of the Rodinia Supercontinent convergent evolution in Western Qinling.

关 键 词：新元古代 花岗质片麻岩 LA-ICP-MS定年 锆石U-Pb年龄 西秦岭 

分 类 号：P588.3[天文地球—岩石学] P579.3[天文地球—地质学]