中祁连西段北大河岩群中早古生代火山碎屑岩的识别——来自锆石U-Pb年代学的证据  

SHRMP U-Pb Geochronological Verification on the Identification of Early Paleozoic Volcanic Clasolite Zircons from the Beidahe Complex-Group in the Western Segment of the Middle Qilian Mountains,China

作　　者：彭岩[1,2] 李荣社[2] 计文化[2] 王超[2] 李猛[2] 张辉善 吴中楠 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地质调查局西安地质调查中心,陕西西安710054

出　　处：《西北地质》2014年第4期178-186,共9页Northwestern Geology

基　　金：国家自然科学基金(41102073);中国地质调查局大地调"东昆仑成矿带地质矿产调查评价成果集成"(12120113028800);"秦-祁-昆重要结合带组成;成因及演化研究"(1212011121258)项目联合资助

摘　　要：前人认为北大河岩群是祁连造山带西段最古老的变质岩系之一。笔者在肃北地区该岩群中发现了变质中基性凝灰岩,并对其进行了锆石的LA-ICP-MS U-Pb同位素测定,分析结果表明,该中基性凝灰岩的形成年龄为(444±6.9)Ma,可能为中祁连地块在早古生代发生构造岩浆活动的产物,而并非北大河岩群物质组分。笔者根据野外露头、变质程度及年代学数据将其从北大河岩群中解体出来,并将其重新归属于中下奥陶统吾力沟组。笔者研究结果将为探讨中南祁连的物质组成和地质演化历史提供新的约束材料。Previous researchers thought Beidahe Complex-Group was one of the oldest metamor- phic rocks in the western part of the Qilian orogenic belt. However, according to the SHRMP U- Pb zircon data of the mafic turfs from the Beidahe Complex-Group in Subei area reported in the paper, the intermediate-basic tuffs were formed in （444±6.9） Ma, and they might be the prod- uct of early Paleozoic tectonic-magmatic activity in Mid-Qilian area rather than material compositions of Beidahe Complex-Group. The authors separated the tuff from Beidahe Complex-Group and re-attributed it to Wuligou Formation of Ordovician Series. The results of this study will pro- vide new materials for exploring material composition and geological evolution of middle-south Qilian.

关 键 词：U-PB年龄 中基性凝灰岩 解体 北大河岩群 中祁连 

分 类 号：P597[天文地球—地球化学]