青藏高原拉萨地块发现古元古代地体  

Discovery of the Paleoproterozoic Terrane in Lhasa Block,Qinghai-Tibet Plateau

作　　者：何世平[1,2] 李荣社[1] 王超[1] 张宏飞[2] 计文化[1] 于浦生[1] 辜平阳[1] 时超[1] 

机构地区：[1]西安地质矿产研究所,陕西西安710054 [2]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学（中国地质大学学报）》2013年第3期519-528,共10页Earth Science-Journal of China University of Geosciences

基　　金：中国地质大调查项目"青藏高原前寒武纪地质;古生代构造-古地理综合研究"(No.1212010610102)

摘　　要：拉萨地块东部呈断块状分布的松多岩群包括岔萨岗岩组、马布库岩组和雷龙库岩组,对其形成时代存在较大分歧.通过高精度的LA-ICP-MS(激光剥蚀等离子体质谱仪)锆石微区原位U-Pb同位素测年,西藏工布江达县一带岔萨岗岩组变基性火山岩中获得2450.3±9.9Ma的不一致线上交点年龄,为原岩形成时代,属于古元古代早期,是目前拉萨地块获得的最老基底同位素年龄值.依据野外调研和新获得的同位素年代学数据,结合新近完成的区域地质调查资料,建议将原"松多岩群"解体,新建工布江达岩群(Pt1Gb),松多岩群仅保留马布库岩组(AnOm)和雷龙库岩组(AnOl).拉萨地块古元古代地体的发现,对重新厘定该区前寒武纪基底格架、区域对比、构造归属划分以及寻找与前寒武纪相关的矿产具有重要意义.Songduo rock group includes Chashagang rock formation, Mabuku rock formation and Leilongku rock formation, which takes on fault blocks locating in the eastern Lhasa block, and its age has long been argued. The high accurate LA-ICP- MS zircon U-Pb isotope dating of recta-basic volcanic rock from Chashagang rock formation in Gongbujiangda County, Tibet, yielded a U-Pb upper-intercept age of 2 450. 3±9. 9 Ma. It is suggested a rock-forming age and the oldest isotopic age of base- ment of Lhasa block, belonging to the Early Paleoproterozoic. According to field investigation and the new data of geochronolo- gy, combining with new results from regional geological survey, we propose that ＂the original Songduo rock group＂ should be disintergrated, and re-establish a Gongbujiangda rock group. The Songduo rock Group only remain Mabuku rock formation （AnOm） and Leilongku rock Formation （AnO/）. It is great significance to redefinite the Preeambrian basement framework, compare in region, subdivide tectonic units, and find minerals related with the Precambrian.

关 键 词：拉萨地块 松多岩群 古元古代早期 锆石U-PB年代学 地球化学 

分 类 号：P587[天文地球—岩石学] P597.3[天文地球—地质学]