今天是2017年09月22日

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青藏高原拉萨地块发现古元古代地体

DOI:10.3799/dqkx.2013.052

作者:何世平;李荣社;王超;张宏飞;计文化;于浦生;辜平阳;时超

联系地址:西安地质矿产研究所;中国地质大学地球科学学院

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. 更多还原

关键字: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

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

Author:HE Shiping, LI Rongshe, WANG Cha, ZHANG Hongfei, JI Wenhua, YU Pusheng, GU Pingyang, SHI Chao

Author Address:1.Xian Institute of Geology and Mineral Resources, Xian710054, China 2.Faculty of Earth Sciences, China University of Geosciences, Wuhan430074, China

Abstract: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 meta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 basement of Lhasa block, belonging to the Early Paleoproterozoic. According to field investigation and the new data of geochronology, 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 (AnOm) and Leilongku rock Formation (AnOl). It is great significance to redefinite the Precambrian basement framework, compare in region, subdivide tectonic units, and find minerals related with the Precambrian

Keyword:Lhasa block; Songduo rock group; Early Paleoproterozoic; zircon U Pb geochronology; geochemistry

 

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作者简介:何世平(1963-),男,研究员,主要从事大地构造、地球化学研究

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