内蒙古巴彦乌拉山古元古代斜长角闪岩LA-ICP-MS锆石U-Pb年龄和Hf同位素组成  

LA-MC-ICP-MS zircons U-Pb dating and Hf isotopic compositions of the Paleoproterozoic amphibolite in Bayan Ul area, Inner Mongolia

作　　者：包创[1] 陈岳龙[1] 李大鹏[1] 

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

出　　处：《地质通报》2013年第10期1513-1524,共12页Geological Bulletin of China

基　　金：国家自然科学基金项目(批准号:40973010)

摘　　要：巴彦乌拉山岩组形成于古元古代，而对其斜长角闪岩的精确定年数据尚缺。采用LA-Mc-IcP-MS技术．对巴彦乌拉山岩组斜长角闪岩及侵入于其中的花岗岩进行了锆石U-Th-Pb和Lu-Hf同位素组成分析，确定巴彦乌拉山组斜长角闪岩原岩形成于2300Ma。根据区域地质背景，斜长角闪岩原岩可能来自叠布斯格岩群的再循环产物，并且遭受了1988-2239Ma和1892-1940Ma的变质一深熔事件，其中1892-1940Ma的年龄可能代表斜长角闪岩先期变质一深熔和花岗岩的形成时代，反映了阴山地块与鄂尔多斯地块拼接的强烈构造事件；1813～1877Ma的年龄为花岗岩的变质及先期高级变质岩退变质为斜长角闪岩的年龄，主要反映了华北板块东、西部块体的拼合事件。而斜长角闪岩中没有1813-1877Ma的年龄记录，可能是构造热事件的温度不足以引起已经发生过多次部分熔融的斜长角闪岩干体系再次发生熔融而结晶锆石。The Bayan U1 Formation was formed in Paleoproterozoic, but the precise dating data of the amphibolite are very insuffi- cient. In this paper, the authors present U-Pb ages and Lu-Hf isotopic compositions of amphibolite and associated granite in the Bayan U1 Formation by mean of LA-MC-ICP-MS. Combined with data of the granite that intruded into the amphibolite, the au- thors hold that the protolith of amphibolite was formed at 2300Ma. Based on regional geological setting, it is suggested that the amphi- bolite＇s protolith was the recycled product of the Diebusige rock group and expereinced two metamorphic episodes that occurred in 1988-2239Ma and 1892-1940Ma respectively. The period of 1892-1940Ma might represent the formation age of granite and former metamorphic facies （granulite） of amphibolite, which indicated the collision between the Yinshan and Ordos blocks. The 1813-1877 Ma might signify the metamorphic age of granite and retrograde metamorphism from grannlite to amphibolite, which indicated the collision time between the west and east blocks in the North China Plate. The age of 1813-1877Ma was recorded only in the granite and not in the amphibolite, which implies that the amphibolite in the dry system could not generate partial melting again after repeated partial melting.

关 键 词：巴彦乌拉山 古元古代 斜长角闪岩 LA-ICP-MS锆石U-Pb HF同位素组成 

分 类 号：P534.3[天文地球—古生物学与地层学] P597.3[天文地球—地质学]