内蒙古阿拉善左旗巴音诺尔公花岗岩体TIMS锆石U-Pb年龄

内蒙古自治区阿拉善东南部的巴音诺尔公花岗岩体,地处华北陆块西北缘,霍尔森-查干楚鲁构造带以南的雅布赖-巴音诺尔公构造带内。岩体整体上受NEE向构造控制,主要由中-细粒黑云母花岗岩和中-粗粒似斑状黑云母花岗岩2种岩石类型组成。采用TIMS锆石U-Pb定年法,测得巴音诺尔公岩体不同位置中-细粒黑云母花岗岩和中-粗粒似斑状黑云母花岗岩样品年龄分别为304.7±2.8Ma和289.0±3.8Ma,属于晚石炭世—早二叠世。结合前人资料,提出巴音诺尔公岩体至少存在2期岩浆活动,分别为晚石炭世(304Ma)和早二叠世(289~272Ma)。

Times zircon U-Pb age of Bayinnuoergong granite pluton of Alxa Block, Inner Mongolia

The Bayinnuoergong granite pluton in the southeast of Alxa Block is located to the northwest of North China Craton and distrbuted in Yabula-Bayinnuoergong tectonic belt in the south of Huoershen-Chaganchulu tectonic belt, controlled generally by NEE-trending structure. It consists of medium to fine grained biotite granite and medium to coarse porphyritic biotite granite. Re-searchers have done some research on the ages of the Bayinnuoergong granite, which provides a favorable condition for analyzing and discussing whether the Bayinnuoergong intrusion formed in multiperiodic magmatic activities. TIMS U-Pb dating of zircons from the Bayinnuoergong medium to fine grained biotite granite and medium to coarse porphyritic biotite granite yielded two ages of 304.7±2.8Ma and 289.0±3.8Ma, respectively, indicating that the pluton should be the Late Carboniferous-Early Permain intrusion. Combined with the previous research in the study area, it is held that there are at least two magmatic activities in this area, which oc-curred in Late Carboniferous (304Ma) and Early Permian (289~272Ma).