【摘要】 甘肃天水东岔镇一带出露的宽坪岩群位于北祁连—北秦岭—华北板块交界地带,呈残留体状分布于花岗岩之中,主体为一套低角闪岩相变质的片麻岩、片岩夹斜长角闪岩。利用西北大学大陆动力学重点实验室LA-ICP-MS(激光剥蚀等离子体质谱)方法,对其中的斜长角闪岩进行单颗粒锆石微区U-Pb同位素测定,获得1753±14Ma的上交点年龄,为古元古代晚期;并反映出415±2Ma～383±2Ma的变质年龄信息。结合前人研究成果,认为区域上宽坪岩群主体形成年龄为中元古代,而研究区的宽坪岩群形成于古元古代,受到加里东晚期和华力西早期构造—热事件的改造。推测研究区的宽坪岩群可能属于华北古老基底南缘的组成部分。更多还原

【Abstract】 Kuanping Rock Group that lies in Dongcha area,Tianshui,Gansu Province,is located in the join place of the North Qilian orogenic belt,the North Qinling orogenic belt,and the North China plate.It shows some remaining bodis surrounding in granites,and is mainly composed of gneiss,schist,and a little of amphibolite.U-Pb isotope of zircons from amphibolite are determined by LA-ICP-MS in the key laboratory of continental dynamics of Northwest University,and yielded a zircon U-Pb upper-intercept age of 1753±14Ma and metamorphic age informations from 415±2Ma to 383±2Ma.According to the earlier research results,this article considers that main part of Kuanping Rock Group formed in Mid-Proterozoic in the all region.However,Kuanping Rock Group in the study area formed in Late Paleo-Proterozoic,and was reconstructed by tectonic-hot events in late Caledonian stage and early Varisca stage.The writers infer that Kuanping Rock Group in the research region may belong to the south part of the ancient basement of the North China.更多还原