Zircon U-Pb Chronology of Kuanping Rock Group By LA-ICP-MS and its Geological Significance

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.