Study Of The Metamorphosed Basement In Tamusu Region Of Aixa Youqi, Inner Mongolia

The Zhagaitu gneiss and the Mctamorphie basite dike of Precambrian were identified in Alxa Youqi,west inner Mongolia on the basis of 1:50000 regional geological survey.The study region is located on the western section of northern edge of NorthChina Platform.The paper is based on fieldwork and office analysis,studing the charaeteristic of metamorphic rock of Precambrian in TaMuSu region,Which included the charaeteristic of macroscopic geology,the type of rock,the texture and structure of rocks, Paragenetic association of mineral,rock chemistry,micro element,rare earth element geochemistry and charaeteristic of primary rock,the metamorphic faeies,the metamorphic type, and temperature-pressure condition,the mechanism of the metamorphism.The ages of zircons from the samples are 1108±74Ma of The Zhagaitu gneiss,respectively,implying that they were formed by Neoproterozoic.The charaeteristic of metamorphic mineral and the paragenetic association of metamorphic mineral show that the regional metamorphism corresponds to amphibolite facies, The thermodynamics condition is P—0.39GPa, evaluation temperature is T—700～800°C, the mother rocks are tonalite—granodiorite—quartz dioite.The ages of zircons from the samples of the Mctamorphic basite dike of Precambrian are 1404±100Ma,early time of Neoproterozoic. Which are greenschist facies—amphibolite facies,the mother rocks are argillaceous sandstone with part of andesite.And the structural situation of passive continental margin, which thermodynamics condition is P—0.39GPa, evaluation temperature is T—550～650℃.The metamorphosed basement in study area maybe in connection with closing of continental marginat chasmic basin which happened at lately Mesoproterozoic to early Neoproterozoic in northern edge of NorthChina Platform.