内蒙古塔尔气地区佳疙瘩组地质特征及锆石年代学研究

通过对塔尔气地区佳疙瘩组的岩石学、构造、地球化学及锆石年代学等特征的研究,对该组岩石的变形特征、构造背景及形成时代进行了探讨。结果表明,研究区出露的佳疙瘩组以二云母石英片岩、绿泥片岩及石英岩为主,变质矿物组合为:石英+角闪石+黑云母+斜长石,变质程度相当于绿片岩相。锆石LA-ICP-MS U-Pb年代学、岩石地球化学测试分析结果表明,其形成时代应为晚奥陶世晚期,原岩为一套中酸性火山岩。后期经历了两期变质变形事件:第一期应力场为北西—南东向挤压,形成北东向展布的构造线;第二期变形应力场为近南北向挤压,形成近东西向展布的构造线方向,时代可能为早石炭世之后。

Ｒesearch on geological characteristics and zircon U-Pb age of Jiageda Formation in Taerqi，Inner Mongolia

The authors studied the characteristics including petrology，tectonics，geochemistry and zircon U- Pb dating，and discussed deformation features，regional tectonic background and formation age for the Jiageda Formation in Tarqi areas． The results show that the Jiageda Formation is mainly composed of mica quartz schist，chlorite schist and quartzite． The metamorphic mineral assemblage is quartz + amphibole + biotite + plagioclase． The metamorphic grade is equivalent to greenschist facies． The LA-ICP- MS U-Pb dating for zircon and geochemical analyses of the samples indicates that it should be formed in late Late Ordovician． The protolith is a set of inter- mediate- felsic volcanic rocks． Jiageda Formation underwent two- phases deformations: the first phase of the stress field direction of NW－SE trending extrusion，forming ne structure in the direction of distribution line; the second phase of stress field direction of NS trending extrusion，forming EW structure in the direction of distribution line， which might occur after Early Carboniferous．