西天山古元古代木札尔特岩群地质特征及时代厘定

摘要

西天山木札尔特岩群发育于塔里木原始古陆台内毗邻陆缘活动带,为一套角闪岩相中深变质岩系,主要岩石组合为变粒岩-浅粒岩-片麻岩-斜长角闪岩-大理岩等,局部受韧性变形改造形成各类糜棱岩系,原岩为中基性火山熔岩-火山碎屑岩-火山碎屑沉积岩夹碳酸盐岩建造.由于缺少古生物化石,其地层时代主要依据区域地层对比和同位素年代学数据进行确定.笔者应用钐钕全岩等时线定年法,在该岩群斜长角闪岩中获得(1966±93)Ma的同位素年龄,这是迄今为止,西天山范围内该岩群内获得的最古老同位素年龄,代表了其成岩年龄.据国际地层表(2000)关于古元古界造山系2050～1800 Ma的划分方案,笔者最终将西天山木札尔特岩群成岩时代厘定为古元古代造山纪.%The Muzhaerte Group Complex in western Tianshan Mountains formed in the mobile belt of the Tarim proto-contcnent margin.lt's main rock group is leptynite-leptite-gneiss-amphibolite-marble etc.which passed with hornblend-phase regional metamorphism and all kinds af mylonite which passed with ductile shear deformation in the strain localization region. The protolish of Muzhaerte Group Complex is intermediate-busic pyroclastic lava-pyrolastic rock-pyroclastic sedimentary rock via carbonate rock formation. Because of the lack of extinct animals and plants fossil,it's diagonesis age has been one of the controversial issues in the geological community for a long time. What's more, the diagonesis age assurance of Muzhaerte Group Complex mainly based on regional stratigraphic correlation and isotopic age determination. The isotopic age of ((1966±93) Ma) had been obtained from amphibolite of Muzhaerte Group Complex through Sm-Nd total-rock isochron method by writer,and was stand for Muzhaerte Group Complex time which is the earliest isotope age founded in this geologic body in Western Tianshan by now.According to the project of 2050～1800 Ma about Orogemc System of Palaeoproterozoic in intemational stratigraphic table(2000),writers think that the diagonesis age of Muzhaerte Group Complex is in Orogenic Period of Palaeoproterozoic.