【摘要】 内蒙古大青山地区孔兹岩系被划分为榴云片麻岩岩组、透辉片麻岩岩组和大理岩岩组。透辉片麻岩岩组中的部分透辉大理岩实际上为壳源碳酸岩。壳源碳酸岩锆石包裹斜锆石、方解石、磷灰石、榍石、石英、长石、辉石等矿物。锆石具核-边结构。透射光和阴极发光下,核部锆石多具密集平行环带,为岩浆成因;边部锆石无明显结构变化,为变质成因。斜锆石在岩浆锆石和变质锆石中都存在。岩浆锆石和变质锆石的年龄分别为1.95～1.93Ga和1.90～1.89Ga。结合地质和岩相学研究,认为大青山地区壳源碳酸岩为透辉片麻岩岩组中的透辉大理岩深熔作用产物,其形成时代为古元古晚期(1.95～1.93Ga),并在稍后(1.90～1.89Ga)遭受变质作用叠加改造。更多还原

【Abstract】 The khondalite suit in the Daqinshan area has been subdivided into garnet-biotite gneiss,diopside gneiss and marble subunits.Diopside marble of diopside gneiss subunit is considered to be crustally derived carbonatitite in terms of geology,petrography,geochemistry,zircon features and dating.Zircons from the crustally derived carbonatite contain various inclusions,including baddeleyite,calcite,apatite,titanite,quartz,feldspar,pyroxene and CO2.The zircons commonly have core-rim structures.Mostly cores show oscillatory zoning in CL and plane polarized light images,suggesting a magmatic origin.The zircon without distinct structural change may represent a metamorphic origin.The baddeleyite inclusions occur in both magmatic and metamorphic zircons.Magmatic and metamorphic zircons from four samples give ages of 1.95～1.93 Ga and 1.90～1.89 Ga,respectively.Combined with geology and lithology,crustally derived carbonatite is the product of anatexis of the diopside marble of the diopside gneiss subunit during the late Paleoproterozoic(1.95～1.93 Ga) and underwent the late metamorphism during a period of 1.90～1.89 Ga.更多还原