东昆仑东段原特提斯洋俯冲的岩浆响应:来自晚震旦世锆石U-Pb年龄的证据

东昆仑造山带新元古代岩浆岩的研究对原特提斯洋的演化具有重要意义.选取东昆仑造山带东段可可沙地区晚震旦世敦德沙尔郭勒角闪二长岩为研究对象，运用锆石U-Pb年代学方法，结合已有的区域地质资料，为新元古代晚期-早古生代的"泛非造山运动"及东昆仑弧后盆地拉张裂解及原特提斯洋俯冲消减时限提供约束.敦德沙尔郭勒角闪二长岩岩石学和岩石地球化学特征显示其具有钾质碱性岩的特征，样品11029/8中所挑锆石均具有岩浆韵律环带，具有较高Th/U比值（0.21~0.41），为岩浆成因锆石.LA-ICP-MS锆石U-Pb年龄为544.8±7.8 Ma（MSWD=5.7），属于震旦纪晚期或寒武纪早期.敦德沙尔郭勒角闪二长岩是原特提斯洋向北俯冲的产物. 

Magmatic Response to Proto-Tethyan Ocean Subduction in East Section of East Kunlun: Evidence from Zircon U-Pb Dating of Late Sinian Dundeshaerguole Hornblende Monzonite

The study of Neoproterozoic magmatic rocks in the East Kunlun orogenic belt has important significances for the evolution of Proto-Tethys. Taking the Late Sinian Dundeshaerguole hornblende monzonite in east section of East Kunlun as research object, this paper constrains on the Pan-African orogenic events, tension and breach of back-arc basin in East Kunlun and Proto-Tethyan Ocean subduction by the zircon U-Pb dating in combination with regional geological data.The lithological and geochemical data indicate that Dundeshaerguole hornblende monzonite is characterized by potassic alkaline rocks. All the zircons selected from sample 11029/8 have magmatic oscillatory zoning, high Th/U ratios of 0.21-0.41, representing the magmatic origin. The LA-ICP-MS zircon U-Pb dating shows age of 544.8±7.8 Ma (MSWD=5.7), belonging to Ediacaran period in Sinian or Early Cambrian. It is concluded that the Dundeshaerguole hornblende monzonite is the products of northward subduction of Proto-Tethys.