特提斯喜马拉雅构造带雅拉香波穹隆构造热事件LA-ICP-MS锆石U-Pb年龄证据

摘要

Paleozoic-Cenozoic rocks and strata together with intense ductile shearing and magmatic thermal events occurred in the Yalaxiangbo (Yardoi) dome of eastern Tethys Himalayan belt, which well recorded the structural deformation and thermal history caused by northward subduction of the Indian Continental Plate. LA-ICP-MS U-Pb isotopic dating of zircons with clear growth zonation selected from granitic rocks sampled in different structural zones reveals high-resolution ages of four periods of tectonic-magmatic events that took place in the Yalaxiangbo dome. The U-Pb isotopic ages of zircons, 520.4 ± 6.3Ma and 536 ± 12.3Ma, are indicative of magmatic emplacement of the Pan-African orogeny in the crystalline basement of the Himalayan block. The other U-Pb isotopic ages of zircons reveal geological epochs of tectonic-thermal events during Cenozoic collisional orogeny, e.g., ages 45.6± 1.2~44.16±0.88Ma are indicative of the initial time of the northward subduction of the Indian Continental Plate, 35.00±0.48Ma is a representative age for Late Eocene tectonic-thermal event that occurred in the depth of the thickened crust, and 15.67±0.50Ma indi-cates the epoch of the emplacement of the core granite and the formation of the Yalaxiangbo dome.%雅拉香波穹隆位于特提斯喜马拉雅构造带东部，出露显生宙不同时期的岩石地层，发育强烈韧性剪切变形和多期岩浆热事件，良好地记录了印度大陆俯冲导致的构造变形和岩浆热历史。对雅拉香波穹隆不同构造部位的花岗质岩石进行LA-ICP-MS锆石U-Pb同位素测年，获得4期构造岩浆事件的高精度测年数据。早期锆石年龄520.4±6.3Ma与536±12Ma指示喜马拉雅地块结晶基底泛非期岩浆侵位时代，晚期锆石年龄揭示新生代碰撞造山不同阶段构造热事件的发生时代。其中，45.6±1.2~44.16±0.88Ma反映印度大陆向北俯冲的起始时代，35.00±0.48Ma对应于始新世晚期增厚地壳深部构造热事件年龄，15.67±0.50Ma指示雅拉香波核部花岗岩侵位及穹隆的形成时代。