西藏嘉黎县措麦地区含石榴子石二云母花岗岩锆石SHRIMP U-Pb年龄及其意义

SHRIMP zircon U-Pb age of garnet-bearing two-mica granite at Comai Township, Lhari County, Tibet, and its significance

1∶25万门巴区幅区域地质调查首次于嘉黎县措麦地区发现了含石榴子石二云母花岗岩,并对其进行了详细的野外地质研究。该花岗岩单颗粒锆石SHRIMPU-Pb年龄的测定结果为123.4Ma,是早白垩世岩浆活动的产物。岩石地球化学研究表明,其属钙碱性系列的强过铝质S型花岗岩,是地壳重熔的产物。它的发现揭示了本区早白垩世的同碰撞事件,并为本区在晚侏罗世—早白垩世时期发生陆内汇聚作用提供了约束。

During 1∶250000 regional geological survey of the Mamba Sheet, we found garnet-bearing two-mica granite near Comai, Lhari County, Tibet, for the first time and carried out intensive field investigation. Single-zircon SHRIMP U-Pb dating of the granite gave an age of 123.4 Ma, indicating that the granite is the product of Early Cretaceous magmatism. Geochemical study of the rock indicates that it is strongly peraluminous S-type granitoids of the calc-alkaline suite and a product of anatexis of the crust. This discovery reveals the Early Jurassic syncollision event in the area and provides constraints on the crustal shortening and thickening in the Late Jurassic-Early Cretaceous in this area.