LA-ICP-MS zircon U-Pb age and genesis of Longbucun granite in Southern Gangdise Belt, Tibet

Granite has important significance for the study of ocean plate subduction and continent-continent collision under certain conditions. Longbucun granite belongs to the middle part of Southern Gangdise Belt, and the formation age of the granitoids in this belt is a subject of much controversy. The LA-ICP-MS U-Pb zircon age of Longbucun granite is 157.0Ma±2.9Ma, which shows that there existed granitic magmation in the Late Jurassic in Southern Gangdise Belt. Longbucun granite is enriched in such large-ion lithophile elements as Rb, Ba, Th, U and K and depleted in the high field strength elements like Nb, Ta and Ti, suggesting the features of island arc magmatic rocks and indicating that there existed an early-stage northward subduction of the Neo-Tethys Ocean to the Eurasian Plate in the Late Jurassic period. Longbucun granite was formed by partial melting of the mantle wedge under the subduction of the Neo-Tethys plate.