Metallogenesis of the main collisional period in mid-western Gangdise:Zir-con U-Pb geochronology of the granite porphyry in Dexin deposit, Tibet

The Dexin Ag-Pb-Zn deposit, located in the Longgeer-Gongbujiangda fault-block uplift belt at the center of Lhasa Ter-rane, is one of the representative hydrothermal type deposits in the Gangdise Ag-Pb-Zn polymetallic ore-forming belt.The Pb-Zn mineralization dominantly occurs in the fractures of wall rocks and the granitic porphyries.Zircons from the ore-bearing granitic por-phyry in Dexin were measured by the LA-ICP-MS U-Pb dating method, which yielded a weighted average ²⁰⁶Pb/²³⁸U age of 57.7±0.5Ma (MSWD=1.6, n=15) that represents the formation age of the granitic porphyries and the Pb-Zn mineralization in the granitic porphyries.With a comprehensive analysis of geological background, it is concluded that the Pb-Zn mineralization associated with the granitic porphyries in Dexin and the cryptoexplosive breccia type Pb-Zn mineralization in Narusongduo were formed by the same magmatic metallogenic system, and there were many magmatic-metallogenic events near/in the main Indian-Asian collisional period in the mid-west part of Gangdise.