富湾超大型银矿床Ar-Ar年龄、铅同位素特征及形成条件分析

The Fuwan superlarge silver deposit is hosted in the Early Carboniferous limestones along a contact fault zone between the limestone and the overlying Changkeng Au-hosting siliceous rocks. The 40Ar-39Ar age of the ore-related quartz veins from the Fuwan silver deposit is (64.3±0.1) Ma. The silver deposit is characterized by high μ values (10.67~10.95) in Pb isotopic composition, being much higher than those of the Paleozoic ore-hosted strata and being similar to those of ores hosted in Preterozoic metamorphic base in the Western Guangdong Province. It is concluded that the ore forming material of the superlarge silver deposit came primarily from the Proterozoic basement. The superlarge silver deposit owns its origin to the Himalayan volcanic activities in the region of the Sanshui Basin. The formation of Fuwan superlarge silver deposit is controlled by the following favorable geological conditions: The intersection of deep faults and contemporaneous faults at the margins of the Sanshui Basin served as excellent passageways for ore fluids; the special ore-hosted rock association served as the ore-concentration and ore-trapping structures; the silver-rich basement, multiple stages of mineralization and of mobilization of silver and related elements; geothermal convection system related to multiple episodes of volcanic activities.