Rb-Sr dating of sphalerites from the Aozigang zinc deposit in Hubei Province and its geological significance

Abstract: The Aozigang zinc deposit lies in eastern Huangling anticline. It is a representative lead zinc deposit recently discovered in western Hubei and Hunan area. The zinc orebodies are strictly controlled by the stratigraphic horizon and lithology, and are mainly hosted in the second member of the Sinian Dengying Formation. The ore-bearing rocks occur in stratoid and lenticular forms, being a suite of brecciform micritic crystal powder dolomites. The Rb-Sr dating of sphalerite separates yielded isochron ages of 431-434 Ma for the deposit, suggesting that the deposit was formed in the early Silurian, which represents the main ore-forming epoch of the deposit. Based on a study of the source of the ore-forming material and the geological significance, the authors hold that higher initial ratios of Sr isotope (0.71119-0.71136) suggest that the metallogenic substances or ore-forming fluids came from relatively high basement rocks and relatively low Sinian carbonate layers. The early mineralization of the Aozigang zinc deposit was closely related to the Early Silurian stretching rift basin, whereas the late mineralization was closely associated with the Caledonian movement and was the product of fluid migration in a stretching basin. The mineralization of the lead-zinc deposits around the Huangling faulted dome was closely related to Caledonian movement. The Aozigang zinc deposit is genetically of hydrothermal karst type, and its formation can be divided into deep burial diagenetic ore-forming stage and hydrothermal karst metallogenic stage.