Rb-Sr isochron age of the Heilongtan Au-deposit in Suizhou, Hubei Province, and its geological significance

The age of the Heilongtan gold deposit in northern Hubei Province was determined by the Rb-Sr isochron method.Six samples of quartz-hosted fluid inclusions yielded a Rb-Sr isochron age of 132.6±2.7Ma, suggesting that the Heilongtan gold deposit was formed in the Late Cretaceous.The (⁸⁷Sr/⁸⁶Sr) _i initial ratio of the isochron is 0.710798, which is lower than that of the terrige-nous silicates (0.720) but higher than that of the mantle (0.707), implying that ore-forming materials were derived from a mixture of crust and mantle components.Combined with the reported S and Pb isotopes, the authors hold that the ore-forming process of the Heilongtan gold deposit was probably related to the Late Mesozoic magmatism in an extensional setting.The magmatism might have provided sufficient heat energy, fluid, sulfur and gold for the mineralization of the Heilongtan gold deposit.