Fluid inclusion characteristics and geological significance of the Dajinshan W–Sn polymetallic deposit in Yunfu, Guangdong Province

•Dajinshan tungsten–tin polymetallic deposit experienced three stages.•Four types of fluid inclusions are identified.•Fluids are magmatic thermal fluid mixed with cryogenic fluids.•Boiling and mixing of various fluids is the main mechanism in mineralization.

The Dajinshan tungsten–tin polymetallic deposit is a quartz-vein-type ore deposit located in Western Guangdong Province. The ore bodies show a fairly simple shape and mainly occur as tungsten–tin polymetallic-bearing sulfide quartz veins, including quartz vein, quartz-greisens, and sulfide quartz veins, and their distribution is spatially related to Dajinshan granitoids. The formation of the deposit experienced three stages: a wolframite–molybdenite–quartz stage, a wolframite–cassiterite–sulfide–quartz stage, and a fluorite–calcite–carbonate stage. Based on detailed petrographic observations, we conducted microthermometric and Raman microspectroscopic studies of fluid inclusions formed at different ore-forming stages in the Dajinshan tungsten–tin polymetallic deposit, identifying four dominant types of fluid inclusions: aqueous two-phase inclusions, CO2-bearing inclusions, solid or daughter mineral-bearing inclusions, and gas-rich inclusions. The gas compositions of ore-forming fluids in the Dajinshan tungsten–tin polymetallic deposit are mostly CO2, CH4, and H2O. The hydrogen, oxygen, and sulfur isotopic data imply that the ore-forming fluids in the Dajinshan tungsten–tin polymetallic deposit were mainly derived from magmatic fluids, mixed with meteoric water in the ore-formation process. These results indicate that the fluid mixing and boiling led to the decomposition of the metal complex in ore-forming fluids and ore deposition.