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.