Sources of Ore-Forming Fluids and Materials of Gold and Antimony Deposits in Southwestern Guizhou

Southwestern Guizhou is a main distribution area of Carlin-type gold deposits in China, and rich in epithermal deposits like antimony, arsenic and mercury. The elemental paragenesis-separation is common among these deposits, especially between gold and antimony. This paper systematically analyzes the fluid inclusions and isotope geochemistry of two typical deposits in southwestern Guizhou, namely, Shuiyindong gold deposit and Dachang antimony deposit. The analysis shows that the ore-forming fluids from the two deposits have similar properties and the same origins, and the ore-forming materials of the two deposits come from the same sources: the ore-forming fluids from both deposits are of low to medium temperature, low to medium salinity and medium density; both of them might belong to the system of H2O-NaCl-KCl-CO2. The tests on gas-liquid phase compositions and H-O isotopes indicate that the ore-forming fluids of both gold and antimony deposits come from multiple sources; the main source is the underground hot fluid formed from meteoric water, and a few amount of magmatic fluid and even mantle fluid might also be involved in the formation of the fluids. The sulfur isotope test reveals that the delta S-34 values of gold and antimony deposits both concentrate in a small range near 0%, and the S isotope composition is similar to that of mantle sulfur, indicating that the sulfur in the ore-forming materials of the gold and antimony deposits mainly come from deep mantle. The research results lay the theoretical basis for the metallogenic factors in southwestern Guizhou.