Characteristics of the Au-Ag-Te minerals and its ore-forming fluids in Sandaowanzi gold deposit, Heilongjiang Province

By means of optical microscope, scanning electron microscope and electron probe analysis, we made a thoroughly study of the tellurides in the gold deposit of Sandaowanzi, Heilongjiang. Compound Au2Te is first discovered in this research, except for hessite, petzite, sylvanite, krennerite and calaverite. These telluride minerals appear as granule, intergrowth or veinlet in the fractures of sulfides and quartz. In the system of Au-Ag-Te tullurides, the content of gold is negatively correlated with the content of silver and has a slightly negatively correlation with tellurium. The paragenetic association of Au-Ag tellurides in sandaowanzi gold deposits has been studied based on the experimental results in Au-Ag-Te ternary system. The experiments show that Te always give priority to combine with Ag to form hessite or petzite, sylvanite, krennerite and calaverite are generated only after a huge consumption of Ag, and only after Te in the fluid consuming a lot can nature gold be generated. Helium isotope studies of fluid inclusions indicate that the ratio He-3/He-4 is 0.01 similar to 0.03Ra in the stage of pyrite-quartz, while it is 0.08 similar to 1.04Ra in the stage of tellurides, which indicated that large quantities of mantle fluids were involved in the stage of tellurides.