Mineralogical, fluid inclusion, and multiple isotope (H-O-S-Pb) constraints on the genesis of the Sandaowanzi epithermal Au-Ag-Te deposit, NE China

The Sandaowanzi gold deposit in the Great Hinggan Range metallogenic belt, northeast China, is unusual because the mineralization takes the form of Au- and Ag-bearing tellurides. This mineralization, which constitutes a resource of 28 t Au, is hosted in 20 NW-trending, syntaxial, layered quartz veins and tension gashes within almost coeval trachyandesites and andesitic breccias that overlie the Sandaowanzi monzogranite. Alteration halos are developed around the quartz veins and tension gashes. They consist of an inner silicic-pyritic zone, two intermediate zones containing quartz-illite-sericite and quartz-adularia, and an outer zone containing a quartz-calcite-kaolinite-chlorite assemblage. Fluid inclusion microthermometric data reveal that the Sandaowanzi ores precipitated from moderate-temperature (200°–280°C), low-pressure (70–130 bar), and low- to moderate-salinity (mostly <6.0 wt % NaCl equiv) hydrothermal fluids. Temperature and pressure are interpreted to have decreased with the evolution of the system. The