CHARACTERISTICS OF ZAOZIGOU GOLD DEPOSIT: AN INVESTIGATION OF A POSSIBLE CARLIN TYPE DEPOSIT

The purpose of this work is to shed light on the Zaozigou gold deposit through a systematic study in describing the mineralization, integrating fluid inclusions, and microanalysis to define and provide a representation of the deposit in the Qinling Belt.

Field and laboratory investigations demonstrated a variety of host rocks for the gold mineralization principally calcareous slate, argillite, siltstone and shale and some igneous dikes that occur with some orebodies. These orebodies are controlled by high to low angle faults normal or reverse principally NE, NW, and NS.

The mineral association consists principally of pyrite, arsenopyrite, stibnite, rutile and low sphalerite, galena, marcasite, pyrrhotite and very minor chalcocite and manganite; whereas gangue minerals are sericite, hydromica, kaolinite, quartz, and calcite. However the absence of orpiment and realgar typical Carlin deposit minerals suggests a mesothermal environment, although the alteration present consists mainly of silicification, argillization, carbonization and decalcification, but also chloritization, sulfidation at different intensity.

Fluid inclusions (120^oC to 300^oC) with salinity comprises between 3 to 16 wt% NaCl equiv indicating a pressures of 282–618 bars assumed a hydrostatic conditions and which indicates that the deposits formed from low to moderate salinity and minor CO₂ (< 4 mol%) in reduced environment with sufficient H₂S to transport Au at relatively shallow level in the crust.

The microanalytical (EMPA) results show that arsenian pyrite, arsenopyrite and stibnite compositions plotted in a solubility diagram confirm the presence of Au⁰ and Au⁺¹ . The solid solutions (Au⁰) contents are an As dependent principally the Au associated to arsenopyrite. Whereas the nanoparticles gold Au ⁺¹ are present somewhere in the absence of As content, except the Au associated to stibnite mineral. The submicron sized gold was found in silica and quartz fracture by using ESEM.

Thus the paragenetic sequence, fluid inclusions and microanalysis results play in favor of Carlin deposit signature and, remarkably similar to many deposits in Nevada, Iran and China Qinling Belt.