Fluid inclusion constraints on the origin of the Zhengguang gold deposit, Heihe City, Heilongjiang Province

The Zhengguang gold deposit, Heihe City, Heilongjiang Province, is located in the Duobaoshan metallogenic belt in the northeastern Great Hinggan Range. The Au-bearing veins occur in the contact zone between diorite pluton and the Middle Ordovician Duobaoshan Formation, and are controlled by faults. Hydrothermal mineralization can be divided into four stages, i.e., quartz-pyrite stage (1), quartz-polymetallic sulfide stage (2), calcite-quartz-polymetallic sulfide stage (3) and carbonate stage (4), with stages 2 and 3 as the main Au mineralization stages and characterized by complicated metallic mineral assemblage of pyrite-sphalerite-galena-chalcopyrite±native gold. Fluid inclusions in quartz and calcite are aqueous (NaCl-H2O) inclusions and 3~15μm in size, with bubbles accounting for 5vol%~10vol%. These inclusions yield total homogeneous temperatures of 119~305℃, salinities of 0.3%~10.4% NaCleqv, and densities of 0.76~0.99g/cm3. The homogeneous temperatures of fluid inclusions decrease gradually, from 150~220℃ at stage 2, through 140~190℃ at stage 3, to 130~150℃ at stage 4. Based on the geological and fluid inclusion features, we conclude that the Zhengguang deposit is a typical low sulfidation epithermal deposit.