A study of ore geology and fluid inclusions of the Jiamante gold deposit, Nilka County, Xinjiang

Abstract：The Jiamante gold deposit in Nilka County of Xinjiang is hosted in a suite of intermediate-acidic lavas and pyroclastic rocks of the Lower Carboniferous Dahalajunshan Formation, and is controlled by a volcanic edifice, with ore bodies being in vein-like and lenticular forms. The ore minerals include chalcopyrite, galena, sphalerite, pyrite, limonite, stibnite, covellite, native gold and native silver, whereas the gangue minerals consist mainly of quartz, calcite, sericite and kaolinite. Ores assume euhedral and subhedral granular, emulsive, metasomatic and cataclastic textures. Colloidal, crustiform, comb, brecciated, banded and massive structures are commonly observed. Petrographic observation, microthermometric measurement and Laser Raman Spectrometry reveal that fluid inclusions in sphalerite and quartz are mainly two-phase and pure liquid phase aqueous ones, belonging to the NaCl-H2O system, and the homogeneous temperatures range from 180 to 260 °C, with the salinities being 0.2-12.5 wt% NaCl.eqv, and the densities from 0.49 g/cm3 to 0.97 g/cm3. All these data show that ore-forming fluids are characterized by low temperature, low salinity and low density. Thus, the characteristics of ore-forming fluid system and ore geology of the Jiamante gold deposit suggest that the ore deposit is of the mesothermal to epithermal lode type, representing a transition from porphyry to epithermal mineralization.