| The Jiamante gold deposit, Nileke County, Xinjiang, is an epithermal gold deposit founded by No.703Geological Team, Xinjiang Geoexploration Bureau for Nonferrous Metals. This year, I have done lots of basic study and testing experiments, from which I get much data and some conclusions.This deposit is hosted in a suite of intermediate-acidic lavas and pyroclastic rocks of the Lower Carboniferous Dahalajunshan Formation, and controlled by a volcanic edifice, with orebodies being vein-like and lenticular in shape. The ore minerals include chalcopyrite, galena, sphalerite, pyrite, limonite, stibnite, covellite, native gold and native silver; the ganaue minerals are mainly quartz, calcite, sericite and kaolinite. Ore textures are euhedral and semi-euhedral granular, emulsion, replacement and cataclastic. Colloidal, crustiform, comb, brecciated, banded and massive structures are commonly observed.The hydrothermal ore-forming process includes the early, middle and late stages, characterized by mineral assemblages of quartz-pyrite feldspar, quartz-polymetal and quartz-carbonate, respectively.Petrographic observation, microthermometric measurement and Laser Raman Spectrometry reveal that the fluid inclusions in sphalerite and quartz are mainly two-phase and pure liquid phase aqueous, i.e., NaCl-H2O system; and the homogeneous temperatures range from180to260℃, with salinities ranging0.2～12.5wt%NaCl.eqv, and the densities from0.49g/cm3to0.97g/cm3. This shows that ore-forming fluids are characterized by low temperature, low salinity and low density.Thus, the natures of ore-forming fluid system and ore geology of the Jiamante gold deposit suggest that the deposit is a mesothermal to epithermal lode system, representing a transition from porphyry to epithermal mineralization. |
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