| The Jinchang gold-nickle deposite is the only gold-nickle deposit in Ailaoshanorogenic belt. Based on the research of geological and geochemical features of thedeposit, this article discussed the ore genesis and the mineralization of Jinchanggold-nickle deposite, and made the following achievements:1. Based on the field work, petrography and EPMA research, there is3occurrence of gold in this deposit:(I) Intergranular gold, hosted between the quartzparticles as native gold,(II)lattice gold, hosted in the lattice of pyrites,(III)inclusiongold, enclosed by polybasite. Gold-bearing mineral including: native gold, pyrite,arsenopyrite, polybasite and a few gersdorffite. The occurrence of nickle in thisdeposit including:(I) independent minerals, such as Ni-As-S minerals and Ni-Sminerals,(II) enter the lattice of pyrite and other minerals as isomorphism.Nickle-bearing mineral including: pyrite, millerite, gersdorffite, ullmannite andannabergite.The mineralization process could be divided into3epochs:(I)sedi-metamorphism epoch,(II) hydrothermal ore-forming epoch,(III) exogenousepoch. The hydrothermal ore-forming stage can be divided into3stage:(a)early stagewith quartz-chrome hydromica-pyrite-arsenopyrite-millerite-gersdorffite-ullmanniteminerals combination,(b)main stage with quartz-pyrite-polybasite-native goldminerals combination,is the main gold mineralization stage,(c)late stage withcalcite-quartz-chalcedony-pyrite vein, which usually fills along the fractures.Thisthesis identified4generations of pyrite, and holds that the mineralizaition epoch ofgold and nickel are the same, the nickel mineralizaition formed in the early stage, andthe gold mineralizaition formed in the main stage.2. The research of the fluid inclusions show that the homogenizationtemperatures of ore-forming fluid varies between98.2to320.3℃, the salinity ofore-forming fluid varies between0.87%to12.07%NaCl eqv., the density ofore-forming fluid varies between0.741to1.093g cm-3. The homogenizationtemperatures falling from early stage to late stage, but the salinity variation is notobvious. The ore-forming fluid is a KCl-H2O-CO2-SO42-potassic solution in the weakreduction environment which characterized by medium-low temperature, low salinityand low density.3. Based on the trace element, REE and C-H-O-S isotopes, the ore-forming fluids sources was probably from deep metamorphic fluid and mantle fluid, meteoricwater provide partial fluid in the shallow. Gold metallogenic source has thecharacteristics of mixed sources, ultrabasic rock provided some ore-forming materials,the main metallogenic material provider was siliceous rocks in Jinchang Formation.Ni was derived from Jinchang ultrabasic rock.4. The comprehensive studies gave the conclusion that the Jinchang gold andnickle deposit is a medium-low temperature hydrothermal superimposed and modifiedgold-nickel deposit. |
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