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Geology And Ore-forming Fluids Geochemistry Of The Huanxiangwa Gold Deposit In Western Henan Province

Posted on:2016-12-28Degree:MasterType:Thesis
Country:ChinaCandidate:X W ZhangFull Text:PDF
GTID:2180330461492721Subject:Mineral prospecting and exploration
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The Huanxiangwa gold deposit in western Henan province is one of the most representative combined gold deposits of alteration rock type with quartz vein type in the Xiaoqinling-Xiongershan gold deposit concentration area. This deposit is excellent in ore-forming condition and lager in potential for ore prospecting. The field investigation and laboratory analysis have been carried out on the deposit so as to ascertain its geological characteristics and ore-forming fluid geochemical features. Mineralization process of the deposit has been discussed based on the obtained geological and geochemical data.Based on metal sulfite type in ores as well as their mineral assemblage and texture and structure, ores in the deposit can be divided into two types of alteration rock and quartz vein. The ores of the alteration rock type have metasomatic textures, and consist of K-feldspar, pyrite, quartz, and sericite. In contrast, the ores of the quartz vein type are characterized by hydrothermal filling textures, and include quartz and pyrite.The field investigation and microscopic observation indicate that the alteration and mineralization zoning of the Huanxiangwa gold deposit is obvious, occurring pyritized-phyllite, pyrite-potassic and siliceous alteration, propylitization, and fresh andesite zones from the ore body outward. According to the crosscutting relationships of the veinlets and the mineral assemblages, the alteration and mineralization process can be divided into hydrothermal and supergenic periods, the former of which can be further divided into five stages as follows: K-feldspar alteration, quartz-pyrite, quartz-polymetallic sulfides, fluorite-polymetallic sulfides, and carbonate stages. The quartz-pyrite stage is a secondary mineralization stage for the formation of the quartz vein type ores, while the quartz-polymetallic sulfides stage is the most important mineralization stage for the formation of the alteration rock type ores.The microscopic observation shows that fluid inclusions within minerals in the deposit include Na Cl-H2 O, CO2-bearing, and daughter mineral-bearing multiphase inclusions. The compositional analyses for fluid inclusions support the derivation of ore-forming fluids from volatile-Na Cl-H2 O and Na Cl-H2 O systems. Gradual decreasing of salinity with temperature and δ18O with δ D of ore-forming fluids occurred from the early K-feldspar stage to the late carbonate stage, indicating gradual increasing of meteoric water in the ore-forming fluids.The obtained ore deposit geological and fluid geochemical data are consistent with the initial enrichment of gold in ore-forming fluids by cooling with temperature decreasing, and the precipitation of gold from the ore-forming fluids for the formation of the different types of ores by CO2 degassing in the quartz-pyrite stage, by water-rock interaction in the quartz-polymetallic sulfides stage, and by fluid immiscibility in the fluorite-polymetallic sulfides stage.
Keywords/Search Tags:Ore deposit geology, ore-forming fluid geochemistry, fluid inclusions, combined gold deposit of alteration rock type with quartz vein type, Huanxiangwa in western Henan province
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