河南省罗山县皇城山银矿床矿化特征和成矿作用

Mineralization characteristics and genesis of Huangchengshan silver deposit in Luoshan county, Henan province

皇城山银矿床成矿作用经历了热液期和表生氧化期。热液期经历了三个成矿阶段:黄铁矿-硅化阶段、多金属硫化物-硅化阶段和角砾岩化阶段。主成矿阶段为多金属硫化物-硅化阶段,热液作用表现为早期石英在碱性热液作用下溶解和金属硫化物沉淀,随后的温度降低和循环地下水的加入最终SiO2因过饱和而沉淀。成矿物理化学条件为低温、低盐度的酸性环境;矿化程度与火山岩的酸性程度成正比。矿床具以强硅化带为中心向外依次发育高级泥化带(高岭石+石英)和泥化带(蒙脱石+石英)的蚀变分带,与矿化有关的为中期硅化,银及多金属硫化物矿化限于强硅化蚀变带内。从矿石矿物的组合、标型、组构及矿床蚀变分带特征判断,皇城山银矿床具有浅成低温热液矿床中的高硫型矿床典型特征,属高硫型浅成低温热液矿床。

The mineralization of Huangchengshan silver deposit experienced hydrothermal and supergenetic oxidation period. The hydrothermal stage had gone through three mineralization stages： the pyrite-quartzite stage polymetallic sulphides-quartzite stage and brecciation stage. The main mineralization stage is polyrnetallic sulphides-quartzite stage. Hydrothermalism showed that early quartz dissolved in alkaline hydrothermal process and precipitated with metal sulfides. With the following of decreased temperature and circulating groundwater, finally, Si02 precipitated because of super-saturation. It has low temperature and low salinity in acidic environment for ore-forming physicochemical conditions; the degree of mineralization is proportional to acidity of volcanics. The deposit has alteration zoning centered in strong silicification outward with development of advanced muddy zone （kaolinite and quartz） and muddy zone （montmorillonite and quartz）. It is limited to the the alteration zoning of strong silicification that middle silicification related to the mineralization of silver and polymetallic sulphides. It can be judged that Huangchengshan silver deposit has the typical high-sulfur characteristics of epithermal deposits, which is a high sulfur epithermal deposit, from the combination, typomorphic characteristics and fabric of the ore minerals and deposit alteration zoning characteristics.