贵州省贞丰县水银洞层控特大型金矿成矿条件与成矿模式

上世纪90年代中期通过成矿预测发现的水银洞金矿床,通过近10年的勘查,成为特大型层控金矿床。矿体呈层状、似层状产出于灰家堡背斜轴部附近300m范围内二叠统龙潭组的大孔隙度生物碎屑灰岩中,形态与背斜形态一致。矿体严格受控于碳酸盐岩,顶板和底板皆为粘土岩或粉砂质粘土岩,界线清楚。矿化表现为“硅化、白云石化、黄铁矿化”组合。硅化与白云石化是成矿的先决条件,碳酸盐岩最终能否成矿及品位的高低,取决于是否具有黄铁矿化热液蚀变及其强度。矿床具矿体多、厚度薄、品位富的特点。单矿体即达中型矿床规模。具中—低温超高压热液成矿的特点。金赋存于沿自形黄铁矿内核生长成的含砷黄铁矿环带中。

Metallogenic conditions and model of the superlarge Shuiyindong stratabound gold deposit in Zhenfeng County, Guizhou Province

The Shuiyindong gold deposit was found in the middle 1990s and has now become a superlarge stratabound gold deposit through nearly ten years of exploration. The orebodies occur in the stratified or stratoid shape in high-porosity bioclastic limestone of the Upper Permian Longtan Formation within 300 m near the axis of the Huijiabao Anticline. The shape of the orebodies is similar with that of the anticline. They are strictly controlled by carbonate rocks, and both their hanging wall and footwall consist of claystone or silty claystone, with clear-cut boundaries. The gold mineralization is represented by the association of silicification, dolomitization and pyritization. Silicification and dolomitization are metallogenic preconditions. The possibility of carbonate mineralization and gold grade of ores depend on the hydrothermal alteration of pyrite and its alteration intensity. The deposit is characterized by the large number of orebodies, small thickness and high grade, and a single orebody may reach a medium-sized deposit scale. This deposit has the features of medium- and low-temperature, ultrahigh-pressure hydrothermal mineralization. Gold is hosted by arsenic-bearing pyrite zones growing along the cores of idiomorphic pyrite.