甘肃天水夏家坪金矿地质特征

Geology and controls on the Xiajiaping gold deposits in Tianshui,Gansu

夏家坪金矿位于西秦岭反"S"弧形构造东段Au-Ag-Cu-Fe-Pb-Zn成矿带中,矿体产出受下古生界李子园群沉积-火山岩系控制。矿体多呈带状、透镜状产出,具收缩膨大、尖灭再现及分支复合特征。容矿岩石主要为变砂(泥)岩、破碎石英脉、硅化角砾岩等。矿石类型以构造蚀变岩型为主,局部为石英脉型。围岩蚀变具分带性,矿化可分为早期的金和晚期的银铅锌两个主要成矿阶段。

The present paper deals with the geological background,geological characteristics and ore-controlling factors of the Xiajiaping gold deposits in Tianshui,Gansu.The Xiajiaping gold deposits is hosted in the Au-Ag-Cu-Fe-Pb-Zn metallogenic belt in the eastern part of the western Qinling reversed ＂S＂-type arcuate structures,and controlled by the meta-clastic rocks and carbonate formation in the Lower Palaeozoic Liziyuan Group sedimentary-volcanic rock series,and associated secondary brittle and brittle-ductile fracture zones.Spatially,the ore bodies tend to occur in strip-shaped and lenticular forms characteristic of expansion,contraction,branching,combination and discontinuity.The host rocks consist of meta-sandstone,meta-mudstone,cataclastic quartz veins and silicified breccias.The ore types are dominated by tectonically altered rocks,locally with quartz vein type and oxidized ores near the surface.In addition,the Ag,Pb and Zn mineralization are also well-developed,indicating a polymetallic sulfide type.The alteration and mineralization generally become weak and simple from the mineralization center outwards.The wall-rock alteration exhibits the zoning patterns.The mineralization can be classified into two main stages： early Au mineralization and late Ag,Pb and Zn mineralization.