甘肃北山南带韧性剪切带型金矿床构造控矿解析

Analysis of Ore-controlling Structure in Ductile Shear Zone Type Gold Deposits in Southern Beishan Area, Gansu Province

通过研究不同层次的韧性剪切带与金矿化的关系及含金裂隙类型 ,结合地质地球化学和磁组构分析 ,探讨了韧性剪切带对金矿化的控制作用。认为韧性剪切带的控矿作用表现为在区域上控制金矿床 (点 )的分布 ,在矿床范围内 ,它既是唯一的赋 (含 )矿构造 ,也控制着矿化带和矿体的形态、产状、规模和分布 ,在矿床成因上决定了金矿化以蚀变糜棱岩型为主 ,同时韧性剪切变形及其形成的动力变质热液是金矿成矿流体的来源之一。

The ductile shear zone type gold deposits are a kind of deposits whose ore_forming mechanism and ore_controlling factors are closely related to the ductile shear zone and its evolution. Ductile shear zones are well developed in southern Beishan area. Based on the studies of the relationship between the ductile shear zone and the gold mineralization as well as the type of Au_bearing fracture system, combined with an analysis of geology and geochemistry and magnetic fabric, this paper has dealt with the controlling role of the ductile shear zone over the gold deposits. The authors have reached the following understanding: (1) The regional distribution of gold deposits (and gold spots) is controlled by the ductile shear zone. (2) The ductile_brittle shear zone is the only ore_bearing structure which controls the shape, attitude, size and distribution of ore_forming zones and orebodies. (3) The mechanical property of the compression_shear ductile deformation leads to the results that the main kind of gold mineralization is of altered mylonite type and that the main alteration is metasomatism. (4) Dynamic differentiation and dynamic metamorphic hydrothermal solution produced by ductile deformation seem to be one of the sources of ore_forming fluids for gold mineralization. The above understanding is identical to the conclusion drawn from fluid inclusions and geochemical characteristics of the deposits that ore_forming minerals are mainly derived from metamorphic rocks and ore_forming fluids are mainly composed of metamorphic water.