陕西潼峪金矿床的形成机理——同生构造型金矿成矿模式探讨

OR E-FORMING MECHANISM OF THE TONGYU GOLD DEPOSIT, SHANXI——A DISCUSSION ON THE METALLOGENIC MODEL OF THE SYNTECTONIC GOLD DEPOSIT

潼峪金矿床的形成受控于区域多期变形-变质作用,与区域复背形-剪滑断裂带密切相关,成矿物质源于太华群的后期改造富集,是一同生构造型金矿床。矿床形成演化分为四阶段:Ⅰ.矿质准备阶段——初始矿源层形成;Ⅱ.矿质活化运移阶段——区域进变质一混合岩化,热力化学分异导致金活化迁移,局部初始富集;Ⅲ.矿床形成阶段——区域褶皱,形成顺层及切层剪滑断裂,在动力作用下,金分异及定向迁移而聚集成矿;Ⅳ.矿床叠加改造出露阶段——地块抬升,矿床又经断裂活动,动力机械分异作用等改造。热-动力成矿作用在矿床形成过程中具主导意义。

The Tongyu gold deposit, completely controlled by regional multideformation-metamorphism is closely related to the regional antiform and shear-slide fracture zone. The late-stage reworking of the Taihua Group accounts for the enrichment of the ore substances. It is a typical syntectonic gold deposit.The Xiao Qinling gold ore belt runs along the main antiform. The gold-quartz veins always occur in synfolding brittle-ductile shear-slide fractures, which are parallel to the beds or cross them. The gold-quartz veins are distributed in the fractured dilatent space at the edges of the early quartz veins. The mineralization was fulfiled in the thermal dynamic environment at (?)edium-deep levels.The formation and evolution of thegold deposits involve four stages. (Ⅰ) The stage of preparation of ore substances: primary source beds originated and high concentrations of gold were evenly distributed. (Ⅱ) The stage of remobilization of ore substances: Viscous and viscoplastic deformation-metamorphism and regional progressive metamorphism-migmatization were extensively developed, thus leading to remobilization mainly due to thermal action and local concentration of gold. (Ⅲ) The stage of gold deposit formation: Plastic deformation-metamorphism occurred. The region as a whole was folded under the lateral compression, thus producing concordant and cross brittle-ductile shear-slip fractures. Under the dynamic action, gold was subjected to differentiation and remobilization and thus migrated in a certain direction and concentrated to form gold deposits. (Ⅳ) The stage of superimposition, reworking and exposure of orebodies: This stage is characterized by brittle deformation-metamorphism,uplift of the terrane, faulting, reworking of shear-slip faults in the rejuvenation of inheritance nature, mechanical differentiation of materials (e.g. in relation to the grain size and gravity), infiltration of groundwater and local readjustment of materials.