中国南天山萨恨托亥-大山口成矿带韧性剪切带与金成矿作用

以南天山中段萨恨托亥-大山口成矿带内控矿韧性剪切带为例,对韧性剪切带的金成矿作用进行了初步探讨.通过对地质体的构造变形特点、变形演化过程的分析表明,韧性剪切带的构造属性控制了金矿的产状及规模,金矿化阶段与韧性剪切带的变形演化过程密切相关.矿化类型、矿化强度及矿化方式受韧性剪切带发展阶段制约,剪切带内物质组分迁移变化揭示出韧性剪切带与金在剪切带内的迁移富集、沉淀成矿的内在联系.韧性剪切带成矿作用是南天山成矿带中段重要的金矿成矿作用.

DUCTILE SHEAR ZONE AND GOLD METALLIZATION IN THE SAHENTUOHAI-DASHANKOU METALLOGENIC BELT, SOUTHERN TIANSHAN, CHINA

The Dashankou and Sahentuohai ductile shear zones,in which gold deposits occur,present the characteristic of ductile and brittle deformation The ductile shear zones are strongly schistosed belts with several kinds of foliation well developed The grain size of rocks and minerals reduces,and the fabrics change in the ductile shear zones There are many kinds of mesoscopic structures in the shear zones such as rotated boudinage,kink band,asymmetic fold,fractures,tectonic lens and shear crack,which provide space for auriferous fluid precipitation The geometric characters of the structure in the shear zone decide the shape and orientation of orebodies within it Auriferous mylonite with disseminated ore is formed at high temperatures in the stage of plastic deformation Gold bearing quartz network is formed during the transformation from ductile to brittle deformation In the brittle deformation stage,gold orebodies are mainly in quartz veins The homogenization temperatures of quartz fluid inclusions in all kinds of ores in the shear zones show that the temperatures at which auriferous mylonite and quartz vein formed are continous and that the gold metellogenis is a continuum from the stage of mylonite to that of quartz vein The mineralization is infiltration metasomatism in the earlier stage and infilling in latter There are obvious changes in compositions of the rocks from the wallrock to the strongly deformed rock in the shear zones The contents of FeO,MgO,SiO 2,Fe 2O 3,SO 3,Au,As,Cu,Sb,Bi and Ag increase but that of CaO decreases form the margin to the core of the shear zones The components that increase strongly in auriferous mylonite are MgO,SO 3,SiO 2,FeO and Fe 2O 3 The changes of compositions in the rocks within the shear zones indicate that the shear deformation results in a deal of moving fluid The mineral assemblage becomes simple in strong deformation belt as quartz sericite ferrodolomite(calcite) The main mineral alteration in the rocks are silicification,sericitation and ferrodolomitization(calcitization) The occurance of quartz pyrite bearing mylonite is due to the moving in of FeO,SiO 2,Fe 2O 3 and SO 3 to strong deformation belt The silicon rich solution containing amount of metallogenic elements such as Cu,As,Au,Sb,Bi and Ag becomes mineralization fluid The SiO 2 precipitation is accompanied by the separating out of gold from the fluid during the shear zone developing The shear crack,fracture and other brittle structures become ore controlling structure Mylonite and shear deformation in splitting,pressolution and plastic deforming play an important role in the activation,movement and enrichment of gold The ductile shear deformation and demetamorphism is an important mechanism for the formation of auriferous fluid The gold deposits in Dashankou Sahentuohai metellogenic province have a close relation to the ductile brittle shear zones spatially,temporally and genetically