广西乐业林旺金矿床构造解析及构造成矿作用

Structure Analysis and Structural Metallogenesis of the Linwang Gold Deposit,Leye,Guangxi,China

详细的构造解析表明,矿床构造线主要分为南北向、北东东向和北西向三组,其中造山期间形成的南北向构造线(不对称褶皱和逆冲断层)控制了矿床的基本构造格架。后碰撞造山侧向挤压期间构造应力场发生近直交的改变,一方面使造山期形成的褶皱发生重褶,形成走向北东东的叠加褶皱;另一方面导致F1的左旋-正滑运动,矿液沿着断层拉张的空间沉淀就位。矿床构造演化至少经历了同生期裂陷、造山期挤压和后碰撞造山侧向挤压等三个阶段,成矿发生在后碰撞造山侧向挤压阶段。层状矿体主要赋存于背斜构造中,在空间上与赋存于断层中的脉状矿体相连。能干性和渗透性明显不同的地层组合是形成层状矿体的岩性基础,断裂构造则是主要控制因素。泥质不透水层分别与反冲断层、背斜构造组成的构造圈闭,以及两期非共轴背斜叠加形成的构造高点则是形成厚大矿体的主要原因。林旺金矿在烂泥沟金矿与水银洞金矿之间形成了一个从脉状型式→脉状和层状之复合型式→层状型式的完整矿床型式系列。这种复合矿床型式直观地表明了层状矿体是后生热液成因矿床。

The Linwang gold deposit,which is located in Leye county of Guangxi Zhuang Autonomous Region,is one of newly discovered middle-scale Carlin-type gold deposits in Yunnan-Guizhou-Guangxi triangle area in southwestern China.It consists of stratabound and fault-controlled orebodies.Detailed structural analysis shows that the structural lines of the deposit can be classified into three groups,i.e.,north-south trend,northeast trend and northwest trend,among which,north-south trend structural line（asymmetric folds and thrusts formed in collision stage） controls the structural framework of the deposit.The compression direction of structural stress field changed perpendicularly in the post-collision stage,as evidenced by the refolding of the north-south trend folds,which were generated in collision stage,into northeast-east strike superimposed folds and the formation of F1 sinistral-normal slipping fault.Ore-formng fluids flew into extension parts and deposited gold.At least three structural deformation stages can be discerned in the deposit,i.e.,syngenetic splitting,collisonal compressing,and postcollision lateral extrusing.The gold mineralization occurred mainly at the postcollisional lateral extrusion stage.Stratiform orebodies are mainly hosted in the cores of anticlines,and spatially associate with the vein orebodies hosted in faults.Strata association of distinctly different competence and permeability is the lithologic basic to form stratiform orebodies,fracture is the dominating factors.The structural traps which composed by argillaceous impermeable barrier and recoil thrust or anticline,and the structural culmination formed by superimposition of different stage non-coaxial anticlines are the main locus to host thick orebodies.The Linwang gold deposit,located between the Lannigou gold deposit and the Shuiyindong gold deposit,and the three deposits form a complete deposit pattern series from vein→compound of vein and stratiform → stratiform pattern.The compound pattern suggests that the stratiform orebodies are of epigenetic hydrothermal.