脉状矿体与似层状矿体的构造成因——以广西大福楼大型锡多金属矿床为例

Structural genesis of vein orebody and stratoid orebody:An example of Dafulou large-scale tin polymetallic deposit in Guangxi

近年来勘探工作发现,单个矿床存在“上脉下层”的空间分布形式,即上部为陡倾斜的脉状矿体和下部为与地层产状一致的似层状矿体共存。为了探讨脉状矿体与似层状矿体的构造成因,以广西大福楼大型锡多金属矿床为例,结合两类矿体的特征和构造分析,认为脉状矿体受形成于脆韧性剪切环境中的裂隙控制,从早至晚经历了剪性雁列脉、张性桥、脉贯通、含矿溶液充填四个构造阶段;似层状矿体则受控于NW向复式背斜层间裂隙,其形成经历了层间滑动、水扩溶、褶皱-断裂和含矿溶液充填四个构造阶段。成矿构造形成于印支期,其中层间裂隙形成于印支期层滑-褶皱构造体系中的早期破裂,而陡倾斜裂隙形成于层滑-褶皱构造体系中的中期破裂,两类矿体的成矿时代为燕山晚期。

Exploration work in recent years has found that there is a spatial distribution form of"upper vein and lower layer"in a single deposit.That is to say,the upper part is a steeply dipping vein orebody and the lower part is a stratoid orebody consistent with the occurrence of the strata.In order to explore for the structural genesis of vein orebody and stratoid orebody,Dafulou large-scale tin polymetallic deposit in Guangxi is take as an example.Based on the characteristics and structural analysis of the two kinds of orebodies,it is considered that the vein orebody is controlled by the fractures formed in the brittle-ductile shear environment,and it has experienced four structural stages from early to late,shear echelon vein,tensile bridge,vein penetration and ore bearing solution filling.The stratoid orebody is controlled by the interlayer fissures of the NW trending complex anticline.Its formation has also experienced four structural stages,interlayer sliding,water expansion,fold-fracture and ore bearing solution filling.The metallogenic structure is formed in the Indosinian period,in which the interlayer fissures are formed in the early fracture of the layer-slip-fold structural system in the Indosinian period,while the steeply dipping fissures are formed in the middle-stage fracture of the layer-slip-fold structural system.The metallogenic age of the two type orebodies is the late Yanshan period.