剪切带中弱应变域对赣东北金家坞金矿的控制

Control of Weak-Deformation Domain in Shear Zone on the Jinjiawu Gold Deposit,Northeastern Jiangxi

金家坞金矿受控于一条顺层脆-韧性剪切带。在脆-韧性剪切带递进变形过程中,由于构造变形分解,剪切带内形成以砂岩构造透镜体为弱应变域,以构造板岩为线性强应变带的构造透镜体型成矿系统。构造透镜体弱应变域是一个周期性的流体泵吸中心。从早至晚,构造透镜体内产生4期明显的构造-流体事件:无矿雁列石英脉阶段、无矿液压角砾岩阶段、二次变形分解及成矿阶段、成矿后的右旋斜冲挤压阶段。成矿阶段的破裂主要集中在砂岩构造透镜体中早期石英脉或液压角砾岩上,形成以碎裂石英脉及液压角砾岩为主要矿化母岩的透镜状矿体。构造透镜体系统中构造-流体作用是通过变形分解、构造泵吸、液压致裂、裂开-愈合相互有序作用而解耦的。基于对该矿床的成因及构造解析,认为金家坞金矿床属蚀变岩型金矿床,而非石英脉型金矿床,长坞坳矿段中砂岩构造透镜体是成矿流体聚积的中心,且深部会出现强应变带分布的无矿"天窗"。

Jinjiawu gold deposit is controlled by the beded brittle-ductile shear zone. With progressive deformation, the tectonic lens type ore-forming system, including the weak-deformation domain of sandy tectonic lens and the linear strong-deformation zone of tectonic slate, is formed by the tectonic deformation. The weak-deformation domains of tectonic lens are a periodic fluid pumping centre. From early to late periods in obvious tectonics-fluid events in the tectonic lens there are four stages： the barren echelon quartz veins stage, the barren hydrofracturing breccia stage, the secondary deformation partitioning and mineralization stage, and the postmineral right-lateral oblique-thrust compression stage. Fracturing of mineralization stage is found mainly concentrated in the early quartz veins or the hydrofracturing breccia in the sandy tectonic lenses, the lens-like orebody mainly consisting of the cataclastic quartz veins and hydrofracturing breccia form. The tectonic-fluid processes are decoupled by interaction of deformation partitioning, tectonic pumping, hydrofracturing and rupture-healing in tectonic lens system. Based on the genetic type and structural analysis of this deposit, it is suggested that Jinjiawu gold deposit is an alteration-type gold deposit, rather than a quartz vein type. The Changwuao ore block is the relative accumulation centre for mineralizing fluid, and barren ＂windows＂ belonging to the strong-deformation zone may appear in its deeps.