黔西南微细粒金矿的油气成藏模式

The disseminated gold deposits in southwestern Guizhou: mineralization model and its correlation with oil-generation theories

关键词:  黔西南  微细粒金矿  油气成藏模式

Key words:  southwestern Guizhou  disseminated gold deposit  oil-generation theory

摘要:

贵州南部微细粒浸染型金矿位于扬子板块西南缘。其主要赋矿层位是二叠系—三叠系。容矿岩石为粘土岩、粉砂岩和不纯的碳酸盐岩。金矿床(点)主要分布在半局限台地相与台地边缘浅滩相鲕粒灰岩的过渡带、孤立台地边缘和盆地相浊积岩。控矿构造为背斜轴部及其倾伏端等构造应力集中的地段、层间及层内断裂或岩溶不整合面,以及与背斜相伴生、共生的断裂构造。成矿热液是沉积、成岩期中封闭的同生水(热卤水)或石油水。沉积作用阶段,为初始矿源岩形成;成岩作用阶段,像汞、锑、砷、金等活泼或较活泼的元素在压实作用和温度升高条件下,随岩石的水体一起排出而形成流体;构造作用阶段,形成背斜、断裂等容矿空间,改变了压力平衡条件,促使成矿流体运移圈闭;表生风化剥蚀作用阶段,圈闭构造受到风化剥蚀而导致含矿流体发生物理、化学变化,或其逸出地表,使矿质沉淀、聚集而成矿。

Abstract:

The disseminated gold deposits in southwestern Guizhou are hosted in the claystones,siltstones and impure carbonate rocks of the Permian to Triassic strata in the transitional zones between the semi-restricted platform and platform-margin shoal oolitic limestones,isolated platform margins and basinal turbidites.The ore-controlling structures are represented by the axes of anticlines and their plunging ends,interformational and intraformational faults or karst unconformities and the fractured structures associated with anticlines.The ore-forming flows include formation water,(hydrothermal brines) or oil-field water trapped during deposition and diagenesis.The source rocks were initiated during deposition.And during diagenesis,gold,mercury,antimony and arsenic elements were removed together with the fluids from the strata under the conditions of compression and high temperatures.Subsequent tectonic activity resulted in the generation of accommodation spaces such as anticlines and faults,variations in pressure equilibrium conditions,and migration and trapping of ore-forming fluids.The weathering and erosion of the trapped structures during epidiagenetic stages,in turn,gave rise to the physical and chemical changes of the ore-bearing fluids.Finally these fluids were concentrated and precipitated to form gold deposits.