重庆彭水火石垭重晶石-萤石矿床控矿因素与成因

Ore-control factors and genesis of Huoshiya barite-fluorite deposit in Pengshui,Chongqing,China

以川东南地区重晶石-萤石成矿带中较典型的重庆彭水火石垭重晶石-萤石矿床为研究对象,对控矿因素、矿床成因进行了探讨。结果表明,地层、构造2大因素共同控制成矿。主要赋矿层位为下奥陶统分乡组和红花园组。矿区有北东向和北西向2组构造,北东向为导矿构造,北西向为布矿-容矿构造,矿体赋存于北西向压扭性断裂构造中;该矿床的矿物简单,矿石矿物为萤石和重晶石,脉石矿物以方解石和石英为主;矿石结构主要有自形、半自形、他形粒状结构等,矿石构造以块状、条带状、斑点状、团块状、角砾状等为主;蚀变以方解石化为主,蚀变程度弱。地层水及大气降水淋滤、溶解、萃取不同地层中的Ba、S、Ca、F等成矿元素后,使成矿元素富集到成矿热液中,构造和地层温压梯度致使成矿热液沿构造带上涌,厚达数百米的大湾组泥页岩将成矿热液遮挡在下奥陶统灰岩及其深部地层中,使得BaSO4和CaF2结晶、成矿。

This paper selects the Huoshiya barite fluorite deposit in Pengshui of Chongqing from the barite-fluorite metallogenic belt in the southeast of Sichuan as the object of study and discusses the ore-control factors and the genesis of the deposit. The results show that the stratum and the structure control the formation of the deposit together. The main host rocks of the deposit are Fenxiang Formation and Honghuayuan Formation of Lower Ordovician. There are two groups of structures, that is, the NE trend structure and NW trend structure. The NE trend structure is the structure as passage-way for ore fluid, and the NW trending is the ore-disfributing and ore-hosting faults. The ore body occurs in the NW compresso-shear faults. The minerals in the studied are clear. The ore minerals are fluorite and barite, and the gangue mineral is mainly calcite. The ore textures are mainly euhedral, subhedral, anhedral, etc. The ore structures are the shapes of lump, banded, punctate, agglomerate, brecciated, etc. The mineral alteration is weak and calcitization is the main kind. The ore-forming elements such as Ba, S, Ca, F are leached, resolved and extracten by precipitated water and formation water, and then concentrated in the hydrothermal fluids. The structure and the temperature and pressure gradient of strata make the fluids upwelling, but the Dawan Group shale layer with thickness of hundreds of meters, blocks the fluids upwelling and make them stand in the Lower Ordovician limestone and the deep strata, making the BaSO4 and CaF2 crystallized and mineralized in these strata.