贵州晴隆锑矿床复式半地堑-盆地流体的成矿耦合关系研究

Study on Metallogenic Coupling of Compound Half-graben and Basin Fluid in the Qinglong Antimony Deposit

贵州省晴隆锑矿床位于南盘江-右江盆地,是我国重要的锑矿床之一。本次研究将大地电磁测深、矿田构造和火山岩相学等资料密切结合,查明晴隆锑矿床位于复式半地堑构造中。大地电磁测深揭示青山镇断层已延深至盆地基底,该断层还控制火山岩相,是复式半地堑的边界断层和控制断层。地质填图和钻探资料揭示晴隆锑矿床存在一个古隆起——大厂古隆起,晴隆锑矿床即分布于古隆起之上。北东向二级断层为控矿断层,填图发现这些断层卷入地层少,虽未错断龙潭组地层,但在断层上方龙潭组可见砂岩流卷构造和大面积剪节理,也具有同生断层的性质。地球化学数据和新近在晴隆锑矿区发现的古油藏表明,盆地流体是晴隆锑矿床成矿流体的重要来源。东吴不整合面是黔西南地区成矿流体侧向运移的通道,在该不整合面上形成了面积巨大(2000 km2)的蚀变体——大厂层,是黔西南地区锑金矿的重要赋存层位,古隆起则是成矿流体运移的指向。青山镇断层是来自盆地深部或者下伏基底成矿流体运移的通道,而北东向二级断层则是将侧向运移的成矿流体输导至有利部位的关键。晴隆锑矿床复式半地堑控矿构造研究对该地区接替资源勘查具有重要的指导意义。

The Qinglong antimony deposit is an important kind of antimony mineralization in China, which is located in southwestern Guizhou. Magnetotelluric Sounding （MT）, ore field structure, and lithofacies studies suggest that the Qinglong antimony deposit occurs in a half-graben and ramp sag. MT survey demonstrates that the Qingshanzhen fault extends into the basement of the Nanpaniang-Youjiang sedimentary basin and controlled the volcanic facies in the Qinglong antimony deposit. Moreover, this fault zone may also be a boundary fault or a key fault for the Dachang half-garben. Drilling and mapping revealed a paleo-apophysis above which occur the antimony ore bodies in the Qinglong Sb deposit. The secondary NE-striking faults, which cut only the topper of the Maokou Formation, the Dachang Layer, and lower Emeishan Basalt, control the ore deposits. Sandstone flow rolls and shear joints are found in the Longtan Formation at the surface, indicating the NE-striking faults might be a growth fault. Geochemical data and the new finding of paleo oil-pool in the Qinglong antimony district suggest that ore-forming fluid was mainly derived from basin fluid. The Dongwu unconformity acted as a lateral migration pathway for the ore-forming fluid. The Dachang Layer was formed above the unconformity interface within which many Carlin-type gold deposits and antimony deposits developed. The Qingshanzhen fault acted as a vertical migration conduit for the ore-forming fluid which derived from the depth of the basin or basin-basements. The Dachang paleo-apophysis is the destination for the ore-forming fluid, and hosts the antimony orebodies. The secondary NE-striking faults are believed to be the key or the last vertical conduits to transfer the ore-forming fluid to the favorable location. The recognization of the half-graben is important for the future resource exploration in the Qinglong antimony district.