黔西南泥堡特大型金矿床的新发现及其控矿因素

New Discovery and Ore-Controlling Factors of the Large Scale Nibao Gold Deposit in Southwestern Guizhou Province

为了在黔西南泥堡金矿区获得找矿突破,进一步厘清矿床控矿因素,近年来,贵州省地质矿产勘查开发局一〇五地质大队根据其积累的黔西南地区金矿找矿经验建立了区域成矿模式,结合该区地表已知金矿体赋存特征,通过对以往大量地质资料再研究,并通过大量深部钻探工程验证,获得了一些新发现:二龙抢宝背斜是一次级褶皱,为隐伏的F1断层上盘的牵引褶皱;新发现了F1断层破碎蚀变带中的厚大金矿体,单矿体达大型矿床规模,从而使泥堡金矿达特大型矿床规模,并新发现了深部泥堡背斜核部的层控型矿体;在黔西南地区,首次在泥堡金矿区中二叠统茅口组中的断层破碎带内发现了金矿体。进一步研究得出泥堡金矿床的控矿因素是:1地层,泥堡金矿体主要产于中二叠统茅口组,上二叠统龙潭组一段、二段和三段;2构造,泥堡金矿体产于泥堡背斜南翼,主要受F1逆断层控制,其次受二龙抢宝背斜核部附近的构造蚀变体控制;3岩性,当岩石为角砾岩或砾屑砂岩、沉凝灰岩、不纯碳酸盐岩时有利于成矿,特别是岩层厚度较薄,成分复杂,孔隙多,其顶、底板为透水性差的黏土岩、粉砂质黏土岩时易富集形成金矿(化)体。

In order to get a prospecting breakthrough of Nibao gold deposit and further clarify the ore-con- trolling factors, 105 Geological Brigade of Guizhou Bureau of Geology and Mineral Resources has recently restudied a large number of geological data and previous researches and confirmed the previous study re- sults and experiences by many deep drillings. Some new discoveries have been made according to its accu- mulation a regional metallogenic model of gold deposit established based on the previous studies in south- western Guizhou Province and the known geological characteristics of gold orebodies. The results show that the Erlong-Qiangbao anticline is a drag fold subsidiary to the hidden hanging wall of the F1 fault. Based on a large number of drills, thick Au ore layers with individual up to large-scale and stratiform Au ores have been found in the fractured alteration zone of F1 and in the core of the Nibao anticline at depth, respectively. Because of the addition of fault-type ores, the Nibao Au deposit reaches a giant scale. Moreo- ver, it is the first time that Au ores are discovered in the Middle Permian Maokou Formation in the mining area of Nibao in southwestern Guizhou. Further studies have concluded that the Nibao deposit is mainly hosted in the Middle Permian Maokou Formation and the 1-3 sections of the Upper Permian Longtan For- mation in the southern flank of the Nibao anticline, and the ores are controlled mainly by the F1 thrust fault, and secondarily by the structural alteration body nearby the core of the Erlong-Qiangbao anticline. Au mineralization is generally hosted in strata like breccias, gravel sandstones, sedimentary turfs, and im- pure carbonates especially when these rocks are thin in thickness, complicate in composition, porous with the roof and floor of impermeable clay rocks and siltstones.