综合地球物理勘探方法在安徽范水洼地区金矿找矿中的应用

滁州范水洼地区是皖东重要的铜金矿找矿远景区,微细浸染型金矿是其重要的金矿成矿类型。前人在综合电磁方法解释和推断方面的工作较为薄弱,为了在该区实现找矿突破,在与范水洼矿区主要构造的垂直方向上布设综合物探地质剖面,包括重磁、音频电磁测深、可控源音频大地电磁法和时间域激发极化法,研究结果表明: ①范水洼矿区西侧黄破断裂上部较陡,在深度约500 m处变缓,而后在深度1 500 m处又转变为陡倾; ②矿区深部存在两处较为明显的隐伏断层,倾向南东,倾角70°~75°。两隐伏断层之间可能存在隐伏岩体,该隐伏岩体埋深较浅(400~500 m)。而后在成矿有利部位施工了1个1 500 m的直孔钻探工程,结果表明黄铁矿化强烈的构造角砾岩是该区微细浸染型金矿的主要赋矿位置。但因地层中碳质成分的影响,通过极化率寻找该成矿有利部位效果不佳,宜通过寻找电阻率梯度带,进而推断断裂构造发育的位置,再圈定有利于成矿的构造破碎带。通过结合该区的岩石物性结构、成矿地质特征以及控矿地质条件,解译了矿区深部构造地质特征,明确了找矿有利块段,为下一步金矿找矿工作指明了方向。

Application of comprehensive geophysical methods in gold deposits prospecting in Fanshuiwa area of Anhui Province

Fanshuiwa district in Chuzhou is an important prospecting area for copper and gold deposits in Eastern Anhui Province, and the fine-disseminated gold deposit is the major type. Previous work on the interpretation and inference of comprehensive electromagnetic methods is relatively weak. Therefore, a comprehensive detection profile on the vertical direction of the main structures was set up, including magnetic, gravity, AMT, CSAMT and TDIP, in order to achieve a breakthrough in prospecting in this area. The results show that ① Huangpo fault, on the west side of the Fanshuiwa mining area, has a steeper upper part. This fault slows down at a depth of approximate 500 m and changes to a steep dip at a depth of 1 500 m. ② There are two obvious hidden faults in the deep, with a southeast tendency and the dip of 70°~75°. One intrusive rock probably locates between these two faults, with a shallow buried depth of 400~500 m. A 1 500 m straight hole drilling project was constructed in the favorable mineralization position, and the results show that the structural breccia with strong pyrite mineralization is the main ore-bearing location of the fine disseminated gold deposits in this area. However, due to the influence of the carbon content in the strata, it is not effective to find the favorable mineralization site by polarizability. It is advisable to find the resistivity gradient zone first, and infer the locations with the fractured structure. The structural fracture zone favorable for mineralization was delineated lastly. Combined with the rock physical structure, ore-forming geological characteristics and ore-controlling geological conditions, the deep tectonic features of this mining area were inferred and favorable blocks for prospecting were clarified in this paper, which could point the prospecting direction for golden deposits in this area.