可控源音频大地电磁法在个旧西区深部地质结构探测中的应用

The Application of Controlled Source Audiomagnetotellurics to Detect Deep Geological Structures in Western Gejiu

个旧西区具有与个旧东区相似的成矿地质条件,是近年来找矿工作的重点。为了研究个旧西区深部地质结构,采用可控源音频大地电磁法(controlled source audiomagnetotellurics,CSAMT),选择在个旧东区典型矿段(卡房)开展长600 m,共12测点的过井试验剖面测量,探讨了在该地区使用CSAMT法的有效性,同时完成个旧西区长21 km,共420测点的CSAMT剖面测量。基于地层岩石物性特征及过井剖面电阻率反演结果,成功划分出2 km以深范围内地层组间界面以及岩体顶面接触结构。结果显示:以316测点为界,南北电阻率迥异,北部为高阻,主要为花岗岩分布区,南部为低阻,主要为沉积岩分布区;识别出F 1、F 2、F 3共3条断裂,揭露了地下构造的形态特征;桥顶山凸起的3处岩凹与南侧的岩兜、者勒白凸起南缘的岩兜、贾沙河海拔750~0 m处的个旧组地层捕虏体是成矿的有利部位,可优先布设相关验证工作;水塘寨下方深埋的花岗岩凸起和个旧组地层接触部位,显示良好的找矿远景,是寻求找矿突破的关键。可见,CSAMT法是该区深部地质信息探测的一种行之有效的方法。

The western Gejiu has the similar ore-forming geological conditions with the eastern Gejiu,which is the focus of mineral explorations in recent years.In order to study the deep geological structure,the method of controlled source audio-magneto-tellurics(CSAMT)was adopted.The research aimed to carry out the cross drilling test profile survey with a length of 600 m and 12 points in the typical ore profile(Kafang)of Gejiu east area,and the effectiveness of CSAMT method was discussed.At the same time,the CSAMT profile with a length of 21 km and 420 points was completed.Based on physical properties of stratum rocks and cross drilling resistivity inversion results,the stratum boundary and the top contact structures of rock mass in the deep area of 2 km were successfully divided.The results show that Point 316 is taken as the boundary.The resistivity is very different,the north is high resistivity,which is the granite distribution area,and the south is low resistivity,which is the sedimentary rock distribution area.Three faults of F 1,F 2 and F 3 are identified,which reveal the morphological characteristics of underground structure.Three rock depressions of Qiaodingshan uplift and the rock pockets at the south side,the rock pockets of Zalebai uplift,and the Gejiu stratum xenoliths at the altitude of 750~0 m in Jiashahe,are the favorable parts for mineralization,and relevant verification work can be given priority.The contact parts of the deep buried granite uplift and the Gejiu stratum under Shuitangzhai show good prospects.It is the key to seek a breakthrough in prospecting.It can be seen that CSAMT method is an effective method for deep geological information exploration in this area.