宽频大地电磁法寻找“界面型”隐伏金矿床:以黔西南戈塘地区深部找矿为例  

Broadband magnetotelluric(BMT)detecting blind gold deposits with interface-type:A case of deep prospecting in the Getang area,southwestern Guizhou

作　　者：张伟[1,2] 曾昭光 周军[2] 季国松 徐学贵[5] 刘光磊 陆建宝 ZHANGWei;ZENG Zhaoguang;ZHOU Jun;JI Guosong;XU Xuegui;LIU Guanglei;LU Jianbao(Chengdu Center of China Geological Survey,Chengdu 610082,Sichuan,China;School of Resources and Environment,University of Electronic Science and Technology of China,Chengdu 611731,Sichuan,China;No.117 Geological Team,Guizhou Bureau of Geology and Mineral Exploration and Development,Guiyang 550018,Guizhou,China;No.102 Geological Team,Guizhou Bureau of Geology and Mineral Exploration and Development,Zunyi 563003,Guizhou,China;No.282 Team of Sichuan Nuclear Geology,Deyang 618099,Sichuan,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610082 [2]电子科技大学资源与环境学院,四川成都611731 [3]贵州省地质矿产勘查开发局117地质大队,贵州贵阳550018 [4]贵州省地质矿产勘查开发局102地质大队,贵州遵义563003 [5]四川省核工业地质局282大队,四川德阳618099

出　　处：《中国地质》2023年第2期359-375,共17页Geology in China

基　　金：中国地质调查局项目(DD20230238、DD20190033、DD20160082);国家自然科学基金项目(41804144、42230311)联合资助。

摘　　要：【研究目的】随着黔西南戈塘地区豹子洞等浅表红土型金矿开采资源的逐渐枯竭,寻找深部接替资源的任务已经十分迫切。从区域成矿规律、物化探异常、典型矿床特征等成矿预测要素出发,戈塘地区海马谷控矿断层北西侧下盘深部二叠纪茅口组、龙潭组之间的碳酸盐岩与碎屑岩Si/Ca界面上具有较大地寻找“层控型”金矿床的找矿前景。【研究方法】引入了宽频大地电磁法查明了海马谷断裂西南段0~2 km深部的电性结构特征,从电阻率反演断面图中的低阻带异常特征推断海马谷断裂具有多期活动特征,早期(中二叠世前)表现为张性正断层性质,倾向北东;后期(早三叠世后)表现为压性逆断层性质,倾向南东,倾角70°~80°。从电阻率反演断面图中的高低阻等值线梯度带推断茅口组与龙潭组存在古岩溶地貌特征,在深部存在相对“隆起”和“凹陷”变化。【研究结果】综合本区典型矿床的成矿模式、找矿标志和区域物化探异常特征,认为处于“空白”状态的海马谷断裂北西盘深部值得部署探索性钻探工程,揭示其深部的资源潜力。【结论】浅深结合的勘查技术方法(组合元素化探异常+宽频大地电磁探测技术)能够为靶区优选提供证据支撑,邻近海马谷断裂的P_(2)/P_(3)、Si/Ca界面相对“隆起”位置是开展钻探验证工作的有利位置。This paper is the result of mineral exploration engineering.[Objective]Accomplished by the gradual depletion of mineral resources of shallow laterite-type gold deposits,e.g.,Baozidong in Getang area,it is essential to detect deep alternative resources.Based on the metallogenic prediction factors such as regional metallogeny,geophysical and geochemical anomalies,and typical deposit characteristics,the Si/Ca interface between carbonatite in Permian Maokou Formation(P_(2)m)and clasolite of Longtan Formation(P_(3)l)at the footwall of the Haimagu ore controlling fault show an ideal prospect for interface-type gold deposits.[Methods]The broadband magnetotelluric(BMT)method was introduced to imagine the electrical structure of 0-2 km depth in the southwest section of the Haimagu fault.The low resistivity zones revealing by the BMT inversion imply the Haimagu fault with multi-stage activity.In the early stage(before the Middle Permian),Haimagu fault is a tensile normal fault dipping to the northeast,and is a compressive reverse fault in the late stage(after the Early Triassic),dipping to the southeast with angel of 70°-80°.According to the gradient zone of high and low resistivity zone,it is inferred that the interface between Maokou Formation and Longtan Formation features paleo-karst landform with relative uplift and depression in the deep.[Results]As for the metallogenic model,e.g.,prospecting criteria and regional geophysical and geochemical anomalies of the typical deposits in this area,it is considered that the northwest of Haimagu fault with little exploration is worth drilling the deep resource potential.[Conclusions]The combination technology of shallow and deep exploration(element geochemical anomaly and broadband magnetotelluric detection technology)can optimize to determine target areas.The relative uplifts of P_(2)/P_(3) and Si/Ca interface adjacent to the Haimagu fault are favorable for drilling verification.

关 键 词：卡林型金矿 深部找矿方法“ 界面型”隐伏矿床 宽频大地电磁法 戈塘穹窿 矿产勘查工程 黔西南 

分 类 号：P611.1[天文地球—矿床学] P622.6[天文地球—地质学]