音频大地电磁测深法在老挝万象盆地钾镁盐矿产勘探中的运用效果  

The application of natural field audio magnetotellurics sounding to the exploration of the Vientiane basin potassium salt deposit in Laos

作　　者：朱自串 周丹 李德文 余润龙 ZHU Zi-Chuan;ZHOU Dan;LI De-Wen;YU Run-Long(Beijing Dachuang High Tech Science&Technology Co.,Ltd..,Beijing 102445,China)

机构地区：[1]北京达创高科科技有限公司，北京102445

出　　处：《物探与化探》2019年第6期1268-1276,共9页Geophysical and Geochemical Exploration

摘　　要：老挝万象盆地位于呵叻盆地北缘,呵叻盆地钾盐矿是世界上最大的固体钾盐矿床之一,矿体以厚层状光卤石为主,局部伴有薄层钾石盐矿体。在万象盆地东北部某矿区内完成了3条音频大地电磁测深(AMT)剖面,剖面二维反演结果直观反映了塔贡组盐岩层起伏及构造分布情况,L2线西部、L3线中西部似球状高阻凸起,钻孔揭露为盐岩层隆起区,盐岩层埋深变浅、厚度增大,隆起区两侧构造发育,AMT二维反演结果模型基本反映出盐隆起全貌;L1线钻孔揭露的盐岩层顶板埋深与二维电性模型推断结果吻合度高。总之,通过与剖面附近钻孔及已有地质、物探成果资料对比,说明AMT所得二维电性模型反映的盐岩层赋存状态、构造发育部位基本可靠,因此通过AMT反演结果反映的盐岩层、构造特征可为找矿靶区优选、钻孔选址、成矿研究提供依据,对今后呵叻盆地钾盐矿产勘查物探方法选取也有积极的参考意义。Located on the north margin of Nakhon?Khorat basin,the Vientiane Basin of Laos has one of the largest solid potash deposits in the world.The main orebody is closely related to thick?bedded Carnallite,and locally associated with thin?bedded potassium.The au?thors'company has completed 3 AMT profiles in a mining area in northeastern Vientiane Basin.The 2D inversion results reflect directly the fluctuation of salt beds in Tagong Formation and the distribution of structures.The spherical high?resistivity uplifts exist in the west?ern part of Line L2 and the central and western part of Line L3.Drilling detected the spherical high?resistivity uplift as the salt bed with salt layer becoming shallower and its thickness becoming larger.The structures on both sides of the uplift area are well developed.AMT 2D inversion model basically reflects the salt layer uplift completely.The roof burial depth of salt rock exposed by L1 line boreholes is in good agreement with the result of two?dimensional electrical model inference.In a word,through the comparison between the AMT 2D inversion models and the data of boreholes near the profiles as well as the results of geological and geophysical prospecting,it is shown that the 2D electrical model obtained by AMT reflects the occurrence state of salt beds and the location of structural development.Therefore,the characteristics of salt beds and the structures reflected by AMT inversion models can provide the evidence for the optimi?zation of prospecting target areas,selection of drilling sites and the metallogenic research.The results obtained by the authors provide a positive reference for the selection of geophysical methods for potash mineral exploration in the future.

关 键 词：音频大地电磁测深 视电阻率 万象盆地 光卤石矿床 古近系塔贡组 

分 类 号：P631[天文地球—地质矿产勘探]