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

doi:10.11720/wtyht.2019.0261

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Abstract

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 authors' 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 western 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 optimization 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.

Key words： natural field audio magnetotellurics resistivity Vientiane basin of Laos Carnallite deposit Tagong Formation of Paleogene

Received: 10 May 2019 Published: 28 November 2019

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	Articles by authors
	Zi-Chuan ZHU
	Dan ZHOU
	De-Wen LI
	Run-Long YU

Cite this article:

Zi-Chuan ZHU,Dan ZHOU,De-Wen LI, et al. The application of natural field audio magnetotellurics sounding to the exploration of the Vientiane basin potassium salt deposit in Laos[J]. Geophysical and Geochemical Exploration, 2019, 43(6): 1268-1276.

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https://www.wutanyuhuatan.com/EN/10.11720/wtyht.2019.0261 OR https://www.wutanyuhuatan.com/EN/Y2019/V43/I6/1268

Geologic structure of Vientiane basin
1—middle Permian; 2—middle-lower Jurassic; 3—lower Cretaceous; 4—tagong formation; 5—bantabo formation; 6—Cretaceous monzonite granite-porphyry; 7—angular unconformity; 8—parallel unconformity; 9—conformity boundary; 10—fault of unknown property ; 11—nucleation fault; 12—concealed fault; 13—anticline and their numbers; 14—syncline and their numbers

Location of AMT line and gravity anomaly of nearby area
1—gravity anomaly contour of negative value; 2—gravity anomaly contour of positive value; 3—contour of zero; 4—inference fault; 5—profile of AMT; 6—drilling of finished

The average resistivity of Tagong formation stratum by electric logging(Ω·m)

Four channels E field time series of two equipment

Four channels H field time series of two equipment

resistivity and phase curve of some site

Two ADU's apparent resistivity and phase curve comparison in same site

2D inversion result of L1、L2 and L3

AMT inversion result and gravity anomaly of L3

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