Abstract:

Abstract: Ordos Basin contains concealed sandstone type uranium deposits in the lower Jurassic Zhiluo Formation. The study of the deeppenetrating geochemical methods will contribute to uranium exploration in the basin. The study shows that the collection and analysis of the clayrich microsurface soil provides a special application to regional geochemical exploration of sandstone type uranium deposit in the semiarid terrains. Pilot geochemical mapping project covering 2000 km2 around Dongsheng uranium deposit area with the sampling density of 1 sample per 4 km2，successfully delineated the clear geochemical anomalies at the redox frontier zone and the concealed deposit belts. The study of the distribution patterns of R=lnCe+lnY+lnZr+lnNb shows that the mobile forms of uranium should be the key factor causing the variation of the total content in surface soil samples. The soil sieving operation can be deemed to be the procedure of physical extraction of the deeppenetrating information for the concealed deposit. The content of uranium in the surface soil can be used as the key indexes for geochemical exploration of sandstone type uranium deposits in the basin. Due to the terrain features, the clayrich microsurface soil samples can be applied as the media for delineating the regional geochemical anomalies, but it cannot be always obtained in the exploration stage of locating the concealed orebodies. The application of the extractant of MMLU to selectively leaching the mobile forms of elements from soil along traverses over the Sunjialiang section of Dongsheng uranium deposit well delineated the U, Mo and V anomalies over the concealed orebodies.

Key words:  Ordos Basin, sandstone type uranium deposit, finegrained soil, extractant for mobile forms of elements, deeppenetrating geochemistry