Analysis of the relationship between sedimentary characteristics and uranium deposits from the Neogene Shizigou Formation in Huatugou area, Northwest Qaidam Basin

This paper is the result of mineral exploration engineering.

Objective Typical sandstone type uranium deposits are developed in Huatugou area, Northwest Qaidam Basin. The uranium reservoirs are Qigequan Formation, Shizigou Formation and Youshashan Formation, while Shizigou Formation is somewhere in between Qigequan Formation and Youshashan Formation. It is an urgent geological problem to correctly understand the relationship between sedimentary characteristics of Shizigou Formation and sandstone-type uranium deposits.

Methods In this paper, the sedimentary characteristics of Shizigou Formation are studied based on the sandstone-type uranium deposit prospecting work in the Qaidam Basin, and we analyzed the stratigraphic sequence frame, cause mechanism, provenance characteristics and their relationship with uranium ore from Shizigou Formation.

Results The colour of greywacke collected from ZK10 in Yuejin 2 area is brownish red, while the main body is calcareous argillaceous sandstone, which belongs to carbonate terrigenous clastic greywacke. Specific value of CIA=37.79-69.14, ICV=0.84-2.13, Σ=1.39-2.14, K₂O/Na₂O=0.90-1.18 (the average is 1.06), which indicated that there are relatively much more potassium feldspar or potassium minerals in the greywacke. The measuring result from a depth of 224 to 240 meter is GR=0-30 API, RT=-5-45 Ω·m. The logging facies is box type, and the amplitude of the curve is large. The measuring result of greywacke is K₂O/Al₂O₃=0.22-0.27, Ni/Co=0.34-0.53.

Conclusions The sediment environment of Shizigou Formation in Yuejin 2 area belongs to fluvial facies. The source rocks of the upper Shizigou Formation contain less clay material, and were deposited for the first time under the dry and cold paleoclimate environment. The source rock of greywacke in the Shizigou Formation were formed in the continental island arc environment, which the sedimentary source rock of the greywacke is the alkali feldspar with a small amount of felsic rocks. The sedimentary environment of the formation is very conducive for the formation of uranium deposits.