Alteration characteristics and implication to uranium metallogenetic fluids of faded sandstones in Luohe Formation, Pengyang area, Ordos Basin

This paper is the result of mineral exploration engineering.

Objective The faded alteration of uranium−bearing rock series in the redbed is closely related to reductive alteration, and the analysis of the characteristics of faded alteration and its genetic fluid is of great significance for understanding the uranium ore−forming fluids and ore−forming mechanism.

Methods This study is based on analyzing the sedimentary characteristics and faded alteration characteristics of sandstones in Luohe Formation by means of core logging, element geochemical test, electron microscope scanning, electron probe analysis, XRF scanning and core infrared spectrum scanning.

Results The sandstones in the Luohe Formation are basically formed in aeolian sedimentary with oxidation conditions mineral assemblages enriched in uranium minerals, pyrite and gypsum but little trivalent iron oxides, and uranium and sulfur elements show obvious migration. Then, the redox state of sandstone and the correlation between uranium mineralization and faded alteration were discussed.

Conclusions The main body of Luohe Formation sandstone was formed in aeolian deposits under oxidation conditions, and its color, Fe₂O₃/FeO, Th/U and Cu/Zn reflect that the environment has been changed from oxidation to reduction with the increase of sandstone faded degree. The characteristics of the consistency between faded alteration and uranium mineralization in Luohe Formation in space, mineral association and redox state suggest that their genesis is related to the same reducing fluid.