Uranium-series disequilibrium as a tool for tracing uranium accumulation zone in altered granite rocks

Abu Garadi area is mainly represented by metasediments, alkali feldspar granites and stream sediments. The granitic mass described different degrees of hydrothermal alterations like albitization, greisenisation, hematitisation, silicification and koalinitisation which are mostly restricted to the faults. Uranium mineralisation in these granitic rocks is mainly controlled by the sheared granite parts. Various radionuclides from uranium decay series such as (U-238, U-234, U-235, Th-230, Ra-226) and K-40 in the altered granite of Abu Garadi area that located in central Eastern Desert, Egypt are used to localise uranium accumulation sites in this pluton. Uranium and Thorium contents indicate that these altered granites have high thorium and high uranium granites. Th/U ratios vary between 0.81 and 5.79 with an average of 2.64, which suggests the presence of these samples in the transitional oxidation-reduction zone as evidenced by Th/U ratios>2 and reduction zone as suggested by Th/U ratios<2, respectively. U-238/U-235, U-234/U-235, U-234/U-238, Th-230/U-238, and Ra-226/Th-230 activity ratios confirm that most samples of Abu Garadi altered granite lie in the U-accumulations zone. All investigated samples clarify that uranium-series disequilibrium is a technique to trace the recent migration of uranium in these altered granites by the characterisation of the oxidation-reduction boundary.