Radioactivity and Geochemistry of Wadi El Reddah Stream Sediments, North Eastern Desert, Egypt

Wadi El Reddah is a semi closed basin as it has only one outlet at its northern tip while the other parts of the wadi collect flood from the internal tributaries along granites and other rock types. ²³⁸U activity concentrations range between 101.24 and 347.96 with an average 214.63 Bq Kg^-1, ²³⁴U between 89.67 and 308.19 Bq Kg^-1 with an average of 190.10 Bq Kg^-1. ²³²Th activity concentrations vary between 96.42 and 463.71 Bq Kg^-1 with 240.46 Bq Kg^-1 as an average. ⁴⁰K activity ranges between 1092.71 and 1227.25 Bq Kg^-1 with an average of 1153.82 Bq Kg^-1. ²³⁵U activity concentration ranges between 4.66 and 17.38 Bq Kg^-1 with average of 10.19 Bq Kg^-1. Most of stream sediment samples exhibit an increase in SiO₂, Fe_2O3^t, Na₂O, P₂O₅ and K₂O and L.O.I, in addition to a prominent decrease in Al₂O₃, TiO₂, MnO, MgO, CaO. However, trace elements in the studied samples show enrichment in Ni, Cu, Pb, Zn, Cd, Ta, Nb, Zr, Y, Rb, Cs, Ga, Hf, Sn, Th, Tl, U, W, Mo, Bi, As, Be, Li, Sb and Au whereas they are depleted in Co, Sr, V, Ag, Cr and Sc. Zr, Hf and Y are relatively immobile and essentially concentrated in the accessory minerals (zircon and its alteration product branirite, xenotime, thorite and uranothorite). Their REE patterns are well characterized by the M- and W-type tetrad effects. The M- type tetrad effect could be inherited from the surrounding granitic rocks whereas the positive Y anomalies intimately associating with the W-type tetrad effect of REE mainly occur in natural aquatic solutions including sea waters and in some hydrogenous deposits. The presence of the two complementary tetrads may indicate the presence of gold mineralization