Radioactivity and geochemistry of Wadi el Reddah stream sediments, north eastern desert, Egypt

Abstract EN

Wadi El Reddah is considered as semi closed basin where the only open tributary is very narrow and has higher ground relative to the ground adjacent to the surrounding peaks.

The 238U activity concentrations range between 101.24 and 347.96 with an average 214.63 Bq Kg-1, 234U activity concentrations range between 89.67 and 308.19 Bq Kg-1 with average 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 ranges between 1092.71 and 1227.25 Bq Kg-1 with an average 1153.82 Bq Kg-1.

235U activity concentration ranges between 4.66 and 17.38 Bq Kg-1 with average 10.19 Bq Kg-1.

Most of stream sediment samples exhibit increase in SiO2, Fe2O3t, Na2O, P2O5 and K2O and L.O.I.

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 seawaters and in some hydrogenous deposits.