Mineralogical and radiometric studies of granitic rocks in Wadi Sabbagh Area, South Sinai, Egypt

Abstract

Wadi Sabbagh area is located at southern part of Sinai Peninsula. It is constrained by Latitudes 28° 05´ and 28° 15´ N and Longitudes 34° 00´ and 34° 15´ E. Gneisses, migmatites, metasediments, syn-and post-orogenic granites, in addition to pegmatites and post-granitic dykes are the main rock units encountered in this area. Geological, petrological and geochemical studies indicate that there are two distinct suites of granitoids: older tonalite to granodiorite assemblage and younger two phases (monzo- to syenogranites and alkaline granites). The field radiometric survey and lab investigations indicate that, the anomalous uranium contents are mainly restricted to the pegmatites and altered monzogranites. The eU contents of pegmatites reach up to 168 ppm with an average 117 ppm, while the eTh reach up to 257 ppm with an average 175 ppm. The eTh/eU ratios range from 1.1 to 2.4 with an average 1.6. In the altered monzogranites, eU reachs up to 305 ppm with an average of 126 ppm. The eTh reaches up to 382 ppm with an average of 166 ppm. The average values of Ra and K are 60 ppm and 2.93 wt percentage, respectively. The average values eTh/eU ratios in the examined anomalies monzgranites (1.56) indicating addition of uranium. The high eU and eTh contents may be attributed to the secondary ascending hydrothermal solutions that lead to the accumulation of radioactive mineralizations mostly along fractures, faults and shear districts. The recognized radioactive minerals in the studied pegmatites are thorite, uranothorite, zircon, fluorite, columbite, samarskite, monazite, xenotime and allanite, whereas thorite, uranothorite, zircon and fluorite are the foremost radioactive minerals in the altered younger granites. Additional accessory minerals such as ilmenite, magnetite, hematite, pyrite and rutile were found in the studied pegmatites. Hematite, magnetite and pyrite are the foremost accessories accompanying the radioactive minerals in the altered younger granites.