MINERALOGY, GEOCHEMISTRY AND RADIOACTIVITY OF GRANITIC ROCKS AND ASSOCIATED FLUORITE-QUARTZ VEINS, GABAL ADEDIA, UM BOGMA AREA, SOUTHWESTERN SINAI, EGYPT

Abstract

Mineralogical, geochemical and radioactive studies were carried out on both the granitic rocks of Gabal Adedia and its associated quartz-fluorite veins. The radioactive fluorite veins are filling the fissures and fractures of the host granite at the base of Gabal Adedia, the fluorite present in two forms as coarse-grained crystals disseminated in the younger granite or associated with quartz veins. The mineralogical investigations of the younger granite and its associated quartz-fluorite veins revealed the presence of secondary uranium mineral (kasolite), in addition to uranothorite, Fergusonite, monazite, allanite, bastnaesite, fluorite, zircon, xenotime, apatite, pyrite, barite, galena, chalcopyrite, sphalerite, covellite, bornite and atacamite. The studied granite and associated quartz-fluorite veins show enrichment in some rare metals (Cu,Zn,Zr,Y,Ba,Pb,Nb,U and Th) mineralizations. Multistage deformation, magmatic and hydrothermal processes accompanied by the events of uranium mineralization with the associated rare metals mineralization in different episodes affected Gabal Adedia. The normalized REE pattern of the younger granite and associated fluorite-quartz veins display negative Eu anomaly (Eu/Eu*= 0.54, 0.76) respectively. The younger granite is characterized by enrichment of LREE, in contrary the fluorite-quartz veins are enriched in HREE. Allanite, bastnaesite and monazite which are the most important REE carriers in this granite. These minerals are strongly enriched in LREE, whereas fluorite and xenotime which are more abundant in fluorite-quartz veins are enriched in HREE. The negative cerium (Ce) anomolia indicate high oxygen (O) fugacity at the source of the hydrothermal fluids. Positive yttrium (Y) anomalia articulate strong complexation with fluorite (F). The studied rocks have slightly high uranium and thorium contents, the younger granite have average U content is 27 ppm and the average of Th content is 54.4 ppm while in fluorite-quartz veins the average U content is 152.4 ppm and the average of Th content is 57.8 ppm.