Document Type : Original Article
Authors
1
Faculty of science, El-Azhar University, Nasr city, Cairo, Egypt.
2
Nuclear Materials Authority, Cairo, Egypt, B.O. Box: 530 El-Maadi
3
Nuclear Materials Authority, Cairo, Egypt, B.O. Box: 530 El-Maadi.
Abstract
The subsurface gneisses of Abu Rusheid area have been studied perfectly through two pre-pilot drillholes BH1&BH2 with depths of 70, 54m respectively comprising the geologic, petrographical and mineralogical studies applied to the picked core samples to throw light on their U-potentiality.
Lithologically, the core samples of BH1 are mainly (from top to bottom): quartz-hornblende schist, serpentinite, whitish gray granoblastic gneiss alternating with pinkish gray porphyroblastic gneiss with sharp contacts. While, the core samples of the BH2 are mainly (from top to bottom) whitish gray granoblastic gneiss, pink granoblastic gneiss, quartz-feldspar-biotite schist, quartz-hornblende-biotite schist, mica schist, talc carbonate, gray granoblastic gneiss with migmatite zone and finally whitish gray granoblastic gneiss.
Petrographic investigation revealed that, the pinkish dark-gray porphyroblastic gneiss of BH1 and pinkish granoblastic gneiss of BH2 are petrographically identical to granodioritic rocks (clearly granitoid composition, lake of pebbles and pelitic minerals such as cordierite and kyanite) alternated with whitish gray granoblastic gneiss of sedimentary origin ( presence of the fragments and pelitic metasomatic minerals; cordierite, kyanite, garnet and anthophyllite). The metamorphic sequence most likely represents a sequence of pelites and psammites, intruded by megacrystic granitoid injections from external sources below, then metamorphosed to an amphibolite-granulite facies assemblage. These results are important for understanding the tectonometamorphic evolution of the Abu-Rusheid area and add to the previous information about Hafafit metamorphic core complexes in the Eastern Desert, their mode of formation and formation of the present modeling are critical to future modeling of the overall tectonic evolution of the Arabian-Nubian Shield.
Mineralogical study indicated that, thorite and uranothorite are the most predominant radioactive minerals in the studied boreholes in addition to the uranophane that recorded in the zone between 23-24m in BH1. Other radioelements-bearing minerals were recorded such as columbite, pyrochlore, betafite, samarskite, fergusonite and zircon associating rare metals (bismuth and molybdenite) and base metals (pyrite, sphalerite and iron oxides).
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