THE LITHOLOGICAL AND STRUCTURAL FEATURES CONTROLLING THE RADIOACTIVE MINERALIZATIONS IN YOUNGER GRANITES OF WADI BALI AND WADI UMM SIDRAH AREA, NORTH EASTERN DESERT, EGYPT

Authors

1 Nuclear Materials Authority, P.O. Box 530, Maadi, Cairo, Egypt.

2 Geology Department, Faculty of Science, Al Azhar University, Egypt.

Abstract

The study area is located in the northern part of the Eastern Desert of Egypt. It is situated in the northern sector of Red Sea mountain ridges at about 65 km northwest of Hurghada City and is considered as one of high potentialities for uranium deposits. The study area comprises the younger granite of Gabal (G) Gattar, Hammamat sedimentary rocks of Gabal (G) Umm Tawat, Dokhan volcanic rocks in the centeral part of the area which are contacted northward by the younger granites of Gabal (G) Abu Harba. The younger granites are the most common rock type in the study area. There are two types of these granites: Gattar alkali feldspar granite to syenogranites and Abu Harba syenogranites. The structural deformations of the study area are represented by primary structures and secondary ones. The most prevailing structures are folding, faulting and jointing. The main trends of faults are NNE-SSW, NNW -SSE, N-S, NW-SE, NE-SW and WNW-ESE trends. All of these faults are of compression stress. The faults, especially those trending in the NNE-SSW and N-S are the main passways to the ascending uranium-bearing hydrothermal solutions. The study area is also affected by five main sets of joints trending NNE-SSW, N-S, NE-SW, WNW-ESE and NW-SE. All joints in the area are of tension stress. The gamma-activity measurements of the study area lead to the discovery of several occurrences. These occurrences are studied geologically, structurally and radiometrically in detail. The uranium content of the mineralized samples range from 155 ppm to 5570 ppm. The younger granites show higher radioactivity than that of the other rock types. It contains U and Th bearing minerals such as uranophane, thorite and zircon in addition to apatite, sphene and iron oxides which capture U and/or Th elements. Along GII occurrence the eU ranges from 59 to 4810 ppm with average 1271 ppm, while Th contents ranges from 13 to 270 ppm with an average 64ppm. At GV occurrence the eU ranges from 15 to 2740 ppm with an average 588, while Th contents range from 12 to 470 ppm with an average 90 ppm.

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