Contribution to the study of radioactivity in younger granites in Southeastern Desert, Egypt

Abstract

The Egyptian granites are the most dominant rock unit of the basement complex in Eastern Desert. Several geological investigations and classifications were carried out on these granites. They were classified according to relative age, dominant colour, type locality and their apparent relation to orogeny. Most of the discovered radioactive occurrence are encountered in the younger granites which are generally enriched in uranium than other rock types. The present work deals with the distribution of radioactivity in younger granites represented in the Southeastern Desert of Egypt and the identification of these granites on aerial photographs and photomosaics in a trial to differentiate between granites with normal to moderate radioactivity and those having higher and anomalous radioactivity. The younger granites have a wide range of radioactivity which is from 400 to 1000 count per second in the granites with normal to moderate radioactivity while it reaches 2000 count per second in the granites with abnormal radioactivity as given in the radiometric map constructed by Lockwood in 1968. Some outcrops of the second type are found with disseminated uranium mineralizations, and in certain localities field measurement of their radioactivity gave values of 10 000 count per second, and even more. Photogeologically, the younger granites are characterized by lighter tone, coarser surface texture, angular to rectangular drainage pattern and the sharp contact against the other types of rocks. Granites with higher to anomalous radioactivity are highly fractured as compared with the other rocks of younger granites.