Distribution of radioactivity at North Wadi Kareim area and correlation with the surrounding areas, Central Eastern Desert, Egypt

Abstract

North Wadi Kareim area, Central Eastern Desert of Egypt, covers about 130 km 2 of basement complex composed of a sequence of igneous and metamorphic rocks of late Precambrian age. The present study deals with the distribution of radioactivity amongst the different lithological units, especially in bostonites and trachyandesites, the structural control of radioactivity and geological studies. Radiometric measurements were carried out for each rock unit, with comparative studies of the surrounding areas. The relationship between radioactivity and the age of rocks, according to their chronological sequence, revealed that the younger rocks had a higher intensity of radioactivity compared with the older ones. Significant radioactive anomalies were discovered in the younger alkaline volcanics, namely bostonites and trachyandesites. Radiometric studies carried out along structural features showed that bostonites and trachyandesites were invaded along fault zones and that faults devoid of bostonites and trachyandesites were barren of radioactivity. Radioactivity is connected with joints normal to the contact of buff bostonite bodies with the country rock, while the radioactivity of trachyandesite is due to mass effect. Radioactive joints cutting the bostonite bodies were measured and the trends of radioactive fractures are N45°E and N15°W. Bostonite dykes and sills were plotted on an equal area stereographic projection and they have a semicircular shape.