Geology And Radioactivity of Gabal Halal, Northern Sinai, Egypt

Gabal Ralal is one of the major asymmetrical doubly- plunging anticlinal fold belts (50 Km length) related to the Syrian Arc System in northern Sinai, Egypt. The exposed rock units at Gabal Ralal range from Cretaceous to Quaternary and are divided into eight formations which are from base to top: Malha, Ralal, Wata, Themed, Sudr, Beida, Egma and Quaternary wadi deposits. The image processing is applied using Landsat-7 satellite data to discriminate structure and lithology for defining the horizons of the radioactive anomalies of each rock unit. The extracted structural lineaments, using Ge Analyst-PCl package, from digital ETM data showed that the main structural trends are NE-SW and NW-SE normal faults which originated as extensional fractures with lateral dip-slip displacement. The axial trace of Gabal Ralal fold is curved and plunging to Wand SW directions while the northeastern part (Gabal Dalfa) is plunging to NE direction. The use of remote sensing data and field radiometric measurements of each rock unit revealed the presence of three radioactive anomalies in Malha, Themed and Sudr Formations. The recorded radioactive anomalies in Malha Formation is ranging from 50 ppm to 75 ppm due to the capture of uranium by iron oxides of oolitic ironstone and iron concretions in the thick-bedded ferruginous sandstone member. The presence of radioactive anomalies up to 71 ppm in the upper unit of Themed Formation and 90 ppm in the middle member of Sudr Formations is due to the presence of phosphatic beds hosting uranium in the phosphatic components. The effect of Syrian Arc System and the structural framework of the area led to the redistribution of the rock units hosting radioactive anomalies