THE LITHOLOGICAL AND STRUCTURAL FEATURES CONTROLLING THE RADIOACTIVE MINERALIZATIONS IN YOUNGER GRANITES OF UM GURUF AREA, NORTH EASTERN DESERT, EGYPT

Abstract

Um Guruf area in the North Eastern Desert (NED) includes granodiorite, Dokhan volcanics, Hammamat sedimentary rocks, younger granites and post granite dykes. The study area is subjected to four main sets of joints trending NE-SW, ENE-WSW, E-W and N-S. All joints in the area are of tension stress. The main faults are of NW-SE, NNW-SSE and NE-SW trends based on their number proportion. All faults in the area are of compression stress. NE-SW trend is the master trend controlling the structural and tectonic framework of Um Guruf area followed by ENE-WSW trend. The younger granites show higher radioactivity than that of the other rock types. Radioactive anomaly is recorded in zoned pegmatite pocket in Hmrat El Sorwhyia alkali feldspar granites. It contains U and Th-bearing minerals of uranophane, thorite and zircon in addition to apatite, sphene and iron oxides which capture U and/or Th elements. The radioactive anomaly is structurally controlled by two strongly hematized and silicified joints striking NNE-SSW and NW-SE and two faults trending NNW-SSE and WNW-ESE.