Discovery of uranium mineralizations in the rhyolite-granite complex in the Jabal Eghei area of southern Libya

Abstract

During an investigation of the Jabal Eghei area in southern Libya and the production of geological maps on a scale of 1:250 000 (Tibesti sector, sheet Wadi Eghei NF 34-1 and NF 34-2), regional prospecting for mineral raw materials was performed. A radiometric survey of the observed targets at the sites indicated two significant uranium mineralizations in rhyolites, and some smaller ones in granites that are in close contact with rhyolites. Rhyolites are located in the central part of the investigated region. They cut through granite rocks. The first mineralization is in the central part of the rhyolite region, which is mostly composed of silificated rhyolites. The second one was discovered near the granite-rhyolite contact zone, characterized by the presence of silicified breccia rocks. These findings were confirmed by laboratory measurements of more than seventy samples collected in the area, using high-resolution gamma-ray spectrometry. The concentrations of uranium in these mineralizations were found to range from approx. 50 mg kg-1 to more than 600 mg kg-1. The latter value is about 240 times above the Earth's average. Besides uranium, these measurements have also given concentrations of thorium and potassium. Additional geochemical analysis was performed on samples taken from locations where uranium anomalies were discovered using the ICP-MS technique, in which the concentrations of more than forty elements were determined. The uranium mineralizations are accompanied by increased contents of silver (up to 17 times), arsenic (up to 8 times), molybdenum (up to 50 times), mercury (up to 9 times), and lead (up to 14 times), with regards to the Clark values. These results warrant a continued investigation of this region because of potential interest in the discovery of nuclear mineral raw materials. Copyright (C)2013 SCS.