ANALYSIS AND INTERPRETATION OF AIRBORNE GAMMA-RAY SPECTROMETRIC AND AEROMAGNETIC SURVEY DATA, GABAL UM-NAGGAT AREA, CENTRAL EASTERN DESERT, EGYPT

The present work deals with the analysis and interpretation of airborne gamma-ray spectrometric and magnetic survey data of Um-Naggat area, Central Eastern Desert of Egypt. The main objective of this study is to delineate zones of alteration and mineralization in the albitized granitic country rocks of the Um-Naggat pluton. The pronounced rock alteration features, represented mainly by silicification, hematitization, fluoritization and kaolinitization, together with the prevailing fracturing system are believed to be the two main contributors to the occurrence of a radioactive mineralization. The intensity of mineralization was found to be closely related to the intensity of rock alteration. The albitized granites are characterized by relatively low magnetic field and high radiospectrometric background, with respect to the surrounding rocks. The three radioelement variable (K, eU and eTh) contour maps as well as their three relative concentration (ratio) contour maps (eTh/K, eU/eTh and eU/K) were correlated with the geological and landsat images of the study area to determine the zones of anomalous radioelement concentration and detect their relation to the prevailing surface structures. The aeromagnetic data were also analysed to visualize the subsurface structures and study their significance as a controlling factor in the localization of potential radioactive and associated non-radioactive mineral deposits. The radioactive and magnetic maps reveal that metasomatic processes are manifested more obviously at a relatively narrow zone restricted to the northern part of Um-Naggat pluton. The false colour composite image contour maps of the principal factors (F1, F2, and F4) proved to be a powerful tool for direct differentiation between altered (mineralized) and non altered zones in Um-Naggat pluton. The NNW to NW and NE structural lineaments as delineated from Landsat image and geological maps are well matched with the aeromagnetic lineaments as deduced from RTP, SVD and analytical signal maps