Mineralization Significance of Airborne Gamma Ray Spectrometric and Magnetic Data of Gabal Umm Naggat Area, Central Eastern Desert, Egypt

Abstract

The area under study lies in the Central Eastern Desert of Egypt. It covers about 1417 Km2 in surface area and is located between Lat. 25° 10' 48'' and 25° 32' 56'' N and Long. 33° 56' 27'' and 34° 18' 7'' E. The study area is characterized by both gentle and rough topography. It is traversed by many wadis (dry valleys) as W. EL Miyah, W. Umm Gheig, W. Umm Bisilla and W. El Jundi. The topographic values range from 404-1286 meters. The study area is primarily occupied by basement rocks that include various volcano-sedimentary rock associations and ophiolitic mafic-ultramafic rock associations. Quaternary sediments in the mapped area represented by wadi sediments are composed of detritus, sands, pebbles and rare boulders that are generally created by weathering of previously-existing basement rocks. The general structural setting of the area under investigation could be summarized to dominant trends of surface structural lineament in two main trends ENE-WSW and NNW-SSE and miner trends in NE- SW and NW- SE directions. The radiometric gamma ray spectrometric data are in the forms of total counts (TC) in unit of (Ur), potassium (K) in (%), equivalent uranium (eU) and equivalent thorium (eTh) in (ppm). In addition of the ratios of eU/eTh, eU/K and eTh/K, these seven variables are then gridded, colored, and contoured for better qualitative interpretation of the radioelement distributions through the different surface exposed rock units. Zonation maps of TC, eU, eTh and 3D view of TC clearly demonstrate the contact and dimensions of alteration zone of albite granite of Umm Naggat pluton in terms of radiometric point of view. TC values range is from 28.3 to 75 in Ur, eU values range is from 11 to 38.1 ppm and eTh values range from 29 to 56 ppm and the dimensions is represented by two locality on oval shape. Both locality has E-W direction. Albite granite anomalous zone it could be considered as a primary target. Factor analysis technique are used for carrying out the quantitative interpretation, with seven variables of TC, eU, eTh, K%, eU/eTh, eU/K and eTh/K to generate three factors F1, F2, F3, where those factors could facilitate the spatial correlation of features in the various data sets, and at the same time displayed variations which difficult to be determined. These factor scores are multiplied by 100 and then gridded, colored and contoured. Factor1 can be identified as the factor of integrated radioactivity or factor of uranium exploration. Factore2 used to different the rock type. Factor 3 refers to rock basicity.