Aeroradiometric and photogeologic characterizations Of the younger granites in the north eastern desert, Egypt and implications for mineral deposits

Abstract

Photogeologic studies of the younger granites in the North Eastern Desert of Egypt using both aerial photographs and satellite images revealed the separation of three successive phases of younger granites with different photogeological radiometrical and gcologiical characteristics. The first phase plutons (YG1) are charactlerizcd by brown colour, dark tone, fine surface texture, low relief with gentle slopes, elongated ridges, large size (3 km3), and high density -dendritic to parallcd-drainagc patterns. They have high density and frequency of photo lineaments. Radiomclrically these plutons are the lowest radioactive (60 - 100 u. R/h). The second phase plutons (YG2) arc characterized by its yellowish brown colour, light tone, moderate to coarse surface, texture, moderate relief with deep slopes, elongated ridges, relatively smaller size (1.7 km3) and moderate density trellis to dendritic-drainage patterns. Plutons of this phase have moderate density and frequency of photo lineaments. They display higher radioactivity (100 -180 u, R/h). The third phase plutons (YG3) are distinguished by oval shapes reddish brown colours, light white tone, smooth surface texture, high relief with steep slopes and rounded peaks, smallest size (1.4 km3) among the other types and low density dendritic to trellis - drainage patterns. They have low density and frequency of photo lineaments. They display radioactivity similar to the second phase but with anomalous zones more than 180 \i R/h. The YG1 is considered as an early (granodiorilic) phase of the younger granites while the YG3 is the highly differentiated latter phase where most of the radioactive anomalies arc restricted to. Tht YG3 of the North Eastern Desert comprise mineralization of U and molybdenite. Anomalous radioactivity arc concentrated along the NS, NNW, and NW fractures and especially at their intersections with the NE trend.