Gold-related Alteration Zones Detection at the Um Balad Area, Egyptian Eastern Desert, using Remote Sensing, Geophysical, and GIS Data Analysis

Abstract

The Um Balad area is a part of the Arabian Nubian Shield (ANS), which hosts various gold and base metal deposits. Gold can be prospected in the alterations and sheared zones in the widely exposed metagabbro-diorite rocks in the Um Balad area. In this regard, the image processing and analysis of the ASTER data is a rapid and efficient technique for such studies, where the structural pattern and associated lineaments are probable indicators of hydrothermal flow and activities developing in mineral-bearing alteration zones as targets for gold exploration. The Spectral Angle Mapper (SAM), Spectral Information Divergence (SID), and Mixture Tuned Matched Filtering (MTMF) techniques have identified the alteration zones and the characterized altered minerals of each alteration. The automatic lineament extraction method was used by ASTER's visible and near-infrared bands to produce a lineament density map. Using gamma-ray spectrometry data, the potassium percent (K %) and hydrothermal alteration parameters (F-parameter and Th-normalization) were calculated. As well as ratio maps (eTh/K and eU/K) were used to determine the potassic and phyllic hydrothermal alteration. The model of exploration for gold-related alterations was developed in the Um Balad area, using multiple layers derived from remote sensing and gamma-ray spectrometry data through a GIS (Weighted Sum Overlay) approach. The probability of gold-related alterations was graded as low, medium, good, and very good. A final map has been generated showing the gold-potential alteration zones in four localities (Area-1, Area-2, Area-3, and Area-4). In these altered zones, valuable minerals such as sulphides and gold may be precipitated, making them ideal gold exploration sites. The field observations and spectral signature analyses of the collected samples from the various identified alterations supported the results of the remote sensing and aero-spectrometry data analysis. Therefore, these techniques have been suggested for similar investigations in other areas.