Significance of lineament patterns in rock unit classification and designation: a pilot study on the Gharib‐Dara area, northern Eastern Desert, Egypt.

Satellite images and aerial photos are among continuous sources of data for mapping lineaments which frequently reflect surfaces of discontinuity in the rocks. The analysis of lineaments not only provides a method for detecting past tectonic trends but also helps in the exploration of minerals, oil and ground water and the seismic risk assessment for nuclear sites and repository studies as well. In the present study, lineaments have been extracted from the digital satellite scene (Landsat 7, ETM + data) for the Gebel Gharib-Dara area using GeoAnalyst PCI EASI/PACE software. In a small test area, the lineaments that were digitally extracted for different settings of the GeoAnalyst parameters were compared with the visually interpreted lineaments for optimal settings of the parameters for lineament extraction. The visual interpretation of the present false colour composite map (FCC) led to tentatively classify the rocks into 24 units to study the spatial distribution of the extracted lineaments. Lineament patterns in the form of lineament azimuth profiles (LAPs) are prepared and they are very characteristic for each unit. The NE lineament trend predominates over all the rock units while the NW trend characterizes those units located towards the Gulf of Suez. LAPs show that the younger granitic rock units of Gebel Gharib, Gebel Abu Khashaba and Gebel Dara (having relatively high radioactivity) are characterized by short amplitude of NW trends relative to the NE trends. Correlating lineament density maps (LDM) with aeroradiometry total count contour maps and other ground radiometric maps show that rock units with high radioactivity are also characterized by high lineament density and lineament intersection density. Using the same reasoning, new possible uranium targets have been located. The present study also shows that the younger granitoid is the only rock unit which has been classified into four sub-lithologic units—G1, G2, G3 and G4—and they probably have a compositional variation that needs further field checking. [ABSTRACT FROM AUTHOR]