Structural and remote sensing studies of gold mineralization and associated alteration in Abu-Marawat area, northern Eastern Desert, Egypt.

摘要

Gold has been mined in the Eastern Desert of Egypt since the time of the Pharaohs, yet the geologic setting of the gold mineralization, the structural controls, and its association with hydrothermal alteration zones is still not fully understood. A common application of remote sensing is to identify variations in surface mineralogy, structural elements, and geologic contacts. In this study, surface reflectance data derived from the Advanced Spaceborne Thermal Emission and reflection Radiometer (ASTER) imagery is used to map areas of high potential gold mineralization within hydrothermal alteration zones through refining previously used satellite image processing techniques. Spectral unmixing in n-dimentional spectral feature space has proven very accurate in distinguishing different alteration minerals, as well as highlighting the extent and main trend of alteration zones around Abu-Marawat area. Band ratio image (bands 4/8, 4/2, 8/9 in RGB) has proved to be efficient in highlighting areas for high-potential gold mineralization. Studying the areas of potential gold mineralization by looking at the associated structural elements has helped us understand the formation and evolution of mineralized zones. Detailed field mapping and structural analysis has helped to identify the main phases of deformation affecting the study area of Abu-Marawat. Mineralized quartz veins, mainly hosted in normal fault shear zones, developed during a period of island arc formation and represent the oldest phase of hydrothermal events in the area. These mineralized veins have been deformed by folding and were subsequently cut by relatively undeformed barren quartz veins. This proposed early phase of arc-related gold mineralization is consistent with the presence of gold-rich banded iron formations of Abu-Marawat that also formed during the arc formation stage.;The tectonic evolution model of the area is illustrated by relating the main structural elements to the major tectonic events that are known to have affected the study area. This model is compared to other tectonic model(s) proposed for the area for further validation.