Volcanogenic talc-copper deposits of Darhib-Abu Jurdi area, Egypt: Petrogenesis and remote sensing characterization

Economic talc deposits were developed as an integral part of a volcanogenic massive sulfide system in Darhib-Abu Jurdi bimodal-mafic type submarine volcanics in the South Eastern Desert of Egypt. These Pan-African metavolcanics were erupted in a rift-related environment and experienced low-grade greenschist metamorphism. They host talc-malachite mineralization, mainly within E-W trending alteration zones along the major latitudinal shear planes. These mineralized alteration zones contain economic talc deposits as well as averages of 1.7% Cu and 0.46% Zn; the maximum may exceed 11% Cu. Sentinel-2, ASTER, and Landsat-8 dataset in conjunction with a portable TerraSpec Halo mineral identifier device (ASD) were employed in detecting and mapping these mineralized alteration zones within the Darhib-Abu Jurdi metavolcanics. Petrography, mineralogy, and geochemistry of these deposits and host volcanics enabled to put constraints on their petrogenesis and evolution as a submarine hydrothermal vent system. Mineralogical characteristics of pervasive chloritization stringer zone, hypogene primary sulfide ore zone, and supergene oxidized zone are addressed and discussed. Talc deposits were formed at Darhib-Abu Jurdi area as the main gangue phase via (a) direct precipitation on seafloor by interaction of silica-saturated hydrothermal fluids with Mg-rich seawater, (b) precipitation with actinolite/tremolite at shallow depth beneath the sulfide ore lenses due to penetration of Mg-rich seawater into hydrothermal conduit, and (c) replacement of pre-existing tremolite, actinolite, chlorite, and septechlorite.