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

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Abstract
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.

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