Orogenic lode-gold deposits and listvenization processes in the El-Barramiya area, Eastern Desert, Egypt

Abstract Gold mineralization in the El-Barramiya region of Eastern Desert, Egypt, is connected to post-accretionary stage throughout Central Desert. It represented by quartz, quartz-carbonate veins and disseminations listvenite rocks. The thrust contact between rock units area played an imperative part gold where obduction ophiolitic rocks over metasediments metavolcanics caused shear zones. Mineralization study formed along zones prefers precipitate transition zone low-grade regional metamorphic which high grade actinolite schist. lode mine situated E–W trending quartz a located intersections faults trend NE–SW (Najd fault), NW–SE NEE–SWW metavolcanic metasedimentary host Porphyry granite important role hydrothermal alteration process it represents source K, when fluids rich CO 2 bearing-K permeate alter previously altered ultramafic rocks, usually serpentinites mélange listvenitization includes silicification carbonatization metasomatic processes, tectonized are as becomes more intense close dipping transpressive faults. Geochemical studies mineralized helped determine genesis transformed bisulfide. whole geochemical data from elsewhere indicate that transformation serpentinite into involves profound modification bulk-rock geochemistry. chemical changes during dominated addition , removal H O, redistribution SiO MgO CaO carbonate minerals silica replace serpentine. All listvenites at deposit enriched CaO, Fe O 3 K but depleted compared with associated presumed represent their protoliths. Alteration also trace elements, some being locally remobilized within rock, added fluid phase, others leached out rock. Petrographic investigation show different types alterations (carbonatization silicification) mineralization. Mineralizations sulfides (pyrite, arsenopyrite smaller quantities chalcopyrite, sphalerite, galena, tetrahedrite gersdorffite) found auriferous disseminated listvenite. exposed brittle–ductile deformation structures such fractures controlling on formation act channels ways for flow. Fluid inclusions revealed was heterogeneous trapping O–CO temperature 280–340 °C pressure range 1.5–1.9 kbar, consistent mesothermal conditions.