Nature and Geodynamic Setting of Late Neoproterozoic Vein-Type Gold Mineralization in the Eastern Desert of Egypt: Mineralogical and Geochemical Constraints

Abstract

The vein-type gold mineralization in the Eastern Desert of Egypt consists of sulphide minerals in stockwork quartz veins with hydrothermal alteration zones. The veins cut Neoproterozoic rocks along contacts between granite intrusions and island arc metavolcano-sedimentary sequence and ophiolitic rocks. Mineralization shows a clear structural control and is thus classified as orogenic gold. A post-peak metamorphic origin for the deposition of gold, sulphides, and carbonate gangue in the veins is suggested on the basis of various observations, such as: (1) gold mineralization is confined to quartz-bearing shear zones that cut host metamorphic rocks; (2) many sulphide minerals such as pyrite and arsenopyrite in addition to native gold and carbonate occur in different generations and parageneses; several of the sulphide generations are formed as a result of sulphidization of pre-existing metamorphic rocks; and (3) the depositional temperature of the hydrothermal minerals is commonly less than 400 °C. Based on relationships to magmatism and geodynamic framework, the gold deposits formed during the post-collision stage (~640–590 Ma) of Neoproterozoic crustal evolution. Major and trace elements data for 848 gold-mineralized samples of host rocks and quartz veins are treated statistically utilizing multivariate methods including discriminant function and R-mode factor analyses. From the geochemical exploration point of view, the Au-mineralized alteration zones developed within granitoids and schists are the most promising for gold exploration, as well as the auriferous quartz veins. Moreover, the Zn–Cu association in the central part of the Eastern Desert and Pb in the southern part could be indicators for auriferous alteration zones, whereas the Ni–Cu–Pb–Zn association could be an indicator for the Au-sulphide quartz veins.