Abstract
The Hangaliya gold deposit, located in the South Eastern Desert of Egypt, comprises a series of milky quartz veins along NW-trending Hangaliya shear zone, cutting through granitic rocks of Gabal Nugrus monzogranite. This shear zone, along with a system of discrete shear and fault zones, formed in the late deformation history of the area. The quartz vein emplacement took place under a brittle-ductile shear regime. Auriferous quartz veins are slightly sheared and boudinaged within the shear zone, especially in the hematized granite. Hydrothermal alteration is pervasive in the granitic wall rocks including sericitization, chloritization, fluoritization, sulphidization and minor carbonatization. The altered zones and associating quartz veins contain sulphides, gold, silver, cobalt, bismuth, and uraninite minerals. The Hangaliya gold veins include gold, silver, cobaltite, native bismuth, chalcopyrite, pyrite, galena, ferrocolumbite, fergusonite and uraninite. The Au-ore occurs in the quartz veins and adjacent wall rocks as dissemination in chalcopyrite and pyrite. Presence of refractory native silver, bismuth and cobalt in chalcopyrite is inferred from microprobe analyses. Wall rock sulphidization also likely contributed to destabilising the gold-silver, cobalt, bismuth assemblages and precipitation of the minerals in the hydrothermal alteration zone adjacent to the quartz veins. Gold occurs in two main modes: "invisible gold" in sulphides and native gold. Most of the "invisible gold" occurs in chalcopyrite and bismuth. The altered granites in the Hangaliya shear zone are enriched in Au, Ag, Bi, Co, and Ni with chalcopyrite, which suggests derivation of these metals from serpentinites due to interaction with the felsic Nugrus granite.
Highlights
The Eastern Desert of Egypt has long been a mining district for gold, with more than 95 gold occurrences mostly confined to the Neoproterozoic basement rocks (El Ramely et al, 1970; Abdel Tawab, 1992; Takla, 2001)
The present paper presents mineral chemistry and mineralogy of the noble elements and minerals associated with the auriferous shear zones
Mineral chemistry of polymetallic mineralization associated with altered granite, Hangaliya area, South Eastern Desert, ... 131
Summary
The Eastern Desert of Egypt has long been a mining district for gold, with more than 95 gold occurrences mostly confined to the Neoproterozoic basement rocks (El Ramely et al, 1970; Abdel Tawab, 1992; Takla, 2001). Osman and Dardir (1986, 1989) showed that gold mineralization at Hangaliya occurs in simple fissure-filling quartz veins in the WNW-ESE trending sheared Nugrus granite. Showed that the source of gold is multiple, being leached from the ophiolitic serpentinites, arc-metavolcanics and sulphide-bearing dolerite dykes They reported that the rock varieties in the auriferous shear zones in the granite are enriched in Cr and Co, which suggests transfer of these met als from serpentinites due to the interaction with the felsic Nugrus granite, which is enriched in U. The Hangaliya gold mine, located in the South Eastern Desert of Egypt (Fig. 1A), comprises a series of milky quartz veins along NW-trending shear zone, cutting through Gabal Nugrus monzogranites. Mineral chemistry of polymetallic mineralization associated with altered granite, Hangaliya area, South Eastern Desert, ... 131
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