Nuweibi Complex, Red Sea Governorate, Egypti

Regional Level Types
Nuweibi Complex	Complex
Red Sea Governorate	Governorate
Egypt	Country

Leucocratic, albite-rich granitoid with accessory Sn-Ta-Nb mineralization, intruded into a metasedimentary sequence (mica schists and hornblende schists) alternating with metavolcanics and serpentinites. Albite granite dikes and apophyses are common in the metasediments. Marginal pegmatite zones (stockscheider), quartz segregations and quartz-amazonite veins occur near the contact as well and these are locally associated with minor greisenization of the metasediments. Ore reserves are estimated at 30 million tons, grading at 0.02% Ta₂O₅ and 0.01% Nb₂O₅.

The intrusion is divided by the Wadi Nuweibi into two parts, West and East Nuweibi, which represent intrusive phases of the main intrusion. West Nuweibi covers an area of 1.0 km2 and is composed of medium-to-coarse-grained microcline-albite granites of the main phase. The contacts with the surrounding ancient granodiorites are almost vertical, with apophyses. East Nuweibi covers an area of 0.26 km2 and consists of white porphyritic albite granite of the additional phase. The contacts with the metamorphic rocks are shallow (15–20°) with apophyses in the surrounding schists, indicating a dome-like shape in the intrusion. The country rocks near the contacts have undergone uneven silicification and amazonitization. The contact between the phases is hidden under the sands of Wadi Nuweibi. In the outcrops of the eastern edge of the valley, a diffuse phase contact of the main phase granite is observed. Geochemical differences have also indicated the affiliation with different phases of the intrusion.
Topaz–zinnwaldite–amazonite–quartz stockscheiders and quartz lenses, with beryl with a thickness of 10–80 cm up to the first meter, are observed at the contacts between microcline–albite granites and schists. At the boundary of the main phase granite and the veins, a zone of striped albite aplite with a thickness of about 10 cm is observed. The main phase granite is disrupted by sub-meridional dolerite dikes. Unlike the Abu Dabbab intrusion, ore-bearing quartz veins are observed only in the host rocks. Veins of a north-northeast orientation have a thickness of 20–30 cm and a length of 100–800 m. The veins and adjacent greisens are composed of Li-micas, topaz, fluorite with inclusions of cassiterite, wolframite, and beryl. The Nuweibi LFGs are Ta ores with accompanying Nb and Sn.

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References