Ghorab Raiyan
A 4x2.5 km granite stock located 2 km east of the southern end of Gabal Ghorab Raiyan (a complex of biotite and muscovite granites) consists of biotite and biotite-riebeckite granites, the amphibole in the latter forming large prisms.
There is no full, general account of the alkaline rocks of Egypt but there are a number giving details of the main groups of 'ring complexes'. The fullest general description, which covers field relationships, petrography and petrochemistry of the alkaline rocks of the southeastern desert, is that of El Ramly et al. (1971) who describe 10 of the major complexes as well as many of the smaller occurrences. A useful compilation of chemical analyses of the igneous rocks of Egypt is that of Aly et al. (1983). Several papers list age data including those of Serencsits et al. (1979) (K-Ar), Hashad and El Reedy (1979) (Rb-Sr) and Omar et al. (1978) (fission-track).
A 4x2.5 km granite stock located 2 km east of the southern end of Gabal Ghorab Raiyan (a complex of biotite and muscovite granites) consists of biotite and biotite-riebeckite granites, the amphibole in the latter forming large prisms.
A granite stock of 5x4 km in the El Ghorab area is composed principally of granites containing biotite, muscovite and garnet but some areas of riebeckite granite are present. An average and range of granite chemical compositions are available (El Ramly et al., 1982b).
The Bir Um Hibal complex is an elliptical intrusion covering 15x10 km which is overlain in places by Nubian sandstone. Most of the complex consists of peralkaline quartz syenite but in the south a broad band of peralkaline granite intrudes the syenite (Mohamed, 1996).
The 3.5 km diameter northern Tarbtie structure is emplaced in a high plateau of Nubian sandstone, although the contacts are usually faulted. Ring-like features, particularly in the southern half of the intrusion, are expressed by wadis and fault and dyke patterns.
A Mesozoic ring complex and trachyte plugs and ring dykes are referred to by Armanious (1978)
This is a horseshoe-shaped intrusion rising 50-60 m above the surrounding Nubian sandstone, and is composed of ring-dykes of latite and agglomerates of latite, basalt and other rock types, around a central area of tuffs and agglomerates. The latites contain sodic amphibole.
This intrusion, emplaced in Nubian sandstones, forms an annular ridge 1 km in diameter rising 25-30 m above wadi level. It is composed of latites which are cut by latite dykes that are also annular; the dykes contain sodic amphiboles.
The complex, 4 km in diameter, forms a horseshoe-shaped ridge up to 500 m elevation open to the south, the opening being partly blocked by a circular peak.
A curving 8 km long ridge may represent the eastern half of a ring, the western part of which is obscured by volcanic rocks, Nubian sandstone, which is in places metamorphosed, and wadi alluvium.
This complex, lying some 15 km south of Tarbtie - north (No.049-00-032), is similar in consisting almost totally of peralkaline syenites with the remnants of two volcanic cones. The complex is bounded on the eastern side by Precambrian schists and gneisses; on the west by Nubian sandstone.