El Kuk (Khor Eit)

El Kuk consists of a southern 19 km diameter ring complex the northern part of which is cut by a smaller, but substantial, intrusion of quartz porphyry; both are emplaced in Precambrian granodiorites. The core of the larger intrusion is composed of biotite granite and rhyolitic volcanic rocks. These are surrounded and intruded by a ring up to 5 km broad of arfvedsonite granite. Against the outer contact of the arfvedsonite granite along the southern margin are dykes described by Kuron (1978) as trachy- and porphyritic basalts, but the latter are said to contain 'aegirine-augite' and augite with rare olivine. At the southeastern and western margins of the complex discontinuous 'cone sheets' of carbonate rocks are found invading rhyolites and trachybasalts, and containing fragments of silicate rocks and minerals with reaction rims. The origin of these rocks is not clear. Mahmoud (1980) carried out gravity and magnetic geophysical surveys over the complex.