Gharib (Gabal Gharib, Mount Gharib)

The crescent-shaped 55 km2 peralkaline Gharib granite cuts Pan-African granodiorites and adamellites and two dyke swarms (Abdel-Rahman and Martin, 1990). The granite has sharp, steep contacts, sends apophyses into the surrounding rocks and has a metasomatised aureole up to 2 km wide. The granite varies from coarse-grained and sparsely miarolitic at the lowest levels of exposure to vacuolar and fine-grained in the roof facies. The characteristic miarolitic cavities increase in size upwards reaching diameters of 50 cm at the highest levels. There are local cognate mafic inclusions. The granite comprises perthite, quartz, sodic amphibole, many grains being zoned from F-rich ferro-richterite cores to arfvedsonitic rims (Abdel-Rahman, 1987), and accessory astrophyllite, biotite, fluorite, aenigmatite, elpidite(?), zircon and ilmenite. A fine-grained roof facies contains acicular arfvedsonite. In the metasomatized aureole there have been major changes to the nature of the feldspar (Abdel-Rahman and Martin, 1990) and the development of fluor-arfvedsonite, astrophyllite and accessory fluorite. Whole rock analyses, including trace element data, are given by Abdel-Rahman and Martin (1990).