The Late Proterozoic volcanics exposed in Wadi Qabila, southeast Sinai, Egypt, occur in the form of a continuous ridge consisting mainly of rhyolitic lavas and their tuffs. They originated from high-K calc-alkaline magma that erupted during the final phase of Pan-African orogeny at an active continental margin setting.

Illite and chlorite are the major alteration products. Compositional variations of them as a function of temperature were investigated. As commonly shown, with increasing temperature, K-content of illite as well as the tetrahedral Al content of chlorite are positively correlated with decreasing proportions of mixed-layered components or discrete intergrown phases of mostly smectitic composition in both minerals.