Mineralogical and geochemical characterization of the Wadi Natash volcanic field (WNVF), Egypt: Alkaline magmatism in a Late Cretaceous continental rift system

Abstract

The Wadi Natash volcanic field (WNVF) in the south of the Eastern Desert of Egypt is a typical example of well-preserved intraplate alkaline magmatism during the Late Cretaceous, i.e., prior to the Oligo-Miocene Red Sea rift. We compiled stratigraphic sections at two sectors; namely East Gabal Nuqra and West Khashm Natash (WKN) where the volcanic flows are intercalated with the Turonian Abu Agag sandstone with occasional paleosols when volcanic activity is intermittent. Peridotite mantle xenoliths are encountered in the first sector whereas flows in the second sector are interrupted by trachyte plugs and ring dykes. On a geochemical basis, the mafic melt originating from the lithospheric mantle beneath the WNVF practiced ~ 5% partial melting of phlogopite-bearing garnet peridotite. Basalts dominate in the two sectors and highly evolved (silicic) rocks are confined to the WKN sector. Rejuvenation of ancient Precambrian fractures following the NW–SE and ENE-WSW trends facilitated the ascend of Late Cretaceous mantle-derived alkaline magma. Structurally, the WNVF developed at the eastern shoulder of the so-called “Kom Ombo-Nuqra-Kharit rift system” that represents a well-defined NW-trending intracontinental rift basin in the southern Eastern Desert. In such a structural setup, the Natash volcanic are confined to half-grabens at the East Gabal Nuqra sector whereas the West Khashm Natash sector is subjected to extensional stresses that propagated eastwards. The WNVF is a typical example of fluvial clastics (Turonian) intercalation with rift-related alkaline volcanic rocks in northeast Africa.