Palaeomagnetism and Opaque Mineral Oxides of Some Basalt From West Central Sinai, Egypt

Abstract

A stable remanence was isolated from two intrusive Occurrences of volcanic rocks collected from west central Sinai, Egypt. Tertiary basalts at Wadi Nukhul have a predominantly reverse magnetization with mean direction D = 173.5", I = -60.7" (K = 46.6, (ug5 = 8.2", dyke and sill) and a palaeopole at 76"S, 193"E. Coarse primary magnetite (100-500 pm) with a Curie temperature between 540" and 580 "C is the principal magnetic mineral.A Mesozoic basaltic intrusion at Gebel Farsh El Azraq exhibits a predominantly normal magnetization carried mainly by fine-grained (50-300 pm) titanomagnetite.Its mean direction is D = 139", Z = 44.6" (K = 5.9, ~y g~ = 24.8", N = 8 sites) with a palaeopole at 28.6"s and 179"E. These results, together with other results from west central Sinai have been compared with the apparent polar wander path (APWP) for Africa given by Irving & Irving (1982). The Mesozoic poles are not compatible with poles of similar age for Africa, reflecting a local effect of tectonic rotations and/or geomagnetic secular variation. In contrast, the Egyptian Early Tertiary poles compare favourably with the relevant part of the African APWP for the period later than 40 Myr, in good agreement with the K-Ar ages of 22-25 Myr obtained for these intrusives.

Cenozoic and Mesozoic basalts from Egypt: a preliminary survey with a view to paleointensity

“…What has been long considered as one single Early Miocene magmatic episode would be in fact two different phases of volcanism? Finally, Tertiary pole positions defined for Sinai (Wassif, 1991;Abdeldayem and Tarling, 1996;Ibrahim et al, 1998;Saleh et al, 2004) are in agreement neither with other Tertiary pole positions for Egypt, nor with South African poles. Let's note here that discrepancies also exist within Africa, between the South and West African cratons, especially in Mesozoic time.…”