Paleomagnetic and geological investigation into southern Sinai volcanic rocks and the rifting of the Gulf of Suez

Two volcanic occurrences from southern Sinai were sampled for paleomagnetic, petrographic and geochemical investigations. 29 oriented samples were taken from six sites of the Middle Jurassic basaltic intrusion at Wadi Budra, southwest Sinai (28 degrees 55'N, 33 degrees 20'E). After alternating field (AF) demagnetization and tilt correction, all samples exhibit normal magnetization with a mean paleomagnetic direction D=63.3 degrees, I=8.0 degrees and alpha(95)=10.2 degrees, This yields a paleopole position at lat, 25 degrees N, long. 133 degrees E and A(95) = 8.6 degrees. Also, six oriented blocks (34 core samples) were taken from the Sant Catherine doleritic dike at Wadi Sahl el Raha, south Sinai (28 degrees 33'N, 33 degrees 55'E). After AF demagnetization all sites showed normal polarity with a mean direction of magnetization D = 3 degrees, I= 39 degrees and alpha(95) = 15.3 degrees and a paleopole position at lat. 83 degrees E, long. 179 degrees E and A(95) = 16.5 degrees. The paleomagnetic pole of W. Budra is found to be incompatible with poles of similar age from Africa. The cause of this cannot be uniquely determined, but most probably could be referred to local tectonic rotations and/or geomagnetic secular variations affecting the paleomagnetic directions of these samples. In contrast, the Tertiary pole of Wadi Sahl el Raha is consistent with the part of the apparent polar wander path (APWP) of Africa for the time period 20 Ma (Oligo-Miocene age). Petrographical and geochemical investigations revealed that the volcanic rocks of both localities are continental within-plate, rift-related alkali olivine basalt (W. Budra) and olivine dolerite (Sahl el Raha). The primary magnetite is the main opaque mineral present in the samples, which represents the main carrier of magnetization in these rocks. (C) 2000 Elsevier Science B.V. All rights reserved.