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

Abstract

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°55′N, 33°20′E). After alternating field (AF) demagnetization and tilt correction, all samples exhibit normal magnetization with a mean paleomagnetic direction D=63.3°, I=8.0° and α 95=10.2°. This yields a paleopole position at lat. 25°N, long. 133°E and A 95=8.6°. Also, six oriented blocks (34 core samples) were taken from the Sant Catherine doleritic dike at Wadi Sahl el Raha, south Sinai (28°33′N, 33°55′E). After AF demagnetization all sites showed normal polarity with a mean direction of magnetization D=3°, I=39° and α 95=15.3° and a paleopole position at lat. 83°E, long. 179°E and A 95=16.5°. 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.