Petrogenesis of a high TiO2 mafic dyke swarm from southwest Sinai

A distinctive high Ti, Fe, P and Ba and low Mg, Cr and Ni mafic dyke swarm cross-cuts the Pan-African basement rocks in the area of Wadi Ager, southwe st Sinai. These dykes trend northwest and dip vertical and subvertical, sug gesting extensional tectonics in the northeast-southwest direction at the e nd of the Pan-African event. The dykes are mostly dolerites showing alkaline to calc-alkaline affinities . Essential mineral phases include plagioclase (An(54-67)), augite (Wo(41.8 -48.1)), Fe-Ti oxides and rare olivine. These rocks are akin to Proterozoic and Mesozoic rift-related high TiO2, basaltic dykes and flows (e.g. Blue R idge-Hudson Highlands of North America, Amundsen of Antarctica and the Para na Basin of South America). It is plausible that the dyke swarm is derived from a homogeneous lithospheric source which suffered a very low degree of partial melting. The dyke swarm experienced fractional crystallisation domi nated by the removal of plagioclase. This was, most probably, followed by a process of crustal contamination during magma ascent. (C) 1999 Elsevier Sc ience Limited. All rights reserved.