Petrogenesis of the Quaternary mafic alkaline volcanism along the African-Anatolian plates boundary in Turunçlu-Delihalil (Osmaniye) region in southern Turkey

Mafic alkaline lavas in Turunçlu-Delihalil region (Osmaniye) in southern Turkey erupted from extensional fractures and volcanic cones such as Delihalil and Üçtepeler along strike-slip fault systems in the Ä°skenderun Basin, which is bordered by Misis-Andırın complex (MAC) that is an accretionary prism. New ArAr dating results indicate that volcanic activity occurred between ~2.1 Ma (alkali basaltic melts) and 120 ka (basanitic melts). The volcanic products are alkaline in character. Major and trace element abundances and EC-AFC models using Sr and Nd isotopic ratios are used to propose that the basanitic samples were subjected to fractional crystallisation but were not affected by significant crustal contamination in contrast to the alkali basaltic samples which contain up to 2-5% crustal assimilation. Partial melting models using fractionation-corrected data indicate that the petrogenesis of the alkali basalts can be explained by mixing of melts from phlogopite-bearing garnet peridotite with melts from phlogopite bearing spinel peridotite, in contrast to basanites which could have been derived only from the phlogopite bearing garnet peridotite mantle source. It is inferred that the phlogopite may have formed in lithosphere-asthenosphere boundary by metasomatic melts or fluids from a rising asthenospheric mantle. Melt generations with residual phlogopite indicate melting at temperatures of 1275-1390 °C at pressures of 2.8-3.7 GPa.