Petrogenesis of Basalts from Southern Turkey: the Plio-Quaternary Volcanism to the North of İskenderun Gulf

Abstract

AbstractThe Quaternary volcanicity north of the İskenderun Gulf in the eastern Mediterranean is represented by small basaltic scoria cones and flows. Approximately 115 km2 of land area is occupied by young basalts which straddle both the main (the Karataş-Osmaniye Fault Zone) strike-slip fault system which forms the Africa-Turkey Plate boundary and the suture of the southern arm of the former Neotethys Ocean. Detailed petrological and geochemical analyses of these rocks have been carried out, with the aim of trying to understand why they have erupted in this locality. The rocks consist mainly of basanites (43–46ilica; 3.9–6.5% alkalis) and some alkali olivine basalts (45ilica; 3.8–4.2% alkalis). Both the basanites and alkali olivine basalts are porphyritic, vitrophyric and highly vesiculated with euhedral and subhedral olivine (Fo82-Fo78) phenocrysts set in a fine-grained groundmass of olivine (Fo70), plagioclase (An71-An66), clinopyroxene and titanomagnetite. Olivine phenocrysts contain abundant Cr-spinel and titanomagnetite inclusions. Some geochemical characteristics of these basalts indicate similarity with extension-related alkali basalts; others indicate similarity with ocean island basalt; and yet others indicate subduction-related characteristics. This complexity leads to difficulties with interpretation, especially since there is no demonstrable local extension, subduction or mantle plume activity in the vicinity.