Shoshonitic volcanism of the Bodrum caldera (SW Turkey): Hybridization of enriched mantle-derived and crustal melts

Bodrum Caldera, located at the southwestern tip of the Anatolian plate, comprises volcanic rocks formed by intrusive, effusive and explosive volcanic activity during Miocene. Volcanic rocks chemically belong to K-rich shoshonitic series and comprised of a range of compositions from absarokites to rhyolites with intrusive micromonzogabbros and micromonzonites. The least evolved magmatic rocks are the post-caldera micromonzogabbros. Blebs/droplets with different mineralogical/petrographical characteristics and resorbed xenocrystic glomerocrysts/cumulates comprised of feldspar and clinopyroxene in disequilibrium with the host rocks suggest that mixing between compositionally different magmas was an important process for the evolution of Bodrum volcanism. Especially shoshonites contain mixing and mingling textures probably occurred between monzogabbroic and more evolved monzonitic magmas. Fractional crystallization was limited to felsic (>60% SiO₂) rocks where feldspar, pyroxene, biotite, apatite and zircon were the main fractionating phases. Trace element abundances indicate a garnet-bearing enriched mantle peridotite, resembling EM-1 with a modal assemblage of garnet, rutile, titanite and phlogopite, as the common mantle source rock. Non-modal fractional melting models exhibit that micromonzonites, absarokites and micromonzogabbros were derived from lower (1–3%), moderate (10–15%) and higher (>20%) degrees partial melting of an enriched mantle, respectively. Besides, monzonitic compositions can be produced by partial fusion of a subducting slab with hypothetical composition of 80% GLOSS and 20 % N-MORB. Basic-intermediate compositions can be produced by the mixing/mingling of the micromonzogabbroic and monzonitic magmas. Crustal assimilation and fractional crystallization of hybrid absarokitic melts can yield intermediate-to-felsic compositions of Bodrum shoshonitic series.