Akademik Veri Yönetim Sistemi
Mediterranean Geoscience Reviews, cilt.4, sa.2, ss.247-272, 2022 (Scopus)
Lower Pliocene–Quaternary Gölcük volcano in SW Turkey, represented by potassic to ultrapotassic alkaline volcanics, is a well-preserved example with pre- and post-caldera volcanism comprising caldera-forming deposits, maar structures, and lava/dome flows. It has a 4 × 5 km diameter summit caldera. The volcanological history of the volcano is divided into two stages: (i) pre-caldera volcanism: intrusive and extrusive lavas including basaltic trachy-andesitic dykes; trachy-andesitic, trachytic and trachy-dacitic lava domes and caldera-forming eruptions. (ii) Post-caldera volcanism: intra-caldera tephriphonolitic lava/dome extrusions along the caldera rim, phreatomagmatic eruptions and finally intra-caldera trachytic domes. Post-caldera phreatomagmatic activity is represented by maar systems, containing ultramafic to felsic plutonic xenoliths having composition of generally phlogopite clinopyroxenite, monzonite and syenite. Phlogopite clinopyroxenite contain clinopyroxene, phlogopite and plagioclase. Monzonitic and syenitic xenoliths include orthoclase, plagioclase, hornblende, clinopyroxene, biotite, nepheline and apatite, sphene as accessory phases. Mineral chemistry and geochemical variations combined with petrographical and textural features of plutonic xenoliths and their host rocks reveal derivation from a common mantle source and the noticeable role of metasomatism. High (La/Yb)n (29–77) and low Ti/Eu (590–2010) ratios of host rocks and variations between Mg# (64–90) and Ca/Al ratio (4–22) of clinopyroxene imply that lithospheric mantle beneath Gölcük volcano was modified by both carbonate and silicate melts risen from the asthenosphere. Infiltration of these metasomatic melts within the overlying lithospheric mantle leads to the formation of amphibole/phlogopite-rich veins. Fractional crystallization following the partial melting of these veins and surrounding lithosphere caused the evolution of Gölcük magmas. Further, clinopyroxene-based thermometry of plutonic xenoliths indicates crystallization at crustal levels, ranging between 3 and 33 km.