Geochronology and geochemistry of the Miocene Kadıkalesi monzonite (Bodrum Peninsula, western Anatolia): Implications for its relation with the South Aegean Volcanic Arc

Abstract

The Late Miocene igneous rocks of the Bodrum magmatic complex (SW Anatolia, Turkey), are composed of small monzonitic intrusions and trachyandesite-trachydacite volcanic rocks. The Kadıkalesi monzonite (KM) forms a small stock (<1 km2) made of plagioclase, biotite, hornblende, clinopyroxene, and quartz, and geochemically belongs to high-K calc-alkaline to shoshonitic, metaluminous series. The zircon separates from the KM yielded 9.5 ± 0.15 Ma core and 8.6 ± 0.04 Ma rim ages, revealing that emplacement of the monzonite continued up to ~8 Ma. The geochemical and mineralogical evidence suggests that the KM was derived by extensive fractionation of plagioclase, alkali feldspar, apatite, and clinopyroxene and/or Fe-Ti oxides and mixing of differently evolved melts. The monzonite has 760–866 Ma depleted mantle Nd Model ages which are considerably younger than the Cycladic and Menderes Massif plutons, as well as the other Miocene magmatic rocks from western Anatolia.On the basis of geochronological and geochemical features, we propose that the KM was fractionated from mafic melts derived from partial melting of spinel-facies (shallow depth) and crustally-contaminated (metasomatized/orogenic) asthenospheric mantle. Asthenospheric input were likely supplied from the slab window between the Aegean and Cyprian slabs, and likely contaminated by subducted sediments from the Aegean slab. It is also suggested that the current geodynamic setting of the Aegean region is also applicable to the Middle Miocene, meaning that the magmatic activity of the SAVA likely commenced at ~10 Ma, earlier than previously considered.