New Findings on Magmatic Evolution, Source Characteristics and Geodynamic Setting of The Kula Volcanics (City of Manisa) Western Turkey

One of the youngest volcanic areas in the Circum-Mediterranean region is located on a horst and graben system in the western Anatolian extensional province in Turkey, north of the city of Manisa. It is essentially made up of Quaternary-aged fresh primitive basic lavas and pyroclastics, which erupted from monogenetic cones and fissures. These volcanic materials cover an area of ~300 km2. In that area, there are over 80 scoria cones. Radiometric dating results published to date have revealed that the volcanism occurred in three different phases. The presence of human footprints pyroclastic material of the last stage in Kula can be proof of active volcanism during the Holocene period.Lavas erupted during the first stage range in composition from basanite to Phono-tephrite. They formed a small plateau in the N and NE of Kula, which was consequently deeply eroded in response to the uplift of the horsts. At present, the remnants of that plateau stand higher than the Elekçitepe and Divlittepe Stages in the form of mesas. Volcanic products of the 2nd Stage has a compositional range spanning from foidite to basanite, basalt, hawaiite, potassic trachy basalt, and phono-tephrite. 3rd stage volcanics display the narrowest compositional range, classifying as phono tephrite. Characteristically, they are made up of calcic plagioclase, zoned clinopyroxene, olivine.Lavas of the Kula volcanics display a clear within-plate geochemical signature which is more enriched than the average OIB. All lavas display a clear within-plate pattern with no Nb and Ta depletion on N-MORB-normalized multielement spidergrams. Hence they have no subduction signature. Chondrite-normalized REE patterns show a slight concave upward pattern in MREEs, indicating the possible involvement of amphibole in fractionation. Results of our petrological melting models based on trace elements, and distribution of data points on some diagrams which are used for the determination of source characteristics of the magmatic series indicate the presence of three contrasting sources for basic magmas. Two of these are of mantle origin, while, one is crustal. Our results indicate that first mantle source was a PM-like garnet peridotite, possibly asthenospheric in origin, from which foiditic mafic lavas containing MgO greater than 11 wt.% were derived. The second mantle source was represented by a Fe-rich metasomatized Gt-Peridotite. This mantle was probably of lithospheric origin, owing to its metasomatic nature. The third one was a Px + Phlg-bearing mafic crustal lithology highly metasomatized by the addition of magmatic batches. Most of the basic lavas from Kula appear to be mixtures of melts derived from the metasomatic peridotitic mantle and mafic (lower) crustal sources. We link the magma genesis to the combined effects of extension that created thinning of the lithosphere (also resulting in a static upwelling of the mantle altogether) and a tear in the slab beneath the region that gave way to much hotter upwellings from the sub-slab asthenosphere. We argue that the abovementioned metasomatism events both in the lithospheric mantle and mafic continental (lower) crust may be linked to that asthenospheric upwelling that brought a much hotter and primordial mantle below the lithosphere.