Tertiary high-Mg volcanic rocks from Western Anatolia and their geodynamic significance for the evolution of the Aegean area

Abstract Scattered Late Miocene high-Mg basaltic andesites to dacites can be found in Western Anatolia. These rocks display Mg#>65, high CaO/Al2O3 ratio, low alkalies and TiO2 contents. Trace element distribution shows typical orogenic signature with higher values of Fluid Mobile Elements and lower values of HREE and HFSE with respect to Early Miocene Western Anatolia calc-alkaline rocks. The 87 Sr/ 86 Sr and 143 Nd/ 144 Nd ratios virtually overlap the values of the less evolved calc-alkaline rocks. The variations observed in this association have been attributed to an FC process combined with interaction with crustal material. A thermal anomaly affecting a depleted mantle source has been invoked for the genesis of these products. Such an anomaly was produced by the ascent of deep sub-slab mantle, which replaced the underthrust lithosphere, already thinned and stretched by extensional process.