Volcanic Rocks from Foca-Karaburun and Ayvalik-Lesvos Grabens (Western Anatolia) and Their Petrogenic-Geodynamic Significance

The Foca-Karaburun and Ayvalik-Lesvos grabens (western coast of Anatolia, Turkey) are two important NW-SE-trending extensional areas generated in response to the Early Miocene-Holocene extension of the Western Anatolian region, related to the opening of the 'unconventional' back-arc basin of the Aegean Sea. The abundance of geo-structural evidence and the occurrence of volcanic rocks representing all the stages of the Aegean-Western Anatolia volcanism render the Foca-Karaburun and Ayvalik-Lesvos Grabens key localities to exemplify the petrogenetic and geodynamic evolution of the area. In this context, the Foca-Karaburun and Ayvalik-Lesvos grabens, possibly formerly a single graben, formed along an original NE-SW-trending extension, later dissected by E-W-trending transtensional faults, are investigated to constrain the petrogenetic and geodynamic evolution of the whole Aegean region. Calc-alkaline and shoshonitic volcanic rocks with scattered ultrapotassic-shoshonitic or lamproitic lavas and dykes represent the orogenic phase of the magmatic activity, while the younger K-and Na-rich alkaline basaltic rocks are the result of later magmatism characterized by an intraplate geochemical signature reflecting progressively decreasing subduction rates.