A geochemical perspective on the genesis of Cenozoic basic volcanism in northeastern Turkey: an overview of metasomatism and heterogeneity of the sub-continental lithospheric mantle in a post-collisional setting

The post-collisional Cenozoic basic volcanic rocks in NE Turkey show temporal variations in whole-rock lithophile element and highly siderophile element (HSE) systematics that are mainly associated with the nature of sub-continental lithospheric mantle (SCLM) sources and parental melt generation. So far, the traditional whole-rock lithophile geochemical data of these basic volcanic rocks have provided important constraints on the nature of SCLM sources. Integrated lithophile element and HSE geochemical data of these basic volcanic rocks also reveal the heterogeneity of the SCLM source, which is principally related to variable metasomatism resulting from previous subduction(s) and post-collisional mantle-crust interactions in an extensional setting. Lithophile element geochemical features suggest that the parental magmas have derived from metasomatized spinel- to garnet-bearing SCLM sources for Eocene and Miocene basic volcanic rocks with subduction signatures whereas originated from spinel- to garnet-bearing SCLM sources for Mio-Pliocene and Plio-Quaternary basaltic volcanic rocks without the subduction signature. Lithophile element and HSE geochemistry also reveal that Eocene and Miocene basic volcanic rocks were affected by more pronounced crustal contamination than the basaltic volcanic rocks of Mio-Pliocene and Quaternary. Furthermore, the integrated lithophile element and HSE compositions of these basic volcanic rocks, together with the regional asymmetric lithospheric delamination model, reveal that the compositional variation (especially due to metasomatism) was significant temporally in the heterogeneity of the SCLM sources from which parental magmas formed during the Cenozoic era.