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We present the geochemical and Sr–Nd–Pb isotopic data and the petrological evolution of primitive basaltic lavas that erupted from the Miocene to Quaternary in the East Anatolia Collision Zone to understand the geodynamic conditions and the change in the lithospheric mantle over time. Major trace element abundances, Sr–Nd–Pb isotopic compositions and petrological models show that the primitive basaltic samples were not affected by crustal contamination and fractional crystallization. They are derived from a depleted MORB mantle modified by melts derived from subducted sediments. The primitive melts of the Miocene and Quaternary series were derived from an amphibole-bearing garnet lherzolitic mantle and an amphibole-bearing garnet–spinel lherzolite mantle source, respectively. In contrast, the Pliocene basaltic melts were formed by mixing melts originating from both an amphibole-bearing spinel and garnet lherzolite. Our thermodynamic calculations indicate that the lithosphere–asthenosphere boundary (LAB) is about 30 km shallower in the Pliocene than in the Miocene.This may be explained by lithospheric delamination in the Early Pliocene. In contrast, the LAB in the Quaternary is approximately 9 km deeper than in the Pliocene, which can be explained by relamination of the mantle lithosphere. Thermal calculations have shown that about 5–11 km of the relamination can occur within 5–6 Ma and that asthenospheric melts can relaminate the base of the thinned lithospheric mantle by cooling, and the presence of the relaminated mantle lithosphere is documented throughout the whole EACZ. [ABSTRACT FROM AUTHOR]

Geochemical and isotopic markers of the most primitive basaltic melts allow us to understand the temporal evolution of the lithospheric mantle and geodynamic processes. This paper presents the geochemical, Sr-Nd-Pb-Hf isotopic data, K Ar dating and the petrological evolution of the petrogenesis of the late Miocene-early Pliocene basaltic volcanism observed in the Baltacık-Günkoru region in the northeastern of Lake Van in Eastern Anatolia Collision Zone (EACZ). These data allow us to understand the origin of collision-related magmatism and the geodynamic processes in the late Miocene-early Pliocene in the EACZ. Geochronological age data (K Ar) indicate that basaltic volcanism erupted between ∼7.63 and 5.24 Ma. Major-incompatible trace element contents, Sr Nd isotopic compositions of the studied samples and EC-AFC (energy-constrained recharge, assimilation, and fractional crystallization), and MELTS model calculations point out that basaltic volcanism has undergone fractional crystallization but unaffected crustal contamination. Petrological models created using 87Sr/86Sr, ℇNd and ℇHf isotopic data, together with calculated primary melt compositions of basaltic lavas, indicate that the DMM-type (Depleted Morb Mantle) mantle source is metasomatized by melts rather than fluids derived from subducted oceanic lithosphere. Combined trace element and isotopic modelling results indicate that the calculated primary melts were formed by 2.5–5% melting of a metasomatised spinel-garnet lherzolitic mantle source, including amphibole and 1% residual rutile. This mantle source has been metasomatised by a 1–3% contribution of subducted slab component, with a sediment melt/AOC (altered oceanic crust) melt ratio of about 90:10. Thermobarometric calculations based on calculated primary melts compositions indicate that the lithosphere-asthenosphere boundary (LAB) is a depth of 67 ± 4 km for 7.53–5.24 Ma. Literature data and the findings obtained from this study indicate that the late Miocene to early Pliocene basaltic volcanism in the south of the EACZ) is progressed by the delamination of the mantle lithosphere. This delamination occurred in a fragmented/patched or dripping manner rather than whole-scale delamination in the 3–4 million years between ∼9 Ma and 5–6 Ma. [Display omitted] • Studied basalts erupted in the Late Miocene to Early Pliocene. • LAB under EACZ decreased from Late Miocene to Early Pliocene via delamination. • Delamination emerged fragmented/patched or dripping rather than a whole scale. [ABSTRACT FROM AUTHOR]

The Pliocene Etrüsk stratovolcano, located in the northeast of Lake Van (Eastern Anatolia; Turkey), is one of the important volcanic centres in the Eastern Anatolian collision zone. Mt. Etrüsk overlies a widespread volcanic plateau, consisting of basaltic and hawaiitic lavas formed by fissure eruptions between 4.9–4.5 Ma. These basic lavas contain a phenocryst phase consisting of olivine, plagioclase and clinopyroxene. Trace element ratio diagrams imply that these basic magmas were generated from a mantle that contained a clear subduction component that is related to the subducted sediments rather than fluids or altered oceanic crust. Results of the melting models on the basaltic plateau lavas indicate that there was a marked variation both in the mantle source mineralogy (i.e. the ratio of garnet peridotite to spinel peridotite in the source varies between 60/40% and 40/60%) and the degree of melting (i.e. F between 0.8–4%). This can be explained by a model in which magmas were generated by partial melting of both metasomatised lithospheric and deeper asthenospheric mantle sources in an extensional setting in response to the partial delamination of the lithospheric mantle of Eastern Anatolia and then mixed with each other during Pliocene times. Central eruptions that formed the Etrüsk volcano lasted ~ 600 kyr between 4.3–3.7 Ma during Zanclean times. The estimated depth of the Etrüsk magma chamber is ~ 9–12 km. The volcano erupted lavas with a rather narrow compositional range from latite to rhyolite, which are either transitional or mildly alkaline in character. The Etrüsk lavas contain plagioclase, clino- and orthopyroxene, biotite, K-feldspar and rarely, minor amounts of olivine and amphibole in the phenocryst phase. A composite chemo-stratigraphic section of the volcano and petrological models indicate that the evolved lavas of the Etrüsk volcano differentiated from a parental magma composition, which is similar to that of the most primitive plateau basalt lavas underlying the volcano, via the AFC process, and experienced at least two major magma replenishment episodes at 4.1 Ma and 3.8 Ma during the magma chamber evolution. [ABSTRACT FROM AUTHOR]

The Eastern Anatolian region provides a good example for collision–related volcanic activity. This activity started during the Middle Miocene and continued through the Pliocene and Quaternary. The new K − Ar ages reveal that the post–collisional Pliocene Timar basalts located in the East Anatolian Accretionary Complex (EAAC) erupted between 4.72 (Zanclean) and 3.29–2.93 Ma (Piacenzian). The Pliocene Timar basalts consist of plagioclase, clinopyroxene (augite), and olivine minerals and have glomeroporphyritic, intergranular, and ophitic textures. They display enrichment in light rare earth elements (LREEs) with (La/Yb) N values that range between 3.19 and 6.66 to 21.63–5.61. 87Sr/86Sr(i) and 143Nd/144Nd(i) isotopic ratios of the Timar basalts are 0.70599–0.70436 and 0.51277–0.51259, respectively. The εNd(t) values of these rocks range between 1.0116 and 1.0121. 87Sr/86Sr (i) and Nd(t) contents indicate crustal contamination during the emplacement of the Timar basalts. According to the Energy Constrained–Assimilation Fractional Crystallization (EC–AFC) model, this contamination rate is between ~1.4 and 4.4%. The melting model shows that the least evolved samples of the Timar basalts were formed by ~0.1–2% partial melting of the lherzolitic source. Primitive melts that constituent Timar basalts were occurred with partial melting of a magma source that has predominantly spinel bearing mineralogy. All data indicate that the origin of the parental melts of the Timar basalts is metasomatized lithospheric mantle source and then these melts reached the surface from the fissures that is related to extensional tectonics in Pliocene. • The post-collisional Pliocene Timar basalts in the Turkish-Iranian high plateau. • The Geochemical and geochronological features of the Timar basalts. • The partial melting of a metasomatized spinel–rich lithospheric mantle source. • The EC-AFC modelling for the Pliocene Timar basalts. [ABSTRACT FROM AUTHOR]