We report the results of a study on early Miocene to Pleistocene volcanic rocks cropping out west of the Karlıova Triple Junction in Eastern Anatolia (Elazığ, Tunceli, and Bingöl provinces). Here the Eurasia–Arabia convergence resulted in collision, marked by the Bitlis–Zagros suture (∼13 Ma), followed by activation of the dextral transform North Anatolian Fault (NAF). At ∼6 Ma the formation of the sinistral transform East Anatolian Fault (EAF) marked the separation of the Anatolian block, which became a kinematically independent plate. On the basis of petrographic, geochemical and Sr–Nd–Pb isotopic characteristics, as well as new ⁴⁰Ar–³⁹Ar age determinations, we distinguish three phases of activity: (1) early–middle Miocene (16·3–15·5 Ma) production of calc-alkaline basaltic trachyandesite to dacites in the Pertek and Mazgirt districts; (2) emplacement of late Miocene (11·4–11·0 Ma) transitional basalts in the Tunceli area; (3) emplacement of Plio-Pleistocene Na-alkali basalts in Karakoçan (4·1 Ma) and Elazığ (1·7 Ma). The oldest samples are characterized by large ion lithophile element (LILE) enrichment (e.g. Ba/Nb = 32–76) with high ⁸⁷Sr/⁸⁶Sr (0·7052–0·7065) and low ¹⁴³Nd/¹⁴⁴Nd isotopic ratios (0·51246–0·51262). The late Miocene basalts display variable geochemical characteristics, including large variations in ⁸⁷Sr/⁸⁶Sr (0·7039–0·7068) and LILE/HFSE (high field strength element) ratios (e.g. Ba/Nb = 13–36). The Plio-Pleistocene alkali basalts have higher LILE and HFSE contents and lower LILE/HFSE ratios (Ba/Nb = 8–21) compared with the two previous groups, low ⁸⁷Sr/⁸⁶Sr (0·7033–0·7038) and high ¹⁴³Nd/¹⁴⁴Nd (0·51270–0·51290), with compositions similar to those of oceanic intraplate magmas. Pb isotopes vary slightly: ²⁰⁶Pb/²⁰⁴Pb ranges from 18·66 to 19·11, ²⁰⁷Pb/²⁰⁴Pb from 15·64 to 15·72 and ²⁰⁸Pb/²⁰⁴Pb from 38·67 to 39·24, with the calc-alkaline early–middle Miocene rocks characterized by higher ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb at a given ²⁰⁶Pb/²⁰⁴Pb. The evolution of volcanic activity is strictly linked to the geodynamic scenario. The early–middle Miocene magmas, emplaced in a convergent setting, indicate derivation from mantle sources modified by subduction components, whereas the late Miocene Tunceli transitional basalts mark the change from compressional to strike-slip tectonics. During the development of the NAF and EAF, passive upwelling of the sub-slab mantle, favoured by the formation of small pull-apart basins, led to the onset of Na-alkali basaltic activity.

Anatolia is characterised by a complex geodynamic evolution, mirrored by a wide spectrum of magmatism. Here, we investigated the timing and the geochemical/isotopic characters of the Miocene to Pliocene volcanism of Sivas–Malatya Region (Central Eastern Anatolia), and its relationships with local and regional tectonics. Na-alkaline basaltic lavas were emplaced during middle Miocene at Sivas (16.7–13.1 Ma), in the North, whilst transition from calc-alkaline to Na-alkaline rocks is observed at Yamadağ and Kepez Dağ volcanic complexes. Calc-alkaline products erupted during early to middle Miocene, and more precisely from 19.5 to 13.6 Ma at Yamadağ and from 16.4 to 13.5 Ma at Kepez Dağ, with final Na-alkaline activity of the Arguvan volcanic field lasting till late Miocene (15.7–10.6 Ma). Volcanism renewed during the Pliocene in the Kangal (5.9–4.0 Ma) volcanic field with the emission of K-alkaline igneous rocks. Mafic calc-alkaline and Na-alkaline rocks partially overlap in age but can be easily distinguished by their petrochemical characters. Mafic calc-alkaline igneous rocks show typical subduction-related petrological and geochemical affinities. They are both two-pyroxene or clinopyroxene and amphibole-bearing rocks, characterised by high LILE/HFSE values, with variable ⁸⁷Sr/⁸⁶Sr_i (0.70396–0.70539) and ¹⁴³Nd/¹⁴⁴Nd_i (0.51260–0.51287). Mafic Na-alkaline igneous rocks are characterised by big olivine phenocrysts and show intraplate geochemical flavours, although some LILE depletion with respect to HFSE as well as variable ⁸⁷Sr/⁸⁶Sr_i (0.70347–0.70553) and ¹⁴³Nd/¹⁴⁴Nd_i (0.51261–0.51291) isotopic compositions are present. These characteristics are suggestive for the occurrence, at some stage of their genesis, of a possible interaction with subduction-related reservoirs. The Kangal K-alkali basalts still show intraplate-like petrological and geochemical affinities with LILE/HFSE ratios similar to those of the Miocene Na-alkaline rocks, and largely variable ⁸⁷Sr/⁸⁶Sr_i (0.70425–0.70520) and ¹⁴³Nd/¹⁴⁴Nd_i (0.51262–0.51277) isotopic compositions, overlapping the arrays observed in the earlier stages of volcanism. A general transition from calc-alkaline to Na-alkaline volcanic rocks is observed with time, according to the evolution of the geodynamics of the Anatolia region. Early to middle Miocene calc-alkaline magmas were derived by partial melting of the mantle wedge delimited by the subduction of the last oceanic branch of Neotethys. The Na-alkaline magmas, on the other hand, were generated within the asthenospheric mantle beneath the slab and migrated through slab tears into the mantle wedge where they mixed with subduction-related components. The subduction-related component decreased with time and transitional magmas are found in the youngest activity of Yamadağ and Kepez Dağ, shortly followed by clear within-plate lavas formed in the Arguvan volcanic field. The appearance of the youngest K-alkaline volcanic rocks in the Kangal basin represents an abrupt change in the magma supply at depth, although continental crustal contamination en-route to the surface played an important role in their genesis.

Widespread sodic alkali basaltic activity developed from Early Miocene to Pleistocene, around the northern termination of the Dead Sea Fault Zone, and in the North-West foreland of the Arabian Plate, in South-East Turkey. Volcanic activity started within the Gaziantep Basin during the Early-Late Miocene (21.2-7.0 Ma), and further East, abundant magmatism brought to the formation of the Karacadağ Shield Volcano, starting from Middle Miocene throughout the Holocene (12.1-0.01 Ma). During the Pleistocene, volcanism developed also around the Anatolia-Africa-Arabia triple junction, along the Karataş-Osmaniye Fault, and along the northern segment of the Dead Sea Fault, in the Karasu Basin.Volcanic rocks emplaced in these areas mainly consist of abundant basalts and basanites, with subordinate hawaiites and basaltic andesites, mostly showing Na-alkaline affinity, whereas some of the older products show calc-alkaline signatures. As a whole, these volcanic rocks show LREE/HREE and HFSE/LILE ratios similar to those of OIB-like magmas. Some trace element and radiogenic isotope variations are observed amongst the less differentiated samples and they are explained by partial melting of a heterogeneous subcontinental mantle source at variable depths, mostly in the garnet stability field.The largest compositional variability observed, however, is attributed to differentiation processes, resulting in quite remarkable chemical and isotopic variations (e.g., 87Sr/86Sr = 0.70301-0.70529; 143Nd/144Nd = 0.51263- 0.51294; 206Pb/204Pb = 18.78-19.47; 207Pb/204Pb = 15.57-15.72; 208Pb/204Pb = 38.75-39.27). This implies the occurrence of open-system magma evolution, characterised by crystal fractionation at low pressure of mineral assemblage made up by olivine ± plagioclase ± clinopyroxene + apatite + Fe-Ti oxides, coupled with assimilation of crustal materials. The extent and the chemical modifications induced by this process are such that in some of the oldest and most evolved samples, the pristine Na-alkaline affinity is obliterated, and a secondary subalkaline signature is overprinted. This effect is less evident or negligible in more recent lavas, which preserve their primary features, being erupted in a well-developed fault system or in a long lasting, chemically homogeneous, magmatic feeding system.The magmatism studied here is quite unusual and not frequent in the frame of Na-alkaline intraplate volcanism, being characterised by abundant intermediate products and by evolutionary processes strongly affected by crustal contamination. In our view, this is due to the peculiar setting of the region, which is the locus of a significant mantle upwelling, accompanied by very limited or absent extensional rate.

The northern and northwestern margins of the Arabian Plate are a locus of a diffuse and long-lasting (early Miocene to Pleistocene) Na-alkali basaltic volcanism, sourced in the asthenosphere mantle. The upwelling asthenosphere at the Africa–Arabia margin produces very limited magma volumes in the axial zone. Therefore, portions of hot, fertile mantle continue their eastward migration and are stored at shallower depths under the 100-km thick Arabian lithosphere, which is much thinner than the African one (≈175 km): this causes the occurrence and 20-Ma persistence of magma supply under the study area. Erupted basalts sampled a continuous variation of the mantle source, with a striking correlation among temperature, pressure and isotopic composition shifting between two end members: a 100 km-deep, more depleted source, and a 60 km-deep, more enriched one. In particular, we observed an unusual variation in boron isotopes, which in the oceanic domain does not vary between more depleted and more enriched mantle sources. This study shows that, at least in the considered region, subcontinental mantle is more heterogeneous than the suboceanic one, and able to record for very long times recycling of shallow material.