Neogene volcanism in Elazig-Tunceli area (eastern Anatolia): geochronological and petrological constraints

The Elaz?? and Tunceli provinces in eastern Anatolia host acomplex succession of Miocene-Pleistocene effusive and explosivevolcanic rocks, divided into four distinct volcanic phases. The mostabundant and widespread products are the calcalkaline Mazgirtvolcanic rocks, characterized by wide Sr isotope variations (87Sr/86Sr~0.7054-0.7077) and narrower 143Nd/144Nd (~0.51246-0.51260) and Pbisotopes (e.g., 206Pb/204Pb ~18.89-19.13). New 40Ar-39Ar ages indicatethat Mazgirt volcanic activity occurred between ~16.3 and 15.1 Ma.The other three volcanic phases are represented by the Tunceli mildlyalkaline basaltic lavas (~11.4-11.0 Ma), the Pliocene Karakoçan (~4.1Ma) and Pleistocene Elaz?? (~1.9-1.6 Ma) Na-alkali basaltic lavas withclear OIB-like geochemical signature.Mazgirt volcanics can be subdivided on the base of mode ofemplacement into lava flows and lava domes units characterizedby petrographic, chemical and isotopic differences: lava flowsare calcalkaline, whereas lava domes mostly belong to a high-Kcalcalkaline series and are, on average, more LREE- and 87Sr-enriched.Lava domes are more porphyritic, with a phenocryst assemblagedominated by amphibole, whereas plagioclase and clinopyroxene arethe most abundant phenocryst phases in lava flows, pointing out thatevolution of dome magmas occurred in conditions of slightly higherpressure, favouring the crystallization of hydrous phases.The Karabak?r Formation, previously reported as late Miocene-Pliocene, encloses Mazgirt volcanics and is capped by Tunceli basalts.These new age data constrain the Karabak?r Formation emplacementfrom early to late Miocene.The evolution of this igneous activity mirrors the geodynamicframework of the region: the early-middle Miocene Mazgirt volcanicsrepresent arc volcanism related to Eurasia-Arabia convergence. Thelate Miocene Tunceli basalts postdate the onset of post-collisionaltectonics in Eastern Anatolia, whereas the Karakoçan and Elaz??volcanic rocks were emplaced after the initiation of strike-slip motionon the North Anatolian and East Anatolian Fault systems.