Geological and geochemical evolution of the quaternary süphan stratovolcano, Eastern Anatolia, Turkey: Evidence for the lithosphere-asthenosphere interaction in post-collisionalvolcanism

Abstract

The Süphan stratovolcano is one of the major Quaternary eruption centers of post-collisional volcanism in eastern Anatolia, located in the zone of convergence between the Arabian and the Anatolian plates. We document the geological and geochemical evolution of Süphan in terms of volcanostratigraphy, geochronology (40Ar-39Ar), isotope composition (Sr, Nd, Pb) and bulk-rock geochemistry. Our new 40Ar-39Ar data, along with previously published K/Ar ages, indicate an age of 0·76-0·06Ma for the eruptive products, which extend over an area of ~2000 km2.The products of Süphan include transitional mildly alkaline to calc-alkaline lavas, domes and pyroclastic rocks ranging in composition from basalt to rhyolite. MELTS modeling suggests that the majority of the Süphan magmas with SiO2 contents between ~57 and ~65 wt % are the products of isobaric-isenthalpic mixing of basaltic trachyandesitic and rhyolitic magmas at a crustal pressure of 0·5 kbar. Energyconstrained assimilation and fractional crystallization modeling of trace element and isotope compositions points to 2-10% (upper) crustal contamination that accompanied differentiation. Large ion lithophile element enrichment and the presence of negative high field strength element anomalies in primitive mantle-normalized trace element patterns suggest a mantle source that was modified by subducted sediments. Light to heavy and medium to heavy rare earth element ratios and partial melting models suggest the derivation of the eastern Anatolian parental magmas from variable mixing of lithospheric and asthenospheric melts. Unlike the commonly accepted models for post-collisional volcanism that envisage an increasing contribution from asthenospheric melts with time, melting degree and contribution of the lithospheric mantle seem to have increased from Miocene-Pliocene to Quaternary times in eastern Anatolia. © The Author 2013. Published by Oxford University Press. All rights reserved.