Research Information System
World Multidisciplinary Earth Sciences Symposium 2016, Prague, Czech Republic, 5 - 09 September 2016, pp.180, (Summary Text)
Pliocene basaltic volcanism in the East Anatolia (Turkey) erupted form both extensional fractures and volcanic centers in the East Anatolia High Plateau created by collision of the Arabian with Eurasian plate. Our recent studies and literature studies on the Eastern Anatolian volcanism suggest that volcanic activity peaked in the Pliocene and continued in the same productivity throughout Quaternary. In order to better understand the spatial and temporal variations in Pliocene basaltic volcanism, we have started to study basaltic volcanism in the East Anatolia within the framework of a TUBITAK project (project number:113Y406). Geochronological dating results (Ar-Ar and K-Ar) indicate that age of this magmatic activity range between 6-3.5 Ma. Volcanic products contain alkaline and subalkaline lavas, ranging in compositions from basalts to andesite and trachyandesite. EC-AFC model calculations suggest that basaltic samples were unaffected from combined processes of the fractional crystallization and crustal contamination but evolved lavas includes to 2-7 % assimilation rates. Enrichment of large ion lithophile elements (LILE) and light rare earth elements (LREE) relative to high strength filed elements (HFSE) and higher 87Sr/86Sr, Pb isotopic ratios and lower 144Nd/143Nd of the basaltic samples indicates that are derived from mantle source region enriched by melts derived from subducted sediment rather than AOC melts and fluids. Results of the melting model indicate that there was a marked variation both in the source mineralogy (from ~70% to 10% garnet) and the degree of melting (i.e. F from 0.8 % to 6 %) during the formation of Pliocene basaltic lavas. The percentage of spinel seems to have increased in the lerzolitic mantle source of the basaltic lavas. Accordingly, chemical character of the lavas turned from alkaline to subalkaline in time. We argue that the temporal increase of spinel contribution and the melting degree in the mantle source region was responsible for transition from alkaline to subalkaline character in the lava chemistry. This can be explained by the variations in the depth of and degree of melting in the mantle source region, possibly related to the lithospheric extensional nature and partial delamination of lithospheric mantle of Eastern Anatolia during the Pliocene.
Key words: East Anatolia; Pliocene; basaltic volcanism; lithospheric mantle.