Geochemical aspects of the formation of Neogene volcanism in the central part of the Lesser Caucasus

Abstract

The article considers the formation of Neogene volcanism in the central part of the Lesser Caucasus on the basis of geochemical features. It was found that in the andesite-dasite-rhyolite association rocks, where volcanism is expressed, light lanthanides predominate over weight, and therefore the La/Sm, La/Yb ratios are high. In medium rocks (quartz latites, andesites) the Eu/Eu* ratio is close to unity (Eu/Eu* = 0.94-1.05), in more acidic rocks the weak Eu-minimum (Eu/Eu* = 0.58-0 ,63) and indicates the fractionation of plagioclase in the formation of acidic rocks. Enrichment melts and fluids with a relatively high melting point caused the increase of Ba/Y, Rb/Y, Th/Yb, Nb/Y, Nb/Yb ratios in the association rocks and their enrichment with Ba, Sr, rare earth elements. It was concluded that the source of the enriched mantle played a key role in the formation of andesite-dasite-riolite association rocks of the central part of the Lesser Caucasus. Keywords: Central part of the Lesser Caucasus, Neogene volcanism, distribution of rare earth and rare elements, source of enriched mantle.