Petrology and geochemistry of Late Cenozoic volcanites in the Lesser Caucasus

The thesis deals with petrology and geochemistry of Late Cenozoic volcanites in the central part of the Mediterranean belt, including the Lesser Caucasus. In the learnt part of Lesser Caucasus there was conducted a formational analyses of the Late Cenozoic volcanites and their geochemical type was determined. Composition of the Late Cenozoic volcanic series was studied as well and typomorphic peculiarities of the rock-forming and accessory minerals and their indicator peculiarities in the evolution of the primary magmas.

On the base of the microelement composition of rocks and minerals, and also on the base of the determination of ratio of the distribution of trace elements there was determined a behavior of these elements in the process evolution of the primary magmas. There was determined, that the Late Cenozoic volcanites are enriched by largly ion rare elements, light REE and according to their petrogeochemical composition they are close to the rocks formed in the active continental margins and riftogenous structures. For the first time on the base of the study of composition of the melted inclusions, temperature of homogenization and also different geothermometers there were determined physical-chemical conditions of crystallization, composition of initial magmas of each formation and degree of melting of the mantle source and role the mantle metosomatizm during the formation of these magmas was assessed. It was determined, that evolution of fusion for the andesite-dacite-rhyolite and trachybasalt-trachyandesite formations is determined by the crystallization differentiation. The rocks of the trachyrhyolite formation were melted out of the granite-metamorphic layer of the earth crust under the influence of the basalt melt. There was made a conclusion the Late Cenozoic magmatism manifested itself in a complex geodynamic environment, i.e. mid alkaline and alkaline volcanism manifested themselves in a general compression (collision-orogenesis) after the formation of a high potassic calcalkaline series in the conditions of riftogenesis.

29.12.2010     Print  Print