ВУЛКАНИТЫ С ВКРАПЛЕННИКАМИ МАГМАТИЧЕСКОГО ЭПИДОТА ИЗ ОКРЕСТНОСТЕЙ ЕКАТЕРИНБУРГА, УРАЛ

Abstract

For the first time, subvolcanic dikes of andesitcs and dacites containing intratelluric phenocrysts of magma-tic cpidote (Ps 16-20), garnet, titanite and other minerals, have been discovered and described at the Urals. Calculated P-T conditions of equilibrium, carried for hornblende, garnet, epidote phenocrysts, has show that they were formed from the rich-in-water melt under pressure of 9-10 kbar, temperature about 800 °C and high fuga-city of oxygen (/02 < -12)- Phenocrysts were rapidly carried by this melt up to the surface, it is indicated by their sound safety without reactionary margins. The andesidacite magma was probably formed in conditions of a local extension of the earth crust in the abovc-subduction zone of the Middle Urals continental margin in the Early-Carboniferous time. Unusual geochemical characteristics of the rocks (low concentration of REE, positive anomaly of Sr, Ba, Zr, Hf, Ti) correspond to that type of tectonic setting.