The Evidence of Cumulate Crystallization and Local Development of the Eclogite Facies Metamorphism in Olivine Gabbro of the Marun-Key Complex (Polar Urals, Russia)

Resumo

This work presents the results of a detailed petrological study of olivine gabbro transformed to a different extent during the eclogite facies metamorphism. The textural features of cumulate crystallization in the rock at the magmatic stage are presented. Due to the significant transformations during eclogite facies metamorphism plagioclases were replaced by a fine-grained aggregate of high-pressure mineral paragenesis. Corona textures are developed along the boundaries of plagioclase (felsic) domains at the contacts with (Fe, Mg)-minerals during eclogite facies events. Mineral thermobarometry and phase equilibrium modeling provide P–T metamorphic conditions in relatively narrow temperature and pressure ranges: T = 680 ± 60°C and Р = 2.2 ± 0.4 GPa. This is in a good agreement with the previously established formation conditions of eclogites and garnet–amphibole peridotite from the same complex.