Chemical composition of the actinolite-hornblende assemblage as indicator for the P-T metamorphic conditions in chlorite-amphibole schists and metadiabases, Vrteska, Plackovica Mt., Eastern Macedonia

Abstract

Microscopic and electronic microprobe studies carried out on the chlorite-amphibole schists and the metadiabases from the vicinity of Vrteska determined an actinolite, Mg-hornblende, biotite, epidote, chorite, albite, calcite, quartz, and ilmenite assemblage. The metamorphic mineral assemblage and structural-textural characteristics indicate that these rocks metamorphosed in conditions of regional dynamothermal metamorphism in a Barovian type series of facies which, according to the degree of metamorphism, corresponds to the transition from quartz-albite-epidote-biotite to quartz-albite-epidote-almnadine subfacies. The chemical composition of actinolite and hornblende indicate that the rocks under investigation metamorphosed in conditions of prograde metamorphism at T = 400-500°C and P = 2-5 kbar.