The high-pressure assemblages at Milos, Greece

Abstract

Metamorphic rocks at Milos are known in small outcrops beneath the volcanic formations, as xenoliths in the Traphores volcanic breccia and as pebbles in the Paleochora Quaternary deposits. These rocks seem to belong to three different metamorphic units which probably have intricate relationships in the basement: — the “eclogites unit” shows garnetjadeite or garnet-omphacite primary associations, with apparently late crystallization of lawsonite phenoblasts an recrystallization features at relatively low temperatures; — the “glaucophane schist unit” exhibits Jadeite+quartz or glaucophane+lawsonite primary mineralogy; — the “greenschist facies unit” shows low-pressure main assemblages, most generally developed after high-pressure events. The two former units involve tholeiitic meta-igneous rocks, having been spilitized before metamorphism; they generally suffered more or less advanced recrystallization features in the low-pressure field of the greenschist facies. The third unit shows only meta-sedimentary rocks, with the sole exception of one single meta-doleritic pebble having calk-alkaline affinities.