A set of metamorphic mineral assemblages that is produced by the metamorphism of a wide range of initial rock types under the same metamorphic conditions, and is typically characterized by the develop-ment of the mineral assemblage albite–epidote–hornblende in rocks of basic igneous composition such as basalts. Other rocks of contrasting composition, e.g. shales or limestones, would each develop their own specific mineral assemblage, even though they are all being metamorphosed under the same conditions. The variation of mineral assemblage with starting rock composition reflects a particular range of pressure, temperature, and P(H2O). Experimental studies of mineral P–T stability fields indicate that the facies represents a range of low-pressure, moderate-temperature conditions. See amphibolite.
Subjects: Earth Sciences and Geography.