Then, a progressive metamorphism in these rocks is marked by the passing of greenschist facies mineralogy [actinolite + chlorite + quartz + plagioclase (albite) + epidote minerals [+ or -] muscovite [+ or -] calcite] to epidote-amphibolite facies mineralogy [hornblende + epidote minerals + quartz + albite [+ or -] garnet], and finally to
amphibolite facies mineralogy [hornblende + garnet + plagioclase [+ or -] quartz].
The graphical analysis of greenschist to
amphibolite facies mineral assemblages in metabasites.
The rocks of the Alutaguse zone have metamorphosed under the conditions of the
amphibolite facies. In some places (Sonda-Uljaste and Haljala) the rocks show evidence of granulite facies metamorphism.
The rock samples of
amphibolite facies show a clear dissimilarity in the acoustopolarigram shape from that of the rocks of prehnite-pumpellyite, greenschist and epidote-amphibolite facies.
It crosscuts the PPZ and extends into the NEGL, the
amphibolite facies terrain.
These rocks comprise mylonitic peridotite and sub-ophiolitic metamorphic rocks that range from garnetiferous amphibolites facies to
amphibolite facies to greenschist facies and un- metamorphosed sediments.
However, in many places retrograde assemblages have formed in the conditions of the
amphibolite facies.
This lower
amphibolite facies metamorphism overprints, in many samples, a pre-existing epidote-hornfels or greenschist assemblage containing epidote + variably sericitised plagioclase + actinolite [+ or -] biotite.
The regional metamorphic mineral assemblages indicate upper
amphibolite facies metamorphism.
Drill core F-156 penetrates volcanic-sedimentary biotite gneisses of
amphibolite facies origin in Eastern Estonia.