In contrast, amphibolitized eclogites are strongly overprinted by amphibolite facies
minerals that omphacite only survived in relics.
The conditions of metamorphism of the metabasites of the Arquia Complex in all lithotypes studied along the Central Cordillera reached the amphibolite facies
for the garnet-amphibolite without garnet and greenschist facies for the epidote actinolite schists.
Their protolith corresponds to fine- to mediumgrained pelitic sediments, which were affected by a metamorphism reaching the amphibolite facies
. They show a porphyroblastic texture with lepidoblastic matrix, which is defined by the alignment of muscovite and graphite.
The Arquia Group is formed by garnet amphibolites, greenschists and mica schists, from basic, volcano-sedimentary and pelitic protoliths, respectively, metamorphosed under greenschist and amphibolite facies
conditions (Restrepo & Toussaint, 1976; Arias & Caballero, 1978; Sanchez, 1988; Rios Reyes, et al.., 2008; Marin, 2009; Ruiz-Jimenez, et at, 2012).
The dominant lithology encountered during the drilling was a coarse-grained metamorphic amphibolite facies
The other missing sample (12) cannot be plotted on these diagrams because it is at amphibolite facies
as a result of contact metamorphism by a Devonian intrusion, as discussed below.
The supracrustal rocks are generally metamorphosed to amphibolite facies
, less commonly to granulite facies, and rarely to greenschist facies.
On the basis of geophysical and petrological studies, the Estonian basement can be divided into two major geological units--North Estonian amphibolite facies
and South Estonian granulite facies complexes, which are separated from each other by a tectonical boundary (Paldiski-Pskov shear zone) and include six petrological-structural zones: the Tallinn, Alutaguse, Johvi, West Estonian, Tapa, and South Estonian zones (Fig.
From our studies, we determined that the most common assemblage at Dark Ridge is olivine + talc + tremolite + chlorite + chromite, which indicates metamorphism in the amphibolite facies
. The samples suggest higher temperature assemblages once existed, possibly granulite facies.
Rocks of the northern structural-formational zone of the Pechenga structure are metamorphosed at the prehnite-pumpellyite to middle stages of the amphibolite facies
(Zagorodny et al., 1964; Petrov, 1999).
These are generally deformed and exhibit greenschist facies metamorphism with the development of epidotes- amphibolite facies
metamorphism at places.
It is mainly composed by metapelitic rocks with minor intercalated psammitic, semipelitic, metabasic and metacarbonate rocks, which were affected by a metamorphism to upper amphibolite facies
regional grade during the Caledonian orogeny, and reveals a very complex tectonic and metamorphic history.