amphibolite facies


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Related to amphibolite facies: Blueschist Facies, Granulite Facies, Metabasites

amphibolite facies

[am′fib·ə‚līt ′fā‚shēz]
(petrology)
Rocks produced by medium- to high-grade regional metamorphism.
References in periodicals archive ?
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 Tallinn zone vary from mafic amphibolite facies metavolcanites to metasediments represented by amphibole gneisses, biotite-plagioclase gneisses, quartz-feldspar gneisses, mica gneisses, and minor sulphide-graphite gneisses and magnetite quartzites (Jagala complex).
The metamorphic rocks on the northwestern part of The sole rocks of JTGM consist of a basal part of the foliated peridotite and the sub-ophiolitic metamorphic rocks; garnet amphibolite facies grades downwards into amphibolite facies and greenschist facies with calcitemarble inter-layers which exhibits decreasing metamorphic grade and decreasing intensity of deformation downward from the stratigraphic base of the ultramafic rocks.
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 Leo Pargil shear zone is a zone of distributed ( greater than 500 m) deformation that consistently records top-down-to-the-west -northwest sense of shear and juxtaposes amphibolite facies rocks in the footwall with low-grade metasedimentary rocks in the hanging wall.
The study sector of the MCT zone recorded a metamorphic event at higher PT conditions up to amphibolite facies followed by a lower grade metamorphism and deformation acquired during exhumation reaching the PT conditions of 2-4 Kbar and 300-400degC at nearly 14-17 Ma determined through Ar/Ar datings on white micas and biotites recrystallized along the mylonitic foliation pointed out a cooling age for the MCTZ (Montomoli et al.
Garnet porphyroblasts from upper amphibolite facies show a textural unconformity defined by inclusion-free rims, which coincides with changes in the garnet composition for both major a nd trace elements, including Cr.
This low-temperature shearing event is associated with chloritization, hematization, and illitization/seritization of the amphibolite facies gneisses, and disseminated silver and pyrite mineralization.