epidote-amphibolite facies

epidote-amphibolite facies

[¦ep·ə‚dōt am′fib·ə‚līt ‚fā·shēz]
(petrology)
Metamorphic rocks formed under pressures of 3000-7000 bars and temperatures of 250-450°C with conditions intermediate between those that formed greenschist and amphibolite, or with characteristics intermediate.
References in periodicals archive ?
Therefore, the prograde metamorphism of these rocks is marked by the transition from the greenschist facies (chlorite + plagioclase + clinozoisite [+ o -] quartz [+ o -] titanite [+ o -] graphite and actinolite + clinozoisite + quartz + plagioclase [+ o -] epidote [+ o -] titanite) through the epidote-amphibolite facies (actinolite + hornblende + epidote + clinozoisite + zoisite + quartz + plagioclase [+ o -] garnet [+ o -] titanite [+ o -] rutile [+ o -] muscovite) to the amphibolite facies (hornblende + garnet + plagioclase [+ o -] quartz).
These are strongly deformed highly tectonized and are metamorphosed mainly to greenschist facies and lesser extent to epidote-amphibolite facies.
The rocks of the CVG are highly tectonized and metamorphosed to mainly greenschist and epidote-amphibolite facies and have the development of altered/sheared zones along local faults within these rocks.
The first one corresponds to epidote-amphibolite facies, represented by hornblende + epidote group minerals + quartz + albite [+ or -] garnet (Figure 3c).
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].
This is supportd by the mineralogy of greenschist facies that is found among the mineral assemblages of the amphibolite and epidote-amphibolite facies, such as chlorite + actinolite + epidote minerals + quartz (mineralogy of greenschist facies), between hornblende + epidote minerals + quartz + albite [+ or -] garnet (mineralogy of epidote-amphibolite facies) in the hornblende schists (Figures 4d), and the chlorite + muscovite + epidote minerals + plagioclase (albite) + quartz (mineralogy of greenschist facies) between the hornblende + garnet + plagioclase [+ or -] quartz (amphibolite facies) in the garnet amphibolites (Figure 3f).
The maximum conditions are followed by a decrease in temperature and pressure, which is shown by mineral assemblages that were retrograded from amphibolites and epidote-amphibolite facies towards greenschist facies.
The basement comprises deformed and epidote-amphibolite facies metamorphosed rocks ranging from mafic to granodioritic composition.
During the collision it may have experienced deformation and metamorphism in epidote-amphibolite facies.