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 ?
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.
One mafic volcanic breccia block, sampled in the northeastern part of the melange yields evidence for lower epidote-amphibolite facies metamorphism prior to emplacement in the melange.