Metamorphic Facies

metamorphic facies

[¦med·ə¦mȯr·fik ′fā·shēz]
All rocks of any composition that have reached chemical equilibrium with respect to certain ranges of pressure and temperature during metamorphism, characterized by the stability of specific index minerals. Also known as densofacies.

Facies, Metamorphic


an ensemble of metamorphic rocks of varying composition that correspond to specific conditions of formation relative to the primary factors of metamorphism, namely, temperature, geostatic pressure, and the partial pressures of the volatile components in the fluids involved in metamorphic reactions among minerals (seeMETAMORPHISM). Metamorphic facies are usually classified according to the names of the main types of basic rocks that are stable in each facies (see Figure 1). Examples include the greenschist and glaucophane schist facies (low temperature, intermediate and high pressures), epidote-amphibolite and amphibolite facies (intermediate temperature, intermediate and high pressures), granulite and eclogite facies (high temperature and pressure), and sanidinite and pyroxene-hornfels facies (very high temperature and very low pressure). Metamorphic facies are also designated according to the names of metamorphic minerals and the mineral sequences that are typical of the corresponding regions of thermodynamic stability. Examples include the garnet-cordierite, hypersthene-sillimanite, staurolite, andalusite, sillimanite, and kyanite facies.

Figure 1. Metamorphic facies of rocks (after Marakushev, 1973): (1) slates, porphyries; (2) phyllites, calcite and chlorite schists, spilites, zeolitic rocks; (3) phyllites, glaucophane and chlorite schists containing jadeite and lawsonite; (4) two-mica schists and gneisses, actinolite schists, epidote amphibolites; (5) two-mica almandine schists, gneisses, gedrites, amphibolites, glaucophane schists, eclogites; (6) cordierite-biotite and pyroxene-amphibolite hornfelses; (7) biotite-sillimanite and andalusite gneisses, pyroxene amphibolites; (8) garnet (almandine-pyrope) gneisses, sillimanite gneisses, hyper-sthene gneisses, pyrozene amphibolites, eclogites; (9) almandine-pyrope and hypersthene-kyanite gneisses, kyanite eclogites; (10) cordierite-andalusite and pyroxene-plagioclase hornfelses; (11) hyper-sthene-cordierite gneisses, two-pyroxene schists; (12) almandine-pyrope and hyperstene-cordierite gneisses, two-pyroxene schists; (13) almandine-pyrope and hypersthene-sillimanite gneisses, eclogites; (14) sanidinites, larnite and spurite rocks, buchites

Depending on the types of mobile belts and the stages in the development of the belts, metamorphism occurs under conditions corresponding to different metamorphic facies. The relatively low-temperature metamorphism of the greenschist glaucophane schist, or zeolite facies is characteristic of the early preorogenic stages in the development of geosynclines. In the later orogenic stages, rocks undergo high-temperature metamorphism, primarily of the amphibolite and granulite facies. The high-temperature metamorphism is associated with the processes by which granitoids are formed in mobile belts. The pyroxene-hornfels and sanidinite facies are limited to contacts with plutonic rock bodies that are intruded in the postorogenic stages in the development of mobile belts or into cratonic structures.

In 1966, a map of the metamorphic facies of the USSR on a scale of 1:7,500,000 was published in the USSR. It was compiled under the direction of V. S. Sobolev at the Siberian Division of the Academy of Sciences of the USSR.


Fatsii metamorfizma. Moscow, 1970.
Marakushev, A. A. Petrologiia metamorficheskikh gornykh porod. Moscow, 1973.
Winkler, H. Genezis metamorficheskikh porod. Moscow, 1969. (Translated from English.)
Eskola. P. The Mineral Faciès of Rocks. Christiania, 1920.


References in periodicals archive ?
Moreover, specific data of rock physical properties of different metamorphic facies will be useful in technical applications.
These rocks are presented by metamorphic complexes from prehnite-pumpellyite to amphibolite metamorphic facies. The location of the sampling sites is shown on the map of the Pechenga formation, Figure 1, and on the diagram of metamorphic facies, Figure 2 (Glebovitsky, 1973).
Cite this article as: Gorbatsevich F F, Trishina O M: Petrophysical properties of the Pechenga rocks of the different metamorphic facies. Acta Geodyn.
The concepts of metamorphic facies and subfacies were modified after Smulikowski et al.
The light gray area represents the metamorphic facies. An anticlockwise PT path (red arrow) followed by the Silgara metapelitic rocks typical of a region that has undergone contact metamorphism.
These particular metamorphic facies are characterized most effectively by specific assemblages unique to metabasite in the chemical system CaO-MgO-[Al.sub.2][O.sub.3]-Si[O.sub.2]-[H.sub.2]O (CMASH; Table 1).
Figure 7 shows the areal distribution of the mafic volcanic samples for which the metamorphic facies were determined.