This ppt includes brief information about metamorphic facies like, what is metamorphic facies? How it is classified? etc.

1. Introduction to
Metamorphic Facies
BY : HAROON MUHAMMED
MSC. GEOLOGY 2020
MIT - MAHE

2. metamorphic facies
 Eskola (1920) first prosed the concept of metamorphic facies for subdividing the
entire P-T range of metamorphism in number of selected domains, primarily on
the basis of occurrences of stable mineral assemblages developing in rocks of
different bulk composition. Where he introduced 8 facies.
 Later in (1958) Fyfe, Turner, Coombs et al. (1959) updated it by adding four more
facies.

3. Definition
 Metamorphic facies is a set of mineral assemblages
in metamorphic rocks formed under similar
pressures and temperature conditions.

4. Concept of Metamorphic facies
 Rocks of identical bulk composition having identical mineral assemblages
must have metamorphosed in identical P-T condition of metamorphism and
surely belong to same metamorphic facies.
 Rocks of a specific bulk chemical composition metamorphosed under
different facies condition will definitely produce different mineral
assemblages.

5.  In any given metamorphic setting there can be a variety of protolith exposed to
metamorphism. While these rocks will be exposed to the same range of pressure
and temperatures conditions within that setting, the metamorphic rock that
results will depend on the protolith. A convenient way to indicate the range of
possible metamorphic rocks in a particular setting is to group those possibilities
into metamorphic facies
 The unique sets of minerals that form in a reference material at one P and T can
be compared with assembages of minerals that formed in other rock
compositions under the same P and T conditions.

6. Metamorphic facies
 A metamorphic facies is not a single rock-type but a wide range of minerals that
form under similar P-T conditions. A general facies diagram was developed and
names of each facies are based on those mineral assemblages that develop when
a mafic bulk composition undergoes various P-T conditions.

8. Metamorphic Facies
 Zeolite Facies - zeolites
 Prehnite-Pumpelleyite Facies - Prehnite + pumpellyite
 Greenschist Facies – chlorite + albite + epidote + actinolite
 Amphibolite Facies -plagioclase + hornblende + garnet
 Granulite Facies - orthopyroxene + clinopyoxene + plag + hornblende + garnet
 Blueschist Facies - glaucophane +lawsonite or epidote (+ albite + chlorite)
 Eclogite Facies - pyroxene + garnet

9.  Albite-epidote hornfelsic Facies
 Hornblende hornfelsic Facies
 Pyroxene hornfelsic Facies
 Sanidinite Facies

10.  Diagram shows the different
metamorphic facies . The axes on the
diagram are temperature, depth and
pressure; the depth within the Earth will
determine how much pressure a rock is
under, so the vertical depth axis is also a
pressure axis. Each facies represents a
range of temperature and pressure
conditions where particular types of
metamorphic rocks will form.

11.  The different metamorphic facies are defined by the mineralogical composition of
a rock. When the temperature or pressure in a rock body change, the rock can
cross into a different facies.

12. Metamorphic facies
 Basalt are considered as reference material due to their abundance.
 A basalt metamorphosed during subduction to high pressures at low
temperatures recrystallizes into a rock containing glaucophane, lawsonite, and
albite; glaucophane is is blue to black in hand sample and lavender to blue under
the microscope. Because of their distinctive bluish coloration, such samples are
called blueschists.
 The same rock type metamorphosed at more moderate pressures and
temperatures in the range of 400–500 °C (752–932 °F) would contain abundant
chlorite and actinolite, minerals that are green both in hand sample and under the
microscope, and would be referred to as a greenschist.

13. Geothermal gradient
 The dashed lines represent the geothermal gradients in
different environments.
 Geothermal gradient describes how rapidly the temperature
increases with depth in Earth. In most areas the rate of increase
in temperature with depth is 30 °C/km.
 In volcanic areas (yellow dashed line), the geothermal gradient
is more like 40 to 50 °C/km, so the temperature rises much
faster as you go down.
 Along subduction zones, the cold ocean lithosphere keeps
temperatures low, so the gradient is typically less than 10
°C/km.

14. tectonic process and metamorphic facies
 Different types of tectonic processes produce different associations of
metamorphic facies in the field. For example, regions associated with subduction
of oceanic material beneath either oceanic crust or continental crust are
characterized by blueschist, greenschist, and eclogite facies rocks,
 whereas areas thought to reflect continent-continent collision are more typically
distinguished by greenschist and amphibolite facies rocks (see also subduction
zone).
 Still other regions, usually containing an abundance of intrusive igneous material,
show associations of low-pressure greenschist, amphibolite, and granulite facies
rocks.

15. Metamorphic facies series
 Akiho Miyashiro, develop the concept
of metamorphic facies series.
Miyashiro described the three facies
associations given above as high-
pressure, medium-pressure, and low-
pressure facies series.

16. Reference
 John D. Winter
 Brittanica(William S. Fyfe)
 K Bucher, University of Freiburg, Freiburg, Germany
 Tulane.edu

17. THANK YOU