The document describes the different metamorphic facies defined by their mineral assemblages under varying pressure and temperature conditions within the Earth's crust and upper mantle. It outlines the key facies including zeolite, prehnite-pumpellyite, greenschist, amphibolite, granulite, blueschist, eclogite, albite-epidote hornfels, hornblende hornfels, pyroxene hornfels, and sanidinite facies. Each facies is characterized by index minerals and typical mineral assemblages that reflect the prevailing metamorphic conditions.

1. Diagram showing metamorphic facies in
pressure- temperature space. The domain of
thegraph corresponds to circumstances within the Earth's crust and
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2. Metamorphic
facies
 1-Eclogite
 2-Blueschist
 3-Greenschist
 4-Prehnite-
 5-Pumpellyite
 6-Zeolite
 7-Granulite
 8-Amphibolite
 9-Hornfels
 10-Sanidinite
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3. Metamorphic facies
 The metamorphic facies are groups of
mineral compositions in metamorphic
rocks, that are typical for a certain field
in pressure-temperature space. Rocks
which contain certain minerals can
therefore be linked to certain tectonic
settings.
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4. Historic definition
 The metamorphic facies are groups of mineral compositions
in metamorphic rocks, that are typical for a certain field in
pressure-temperature space
 The name facies was first used for specific sedimentary
environments in sedimentary rocks by Swiss geologist Amanz
Gressly in 1838.
 Analogous with these sedimentary facies a number of
metamorphic facies were proposed in 1920 by Finnish
petrologist Pentti Eskola.
 Eskola's classification was refined in the 1970s by New-
Zealand geologist Francis John Turner.
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5. Underlying principles
 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
and some minerals become stable while others
become unstable or metastable
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6. Index minerals
 Every metamorphic facies has some index minerals by
which it can be recognized.
 Very typical index minerals are the polymorphs of
aluminosilicate (Al2SiO5, all are nesosilicates).
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7. Metamorphic facies
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and their mineral
assemblages
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8. Zeolite facies (LP/LT)
 The zeolite facies is the metamorphic
facies with the lowest metamorphic
grade.
 The facies is named for zeolites,
strongly hydrated tectosilicates
 It can have the following mineral
assemblages:
 heulandite + analcime + quartz ± clay
minerals
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9. PREHNITE-PUMPELLYITE-FACIES
(LP/LT)
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 The prehnite-pumpellyite facies is a little higher in pressure and
temperature than the zeolite facies
 . The prehnite-pumpellyite is characterized by the mineral
assemblages
 prehnite + pumpellyite + chlorite + albite + quartz
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10. GREENSCHIST FACIES (MP/MT)
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The greenschist facies is at medium pressure and
temperature.
The facies is named for the typical schistose texture
of the rocks and green colour of the minerals
chlorite, epidote and actinolite.
Characteristic mineral assemblages are:
 chlorite + albite + epidote ± actinolite, quartz
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11.  The amphibolite facies is a facies of medium
pressure and average to high temperature.
 It is named after amphiboles that form under
such circumstances.
 It has the following mineral assemblages:
 hornblende + plagioclase ± epidote, garnet,
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12. Granulite facies (MP/HT)
 The granulite facies is the highest grade of metamorphism at
medium pressure.
 The depth at which it occurs is not constant.
 A characteristic mineral for this facies and the pyroxene-
hornblende facies is orthopyroxene.
 orthopyroxene + clinopyroxene + hornblende
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13.  The blueschist facies is at relatively low
temperature but high pressure, such as occurs in
rocks in a subduction zone.
 The facies is named after the schistose character of
the rocks and the blue minerals glaucophane and
lawsonite. mineral assemblages:
 glaucophane + lawsonite + chlorite + sphene ±
epidote
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14. Eclogite facies (HP/HT)
 The eclogite facies is the facies at the highest pressure
and high temperature.
 It is named for the metabasic rock eclogite.
 The mineral assemblages:
 omphacite + garnet ± kyanite, quartz,
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15. ALBITE-EPIDOTE-HORNFELS FACIES (LP/LT-MT)
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 The albite-epidote-hornfels facies is a facies at low pressure
and relatively low temperatures.
 It is named for the two minerals albite and epidote, though they
are stable in more facies.
 Hornfels is a rock formed in contact metamorphism, a process
that characteristically involves high temperatures but low
pressures/depths.
 albite + epidote + actinolite + chlorite + quartz
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16.  The hornblende-hornfels facies is a facies with
the same low pressures but slightly higher
temperatures as the albite-epidote facies.
 Though it is named for the mineral hornblende,
 The hornblende-hornfels facies has the
following mineral assemblages:
 hornblende + plagioclase ± diopside,
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17. Pyroxene-hornfels facies (LP/MT-HT)
 The pyroxene-hornfels facies is the contact-
metamorphic facies with the highest
temperatures and is, like the granulite facies
 Characterized by the mineral orthopyroxene.
 Mineral assemblages:
 orthopyroxene + clinopyroxene + plagioclase ±
olivine or quartz
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18. Sanidinite facies (LP/HT)
 The sanidinite facies is a rare facies of extremely high
temperatures and low pressure.
 It can only be reached under certain contact-
metamorphic circumstances.
 Due to the high temperature the rock experiences
partial melting and glass is formed.
 This facies is named for the mineral sanidine.
 cordierite + mullite + sanidine + tridymite (often altered
to quartz) + glass
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19. References
 Eskola, Pentti Eelis, 1920: "The mineral facies of rocks"
 Phillpots, Anthony R., 1990: Principles of Igneous and
Metamorphic Petrology
 Duff, P. McL. D., 1996; Holmes' Principles of Physical
Geology
 Visser, W.A., 1980; Geological Nomenclature
 Metamorphic facies by Dave Waters
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20. ABID ALI
Geologist From University of Sargodha
Pakistan
DECENT572@GMAIL.COM
 #no.0923346965614
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