Introduction to Metamorphic Petrology
Recommended Textbook: J.D. Winter (2001)
An Introduction to Igneous and Metamorphic
Petrology: Prentice Hall Pub.
Scope of Metamorphic petrology
 Metamorphic petrology is the study of the subsolidus
changes that a rock undergoes when exposed to
physicochemical conditions different from those prevailing
near the surface of the Earth.
 Metamorphism produces changes in mineral assemblages
and textures that reflect re-equilibration of the rock to the
new physicochemical conditions, i.e., minimization of the
energy of the system.
Metamorphism is commonly isochemical (except for
volatile components, e.g., H2O, CO2). Where the system is
open, the process is referred to as metasomatism.
Metamorphic Reactions
Dehydration
KAl3Si3O10(OH)2 + SiO2 = KAlSi3O8 + AlSi2O5 + H2O
Muscovite
Quartz
K-Feldspar Sillimanite
Decarbonation
CaCO3 + SiO2 = CaSiO3 + CO2
Calcite Quartz Wollastonite
Solid-Solid
NaAlSi3O8 = NaAlSi2O6 + SiO2
Albite
Jadeite
Quartz
Prograde and Retrograde Metamorphism
Retrograde Path
Prograde Path
Metamorphic Facies
 A metamorphic facies is a domain of
Pressure-Temperature Space
 Metamorphic facies are defined by
characteristic mineral assemblages specific
to particular bulk-rock compositions
Conditions of Metamorphism and
Metamorphic Facies
Types of Metamorphism
Contact or Thermal Metamorphism
 Regional Metamorphism
 Orogenic Metamorphism
 Burial Metamorphism
 Ocean Floor Metamorphism
 Hydrothermal Metamorphism
(Alteration)
 Impact or Shock Metamorphism

Contact or Thermal Metamorphism
Contact Metamorphism of Limestone
Limestone
Marble
Diabase
Marble
Limestone
Thermally Metamorphosed Clastic Sediments
Plagioclase
Garnet
Pyroxene
Orogenic Metamorphism
Orogenic Metamorphism
Orogenic Metamorphism and differential stress
Foliation (or Cleavage) and Lineation
s1
 s1 > s2 = s3  foliation and no lineation
 s1 = s2 > s3  lineation and no foliation
 s1 > s2 > s3  both foliation and lineation
Onset of Orogenic Metamorphism
Shale
Slate
Progressive Orogenic Metamorphism
Phyllite
Schist
Progressive Orogenic Metamorphism
Gneiss
Anatexis
Anatexis or Partial Melting of Metasedimentary
Rocks (Migmatites)
Burial Metamorphism
Burial Metamorphism
Subduction Metamorphism
Paired Metamorphic Belts
Amphibolite Facies
Blueschist Facies
Subduction Metamorphism
Ocean Floor Metamorphism
Ocean Floor Metamorphism
Metamorphic Isograd Mapping (Index Minerals)
Metamorphic
Index Minerals
Cordierite
(Mg,Fe)2Al4Si5O18
(Porphyroblasts)
Staurolite
(Fe,Mg)2Al9Si4O23(OH)
Garnet
(Fe,Mg)3Al2Si3O12
The Aluminosilicates Al2SiO5
Andalusite
Kyanite
Sillimanite
Sillimanite
Metamorphic Isograds and P-T Paths
Barrow Zones
Buchan Zones
Aluminosilcates as Indicators of
Metamorphic Grade
Metamorphic reactions and metamorphic grade
Muscovite + Quartz = K-feldspar + sillimanite + H2O
Muscovite
Quartz
Sillimanite
K-feldspar
Metamorphic Facies and Isograds
Oslo: K-Feldspar- Cordierite
Orijärvi: Biotite-muscovite
2 KMg3AlSi3O10(OH)2 + 6 KAl2AlSi3O10(OH)2 (Ms) + 15 SiO2
= 3 Mg2Al4Si5O18 + 8 KAlSi3O8 + 8 H2O
Facies Series
Pressure-Temperature-Time Paths