Introduction to Metamorphic Petrology Recommended Textbook J D
Introduction to Metamorphic Petrology Recommended Textbook: J. D. Winter (2001) An Introduction to Igneous and Metamorphic Petrology: Prentice Hall Pub.
Scope of Metamorphic petrology Ø 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. Ø 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. ØMetamorphism is commonly isochemical (except for volatile components, e. g. , H 2 O, CO 2). Where the system is open, the process is referred to as metasomatism.
Metamorphic Reactions Dehydration KAl 3 Si 3 O 10(OH)2 + Si. O 2 = KAl. Si 3 O 8 + Al. Si 2 O 5 + H 2 O Muscovite Quartz K-Feldspar Sillimanite Decarbonation Ca. CO 3 + Si. O 2 = Ca. Si. O 3 + CO 2 Calcite Quartz Wollastonite Solid-Solid Na. Al. Si 3 O 8 = Na. Al. Si 2 O 6 + Si. O 2 Albite Jadeite Quartz
Prograde and Retrograde Metamorphism Retrograde Path Prograde Path
Metamorphic Facies Ø A metamorphic facies is a domain of Pressure-Temperature Space Ø Metamorphic facies are defined by characteristic mineral assemblages specific to particular bulk-rock compositions
Conditions of Metamorphism and Metamorphic Facies
Types of Metamorphism Ø Contact or Thermal Metamorphism Ø Regional Metamorphism n Orogenic Metamorphism n Burial Metamorphism n Ocean Floor Metamorphism Ø Hydrothermal Metamorphism (Alteration) Ø Impact or Shock Metamorphism
Contact or Thermal Metamorphism
Contact Metamorphism of 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 s 1 · · · s 1 > s 2 = s 3 foliation and no lineation s 1 = s 2 > s 3 lineation and no foliation s 1 > s 2 > s 3 both foliation and lineation
Onset of Orogenic Metamorphism Shale B n i d ed Slate g e a e l C g va Bedding
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)2 Al 4 Si 5 O 18 (Porphyroblasts) Staurolite (Fe, Mg)2 Al 9 Si 4 O 23(OH) Garnet (Fe, Mg)3 Al 2 Si 3 O 12
The Aluminosilicates Al 2 Si. O 5 Andalusite Kyanite 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 + H 2 O Muscovite Quartz Sillimanite K-feldspar
Metamorphic Facies and Isograds Oslo: K-Feldspar- Cordierite Orijärvi: Biotite-muscovite 2 KMg 3 Al. Si 3 O 10(OH)2 + 6 KAl 2 Al. Si 3 O 10(OH)2 (Ms) + 15 Si. O 2 = 3 Mg 2 Al 4 Si 5 O 18 + 8 KAl. Si 3 O 8 + 8 H 2 O
Facies Series
Pressure-Temperature-Time Paths
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