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 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

Subduction Metamorphism

Paired Metamorphic Belts Amphibolite Facies Blueschist Facies

Subduction 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