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Metamorphic rocksMetamorphic rocks
TodayTodayUpdates:Updates:
MidtermMidterm
Lecture outline:Lecture outline:
- Types of metamorphismTypes of metamorphism
- Prograde and retrogradePrograde and retrograde
Types of MetamorphismTypes of Metamorphism
Different approaches to classificationDifferent approaches to classification
1. Based on 1. Based on pressure/stress and temperaturepressure/stress and temperature:: Dynamic Metamorphism: deviatoric stressDynamic Metamorphism: deviatoric stress Thermal Metamorphism: increase in TThermal Metamorphism: increase in T Dynamo-thermal Metamorphism: P+T changeDynamo-thermal Metamorphism: P+T change
Types of MetamorphismTypes of Metamorphism
2. Based on 2. Based on settingsetting Contact MetamorphismContact Metamorphism Regional MetamorphismRegional Metamorphism Hydrothermal MetamorphismHydrothermal Metamorphism Fault-Zone Metamorphism Fault-Zone Metamorphism Impact or Shock MetamorphismImpact or Shock Metamorphism
Contact MetamorphismContact Metamorphism
The size and shape of an aureole is controlled by:The size and shape of an aureole is controlled by:
Pluton:Pluton:
Country rocks:Country rocks:
Size Shape Orientation
Temperature Composition
CompositionComposition Depth and metamorphic grade prior to intrusionDepth and metamorphic grade prior to intrusion Permeability Permeability
Contact Metamorphism 2Contact Metamorphism 2
Contact -- rock typesContact -- rock types
Contact -- rock types 2Contact -- rock types 2
Regional MetamorphismRegional Metamorphism
Regional/Orogenic MetamorphismRegional/Orogenic Metamorphism
Regional/Orogenic Metamorphism 2Regional/Orogenic Metamorphism 2
Regional/Orogenic Metamorphism 3 Regional/Orogenic Metamorphism 3
Regional/Orogenic Metamorphism 4 Regional/Orogenic Metamorphism 4
http://193.232.116.228/personal/vsz/autoref/fig2ce.GIF
Regional: burial metamorphismRegional: burial metamorphism
Hydrothermal MetamorphismHydrothermal Metamorphism
Basalt
Serpentinite
Water
Fault zone and impactFault zone and impact
www.lpi.usra.edu/meetings/gap2007/gapII-logo.jpg
Progressive Nature of MetamorphismProgressive Nature of Metamorphism
Prograde
Retrograde
Prograde MetamorphismPrograde Metamorphism
• Normally progress through series of mineral Normally progress through series of mineral assemblages, for example:assemblages, for example:
1.1. epidote, chlorite, andalusite, muscovite, quartz, epidote, chlorite, andalusite, muscovite, quartz, k-spar, and albitek-spar, and albite
2.2. sillimanite, plagioclase, cordierite, muscovite, sillimanite, plagioclase, cordierite, muscovite, quartz and k-sparquartz and k-spar
3.3. sillimanite, plagioclase, cordierite, quartz, and sillimanite, plagioclase, cordierite, quartz, and k-spark-spar
Prograde
Retrograde
Prograde MetamorphismPrograde Metamorphism
Retrograde MetamorphismRetrograde Metamorphism
Prograde
Retrogradehttp://www.und.nodak.edu/instruct/mineral/320petrology/opticalmin/chlorite.htm
Common Prograde SequenceCommon Prograde Sequence
Index minerals make zones:Index minerals make zones: Chlorite zone. Pelitic rocks are slates or phyllites and typically Chlorite zone. Pelitic rocks are slates or phyllites and typically
contain chlorite, muscovite, quartz and albitecontain chlorite, muscovite, quartz and albite Biotite zone. Slates give way to phyllites and schists, with biotite, Biotite zone. Slates give way to phyllites and schists, with biotite,
chlorite, muscovite, quartz, and albitechlorite, muscovite, quartz, and albite Garnet zone. Schists with conspicuous red almandine garnet, Garnet zone. Schists with conspicuous red almandine garnet,
usually with biotite, chlorite, muscovite, quartz, and albite or usually with biotite, chlorite, muscovite, quartz, and albite or oligoclaseoligoclase
Staurolite zone. Schists with staurolite, biotite, muscovite, quartz, Staurolite zone. Schists with staurolite, biotite, muscovite, quartz, garnet, and plagioclase. Some chlorite may persistgarnet, and plagioclase. Some chlorite may persist
Kyanite zone. Schists with kyanite, biotite, muscovite, quartz, Kyanite zone. Schists with kyanite, biotite, muscovite, quartz, plagioclase, and usually garnet and stauroliteplagioclase, and usually garnet and staurolite
Sillimanite zone. Schists and gneisses with sillimanite, biotite, muscovite, quartz, plagioclase, garnet, and perhaps staurolite. Some kyanite may also be present (although kyanite and sillimanite are both polymorphs of Al2SiO5)
Sequence of indicator mineralsSequence of indicator minerals
Chlorite
BiotiteGarnet
Staurolite
Kyanite
Sillimanite