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Metamorphic rocks

Metamorphic rocks

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Metamorphic rocks

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  1. Metamorphic rocks

  2. Today Updates: Midterm Lecture outline: • Types of metamorphism • Prograde and retrograde

  3. Types of Metamorphism Different approaches to classification • 1. Based on pressure/stress and temperature: • Dynamic Metamorphism: deviatoric stress • Thermal Metamorphism: increase in T • Dynamo-thermal Metamorphism: P+T change

  4. Types of Metamorphism • 2. Based on setting • Contact Metamorphism • Regional Metamorphism • Hydrothermal Metamorphism • Fault-Zone Metamorphism • Impact or Shock Metamorphism

  5. Contact Metamorphism

  6. Contact Metamorphism 2 The size and shape of an aureole is controlled by: • Pluton: • Size • Shape • Orientation • Temperature • Composition • Country rocks: • Composition • Depth and metamorphic grade prior to intrusion • Permeability

  7. Contact -- rock types

  8. Contact -- rock types 2

  9. Regional Metamorphism

  10. Regional/Orogenic Metamorphism

  11. Regional/Orogenic Metamorphism 2

  12. Regional/Orogenic Metamorphism 3

  13. Regional/Orogenic Metamorphism 4 http://193.232.116.228/personal/vsz/autoref/fig2ce.GIF

  14. Regional: burial metamorphism

  15. Hydrothermal Metamorphism Water Serpentinite Basalt

  16. Fault zone and impact www.lpi.usra.edu/meetings/gap2007/gapII-logo.jpg

  17. Progressive Nature of Metamorphism Prograde Retrograde

  18. Prograde Metamorphism • Normally progress through series of mineral assemblages, for example: • epidote, chlorite, andalusite, muscovite, quartz, k-spar, and albite • sillimanite, plagioclase, cordierite, muscovite, quartz and k-spar • sillimanite, plagioclase, cordierite, quartz, and k-spar

  19. Prograde Metamorphism Prograde Retrograde

  20. Retrograde Metamorphism Prograde Retrograde http://www.und.nodak.edu/instruct/mineral/320petrology/opticalmin/chlorite.htm

  21. Common Prograde Sequence Index minerals make zones: • Chlorite zone. Pelitic rocks are slates or phyllites and typically contain chlorite, muscovite, quartz and albite • Biotite zone. Slates give way to phyllites and schists, with biotite, chlorite, muscovite, quartz, and albite • Garnet zone. Schists with conspicuous red almandine garnet, usually with biotite, chlorite, muscovite, quartz, and albite or oligoclase • Staurolite zone. Schists with staurolite, biotite, muscovite, quartz, garnet, and plagioclase. Some chlorite may persist • Kyanite zone. Schists with kyanite, biotite, muscovite, quartz, plagioclase, 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)

  22. Sequence of indicator minerals Sillimanite Kyanite Staurolite Garnet Biotite Chlorite