Metamorphic rocks
Today Updates: Midterm Lecture outline: Types of metamorphism Prograde and retrograde
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
Types of Metamorphism 2. Based on setting Contact Metamorphism Regional Metamorphism Hydrothermal Metamorphism Fault-Zone Metamorphism Impact or Shock Metamorphism
Contact Metamorphism
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
Contact -- rock types
Contact -- rock types 2
Regional Metamorphism
Regional/Orogenic Metamorphism
Regional/Orogenic Metamorphism 2
Regional/Orogenic Metamorphism 3
Regional/Orogenic Metamorphism 4 http://193.232.116.228/personal/vsz/autoref/fig2ce.GIF
Regional: burial metamorphism
Hydrothermal Metamorphism Water Serpentinite Basalt
Fault zone and impact www.lpi.usra.edu/meetings/gap2007/gapII-logo.jpg
Progressive Nature of Metamorphism Prograde Retrograde
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
Prograde Metamorphism Retrograde
Retrograde Metamorphism Prograde Retrograde http://www.und.nodak.edu/instruct/mineral/320petrology/opticalmin/chlorite.htm
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)
Sequence of indicator minerals Sillimanite Kyanite Staurolite Garnet Biotite Chlorite