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Classification and Facies

Classification and Facies. Wikipedia. Today. Updates: Not today Lecture outline: Rock classification Facies. Prograde Metamorphism. Normally progress through series of mineral assemblages, for example: epidote, chlorite, andalusite, muscovite, quartz, k-spar, and albite

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Classification and Facies

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  1. Classification and Facies Wikipedia

  2. Today Updates: Not today Lecture outline: • Rock classification • Facies

  3. 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

  4. Prograde Metamorphism Prograde Retrograde

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

  6. 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)

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

  8. Types of Protolith Six chemically based-groups to start with 1. Ultramafic - very high Mg, Fe, Ni, Cr 2. Mafic - high Fe, Mg, and Ca 3. Shales (pelitic) - high Al, K, Si 4. Carbonates- high Ca, Mg, CO2 5. Quartz - nearly pure SiO2. 6. Quartzo-feldspathic - high Si, Na, K, Al

  9. A Classification of Metamorphic Rocks

  10. A Classification of Metamorphic Rocks

  11. Compositional Classification Parent Metamorphic rock Clay-rich sediment pelite Sand-rich sediment psammite Clay-sand mix semi-pelite Quartz sand quartzite Marl (limy mud) metamarls-silicate/calcareous Limestone marble Basalt metabasite

  12. a b Pelite protolith: Foliated Metamorphic Rocks-- low grade

  13. Pelite protolith: Foliated Metamorphic Rocks--middle grade

  14. Pelite protolith: Foliated Metamorphic Rocks-- high grade

  15. Non-Foliated Rocks

  16. Specific Rock Types

  17. Specific Rock Types Skarn: carbonate + contact metamorphism + Si added (metasomatism). Minerals: grossular, epidote, tremolite, wollastonite, diopside Granulite: high-grade rock from pelitic, mafic, or quartzo-feldspathic protolith, few OH-bearing minerals.

  18. Specific Rock Types http://www.earth.edu.waseda.ac.jp/photogeology/ 200504rocky/BigornMtS/1K_DSC_1687.jpg http://z.about.com/d/geology/1/0/I/z/migmatite1_500.jpg

  19. http://z.about.com/d/geology/1/0/h/L/greenschist.jpg Specific Rock Types Protolith = mafic rock or graywacke (dirty sst): Greenschist: low-grade, contains chlorite, actinolite, epidote (all green), and albite. Amphibolite: mid-grade, dominated by hornblende + plagioclase.

  20. http://www.npolar.no/geonet/picture_atlas/SE02-1-25.jpg Specific Rock Types Serpentinite:ultramafic rock, low-grade metamorphosed. Blueschist:high-P, blue by glaucophane--amphibole (mafic rock) or blue by kyanite (pelite). Eclogite:green + red due to clinopyroxene and garnet (omphacite + pyrope). (basalt) http://www.dges.tohoku.ac.jp/museum/large/eclogite.jpg

  21. Metamorphic Facies Wikipedia

  22. Prograde Sequence and Facies Index minerals make zones, but COMPOSITION DEPENDENT Change in composition, means change in minerals occurring • Chlorite zone. • Biotite zone. • Garnet zone. • Staurolite zone. • Kyanite zone. • Sillimanite zone. => Facies is better to compare different metamorphic rocks • Chlorite • Biotite • Cordierite • Andalusite • Sillimanite

  23. Prefix and mineral texture

  24. High Strain Rocks

  25. High Strain Rocks

  26. Why do we care about metamorphic rocks?

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