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metamorphism
- 1. Metamorphism, Metamorphic Rocks, andHydrothermal Rocks Metamorphic gneiss from Greenland, 3.7 Ba
- 2. © 2008, JohnWiley and Sons, Inc. Metamorphic Rocks – are like Cooking * Ingredients added together are cooked at high temperatures to produce a new and different substance with different textures and form. * Rocks exposed to high temps and pressures react chemically, change
- 3. © 2008, JohnWiley and Sons, Inc. Metamorphic Rocks Metamorphism is the mineralogical, textural, chemical, and structural changes that occur in rocks as a result of exposure to elevated temperatures and/or pressures. Metamorphism occurs in solid state, without any melting processes. So deformation process is preserved in the metamorphic rocks and can be “tracked” in time and through tectonic cycles.
- 4. © 2008, JohnWiley and Sons, Inc. Metamorphic Rocks Factors effecting metamorphism: Temperature Pressure Rock composition Fluids present Stress environment
- 5. • Metamorphic rockscommon in the old, stable cores of continents, known as cratons Metamorphic Rocks *Oldest stable continental core *Seismically fast *Geothermally cold *Buoyant – low density (chemically depleted)
- 6. © 2008, JohnWiley and Sons, Inc. Temperature and pressure conditions for metamorphism Figure 10.2
- 7. © 2008, JohnWiley and Sons, Inc. From shale to gneiss Figure 10.3 Shale Slate Phyllite Gneiss Diagenesis Low-Grade Medium-Grade High-Grade * Sillmanite and Kyanite Al2O3 with different crystal structures
- 8. Pore Fluids andMetamorphic Veins The presence of pore space and aqueous fulids can facilitate metamorphic reactions. Porous fluid flow transports mineral chemicals and speeds up mineral growth and recrystallization.
- 9. Metamorphic Rocks UnderStress Granite consists of quartz, feldspar, biotite which recrystallized from magma under conditions of uniform stress. Grains are randomly oriented. This gneiss, a high-grade metamorphic rock, contains the same minerals as the rock on the left but deformed in solid state under differential stress. Biotite grains are aligned in a layered texture. Foliation is the planar arrangement of mineral grains giving a layered texture
- 10. Metamorphism and Billiards ©2008, John Wiley and Sons, Inc. Wood in early pool tables vibrated and warped. Slate used in 1825 – better table and game. Slaty (low grade met.) cleavage surface, strong, still.
- 11. Rocks with Foliation Rockswithout Foliation Metamorphic Rocks © 2008, John Wiley and Sons, Inc. Metamorphism: New Rocks from Old
- 12. © 2008, JohnWiley and Sons, Inc. Metamophism of Sedimentary Rocks Shale Slate Phyllite Sedimentary Rock Fine grained, low grade metamorphic rock with slaty cleavage. Fine grained, high grade metamorphic rock with foliation.
- 13. Metamophism of SedimentaryRocks Sandstone Quartzite Dominantly quartz minerals Very little foliation due to low diversity of minerals.
- 14. © 2008, JohnWiley and Sons, Inc. Metamorphism of Volcanic Rocks Granite Gneiss Mineral content includes quartz, feldspar, biotite micas Metamorphism of complex mineralogy induces foliation.
- 15. Figure 10.9 Greenschist Amphibolite BlueschistEcologite Increasing grade of metamorphism Increasing pressure (without increasing temperature) Metamorphism of Basalt
- 16. Mechanical deformation Conglomerate pebblesDeformed pebbles due to differential pressure and shear.
- 17. Types of Metamorphism MetamorphicProcesses Metamorphism: New Rocks from Old © 2008, John Wiley and Sons, Inc.
- 18. Types of Metamorphism -Contact metamorphism:Occurs when rocks are heated and chemically changed adjacent to an introduced body of hot magma -Burial: Occurs as a result of burial of sediments in deep sedimentary basins -Regional: Extensive area of crust associated with plate convergence, collision, and subduction.
- 19. © 2008, JohnWiley and Sons, Inc. Nordlingen Cathedral (in Germany) Constructed within an impact crater. Rock construction include local rocks that were metamorphosed by high heat and pressure during impact Shocked quartz from impact