METAMORPHISM: NEW ROCKS FROM OLD

1. METAMORPHISM: NEW ROCKS FROM OLD

2. Objectives Explain how metamorphism differs from diagenesis and lithification. Define the grade of metamorphism. Define foliation. Describe and identify the common metamorphic products of shale and basalt. Identify several common metamorphic rocks. Describe contact, burial, and regional metamorphism.

3. What is Metamorphism? Metamorphism The mineralogical, textural, chemical and structural changes that occur in rocks A result of exposure to elevated temperatures and/or pressure

4. What is Metamorphism? Low-grade Rocks metamorphosed under temperature and pressure conditions up to 400°C and 400 MPa High-grade Rocks metamorphosed under temperature and pressure conditions higher than about 400°C and 400 MPa

5. What is Metamorphism? Factors that influence metamorphism Temperature Pressure

6. What is Metamorphism? Factors that influence metamorphism Pore fluids

7. What is Metamorphism? Factors that influence metamorphism Stress Foliation A planar arrangement of textural features in a metamorphic rock, Gives rock a layered or banded appearance

8. What is Metamorphism? Factors that influence metamorphism Foliation Slaty cleavage Foliation in low-grade metamorphic rocks that causes such rock to break into flat, plate like fragments Schistosity Foliation in coarse grained metamorphic rocks

9. What is Metamorphism?

10. Metamorphism and Billiards

11. What is Metamorphism? Factors that influence metamorphism Duration Rate of metamorphism

12. Metamorphic Rocks Rocks with foliation Slate A very fine grained metamorphic rock with slaty cleavage; the metamorphic product of shale Phyllite A fine grained metamorphic rock with pronounced foliation, produced by further metamorphism of slate

13. Metamorphic Rocks

14. Metamorphic Rocks

15. Metamorphic Rocks Rocks without foliation Quartzite The product formed by re-crystallization of sandstone Marble The product formed by re-crystallization of limestone

16. Metamorphic Processes Processes that cause changes in texture and mineral assemblages in metamorphic rock Mechanical deformation Grinding, crushing, bending and fracturing

17. Metamorphic Processes Processes that cause changes in texture and mineral assemblages in metamorphic rock Chemical recrystallization Changes in mineral composition, growth of new minerals, recrystallization of old minerals, and changes in amount of pore fluid Typically caused by heating and squeezing of rock

18. Metamorphic Processes Type of metamorphism Contact metamorphism Rocks are heated and chemically changed adjacent to an intruded body of hot magma Burial metamorphism Occurs after diagenesis, as a result of the burial of sediments in deep sedimentary basins

19. Metamorphic Processes Type of metamorphism Regional metamorphism Metamorphism of an extensive area of the crust Associated with plate convergence, collision, and subduction Other types of metamorphism occasionally occur in geologic settings where high temperature and/or elevated pressure or stress exists

20. Metasomatism Metasomatism: The process where-by the chemical composition of a rock is altered by the addition or removal of material by solution in fluids Frequently water or carbon dioxide

21. Metamorphic Facies The set of metamorphic mineral assemblages Form in rocks of different compositions Form under similar temperature and stress conditions

22. Metamorphic Facies

23. Critical Thinking Compare the concept of metamorphic facies to that of sedimentary facies. In what ways are they similar? In what ways are they different? Museum curators obviously can’t shave off pieces from valuable art. How do you think they manage to identify the rocks and minerals? Briefly explain how pressure and temperature might change over time in rocks being subjected to contact, burial, and subduction-related regional metamorphism.