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Learn the differences between metamorphism, diagenesis, and lithification. Explore metamorphic grade, foliation, common products of shale and basalt, and identification of metamorphic rocks. Understand contact, burial, and regional metamorphism, factors influencing metamorphism, and metamorphic facies. Delve into types of metamorphism like contact, burial, and regional, metasomatism, and metamorphic processes. Discover rocks such as slate, phyllite, quartzite, and marble, and how pressure and temperature change in different metamorphic settings.
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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.
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
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
What is Metamorphism? Factors that influence metamorphism Temperature Pressure
What is Metamorphism? Factors that influence metamorphism Pore fluids
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
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
What is Metamorphism? Factors that influence metamorphism Duration Rate of metamorphism
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
Metamorphic Rocks Rocks without foliation Quartzite The product formed by re-crystallization of sandstone Marble The product formed by re-crystallization of limestone
Metamorphic Processes Processes that cause changes in texture and mineral assemblages in metamorphic rock Mechanical deformation Grinding, crushing, bending and fracturing
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
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
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
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
Metamorphic Facies The set of metamorphic mineral assemblages Form in rocks of different compositions Form under similar temperature and stress conditions
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.