Petro Lecture Final Flashcards
Define Metamorphism
a subsolidus process leading to changes in mineralogy and/or texture
What are the effects of increasing temperature in metamorphic reactions
Promotes recrystalization, drives reactions, and overcome kinetic barriers
How are upper and lower limits of metamorphism defined
Upper limits begins when the rock begins to melt. Lower limit begins when the tem or pressure is too low for crystals to form.
Are the upper and lower limits the same for different protoliths
No, the crystal formation varies on composition
Explain how and why the lithostatic and hydrostatic pressure gradients are different
Lithostatic: vertical gradient of pressure caused by a column of ROCK
Hydrostatic: vertical gradient of pressure caused by a column of WATER
Describe the three types of deviatoric stress
Compression
Tension
Shear
Order of Stress for Lineation
Max= intermediate >min
Sausage
Order of stress of Foliation
Max>intermediate=min
cookie
order of Stress of Lineation-foliation
Max>intermediate>min
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How are fluids involved in metamorphism
In fluid inclusions, and for hydrous and carbonate phases
How are fluids involved in metamorphism
Fluid inclusions
Fluids required for hydrous and carbonous phases
What are the sources of fluid in metamorphism
Meteoric, juvenile magmatic, subducted material, trapped sea brine, degassing of the mantle
Where in the US is the highest enhances geothermal potential? Why? How is metamorphism involved?
West (yellowstone)
Dynamic Metamorphism
deviatoric stress in dominant, deformation and recrystallization are the main process
Thermal metamorphism
temperature in a near static stress field
Dynamothermal metamorphism
both temp and deformation
Hydrothermal Metamorphism
hot water rich fluids, usually involves metasomatism
Fault-zone metamorphism
high rates of deformation and strain, minor recrystallization inpact/shock
Prograde metamorphism
increase in metamorphic grade with time
retrograde metamorphism
decreasing grade as rock cools
What governs the size and shape of contact aureole formed around a pluton?
Nature of the pluton and nature of the country rock
Nature of the pluton examples
size, shape, orientation, temp, composition
Nature of country rock examples
composition, depth, metamorphic, grade prior to intrusion, permiability
What two rocks can be formed in fault-zones? Which one is found deep and which one shallow?
Fault breccia forms at shallow
Mylonite forms deep
