GLGY 209 Chapter Notes - Chapter 9: Metamorphic Rock, Geothermal Gradient, Protolith
4 May 2019
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Document Summary
Metamorphic rocks form through the transformation of pre-existing rocks under the action of high temperatures, high pressures oriented stress, and chemically reactive fluids. Transformation of the initial rock into new rock happens as the rock remain in solid state, and the changes induced in the protolith can be mineralogical, textural, or, more frequently both mineralogical and textural. The environmental conditions at the earth"s surace and in its interior are continuously changing, and rocks, just like every other physical system, have the tendency to achieve equilibrium with the surrounding environment. Temperature increases gradually from the surface to the center of the earth. Rate at which the temperature increases is known as geothermal gradient. Geothermal gradient is variable due to the heterogeneity in the earth"s composition, radioactive decay process, migrating molten matter, presence/absence of volatile substances etc. Temperature increases results in the bond breakage of crystal structure. Pressure consists of two distinct components.
