GEOL 001 Lecture Notes - Lecture 9: Differential Stress, Geothermal Gradient, Shear Stress
20 Dec 2020
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Document Summary
Transition of one rock into another by temperatures and/or pressure unlike those in which it formed. Igneous rocks, sedimentary rocks, & other metamorphic rocks. Changes in heat, pressure, and the chemical environment of rocks can alter mineral compositions and crystalline textures. Metamorphic changes occur in the solid state, so there is no melting. Recrystallization results in new, stable minerals (making new bonds and moving around) Two sources of heat: contact metamorphism heat from magma, an increase in temperature with depth geothermal gradient. Confining pressure- applies forces equally in all directions. Differential stress unequal in different directions. Sources of fluids: pore spaces of sedimentary rocks (course grains in sandstone, fractures in igneous rocks, hydrated minerals such as clays and micas. Most metamorphic rocks have the same overall chemical composition as the original parent rock (reorganization of matter until stable) Texture size, shape, and arrangement of mineral grains. Foliation any planar arrangement of mineral grains or structural features within a rock.
