Earth Sciences 1022A/B Lecture Notes - Lecture 4: Metamorphic Rock, Geothermal Gradient, Parent Rock
14 Jan 2016
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Document Summary
Rocks can be deeply buried, intruded by magma, or squeezed; They are subjected to heat, pressure, and chemically active fluids: these agents result in metamorphism. Pressure: increases with depth: confining pressure. Produced when a rock is buried quite deeply. Experiences pressure from all sides: directed pressure. Minerals realign to form a new texture (foliation) It"s not from all directions, its from a line through the rock. Increases mainly with temperature as indicated by index minerals in metamorphic rocks. Index minerals from low grade to high grade: (low grade) chlorite, muscovite, biotite, garnet, staurolite, **illustration: progressive metamorphism of shale** sillimanite (high grade) Caused by magma intrusion into cooler parents rocks. Metamorphic aureoles form with decreasing effect away from the intrusion. Host rock minerals recrystallize to new minerals, but are not reoriented (nonfoliated) Nonfoliated metamorphic rocks: marble: coarse interlocking crystals of calcite, quartzite: coarse interlocking crystals of quartz. Involves rocks found near convergent plate boundaries in the cores of mountain belts.
