Earth Sciences 1022A/B Lecture Notes - Lecture 19: Differential Stress, Gneiss, Schist
18 Apr 2019
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Document Summary
Metamorphic rocks are formed by the transformation of pre-existing rocks under high temp and pressures. Pre-existing rock is heated by igneous intrusion > forms a metamorphic halo/ aureole in the adjacent rock. Pre-existing rocks are exposed to heat and pressure on a regional scale (mountain building) Sheet like minerals- end up lining up perpendicular to the areas of stress. Bedding= sedimentary characteristic >produced by the deposition of sediment in horizontal layers (the direction alternates light and dark layers) Foliation= only in metamorphic rocks >occurs when plating minerals lining up in response to pressure/stress (often breaks in the direction of foliation > following the alignment of the crystals) Rocks containing elongated minerals (caused by regional metamorphism) are typically foliated. Results in increased size and grains and types of foliation. Slate = transform from shale to create small, plate like mica crystals (low h & p)
