Earth Sciences 1022A/B Lecture 7: Lecture 7
20 Dec 2018
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Document Summary
Heating and pressing of rock by tectonic forces. Heating of rock surrounding igneous intrusions: the intrusions cook the rock around it. Metamorphic rocks are formed by the transformation of pre-existing rock under the influence of high temperature and pressure. Two basic types of metamorphism: 1. Contact heat + uniform pressure: 2. Regional heat + uneven pressure (differential stress) Occurs when a pre-existing rock is heated under uneven pressure (differential stress) i. e. shale (sedimentary) genesis: main minerals: clay + quartz potassium feldspar, amphibole, quarts (crystals are aligned in bands) Pre-existing rock is subjected to heat and pressure on a regional scale: commonly associated with mountain building events rocks are lowered to great depths and squeezed by compressive forces. Bedding (stratification) a sedimentary characteristic produced by the deposition of sediments in horizontal layers. Grade increasing intensity of metamorphism: results in increased size of mineral grains and the development of distinct types of foliation.
