EARTH121 Lecture Notes - Lecture 6: Gneiss, Igneous Rock, Metamorphism

• School: University of Waterloo
• Department: Earth Sciences
• Course: EARTH121
• Professor: John Johnston

Document Summary

Basin during silurian time period contained water, that over time evaporated and left behind precipitates that is now the sediment composing the basin. Metamorphic rock: can form from sedimentary or igneous rock, found in large regions of ancient high-grade rocks called shields that are exposed in continental interiors. Shield rocks form the basement under sedimentary cover. Continental platforms: areas where sediment and sedimentary rocks form: metamorphic rocks return to the surface through exhumation. Meta change, morphe form: protoliths- pre-existing rocks, metamorphism is the alteration of protoliths. Protoliths undergo slow solid-state changes in terms of: texture, mineralogy. Causes: temp, pressure, tectonic stresses, amount of reactive water. Mineralogy: minerals within the rock change in composition due to heat and the rock undergoes a transformation (shale gneiss) Texture: intergrown and interlocking grains, recrystallization, foliation. Development of preferred orientation: compression and shear cause minerals to change shape. Minerals can rotate or grow in preferred directions relative to stretching.