EPSC 201 Lecture Notes - Lecture 18: Gneiss, Convergent Boundary, Feldspar
30 May 2016
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Document Summary
Lecture 18: metamorphism occurs when the protolith is subject to, heat, pressure, differential stress (push, pull or shear, bathing in hydrothermal fluids, heat, metamorphism occurs between 250c and 850c and the depth to this temperature varies with tectonic setting, sources of heat: the geothermal gradient, magmatic intrusions, and tectonic compression, heat causes the atoms to vibrate faster, stretching and bending chemical bonds. Mineral grains grow larger at the expense of smaller ones until they interlock: pressure, under the effect of pressure, mineral grains will deform depending on how fast and how the pressure is applied, as pressure increases, the space between mineral grains is eliminated as grains are pressed together. Such transformations involve phase changes and/or neocrystallization: pressure and temperature, when pressure and temperature increase, the original mineral assemblage in a rock becomes unstable, and a new assemblage forms out of minerals that are stable, differential stress, shear.
