EARTHSC 1121 Lecture 11: Metamorphic Rocks and Mountain Building
11 Apr 2017
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Mountain building exhumes deep crust and subjects rock to stress, resulting in economic resources. Metamorphic: changed from an original parent : meta = change, morph = form or shape. Protoliths undergo pronounced changes in : texture, mineralogy. Due to change in physical or chemical conditions: burial, tectonic stresses, heating by magma, fluid alteration. Mountains frequently occur in elongate, linear belts. Mountains are constructed by tectonic plate interactions in a process called orogenesis. Mountain building is driven by plate tectonics: convergent plate boundaries, continental collisions, rifting. Orogenesic phases may last several hundred ma. Ancient mountains are deeply dissected by erosion. Convergent tectonic boundaries create mountains: subduction-related volcanic arcs grow on overriding plate, accretionary prisms (off-scraped sediment) grow upward. Accretion of arc island: island fragments of continental lithosphere wont subduct, added to the overriding plate, exotic terrains geologic history differs from surroundings. Continental collisions: closure of oceans through subduction. Brings two blocks of continental crust together: buoyant continental crust will not subduct.
