Himalayas dynamothermalmetamorphism beforecollision

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Unformatted text preview: , Major Himalayas, and Appalachian Mts. Himalayas, Dynamothermal Metamorphism, Before collision Sediments are “unconsolidated”. They will fold if pushed. Dynamothermal Metamorphism, After continental collision Felsic continental materials and sediments are buoyant, they have low density They float, cannot be subducted, so they get squashed. 2. Regional Metamorphism 2. Regional Metamorphism (continued) Most Dynamothermal metamorphism occurs along convergent plate boundaries plate Most Example 2: In Subduction Zones Metamorphism in a Subduction Zone Metamorphic Grade and Index Minerals Index Certain minerals, called index Certain minerals, are good indicators of minerals are the metamorphic conditions in which they form they Note Temperature gradient Index Minerals in metamorphic rocks 580oC 220oC 460oC Note Quartz and Feldspar are not index minerals: Why? 690oC Here is an internally heated pressure vessel at the AMNH With these you can study, for example: 1. the temperature and pressure conditions at which polymorphs change from one form to another. (next slide) 2. the reactions of minerals with fluids (for example salty or alkaline water) at high temperatures and pressures. 3. the conditions necessary to change one assemblage of minerals to another http://research.amnh.org/earthplan/research/Equipment/Petrology Thermometers and Pressure Gauges Sillimanite Kyanite Polymorphs of Al2SiO5 Andalusite CANADA New England Dynamothermal Metamorphism 7_21 . MAINE ADA CAN .A. U.S Augusta . Caused by C-C collision M-P Most of Appalachians Montpelier NEW VERMONT HAMPSHI...
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