Geology -- Metamorphic Rocks -- Ch. 6
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28 terms
Terms | Definitions |
|---|---|
 Metamorphism | When rocks are subjected to enough heat, pressure, and fluid activity to change their mineral composition, texture or both |
| Metamorphic Rocks | Transformation of rocks by processes that occur beneath Earth's surface |
| 3 Agents of Metamorphism | Heat, Pressure, and Fluids |
| Heat | Increases the rate of chemical reactions |
| Pressure | Burying rocks subjects them to increasingly greater pressure |
| Lithostatic Pressure | Pressure exerted on buried rock by overlying and surrounding rocks |
| Differential Pressure | Stress is not equal in all direction |
| Fluid Activity | The presence of fluids increase reaction rates forming new minerals |
| Contact Metamorphism | Body of magma alters surrounding country rock |
| Country Rock | Surrounding Rocks |
| Shock Metamorphism | Rocks subjected to high levels of differential pressure and some heat by impact |
| Regional Metamorphism | Occurs over a large area usually by intense temperatures and pressures within the deeper portions of the crust |
| Index Minerals | Minerals that form in specific temperature and pressure ranges |
| Metamorphic Grade | Characterizes the degree to which rocks have been metamorphosed; Unaltered, Low Grade, Intermediate, High Grade |
| Foliation | Elongate or platy minerals arrange in a parallel fashion during metamorphism |
| Low Grade Metamorphism | Fine Foliation |
| High Grade Metamorphism | Thick Foliation |
| Slate | Low-grade foliated metamorphic rock |
| Phyllite | Similar in composition to, but coarser grained than slate |
| Schist | Coarser grains than Phyllite |
| Gneiss | High-grade metamorphic rock |
| Migmatite | Formed from extremely high temperatures during metamorphism |
| Marble | Composed of calcite or dolomite |
| Quartzite | Forms under intermediate to high-grade metamorphic conditions under contact or regional metamorphism |
| Anthracite | Forms from metamorphism of coals |
| Metamorphic Zones | A belt of rocks showing the same degree of metamorphism |
| Isograds | Separates metamorphic zones by mineral content |
| Metamorphic Facies | A group of metamorphic rocks characterized by its own distinctive mineral assemblage formed under broadly similar temperature and pressure conditions |
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