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| A process or set of processes that affect rocks in such a way as to produce textural changes, mineralogical changes, or both under conditions in the Earth between those of diagenesis and weathering (at the lower limit) and melting (at the upper limit). |
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| Metamorphism dominated by chemical changes induced primarily by chemically active fluids. |
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| Metamorphosed pelite (fine grained, aluminous rock, i.e. mudrocks) |
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| Geothermal gradient ("geotherm") |
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| The rate of increasing temperature with respect to increasing depth in the Earth's interior. |
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| Blueschist metamorphism (high P, low T) |
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| Shock (impact) metamorphism |
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| Calc-silicate mineral suite |
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"Tremble for dire peril walks! Monstrous acrimony spurs mercy's law."
Tremolite Forsterite Diopside Periclase Wollastonite Monticellite Akermanite Spurrite Merwinite Lawsonite |
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| The parallel arrangement of minerals. |
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| The parallelism of alignment of linear elements. |
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| A parallel arrangement of platy minerals. |
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| Gneiss, gneissic layering/banding (gneissosity) |
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| The alteration of lighter and dark layers. |
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| Segregation layering/banding |
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| A line on a map representing the first appearance or disappearance of any particular mineral. |
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| A set of rocks representing the full range of possible rock chemistries, with each rock characterized by an equilibrium assemblage of minerals that reflects a specific, but limited, range of metamorphic conditions. |
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| "In any rock of a metamorphic formation which has arrived at chemical equilibrium through metamorphism at constant pressure and Temperature conditions, the mineral composition is controlled only by the chemical composition [bulk chemistry]. We are led to a general conception which the writer proposes to call metamorphic facies." (Eskola, 1915) |
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| A group of metamorphic facies characteristic of an individual area, represented in a pressure-temperature diagram by a curve or group of curves illustrating the range of the different types of metamorphism and metamorphic facies. |
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