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Chlorite schist is typically formed by metamorphism of ultramafic igneous rocks, [19] [20] as is talc schist. [21] Talc schist also forms from metamorphosis of talc-bearing carbonate rocks formed by hydrothermal alteration. [22] Graphite schist is uncommon but can form from metamorphosis of sedimentary beds containing abundant organic carbon. [23]
Triangular diagrams showing the aluminium (A), calcium (C) and iron (F) content of the main phases (dark dots) in metamorphic rocks in various facies. Thin grey lines are stable phase equilibria. Triangular diagrams showing the aluminium (A), iron (F) and magnesium (M) content of the main phases (dark dots and, when the composition can vary ...
Blueschist on Île de Groix, France Photomicrograph of a thin section of blueschist facies metamorphosed basalt, from Sivrihisar, Turkey. Blueschist (/ ˈ b l uː ʃ ɪ s t /), also called glaucophane schist, is a metavolcanic rock [1] that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures (200–500 °C (392–932 °F ...
[88] [89] The Al 2 SiO 5 nesosilicate phase diagram shown is a very simple petrogenetic grid for rocks that only have a composition consisting of aluminum (Al), silicon (Si), and oxygen (O). As the rock undergoes different temperatures and pressure, it could be any of the three given polymorphic minerals. [ 84 ]
By lithologic criteria, the Main Central Thrust is defined as the boundary between quartzite and phyllite, from the Lesser Himalayan Sequence; and the orthogneiss biotite-rich schist, which belongs to the Greater Himalayan Crystalline complex. [2] [3] By metamorphic isograd, the Main Central Thrust follows the kyanite isograd. Under this ...
When nothing is known about the protolith, the textural name is used without a prefix. For example, a schist is a rock with schistose texture whose protolith is uncertain. [23] Special classifications exist for metamorphic rocks with a volcaniclastic protolith or formed along a fault or through hydrothermal circulation.
Chlorite schist, a type of greenschist Greenschist (prasinite) at Cap Corse in Corsica, France Greenschist (epidote) from Itogon, Benguet, Philippines. Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically 300–450 °C (570–840 °F) and 2–10 kilobars (29,000–145,000 psi). [1]
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