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Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith ) is subjected to temperatures greater than 150 to 200 °C (300 to 400 °F) and, often, elevated pressure of 100 megapascals (1,000 bar ) or more, causing profound physical or chemical changes.
Hornfels – Group of metamorphic rocks Calcflinta – A type of hornfels found in the Scottish Highlands; Litchfieldite – Nepheline syenite gneiss; Marble – Type of metamorphic rock – a metamorphosed limestone; Migmatite – Mixture of metamorphic rock and igneous rock; Mylonite – Metamorphic rock – A metamorphic rock formed by shearing
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The metamorphic facies is not usually considered when classifying metamorphic rock based on protolith, mineral mode, or texture. However, a few metamorphic facies produce rock of such distinctive character that the facies name is used for the rock when more precise classification is not possible.
Igneous rocks can be seen at mid-ocean ridges, areas of island arc volcanism or in intra-plate hotspots. Metamorphic rocks once existed as igneous or sedimentary rocks, but have been subjected to varying degrees of pressure and heat within the Earth's crust. The processes involved will change the composition and fabric of the rock and their ...
The platiness gives the rock schistosity (a tendency to split into layers). Other common minerals include quartz, orthoclase, talc, carbonate minerals and amphibole . [1] Greenschist is a general field petrologic term for metamorphic or altered mafic volcanic rock. In Europe, the term prasinite is sometimes used.
The dominant green epidote in unakite rocks is the metasomatic alteration product of plagioclase feldspar, while the orthoclase and quartz crystals remain unaffected. Distribution [ edit ]
In the igneous environment, metasomatism produces skarns, greisen, and may affect hornfels in the contact metamorphic aureole adjacent to an intrusive rock mass. In the metamorphic environment, metasomatism is driven by mass transfer from a volume of metamorphic rock at higher stress and temperature into a zone with lower stress and temperature ...