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  2. Migmatite - Wikipedia

    en.wikipedia.org/wiki/Migmatite

    The melanosome is a dark, mafic mineral band formed in migmatite which is melting into a eutaxitic texture; often, this leads to the formation of granite. The melanosomes form bands with leucosomes , and in that context may be described as schlieren (color banding) or migmatitic .

  3. Ultra-high-temperature metamorphism - Wikipedia

    en.wikipedia.org/wiki/Ultra-high-temperature...

    Metamorphism of crustal rocks in which peak temperature exceeds 900 °C, recognized either by robust thermobarometry or by the presence of a diagnostic mineral assemblage in an appropriate bulk composition and oxidation state, such as assemblages with orthopyroxene + sillimanite + quartz, sapphirine + quartz or spinel + quartz, generally at pressure conditions of sillimanite stability in ...

  4. Geology of Nigeria - Wikipedia

    en.wikipedia.org/wiki/Geology_of_Nigeria

    The Migmatite-Gneiss Complex covers half of Nigeria's surface area and encompasses Archean gray gneisses, with tonalite and granodiorite consistencies. Within this complex are occurrences of schist , migmatite , garnet , sillimanite , kyanite and staurolite , which together indicate high-grade metamorphism up to the level of amphibolite on the ...

  5. Granite - Wikipedia

    en.wikipedia.org/wiki/Granite

    Migmatite featuring felsic minerals, at Morton Gneiss Complex Granitization is an old, and largely discounted, hypothesis that granite is formed in place through extreme metasomatism . The idea behind granitization was that fluids would supposedly bring in elements such as potassium, and remove others, such as calcium, to transform a ...

  6. Metamorphic facies - Wikipedia

    en.wikipedia.org/wiki/Metamorphic_facies

    The minerals in a metamorphic rock and their age relations can be studied by optical microscopy or scanning electron microscopy of thin sections of the rock. Apart from the metamorphic facies of a rock, a whole terrane can be described by the abbreviations LT, MT, HT, LP, MP, HP (from low, medium or high; pressure or temperature).

  7. Rock cycle - Wikipedia

    en.wikipedia.org/wiki/Rock_cycle

    This diamond is a mineral from within an igneous or metamorphic rock that formed at high temperature and pressure. The rock cycle is a basic concept in geology that describes transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous. Each rock type is altered when it is forced out of its ...

  8. Mylonite - Wikipedia

    en.wikipedia.org/wiki/Mylonite

    Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogical compositions; it is a classification based on the textural appearance of the rock.

  9. Geology of Wisconsin - Wikipedia

    en.wikipedia.org/wiki/Geology_of_Wisconsin

    The rock record contains an uncertain age gap with younger 1.8 billion years old Proterozoic quartzofeldspathic and migmatite gneiss, with amphibolite and biotite schist. Around 1.9 billion years ago, mafic, intermediate and felsic rocks, in some cases with subordinate metasedimentary rocks, began to form and metamorphosed, reaching greenschist ...