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Migmatite is a composite rock found in medium and high-grade metamorphic environments, commonly within Precambrian cratonic blocks. It consists of two or more constituents often layered repetitively: one layer is an older metamorphic rock that was reconstituted subsequently by partial melting ("paleosome"), while the alternate layer has a ...
Late-stage charnockite dykes cutting anorthosite, Rogaland, Norway Job Charnock's Mausoleum at St John's Church compound, Kolkata. Charnockite (/ ˈ tʃ ɑːr n ə k aɪ t /) is any orthopyroxene-bearing quartz-feldspar rock formed at high temperature and pressure, commonly found in granulite facies’ metamorphic regions, sensu stricto as an endmember of the charnockite series.
The mafic minerals in the TTG rock body, possibly biotite, were weathered, which introduced a brownish coating on the TTG rock surface. Tonalite–trondhjemite–granodiorite ( TTG ) rocks are intrusive rocks with typical granitic composition ( quartz and feldspar ) but containing only a small portion of potassium feldspar .
Migmatite is a gneiss consisting of two or more distinct rock types, one of which has the appearance of an ordinary gneiss (the mesosome), and another of which has the appearance of an intrusive rock such pegmatite, aplite, or granite (the leucosome). The rock may also contain a melanosome of mafic rock complementary to the leucosome. [11]
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 ...
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 ...
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 ...
Aruan Group rocks overly the Watian Group in the West Nile area, with biotite gneiss, hornblende gneiss, migmatite and granitic gneiss and quartzites. Karamoja Gneiss Group rocks share a very similar lithology to the Aruan Group, along with the eastern West Nile Mirian Group , although this group has experienced intense isoclinal folding.