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Metamorphic rock can be formed locally when rock is heated by the intrusion of hot molten rock called magma from the Earth's interior. The study of metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides information about the temperatures and pressures that occur at great depths within the Earth's crust.
Eclogite – Metamorphic rock formed under high pressure; Gneiss – Common high-grade metamorphic rock; Granulite – Class of high-grade medium to coarse grained metamorphic rocks; Greenschist – Metamorphic rock – A mafic metamorphic rock dominated by green amphiboles; Hornfels – Group of metamorphic rocks
These rocks have undergone extensive metamorphism, and represent some of the oldest surface rocks on Earth. Two papers dating the age of the Nuvvuagittuq Greenstone Belt have been published. One paper gave an age of c. 3,750 million years ( Ma ), [ 2 ] while the other gave an age of c. 4,388 Ma. [ 3 ]
Slate is a fine-grained, foliated, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade, regional metamorphism. It is the finest-grained foliated metamorphic rock. [1]
Metamorphic rocks are created by rocks that have been transformed into another kind of rock, usually by some combination of heat, pressure, and chemical alteration. Sedimentary rocks are created by a variety of processes but usually involving deposition, grain by grain, layer by layer, in water or, in the case of terrestrial sediments, on land ...
Tectonites are rocks with minerals that have been affected by natural forces of the earth, which allowed their orientations to change. This usually includes recrystallization of minerals, and the foliation formation. Tectonites are studied through structural analysis and allows for the determination of two things: [2]
Gneiss, a foliated metamorphic rock. Quartzite, a non-foliated metamorphic rock. Foliation in geology refers to repetitive layering in metamorphic rocks. [1] Each layer can be as thin as a sheet of paper, or over a meter in thickness. [1] The word comes from the Latin folium, meaning "leaf", and refers to the sheet-like planar structure. [1]
[33] [34] Subsequent erosion of the mountains exposes the roots of the orogenic belt as extensive outcrops of metamorphic rock, [35] characteristic of mountain chains. [33] Metamorphic rock formed in these settings tends to shown well-developed foliation. [33] Foliation develops when a rock is being shortened along one axis during metamorphism.