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Metamorphism is further divided into prograde and retrograde metamorphism. Prograde metamorphism involves the change of mineral assemblages (paragenesis) with increasing temperature and (usually) pressure conditions. These are solid state dehydration reactions, and involve the loss of volatiles such as water or carbon dioxide.
During retrograde metamorphism, near-isobaric cooling after the peak took place, indicating that the rock stays at the same position while the magma cools. [ 16 ] Intrusion of magma results in a great increment in temperature and a slight increase in pressure experienced by the underlying rocks, which gives prograde metamorphism.
Serpentinization is a form of low-temperature (0 to ~600 °C) [5] metamorphism of ferromagnesian minerals in mafic and ultramafic rocks, such as dunite, harzburgite, or lherzolite. These are rocks low in silica and composed mostly of olivine ( (Mg 2+ , Fe 2+ ) 2 SiO 4 ), pyroxene ( XY(Si,Al) 2 O 6 ), and chromite (approximately FeCr 2 O 4 ).
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.
Mineral alteration refers to the various natural processes that alter a mineral's chemical composition or crystallography. [1]Mineral alteration is essentially governed by the laws of thermodynamics related to energy conservation, relevant to environmental conditions, often in presence of catalysts, the most common and influential being water (H 2 O).
In inorganic chemistry, mineral hydration is a reaction which adds water to the crystal structure of a mineral, usually creating a new mineral, commonly called a hydrate.. In geological terms, the process of mineral hydration is known as retrograde alteration and is a process occurring in retrograde metamorphism.
They may often show some form of retrograde metamorphism from a peak metamorphic assemblage and are commonly metasomatised. Shear zones can be only inches wide, or up to several kilometres wide. Often, due to their structural control and presence at the edges of tectonic blocks, shear zones are mappable units and form important discontinuities ...
Often, retrograde metamorphism will not form a foliation because the unroofing of a metamorphic belt is not accompanied by significant compressive stress. Thermal metamorphism in the aureole of a granite is also unlikely to result in the growth of mica in a foliation, although the growth of new minerals may overprint existing foliation(s).