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In metamorphic geology, a compatibility diagram shows how the mineral assemblage of a metamorphic rock in thermodynamic equilibrium varies with composition at a fixed temperature and pressure. Compatibility diagrams provide an excellent way to analyze how variations in the rock's composition affect the mineral paragenesis that develops in a ...
Geothermobarometry is the methodology for estimating the pressure and temperature history of rocks (metamorphic, igneous or sedimentary).Geothermobarometry is a combination of geobarometry, where the pressure attained (and retained) by a mineral assemblage is estimated, and geothermometry where the temperature attained (and retained) by a mineral assemblage is estimated.
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 ...
Determining the temperature and/or pressure of formation of metamorphic rocks began as a mostly qualitative science. Pelitic index minerals were used to estimate the metamorphic grade of rocks, and the relative conditions of metamorphism across an area.
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.
This assumes the rock has a KFMASH (K 2 O–FeO–MgO–Al 2 O 3 –SiO 2 –H 2 O) composition because that is what the experimental data was created with. If the composition of the rock differs from this, then the figure is less accurate. Norman L. Bowen proposed the concept of petrogenetic grids in 1940. [7]
In practice, garnet is commonly used in the study of metamorphic rocks due to its refractory nature. [22] In past studies, garnet is found to be a mineral that is stable under a wide range of P-T conditions, meanwhile chemically displays responses (e.g. ions exchange ) to the P-T variations throughout its metamorphic history without reaching ...
A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures. [1] The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. pressure (See diagram in Figure 1). [ 1 ]