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Greenschist facies results from low temperature, moderate pressure metamorphism. Metamorphic conditions which create typical greenschist facies assemblages are called the Barrovian Facies Sequence, and the lower-pressure Abukuma Facies Series. Temperatures of approximately 400 to 500 °C (750 to 930 °F) and depths of about 8 to 50 kilometres ...
The granulite facies is the highest grade of metamorphism at medium pressure. The depth at which it occurs is not constant. A characteristic mineral for this facies and the pyroxene-hornblende facies is orthopyroxene. The granulite facies is characterized by the following mineral assemblages: In metabasites:
Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of 150 °C (300 °F), and often also at elevated pressure or in the presence of chemically active fluids, but the rock remains mostly solid during the transformation. [1]
In his pioneering work on metamorphic facies in the Scottish Highlands, G.M. Barrow identified the chlorite zone as the zone of mildest metamorphism. [12] In modern petrology, chlorite is the diagnostic mineral of the greenschist facies. [10] This facies is characterized by temperatures near 450 °C (840 °F) and pressures near 5 kbar. [13]
Most likely, fluids have been produced under prograde greenschist- to amphibolite-facies metamorphism (220–450 °C and 1–5 Kbar). [3] The generally low salinity of the hydrothermal fluids can be attributed to devolatilization of minerals associated with metamorphic phase reactions, involving dehydration and decarbonisation. [26]
The metamorphic grade is greenschist facies to epidote amphibolite facies. The PMU overthrusts the fold and thrust belt to the South. Paleozoic fold and thrust belt. This unit is very well developed in the Montagne Noire. It shows kilometer-scale isoclinal recumbent folding with thrusting to the South. It comprises a low-grade to non ...
This resulted in widespread deformation with the generation of thrust faults and folding, and caused high pressure-low temperature regional metamorphism. [10] In the Miocene, the Farallon-Pacific spreading center reached the Franciscan trench and the relative motion between Pacific-North America caused the initiation of the San Andreas Fault.
Petrogenetic grid for metapelites (click to zoom). [1] [2] Each line represents a metamorphic reaction.Metamorphic facies included are: BS = Blueschist facies, EC = Eclogite facies, PP = Prehnite-Pumpellyite facies, GS = Greenschist facies, EA = Epidote-Amphibolite facies, AM = Amphibolite facies, GRA = Granulite facies, UHT = Ultra-High Temperature facies, HAE = Hornfels-Albite-Epidote facies ...