What tectonic setting does blueschist form in?
subduction zones
The blueschist facies describes a set of pressure-temperature conditions found in subduction zones where high pressures (i.e. 5-6 kbar) can be achieved in combination with low temperatures (i.e. 200-500°C).
Where are blueschist rocks formed?
See, blueschist facies rocks are generally formed in subduction zones where oceanic crust is being stuffed into a trench. That crust includes the basalts and other mafic and ultramafic rocks that will become true blueschist once they’re pressure-cooked.
Where does blueschist facies metamorphism happen?
The blueschist metamorphism probably occurred during thrusting in a zone of anomalously high water pressure in the lower plate along the sole of the thrust fault. This tectonic mode of origin for blueschist differs from the generally accepted hypothesis involving extreme depth of burial.
Where can you find blueschist?
Type-A: most of the Type-A blueschist belts lie in Europe and the Tethyan orogen, including these HP-UHP terranes in the Alps, Greece, and Himalaya (Fig. 3). The pressure of some Type-A UHP metamorphic terranes reaches up to 4.5 GPa, whereas the highest pressure of blueschists are up to 2.5 GPa.
How is blueschist formed?
Blueschists are formed in association with subduction and continental collision and reflect burial to high pressures at relatively low temperatures (see Figure 2.10). It has long been recognized that blueschists older than about 1000 Ma are apparently absent in the geologic record (Ernst, 1972).
What is blueschist metamorphic rock?
Blueschist ( /ˈbluːʃɪst/), also called glaucophane schist, is a metavolcanic rock that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures (200–500 °C (392–932 °F)), approximately corresponding to a depth of 15–30 km (9.3–18.6 mi).
What is the difference between blueschist and greenschist facies?
As nouns the difference between blueschist and greenschist is that blueschist is (geology) a metamorphic rock containing glaucophane while greenschist is a metamorphic rock formed at low temperature and pressure, often with an abundance of green minerals such as chlorite, serpentine, and epidote.
What conditions of temperature and pressure do Blueschist facies indicate?
The presence of the blue sodium-rich amphibole glaucophane defines rocks of the Blueschist Facies, which is diagnostic of metamorphism at high pressures (> 2 GPa) and low temperatures (< 500 °C) that is associated with basaltic rocks having experienced rapid subduction and subsequent rapid exhumation.
Under what tectonic setting does the metamorphic facies blueschist occur the dark blue area in the image )?
Tectonic Settings Blueschist-facies metamorphism is important in subduction zones, where high-pressure, relatively low-temperature mineral assemblages form. Glaucophane and lawsonite, both of which have a bluish color, are common minerals in this setting.
At what temperature and pressure range does blueschist form?
The blueschist metamorphic facies are characterized by the minerals jadeite, glaucophane, epidote, lawsonite, and garnet. They record metamorphism in the cool high-pressure/low-temperature thermal gradients at less than 7°C/km in subduction zones in the last 1 billion years.