Why is blueschist so rare?
Blueschist is rare, since the conditions that produce it are rather odd. It’s also rarely very old, as it’s easily changed by further metamorphic events.
Is blueschist high grade?
Very Low- to Low-Grade Metamorphism of Mafic Rocks at Medium-High Pressure—Blueschist. At very low to low-temperature (250–500 °C) and medium-high pressure (> 8 kbar), mafic rocks are generally metamorphosed to form blueschist, which contains the blue Na-rich amphibole—glaucophane.
What is blueschist in geology?
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?
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 metamorphic grade is blueschist?
|Metamorphic Type||Blueschist (subtype of Regional)|
|Metamorphic Grade||High P – Low T|
Is blueschist a metamorphic rock?
Blueschist is a regional metamorphic rock formed under high-pressure (HP) low-temperature (LT) conditions.
What type of rock is blueschist?
What is the protolith of Migmatite?
Other migmatite hypotheses Such granites derived from sedimentary rock protoliths would be termed S-type granite, are typically potassic, sometimes containing leucite, and would be termed adamellite, granite and syenite.
Is blueschist a mineral?
Abstract. 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.
Where is greenschist found?
These ancient rocks are noted as host rocks for a variety of ore deposits in Australia, Namibia and Canada. Greenschist-like rocks can also be formed under blueschist facies conditions if the original rock (protolith) contains enough magnesium.
Is blueschist foliated or Nonfoliated?
|Texture||Non-foliated to moderatly-foliated; Medium-grained|
What environment does blueschist form in?
Blueschist, which contains the blue mineral glaucophane, forms in subduction zones under high pressures and low temperatures, and its rare occurrence in Precambrian rocks may indicate that temperatures in early subduction zones were too high for its formation.