What is retrograde metamorphism in geology?
Retrograde metamorphism (diaphthoresis, retrogressive metamorphism) is the mineralogical adjustment of relatively high-grade metamorphic rocks to temperatures lower than those of their initial metamorphism.
What is prograde and retrograde metamorphism?
In metamorphic rock: Retrograde metamorphism. In general, the changes in mineral assemblage and mineral composition that occur during burial and heating are referred to as prograde metamorphism, whereas those that occur during uplift and cooling of a rock represent retrograde metamorphism.
What are the 3 main types of metamorphism?
The three types of metamorphism are Contact, Regional, and Dynamic metamorphism. Contact Metamorphism occurs when magma comes in contact with an already existing body of rock.
What is meant by Metasomatism?
Metasomatism refers to the process whereby a preexisting igneous, sedimentary, or metamorphic rock undergoes compositional and mineralogical transformations associated with chemical reactions triggered by the reaction of fluids (so-called metasomatic agents), which invade the protolith.
What do you mean by prograde?
Prograde refers to an object that spins in the same direction as its orbit. Retrograde refers to an object that spins in the opposite direction of its orbit. Earth has a prograde rotation, and asteroid Bennu has a retrograde rotation, which means the two bodies rotate in opposite directions.
What causes shock metamorphism?
Shock Metamorphism (Impact Metamorphism) When an extraterrestrial body, such as a meteorite or comet impacts with the Earth or if there is a very large volcanic explosion, ultrahigh pressures can be generated in the impacted rock.
What are the 7 types of metamorphism?
Types
- Regional.
- Contact (thermal)
- Hydrothermal.
- Shock.
- Dynamic.
- Metamorphic facies.
- Metamorphic grades.
- Recrystallization.
What is retrogression in psychology?
Definition of retrogression 1 : regression sense 3 2 : return to a former and less complex level of development or organization
What has led the economy to retrogression?
Incompetent management has led the economy to retrogression. A society which sidelines women is heading towards retrogression. We are focusing on progression and not retrogression. She warned of serious retrogression in relations between the two countries. The Dark Ages are often considered a time of retrogression.
What is retrogression in gold?
Retrogression is likely to have caused redistribution of gold and yielded textures suggesting that the gold is late — both features of many other gold deposits. The retrogressed rim/corona is a common texture in retrogression in response to uplift or exhumation of former deep-sited metamorphic rocks.
What is the effect of retrogression on metamorphic rocks?
Retrogression of rocks during exhumation can result in a complete overprint of the UHP mineral assemblage, thus, erasing the memory (record) of the UHP event in a metamorphic rock.