What rocks form in retrograde metamorphism?
Winkler (1967) has suggested that burial of volcanic rocks intercalated with sediments may result in retrograde metamorphism of the volcanic rocks at the same time as the sedimentary rocks are being progressively metamorphosed….Retrograde metamorphic reactions.
| Reactant(s) | Product(s) |
|---|---|
| Wollastonite | Calcite |
How does retrograde metamorphism occur?
Retrograde metamorphism involves the reconstitution of a rock via revolatisation under decreasing temperatures (and usually pressures), allowing the mineral assemblages formed in prograde metamorphism to revert to those more stable at less extreme conditions.
Where does retrograde metamorphism occur?
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 is a retrograde mineral?
Reaction textures present in the rock might indicate incomplete reaction. Known retrograde minerals, i.e. those stable at lower pressures and temperatures than the rest of the minerals in the rock, could be identified.
What is a eclogite facies in geology?
glaucophane facies, one of the major divisions of the mineral facies classification of metamorphic rocks, the rocks of which, because of their peculiar mineralogy, suggest formation conditions of high pressure and relatively low temperature; such conditions are not typical of the normal geothermal gradient in the Earth …
What texture is eclogite?
Eclogite GR 30c is a massive medium-grained rock, consisting of garnet, omphacite, glaucophane, epidote, phengite, apatite, quartz, and rutile. Garnet poikiloblasts occur as euhedral crystals, rich in inclusions such as titanite, epidote, apatite, and quartz. The foliation is defined by glaucophane and epidote.
How is eclogite created?
Eclogites form when mafic rock (basalt or gabbro) descends deep within the Earth, generally at a subduction zone. At high pressures and temperatures, the original minerals in mafic rock are squished into the more compact (denser) minerals garnet and omphacite, and the mafic rock becomes eclogite.
What is Polymetamorphism geology?
polymetamorphism Repeated episodes of heating and deformation (metamorphism) acting upon a rock system. A Dictionary of Earth Sciences.
