What are pelitic rocks?
What are pelitic rocks?
A pelite (Greek: pelos, “clay”) or metapelite is a metamorphosed fine-grained sedimentary rock, i.e. mudstone or siltstone. A semipelite is defined in part as having similar chemical composition but being of a crystalloblastic nature.
Which rocks are typical of contact metamorphism?
The original rock with thermal contact metamorphism is mainly mudstone, carbonate rock, clastic rock, and igneous rock that can form different thermal contact metamorphic rock types.
What is a contact metamorphism rock?
Contact metamorphic rocks form when rocks are heated to high temperatures, usually through contact with an igneous intrusion at a relatively low pressure. The effects of contact metamorphism usually only extend for a short distance from the cooling igneous rock that is providing the heat.
What is prograde metamorphism?
Prograde metamorphism involves the change of mineral assemblages (paragenesis) with increasing temperature and (usually) pressure conditions. These are solid state dehydration reactions, and involve the loss of volatiles such as water or carbon dioxide.
Where do you find contact metamorphism?
Contact metamorphism is thus primarily a thermal phenomenon. It may occur in diverse tectonic settings such as in orogenic or anorogenic environments, in plate interiors or along plate margins.
Why are metamorphic rocks formed by contact metamorphism?
Metamorphic rocks form when heat and pressure transform an existing rock into a new rock. Contact metamorphism occurs when hot magma transforms rock that it contacts. Regional metamorphism transforms large areas of existing rocks under the tremendous heat and pressure created by tectonic forces.
Is limestone contact metamorphic?
Regional (pressure-dominated) metamorphism occurs over large areas during periods of mountain building. Regional metamorphism causes a layered or platy structure in rocks, called foliation….
| Summary Chart of Common Metamorphic Rocks | Original Rocks | limestone |
|---|---|---|
| Metamorphic Equivalent | marble | |
| Foliated? | no | |
| Metamorphism | contact |
Which is an example of metamorphic rocks?
Common metamorphic rocks include phyllite, schist, gneiss, quartzite and marble.
What is a type locality for contact metamorphism in pelitic rocks?
A type locality for contact metamorphism in pelitic rocks is the contact aureole surrounding the Ballachulish Granite, western Scotland (cf. Pattison, 1992 ).
What is contact metamorphic rock?
Contact metamorphism is a static thermal metamorphism in the vicinity of hot intrusive igneous bodies, and metamorphic rock is formed within the zone of contact metamorphism—contact aureole (Figure 8-1 ).
What are the characteristics of pelitic sediments?
Distal from an igneous intrusion in the shallow continental crust, pelitic sediments may have already experienced low-grade burial metamorphism, such that slates and phyllites are common as “unmodified” country rocks. These lithologies are characterized by fine-crystalline quartz, albite, epidote, muscovite, and chlorite and/or biotite.
What is the significance of metamorphic pelites?
When metamorphosed, pelites show a great diversity in mineral assemblages and textures that are highly sensitive to changing pressure and temperature conditions within the Earth. As such, they have considerable value for petrologists who employ thermobarometry to interpret the tectonic evolution of geological terranes.
