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[33] [34] Subsequent erosion of the mountains exposes the roots of the orogenic belt as extensive outcrops of metamorphic rock, [35] characteristic of mountain chains. [33] Metamorphic rock formed in these settings tends to shown well-developed foliation. [33] Foliation develops when a rock is being shortened along one axis during metamorphism.
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith ) is subjected to temperatures greater than 150 to 200 °C (300 to 400 °F) and, often, elevated pressure of 100 megapascals (1,000 bar ) or more, causing profound physical or chemical changes.
Carbonate rocks are classified with the Dunham or Folk classification schemes according to the constituents of the carbonate rock. [13] Metamorphic rock naming can be based on protolith, mineral composition, texture, or metamorphic facies. Naming based on texture and a pelite (e.g., shale, mudrock) protolith can be used to define slate and ...
In metamorphic geology, a compatibility diagram shows how the mineral assemblage of a metamorphic rock in thermodynamic equilibrium varies with composition at a fixed temperature and pressure. Compatibility diagrams provide an excellent way to analyze how variations in the rock's composition affect the mineral paragenesis that develops in a ...
The following is a list of rock types recognized by geologists.There is no agreed number of specific types of rock. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe a rock type.
Rock outcrop along a mountain creek near Orosí, Costa Rica. Rocks are classified according to characteristics such as mineral and chemical composition, permeability, texture of the constituent particles, and particle size. These physical properties are the result of the processes that formed the rocks. [5]
Lithostratigraphic units are recognized and defined on the basis of observable physical rock characteristics. The lithology of a unit includes characteristics such as chemical and mineralogical composition, texture, color, primary depositional structures, fossils regarded as rock-forming particles, or other organic materials such as coal or ...
A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures. [1] The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. pressure (See diagram in Figure 1). [ 1 ]