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Contact metamorphism occurs typically around intrusive igneous rocks as a result of the temperature increase caused by the intrusion of magma into cooler country rock. The area surrounding the intrusion where the contact metamorphism effects are present is called the metamorphic aureole, [44] the contact aureole, or simply the aureole. [45]
A geological contact is a boundary ... Gradational contacts occur where the change in ... The surrounding rock may be "baked" through contact metamorphism, ...
Within the upper crust, which is the only part of the Earth's crust geologists can directly sample, metamorphic rock forms only from processes that can occur at shallow depth. These are contact (thermal) metamorphism, dynamic (cataclastic) metamorphism, hydrothermal metamorphism, and impact metamorphism.
Buchan metamorphism occurs often in extensional settings, for example at rift basins. In contact metamorphism (metamorphism caused by high temperatures at low pressure in the vicinity of an igneous intrusion) a local contact aureole of zones is formed around a heat source.
This contact metamorphism results in a rock that is altered and re-crystallized by the extreme heat of the magma and/or by the addition of fluids from the magma that add chemicals to the surrounding rock (metasomatism). Any pre-existing type of rock can be modified by the processes of metamorphism. [4] [5]
Based on inspection of extreme metamorphism and post-subduction magmatism at convergent plate margins, paired metamorphic belts are further extended to two contrasting metamorphic facies series: [7] one is blueschist to eclogite facies series that was produced by subducting metamorphism at low thermal gradients of <10 °C/km, and the other is ...
At stage 1 retrograde metamorphism, near-isothermal decompression after the peak, which indicates uplift and exhumation of the compressed rock in the orogenic belt or forearc. [16] At stage 2 retrograde metamorphism, further decompression and cooling occur at a slow rate, implying further erosion after the tectonic event. [16]
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...