About Metamorphic Rock.
Metamorphic Occurs When.
When an existing rock (a protolith)is subjected to pressures or temperatures very different from those under which it originally formed. This causes its atoms and molecules to rearrange themselves into new minerals while still in the solid state, without melting taking place. The result of this transmutation is called a metamorphic rock. There are three different ways in which metamorphic rocks are formed.
Dynamic Pressure. Dynamic Metamorphism Rocks.
Metamorphism may be the result of a large-scale movement in the earths crust, especially along fault planes and at continental margins where tectonic plates are colliding
Rock masses are crusted as great pressures come . The resulting mechanical deformation, with little temperature change, is known as Dynamic Metamorphism.
The rocks that are produced by this form of metamorphism range from angular fragments to fine-grained, granulated or powered rocks, such as mylonite.
Contact Metamorphism Rocks. (or thermal metamorphism.)
Contact metamorphism occurs mainly as a result of increases in temperature with little or no contribution from pressure. It is common in rocks near an igneous intrusion. Heat from the intrusion alter rocks in the surrounding area to produce a (aureole) Change of metamorphic rock. Since the rocks nearest to the intrusion are subjected to higher temperatures than those farther away, they exhibit different characteristics. Thus the temperature gradient , form high to low, creates concentric zones of distinctive metamorphic rocks.
Regional Metamorphic Rocks
Regional Metamorphic Rocks formation is associated with the process of mountain-building through the collision of tectonic plates. This process generates increases in temperature and pressure that may extend over an area of thousand of square kilometres, producing widespread metamorphism. The most important regional metamorphic rocks include slate, schists, and gneisses.
Which one of these is produced depends on the temperatures and pressure to which the existing rocks have been subjected, as well as the amount of time they have spent under those conditions.. Slates are produced in areas of relatively low temperature and pressure. Where temperatures and pressures are at their highest, gneisses are produced. Schists are formed in zones of intermediate temperature and pressure.