What does metamorphic rock mean



    Metamorphic rocks arise from older rocks of any type through metamorphosis, i.e. through conversion under high pressure, high temperature and possibly through chemical exchange in the firm Status. During the transformation, the mineral composition of the rock changes because new minerals and mineral aggregates are formed which are stable under the given new pressure and temperature conditions; in addition, the structure of the rock is also transformed. Foliation is typical of metamorphic rocks.

The metamorphic rock quartzite is created from quartz sandstones through recrystallization and the intimate intergrowth of the individual crystal grains, in which the individual grains of sand can no longer be recognized as such. A (pure) limestone turns into a coarse-grained marble by recrystallization while retaining the chemical substance. The metamorphic rocks formed under different conditions are in turn assigned to metamorphic facies. A partially melted rock (anatexis) is called a migmatite and already represents the transition to an igneous rock.

 

Large-scale metamorphosis of rocks usually takes place at great depths, but local transformations can also occur near the earth's surface, for example in places where high tensions have built up.

  • Dynamic metamorphism is caused by high pressure. For example, it can occur locally at faults, and dynamic metamorphism also occurs when rocks are folded through compression and recrystallization. One example is the transformation of clayey sediments into shale.
  • Thermal metamorphism describes the rock transformation through the action of heat from the surrounding rock, either on a local scale by heating the rock around smaller underground magma chambers up to huge transformation zones, so-called Aureolesthat form around large, deep-seated plutonic intrusions, such as those found in the formation of granite.
  • Large-scale exposure to heat and pressure results in regional metamorphismwhich is divided into different degrees. Slate is evidence of regional metamorphism of a low degree, while gneiss is a product of high-degree metamorphism.

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Category: Rock