In nature, there are several varieties of rocks: sedimentary, metamorphic and igneous. All of them are compounds of certain minerals.
In this article, we will examine in detail what metamorphic rocks are. Let us describe their types, characteristic features and methods of use in industry.
However, first of all, it should be told what rocks are. This term is used to refer to natural chemical compounds that form in the earth's crust.
Metamorphic rocks occur as a result of exposure to high temperatures and strong pressure on fossils of magmatic or sedimentary origin. At the same time, the chemical composition of minerals does not undergo significant changes, but they acquire a new texture and structure.
Many metamorphic fossils are distinguished by shale (the presence of thin stripes). This characteristic indicates the method of mineral formation (under the influence of pressure). Such fossils have the ability to break into thin plates.
If the process of transformation of some minerals into others (metamorphism) occurs under the influence of heat of intrusive masses at a shallow depth, in this case metamorphic rocks will have a horny structure. An example of this is the hornfelses (biotite, pyroxene, amphibolite) formed from clay.
The process of metamorphism (modification) can be exposed to any minerals - of magmatic, sedimentary or metamorphic origin. Any transformations in the rocks are carried out by their recrystallization in the solid state. Moreover, the degree of transformation of the source minerals can be very diverse, from small modifications to significant changes in the composition and appearance of the fossil. The nature of metamorphism is also different. Only a slight compaction can occur, and maybe a complete recrystallization of the mineral.
All metamorphic rocks are inherently a secondary product. Depending on the degree of conversion, several types of transitional minerals are distinguished:
- Contact. They arise as a result of magma intrusion (penetration into the earth's crust) and its interaction with sedimentary rocks. Minerals of this type are formed under the influence of pressure and high temperature. Such fossils include marble, skarn, migmatite. The rocks of contact metamorphism have a predominantly crystalline, massive, sugar-like and slightly layered structure, while the composition of minerals undergoes significant changes.
- Regional (deep). The process of modification takes place at great depths with the interaction of high pressure, temperature and fluids. The mineralogical composition of minerals in this case does not always change. The rocks are distinguished by crystalline, shale, dense structure.
- Dynamo metamorphism. The conversion process occurs in tectonic plates under high pressure. In this variety of minerals strong crushing zones and complex folds are formed. Such fossils include milonites and ka-taclazites.
Usually metamorphic rocks are found in nature in the form of veins, layers and lenses. They most often preserve the bedding of the original mineral, but upon contact with magma intrusions, the minerals may be irregular in shape.
Metamorphic minerals are used all over the world as decorative, building and ornamental material (quartzite, marble, slates, gneiss). They are also used as industrial raw materials (asbestos, talc, etc.). In nature, metamorphic rocks are most often located near deposits of minerals, precious and ornamental stones (ruby, emerald, jadeite, garnet, etc.).