Rocks that have undergone significant heat and pressure are known as metamorphic rocks. Due to these circumstances, the minerals in rocks rearrange and recrystallize, creating a new rock with differing characteristics from the original rock. Any type of rock, including igneous and sedimentary rocks, can undergo metamorphism. They can also develop as a result of tectonic plate collisions, which subject the rock to extreme pressures and temperatures. Regional Metamorphism and Dynamothermal Metamorphism are the two basic forms of Metamorphism.
What is Metamorphic Rock?
The process of metamorphism, which transforms old rocks into new kinds of rocks, produces metamorphic rocks. The protolith, which is the prior rock, is frequently subjected to pressures of 100 megapascals (1,000 bar) or more as well as temperatures between 150 and 200 °C (300 and 400 °F), resulting in significant physical or chemical changes. The rock mainly maintains its solid state during this phase, although it gradually recrystallizes to a new grade or mineral composition. Any type of rock could be preexisting, including igneous, sedimentary, and metamorphic rocks.
Slate gneiss, schist, marble, and quartzite are a few metamorphic rocks. In the construction of buildings, slate and quartzite tiles are used. Both the construction of buildings and the creation of sculpture use marble. Schist bedrock, on the other hand, can present a problem for civil engineering because of its articulated planes of weakness.
Process of Metamorphism
The rocks do not melt throughout the metamorphism process; instead, they become denser, more compact rocks. There are several ways to create new minerals, including rearranging mineral components, reacting with fluids that enter rocks, and rearranging mineral components. Pressure or temperature can cause changes in rocks that have previously undergone a metamorphosis. Metamorphosing rocks frequently become crushed, smeared, and crumpled. These extreme circumstances do not cause metamorphic rocks to melt or change into igneous rocks.
Formation of Metamorphic Rocks
1. Using High Pressure and Temperature
- High temperature and pressure cause igneous and sedimentary rocks to change in shape and properties.
- The rocks’ composition and texture both change.
2. Fundamental Restructuring
- The rock is broken up into its parts by mechanical and chemical action.
- Various elements combine to form new hard rocks.
Types of Metamorphism Rocks
There are two main types of metamorphic rocks due to variations in pressure, temperature, and direct stress.
- Foliated Metamorphic Rocks
- Nonfoliate Metamorphic Rocks
What are Foliated Metamorphic Rocks?
Slate, phyllite, schist, and gneiss are the four typical forms of foliated metamorphic rocks, listed in order of metamorphic grade or severity of metamorphism. Each of these has a different foliation type.
Slate
- Shale undergoes low-grade metamorphism, which produces slate. Microscopic clay and mica crystals have developed perpendicular to the direction of the highest tension in the slate. Slate tends to cleave into flat sheets or plates; this is known as slate cleavage.
Slate
Phyllite
- Slate and phyllite are comparable, although phyllite has usually been heated to a higher temperature. The micas have expanded as a result. They still are not visible as individual crystals, but the bigger size contributes to a satiny shine on the surface. In contrast to slate, phyllite has a somewhat wavy cleavage.
Phyllite
Schist
- Mica crystals in schist, which develop at greater temperatures and pressures, are large enough to be seen without a magnifying glass. When the sample is turned in the light, individual crystal faces may flash, giving the rock the appearance of sparkling. other minerals, like garnet.
Schist
Gneiss
- The crystals in gneiss are large enough to be seen without the use of glasses and develop under the highest pressures and temperatures. Minerals that have split into bands of various colours are found in gneiss. Foliation in gneiss is identified by the colour bands. Occasionally the bands are quite obvious and continuous, while sometimes they are more like lenses. The light-coloured bands are feldspar and quartz, whereas the dark bands are mostly amphibole. Due to its formation at temperatures greater than those at which micas are stable, gneiss often contains little to no mica.
Gneiss
What are Non-Foliated Metamorphic Rocks?
Metamorphic rocks do not become foliated when they form under low pressure or under the effects of confining pressure that is equal in all directions. Most often, this occurs because they are not sufficiently buried, and a body of magma that has moved into the crust’s uppermost region provides the heat necessary for the metamorphism. Contact metamorphism is the name given to metamorphism that results from being close to magma. Marble, quartzite, and hornfels are a few examples of non-foliated metamorphic rocks.
Marble:
- Metamorphosed limestone is a marble. Any sedimentary textures and fossils that may have been present are obliterated when the calcite crystals recrystallize (grow into larger blocky calcite crystals) during the formation process. The marble will be white if the original limestone is only calcite. However, if it contains impurities like clay, silica, or magnesium, the marble may look to have been “marbled.”
Marble
Quartzite
- Sandstone that has undergone metamorphosis is called quartzite. It is primarily composed of quartz, and frequently, extra silica is used to weld the natural quartz grains of the sandstone together. Quartzite can also have impurities since sandstone often has feldspar, clay minerals, or lithic particles.
Quartzite
Hornfels
- Another non-foliated metamorphic rock that typically develops during the contact metamorphism of fine-grained rocks like mudstone or volcanic rocks is hornfels. Depending on the specific circumstances and the parent rock, hornfels can contain a variety of elongated or platy minerals (such as micas, pyroxene, amphibole, and others), but because the pressure wasn’t noticeably higher in any one direction, the crystal orientation of these minerals is random.
Hornfels
Characteristics of Metamorphic Rocks
- These rocks were formerly igneous or sedimentary rocks, but they underwent high pressure and heat in the earth’s crust, undergoing metamorphosis.
- They have foliated textures and are crystallized.
- Some rocks undergo metamorphosis and afterwards become harder than they were before, such as marble from limestone, diamonds from carbon, and quartzite from sandstone.
- Since the original sedimentary rocks’ fossils were lost during metamorphosis, the metamorphic rocks don’t have any.
- These rocks can be found all over the place.
- Coarse-grained metamorphic rocks make up irregularly foliated rocks. such as gneisses
- The metamorphic rocks with fine grains have excellent foliation. as in schist from the Shale.
- Bands of granular quartz and feldspar make up the majority of gneissic metamorphic rocks.
Uses of Metamorphic Rocks
- Slates are used in building, particularly as roof shingles.
- Some quartzite is used as road aggregate, dimension stone, and slabs for walls, staircases, floors, and flooring.
- Marble is employed in the building and the creation of sculptures.
Metamorphic Rocks in India
- The Himalayas, Assam, West Bengal, Bihar, Orissa, Madhya Pradesh, and Rajasthan are among the regions where gneisses and schists are frequently found.
- The hard rock known as quartzite can be found in Delhi’s environs as well as Rajasthan, Bihar, Madhya Pradesh, Tamil Nadu, and other states.
- Near Alwar, Ajmer, Jaipur, and Jodhpur in Rajasthan, as well as in some areas of the Narmada Valley in Madhya Pradesh, marble is found.
- Rewari (Haryana), Kangra (Himachal Pradesh), and some areas of Bihar are covered in slate, which is used for roofing and for writing in schools.
- Both Orissa and Andhra Pradesh contain graphite.
Conclusion
It can be concluded that metamorphism happens when igneous stone, which is how strong stone is formed, undergoes synthesis or surface changes without the mineral jewels liquefying. According to their protolith, compound and mineral makeup, and surface, metamorphic rocks are arranged in descending order. They could be framed simply by being thickly covered underground, where they are reliant on extreme heat and the tremendous pressure of the stone strata above.
FAQs Related to Rock:
1Q. Why is it called metamorphic rock?
Ans: The word “metamorphism” means “changing of the form” in Greek, and rocks that have undergone recrystallization as a result of environmental changes are known as metamorphic rocks.
2Q. What are the 3 main types of metamorphic rocks?
Ans: There are three different types of metamorphism: contact, regional, and dynamic. Contact metamorphism happens when magma comes into contact with a rock that has previously formed.
3Q. What are metamorphic rocks called?
Ans: Through the process of metamorphism, previous rocks are transformed into new forms as a result of rises in temperature, pressure, and chemically active fluids.
4Q. What are the 2 most useful metamorphic rocks?
Ans: Quartzite and marble are the two most prevalent types of non-foliated rocks. Sandstone’s protolith underwent metamorphism to become quartzite, a rock. In quartzites, recrystallization enlarges and interlocks the quartz grains from the original sandstone.
5Q. Where is a metamorphic rock formed?
Ans: When rocks are exposed to extreme temperatures, high pressures, hot mineral-rich fluids, or more frequently, a combination of these conditions, metamorphic rocks are formed. These kinds of situations can be found on the surface of the Earth or when the tectonic plates collide.