Metamorphic Rocks

Introduction

Minerals or rocks are something that the earth is blessed with. There were many types of rocks present in our nature like sedimentary rocks, igneous rocks, and metamorphic rocks. We discussed metamorphic rocks. Metamorphic rocks are created when extreme heat and pressure change and change the original rock into a new type of rock, sedimentary or igneous rocks are transformed into new metamorphic rocks under extreme heat and pressure like magma inside the earth.

The changes that occurred during this process of metamorphism. This is because of the change in the pressure and temperature that changes the configuration and also the appearance of the existing igneous and also in sedimentary rocks and thus form metamorphic rocks. Thus we can say that metamorphic processes include the state change in the minerals.

The temperature inclined between the pre-existing rocks and the magma of liquid form is the main factor for the large changes in appearance and chemical configuration.

What do you mean by metamorphic rocks?

When sedimentary or igneous rocks are countered by the change of heat and pressure, they change their form and transform into metamorphic rocks.

Metamorphism is a type of process which combines rocks and undergoes recrystallization and reorganization of new materials with original rocks. Metamorphisms are divided into two categories: Dynamic Metamorphism (without any relevant chemical change) and Thermal Metamorphism.

Due to thermal metamorphism, it can be divided into the following parts −

Contact Metamorphism

As the name suggests mainly original rocks are coming into contact with extremely large heat which is generally given that by lava or magma present at the core of the earth. Rocks are burnt by the heat of the magma, and that burning causes them to change or morphosis into new. This is commonly in orange color.

Regional Metamorphism

This is going to be more pressure. The cracked layer of rock, as two sides of cracks, are coming together. In the middle there is immense pressure and that pressure can cause the rocks trapped in the middle to become metamorphosed. so at the boundary metamorphic rocks are created. This is different from contact metamorphism as it does not contain so much heat, it is formed by more pressure.

Types of metamorphic rocks

Majorly there are generally two types of metamorphic rocks −

• Foliated Metamorphic Rock − They are arranged in layers or bands. Rocks are subjected to different stress and are classified by composition and grain size. The rock is stripped or streaked. Foliation occurs when pressure compresses the minerals within the rocks to line up flatly. These types of rocks form a sheet-like composition which considers that the pressure is applied in that direction. In other words, we say that foliated metamorphic rocks contain layers or stripes caused by the heating and other effects of minerals in the rock as a result it undergoes metamorphism. For Example Slate, genesis, schist, migmatite, phyllite, etc

• Non-Foliated Metamorphic Rocks − They do not have layers or bands. There is no compression or shear possible. This type forms minerals that are not flat. Also, grains will not line up when pressure is applied. The rock is stripped or streaked. Layers or banding also did not appear. Also, Nonfoliated metamorphic rocks do not consist of minerals that line up during metamorphism and they do not appear layered. For Example Quartzite, hornfels, most importantly marble, etc.

Formation of metamorphic rocks

Due to the earth's movement or due to other reasons rocks are deeply buried or squeezed. As a result heat from magma and pressure from the surface of rocks put these rocks under great pressure and thus these rocks change. They do not melt but the minerals inside them change chemically and they form another type of rock which is known as metamorphic rocks. The changes that change the rock’s type and size and texture. It is processed at a heat which is between 150° and 795° Celsius which produces high energy that can crack and reform the texture of rocks.

Elements present in metamorphic rocks

There are many metamorphic rocks present and also contain various elements. Some of the metamorphic rocks are as follows −

• Quartzite - Essentially hard and consists of quartz. Also small amounts of magnetite, chlorite, amphiboles, calcite, epidote, etc. Also forms a variety of colors due to formalization from sandstone.

• Marble - It contains a typical structure with a variety of colors due to the recrystallization of limestone. It is a type of carbonate consisting of calcite with small amounts of minerals also present such as pyrite, mica, talc, etc. Present as pink marble, black marble, grey marble, or white marble.

• Phyllite - This is an example of foliated metamorphic rock. It consists of mica, chlorite, quartz, iron oxides, felspars, etc.

• Schist - It is formed from the metamorphism of large rocks. It consists of mica, chlorite, talc, kyanite, sericite, etc. It contains a large amount of quartz, garnets, felspars or calcite,

• Genesis - Genesis is a type of foliated metamorphic rock. It is made up of fine mineral grains. It consists of a large number of feldspar minerals, quartz, and mica. It appears branded. It looks the same as granite.

• Hornfels - Hornfels is a fine metamorphic rock. It is formed by the heat on clay rocks which is to be known as contact metamorphism. It is a sort of non-foliated metamorphic rock with no particular composition.

• Amphibolite - Amphibolite is a sort of non-foliated metamorphic rock. It consists of plagioclase, amphibole, and small amounts of quartz. Amphibolite forms in the process of directed pressure and high viscosity within the process of recrystallization.

Conclusion

Metamorphic rocks are the type of rocks formed from other rocks or minerals. They are formed from various processes of sedimentary and igneous rocks. Also, they underwent many changes which resulted from the large pressure or heat. The name suggests their formation where meta means the change which means the new formation. Therefore metamorphic rocks were those rocks whose forms changed through various processes such as large magma or lava intrusions.

FAQs

1. Marble is which type of rock?

Marbles are originally granular metamorphic rock composed of recrystallized limestone with texture grain-like size and varied with different varieties.

2. Which type of rock is formed of quartzite?

By the influence of contact and also dynamic metamorphosis

3. Write some conditions under which low-grade schist is generally formed.

Under the condition of low temperature in regional metamorphosis, low grades of schist are generally formed.

4. For the identification of marbles, which test is preferred?

Due to the presence of calcite which reacts with acid readily and gives the prominent marble to another metamorphosis. Hydrochloric acid is generally used.

5. What do you feel when you touch the talc schist?

Talc schist is low-grade schist that has the property to give a soapy feel when touched with our hands.