To the Point Classification of Igneous Rocks
To the Point Classification of Igneous Rocks
Igneous Rock Definition
The Rocks which are formed due to the Cooling action, and solidification of molten magma, and lava called Igneous Rocks.Characteristics of Igneous Rocks
- Igneous rocks are considered the world’s oldest rocks and are also known as primary rocks.
- Igneous Rocks are crystalline because they are formed from the cooling of molten magma.
- Igneous Rocks are not made of Rounded Particles (Textures).
- Igneous Rocks are made of texture having various shapes and sizes.
- Igneous Rocks do not contain any fossil content.
- Igneous Rocks are compact; therefore, they are too hard to be eroded easily.therefore,
- Igneous Rocks contain a large variety of minerals in bulk quantity.
- Igneous Rocks are Non-porous, thus, water cannot percolate in them.
- Igneous Rocks are not formed in layers.
- Igneous Rocks show a lot of variations in their Chemical, Mineralogical composition and textural Characteristics.
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Classification of Igneous Rocks
Igneous Rocks are classified in three different ways
01. According
to the Situation
02. According
to Mineral composition
03. According to Formation
01. According to the Situation
According to the situation, igneous rocks are
classified into two types:
Intrusive
Igneous Rock (Plutonic Rock): formed inside the surface.
Extrusive
Igneous Rock (Volcanic Rock): formed outside surface.
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02. According to minerals Composition
According to minerals, igneous rocks are
classified in to
i. Acid Igneous
Rock
ii. Basic Igneous Rock
i. Acid Igneous Rock
Properties:
- Acid igneous rocks about 80% composed of acid-forming radical silicon.
- Acid igneous rock is light in colour.
- It cools fast, therefore; it does not flow or spread away.
- High mountains formed from Acid igneous rock.
- Acid Igneous Rocke belongs to the portion of Earth Called Sill.
ii. Basic Igneous Rock
Properties
- Basic Igneous Rocks contains 40% silicon, they contain 40% magnesium and rest 20% iron.
- Basic igneous rock cools slowly because it contains too low silicon percentage.
- Basalt and Dole site are main examples of basic igneous rock.
- Basic Igneous Rock Belongs to Portions of Earth Called 'Sima'.
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03. According to the Formation
According to the formation, igneous rocks are
classified into six types:
a.
Sill
b.
Dyke
c.
Laccolith
d.
Lapolith
e.
Phacolith
f.
Batholith
a. Sill Igneous Rocks
When an intrusion occurs like a thin sheet
of a horizontal position, parallel to the existing rock called sill
igneous rock.
b. Dyke Igneous Rock
- When vertical layers of intrusive igneous rocks are formed in already existing sedimentary rock are called dyke igneous. rock.
- Dykes are semi-crystalline rocks formed along the beds or layers of sedimentary rocks.
c. Laccolith Igneous Rock
A laccolith is a dome-shaped large blister
of igneous rock that appears on the upper Earth Surface.
d. Phacolith Igneous Rock
Phacolith
is a lense-shaped, wavelike a mass of igneous rock that occupies the crest of anticline and bottom of the syncline, it is fed by the Conduit (volcanic pipe) from the bottom.
e. Batholith Igneous rock
The Batholith is a large body of intrusive igneous rock; it is also called Plutonic rock. it is formed deep inside and mostly covers a larger than 100 sq km area.
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