Formation of Anorthosite and Banded iron formation

Anorthosite

Banded iron formation

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1 Formation

1.1 Formation

Anorthosite is a phaneritic, intrusive igneous rock which is characterized by a predominance of plagioclase feldspar which is almost 90–100%, and a minimal mafic component.

The banded iron layers are formed in sea water when oxygen is released by photosynthetic cyano-bacteria. The oxygen then combines with dissolved iron in ocean to form insoluble iron oxides, which precipitated out, forming a thin layer of banded iron formation on ocean floor.

1.2 Composition

1.2.1 Mineral Content

Amphibole, Clinopyroxene, Ilmenite, Magnetite, Olivine, Orthopyroxene

Hematite, Magnetite, Quartz

1.2.2 Compound Content

Ca, CaO, Chromium(III) Oxide, MgO, Sulfur Trioxide

Fe, Iron(III) Oxide, Silicon Dioxide

1.3 Transformation

1.3.1 Metamorphism

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1.3.2 Types of Metamorphism

Cataclastic Metamorphism, Contact Metamorphism

Not Applicable

1.3.3 Weathering

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1.3.4 Types of Weathering

Biological Weathering

Chemical Weathering

1.3.5 Erosion

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1.3.6 Types of Erosion

Chemical Erosion, Wind Erosion

Coastal Erosion, Wind Erosion

Anorthosite and Banded iron formation Formation

Formation of rocks is a long process and hence, Anorthosite and Banded iron formation formation sounds very interesting. According to the formation, all rocks are divided into :Igneous Rocks, Fossil Rocks and Metamorphic Rocks. Igneous rocks form by crystallization of magma or lava. The magma is made up of various components of pre-existing rocks which have been subjected to melting either at subduction zones or within the Earth's mantle. Igneous rocks are generally seen at mid ocean ridges or in intra-plate hotspots. Sedimentary rocks are formed when sediments accumulate gradually. As the sediments are buried they get compacted as more and more material is deposited on top. Eventually the sediments become so dense that they form a rock. Metamorphic rocks are rocks which once existed as igneous or sedimentary rocks but have been subjected to varying degrees of pressure and heat within the Earth's crust. Get to know all about formation of Anorthosite and Banded iron formation, composition of Anorthosite and Banded iron formation and their transformation.