Formation of Coquina and Dacite

Coquina

Dacite

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1 Formation

1.1 Formation

Coquina is a sedimentary rock which is formed when billions of small clam-like seashell, called Coquina, or cockleshell are die and hence are deposited, buried and turns into a rock when pressure is applied.

Dacitic magma is formed by the subduction of young oceanic crust under a thick felsic continental plate. Further, the Oceanic crust is hydrothermally altered as quartz and sodium are added.

1.2 Composition

1.2.1 Mineral Content

Apatite, Augite, Bronzite, Calcite, Chert, Chlorite, Clay Minerals, Epidote, Feldspar, Garnet, Micas, Muscovite or Illite

Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon

1.2.2 Compound Content

CaO, Carbon Dioxide, Iron(III) Oxide, MgO

Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide

1.3 Transformation

1.3.1 Metamorphism

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1.3.2 Types of Metamorphism

Not Applicable

Burial Metamorphism, Cataclastic Metamorphism

1.3.3 Weathering

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1.3.4 Types of Weathering

Biological Weathering, Chemical Weathering, Mechanical Weathering

1.3.5 Erosion

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1.3.6 Types of Erosion

Coastal Erosion, Sea Erosion, Water Erosion, Wind Erosion

Chemical Erosion

Coquina and Dacite Formation

Formation of rocks is a long process and hence, Coquina and Dacite 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 Coquina and Dacite, composition of Coquina and Dacite and their transformation.