What are felsic and mafic rocks?
In a widely accepted silica-content classification scheme, rocks with more than 65 percent silica are called felsic; those with between 55 and 65 percent silica are intermediate; those with between 45 and 55 percent silica are mafic; and those with less than 45 percent are ultramafic.
What type of rock is a felsic rock?
The class of rock which crystallizes from silicate minerals at relatively low temperatures and with relatively high percentage of silica is generally referred to as “felsic” rock. This class includes granite and rhyolite and is at the low temperature extreme of the Bowen reaction series.
What is felsic rock composition?
Felsic rocks are mostly feldspar (especially K-feldspar), at least 10% quartz, and less than 15% mafic minerals (biotite, hornblende).
What is a felsic volcanic rock?
Felsic volcanic rock. A light-colored, fine-grained or aphanitic extrusive or hypabyssal rock, with or without phenocrysts and composed chiefly of quartz and feldspar. This category is also used for felsic volcanic rock (aphanitic). Subtopics: Alkali-feldspar rhyolite.
Whats the definition of felsic?
Definition of felsic : consisting of or chiefly consisting of feldspar or feldspathoid quartz.
What is the difference between felsic and mafic?
Either in describing rocks or lava, mafic means that the lava or rock has less silica while felsic implies that the lava or rock has the most silica. 6. Mafic rocks are darker in color than felsic rocks.
What does felsic describe?
Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Felsic magma or lava is higher in viscosity than mafic magma/lava. Felsic rocks are usually light in color and have specific gravities less than 3.
Are felsic rocks intrusive or extrusive?
For example, a coarse-grained, felsic igneous rock is not only a granite, it is an intrusive igneous rock that formed from slow cooling and crystallization of a body of magma within the earth’s crust.
What color are felsic igneous rocks?
light
Note that felsic rocks are light in color; intermediate rocks range through grays, and mafic rocks are black in color. Ultramafic rocks (peridotite) may range black to olive green (dunite) from the mineral olivine.
How is felsic rock formed?
Felsic rocks are formed out of the cooling and crystallization of felsic magma or lava. Felsic magma forms out of the melting material beneath Earth’s continental crust.
What is felsic rock used for?
Saprolite.) Felsic, on the other hand, is used for silicate minerals, magmas, and rocks which have a lower percentage of the heavier elements, and are correspondingly enriched in the lighter elements, such as silicon and oxygen, aluminum, and potassium.
Where is felsic rock found?
Some of the oldest surface felsic rocks on Earth had been found in the Canadian Shield, Australia, and Africa with ages varying between 2.5 and 3.8 billion years.
What is a felsic extrusive igneous rock?
Felsic extrusive igneous rocks (e.g., rhyolite) are usually light in color (though obsidian is a notable exception; see below) because they are rich in minerals like feldspar that contain a lot of Al, Na, or K.
What is the meaning of felsic?
What texture is felsic rock?
porphyritic texture
Volcanic rocks, especially felsic and intermediate, often have a porphyritic texture characterized by visible crystals floating in a fine-grained groundmass.
Where do felsic rocks occur?
The felsic magma is differentiated from mafic materials within the crust because of their varying densities and because mafic magma crystallizes first. Felsic rocks are mostly found within and on Earth’s continental crust because of the lighter and less dense elements and minerals that compose them.
How do you tell if a rock is felsic or mafic?
Felsic minerals (quartz, K feldspar, etc) are light colored while mafic minerals (hornblende, pyroxenes) are normally dark colored. Felsic minerals have the lowest melting points (600 to 750 °C) and mafic minerals have higher melting points (1000 to 1200 °C).