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.
What produces felsic magma?
It has been suggested that felsic magmas found at subduction-zone volcanoes are produced by mechanisms including fractional crystallization with or without crustal assimilation8, partial melting of the crust9,10, and partial melting of metasomatised silica-excess pyroxenite mantle11,12.
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.
Is felsic magma intrusive?
Intrusive rocks that were formed deep in the earth’s crust are called plutonic rocks and are generally coarse grained (mineral grains greater than 1 millimeter in diameter), large, and often associated with mountain‐building. Mafic, felsic, and intermediate intrusive rocks.
Where is felsic magma formed?
A. Intermediate and felsic magmas form around convergent margins with a subduction zone. 3. these volcanic mountain chains often form arc shapes, because that is the shape produced when a flat plate (tectonic plate) intersects a sphere (Earth).
Is felsic magma explosive?
Felsic lavas are not as hot, high in silica and volatiles, and have a high viscosity. They are thick and gooey and resist flowing. Their high volatile content makes them potentially highly explosive.
How is felsic 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.
How magma is formed?
Magma forms from partial melting of mantle rocks. As the rocks move upward (or have water added to them), they start to melt a little bit. These little blebs of melt migrate upward and coalesce into larger volumes that continue to move upward. They may collect in a magma chamber or they may just come straight up.
Why are there different compositions of magma?
The composition of magma depends on the rock it was formed from (by melting), and the conditions of that melting. Magmas derived from the mantle have higher levels of iron, magnesium, and calcium, but they are still likely to be dominated by oxygen and silicon.
What rocks are created from felsic lava and magma?
Felsic magma is viscous and does not flow easily. Most felsic magma will stay deeper in the crust and will cool to form igneous intrusive rocks such as granite and granodiorite.
What do felsic rocks contain?
Felsic rocks are mostly feldspar (especially K-feldspar), at least 10% quartz, and less than 15% mafic minerals (biotite, hornblende).
What is the meaning of felsic?
Definition of felsic
: consisting of or chiefly consisting of feldspar or feldspathoid quartz.
Is felsic light or dark?
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).
What melts first mafic or felsic?
The most mafic minerals in a melt (i.e. those with the highest melting point) will be the first to crstallize out, leaving an increasingly felsic magma.
Is felsic high in silica?
Whereas, felsic rocks are rich in silica and aluminium along with oxygen, sodium and potassium that gives the light shade for these rocks.
What is the viscosity of basaltic magma?
Viscosity of Magmas
Thus, basaltic magmas tend to be fairly fluid (low viscosity), but their viscosity is still 10,000 to 100,0000 times more viscous than water.
Why does basalt have no visible crystals?
Cooled lava forms basalt with no visible crystals. Why are there no visible crystals? Extrusive igneous rocks cool much more rapidly than intrusive rocks. There is little time for crystals to form, so extrusive igneous rocks have tiny crystals (figure 5).
