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In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz. [1] It is contrasted with mafic rocks, which are richer in magnesium and iron. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium ...
Viscosity is a key melt property in understanding the behaviour of magmas. Whereas temperatures in common silicate lavas range from about 800 °C (1,470 °F) for felsic lavas to 1,200 °C (2,190 °F) for mafic lavas, [24] the viscosity of the same lavas ranges over seven orders of magnitude, from 10 4 cP (10 Pa⋅s) for mafic lava to 10 11 cP ...
Archean felsic volcanic rocks also have high zircon abundance. Incompatible elements, like zirconium, are reluctant to substitute into early-forming crystals. [17] As a result, they tend to remain in the melt. In strongly fractionated felsic magma, zircon is easily saturated. As a result, zircon is common in felsic rocks. [38]
There are three main types of volcanic eruption: Magmatic eruptions are the most well-observed type of eruption. They involve the decompression of gas within magma that propels it forward. Phreatic eruptions are driven by the superheating of steam due to the close proximity of magma.
Volcanoes with rhyolitic magma commonly erupt explosively, and rhyolitic lava flows are typically of limited extent and have steep margins because the magma is so viscous. [15] Felsic and intermediate magmas that erupt often do so violently, with explosions driven by the release of dissolved gases—typically water vapour, but also carbon dioxide.
The lighter felsic magma floats on the mafic magma without significant mixing. [46] Less commonly, felsic magmas are produced by extreme fractional crystallization of more mafic magmas. [47] This is a process in which mafic minerals crystallize out of the slowly cooling magma, which enriches the remaining liquid in silica. If the erupted magma ...
Granite. Granite (/ ˈɡrænɪt / GRAN-it) is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground.
Felsic magmas can erupt at ... Intermediate lavas form andesite domes and block lavas and may occur on steep ... [18] They are also commonly hotter than felsic lavas ...