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Some examples of felsic rocks include granite and rhyolite, while examples of mafic rocks include gabbro and basalt. [1] According to the Encyclopædia Britannica, color indices, 0–50 are felsic, 50–90 are mafic, and 90–100 are ultramafic. [6] An online geology textbook provides an example of the use of another classification scheme, in ...
This is particularly true of a series of ultramafic-mafic layered intrusions in the Yilgarn Craton of ~2.8 Ga and associated komatiite volcanism and widespread tholeiitic volcanism. Plume magmatism is an effective mechanism for explaining the large volumes of magmatism required to inflate an intrusion to several kilometres thickness (up to and ...
Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar (typically andesine), biotite, hornblende, and sometimes pyroxene.The chemical composition of diorite is intermediate, between that of mafic gabbro and felsic granite.
Peridotite, a type of ultramafic rock. Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are usually composed of greater than 90% mafic minerals (dark colored, high magnesium and iron content).
Large igneous provinces (LIPs) are defined as "mainly mafic (+ ultramafic) magmatic provinces with an areal extent >0.1 Mkm 2 and igneous volume >0.1Mkm 3, that have intraplate characteristics, and are emplaced in a short duration pulse or multiple pulses (less than 1–5 Ma) with a maximum duration of <c.50 Ma".
In the early 20th century there was a lively discussion on the relative importance of the process in igneous differentiation. [ 5 ] [ 6 ] More recent research has shown, however, that assimilation has a fundamental role in altering the trace element and isotopic composition of magmas, [ 7 ] in formation of some economically important ore ...
Granodiorite is felsic to intermediate in composition. It is the intrusive igneous equivalent of the extrusive igneous dacite . It contains a large amount of sodium (Na) and calcium (Ca) rich plagioclase, potassium feldspar , quartz , and minor amounts of muscovite mica as the lighter colored mineral components.
The mafic rocks also typically have a higher density than felsic rocks. The term roughly corresponds to the older basic rock class. [9] Mafic lava, before cooling, has a low viscosity, in comparison with felsic lava, due to the lower silica content in mafic magma. Water and other volatiles can more easily and gradually escape from mafic lava.