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QAPF diagram with basalt/andesite field highlighted in yellow. Andesite is distinguished from basalt by SiO 2 > 52%. Andesite is field O2 in the TAS classification.. Andesite is an aphanitic (fine-grained) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals.
Magma can be found in the mantle or molten crust. ... [97] though it has been suggested that boninite is a variety of andesite crystallized from a primary magma. ...
For example, andesitic magmatism is associated with the formation of island arcs at convergent plate boundaries while basaltic magmatism is found at mid-ocean ridges during sea-floor spreading at divergent plate boundaries. On Earth, magma forms by partial melting of silicate rocks either in the mantle, continental or oceanic crust. Evidence ...
Fissure volcanoes pour out low viscosity basaltic magma from fissure vents to form the extrusive rock basalt. [2] Composite or stratovolcanoes often have andesitic magma and typically form the extrusive rock andesite. Andesitic magma is composed of many gases and melted mantle rocks. [2]
A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma into a more evolved, silica rich end member. Rock types of the tholeiitic magma series include tholeiitic basalt , ferro-basalt, tholeiitic basaltic andesite , tholeiitic andesite , dacite and rhyolite .
The Altiplano-Puna Magma Body (APMB), a magma body located within the Altiplano-Puna plateau approximately 10–20 km beneath the Altiplano-Puna Volcanic Complex (APVC) [1] in the Central Andes. High resolution tomography shows that this magma body has a diameter of ~200 km, a depth of 14–20 km, with a total volume of ~500,000 km 3 , [ 2 ...
The initial magma was basaltic, though this was replaced several hundred years later by more evolved, basaltic andesite magma. [20] Eruptions at Sand Mountain Field were fed by two or three magma chambers, [21] including a number of mafic magma sources over a brief span of distance and time. [22]
Basaltic over shoshonitic (both 25 and 21 m) to andesitic (post-Miocene) lavas are found in the southern Altiplano. [6] Ignimbrites deposited during eruptions of APVC volcanoes are formed by "boiling over" eruptions, where magma chambers containing viscous crystal-rich volatile-poor magmas partially empty in tranquil, non-explosive fashion.