Chart illustrating the meaning of peralkaline, metaluminous, peraluminous and subaluminous

Peraluminous rocks are igneous rocks that have a molecular proportion of aluminium oxide higher than the combination of sodium oxide, potassium oxide and calcium oxide.[1] This contrasts with peralkaline in which the alkalis are higher, metaluminous where aluminium oxide concentration is lower than the combination, but above the alkalis, and subaluminous in which aluminia concentration is lower than the combination. Examples of peraluminous minerals include biotite, muscovite, cordierite, andalusite and garnet.

Peraluminous corresponds to the aluminum saturation index values greater than 1.[2]

Peraluminous magmas can form S-type granitoids and have been linked to collisional orogenies and to the formation of tin, tungsten and silver deposits such as those in the Bolivian tin belt.[3]

References

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  1. ^ Blatt, Harvey and Robert J. Tracy, Petrology, Freeman, 2nd ed., 1995, p. 516 ISBN 0-7167-2438-3
  2. ^ Ludington, Steve; Victor G. Mossotti (6 August 2008). "Aluminum saturation, alkalinity, and magma series". 33rd International Geologic Congress. Retrieved 22 September 2013.
  3. ^ Mlynarczyk, Michael S.J.; Williams-Jones, Anthony E. (2005). "The role of collisional tectonics in the metallogeny of the Central Andean tin belt". Earth and Planetary Science Letters. 240 (3–4): 656–667. Bibcode:2005E&PSL.240..656M. doi:10.1016/j.epsl.2005.09.047.


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Muscovite

metamorphic rock or as a secondary mineral resulting from the alteration of topaz, feldspar, kyanite, etc. It is characteristic of peraluminous rock, in which

Peralkaline rock

proportion of plagioclase relative to mafic minerals. Agpaitic rock Metaluminous rock Peraluminous rock Philpotts, Anthony R.; Ague, Jay J. (2009). Principles

Igneous rock

K2O/Na2O >3. Peralkaline – rocks containing molar (K2O + Na2O)/Al2O3 >1. Peraluminous – rocks containing molar (K2O + Na2O + CaO)/Al2O3 <1. In older terminology

Granite

thus more common as volcanic rock (rhyolite). They are also orogenic but range from metaluminous to strongly peraluminous. Although both I- and S-type

Hadean zircon

on the Comment on Nature of Biotites in Alkaline, Calc-alkaline and Peraluminous Magmas". 37(5), 1031–1035. Nutman, A., Mojzsis, S., & Friend, C. (1997)

Syenite

peralkaline with high proportions of alkali elements relative to aluminum, or peraluminous with a higher concentration of aluminum relative to alkali (predominantly

Bohus granite

narrow range of high silica contents (68–75 wt% SiO2) and are mildly peraluminous. The Bohus granites have also high uranium and thorium contents. The

Lundy

2017). "Age and petrogenesis of the Lundy granite: Paleocene intraplate peraluminous magmatism in the Bristol Channel, UK" (PDF). Journal of the Geological