Tonalite is an igneous, plutonic (intrusive) rock, of felsic composition, with phaneritic (coarse-grained) texture. Feldspar is present as plagioclase (typically oligoclase or andesine) with alkali feldspar making up less than 10% of the total feldspar content. Quartz (SiO2) is present as more than 20% of the total quartz-alkali feldspar-plagioclase-feldspathoid (QAPF) content of the rock. Amphiboles and biotite are common accessory minerals.
In older references tonalite is sometimes used as a synonym for quartz diorite. However the current IUGS classification defines tonalite as having greater than 20% quartz, while quartz diorite varies its quartz content from 5 to 20%.
The name is derived from the type locality of tonalites, adjacent to the Tonale Line, a major structural lineament and mountain pass, Tonale Pass, in the Italian and Austrian Alps. The name was first applied by Gerhard vom Rath in 1864. The term adamellite was originally applied by A. Cathrein in 1890 to orthoclase-bearing tonalite (likely a granodiorite) at Monte Adamello, Italy, in 1890, but later came to refer to quartz monzonite, and is now a deprecated term.
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- "Rock Classification Scheme - Vol 1 - Igneous" (PDF). British Geological Survey: Rock Classification Scheme. 1: 1–52. 1999.
- Allaby, Michael (2013). "tonalite". A dictionary of geology and earth sciences (Fourth ed.). Oxford: Oxford University Press. ISBN 9780199653065.
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- Jackson 1997, "trondhjemhite".
- Castro, Antonio (September 2013). "Tonalite–granodiorite suites as cotectic systems: A review of experimental studies with applications to granitoid petrogenesis". Earth-Science Reviews. 124: 68–95. doi:10.1016/j.earscirev.2013.05.006.
- Media related to Tonalite at Wikimedia Commons