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Tonalite is an igneous rock, (Intrusive rock) 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. and biotite are common in lesser quantities, while accessory include apatite, magnetite and
Tonalite Page in Geology Science (2025). 9780199653065, Oxford University Press. ISBN 9780199653065
In older references tonalite is sometimes used as a synonym for quartz diorite. However the current IUGS QAPF diagram 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 Italy and Alps. The name was first applied by Gerhard vom Rath in 1864. (1997). 9780922152346, American Geological Institute. ISBN 9780922152346 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.
Trondhjemite is an orthoclase-deficient variety of sodium-rich tonalite with minor biotite as the only mafic mineral, named after Norway's third largest city, Trondheim.
Tonalites, together with , are characteristic of calc-alkaline formed above subduction zones.
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