[mass noun] A coarse-grained plutonic rock consisting chiefly of sodic plagioclase, quartz, and hornblende or other mafic minerals.‘fields of tonalite’[count noun] ‘the margins are invaded by mantle-derived tonalites’
- ‘Permian and Triassic plutonic complexes comprise monzonite, granite, granodiorite or tonalite with minor gabbro and diorite.’
- ‘There are enormous intrusions into many of these terrains; layered anorthosites, dyke swarms of basalts, and complexes of tonalite or diorite intrusions also occur.’
- ‘These plutons generally contain a variety of rock types, ranging from appinites and diorites through tonalites, granodiorites and rare syenites to ademellites and granites.’
- ‘The tonalite is characterized by a strong fabric defined by aligned plagioclase, hornblende and biotite that is interpreted to be a magmatic state deformation fabric formed during emplacement.’
- ‘The tonalite is gneissic, banded on a decimetre scale, and loaded with discrete mafic enclaves, metasedimentary xenoliths and garnet, feldspar and rutile xenocrysts, such that the body has a migmatitic appearance.’
Late 19th century: from Tonale Pass, northern Italy, + -ite.