tonalite
/ˈtɒn(ə)lʌɪt
/noun [mass noun] Geology
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.
Derivatives
tonalitic
- The Archaean Baidrag complex, composed of tonalitic gneiss, granulite and amphibolite, with minor marble and quartzite, has been interpreted as a microcontinental block.
- In general, the strain intensity is commonly considerably higher in the granodiorite dykes than in the tonalitic wall-rock gneisses, which probably reflects strain localization into the dykes.
- Of these, the vast majority comprise late Archaean tonalitic gneiss with various mafic, ultramafic and metasedimentary enclaves, collectively known as ‘grey gneiss’.
Origin
Late 19th century: from Tonale Pass, northern Italy, + -ite1.