Our website is made possible by displaying online advertisements to our visitors.
Please consider supporting us by disabling your ad blocker.
Tonalite
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.[1][2] Amphiboles and biotite are common in lesser quantities, while accessory minerals include apatite, magnetite and zircon.[3][4]
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%.[1]
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.[5] 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.[6]
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.[7]
Tonalites, together with granodiorites, are characteristic of calc-alkaline batholiths formed above subduction zones.[8]
- ^ a b Le Bas, M. J.; Streckeisen, A. L. (1991). "The IUGS systematics of igneous rocks". Journal of the Geological Society. 148 (5): 825–833. Bibcode:1991JGSoc.148..825L. CiteSeerX 10.1.1.692.4446. doi:10.1144/gsjgs.148.5.0825. S2CID 28548230.
- ^ "Rock Classification Scheme - Vol 1 - Igneous" (PDF). British Geological Survey: Rock Classification Scheme. 1: 1–52. 1999.
- ^ https://geologyscience.com/rocks/igneous-rocks/intrusive-igneous-rocks/tonalite/ Tonalite Page in Geology Science
- ^ Allaby, Michael (2013). "tonalite". A dictionary of geology and earth sciences (Fourth ed.). Oxford: Oxford University Press. ISBN 9780199653065.
- ^ Jackson, Julia A., ed. (1997). "tonalite". Glossary of geology (Fourth ed.). Alexandria, Virginia: American Geological Institute. ISBN 0922152349.
- ^ Streckeisen, A. (1 March 1976). "To each plutonic rock its proper name". Earth-Science Reviews. 12 (1): 1–33. doi:10.1016/0012-8252(76)90052-0.
- ^ 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.
- ^ SIGES Occitanie (Font-Romeu-Odeillo-Via), at sigesocc.brgm.fr; section "Carte géologique"; "Paléozoïque - Cycle hercynien... Tonalite à biotite et hornblende".
- ^ Topographical map extract (in Géoportail).
Previous Page Next Page
