Tonalite

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A piece of tonalite on red granite gneiss from Tjörn, Sweden
QAPF diagram with tonalite field highlighted

Tonalite is an

QAPF) content of the rock.[1][2] Amphiboles and biotite are common accessory minerals.[3]

In older references tonalite is sometimes used as a synonym for

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.[4] 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.[5]

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.[6]

Tonalites, together with

subduction zones.[7]

References

  1. ^
    S2CID 28548230
    .
  2. ^ "Rock Classification Scheme - Vol 1 - Igneous" (PDF). British Geological Survey: Rock Classification Scheme. 1: 1–52. 1999.
  3. ISBN 9780199653065
    .
  4. ISBN 0922152349
    .
  5. doi:10.1016/0012-8252(76)90052-0
    .
  6. ^ Jackson 1997, "trondhjemhite".
  7. doi:10.1016/j.earscirev.2013.05.006
    .

External links

  • Media related to Tonalite at Wikimedia Commons
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