Trondhjemite

Trondhjemite

Igneous rock
Tonalite–trondhjemite–granodiorite migmatite (left) and trondhjemitic gneiss (right) from northern China
Composition
oligoclase, other plagioclase

Trondhjemite is a leucocratic (light-colored) intrusive igneous rock. It is a variety of tonalite in which the plagioclase is mostly in the form of oligoclase. ^[1] Trondhjemites that occur in the oceanic crust or in ophiolites are usually called plagiogranites. ^{[2] [3]}

Trondhjemite is common in Archean terranes occurring in conjunction with tonalite and granodiorite as the TTG (tonalite–trondhjemite–granodiorite) orthogneiss suite. ^[4] Trondhjemite dikes also commonly form part of the sheeted dike complex of an ophiolite. ^[3]

The rock type was first described by Victor Goldschmidt in 1916. The name of the rock type is derived from the city of Trondheim, Norway. ^[1]

Notes

1. Jackson 1997, "trondjhemite".
2. Jackson 1997, "plagiogranite".
3. Philpotts & Ague 2009, pp. 367, 372.
4. Philpotts & Ague 2009, p. 398.

References

• Jackson, Julia A., ed. (1997). "Friable". Glossary of geology (Fourth ed.). Alexandria, Virginia: American Geological Institute. ISBN   0922152349.
• Philpotts, Anthony R.; Ague, Jay J. (2009). Principles of igneous and metamorphic petrology (2nd ed.). Cambridge, UK: Cambridge University Press. ISBN   9780521880060.

Further reading

• Best, Myron G. (2002) Igneous and Metamorphic Petrology, Blackwell Publishing, 2nd ed. ISBN   1-4051-0588-7