| Igneous rock | |
 | |
| 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 V.M. Goldschmidt in 1916. The name of the rock type is derived from the city of Trondheim, Norway.[1]