trondhjemite

{{short description|Light-colored intrusive igneous rock}}

{{Infobox rock

|image = File:HKU 香港大學 Stephen Hui Geological Museum 許士芬地質博物館 the oldest rocks from China TTG Migmatite Taishan complex n old trondhjemitic gneiss Baijiafen Anshan Oct 2016 Lnv.jpg

|name=Trondhjemite

|type=Igneous

|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.{{sfn|Jackson|1997|loc="trondjhemite"}} Trondhjemites that occur in the oceanic crust or in ophiolites are usually called plagiogranites.{{sfn|Jackson|1997|loc="plagiogranite"}}{{sfn|Philpotts|Ague|2009|pp=367, 372}}

Trondhjemite is common in Archean terranes occurring in conjunction with tonalite and granodiorite as the TTG (tonalite–trondhjemite–granodiorite) orthogneiss suite.{{sfn|Philpotts|Ague|2009|p=398}} Trondhjemite dikes also commonly form part of the sheeted dike complex of an ophiolite.{{sfn|Philpotts|Ague|2009|pp=367, 372}}

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.{{sfn|Jackson|1997|loc="trondjhemite"}}