Definition of troctolite in US English:



  • Gabbro made up mainly of olivine and calcic plagioclase, often having a spotted appearance likened to a trout's back.

    • ‘Hydrated troctolite is most voluminous in boudin necks, the hinge regions of map-scale folds, and in shear zones, all regions where structural features may have favored local fluid infiltration.’
    • ‘Metasomatic anorthosite formed by replacement of layered gabbroic troctolite in the Skaergaard intrusion is shown here.’
    • ‘Similar advantages in melt behaviour are also achieved by using troctolite as the iron and magnesium source rather than traditional materials.’
    • ‘The youngest sills are undeformed and crosscut older foliated troctolite sills, which in turn crosscut isoclinally folded hybrid gabbro-troctolite-anorthosite complexes.’
    • ‘There is some grain size reduction of the troctolite adjacent to the anorthosite, indicating a chilling effect.’


Late 19th century: from German Troklotit, from Greek trōktēs, a marine fish (taken to be ‘trout’).