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Olivinites, clinopyroxenites and mixed olivine-clinopyroxene rocks (wherlites) are the most common plutonic ultramafic rocks found in association with foidolites, feldspathoid syenites and carbonatites. Although they look a lot like ultramafic rocks found in other lithological settings (e.g., layered mafic intrusions), their mineralogical and geochemical characteristics are quite distinct. For example, these rocks commonly contain abundant perovskite (CaTiO3) and Ti-rich magnetite, but not chromite. Their textures are suggestive of crystal settling as the principal mechanism of their formation, but enrichment of early magmas in Mg and Ca through thermogravitational diffusion may be at play, too. The upper photograph (at right) shows olivinite from Lesnaya Varaka (Kola, Russia), as seen under the microscope in plane-polarized light (PPL, left) and in crossed polars (XP, right). The lower photograph shows clinopyroxenite from Turiy Mys (Kola, Russia), also in PPL and XP. In addition to ferromagnesian silicates (colorless olivine and pale-green to pale-yellow diopside), both rocks contain intercumulus magnetite (opaque).
Olivinite, Lesnaya Varaka (Kola, Russia)

Clinopyroxenite, Turiy Mys (Kola, Russia)