Controls on Corundum Formation: Metasomatism of Ultramafic Rock, Nattivit, South-East Greenland.

This article focuses on the geotectonic setting, mineralogy, geochemistry, and formation processes of plumasite-type corundum occurrences in the Nattivit area of the Isertoq Terrane, South-East Greenland. It documents how syn-tectonic, peraluminous, calc-alkaline G2 pegmatites, dated at 1843 ± 4 Ma and derived from partial melts of lower crustal mafic granulite or subducted oceanic crust during the Nagssugtoqidian Orogeny, intruded ultramafic rocks (lherzolite and dunite), triggering metasomatic reactions that formed corundum with characteristic trace element signatures. The study identifies distinct metasomatic zones with varying mineral assemblages and demonstrates that trace elements such as Cr, Fe, Ti, and V controlling corundum color are primarily sourced from the ultramafic host rocks, while elements like Al, Ca, K derive mainly from the pegmatites. The findings suggest that plumasite-type corundum typically forms in the upper plate of collisional orogens where specific pegmatite compositions interact with mafic-ultramafic rocks, and that corundum trace element geochemistry can serve as a fingerprint for its geological origin and tectonic setting.