Geochemical evolution of the Ivigtut granite, South Greenland: a fluorine-rich “A-type” intrusion

The Ivigtut alkali granite stock lies within the Proterozoic Gardar alkaline igneous province of South Greenland. This small (300 m across) granite body once contained the worldʹs largest body of cryolite, now mined out. The granite surrounding the cryolite body has been extensively metasomatised by F- and CO2-rich fluids, leading to zonal enrichment in HFSE and REE. Variations in the Rb–Sr and Sm–Nd systematics of the granite can be correlated with the degree of metasomatism. Unaltered granites have highly variable initial 87Sr/86Sr, and initial εNd ratios of around −3, suggesting formation through crustal contamination of a mantle-derived magma. Metasomatised granites show higher initial εNd ratios, which can be interpreted to suggest that the metasomatic fluid was derived from a mantle source.