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

Abstract

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 world's 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 Sr-87/Sr-86, and initial epsilon(Nd) ratios of around -3, suggesting formation through crustal contamination of a mantle-derived magma. Metasomatised granites show higher initial epsilon(Nd) ratios, which can be interpreted to suggest that the metasomatic fluid was derived from a mantle source.