Hydrothermal alteration of Tertiary layered gabbros, east Greenland

Abstract

In the early Tertiary, layered gabbro intrusions of central East Greenland represented heat sources for large-scale hydrothermal circulation during the initial stages of the opening of the North Atlantic ocean. Field and petrographic investigation of the Skaergaard and Nordre Aputiteq intrusions, the Kruuse Fjord and Kap Edvard Holm complexes, and the Miki Fjord macrodike suggest that the style and complexity of hydrothermal alteration in each pluton is closely related to its magmatic and structural history during emplacement and cooling. Characteristic assemblages of hydrothermal minerals are found within all the intrusions, but each gabbro is characterized by a unique distribution and abundance of mineralized veins, miarolitic cavities, and metasomatized gabbros. Geometric relations of the various vein sets suggest that the permeability in the cooling gabbros changed spatially and temporally as older fracture systems and cavities were sealed by secondary minerals and as new fractures formed. -from Authors