Epithermal gold and massive sulphide mineralisation in oil impregnated palaeogene volcanic rocks of Ubekendt Ejland, West Greenland

The presence of chalcedony and fibrous silica possibly replacing amorphous silica suggest that the quartz-carbonate veins formed at a shallow level in hydrothermal conduits. The quartz-carbonate veins are similar to epithermal Au-rich vein mineralisations described from other volcanic terrains associated with organic-rich sediments, in terms of geological setting, vein mineralogy, alteration of wall rocks and the evidence of migration of hydrocarbons (see e.g. Sketchley and Sinclair 1991; Sherlock and Lehrman 1995; Sillitoe et al. 2002). The vein mineralogy and alteration assemblage further suggest the mineralisation is a low sulphidation type (e.g. Bonham 1988). The presence of Fe-Pb-Zn sulphides in several veins may indicate that the sampled level of the veins is below that of precious metal deposition, that according to the model of Buchanan (1981) would appear above that of base metal sulphides. Our findings suggest there is a potential for economic precious metal mineralisation on Ubekendt Ejland.