Prospecting for base and noble metals in the Ingia area, West Greenland: analytical results

The Íngia area of the northern Umanak district is underlain by Archaean gneiss and Lower Proterozoic supracrustals. The latter were deposited in an epicontinental back-arc basin. They comprise a thick basal unit of shallow marine quartzites overlain by a thin wedge of mafic metavolcanics and uppermost a thick sequence of metaturbidites.

Stratiform pyrrhotite mineralisation occurs at several levels in the supracrustal pile. An investigated pyrrhotite horizon associated with the metavolcanics contains base/noble metals in the order of 500 ppm Zn, 400 ppm Cu, 20 ppm Pb, 15 ppb Pd and 4 ppb Au. Such mineralisation offers in itself possibilities for economic metal concentrations, and also constitutes a potential source rock for epigenetic mineralisation.

Epigenetic quartz vein mineralisation is mainly known from boulder finds. It is dominated by pyrrhotite, but also chalcopyrite and rare arsenopyrite, galena and scheelite occur. Gold contents of up to 371 ppb have been encountered.

A geochemical survey using stream sediment samples and pan samples has outlined two areas with anomalous values for gold-arsenic-tungsten and gold-arsenic-cobalt respectively. The highest gold value is 2.6 ppm in a pan sample.

The Íngia area is considered to have a potential for gold/base metal deposits of vein or stratiform type.