Geochemical mapping and prospecting in Greenland — A review of results and experience

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Reconnaissance and regional geochemical surveys based on stream sediment and water samples been carried out by the Geological Survey of Greenland over the past 10 years. The areas covered represent a wide variety of geological environments and physiographic conditions. The surveys were based on low-density sampling (1 sample per 20–30 km 2 ) and covered Archean gneiss terrain in West Greenland, as well as the Paleozoic platform and fold belt in North Greenland. Regional multi-element surveys were conducted as part of U exploration programmes in East and South Greenland. In addition several prospects and anomalies were sampled in detail, and the dispersion of elements in stream sediment, stream water, soil, and aquatic moss is currently being studied in new areas. The conditions for geochemical dispersion in North and northeast Greenland are comparable with those of desert terrains. The streams flow periodically, and weathering and transport is predominantly mechanical. The dispersion trains are rather short and depend on the topography and the flow rate. Variations in the chemical composition of stream sediment at a sample site can be considerable. The terrain of West and South Greenland resembles Scotland and northern Scandinavia. A thin cover of morainic drift supports a low vegetation, and the influence of chemical agents like ground water and organic matter is noticed to a varying degree in the dispersion processes. Geochemical mapping, based on low-density drainage samples, has revealed large-scale lithogeochemical patterns, including metallogenic provinces and potential ore zones. In East Greenland the extent of hydrothermal mineralization in a major fault zone is outlined by F and U in stream water. In North Greenland the Cambro-Ordovician platform margin is identified as having potential for Zn and Ba deposits. In West Greenland geochemical maps based on reconnaissance gamma spectrometry together with evidence from drainage geochemistry point to the Godthåbsfjord area as a potential province for W, base metal and Au deposits. In South Greenland reconnaissance drainage geochemistry defines a U province, as well as a province influenced by alkaline magmatism. The geochemical maps produced contribute to an understanding of the structural development of the crust and are of assistance to geological mapping. Prospecting by geochemical methods, from regional to detailed scale, has led to the discovery of many mineral occurrences and prospects (some with economic potential) in previously unknown regions in Greenland.