ALKALINE ROCKS IN GREENLAND
Kimberlites and related rocks

Sven Monrad Jensen, Troels Nielsen, Frands Schjøth (Department of Economic Geology), Lotte Melchior Larsen (Department of Geological Mapping).b> Stefan Bernstein, GEUS; Rikke Harlou, University of Durham;

Alkaline rocks may host some special and unusual deposits of economic interest such as diamonds, zirconium, tantalum, etc. GEUS conducts a number of focussed studies on these rocks in order to provide basic knowledge and expertise to the mining industry. Kimberlites occur as swarms of mainly dykes and sheets over large areas in West Greenland, reaching from the Ivittuut area in the south (65ºN) to the Uummannaq region in the north (71ºN). In the region between Maniitsoq and Sisimiut (65–67ºN) they have been the subject of intensive exploration activities from mining companies since the 1990s. Some of the rocks have yielded diamonds, mainly micros but also a few macros, most recently in 2004. GEUS contributes to the understanding of the distribution and genesis of these rocks by conducting field studies, mineralogical and petrological studies, and age dating, financed by the Bureau of Minerals and Petroleum in Greenland (BMP). GEUS also takes part in promotion activities instigated by the BMP. Further, GEUS acts as data repository for the huge amount of company data on these rocks obtained over the last decade. Recently, the existing knowledge, including a comprehensive data set from released company reports, was collated in a report with a DVD.

Key publications from the Survey
Larsen, L.M. & Rex, D.C. 1992: A review of the 2500 Ma span of alkaline-ultramafic, potassic and carbonatitic magmatism in West Greenland. Lithos 28, 367–402.

Jensen, S. M., Hansen, H., Secher, K., Steenfelt, A., Schjødt, F. & Rasmussen, T. M. 2002. Kimberlites and other ultramafic alkaline rocks in the Sisimiut–Kangerlussuaq region, southern West Greenland. Geology of Greenland Survey Bulletin 191, 57–66.

Jensen, S.M., Lind, M., Rasmussen, T.M., Schjøth, F. & Secher K. 2003: Diamond exploration data from West Greenland. Danmarks og Grønlands Geologiske Undersøgelse Rapport 2003/21, 50 pp.+ DVD.