Occurrences of kimberlite, lamproite and ultramafic lamprophyre in Greenland

Kimberlite, lamproite and ultramafic lamprophyre may be host rocks for diamonds. Localities with occurrences of such rocks in Greenland have been compiled in an overview table given here as appendix 1, and in more detailed tables that are available on request from GGU.

 The rocks in question are concentrated in West Greenland. West Greenland from 60°N to 72°N houses at least four swarms of kimberlite, one swarm of lamproite and one lamproite pipe, and seven swarms of ultramafic or strongly potassic lamprophyre. Ages range from Proterozoic (c. 1800 Ma) to Mesozoic (120 Ma).

 The field relations and petrography of each swarm is reviewed. The whole-rock geochemistry of each rock group is discussed and illustrated in a few plots. Many swarms tend to possess individual chemical characteristics, distinct for each swarm. Of the kimberlites, the Sukkertoppen swarm seems to have originated at the deepest level in the mantle, in accordance with its occurrence well within the undisturbed Archaean craton.

 Sparse microdiamonds have been found in connection with the Pyramidefjeld-Midternæs and Sarfartoq swarms and in an unsupported occurrence near Fiskenæsset. The best diamond potential is considered to be possessed by the Sukkertoppen kimberlite swarm and a dyke swarm in the Disko Bugt region of ultramafic lamprophyre with affinities to olivine lamproite.