Preliminary account of kimberlite intrusions from the Frederikshåb district, South-West Greenland

Abstract

Kimberlite intrusions from three localities, Nigerdlikasik, Pyramidefjeld and Midternæs, show closely comparable petrographicaI, mineralogical and geochemical features. They contain ultramafic gamet, spinel and phlogopite peridotite inclusions which appear to have been derived from the Upper MantIe, though scapolite granulite nodules in the Nigerdlikasik kimberlite must have originated in the lower crust. Garnet and spinel peridotite were sampled at successively higher levels by the kimberlite magma and micaceous peridotites wete produced by phlogopitisation of some of these inclusions during transport. Generation of the kimberlites took place during, the early Mesozoic and forms part of the Mesozoic pattern of igneous activity in South-West Greenland.