A Hawaiian beginning for the Iceland plume: Modelling of reconnaissance data for olivine-hosted melt inclusions in Palaeogene picrite lavas from East Greenland

Compositions of parental and primary melts are modelled for olivine-hosted melt inclusions in three, Palaeogene, proto-Iceland plume picrite samples from East Greenland. The samples represent three stages in the magmatic evolution: (1) the early prespreading volcanics of the Lower Basalts, (2) the early plateau basalts in the Milne Land Formation and (3) the steady stage plateau basalt of the Geikie Plateau Fort-nation. The observations suggest that the host lavas are variably mixed with melts and material from the wall rocks of the feeder system. Pressure estimates based on K-D between olivine and reconstructed melt composition suggests the melts to be trapped in their hosts during ascent from magma chambers near the base of the East Greenland crust. CaO/Al2O3 ratios suggest initiation of melting in the proto-Iceland plume at pressures up to 5-6 GPa and segregation depths mainly between 3 and 4 GPa. Early melts show marked similarities in major and trace elements with primary Hawaiian type melts. It is proposed that the continental separation in the North Atlantic was influenced by a pre-seafloor spreading rise of a "Hawaiian" type plume with a significant component of recycled basalt. (C) 2006 Elsevier B.V. All rights reserved.