1 Department of Geoscience, Science and Technology, Aarhus University2 Department of Earth Sciences, University of Aarhus, Høegh-Guldbergs Gade 2, 8000, Aarhus C, Denmark3 Depart Geology, Copenhagen4 University of Oregon5 GEUS6 Department of Geoscience, Science and Technology, Aarhus University
Abstract Troctolite blocks with compositions akin to the Hidden Zone are exposed in a tholeiitic dyke cutting across the Skaergaard intrusion, East Greenland. Plagioclase in these blocks contains finely crystallised melt inclusions that we have homogenised to constrain the parental magma to 47.4–49.0 wt.% SiO2, 13.4–14.9 wt.% Al2O3 and 10.7–14.1 wt.% FeOT. These compositions are lower in FeOT and higher in SiO2 than previous estimates and have distinct La/SmN and Dy/YbN ratios that link them to the lowermost volcanic succession (Milne Land Formation) of the regional East Greenland flood basalt province. New major- and trace element compositions for the FG-1 dyke swarm, previously taken to represent Skaergaard magmas, overlap with the entire range of the regional flood basalt succession and do not form a coherent suite of Skaergaard like melts. These dykes are therefore re-interpreted as feeder dykes throughout the main phase of flood basalt volcanism.
Contributions To Mineralogy and Petrology, 2010, Vol 159, Issue 1, p. 61-79