Parental magma of the Skaergaard intrusion: constraints from melt inclusions in primitive troctolite blocks and FG-1 dykes |
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| Authors: | Jakob K Jakobsen Christian Tegner C Kent Brooks Adam J R Kent Charles E Lesher Troels F D Nielsen Michael Wiedenbeck |
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| Institution: | 1.Department of Earth Sciences,University of Aarhus,Aarhus C,Denmark;2.Nordic Volcanological Centre, Institute of Earth Sciences,University of Iceland,Reykjavik,Iceland;3.Geological Museum,Copenhagen K,Denmark;4.Department of Geosciences,Oregon State University,Corvallis,USA;5.Department of Geology,University of California, Davis,Davis,USA;6.Geological Survey of Denmark and Greenland,Copenhagen K,Denmark;7.Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum,Potsdam,Germany |
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| 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. |
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