Parental magma of the Skaergaard intrusion: constraints from melt inclusions in primitive troctolite blocks and FG-1 dykes.

• Main Authors: Jakobsen, J.K., Tegner, Christian, Brooks, Kent, Kent, Adam, Lesher, Charles, Nielsen, Troels
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2010
• Subjects: East Greenland; Greenland; Milne Land
• Online Access: https://pure.au.dk/portal/en/publications/289ece69-3b90-4e25-8ddb-4af042551b25

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.