Rb-Sr studies of the major alkaline igneous complexes within the Precambrian Gardar Province of south Greenland indicate that the magmatic activity is divisible into three phases, referred to as Early (1300 m.y.), Mid (1250 m.y.) and Late (1165 m.y.) Gardar, respectively. Initial 87Sr/86Sr ratios for the majority of the Gardar magmas were low (0.702-0.704) suggesting derivation from a primitive (mantle) source; some complexes have moderately elevated ratios (0.704-0.707) attributed to varying degrees of contamination by older granitic basement. Two complexes (Ilimaussaq and Ivigtut), both highly differentiated and having high volatile contents, had high (0.707) initial ratios that cannot be explained by such bulk assimilation mechanisms. For these, it is suggested that preferential leaching of B7Sr from the surrounding crust before and during intrusion can account for the elevated values. Rb-Sr investigations of the Red Wine (Labrador) and Norra Farr (Sweden) agpaitic complexes show that the former (1350 m.y.) may well have been emplaced during the Early Gardar Period but the latter is considerably older (1580 m.y.). Both have been affected by the Grenville metamorphism. Rare earth element data for the Tugtutoq younger giant dyke complex of the Gardar Province support previous suggestions that anorthosite inclusions found in the gabbro dykes represent early fractionates disrupted and carried upward by the gabbro magmas. Rare earth and other evidence suggests that the anorthosites may be related to the development of peralkaline magmas at Ilimaussaq.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:641718 |
| Date | January 1976 |
| Creators | Blaxland, Alan B. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14117 |
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