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TitreTorngat ultramafic lamprophyres and their relation to the North Atlantic Alkaline Province
AuteurTappe, S; Jenner, G A; Foley, S F; Heaman, L; Besserer, D; Kjarsgaard, B A; Ryan, B
SourceSelected papers from the Eighth International Kimberlite Conference, volume 1: the C. Roger Clement volume; par Mitchell, R H (éd.); Grutter, H S (éd.); Heaman, L M (éd.); Scott Smith, B H (éd.); Lithos vol. 76, issue 1-4, 2004 p. 491-518,
Séries alt.Commission géologique du Canada, Contributions aux publications extérieures 2003317
ÉditeurElsevier BV
RéunionEighth International Kimberlite Conference; Victoria, BC; CA; juin 22-27, 2003
Documentpublication en série
Mediapapier; en ligne; numérique
Référence reliéeCette publication est reliée Tappe, S; Foley, S; Jenner, G; Ryan, B; Besserer, D; Kjarsgaard, B; (2003). Ultramafic lamprophyre dyke swarm, Torngat Mountains, Quebec and Labrador: mineralogy and geochemistry, 8th International Kimberlite Conference: extended abstract
Formatshtml; pdf (Adobe Acrobat Reader)
ProvinceRégion extracotière de l'est
SNRC13; 14; 15; 16; 23; 24; 25; 26A; 26B; 26C; 26D; 26E; 26F; 26G; 26H; 33; 34; 35; 36A; 36B; 36C; 36D; 36E; 36F; 36G; 36H
Lat/Long OENS -80.0000 -36.0000 66.0000 52.0000
Sujetsroches ultramafiques; filons rocheux; olivine; phlogopite; carbonatites; lamprophyres; carbonatites; décrochement horizontal; crevasses; tectonique de plaques; diamant; datation au uranium-plomb; géologie économique; géochimie; géochronologie; pétrologie ignée et métamorphique; tectonique
Illustrationslocation maps; tables; geochemical plots; photomicrographs; graphs
ProgrammeCRSNG Conseil de recherches en sciences naturelles et en génie du Canada
Résumé(disponible en anglais seulement)
Geological mapping and diamond exploration in northern Quebec and Labrador has revealed an undeformed ultramafic dyke swarm in the northern Torngat Mountains. The dyke rocks are dominated by an olivine-phlogopite mineralogy and contain varying amounts of primary carbonate. Their mineralogy, mineral compositional trends and the presence of typomorphic minerals (e.g. kimzeyitic garnet), indicate that these dykes comprise an ultramafic lamprophyre suite grading into carbonatite. Recognized rock varieties are aillikite, mela-aillikite and subordinate carbonatite. Carbonatite and aillikite have in common high carbonate content and a lack of clinopyroxene. In contrast, mela-aillikites are richer in mafic silicate minerals, in particular clinopyroxene and amphibole, and contain only small amounts of primary carbonate. The modal mineralogy and textures of the dyke varieties are gradational, indicating that they represent end-members in a compositional continuum.

The Torngat ultramafic lamprophyres are characterized by high but variable MgO (10-25 wt.%), CaO (5-20 wt.%), TiO2 (3-10 wt.%) and K2O (1-4 wt.%), but low SiO2 (22-37 wt.%) and Al2O3 (2-6 wt.%). Higher SiO2, Al2O3, Na2O and lower CO2 content distinguish the mela-aillikites from the aillikites. Whereas the bulk rock major and trace element concentrations of the aillikites and mela-aillikites overlap, there is no fractional crystallization relation between them. The major and trace element characteristics imply related parental magmas, with minor olivine and Cr-spinel fractionation accounting for intra-group variation.

The Torngat ultramafic lamprophyres have a Neoproterozoic age and are spatially and compositionally closely related with the Neoproterozoic ultramafic lamprophyres from central West Greenland. Ultramafic potassic-to-carbonatitic magmatism occurred in both eastern Laurentia and western Baltica during the Late Neoproterozoic. It can be inferred from the emplacement ages of the alkaline complexes and timing of Late Proterozoic processes in the North Atlantic region that this volatile-rich, deep-seated igneous activity was a distal effect of the breakup of Rodinia. This occurred during and/or after the rift-to-drift transition that led to the opening of the Iapetus Ocean.