| Titre | Age and eruptive style of volcanic rocks dredged from the Alpha Ridge, Arctic Ocean |
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| Auteur | Williamson, M -C ;
Kellett, D; Miggins, D; Koppers, A; Carey, R; Oakey, G; Weis,
D; Jocat, W; Massey, E |
| Source | Geophysical Research Abstracts vol. 21, EGU2019-6336, 2019 p. 1 |
| Image |  |
| Année | 2019 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20180358 |
| Éditeur | European Geosciences Union (EGU) |
| Réunion | General Assembly of the European Geosciences Union (EGU 2019); Vienna; AT; avril 7-12, 2019 |
| Document | publication en série |
| Lang. | anglais |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Nunavut; Région extracotière du nord |
| SNRC | 49F; 49G; 59E; 59F; 59G; 59H; 340B; 340C; 560A; 560D |
| Région | Océan Arctique; Alpha Ridge |
| Lat/Long OENS | -180.0000 -60.0000 90.0000 76.0000 |
| Sujets | Crétacé supérieur; géologie du substratum rocheux; lithologie; roches ignées; roches volcaniques; tufs volcaniques; basaltes; cadre tectonique; magmatisme; volcanisme; échantillonnage par drague; analyses
des éléments majeurs; analyses des éléments en trace; datation radiométrique; datation argon-argon; analyses à l'infrarouge; Bassin d'Amerasia ; tectonique; minéralogie; géochimie; géochronologie; Phanérozoïque; Mésozoïque; Crétacé |
| Programme | Délimitation du plateau continental du Canada en vertu de la Convention des Nations Unies sur le droit de la mer (UNCLOS) |
| Diffusé | 2019 03 01 |
| Résumé | (disponible en anglais seulement)
The Alpha-Mendeleev ridge complex is a prominent physiographic and geological feature of the Arctic Amerasia Basin. The Alpha and Mendeleev ridges are,
respectively, the eastern and western components of a continuous seafloor high that is approximately 2000 km long and 200-400 km wide. A surge of interest in the tectonic evolution of Arctic submarine features has led to a wealth of new geophysical
data collected from the Alpha Ridge. Current interpretations of its origin vary but there is compelling evidence that the Alpha Ridge may have formed as an oceanic plateau during the Late Cretaceous. Geological samples are rare but most samples
recovered indicate a genetic link with the High Arctic Large Igneous Province (HALIP).
In August 2016, Canada's Extended Continental Margin-United Nations Convention on the Law of the Sea Program dredged approximately 100 kg of volcanic rocks from
the Alpha Ridge. The large size and pristine state of the samples enabled the first comprehensive study of a single eruptive event in the volcanic record of the Alpha Ridge. The dredge sample is a lapilli tuff containing vitric and basaltic clasts.
Textural evidence and the coexistence of juvenile and cognate clasts suggest a phreatomagmatic eruption. The vitric fragments consist of sideromelane glass with abundant plagioclase microlites. Texturally, these basaltic glass lapilli display a fresh
glassy core surrounded by Fe- and Ti-rich zones and a palagonite rim. Major and trace element analyses of glassy cores indicate remarkably uniform, mildly alkaline basaltic compositions. The plagioclase-bearing glass yielded a 40Ar/39Ar plateau age
of 90.40 ± 0.26 Ma (2-sigma error) which included 89% of 39Ar released. We interpret this result to represent the eruption age of the plagioclase microlites and consequently, of the host basaltic glass lapilli in the tuff. Volatile species analyses
by infrared spectroscopy on the fresh basaltic glass suggests that the melt was effectively degassed to shallow level. Assuming equilibrium degassing, the homogeneous resulting values of H2O(total) in the range 0.1 to 0.19 wt.% (1-sigma error)
indicate subaerial or shallow eruption (surface to 80 m).
The new 40Ar/39Ar age for the sample is consistent with a 40Ar/39Ar age of 89 ± 1 Ma obtained for a sample of tholeiitic basalt dredged from the central part of the Alpha Ridge, and with
the range of ages reported for HALIP igneous rocks exposed onshore in the Canadian Arctic Archipelago (130-80 Ma). Our new data provide evidence for local emergence of the Alpha Ridge in the Late Cretaceous. A comparison of the Alpha Ridge and
Kerguelen Plateau-Broken Ridge Large Igneous Province (LIP) provides new insights on the episodic nature of LIP magmatism and variations in eruptive style through time. |
| Sommaire | (Résumé en langage clair et simple, non publié)
En août 2016, environ 100 kg de roches volcaniques ont été récupérés avec succès de la chaîne Alpha, située dans l`océan Arctique, dans le cadre
du programme continental étendu du Canada (UNCLOS). Les échantillons recueillis par dragage du fond marin sont constitués de tufs de lapilli mis en place lors du mélange explosif de lave et d¿eau à faible profondeur. Nous présentons de nouvelles
données géochronologiques et volcanologiques qui nous permettent de comparer ces résultats avec ceux obtenus sur des roches ignées de la Grande Province Ignée de l`Extrême Arctique (HALIP) et du plateau de Kerguelen. |
| GEOSCAN ID | 313521 |
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