The origin of mafic-ultramafic bodies within the northern Dashwoods Subzone, Newfoundland Appalachians

Authors

  • C. Johan Lissenberg Department of Earth Sciences, University of Ottawa, and Ottawa-Carleton Geoscience Centre, 140 Louis Pasteur, Ottawa, ON K1N 6N5, Canada. * Corresponding author; Current address: Department of Geology and Geophysics, Woods Hole Oceanographic Institute, 36
  • Vicki J. McNicoll Geological Survey of Canada, NRCan, 601 Booth Street, Ottawa, ON K1A 0E8, Canada.
  • Cess R. van Staal Department of Earth Sciences, University of Ottawa, and Ottawa-Carleton Geoscience Centre, 140 Louis Pasteur, Ottawa, ON K1N 6N5, Canada.; Geological Survey of Canada, NRCan, 601 Booth Street, Ottawa, ON K1A 0E8, Canada.

DOI:

https://doi.org/10.4138/2152

Abstract

Mafic-ultramafic bodies of possible ophiolitic origin are widespread within the northern part of the Dashwoods Subzone of the Newfoundland Appalachians. The bodies fall into two types; the first consists of relatively undeformed, fresh, layered gabbroic bodies, which contrasts with the second that consists of metamorphosed ultramafic lithologies. Two of the largest gabbroic bodies yielded U-Pb zircon ages of 432.4±1.0 and 429.9±1.2 Ma. Their Silurian age refutes an ophiolitic origin, and, along with their hydrous nature and fresh character, indicates that they formed in the widespread Early Silurian igneous event that affected both the Dashwoods and Notre Dame subzones. Our new data further substantiate the bimodal character of the Silurian event. The ultramafic bodies are inferred to be of ophiolitic origin. Those that occur in the Dashwoods subzone are interpreted to be related to the Lushs Bight oceanic tract, whereas those in the Lloyds River Fault Zone are correlated with the Annieopsquotch ophiolite belt. RÉSUMÉ Des masses mafiques-ultramafiques d’origine possiblement ophiolitique sont répandues à l’intérieur de la partie septentrionale de la sous-zone de Dashwoods des Appalaches à Terre-Neuve. Les masses s’insèrent dans deux catégories: la première est constituée de masses gabbroïques stratifiées, récentes, relativement peu déformées, qui tranchent avec la seconde, constituée de lithologies ultramafiques métamorphisées. Deux des masses gabbroïques les plus vastes ont affiché des âges de 432,4 ±1,0 et de 429,9 ±1,2 Ma par datation U-Pb sur zircon. Leur âge silurien réfute une origine ophiolitique et, de pair avec leur nature aqueuse et leur caractère récent, signale qu’elles se sont formées au cours du processus igné étendu du Silurien précoce ayant affecté les sous-zones de Dashwoods et de Notre Dame. Nos nouvelles données attestent davantage le caractère bimodal de l’événement silurien. On suppose que les masses ultramafiques sont d’origine ophiolitique. Les masses présentes dans la sous-zone de Dashwoods sont interprétées comme des unités apparentées à la parcelle océanique de Lushs Bight tandis que celles se trouvant dans la zone de la faille de la rivière Lloyds ont été corrélées avec la ceinture ophiolitique d’Annieopsquotch. [Traduit par la rédaction]

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Published

2006-04-01

How to Cite

Lissenberg, C. J., McNicoll, V. J., & van Staal, C. R. (2006). The origin of mafic-ultramafic bodies within the northern Dashwoods Subzone, Newfoundland Appalachians. Atlantic Geoscience, 42(1). https://doi.org/10.4138/2152

Issue

Vol. 42 No. 1 (2006)

Section

Articles

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