Geochemistry of the Annidale Group: implications for the tectonic setting of Lower Ordovician volcanism in southwestern New Brunswick

Authors

  • M. J. MacLeod Geological Surveys Branch, Department of Natural Resources and Energy, Sussex, New Brunswick
  • J. A. Winchester Department of Geology, University of Keele, Keele, Staffordshire, England
  • A. A. Ruitenberg Geological Surveys Branch, Department of Natural Resources and Energy, Sussex, New Brunswick

DOI:

https://doi.org/10.4138/2122

Abstract

Chemical analyses from volcanic rocks in the Lower Ordovician Annidale Group in southern New Brunswick indicate that it contains two main suites. The volumetrically more abundant suite is bimodal, and consists of within-plate tholeiitic basalt and myolite. The other suite contains rocks that exhibit features indicative of oceanic or possibly subduction-related magmatism. The chemistry of the former suite is consistent with the current interpretation that Ordovician volcanism in southwestern New Brunswick occurred in a back-arc basin. The latter suite, situated near the highly-sheared southeastern margin of the Annidale Group, apparently contains remnants of a different magmatic series near the suture zone between the Gander Zone and the surface expression of the Avalon Zone to the southeast. RÉSUMÉ Les analyses chimiques des roches volcaniques du Groupe d'Annidale, de l'Ordovicien inférieur, dans le sud du Nouvcau-Brunswick indique que celui-ci comprend deux suites principales. La suite la plus abondante en termes de volume est bimodale et comprend des basaltes tholéiitiqucs intraplaques et des rhyolites. L'autre suite contient des roches qui montrent des caractéristiques indiquant un magmatisme océanique ou possiblement relic; a la subduction. La chimie de la première suite est en accord avec l'interprétation prévalant actuellement voulant que le volcanisme ordovicien du sud du Nouveau-Brunswick ait eu lieu dans un bassin d'arrière-arc. La seconde suitée, située près de la bordure sud-est, fortement cisaillée, du Groupe d'Annidale, contient apparemment des reliques d'une séine magmatique différente près de la zone de suture entre la zone de Gander et Pexpression en surface de la zone d'Avalon vers le sud-est. [Traduit par la rédaction]

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Published

1994-07-01

How to Cite

MacLeod, M. J., Winchester, J. A., & Ruitenberg, A. A. (1994). Geochemistry of the Annidale Group: implications for the tectonic setting of Lower Ordovician volcanism in southwestern New Brunswick. Atlantic Geoscience, 30(2). https://doi.org/10.4138/2122

Issue

Vol. 30 No. 2 (1994)

Section

Articles

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