| Summary: | Although small in volume, Cambrian volcanic rocks associated with Acado-Baltlc sedimentary rocks In Newfoundland, New Brunswick, and Nova Scotia, Norway and Poland display characteristics indicating formation in a tensional tectonic setting. They generally form bimodal (basalt-rhyolite) suites. Mafic rocks are of both alkaline and tholeiitic affinities but all have withln-plate major element and trace element characteristics. The small volume and low frequency of eruption suggests that in most cases the volcanic rocks resulted from only small amounts of lithospherlc extension, and that rupturing and separation of plates may not have taken place. Volcanism over the Acado-Baltic province appears to have been less common in the Late Cambrian than in the Early and Middle Cambrian. This suggests that tension persisted throughout the Early and Middle Cambrian, but waned in the Upper Cambrian, possibly in direct or indirect response to processes which led to closing of the lapetus Ocean. RÉSUMÉ Malgré un volume restraint, les volcanites cambriennes associées aux roches sédimentaires acado-baltiques à Terre-Neuve, au Nouveau-Brunswick ainsi qu'en Nouvelle-Écosse, Norvège et Pologne montrent des caractéristiques qui suggèrent leur formation en régime tectonlque de tension. Elles foment généralement des suites bimodales (basalte-rhyolite). Les roches mafiques ont des affinites tant alcalines que tholèiitiques bien qu’elles révèlent un caractére intraplaque au plan des éléments majeurs et en traces. Du volume restreint et de la faible fréquence éruptive, on retire l’impression que, pour la plupart, ces volcanites ne reultent que d'une extension lithospherique de faible valeur et qu'aucune rupture ou séparation des plaques n'a eu lieu. La province acado-baltique aurait connu un volcanisme mollis prononce à l'eo-Cambrlen ...
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