Geochemistry of Silurian-Devonian alkaline basalt suites from the Gaspé Peninsula, Quebec Appalachians
DOI:
https://doi.org/10.4138/1577Abstract
Products of Late Silurian and Early Devonian volcanism in the Northern Appalachians are well exposed in the Chaleurs Bay area of the Gaspé Peninsula. The volcanic association Is dominated by plagioclase basalts and andesltes, and includes pyroclastic flows of dacltic and rhyolitic composition. Major and trace-element chemical analyzes of 174 rocks show that the volcanic association derives from alkaline and high-alumina basalt magmas. The basalts are usually olivine normative and high in A12O3, TiO2, P2O5 and in incompatible elements such as Y and Zr. They follow the course of a calc-alkaline differentiation trend. This volcanism is interpreted to have been related genetically to a regime of tectonic compression, and controlled structurally by fault zones. The Quaternary volcanism associated with the major transcurrent fault zones of northern Anatolia and Iran within the Alpine Orogen provides a modern analog to the Silurian-Devonian volcanism of the Gaspé Peninsula and Newfoundland. RÉSUMÉ Les produits du volcanisme silurien et dévonien des Appal aches du Nord sont bien exposés dans la région de la Baie des Chaleurs de la péninsule gaspéslenne. L'association volcanique comprend sur-tout des basaltes plagioclasiques et des andesltes, tout en incluant une quantite plus faible de coulées pyroclastlques de composition dacitique et rhyolitique. Les analyses chimiques des éléments majeurs et traces de 174 roches indiquent que l'association volcanique dérive de magmas de type basatte alcalin et basalte alumineux. Les basaltes ont fréquemment de l'olivine normative, et ils sont riches en A12O3, TiO2, P2O5, ainsi qu'en éléments incompatibles tels que Y et Zr. Ils suivent une tendance de différenciatlon de type calco-alcaline. Ce volcanisme est interprète comme étant génétiquement lie à un régime tectonique de compression, et sa localisation est controlée structuralement par des zones de failles. Le volcanisme qua-ternaire associé aux grandes failles de décrochement du nord de l'Anatolie et de L’iran, à l'intérieur de L’orogène alpln, est consideré comme un analogue moderne du volcanisme siluro-dévonien de la péninsule de Gaspé et de l'ile de Terre Neuve. [Traduit par le journal]Downloads
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