Abstracts
Abstract
The late Proterozoic Folly River Formation of the Cobequid Highlands, Nova Scotia, is a volcano-sedimentary sequence within the Avalon Terrane. The succession consists of interlayered mafic volcanic rocks and thinly laminated volcanogenic turbidites and is associated with abundant mafic dykes that are inferred to have fed the volcanic eruptions. The formation occurs exclusively between the Rockland Brook and Cobequid faults. The basalts and dykes are Fe- and Ti-rich, differentiated, within-plate continental tholeiites. Their emplacement is attributed to limited continental rifting. The Folly River Formation is similar in lithology, geochemistry and stratigraphy to the Clydesdale Formation in the Antigonish Highlands and is probably pcnecontemporaneous with arc-related volcanic sequences in both the Cobequid and Antigonish highlands. Hence it is concluded that the Folly River Formation formed in a rifting environment within a volcanic arc.
RESUME
La Formation tardiprot^rozoique de Folly River (Monis Cobequid, Nouvelle-Ecosse) est une seiie volcano-s&limentaire au sein de la Laniere d'Avalon. La succession consiste en un interlitage de volcanites mafiques et de turbidites volcanogenes finement laminees. Lui sont associes d'abondants dykes mafiques qui auraient nouiri les Eruptions volcaniques. La formation ne se rencontre qu'entre les failles de Rockland Brook et de Cobequid. Les basaltes et les dykes sont des tholeiites intraplaques continentales, differenciees et riches en Fe ainsi qu'en Ti. On attribue leur emplacement a l'ouverture restreinte d'un rift continental. La Formation de Folly River ressemble, par sa litnologie, sa geochimie et sa stratigraphie, a la Formation de Clydesdale dans les Monts Antigonish. Elle est probablement penecontemporaine des series volcaniques relives aux arcs dcs monts Cobequid et Antigonish. On conclut done que la Formation de Folly River s'&ablit en regime d'ouverture a rint&ieur d'un arc volcanique.
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