Remnants of Early Mesozoic basalt of the Central Atlantic Magmatic Province in Cape Breton Island, Nova Scotia, Canada

Abstract

Amygdaloidal basaltic flows of the Ashfield Formation were encountered in two drill holes in areas of positive aeromagnetic anomalies in the Carboniferous River Denys Basin in southwestern Cape Breton Island, Nova Scotia. One sample of medium-grained basalt yielded a plateau age of 201.8 ± 2.0 Ma, similar to the U–Pb and 40Ar/39Ar crystallization ages from basaltic flows and dykes in the Newark Supergroup. A second sample of zeolite-bearing basalt yielded a discordant age spectrum and a younger age of ca. 190 Ma, which is interpreted to date a widespread hydrothermal event related to zeolite formation. Whole-rock chemical data show that the Ashfield Formation basalt is low-Ti continental tholeiite, consistent with its within-plate tectonic setting. Chemically, it resembles basaltic flows in the Mesozoic Fundy and Grand Manan basins exposed in southern Nova Scotia and eastern New Brunswick and elsewhere in Central Atlantic Magmatic Province (CAMP). The age and geochemical data from the Ashfield Formation provide the first evidence for early Mesozoic CAMP volcanism in Cape Breton Island and demonstrate that the event was more widespread in Nova Scotia than previously thought, which has implications for its continuity and extent elsewhere within CAMP.

The development of the eastern Orpheus rift basin, offshore eastern Canada: A case study of the interplay between rift-related faulting and salt deposition and flow

“…1a), CAMP-related igneous rocks include the North Mountain Basalt in the Fundy rift basin (Dostal and Greenough, 1992;Olsen and Et-Touhami, 2008;Cirilli et al, 2009;Jourdan et al, 2009) and the Shelburne (Pe-Piper et al, 1992;Dostal and Durning, 1998;Dunn et al, 1998), Caraquet (Pe-Piper et al, 1992Dostal and Durning, 1998), and Avalon dikes (Pe-Piper et al, 1992). CAMP-related basalts are also present in nearby wells from the region between the Fundy and Orpheus rift basins (White et al, 2017), in the Mohican rift basin on the Scotian Shelf (Weston et al, 2012), and in the Jeanne d'Arc rift basin of the Grand Banks region (Pe-Piper et al, 1992).…”