Radiometric Ages of Granitic Rocks, Southwestern Nova Scotia

Abstract

Granitic rocks comprising the eastern half of the main batholith of southwestern Nova Scotia have been studied. The granitic rocks intrude Lower Paleozoic metasediments of the Meguma Group. Field work, the chemistry and petrology of the granitic rocks, and Rb–Sr whole-rock isochron dates indicate that there were at least two episodes of granite emplacement, the earlier about 415 m.y. ago and the later about 350 m.y. ago. Samples from a much smaller pluton some 65 mi (104 km) away from the study area were also dated and are correlated with rocks in the main batholith.

Chronology of tectonothermal activity in the western Avalon Zone of the Newfoundland Appalachians

“…Therefore, the whole-rock ages are interpreted to closely date the widespread regional metamorphism and concomitant deformation recorded in the western Avalon Zone. The whole-rock phyllite ages are generally similar to those defined for the Devonian (Acadian) metamorphism, which affected many northern and maritime Appalachian lithotectonic terranes (e.g., Spooner and Fairbairn I 1970;Naylor 197 1;Cormier and Smith 1973;Pajari et I al. 1974;Lyons and Livingston 1977;Dallmeyer and VanBreemen 198 1).…”

A radiometric age of deformed granitic rocks in north-central New Brunswick

“…No specimens were included from the largest pluton because of its low Rb-Sr ratio. The analytical procedure for the determinations was essentially the same as that detailed in Cormier and Smith (1973). The age, initial ratio, and error at the 95% confidence level were calculated using the methods described by York (1966).…”

Zircon isotopic age from the Union ultramafic complex, Maine

“…Recent studies by a number of investigators in the northem Appalachians are defining a minimum time of peak Acadian metamorphism at 385-400 Ma (Dallmeyer 1979;Gaudette et al 1975, manuscript in preparation;Pajari et al 1974;Cormier and Smith 1973;Naylor 1971;Lyons and Livingston 1977;Spooner and Fairbairn 1970). These data and the age of the Union complex of this report strongly suggest that the Acadian event, from final closure of Iapetus and collision of the Avalonian microcontinent through the peak of Acadian deformation, occurred in a period of less than 20 Ma in this part of the northem Appalachian system.…”