40Ar/39Ar age of shear zones in the southwest Meguma Zone between Yarmouth and Meteghan, Nova Scotia

1997/06/01 by Nicholas Culshaw, Peter Reynolds, P. H. Reynolds · 46 citations
Earth and Planetary Sciences · #Closure temperature #Facies #Geochemistry #Geological and Geochemical Analysis #Geological formations and processes #Geology #Geology and Paleoclimatology Research #Geomorphology #Greenschist #Metamorphic facies #Metamorphism #Mineralogy #Muscovite #Mylonite #Nova scotia #Paleontology #Petrology #Quartz #Seismology #Shear (geology) #Shear zone #Tectonics

paper · doi:10.1139/e17-069

published in Canadian Journal of Earth Sciences 34(6), 848-853 (NRC Research Press)

openalex publication_date 1997/06/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/25

Abstract

The Cape St. Marys, Cranberry Point, and Chebogue Point shear zones lie within a zone of D2 deformation that overprinted D1 fabrics and reactivated F1 folds between the shear zones. D2 was accompanied by greenschist-facies metamorphism that variably overprinted earlier metamorphism of varying grade. A collection of single muscovite grains from pressure shadows defining L2 in a sample from the Cape St. Marys shear zone yields an average apparent age of 316 ± 5 Ma. The age obtained for these grains from an isotope correlation diagram is 320 ± 5 Ma. Ages for muscovite separates for two samples from the Cranberry Point shear zone are 325 ± 4 and 319 ± 4 Ma. An amphibolite from this zone yields a discordant spectrum interpreted to reflect the combined effects of Acadian metamorphism and excess argon. The muscovite ages approximate the time of syntectonic deformation because muscovite closure temperatures approximate the temperature of metamorphism during D2. Thus, together with published data from the Chebogue Point shear zone, our data indicate a Mid-Carboniferous age, ca. 320 Ma, for D2 within this system of three shear zones and reactivated folds.

Citations

• Late Paleozoic collision, delamination, short-lived magmatism, and rapid denudation in the Meguma Terrane (Nova Scotia, Canada): constraints from 40Ar/39Ar isotopic data

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