Deformation of the Cape Chignecto pluton, Cobequid Highlands, Nova Scotia: thrusting at the Meguma-Avalon boundary

Abstract

The Early Carboniferous Cape Chignecto pluton, at the western end of the Cobequid Highlands in the Avalon Terrane of Nova Scotia, consists predominantly of two-feldspar biotite granite. Much of the pluton has a flat-lying mylonitic foliation, with a mineral elongation lineation trending between north and west. Quartz is dynamically recrystallized, but feldspars show predominantly brittle deformation. The pluton was probably deformed under greenschist facies conditions, after cooling. C-S fabrics observed in the field, and tails on porphyroclasts seen in thin section, indicate northward overthrusting. The deformation of the pluton is constrained by stratigraphic relationships and isotopic dates to a Namurian or possibly early Westphalian age. Deformation within the pluton is correlated with Namurian uplift of the Cobequid and Caledonia Highlands. It records either transpression resulting from the curvature of the Meguma-Avalon boundary or a major component of convergent movement between the Meguma and Avalon terranes. -from Authors