New insights into the Appalachian Orogen from geology and geochronology along the Cape Ray fault zone, southwest Newfoundland

摘要: Reverse-oblique overthrusting of high-grade Port aux Basques Gneiss over the lower-grade, supracrustal Windsor Point Group along Cape Ray fault zone occurred during late Silurian to early Devonian time and is attributed major oblique collision between Gondwanan Laurentian continental blocks. New U-Pb zircon, 40 Ar/ 39 Ar, K/Ar data limit timing this orogenic event. The megacrystic granitic phase Igneous Complex tonalite have been dated at 488 ± 3 Ma 469 2 Ma, respectively. A black rhyolite from yielded an Ordovician age (453 +5/−4 Ma). pretectonic gabbro sill within Group, 424 +4/−3 cut by Windowglass Hill granite Ma. Synkinematic hornblende biotite Grand Bay mylonites Ar ages 407 4 403 respectively, which indicative a Silurian–early for amphibolite grade deformation. These are compatible with previously determined 415 monazite age, interpreted as peak metamorphism in Gneiss, suggests rapid exhumation. east-west flexure represents tear accommodating differential shortening correlative system central Newfoundland. Mid-Devonian granites (386 3, 384 Ma) intervene thrusting events younger sinistral transcurrent movement. This deformation magmatic history can be correlated throughout northern Appalachians other boundaries.