Granitoid rocks and terrane characterization: An example from the northern Appalachian Orogen

Granitoid rocks in the Aspy, Bras d'Or, and Mira terranes of Cape Breton Island in the northern Appalachian Orogen display contrasts in age and petrological characteristics that reflect differences in source rocks and tectonic events in these three terranes. The Aspy Terrane is characterized by a protracted Silurian and Devonian plutonic history, during which granitoid rocks were generated sequentially in volcanic‐arc, post‐arc, collisional, and extensional tectonic settings. In contrast, the Bras d'or and Mira terranes are characterized by Late Precambrian calc‐alkalic I‐type granitoid suites, and only minor Devonian plutonism. Late Precambrian suites in the Bras d'Or Terrane (age ca. 565–555 Ma) are significantly younger than those in the Mira Terrane (age ca. 620 Ma), and the two suites are interpreted to have formed in separate volcanic arcs.