Tectonic setting of the Devonian Park Spur pluton, central Cape Breton Highlands, Nova Scotia, Canada.

Field, petrological, dating, and structural studies in the central Cape Breton Highlands have led to new understanding of the complex history related to convergence between the Aspy and Bras d'Or terranes along the Eastern Highlands shear zone in the late Devonian. The Park Spur pluton (PSP) was emplaced in the Aspy terrane in the early Late Devonian (ca. 375 Ma, U-Pb zircon). Its age combined with S-type petrological characteristics and abundant pegmatite and aplite show that it is co-magmatic with the Black Brook Granitic Suite and satellite plutons that characterize the northern Aspy terrane. These widespread plutons may have formed by crustal melting caused by subducted slab failure. On its northern margin the PSP intruded high-grade Ordovician-Silurian metamorphic rocks of the Cape North Group at mesozonal depth (>10 km), consistent with its petrological features and abundant pegmatite and aplite dykes. On its southern margin the PSP was synchronously deformed in the east-west-trending Park Spur Road shear zone and juxtaposed in a southerly direction over the low-grade metasedimentary and metavolcanic rocks of the Ordovician-Silurian Calumruadh Brook Formation (CBF). Ongoing dextral transpression between Aspy and Bras d'Or terranes reactivated the north-south-trending Central Highlands shear zone, on which the higher- grade Middle River metamorphic suite and Silurian Taylors Barren pluton to the west were transported upward relative to the adjacent CBF and PSP. By about 365 Ma, convergence had mainly ended, as evidenced by shallow emplacement of the ca. 363 Ma Margaree pluton in an extensional setting. [ABSTRACT FROM AUTHOR]