New insights on the 1.7–1.0 Ga crustal evolution of the central Grenville Province from the Manicouagan – Baie Comeau transect

Integrated field relationships and U–Pb geochronology of rocks exposed along the southern part of the Manicouagan reservoir (central Grenville Province, Quebec) provide insights into protolith formation and thermal events that range in age from ca. 1.7 to 0.9 Ga and share common features with the rest of the Grenville Province and beyond.From presently lower to higher structural levels, main findings include the recognition of: (a) ca. 1.70–1.75 Ga granitic magmatism and metamorphism in the southern part of the parautochthonous Gagnon terrane, correlative in age with late stages of magmatism in the Makkovik Orogen to the northeast; (b) a ca. 1.69 gabbro-anorthosite suite (Island domain) which is inferred to represent the southwesternmost exposure of Labradorian crust in the central Grenville Province; (c) a 1.4 Ga volcaniclastic sequence and associated plutonic rocks (Canyon domain), which based on lithological association and age, is inferred to represent the NNE extension of the Montauban island arc; and (d) a ca. 1.2 Ga bimodal felsic-mafic volcanic to intermediate volcaniclastic sequence (Banded complex), inferred to have originated in an intra-continental rift system, contemporaneously with the Composite Arc Belt (southwestern Grenville Province) and with widespread extensional magmatism elsewhere in the Canadian Shield. In addition, 1.3 Ga granitoid plutons are documented to intrude Labradorian units at the NW boundary of Canyon domain. The significance of these plutons is ambiguous, as they may represent either stitching plutons, marking the accretion of the 1.4 Ga Canyon domain to the Laurentian margin, or the first stage in the development of the ca. 1.2 Ga continental rift system.The hinterland units (Island domain, Canyon domain and Banded complex) were metamorphosed under medium-pressure granulite facies conditions during the culmination of the Grenvillian orogeny between 1.08 and 1.04 Ga. This metamorphism was accompanied by ca. 1.07 Ga A-type granitic magmatism in Canyon domain. In addition, locally abundant ca. 0.98 Ga late-tectonic felsic pegmatite and ultrapotassic dykes occur in Canyon domain. This event is coeval with titanite ages documented in a wide range of units. The data on the Grenvillian evolution suggest mantle-derived magmatism and associated metamorphism in the hinterland during both the culmination and the waning stages of the Grenvillian orogeny.