U-Pb age constraints for the lithotectonic evolution of the Grenville province along the Mauricie transect, Quebec

New U-Pb zircon and monazite ages on 12 samples from the Mauricie transect in Quebec provide constraints on the lithologic and tectonic evolution of the south-central Grenville Province. From lowest to highest structural levels, the Mekinac, Shawinigan, and Portneuf - St. Maurice domains are identified on the basis of protolith age, tectonic overprint, and plutonism. The structurally highest Portneuf - St. Maurice domain consists of remnants of an island are (Montauban Group) that was deformed and metamorphosed before and during the intrusion of continental are plutons: (La Bostonnais complex). A tonalitic orthogneiss yeilding a 1371(-32)(+51) Ma zircon age suggests that most of the structurally underlying Mekinac and Shawinigan domains consist of orthogneisses that may be high-grade equivalents of the La Bostonnais complex. A voluminous metasedimentary unit occurring in the Shawinigan domain (St. Boniface unit) was deposited between ca. 1.18 and 1.09 Ga, precluding any correlation with the ca. 1.45 Ga Montauban Group. Two suites of anorthosite-mangerite-charnockite-granite (AMCG) plutonic rocks are identified on the basis of field relationships and isotopic age. A megacrystic granite belonging to the ''older'' AMCG suite yielded a 1153(-1)(+2) Ma zircon age. Three plutons from the ''younger'' suite yielded ages of 1076(-3)(+4), 1059 +/- 2, and 1056 +/- 2 Ma. The Mekinac and Shawinigan domains, excluding the younger AMCG plutons, were penetratively deformed at granulite to uppermost amphibolite facies during west-northwest-directed thrusting between 1.15 and 1.09 Ga. At ca. 1.09 Ga, a transition from contraction to oblique extension resulted in the juxtaposition of the ''cold'' Portneuf - St. Maurice domain with the ''hot'' Shawinigan domain, along the Tawachiche shear zone. Oblique extension may have been active from ca. 1.09 to 1.04 Ga and was contemporaneous with emplacement of the younger AMCG suite.