This study investigates the tectono-metamorphic history and exhumation mechanisms of the mid-crustal Mékinac-Taureau domain of the Mauricie area, central Grenville Province. Macro- and micro-structural analyses reveal the top-down-to-the-ESE sense of shear on the eastern Taureau shear zone, a major extensional structure that exhumed the mid-crustal Mékinac-Taureau domain and juxtaposed it against the lower grade rocks of the Shawinigan domain. Peak metamorphism in the Mékinac-Taureau domain, inferred to be the result of northwestward thrusting and regional crustal thickening, took place under P–T conditions of 1000–1100 MPa and 820–880 °C prior to 1082 ± 20 Ma. Retrograde conditions varying from 775 to 675 °C and from 800 to 650 MPa were registered in its upper structural levels prior to and/or during shearing along the eastern Taureau shear zone that was active at 1064 ± 15 Ma. The Shawinigan domain records P–T conditions ranging from 850 to 625 MPa and from 775 to 700 °C, P–T values that are similar to or slightly lower than those for retrogressed samples from the upper structural levels of the Mékinac-Taureau domain, but clearly lower than the peak metamorphism values of the latter domain. Finally, the area cooled below 550–600 °C at ∼1000–1030 Ma and below 450 °C at ∼900–970 Ma on the basis of 40Ar/39Ar geochronology on amphibole and biotite. Structural and metamorphic characteristics of the Mauricie area are similar to those expected from a metamorphic core complex formed during post-convergence orogenic collapse in a gravity-driven fixed-boundary mode. The Mékinac-Taureau and Shawinigan domains were thus probably exhumed by a similar process, which supports the orogenic collapse model recently proposed to explain the exhumation of mid-crustal metamorphic core complexes in the Grenville Province.
This is the author’s version of a work that was accepted for publication in Precambrian Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Precambrian Research, 257 (Feb 2015) doi: 10.1016/j.precamres.2014.11.012
Soucy La Roche, Renaud; Gervais, Félix; Tremblay, Alain; Crowley, James L.; and Ruffet, Gilles. (2015). "Tectono-Metamorphic History of the Eastern Taureau Shear Zone, Mauricie Area, Québec: Implications for the Exhumation of the Mid-Crust in the Grenville Province". Precambrian Research, 257, 22-46. http://dx.doi.org/10.1016/j.precamres.2014.11.012