The location of the Allochthon Boundary Thrust and the Archean–Proterozoic suture in the Mattawa area of the Grenville Province: Nd isotope evidence

Over 100 Nd isotope analyses are used to map the crustal formation ages of Grenville orthogneisses in a 10 000 km2 area near Mattawa on the Ontario–Quebec border. Lithotectonic terranes with mapped outcrops of eclogite or coronitic metagabbro have Nd model ages less than 1.8 Ga, and are interpreted as fragments of the allochthonous polycyclic belt. However, large areas of orthogneiss to the north of Mattawa have model ages of 1.9–2.9 Ga, …