ИСТИНА

Mesozoic intraplate magmatic activity in Canada occurs as kimberlite fields and ultramafic lamprophyre (UML) across Nunavut, Ontario, and Quebec, including the Monteregian Hills alkaline province in Quebec. Based on the isotope ages obtained for some of these intrusions, several petrogenetic models explaining their corridor-like spatial distribution have been developed, variously attributing their emplacement to the passage of one or several mantle plumes, effects of edge-driven convection along the Superior craton margin, and influence of Farallon slab subduction. This study aims to test the feasibility of these proposed models using existing plate tectonic reconstructions based on previously published data. A dataset consisting of 50 isotope age determinations and precise locations for kimberlites and UMLs in the Rankin Inlet, Attawapiskat, Kirkland Lake, Lake Timiscaming regions and some individual kimberlite occurrences, as well as for Monteregian Hills intrusions and New England seamounts were compiled from the literature. The GPlates 2.3 software package was used to calculate the North American hotspot tracks of the Azores, Madeira, Canary Islands, Capo Verde, and Great Meteor plumes according to three widely used plate movement reconstructions. The positions of intraplate magmatism occurrences relative to the Superior craton boundary and s-wave velocity anomalies at the depth of 200 km were also considered. Stress field orientations in Moneregian and Timiscaming regions were inferred from plate kinematics at the time of formation of the respective magmatic provinces. Multiple major differences between the hotspot tracks reconstructed from geochronological data and those reconstructed from existing plate movement models were discovered even in the best-fit combinations, e.g. the oldest of Timiscaming structural zone kimberlites are emplaced ~30 Ma after the last plume passage through the area, and Monteregian intrusions are ~25 Ma ‘late’; Timiscaming field is also distant (~700 km) from craton margins or mantle shear-wave velocity anomalies. The results suggest that either significant inaccuracies exist in some of the datasets used for the modeling, or mantle phenomena alone are not sufficient to explain the spatio-temporal distribution of intraplate intrusions in Canada, and structural controls imposed by the crust play a significant role. We suggest that the Mesozoic reactivation of faults in the Ottawa-Bonnechere graben system triggered the emplacement of some of the intraplate intrusions, although the previous passage of the plumes could have primed the subcontinental lithospheric mantle for ultra-alkaline melt generation.