NEW CONSTRAINTS ON NORTH AMERICAN KIMBERLITE EMPLACEMENT FROM KINEMATIC AND GEOPHYSICAL MODELS

Kimberlites are relatively rare ultramafic igneous rocks that are most commonly associated with emplacement on Archean cratons. However, they are distributed more widely across the North American continent, including numerous occurrences within younger Proterozoic terranes. Several hypotheses have seen proposed to explain this widespread distribution across North America: entrainment through mantle plumes, fluids deriving from subducting slabs, and edge-driven convection. In this study we provide new constraints on North American kimberlite emplacement by backtracking the locus of their emplacement over time by considering several recent kinematic models. We use the GPlates software to make this reconstruction. The results show that kimberlites do not have a common “fixed” mantle source, such as plumes or large low shear velocity provinces, as suggested in recent studies. Lithosphere-asthenosphere models, as well as seismic tomography models, indicate that the edge-driven convection model is most consistent with the distribution of kimberlites emplaced over the North America continent. Indeed, most of these kimberlites are located within the region of transition between thick (> 220 km) and thin (< 180 km) lithosphere.