TECTONIC EVOLUTION OF LAURENTIA IN THE LATE MESOPROTEROZOIC AND ITS ROLE WITHIN THE SUPERCONTINENT RODINIA

The late Mesoproterozoic to early Neoproterozoic was a critical interval in the tectonic evolution of Laurentia. The interval spans the rise and fall of the Grenville orogen at the center of the supercontinent Rodinia. Prior to the Grenvillian orogeny, a major intracontinental rift co-located with a large igneous province formed in Laurentia's interior leading to extension within the Archean Superior province and adjacent Paleoproterozoic provinces to the south. The large igneous province associated with this Midcontinent Rift led to mafic volcanism that spanned from one end of the continent to the other over a distance of >3,000 km with pulsed emplacement of voluminous lavas and intrusions over a 25 million year interval. The thick successions of well-preserved volcanics in the Midcontinent Rift have enabled the development of a precisely-calibrated record of paleomagnetic poles that reveal extraordinarily rapid plate motion leading up to collisional Grenvillian orogenesis. The eastern margin of Laurentia that had experienced intervals of accretionary orogenesis over the preceding 600 million years was the leading edge of Laurentia as it sped towards the equator at rates exceeding 30 cm/year. The protracted Grenvillian orogeny could have been sustained by the strong convective cell established through the subduction that moved Laurentia southward. This collisional orogenesis terminated Midcontinent Rift development, eventually leading to rift inversion, and established the supercontinent Rodinia.