Timing of eastern North American kimberlite magmatism: continental extension of the Great Meteor hotspot track?

Twenty-nine new high precision U-Pb perovskite ages for kimberlite and other CO2-rich ultrabasic rocks, primarily from five fields or clusters in eastern North America (Rankin Inlet, Attawapiskat, Kirkland Lake, Timiskaming and Finger Lakes), indicate that at least five periods of Mesozoic kimberlite magmatism can be distinguished. These new data document four periods of kimberlite magmatism previously unrecognized in eastern North America: at 196, 180-176, 148-146 and 142-134 Ma. In addition, the detailed emplacement history of Jurassic kimberlites in the Kirkland Lake field indicates magmatism spanned a period of 13 Myr from 165 to 152 Ma with approximately half of the kimberlites in this field emplaced in less than 2 Myr between 156.9-155.3 Ma. These U-Pb results demonstrate for the first time that there is a NW-SE Triassic to Cretaceous age progression in kimberlite magmatism, which is consistent with the relative plate motions of North America during this interval. This age progression in kimberlite magmatism extends for more than 2000 km from Rankin Inlet through to the Attawapiskat, Kirkland Lake and Timiskaming fields and is interpreted, in part, to be the continental expression of magmatism linked to the Great Meteor mantle plume hotspot track. If correct, then the timing and location of this magmatism provides a more rigid constraint for both the exact position of the hotspot and the relative direction and rate of North American plate motion during the Mesozoic opening of the North Atlantic Ocean. (C) 2000 Elsevier Science B.V. All rights reserved.