North America’s Midcontinent Rift magma volume: A coincidental rendezvous of a plume with a rift

The Midcontinent Rift of North America is a ca. 1.1 Ga, 3000-km-long failed rift that nearly split the Precambrian continent of Laurentia. Unlike most continental rifts, which are filled with a mixture of volcanic rocks and sediments, the Midcontinent Rift contains a large volume of flood basalts that were emplaced during both syn and post-rift stages. Consequently, the Midcontinent Rift, which comprises the Keweenaw large igneous province, is the most significant positive anomaly on gravity maps of central North America. We investigated the mantle conditions required to produce this large volume of flood basalt and the observed two main stages of emplacement. To explore whether these magma volumes required a plume or, instead, could have resulted from the increased ambient mantle temperatures expected for the Neoproterozoic, we used a geodynamic model for a range of ambient mantle and plume temperatures under different scenarios of lithospheric extension.