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Tectonomagmatic Evolution of the Midcontinent Rift

Tectonomagmatic Evolution of the Midcontinent Rift. North America (Laurentia) at 1.1 Ga. Continental Rifting- The creation of ocean basins. Mantle Plumes and Flood Basalts. Magmatic Underplating of the Crust A Consequence of Mantle Plume Magmatism. LIPs-Large Igneous Provinces.

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Tectonomagmatic Evolution of the Midcontinent Rift

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  1. Tectonomagmatic Evolution of the Midcontinent Rift

  2. North America (Laurentia) at 1.1 Ga

  3. Continental Rifting- The creation of ocean basins

  4. Mantle Plumes and Flood Basalts

  5. Magmatic Underplating of the Crust A Consequence of Mantle Plume Magmatism LIPs-Large Igneous Provinces

  6. Simple Tectonic Model for the MCR

  7. Evidence of a Starting Mantle Plume • Rapid early rates of volcanism • Large total volume of mafic magmatism (> 20 km volcanic edifice in central axis of rift) • εNd of mafic rocks = 0 to slightly +

  8. Main Igneous Units of the MCR Nipigon Sills Coldwell Complex Logan Sills Osler Group Duluth Complex Michipichoten Island Volcanics Isle Royale Fault Beaver Bay Complex Portage Lake volcanics North Shore Volcanic Gp Mamainse Pt Volcanics Douglas Fault Mellen Complex Powdermill Group Chengwatana volcanics

  9. Geophysical Evidence of Underplating

  10. Lo-P Hi-P Differentiated Basalts of the NSVG Primitive Ol Tholeiite

  11. Geochronology of the MCR Hoaglund (2010)

  12. Proposed Tectonomagmatic Model for the Midcontinent Rift

  13. Why Didn’t the MCR Evolve to an Ocean Basin? - Dissipation of the Plume - Resurgence of Grenville Compression

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