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The Paleogeography of Laurentia in Its Early Years: New Constraints From the Paleoproterozoic East-Central Minnesota Batholith

  • Author(s): Swanson-Hysell, NL;
  • Avery, MS;
  • Zhang, Y;
  • Hodgin, EB;
  • Sherwood, RJ;
  • Apen, FE;
  • Boerboom, TJ;
  • Keller, CB;
  • Cottle, JM
  • et al.
Abstract

The ca. 1.83 Ga Trans-Hudson orogeny resulted from collision of an upper plate consisting of the Hearne, Rae, and Slave provinces with a lower plate consisting of the Superior province. While the geologic record of ca. 1.83 Ga peak metamorphism within the orogen suggests that these provinces were a single amalgamated craton from this time onward, a lack of paleomagnetic poles from the Superior province following Trans-Hudson orogenesis has made this coherency difficult to test. We develop a high-quality paleomagnetic pole for northeast-trending diabase dikes of the post-Penokean orogen East-Central Minnesota Batholith (pole longitude: 265.8°; pole latitude: 20.4°; A95: 4.5°; K: 45.6 N: 23) whose age we constrain to be 1,779.1 ± 2.3 Ma (95% CI) with new U-Pb dates. Demagnetization and low-temperature magnetometry experiments establish dike remanence be held by low-Ti titanomagnetite. Thermochronology data constrain the intrusions to have cooled below magnetite blocking temperatures upon initial emplacement with a mild subsequent thermal history within the stable craton. The similarity of this new Superior province pole with poles from the Slave and Rae provinces establishes the coherency of Laurentia following Trans-Hudson orogenesis. This consistency supports interpretations that older discrepant 2.22–1.87 Ga pole positions between the provinces are the result of differential motion through mobile-lid plate tectonics. The new pole supports the northern Europe and North America connection between the Laurentia and Fennoscandia cratons. The pole can be used to jointly reconstruct these cratons ca. 1,780 Ma strengthening the paleogeographic position of these major constituents of the hypothesized late Paleoproterozoic supercontinent Nuna.

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