The paleogeography of Laurentia in its early years: new constraints from the Paleoproterozoic East-Central Minnesota batholith

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 should be considered as 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 di cult 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 1779.1 ± 2.3 Ma (95% CI) with new U-Pb dates on the granites. Demagnetization and low-temperature magnetometry experiments establish the remanence of the dikes to be held by low-Ti titanomagnetite. Thermochronology data constrain these post-orogenic plutons to have cooled below magnetite blocking temperatures upon initial emplacement and to have had a mild subsequent thermal history within the stable craton with no evidence of any significant subsequent thermal overprinting. The similarity of this new Superior province pole with poles from the Slave and Rae provinces establishes the coherency of the Laurentia craton following Trans-Hudson orogenesis. This consistency supports interpretations that older discrepant 2.22 to 1.87 Ga pole positions between the provinces are the result of differential motion through mobile-lid plate tectonics. The East-Central Minnesota Batholith pole supports the NENA connection between the Laurentia and Fennoscandia cratons. The pole can be used to jointly reconstruct the paleogeographic positions of these cratons ca. 1780 Ma strengthening the position of these major constituents of the hypothesized late Paleoproterozoic supercontinent Nuna.

Suggested citation:
Swanson-Hysell, N.L., Avery, M.S., Zhang, Y., Hodgin, E.B., Sherwood, R.J., Apen, F.E, Boerboom, T.J., Keller, C.B., & Cottle, J.M. (2021). The paleogeography of Laurentia in its early years: new constraints from the Paleoproterozoic East-Central Minnesota batholith. Tectonics 40, e2021TC006751