Summary: Minnesota and Ontario both preserve rocks that relate to the initial formation of the core of the North American continent, the Superior Province. These rocks formed during the Archean Eon (4000-2500 Ma), with a large proportion being emplaced and amalgamated together in the Neoarchean at ~2700 Ma. The present-day configuration of the Superior Province largely reflects this event, although earlier Archean rocks are locally preserved. While the tectonic and paleoenvironmental setting in younger, post-Archean rocks is well-understood, similar inferences concerning Archean domains are debated. This is due to the fact that a hotter Earth is predicted during this time period, which may have favored a predominance of non-plate tectonic processes. Based on theoretical studies, many workers have inferred that the transition from non-plate tectonic processes to modern-styles of geodynamics (subduction-accretion processes) was likely to have occurred around the culmination of the Archean Eon. This talk explores the rock record of Minnesota’s nearest Canadian neighbor, Ontario, that preserves an extensive, nearly one-billion-year history spanning this transitional time period. New evidence suggests that the origin of the southwestern Superior Province was in the Eoarchean (at ~3650-3600 Ma) as a result of plume-dominated processes, while the Neoarchean history (at ~2700 Ma) preserves characteristics consistent with a continental arc environment. These results are placed within a new regional framework and are used to infer why base and precious metal deposits occur where they do within Ontario and Minnesota.

Biography: Dr. Ben M. Frieman is currently a contract Geologist with Ivanhoe Electric, conducting economic exploration. Previously, Ben was a Postdoctoral Fellow and Research Associate as part of Laurentian University’s Mineral Exploration Research Centre (LU-MERC). There, Ben was part of the Metal Earth research initiative, which is focused on elucidating the lithotectonic evolution of the Archean Superior Province in order to better understand differential metal endowment in the region. This work utilized field-based investigations, (isotope) geochemistry, and integrated geophysics. Prior to his time at LU-MERC, Ben completed his Ph.D. at the Colorado School of Mines in 2018. There his dissertation work was similarly focused on the Superior Province and included both structural and multi-isotope detrital zircon investigations to constrain Archean geodynamic processes, related crust-mantle evolution, and how deformation processes influence the present-day distribution of base and precious metal deposits. Ben also attended the University of Maine where he obtained a M.Sc. in Earth Sciences in 2012 and the University of Minnesota where he obtained B.Sc. degrees in Geology and Geophysics in 2010.