130-1 Were Plate Tectonics Active During the Neoarchean? Thermobarometry, U-Pb and Lu-Hf Geochronology of the English River Subprovince, Ontario, Canada

Session: Evolution of Orogenic Belts Through Time: Insights from Sedimentation, Deformation, Magmatism, and Metamorphism, Part II

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Abstract:

The Neoarchean is of particular interest for understanding the origin of plate tectonics due to the large-scale changes happening on Earth during this time, including the start of the supercontinent cycle, the Great Oxidation Event, and life becoming more complex which have been attributed to the start of plate tectonics.  The Superior Province is of particular interest for investigating whether plate tectonics were active in the Neoarchean because it is the largest Archean craton, assembled between 4.3 and 2.57 Ga, and has conflicting hypotheses for how it formed including a plate tectonic model and a non-plate tectonic model.  New temperature and pressure constraints from modern thermobarometry provide more accurate peak metamorphism conditions for the English River Subprovince (ERSP), an E-W trending metasedimentary belt in the western Superior Province, between  790-820^oC and 5.5-6.0 kbar for amphibolite facies and 810-850^oC and 5.5-7.0 kbar for granulite facies.  Samples for thermobarometry were collected along two transects and show a symmetrical distribution of temperature which is inconsistent with a subduction setting for the ERSP. Zircon U–Pb dating and garnet Lu–Hf dating were also conducted to constrain the timing of deformation, magmatism, and metamorphism, and provide the first ages of metamorphic units in the ERSP. Preliminary data suggests magmatism occurs before metamorphism, which is also inconsistent with subduction.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10763

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