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

This session explores the evolution of orogenesis on Earth, encompassing applications of sedimentology, petrology, geochemistry, paleomagnetism, geochronology, and structural geology. We encourage studies combining field observations with laboratory and modeling techniques to unravel tectonic processes.

Monday, 20 October 2025
1:30 PM - 5:30 PM
HBGCC, 217C

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

Paper number: 130-1
Program: Technical Sessions
Time: 1:35 PM – 1:50 PM

Authors

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  790-820oC and 5.5-6.0 kbar for amphibolite facies and 810-850oC 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 Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414592

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