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

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
8:00 AM - 12:00 PM
HBGCC, 217C

Rapid cooling of the Neoarchean Quetico metamorphic belt challenges the paradigm of long-lived, slow-cooling Archean metamorphism

Paper number: 88-2
Program: Technical Sessions
Time: 8:25 AM – 8:40 AM

Authors

Abstract

Higher and more variable metamorphic cooling rates among Phanerozoic rocks, compared to Archean, have been interpreted to indicate secular change in the global system of (plate) tectonics. We present metamorphic cooling rates from the c. 2.7 Ga Quetico Subprovince, Superior Province, Canada, using both garnet diffusion chronometry and 40 Ar/ 39 Ar biotite thermochronology. In contrast to the paradigm of low cooling rates for Archean metamorphic rocks (1’s of °C/Ma), our results require cooling rates ≥ 20–50 °C/Ma, comparable to many Phanerozoic examples. We argue that apparent homogeneity of low cooling rates for Archean rocks reflects, in part, the limited range of metamorphic environments from which data have been compiled. This itself might be an indirect indication of secular change in tectonic processes, insofar as there is greater variety of metamorphic and structural environments preserved from Phanerozoic orogenic belts. However, more comprehensive studies of cooling rates from a larger and more representative variety of Archean metamorphic environments and structural settings—comparable to the diversity of available Phanerozoic data—are needed to rigorously test hypotheses of secular change in global tectonic processes.

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

doi: 10.1130/abs/2025AM-412734

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.