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

Deposition, Burial, Orogenesis, and Lower Crustal Metamorphism in a Deeply Exhumed Backarc Basin

Paper number: 130-2
Program: Technical Sessions
Time: 1:50 PM – 2:05 PM

Authors

Abstract

Backarc basins coincide with attenuated and hot lithosphere behind many subduction zones on Earth. These regions can have Moho temperatures approaching 900 C which can lead to pervasive high to ultrahigh temperature metamorphism during emplacement of mantle-derived magma. This stretched lithosphere can eventually give rise to backarc basalts which can have both arc- and mid-ocean ridge basalt (MORB)-like affinity. Basins consisting of locally thick successions of sediment atop this stretched mafic basement can have depocenters >10 km in thickness. The tectonic fate of backarc basins remains poorly understood, particularly during the closure and burial of backarc basins as a consequence of arc collision. The >400 km2 Upper Deck domain in the Athabasca granulite terrane in northern Saskatchewan, Canada, consists of a >6 km-thick succession of metasedimentary gneisses intruded by MORB-like mafic granulite sills that achieved P-T conditions of >1.4 GPa and >950 C during backarc basin closure and orogenesis. New results from LA-ICP-MS and chemical abrasion ID-TIMS U-Pb zircon geochronology constrain the provenance, burial, and lower crustal metamorphism of the metasedimentary succession. Abundant 2.98-2.64 Ga detrital zircon grains of presumed local provenance occur within the metasedimentary gneisses that host the mafic granulites. These gneisses are partially melted adjacent to the mafic granulite sills and contain detrital zircon cores with prominent 2.61-2.54 Ga metamorphic rims. High precision chemical abrasion ID-TIMS 207Pb/206Pb dates of metamorphic zircon with soccer ball zoning constrain the onset of deep crustal metamorphism to 2607.40 ± 0.92 Ma. Backarc basin sediments can thus be exceptional recorders of backarc burial and metamorphism during orogeny.

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

doi: 10.1130/abs/2025AM-414486

© 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.