36 Rates, Dates, and Plates: Petrochronological Approaches to Unraveling Tectonometamorphic Histories

This session welcomes contributions  applying modern approaches in metamorphic petrology, geochronology, and structural geology to unravel the dynamics of convergent margin processes from the Appalachians and beyond. We encourage submission from Early Career participants.

Tuesday, 24 March 2026
8:00 AM - 12:00 PM
CCC, Room 22/23

Detrital zircon trace element fingerprinting and comparative U-Pb analysis of Moretown Terrane provenance more firmly establishes its peri-Gondwanan origin

Paper number: 36-7
Program: Technical Sessions
Time: 10:00 AM – 10:20 AM

Authors

Abstract

The Taconic arc terrane in New England was formerly thought to be peri-Laurentian before recently being redefined as peri-Gondwanan. The basis for reevaluation of the terrane’s origin is its detrital zircon U-Pb age distribution from upper Cambrian units: the Moretown and Albee formations. The age distribution of samples generally has a single, dominant 750–500 Ma age peak, characteristic of other peri-Gondwanan terranes, and lacks a prominent Grenvillian (1250–950 Ma) age peak, the dominant age peak from rift-related strata of eastern Laurentia. The tectonic interpretation has been strengthened by rift-related magmatism in New England being restricted in age (570–550 Ma) and the scarce and generally mafic rift units likely constituting an insignificant source of detrital zircons. However, an updated inventory of geological units along the eastern margin of Laurentia includes voluminous and felsic ca. 610–540 Ma rift-related magmatism in the eastern Canadian Appalachians and ca. 770–550 Ma rift-related magmatism in the central Appalachians. The occurrence of these rift-related units illustrates the potential non-uniqueness of the 750–500 Ma age peak that defines the Moretown Terrane as peri-Gondwanan. Moreover, new datasets and interpretations from the Taconic arc terrane elsewhere along the eastern margin continue to argue for its peri-Laurentian origin. This further elevates the need, beyond age alone, to test and clarify the petrogenetic origin of Moretown Terrane zircons in New England. Here, we investigate the trace element distribution of the 800–500 Ma age peak of zircons from the Moretown and Albee formations, binned by age interval, and compared to reference zircon trace element datasets, including from known Laurentian rift-related and peri-Gondwanan arc-related igneous samples from New England and the Canadian Appalachians. The Nb/Yb v. U/Yb results illustrate that the majority of 800–500 Ma Moretown Terrane detrital zircons (>80%) have a volcanic arc affinity and >90% from the most dominant age group (700-600 Ma). This is consistent with volcanic arc reference samples similarly containing >80-90% of zircon trace element data plotting in the volcanic arc domain. Results from zircon Nb/Yb vs. U/Yb are substantiated by other zircon trace element tectonomagmatic discrimination plots. In addition to more firmly establishing the tectonic affinity of the Moretown Terrane as peri-Gondwanan, new tectonostratigraphic insights of the peri-Gondwanan arc terrane and its origin are presented along with broader plate tectonic implications.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411492

© Copyright 2026 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.