284-7 Spatio-Temporal Trends in Late Paleozoic Metamorphic Temperatures in the Southern New England Appalachians

Session: The Deformation-Metamorphism-Fluid Triplet Governing Plate Boundaries and Orogens

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Abstract:

The thermal structure and evolution of orogenic crust exerts a fundamental control on lithospheric rheology and the geodynamic processes that shape mountain belts. While orogenic thermal architecture is often constrained from geodynamic models, xenoliths, or seismic imaging, few studies reconstruct large-scale orogenic thermal evolution directly from field-based structural, petrographic, and geochronologic datasets. The New England Appalachians expose a broad section of the middle to lower orogenic crust which formed during late Paleozoic orogenesis on the margin of Laurentia. This crustal section preserves evidence of high- to ultrahigh-temperature (UHT) metamorphism, intense ductile deformation, and widespread fluid-mediated mineral reactions across scales ranging from grains to regions. However, the relationships among metamorphism, deformation, and fluid flow remain enigmatic and are closely tied to the long-term thermal evolution of the orogen. We present new whole rock and mineral geochemistry, petrochronology, and phase equilibria modelling of samples from central Massachusetts and eastern Connecticut showcasing the spatio-temporal distribution of metamorphic temperatures during the Acadian-Neoacadian (Devonian-early Carboniferous) and Alleghanian (Carboniferous-Permian) orogenies in the New England Appalachians. Our results, integrated with existing regional datasets, find that high to ultra-high temperature (>700 °C) metamorphic domains are commonly separated or truncated by lower amphibolite to greenschist facies moderate-temperature (< 650-700 °C) zones, often representing increasingly localized strain along major Carboniferous shear zones. These thermal contrasts are also associated with distinct deformation styles and intensities, as well as late-metamorphic fluid infiltration. By binning metamorphic temperatures by ages from petrochronology, we reconstruct the evolving thermal architecture of the southern New England orogen from ~400–300 Ma, with implications for crustal reworking, strain localization, and the feedbacks between heat, deformation, and fluid flow during collisional orogenesis.

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

doi: 10.1130/abs/2025AM-8916

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