304 Integrating Geochronology and Geochemistry to Decipher the Tectonic Evolution of Orogenic Belts (Posters)

This session focuses on deciphering magmatic, metamorphic, depositional and deformational events recorded in orogenic belts via the integration of geochemistry and geochronology. We welcome contributions from modern applications of analytical methods aimed at unraveling orogenic events worldwide, fostering interdisciplinary discussion.

Wednesday, 22 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Revisiting the Winding Stair Gap (Central Blue Ridge, NC, USA): Preliminary U-Pb Geochronology of Metamorphic Zircons of the Taconic Orogeny

Paper number: 304-5
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The Appalachian Orogeny is comprised of overprinting collision and accretion through the Paleozoic Era. The Taconic Orogeny, within the Appalachian Orogeny, was driven by subduction of the Iapetus Ocean beneath Laurentia and the accretion of various oceanic arcs and lithosphere. The resulting Taconic peak metamorphism is well recorded within the exposed basement of the Central Blue Ridge at the Winding Stair Gap (North Carolina, USA). The exposed basement contains a variety of meta- pelitic and mafic lithologies, including biotite-garnet granulite, quartzo-feldspathic gneiss, sillimanite-garnet schist and amphibolites. Here we present new U-Pb ages of zircons separated from biotite-garnet granulite and an amphibolite lens encompassed within, providing insights into the complex tectonic and metamorphic evolution of the Central Blue Ridge.

The zircons analyzed in the present study are all euhedral, exhibiting their tetragonal structure. Even though they appear as typical magmatic zircons on a macro scale, CL imaging revealed their completely metamictizied character, appearing completely dark with high U and Th content, and lacking zoning patterns. Zircons from the amphibolite sample yielded a concordia age of 453.1±2.0 Ma (n=32, MSWD=1.8) and zircons from the biotite-garnet granulite sample yielded a concordia age of 457.4±3.0 Ma (n=28, MSWD=1.2). These ages are interpreted to record the peak granulite facies metamorphism during the Taconic Orogeny, consistent with previously reported U-Pb ages of zircons from garnet-bearing leucosomes within the same basement assemblage exposed at the Winding Stair Gap.

Future work will integrate geochemical and geo- and thermo-chronological constraints, attempting to resolve the temporal and thermal evolution of the Central Blue Ridge basement during post-Taconic orogeny.

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

doi: 10.1130/abs/2025AM-414813

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