167 Integrating Geochronology and Geochemistry to Decipher the Tectonic Evolution of Orogenic Belts

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.

Tuesday, 21 October 2025
8:00 AM - 12:00 PM
HBGCC, 217B

Silurian Zircon Age from the Chunky Gal Mountain Amphibolite (NC, USA)

Paper number: 167-11
Program: Technical Sessions
Time: 10:45 AM – 11:00 AM

Authors

Abstract

The Appalachian Orogeny recorded series of tectonic events associated with accretion of various terranes, evolving throughout the Paleozoic and marking the assembly of the Pangea supercontinent. Owing to the multiple stages of deformation and/or metamorphism these terrains experienced, the decipher of their tectonothermal evolution is difficult and a long-standing challenge. Chunky Gal Mountain (CGM) complex resides within the Cartoogechaye Terrane of the Central Blue Ridge and comprises of amphibolites that surrounds the Buck Creek ultramafic complex. These amphibolites are bound by major thrust faults in contact with pelitic schists and gneisses. With limited data, the CGM amphibolites have been previously interpreted to have protoliths that formed as oceanic basalts or gabbros in a mid-ocean ridge setting. Here we present preliminary zircon U-Pb age from a CGM amphibolite sample.

The examined amphibolite sample is made up of dominantly hornblende and plagioclase and have the typical salt-and-pepper texture. The analyzed zircons have euhedral shapes with typical magmatic tetragonal structure and have seldom inclusions of apatite and titanite. The zircons have yielded an 206Pb/238U weighted mean age of 434.9±3.6 Ma (n=19, MSWD=1.7). This age is consistent with independently reported Silurian ages from the Marble Hill Hornblende Schist amphibolite of the Western Blue Ridge, and in conflict with the current interpretation of Taconic metamorphism for the CGM complex. We propose that this mafic body may represent the continuation of a remnant Iapetus Oceanic lithosphere at the Laurentian margin that extends to the southernmost Appalachians, and to be emplaced into the Taconic Central Blue Ridge at a later stage during the remainder of the Appalachian Orogeny.

This preliminary data set will be expanded to include a larger set of samples and will be integrated with geochemical and geo- and thermo-chronological constraints to thoroughly decipher and characterize the tectono-stratigraphically important Chunky Gal Mountain amphibolites to provide insights into the tectonic evolution of the Central Blue Ridge.

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

doi: 10.1130/abs/2025AM-414938

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