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

New Geochronologic and Geochemical Constraints on Paleogene Magmatism in the Southern Omineca Belt, Southeastern British Columbia

Paper number: 304-3
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The southern Omineca belt in southeastern British Columbia, Canada, contains voluminous Paleocene to Eocene granites generally thought to represent the northern culmination of the North American Cordilleran Anatectic Belt. Some of these granites, like the Ladybird Suite, are linked to metamorphic core complex development, while others have an uncertain tectonic setting. We present new zircon U/Pb ages and whole rock geochemistry for 25 Paleocene to Eocene plutons across a wide area (>7000 km2), with the goal of better understanding their petrologic development and tectonic affinity. Based on these new data, three groups of Paleogene intrusive rocks have been identified: (1) the Ladybird granites, (2) the Eocene Okanagan batholith, and (3) the Coryell suite. The Ladybird granites and Eocene Okanagan batholith range in age from 68 to 51 Ma and are geochemically and temporally indistinguishable. Both are peraluminous, exhibit LREE enrichment, contain inherited zircon cores, and have Rb/Sr vs Sr patterns consistent with muscovite dehydration melting during crustal anatexis. However, the Ladybird granites are geochemically and geographically linked to the formation of the Thor-Odin and the Valhalla domes while the Eocene Okanagan batholith has not been previously genetically linked to a metamorphic core complex. The volume and spatial extent of the Eocene Okanagan batholith requires large-scale melt generation, not only from magma produced through high-grade migmatization in core complex footwalls. Temporally and spatially overlapping with the Ladybird Granites and the Eocene Okanagan batholith, the Coryell suite includes metaluminous to weakly peraluminous monzonites and syenites ranging in age from 52 to 48 Ma that exhibit no zircon inheritance. The Coryell suite is geochemically distinct from the older granites and indicates a different petrogenetic process. Recognizing both spatially significant suites as geochemically distinct requires increasing complexity for proposed regional models of core complex formation and its relation to magmatism.

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

doi: 10.1130/abs/2025AM-414276

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