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

The temporal control on the isotopic compositions of the Antarctic Peninsula arc

Paper number: 167-7
Program: Technical Sessions
Time: 9:40 AM – 9:55 AM

Authors

Abstract

Radiogenic isotopic compositions of arc magmas are a key tool for studying active margin evolution. They have two isotopic end-members: melts formed mostly from juvenile asthenosphere and melts sourced from evolved continental crust/continental lithospheric mantle. Cordilleran-margins are typically more isotopically juvenile near the trench, and conversely, increasingly evolved landward. However, this model has not been tested on the ~1,500km long Mesozoic-Cenozoic arc of the Antarctic Peninsula. Here we show that while geochemical compositions remain largely constant, radiogenic isotopes become increasingly juvenile with time. Unlike other continental arcs, there is no association between isotopic composition and spatial distribution. This is attributed to: (i) slow subduction of young oceanic lithosphere, resulting in narrowing of the arc and reduced capacity to incorporate continental crust into melts, and (ii) the Cenozoic decrease in convergence rate, which reduced the friction in the slab-overriding plate interface, allowing the arc melts to increasingly source from young juvenile asthenosphere.

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

doi: 10.1130/abs/2025AM-413385

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