25 Integrating metamorphism, mass transfer, and magmatism across the American Cordillera (Posters)

Subduction drive crustal evolution and element cycling between Earth’s surface and interior. This session highlights petrological research integrating field data, geochemistry, geochronology, and experimental or numerical modeling to illuminate subduction dynamics across the American Cordillera.

Thursday, 23 April 2026
8:00 AM - 5:30 PM
LMH, 5th Floor Chapel

Zinc Isotopes Trace Lithogenic and Biogenic Recycling in Cordilleran Continental Arcs

Paper number: 25-6
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

  • Arturo Gómez-Tuena Presenting Author
    Universidad Nacional Autónoma de México, Instituto de Geologia, Mexico City, Mexico City
  • Carlos Errázuriz-Henao
    Universidad Nacional de Colombia, Facultad de Minas, Medellín, Antioquia
  • Mattia Parolari
    Universidad Nacional Autónoma de México, Instituto de Geología, Mexico City, Mexico City
  • Frédéric Moynier
    Université Paris Cité, Institut de Physique du Globe de Paris, Paris

Abstract

Arc magmatism has played a fundamental role in shaping the composition of the oceans and atmosphere and, consequently, the evolution of life on Earth. However, the extent to which biological processes modulate arc magmatism remains poorly understood. A significant fraction of the CO2​ emitted by arc volcanoes is thought to originate from subducted microfossils, organic matter, and carbonate sediments; yet, the fate of carbon within terrestrial reservoirs remains difficult to trace because of its complex partitioning among minerals, fluids and gases. Zinc isotopes have emerged as promising tracers of subducted carbon due to the isotopic contrasts between silicic and carbonate lithologies. In the ocean, Zn behaves as a micronutrient: organic tissues preferentially incorporate light isotopes, while biogenic carbonate shells are enriched in heavy Zn isotopes. Consequently, biogenic carbonate sediments display heavier Zn isotopes (δ66Zn≈+0.94‰) than the continental crust (δ66Zn≈+0.27‰) or the upper mantle (δ66Zn≈+0.16‰), suggesting that Zn isotopes may distinguish subducted carbonate from lithogenic inputs in arc magmas. Despite this potential, previous studies of arc volcanic rocks have not identified a clear carbonate-derived Zn isotopic signal, whereas heavy Zn isotopes are instead observed in intraplate basalts where the influence of subduction is difficult to recognize.

To resolve this apparent discrepancy, we analyzed Zn isotopic compositions of well-characterized arc volcanoes from Mexico and Colombia: archetypal Cordilleran arcs developed on thick, ancient continental crust. In both regions, the dominant volcanism consists of high-Mg# andesites that are virtually identical in their major-element compositions. However, andesites from the two arcs differ markedly in radiogenic isotopes and trace-elements, reflecting contrasting subduction inputs. In Mexico, intense forearc subduction erosion introduces predominantly continental material into the mantle wedge. Conversely, the non-erosive character of the Colombian margin allows biogenic carbonates and organic-rich clays to be transported into the subduction zone. Consistent with these contrasting inputs, Mexican andesites display significantly lighter Zn isotopic compositions (δ66Zn≈0.23±0.02‰) than their Colombian counterparts (δ66Zn≈0.31±0.03‰). The Zn isotopic variations are independent of proxies for partial melting or crystal fractionation, but correlate with trace-element ratios and radiogenic isotopes sensitive to lithogenic and biogenic inputs (e.g., Ba/Nb,U/La,87Sr/86Sr). Together, these results demonstrate that Zn isotopes provide a robust link between surface biogeochemical processes and deep carbon cycling in Cordilleran convergent systems.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3

doi: 10.1130/abs/2026CD-410927

© Copyright 2026 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.