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

Thermodynamic Modeling of Subduction-Mélange and Hydrated Lithospheric Mantle Constrains Water Fluxes, Seismicity, and Arc Magmatism Along the Cocos Plate Beneath Central Mexico

Paper number: 25-9
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

  • Fabián Gutiérrez Aguilar Presenting Author
    Posgrado en Ciencias de la Tierra, Instituto de Geología, Universidad Nacional Autónoma de México, Coyoacán , CDMX
  • Mattia Parolari
    Instituto de Geología, Universidad Nacional Autónoma de México, Coyoacán , CDMX
  • Arturo Gómez Tuena
    Instituto de Geología, Universidad Nacional Autónoma de México, Coyoacán , CDMX
  • David Hernández Uribe
    Department of Earth and Environmental Sciences, University of Illinois, Chicago, IL
  • Anthony Ramírez Salazar
    Instituto de Geología, Universidad Nacional Autónoma de México, Coyoacán , CDMX

Abstract

Beneath central Mexico, the Cocos plate exhibits flat-to-steep subduction, driving fluid-related processes like slow slip events (SSE) and intermediate-depth seismicity (IDS) to mantle serpentinization and H2O -rich magmatism in the Trans-Mexican Volcanic Belt (TMVB). Yet, the controls on how and where these fluids are generated and transferred—whether governed by slab dehydration, redox conditions, or lithologic heterogeneity—remain debated. In this work, we apply Gibbs free-energy minimization along slab-top and Moho geotherms to model phase equilibria, H2O release, porosity, volume change, and fluid flux in sediments, mafic oceanic crust, hydrated lithospheric mantle, and subduction-mélange under varying hydration, redox, and hybridization. Sediments and mafic crust dehydrate at shallow to intermediate depths, limiting deep fluid transport. Instead, along the flat slab, talc- and chlorite-rich subduction-mélanges and serpentinized mantle retain most bound water, keeping porosity <0.01 and trapping fluids in an overpressured interface consistent with SSE. As the slab steepens, epidote breakdown in subduction-mélanges and brucite + amphibole + antigorite breakdown in serpentinized mantle generate dehydration pulses up to ~107 kg m–2 Myr–1, porosity up to 0.5, and solid + fluid volume changes ≤355.7 J bar−1, exceeding percolation thresholds and promoting IDS by dehydration embrittlement and stress transfer. During steep subduction, amphibole (subduction-mélange) and antigorite + chlorite (lithospheric mantle) breakdown deliver a 109 Tg H2O Myr–1 flux to the mantle wedge, fueling TMVB magmas. Thus, subduction-mélanges and hydrated lithospheric mantle form a connected fluid system that mediates where fluids accumulate, when they are released, and how they modulate the Cocos plate’s mechanical behavior.

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

doi: 10.1130/abs/2026CD-410738

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