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

Geochemical variations across the Sierra Nevada, Central Mexico: evaluating the reworking of the subduction components in rear-arc magmatism

Paper number: 25-3
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The geochemical diversity of orogenic andesites in the Trans-Mexican Volcanic Belt (TMVB) has been recently attributed to the recycling of subducted materials—specifically through the melting of subduction mélanges. While along-arc variations at the volcanic front are relatively well-understood and linked to the subduction of ablated forearc crust, the mechanisms responsible for transferring these signatures toward the rear of the volcanic belt remain yet to be addressed. In this view, The Sierra Nevada, a roughly N-S volcanic chain orthogonal to the arc front, provides a strategic transect to investigate these across-arc processes and the potential maturation of the continental crust.

The Sierra Nevada chain comprises four major stratovolcanoes: Popocatépetl, Iztaccíhuatl, Tlaloc, and Telapon. In this study, we present new geochemical and petrographic data for the three northernmost centers—Iztaccíhuatl, Tlaloc, and Telapon. Our preliminary results reveal a systematic spatial gradient where lavas become progressively more felsic and enriched in incompatible trace elements with increasing distance from the trench. Despite their evolved compositions, these northern centers maintain relatively high Mg# values—a signature difficult to reconcile with simple upper-crustal crystal fractionation and instead indicative of a primary feature inherited from the deep-seated interaction between subducted components and the mantle wedge.

We will test whether these geochemical trends can be explained by the progressive melting of buoyant mélange diapirs under changing P-T-H2O conditions—involving increasing temperature and possibly decreasing water content as the slab deepens. The purpose of the study is to determine if these across-arc variations can be coherently integrated into the mélange-melting model we recently proposed for the arc-front volcanoes. By combining detailed petrography with thermodynamic modeling (e.g., Perple_X and MELTS), this research aims to provide a more comprehensive understanding of how subduction components are reworked and distributed across the rear of the TMVB.

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

doi: 10.1130/abs/2026CD-410849

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