73-3 Chemical-Temporal Complexity in the Eruptive Products of Xitle Volcano, Mexico: A Window into a Complex Monogenetic Magmatic System and the Underlying Mantle Wedge

Session: Using Volcanic Deposits to Help Us Understand Volcanic and Magmatic Processes (Posters)

Poster Booth No.: 273

Presenting Author:

Jamshid Ahmadi

Authors:

Ahmadi, Jamshid¹, Widom, Elisabeth², Sanchez, Rachelle³, Kuentz, David C.⁴, Guilbaud, Marie-Noelle⁵, Siebe, Claus⁶, Medina Jaen, Miguel⁷, Zamorano Orozco, José Juan⁸, Straub, Susanne M.⁹

(1) Department of Geology & Environmental Earth Science, Miami University, Oxford, Ohio, USA, (2) Department of Geology & Environmental Earth Science, Miami University, Oxford, OH, USA, (3) Volcanic Risk Solutions, School of Agriculture and Environment, Massey University, Palmerston North, New Zealand; Department of Geology & Environmental Earth Science, Miami University, Oxford, Ohio, USA, (4) Department of Geology & Environmental Earth Science, Miami University, Oxford, Ohio, USA, (5) Departamento de Vulcanología, Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad de México, Mexico, (6) Departamento de Vulcanología, Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad de México, Mexico, (7) Instituto Nacional de Antropología e Historia, Ciudad de México, Mexico, (8) Departamento de Vulcanología, Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad de México, Mexico, (9) Lamont Doherty Earth Observatory at the Columbia University, Palisades, NY, USA,

Abstract:

Monogenetic volcanoes are the most common volcanic features on Earth and despite their usually small sizes they can pose significant hazards, especially near populated areas, highlighting the importance of understanding their eruptive history and geochemical evolution. Xitle Volcano, a ~1600-year-old monogenetic cone on the southern edge of Mexico City and the central TMVB, destroyed several pre-Hispanic settlements during its eruption. Xitle eruptive products exhibit complex chemical-temporal variations which may result from either fractional crystallization and crustal assimilation (AFC) of a single magma batch or magma recharge with mixing and/or mingling of multiple melts from a heterogeneous mantle source. To investigate this, we present major and trace element data and Sr–Nd–Pb–Os isotopes from 40 samples capturing the entire duration of the eruption, integrated with new stratigraphic mapping and petrologic observations.

 

Variations in Sr-Nd-Pb-Os isotopic signatures occur throughout the eruption sequence but show no correlation with SiO₂ or Mg#, arguing against simple AFC processes. This interpretation is also supported in Os–Sr–Pb isotope space and MELTS modeling. Alternatively, distinct geochemical and isotopic groupings in major and trace elements, along with petrographic evidence such as magma mingling textures and disequilibrium features in olivine crystals, support a model involving magma recharge and mixing among at least three compositionally and isotopically distinct magma batches. Magma Chamber Simulator (MCS) modeling confirms this scenario, successfully reproducing the observed compositions through successive magma recharge events. These magma batches originated from a heterogeneous mantle wedge metasomatized by variable slab-derived fluids/melts dominated by subducted terrigenous sediment. Osmium isotope systematics imply serial fluid addition from the slab, along with progressive melt depletion and oxidation of the mantle wedge, as likely processes governing mantle wedge evolution beneath Xitle.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7186

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