The Long-Term Life-Cycle of Nevado de Toluca Volcano (Mexico): Insights Into the Origin of Petrologic Modes

Abstract

The petrologic diversity of volcanic rocks reflects the dynamics of magma reservoirs and the temporal evolution of magma chemistry can provide valuable information for hazard assessment. While some stratovolcanoes monotonously produce intermediate magmas (55-68 wt% SiO 2), dominantly erupted magma types (e.g., basaltic andesite, andesite or dacite) frequently differ even between neighboring volcanoes. If such differences arise due to thermal maturation processes over time or are predetermined by other properties of magmatic systems remains poorly understood. This study helps to elucidate the underlying factors modulating the chemistry of the magma preferentially erupted by Nevado de Toluca volcano in Central Mexico. We present a new dataset of bulk-rock and mineral chemistry spanning the entire 1.5 Million years of the volcanos' eruptive history. The results reveal that Nevado de Toluca dacites and minor andesite originate in a stable configuration of pre-eruptive processes and plumbing system architecture by hybridization between an upper crustal silicic mush and deeper sourced basaltic andesite magmas. Yet, a subtle trend toward increasing silica content with time (2 wt% in 1.5 Ma) and episodicity in magma hybridization conditions are observed. We use thermal simulations of pulsed magma injection to probe the controlling variables on the temporal variation and compositional mode of magma geochemistry. The results show that the subtle temporal trend toward increasing bulk-rock SiO 2 content is plausibly explained by slightly dropping recharge rates and continued upper crustal reservoir growth. Our modeling also shows that the dominant composition of eruptible magmas ("petrologic mode") can shift as a function of magma flux, extrusive:intrusive ratio and temperature of the recharge magma. A comparison of SiO 2 whole rock distributions for monotonous Mexican stratovolcanoes and their peripheral cones shows that their petrologic modes vary in concert, indicating that the recharge magma chemistry or temperature is a major control on the preferentially erupted magma composition for these volcanoes.

Geochemical variability as an indicator for large magnitude eruptions in volcanic arcs

“…3 a, caldera systems producing diverse magma chemistry like Mazama, Santorini, or Los Humeros have lifespans equivalent or shorter than many examples of long-lived stratovolcanoes (e. g., Uturuncu, Aucanquilcha, Xinantécatl) that have produced monotonous andesitic-dacitic magma chemistry throughout their > 1.5 Ma histories 41 – 43 . In order to maintain their monotonous character over such long timescales, pre-eruptive magma storage depth and temperatures for such volcanoes must be relatively constant and balanced by eruption rates 44 . For younger, more monotonous basaltic systems (e.g., Tolbachik, Merapi; Fig.…”

A new calibration of the OPAM thermobarometer for anhydrous and hydrous mafic systems

“…The P-T-X of magma during storage and ascent plays a leading role in modulating eruptive dynamics (Higgins and Caricchi, 2023;Popa et al, 2021). Therefore, quantitative tools to describe pre-eruptive magmatic P-T-X, such as the new thermobarometric equations presented here, can be useful to: (i) petrologically monitor active volcanoes during protracted eruptions, particularly to compare evolving geochemical and geophysical signals Longpré et al, 2014;Magee et al, 2018Magee et al, , 2020Saunders et al, 2012;Stock et al, 2018); (ii) understand medium-term and long-term evolution in magma storage conditions by studying multiple temporally constrained volcanic deposits (Bouvet de Maisonneuve et al, 2021;Forni et al, 2018;Giordano and Caricchi, 2022;Higgins et al, 2021a;Smithies et al, 2023;Weber et al, 2020). To assess the utility of our new thermobarometer for studying volcanic systems, we apply our calibration to the OPAMSAT melts of two case study eruptions 5.…”

“…Irrespective of the calibration strategy, thermobarometers have significant scope as petrological volcano monitoring tools. For example, P data can independently validate geophysical estimates of pre-eruptive magma storage depth during or after eruptions (Hartley et al, 2018;Stock et al, 2018;Ubide et al, 2023) or catalogue past changes in magma P and T for eruptions of volcanoes that lack a protracted historical monitoring record (Bouvet de Maisonneuve et al, 2021;Higgins et al, 2021a;Jorgenson et al, 2024;Weber et al, 2020).…”