30 Applications of Igneous Petrology, Geochemistry, and Geochronology to Understanding Earth and Other Planetary Systems

This session invites contributions that explore igneous systems through traditional and nontraditional methods. Studies that link crustal evolution, planetary formation, resource potential, and comparative planetology across temporal and spatial scales are especially encouraged.

Tuesday, 10 March 2026
1:30 PM - 3:30 PM
RCC, 104

Inside Andean Large Silicic Domes: Magma Storage and Timescales

Paper number: 30-2
Program: Technical Sessions
Time: 2:00 PM – 2:15 PM

Authors

Abstract

Quantifying the timescales of magma storage and mobilization is fundamental to understanding the evolution of large silicic systems and assessing their associated volcanic hazards. This study applies diffusion chronometry to plagioclase crystals from the Chao, Chillahuita, and Tocopuri domes in the Central Volcanic Zone (CVZ) of the Andes to constrain the thermal history of the magmatic system. We modeled Sr and Mg diffusion across 51 compositional transects using a finite-difference forward model, with diffusion coefficients referenced to a rheologically critical temperature of 750 °C. Our results yield diffusion timescales ranging from decades to millennia (10¹ to 10³ years) with most crystals recording short-lived thermal reactivation (<10³ years) at temperatures ≥ 750 °C. These short durations indicate that the magmatic system resided at sub-solidus, non-eruptible conditions for much of its history. The plagioclase crystals record complex growth zonation and diverse crystallization environments, reflecting long-term chemical heterogeneity within the reservoir. However, the brief high-temperature timescales derived from diffusion modeling imply that eruptible, mobile magma was only generated transiently, likely in response to short-lived reheating events such as magma recharge. We conclude that the CVZ magmatic system existed predominantly in a cool, crystal-rich, and immobile state, with punctuated thermal perturbations that remobilized magma and triggered eruption.

 

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411554

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