Timescales of magmatic processes during the 2013-2017 eruption at Volcán de Colima, Mexico

Hughes, Gerallt Emlyn (2022) Timescales of magmatic processes during the 2013-2017 eruption at Volcán de Colima, Mexico. PhD thesis, Birkbeck, University of London.

Abstract

Volcán de Colima is an active, continental arc stratovolcano in western Mexico, and its persistent activity presents hazards to >750,000 people near the volcano. The volcano has a history of Plinian eruptions, the most recent in 1818 and 1913, and less intense interplinian activity characterised by transitions between effusive and explosive events, such as the most recent 2013-17 eruption. The processes which control these eruptive style changes and timing of eruptions is still poorly understood. The relationship between pre-eruptive magmatic processes, such as magma storage, recharge and mixing, and volcano monitoring data is also poorly known, yet it is key to accurately interpreting monitoring data and understanding future hazards. In this study, mineral chemistry, petrography and diffusion modelling of the crystal cargo were combined to investigate the role of magma recharge during the 2013-17 eruption, and to investigate the relationship between recharge events and the monitoring record. The findings show that these andesites contain a diverse crystal cargo, recording complex pre-eruptive magmatic processes, and formed in a mid-crustal storage plumbing system at c.15 km depth. Here, evolved magmas are stored within a heterogeneous crystal mush and are occasionally recharged and mixed by mafic magmas before migrating into shallower reservoirs prior to eruption. Despite evidence of mafic recharge, a change in bulk composition towards mafic compositions was not observed. Long residence timescales of decades to centuries are recorded in evolved magmas, in contrast to shorter residence times of weeks to months in mafic magmas, indicating that mafic injections are ephemeral events within the evolved crystal mush. Placing these recharge events in time shows a strong relationship between some recharge events and features in the volcano monitoring record, which may be useful for interpreting monitoring data in the future. The findings suggest that Volcán de Colima is an open-system, steady-state volcano, where the magmas and crystal mush are kept in a persistently warmed and near-eruptible state, a feature recognised at an increasing number of arc volcanoes.

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