Investigating shifts in magma dynamics of the Atitlán volcanic centre, Guatemala

Solid Earth Dynamics

NHM

BBK

Over the past 14Ma, the Atitlán volcanic centre has been producing a range of volcanic products over three phases (Atitlán I 14-11 Ma, Atitlán II, 10-8 Ma, Atitlán III 1 Ma to present), including stratovolcanoes, domes, and large and small volume ignimbrites, three of which have resulted in the formation of calderas. The path of these calderas mirror a pattern which is near ubiquitous in Guatemalan arc-front volcanism, whereby the locus of activity shifts south/southwestwards over time. This project will look into the geochemistry and petrology of the volcanic products of the Atitlán centre and produce a conceptual model that will explain the nature of the genesis of the magmas and their interactions with one another, as magma mixing has previously been identified as an important process here. It will also examine the change in magma generation processes as they have evolved over time. Atitlán is an especially important site to study, as relatively little is known about the magma plumbing system feeding the volcanoes, especially for the pre- Quaternary volcanism. It also represents a rare location where extensional and compressional tectonic regimes overlie one another. This could manifest itself by producing hybrid magmas with both decompression and flux melting signatures.

The methods that will be used include collection of samples from the various eruptions, spot and profile analyses by SEM, EMPA and LA-ICP-MS as well as whole rock major and trace element and radiogenic isotope analyses at Actlab, the Open University and the NERC Isotope Geoscience Laboratories respectively. These will then feed into a variety of models including various thermobarometers and phase equilibria models such as MELTS and EC-RAχFC.

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