Investigating shifts in magma genesis at the Atitlan volcanic centre, Guatemala

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Over the past 14 Ma, the Atitlan volcanic centre has been producing a range of volcanic productsover three phases (Atitlan I 14-11 Ma, Atitlan II, 10-8 Ma, Atitlan III 1 Ma to present), includingstratovolcanoes, domes, and large and small volume ignimbrites, three of which have resulted inthe formation of calderas. The path of these calderas mirror a pattern which is near ubiquitous inGuatemalan arc-front volcanism, whereby the locus of activity shifts south/southwestwards overtime. This project will look into the geochemistry and petrology of the volcanic products of theAtitlan centre and produce a conceptual model that will explain the nature of the genesis of themagmas and their interactions with one another, as magma mixing has previously been identifiedas an important process here. It will also examine the change in magma generation processesas they have evolved over time. Atitlan is an especially important site to study, as relativelylittle 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 compressionaltectonic regimes overlie one another. This could manifest itself by producing hybrid magmaswith both decompression and flux melting signatures.The methods that will be used include collection of samples from the various eruptions, spotand profile analyses by SEM, EMPA and LA-ICP-MS as well as whole rock major and traceelement and radiogenic isotope analyses at Actlab, the Open University and the NERC IsotopeGeoscience Laboratories respectively. These will then feed into a variety of models includingvarious thermobarometers and phase equilibria models such as MELTS and EC-RA xFC