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

Over the past 14 Ma, the Atitlan volcanic centre has been producing a range of volcanic products
over three phases (Atitlan I 14-11 Ma, Atitlan II, 10-8 Ma, Atitlan 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
Atitlan 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. Atitlan 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-RA xFC