- An opportunity to research one of the best exposed volcanic sequences on Earth.
- Contribute to understanding one of the principal controls on volcanic eruptions, their deposits and volcanic hazards.
- Develop expertise in a variety of field and laboratory techniques to resolve the evolution of volatile elements in volcanic systems
Volatiles like H2O, CO2, S, F and Cl are key components of magmas and are inherited from their source regions. Their ability to dissolve in magmas changes during magma ascent due to changes in pressure and temperature. When volatiles saturate, exsolved fluids and bubble expansion can change the physical properties (e.g. viscosity) of a magma, and in some cases may even help to remobilise stagnant, crystal-rich mushes and trigger explosive eruptions. In addition to controlling the eruption of a magma, volatiles are also likely to play an important part in controlling the nature of their deposits. Ignimbrites are the deposits formed by pyroclastic density currents, but the controls on whether these deposits remain unconsolidated or weld during deposition may also in part depend on the volatile content of the magma being erupted. Gaining a complete picture of volatile evolution from magma mush, to eruption, to surface deposit is therefore critical for understanding the most hazardous components of explosive volcanoes.
Melt inclusion studies currently represent the state-of-the-art in reconstructing pre-eruptive magmatic volatile contents. However, melt inclusions are affected by a number of post-entrapment processes that can modify or reset their volatile contents on timescales of hours to years (e.g. Hartley et al., 2014). Recent studies have highlighted the potential of the mineral apatite as an alternative proxy for tracking volatiles in magmas (e.g. Stock et al., 2016). The apatite crystal structure can host a range of volatile species that are important for understanding volatile budgets. Apatite is more retentive of these elements than many silicate minerals and glasses, and it can preserve a record of magmatic volatile contents even where the glass is largely degassed. Apatite also hosts other trace and redox-sensitive elements that can be used to build a detailed picture of pre-eruptive magma storage conditions (Miles et al., 2013). However, the benefits of apatite are often offset by its small grain size, which can hinder detailed analytical study of its rich volatile record.
By contrast, haüyne is rare, but often large S-rich mineral found in highly Si-undersaturated magmas. It has received comparatively little attention as a monitor of volatile evolution and excess degassing, but its size enables a detailed examination of its chemical and textural characteristics. Early studies have shown a fascinating range of textural varieties that have tentatively been shown to reflect episodes of volatile sparging during magma accumulation (Cooper et al., 2015).
This project is the first to propose examining how apatite and haüyne can be used in tandem to provide a detailed and complementary record of volatile evolution leading up to a Plinian eruption. The project will focus on the 668ka Arico ignimbrite – a rare welded ignimbrite formed from the eruption of the Las Cañadas volcano, Tenerife. State-of-the-art analytical techniques (SEM, EPMA, LA-ICP-MS and SIMS) will be used to carry out in situ textural and chemical analyses of both crystal types. This combination provides an unrivalled opportunity to track the lead up to one of the most significant eruptions of the Las Cañadas volcano and the circumstances that led to the welding of its pyroclastic density current deposits. Understanding how volatile elements behave in magmas has important implications beyond unravelling the events that led up to eruptions, including the formation of hydrothermal ore deposits that are commonly found in association with many volatile-saturated, S-rich volcanic centres.
Figure 1: The modern-day Teide volcano, Tenerife. Teide sits on top of the much larger Las Cañadas volcano from which the Arico ignimbrite formed 668 ka.
HostUniversity of Leicester
- Dynamic Earth
Dr Andrew Miles ([email protected])
Prof Mike Branney (University of Leicester)
Dr Cees-Jan de Hoog (University of Edinburgh)
The successful student will be accompanied in the field to gather juvenile pumice samples from the Arico ignimbrite, Tenerife. These samples will supplement an existing collection gathered by the PIs. Quantitative textural and compositional characterisation will be carried out at the University of Leicester using a scanning electron microscope (SEM) coupled with Zeiss’ Minerlogic software and laser ablation mass spectrometry. Crystals will be analysed in situ from thin section or mineral separates, with major and some volatile elements determined by a combination of SEM and electron microprobe. Volatile elements will also be measured by secondary ionisation mass spectrometry (SIMS) at the University of Edinburgh following a grant application to the facility.
Training and skills
You will receive full field training from experienced field geologists prior to, and during, your field season. You will also be trained in the use of state-of-the-art analytical equipment including quantitative evaluation of minerals, SEM, and high-resolution mass spectrometry. This training will provide you with a unique set of skills that will be attractive to industrial and academic employers. You will join a thriving community of volcanologists, igneous petrologists and applied researchers.
Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2-provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.
Further details on how to contact the supervisor for this project and how to apply for this project can be found here:
For any enquiries related to this project please contact Andrew Miles ([email protected]).
To apply to this project:
- You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2024.
- You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.
- Please submit your application and complete the host institution application process via: https://le.ac.uk/study/research-degrees/funded-opportunities/centa-phd-studentships. Please scroll to the bottom of the page and click on the “Apply for NERC CENTA Studentship” button. Your CV can uploaded to the Experience section of the online form, the CENTA application form 2024 can be uploaded to the Personal Statement section of the online form. Please quote CENTA 2024-L8-CENTA2-SGGE1-MILE when completing the application form.
Applications must be submitted by 23:59 GMT on Wednesday 10th January 2024.
A thorough review of the latest literature will be conducted. Fieldwork and sample collection will be conducted on Tenerife within the first six months. Training in SEM imaging and point analysis will be provided at the University of Leicester. An application to the NERC ion microprobe facility will be made for volatile and trace element analysis. Attend a national conference.
Ongoing sample preparation and analysis. Presentation of results at large national and international conference.
Integration of data will provide a model for volatile evolution. Publication of papers. Presentation at large national and international conference.
Cooper, L.B., Bachmann, O., Huber, C., 2015. Volatile budget of Tenerife phonolites inferred from textural zonation of S-rich haüyne. Geology. 43, 423-426.
Hartley, M.E., Bali, E., Mclennan, J., Neave, D., Halldorsson, S.A., Melt inclusion constrains on petrogensis of the 2014-2015 Holuhraun eruption, Iceland. Contributions to Mineralogy and Petrology, 173:10.
Miles, A.J., Graham, C.M., Hawkesworth, C.J., Gillespie, M.R., Hinton, R.W., EIMF, 2013, Evidence for distinct stages of magma history recorded by the compositions of accessory apatite and zircon: Contributions to Mineralogy and Petrology, v. 166, p. 1-19.