Project highlights

  • A unique petrological perspective gained from looking inside an active volcano
  • Contribute to understanding one of the principal controls on volcanic eruptions and volcanic hazard assessment
  • Develop expertise in a variety of field and laboratory techniques to resolve the evolution of volatile elements in volcanic systems.

Overview

Accurate and reliable forecasting of volcanic eruptions remains one of the principal objectives of modern volcanology and is often reliant on real-time gas monitoring. Accurate interpretation of gas monitoring data relies on a quantification of the likely dissolved volatile (H2O, CO2, S, F, Cl) contents in the pre-eruptive magma. This is particularly the case when monitoring persistently degassing volcanoes that have not undergone a major eruption within the lifetime of the gas monitoring system. At present, melt inclusion studies 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 magmatic volatile contents (e.g. Stock et al., 2016). The apatite crystal structure can host a range of volatile species that are important for understanding volatile budgets (e.g. F, Cl, OH, C, Br and S). Apatite is more retentive of these elements than silicate melts or glasses, and it can preserve a record of magmatic volatile contents even in volcanic rocks 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).

This project aims to explore the extent to which apatite and melt inclusions preserve similar information about volatile evolution at Pinatubo, Philippines. The explosive eruption of 15th June, 1991 was one of the largest eruptions of the 20th century, but was relatively small in the context of Pinatubo’s eruption history (De Hoog et al., 2004). New state-of-the-art analytical techniques can now be used to carry out in situ analyses of melt inclusions, apatite crystals and crucially, their host phenocrysts. This combination provides an unrivalled opportunity to track the eruption history of volcanoes. Furthermore, Pinatubo shares many compositional characteristics with nearby copper porphyry systems, and it seems likely that understanding the volatile evolution of Pinatubo will ultimately help in understanding the development porphyry deposits more widely.

Pinatubo volcano
Figure 1: 1991 June 15th eruption of Pinatubo volcano.

Host

University of Leicester

Theme

  • Dynamic Earth

Supervisors

Project investigator

Dr Andrew Miles, University of Leicester ([email protected])

Co-investigators

How to apply

Methodology

Samples will be collected from Pinatubo during a planned field season. These samples will supplement an existing collection gathered by the PI and an active researcher at Leicester. 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. Apatite will be analysed in situ from thin section, 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. The major elements, F, S, and Cl of melt inclusions within silicate minerals will be determined by electron microprobe analysis, while other volatiles and trace/rare earth elements will be analysed by SIMS.

Training and skills

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.

You will become proficient in the use of analytical equipment including quantitative evaluation of minerals, SEM and XRF, and high-resolution mass spectrometry. This combination of state-of-the-art analytical methods 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 igneous and applied researchers, and work closely with members of two major NERC-funded projects (FAMOS – From Arc Magmas to Ore Systems, and TeaSe – Te and Se Cycling and Supply), as well as chemists and material scientists within the Centre for Sustainable Resource Extraction.

Partners and collaboration

The student will benefit from supervision at two leading institutions (the Universities of Leicester and Edinburgh). They will also attend the NERC-funded ion microprobe facility at the University of Edinburgh where they will receive full training on the UK’s only SIMS facility available for academic study.

Further details

Please contact Andrew Miles ([email protected]) for further information or to discuss the project in more detail.

If you wish to apply to the project, applications should include:

  • A CV with the names of at least two referees (preferably three and who can comment on your academic abilities)

Applications to be received by Wednesday 31st May 2023.

Possible timeline

Year 1

A thorough review of the latest literature will be conducted. Any fieldwork and sample collection will be conducted in the Philippines. 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 of apatites and melt inclusions. Attend a national conference.

Year 2

Ongoing sample preparation and analysis. Presentation of results at large national and international conference.

Year 3

Integration of data will provide a model for volatile evolution. Publication of papers. Presentation at large national and international conference.

Further reading

  • De Hoog., J.C.M., Hattori, K.H., Hoblitt., R.P., 2004. Oxidised sulphur-rich mafic magma at Mount Pinatubo, Philippines. Contributions to Mineralogy and Petrology, 146: 750-761.
  • 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.
  • Stock, M.J., Humphreys, M.C.S., Smith, V.C., Isaia, R., and Pyle, D.M., 2016, ‘Late-stage volatile saturation as a potential trigger for explosive volcanic eruptions’. Nature Geoscience, 9, 243. 1-2.

COVID-19

This project has a good resilience to any potential disruption caused by a future respiratory and contact infection. In the event of any travel restrictions, samples from Pinatubo are already available at the University of Leicester, were collected during a previous field season. Conferences are likely to move online in such an event and data may be presented remotely.