2026-L08 Tracking volatiles in explosive alkaline eruptions

PROJECT HIGHLIGHTS

  • Gain a unique petrological perspective by studying the interior of an active volcano. 
  • Advance understanding of a key control on volcanic eruptions and associated hazards with relevance to hydrothermal ore deposits. 
  • Build expertise in diverse field and laboratory techniques to trace the evolution of volatile elements in volcanic systems. 

Overview

Volatiles such as H₂O, CO₂, S, F, and Cl are fundamental components of magmas, inherited from their source regions and play a critical role in a number of magmatic processes. Their solubility in magmas fluctuates during magma ascent due to variations in pressure and temperature, leading to volatile saturation. This saturation triggers the exsolution of fluids and the formation of bubbles, significantly altering a magma’s physical properties, including viscosity. These changes can, in some instances, remobilise stagnant, crystal-rich mushes, trigger explosive volcanic eruptions and lead to the formation of hydrothermal mineral deposits. 

Beyond eruption and magma dynamics, volatiles also influence the characteristics of volcanic deposits. Ignimbrites, deposits formed by pyroclastic density currents (PDCs), can either remain unconsolidated or weld during deposition, with the volatile content of the magma playing a potential role in this distinction. Understanding volatile evolution from deep-seated magma mushes to surface deposits is therefore crucial for assessing the most hazardous components of explosive volcanism. 

Current state-of-the-art techniques for reconstructing pre-eruptive volatile contents primarily rely on melt inclusion studies. However, these inclusions are susceptible to post-entrapment modifications, which can reset or alter volatile records over timescales of hours to years (e.g., Hartley et al., 2014). Recent research has identified the mineral apatite as a more resilient alternative proxy for tracking magmatic volatiles (e.g., Stock et al. 2016; Stonadge et al., 2023). Apatite’s crystal structure can incorporate a variety of volatile species, retaining a more complete record of magmatic volatile contents even when the surrounding glass is degassed. Additionally, apatite can host trace and redox-sensitive elements, providing insights into pre-eruptive magma storage conditions (Miles et al., 2013). However, the small grain size of apatite often limits detailed analysis of its volatile record. 

In contrast, haüyne, a rare but frequently large S-rich mineral found in highly Si-undersaturated magmas, has been comparatively underutilised as a monitor of volatile evolution and excess degassing. The mineral’s size offers a unique opportunity for detailed chemical and textural analysis. Preliminary studies suggest that haüyne’s textural varieties may reflect volatile sparging episodes during magma accumulation (Cooper et al., 2015). 

This project is the first to propose an integrated approach using both apatite and haüyne to create a detailed, complementary record of volatile evolution leading up to a Plinian eruption. The study will focus on the 668 ka Arico ignimbrite, a rare welded ignimbrite deposit formed by the eruption of the Las Cañadas volcano, Tenerife. Cutting-edge analytical techniques (SEM, EPMA, LA-ICP-MS, and SIMS) will be employed for in situ textural and chemical analyses of these two crystal types. This combined methodology offers an unprecedented opportunity to trace the processes leading up to one of the most significant eruptions of the Las Cañadas volcano, while exploring the factors responsible for the welding of pyroclastic density current deposits. 

The broader implications of this study extend beyond magmatic evolution. Understanding how volatiles behave in magmas not only sheds light on eruption dynamics but also offers insights into the formation of hydrothermal ore deposits, which are often associated with volatile-rich volcanic centres. In a wider societal context, this knowledge also supports more accurate volcanic hazard forecasting, helping to protect communities living in volcanically active regions, and informs sustainable approaches to securing critical raw materials formed by hydrothermal processes. 

Figure: Teide – a recent stratovolcano situation within the significantly larger Las Cañadas caldera – the source of a number of Plinian-sized eruptions to have occurred on Tenerife, including the Arico eruption. 

Sunset landscape with a snow-capped mountain on the left, rugged terrain, and sparse vegetation. The sky fades from warm orange near the horizon to pale blue above, creating a peaceful scene.

Case funding

This project is not suitable for CASE funding

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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’ Mineralogic 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 subject to a successful outcome of a funding application to use the facility.  

DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.  

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.  

Year 1: 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. 

 

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. 

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. 

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 

Stonadge, G., Miles, A.J., Smith, D.J., Large, S., Knott, T, 2023. The volatile record of volcanic apatite and its implications for the formation of porphyry copper deposits. Geology, 51, 1158-1162. 

Further details and How to Apply

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

To apply to this project: 

  • 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: CENTA PhD Studentships | Postgraduate research | University of Leicester.  Please scroll to the bottom of the page and click on the “Apply Now” button.  The “How to apply” tab at the bottom of the page gives instructions on how to submit your completed CENTA Studentship Application Form 2026 your CV and your other supporting documents to your University of Leicester application. Please quote 2026-L08when completing the application form.  

 Applications must be submitted by 23:59 GMT on Wednesday 7th January 2026. 

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