Current PhD Projects

Sean Whitley

Xenoliths as tracers of magmatic and intra-crustal processes at subduction zone volcanoes

Sean Whitley

Supervisors : Dr Ralf Halama and Dr Ralf Gertisser


Rebecca Wiltshire

Transitions in eruption styles of arc eruptions

Rebecca Wiltshire

Supervisor : Dr Ralf Gertisser and Dr Ralf Halama


Completed PhD Projects

Luke Hepworth - Linking in situ crystallisation and magma replenishment in the Rum layered Intrusion, NW Scotland

Luke Hepworth

Linking in situ crystallisation and magma replenishment in the Rum layered Intrusion, NW Scotland

Adam Jeffery - Petrogenesis and contrasting eruption styles of peralkaline silicic magmas from Terceira and São Miguel, Azores

Adam Jeffery

Petrogenesis and contrasting eruption styles of peralkaline silicic magmas from Terceira and São Miguel, Azores

Supervisors : Dr Ralf Gertisser, Dr Brian O'Driscoll

Map  Explosive eruptions of evolved, silicic magmas are not typically associated with oceanic-island, intraplate settings, where effusive eruptions of basaltic magma dominate. However, many Atlantic islands exhibit ignimbrites, presumably due to the development of shallow magma chambers and the evolution of silicic magmas therein. The Azores archipelago provides one such example, where eruptions of silicic, and commonly peralkaline, magmas have been explosive (forming ignimbrites and pumice falls) and effusive (forming lava domes and flows).

This study aims to investigate the pre- and syn-eruptive processes occurring in the magma systems of the Azores, elucidating the controlling factors in the contrasting eruption styles of silicic magmas in oceanic island settings. Two case studies are utilised; the ignimbrites of Terceira Island and the products of Furnas volcano, São Miguel Island.

Terceira

volcanoes  With a surface area of approximately 382 km2 and a population of 58,000, Terceira is the third largest island in the Azores archipelago. One of the five islands of the central group, it comprises four central volcanoes; Sánta Barbara, Pico Alto, Guilherme Moniz and Cinco Picos.

The island is bisected from NW-SE by a 2 km wide rift zone that cross-cuts Santa Bárbara, Guilherme Moniz and Cinco Picos. The rift is defined by various scoria cones and lava flow vents and is considered to be the surface expression of the large-scale geodynamic feature, the Terceira Rift (Self 1976; Gertisser et al. 2010).

Ignimbrites make up a significant proportion of the islands stratigraphy, attesting to multiple major ignimbrite-forming eruptions during the last 100 ka.

This study focuses upon the seven ignimbrite formations recognised by Self (1976) and Gertisser et al. (2010); the Lajes-Angra Ignimbrite (LAI), the Linhares-Matela Ignimbrite (LMI), the Vila Nova-Fanal Ignimbrite (VFI), the Caldeira-Castelinho Ignimbrite (CCI), the Pedras Negras Ignimbrite, the Groto do Vale Ignimbrite and Ignimbrite-i.

Furnas volcano

Furnas volcano is the youngest of the three active central volcanoes on São Miguel Island, Azores, and is widely considered to be one of the most active and dangerous in the archipelago (Booth et al. 1978; Guest et al. 1999).

Approximately 3,000 people live within the nested caldera, with several thousand more in the immediate vicinity. The volcano’s eruptive history ranges from effusive, dome-forming activity, to at least two explosive, caldera-forming events involving pyroclastic density currents (dated at ~30,000 and ~12,000 y B.P.).

The younger history of Furnas volcano, termed the Upper Furnas Group (UFG) (< 5,000 y B.P.), comprises ten sub-plinian eruptions of uniformly trachytic and often peralkaline material, at least three of which have produced lava domes after initial explosive phases. This study targets the UFG and the older, caldera-forming Povoação Ignimbrite (~30,000 y B.P.)

furnas volcano

Methods:

The aims of this study will be addressed with the following objectives:

  • Geochemical characterisation of the deposits, their crystal cargoes and melt inclusions, followed by thermobarometric determination of pre-eruptive intensive variables
  • Quantitative textural analysis of pumice clasts, evaluation of conduit processes and conduit modelling
  • Geochemical modelling of magma evolution and production of conceptual models for the temporal evolution of the Terceira and Furnas magma systems

Field area

 

Key References:

  • Booth, B., Croasdale, R., Walker, G. P. L. (1978) A Quantitative Study of Five Thousand Years of Volcanism on São Miguel, Azores. Philos. T. R. Soc. Lond. S-A., 288, 271-319
  • Gertisser, R., Self, S., Gaspar, J., Kelley, S., Pimentel, A., Eikenberg, J., Barry, T., Pacheco, J., Queiroz, G., Vespa, M. (2010) Ignimbrite stratigraphy and chronology on Terceira Island, Azores. Geol Soc Am, Special Paper 464
  • Guest, J. E., Gaspar, J.L., Cole, P.D., Queiroz, G., Duncan, A. M., Wallenstein, N., Ferreira, T., Pacheco, J.-M. (1999) Volcanic Geology of Furnas Volcano, São Miguel, Azores. J. Volcanol. Geoth. Res., 92, 1-29
  • Self, S. (1973) Recent Volcanism On Terceira, Azores. Unpublished PhD thesis, Imperial College, London, 250pp

 

Liam Bullock - Structure, emplacement and textural evolution of young obsidian lavas in the Aeolian islands, Italy

Liam Bullock

Structure, emplacement and textural evolution of young obsidian lavas in the Aeolian islands, Italy

Supervisors : Dr Ralf Gertisser, Dr Brian O'Driscoll

Research Area

The emplacement kinematics of silicic lava flows are not well understood, due to a paucity of observations on active flows. The measurement of textural and structural features can serve as an important tracer for silicic lava flow emplacement and deformation.

Silicic volcanism defines recent volcanic activity at the Aeolian Archipelago, Italy. The Rocche Rosse obsidian lava flow represents the youngest outpourings of the Monte Pilato pumice cone on the northern coast of Lipari (Aeolian Islands, Italy).

In my study, structural measurements on surface features and quantitative textural data are coupled with detailed mapping and cross sectional interpretations of the Rocche Rosse obsidian to gain insight into its rheological behaviour and emplacement history.

This will be achieved through meeting the following objectives:

  • Undertake detailed structural investigations of the emplacement mechanisms and post-emplacement deformation of the Rocche Rosse obsidian lava flow on the island of Lipari and the Pietre Cotte lava flow on Vulcano.
  • Full textural and compositional characterisation of spherulite populations in young silicic lava bodies in the Aeolian Islands to identify spherulite heterogeneity and crystallization conditions.
  • Examination and a detailed evaluation of the relationship between spherulite occurrence and flow emplacement and deformation.

Obsidion Meeting these objectives centres on careful and detailed studies of two main study areas – the Rocche Rosse obsidian lava flow (Lipari) and the Pietre Cotte obsidian lava flow (Vulcano), as well as selected young silicic lava bodies across Lipari and Vulcano that exhibit spherulitic textures. The methodologies to address the structural investigations include detailed mapping, and cross section and high resolution satellite imagery interpretations of the Rocche Rosse and Pietre Cotte obsidian lava flows. In order to address the textural characterisation of spherulites, strain analysis, textural observations, crystal-size distribution (CSD), microprobe and Raman spectroscopy methods will be applied in order to create an extensive dataset of individual spherulitic populations.

The detailed textural and structural features documented provide important constraints on the rheological properties of historic obsidian lava flows in the Aeolian Islands, important for understanding the structural kinematics and emplacement mechanisms of young silicic lava flows.

Lizzie Derbyshire - Upper mantle processes, serpentinisation and late-stage alteration preserved in British ophiolites

Lizzie Derbyshire

Upper mantle processes, serpentinisation and late-stage alteration preserved in British ophiolite peridotites and chromitites

Supervisors : Dr Brian O'Driscoll, Dr Ralf Gertisser

In ophiolitic mantle, the robust Cr-spinel crystals in chromitite seams are the only primary mineral which remains relatively unaltered, retaining primary igneous compositions even after extensive serpentinisation alteration. Therefore, the chemical compositions recorded by chromitite are considered to retain primary melt compositions and partial melting extent. Serpentinisation effects are recorded at Cr-spinel crystal edges and along crystal fractures as a Fe-rich (ferritchromit) alteration rims. 

Chromite seam  

Chromitite seam in dunite from Shetland Ophiolite, Unst

The Shetland Ophiolite (Isle of Unst, Shetland) and Ballantrae Ophiolite (Ayrshire) are the focus of this study to understand chromitite formation and the serpentinisation process, in addition to explaining the  complex melt-rock and melt-melt interactions in the upper mantle. The spectacular Shetland and Ballantrae Ophiolites preserve podiform chromitite seams which are currently being investigated by petrographic, mineral chemical and crystal structural analysis.

Katie Preece - Transitions between effusive and explosive activity at Merapi volcano, Indonesia

Katie Preece

Transitions between effusive and explosive activity at Merapi volcano, Indonesia: a volcanological and petrological study of the 2006 and 2010 eruptions.

(University East Anglia; co-supervised by Ralf Gertisser)

Sylvain Charbonnier - The dynamics and hazards of small-volume pyroclastic flows

Sylvain Charbonnier

The dynamics and hazards of small-volume pyroclastic flows: a case study of the 2006 eruption of Merapi volcano, Java, Indonesia

Completed 2010

Supervisor : Dr Ralf Gertisser