Lead supervisor: Marian Holness, Earth Sciences
Co-supervisor: Michael Stock, Trinity College Dublin; Mark Cooper, Geological Survey of Northern Ireland
This is a CASE project with the DfE in Northern Ireland
Brief summary:
This project is focussed on the currently poorly understood physical and chemical behaviour of strongly bimodal magmatic systems using the Slieve Gullion Complex as an exemplar.
Importance of the area of research concerned:
The Daly Gap is an enigmatic feature of many large magmatic systems, in which intermediate compositions are rare or entirely absent: while it is often noted in volcanic deposits, corresponding bimodality occurs in intrusive systems. Suggested causes include liquid immiscibility and variations in temperature-time relationships during fractionation. What has not yet received attention is the physical and chemical behaviour of these strongly bimodal crustal magmatic systems: how much interaction occurs between the two compositional end-members?; how much assimilation of partially melted crust takes place?; what are the implications for the behaviour of magmatic sulphides and the development of economically important mineral deposits including PGEs? These questions will be addressed with a petrological and geochemical examination of the well exposed, bimodal intrusive rocks at Slieve Gullion in Northern Ireland . As Slieve Gullion has received little scientific attention since the mid-20th Century, this project will also represent a major advance in our understanding of the British and Irish Paleogene Igneous Province.
Project summary :
The Slieve Gullion Complex comprises a major centre of Paleogene igneous activity in the southern part of Northern Ireland. It intruded the Caledonian Newry granodiorite, and comprises a ring dyke and a central layered complex with strongly bimodal compositions. Slieve Gullion is situated immediately NW of the contemporaneous Carlingford Complex which has been the subject of recent critical raw material (PGE) exploration. However, the relationships between these two systems, the impact of mafic-felsic interactions on their physico-chemical evolution, and the potential for mineralisation in Slieve Gullion remain poorly understood. This project will use state-of-the-art geochemistry/petrology to produce an understanding of the Slieve Gullion magma system, assessing the dynamics of bimodal magmatic interactions, its economic potential, and genetic relationship with the Carlingford Complex.
What will the student do?:
The student will produce the first modern characterisation of the Slieve Gullion central Complex, using systematic field measurements and sample collection to characterise the magmatic stratigraphy. This includes constraining the number, composition and relative timing of individual magma injections, the extent of interaction between injections, and the identification of economically important sulphide minerals. This will be achieved using textural measurements (e.g. dihedral angles), bulk-rock geochemistry (XRF) and geochemical microanalysis (SEM, EPMA).
Once the magmatic stratigraphy is constrained, the student will focus on investigating the contacts between the basic and felsic components of the neighbouring Slieve Gullion and Carlingford complexes, using field and microstructural analyses to identify different magmatic generations and the relative timing of their emplacement and/or mobilisation. They will constrain the mixing dynamics between these magmas, and how the compositional bimodality impacts the structural and compositional evolution of the magmatic system, before collecting new radiometric dates to quantify the absolute timing of magmatism.
References - references should provide further reading about the project:
Emeleus, C.H., Troll, V.R., Chew, D.M. & Meade, F.C. 2012. Lateral versus vertical emplacement in shallow-level intrusions? the Slieve Gullion Ring-complex revisited. Journal of the Geological Society, London, vol. 169, pp.157-171., DOI: 10.1144/0016-76492011-044
Meade, F.C., Troll, V.R., Ellam, R.M., Freda, C., Font, L., Donaldson, C.H. & Klonowska, I. 2013. Bimodal magmatism produced by progressively inhibited crustal assimilation. Nature Communications, 5:4199., DOI: 10.1038/ncomms5199
Applying
You can find out about applying for this project on the Department of Earth Sciences page.