Luke Hepworth

Biography

I graduated from the University of Portsmouth with First Class Honours in Geology in 2013 and started my PhD at Keele University in the same year, studying Cr-spinel seam petrogenesis in the Rum Layered Intrusion in Scotland with Dr Brian O’Driscoll.

Awards and Achievements

Undergraduate:

2012 – Mineralogical Society Prize (Best 2^nd Year Petrology performance)

2012 – Petroleum Exploration Society of Great Britain Project Sponsorship (Best 2^nd Year mapping project)

2013 – Jeremy Miller Prize (Best 3^rd Year Geoscience project)

Recent:

The Geoff Brown Prize, (Best student poster) - Volcanic and Magmatic Studies Group Annual Meeting, Edinburgh, UK, Jan. 2014.

Funding / Grant

Mineralogical Society of Great Britain and Ireland Postgraduate Bursary: £400

Affiliations

• Geological Society of London: Fellow
• Mineralogical Society of Great Britain and Ireland
• Volcanic and Magmatic Studies Group (VMSG)
• European Microbeam Analysis Society (EMAS)

Research and scholarship

Project:

Linking in situ Crystallisation and Magma Replenishment in the Rum Layered Suite, NW Scotland

Cr-spinel is a common accessory mineral in mafic/ultramafic igneous rocks, such as layered intrusions or mantle rocks exposed in ophiolite complexes. Chromitite (>60 vol.% Cr-spinel) seams are particularly abundant in layered mafic-ultramafic intrusions, where they can form significant deposits of chromium ore, as well major reserves of platinum-group elements (PGE). Although important for economic, as well as purely scientific reasons, the origin of chromitite remains controversial.

The Rum Layered Suite, NW Scotland, is a classic example of an open system layered intrusion that has been studied for over a century. Chromitites hosted in olivine-cumulates occur abundantly throughout the Western and also the Eastern Layered Intrusion. The chromitites are closely associated with harrisite, an unusual form of olivine-cumulate that represents a significant example of in situ crystallisation in layered intrusions.

This observation raises the possibility that the seams also crystallised in situ. The comparatively smaller scale of the Rum Layered Suite compared to other layered mafic-ultramafic intrusions (i.e. the Bushveld Complex, South Africa) presents an intriguing opportunity to investigate and characterise discrete open-system chamber processes such as complex magma replenishment and in situ crystallisation, as well as potential PGE concentration in chromitite-hosted sulphide minerals.

 ‌

The project focus is to investigate the formation of olivine-cumulate hosted chromitite seams and platinum-group element enrichment of associated sulphide phases. The focus of recent work has been to investigate the formation of the Unit 10 peridotite and the abundant chromitite seams therein. Extensive field work will also take place on the poorly studied Western Layered Intrusion, to investigate the magma chamber processes.

Methods employed include:

• Detailed logging and outcrop mapping of the respective peridotite bodies alongside petrographic analysis of Cr-spinel seams and peridotites.
• Major and trace element geochemistry of Cr-spinel and host mineralogy, and characterisation of sulphides and PGMs.
• Textural (Crystal size distribution, Spatial Distribution) analysis of Cr-spinel and crystallographic studies (Electron-backscatter diffraction).
• Isotope geochemistry of cumulus and intercumulus mineralogy.

The above datasets will be combined in order to produce a comprehensive conceptual model of magma chamber processes involved in the petrogenesis of chromitite seams in olivine cumulates and associated platinum enrichment in the Rum Layered Suite.

Conferences

Conference Presentations

• Hepworth, L., O’Driscoll, B., Gertisser, R. & Daly, S. (2014). Linking in situ crystallisation and magma chamber replenishment in the Rum Western Layered Intrusion, NW Scotland. Volcanic and Magmatic Studies Group Annual Meeting, Edinburgh, UK, Jan. 2014. See poster.
• Hepworth, L.N., O’Driscoll, B., Gertisser, R., Emeleus, C.H, 2015. Incremental construction of the Unit 10 peridotite, Rum Eastern Layered Intrusion, NW Scotland. Volcanic and Magmatic Studies Group Annual Meeting, Norwich, UK, Jan. 2015 (Oral presentation)