Unlocking Cornwall's Geothermal-Lithium Resources: Fault Reactivation, Fluid Flow and Permeability Evolution Through Time

Monaghan et al., 2025). Despite growing investment and recent advances in geothermal development, the geological controls on reservoir permeability remain poorly understood, limiting exploration and resource development. This PhD project, which has been co-designed with industry partner Cornish Lithium, will investigate how faulting, fracturing and fluid flow have evolved in SW England since the end of the Carboniferous-Permian Variscan mountain-building event. While the Variscan evolution of Cornwall is relatively well constrained (e.g. Shail and Leveridge, 2009), the subsequent tectonic history remains poorly understood despite emerging evidence that post-Variscan fault reactivation (e.g. Shail and Alexander, 1997) played a critical role in generating the fracture networks that control modern geothermal fluid circulation.

Project highlights:

• Work with Cornish Lithium, a pioneering company extracting lithium from both hard-rock deposits and geothermal waters in Cornwall. Undertake fieldwork across Cornwall and Devon and analyse drill core from active exploration projects.
• Gain first-hand industry experience through a placement with Cornish Lithium, developing practical skills and professional networks within the rapidly growing geothermal and critical minerals sectors.
• Access world-class analytical facilities at the University of Portsmouth, applying cutting-edge laser ablation mass spectrometry and electron microscopy techniques to investigate the timing of faulting and sources fluid flow.
• Develop highly sought-after skills at the intersection of renewable energy and critical mineral exploration, contributing to research that will help advance sustainable geothermal-lithium resources for the energy transition.

Aim:

This project aims to determine how faulting, fracturing and fluid flow-mediated mineralisation have controlled the evolution of permeability through time, and influenced the size, distribution, and dynamics of the modern geothermal-lithium reservoir.

The project will involve fieldwork in Cornwall and Devon with industry professionals and regional geology experts, work experience in the geothermal-critical metal industry with Cornish Lithium, and access cutting-edge laboratory facilities at the University of Portsmouth. There will also be opportunities to present research findings at international conferences, contribute to peer-reviewed journal publications, and engage with industry stakeholders throughout the project.

Building on recent advances in fault-dating methods (e.g. Mottram et al., 2020; Connolly et al., 2024), this project will use U-Pb carbonate geochronology alongside structural and geochemical analyses to determine the timing of fault formation and reactivation to evaluate permeability creation and destruction processes. These results will establish the principal controls on modern geothermal fluid circulation. Integrating with the ongoing exploration activities of Cornish Lithium, the project will focus on major regional structures, mineralised fault-parallel veins (Lodes), Cross-course faults, and their associated younger fracture networks, which have been newly identified through project pilot studies. Field observations will be combined with drill core provided by Cornish Lithium to tie surface datasets and analysis to comparative observations made at reservoir depths.

Objectives:

1. In collaboration with Cornish Lithium, conduct targeted geological fieldwork in SW England to characterize the orientations, kinematics, infill and relative chronology of fault and fracture populations using both field and core samples;
2. Use advanced microscopy and in-situ geochemical techniques to describe the mineral infill and textures associated with these populations and infer fluid paragenesis;
3. Apply novel geochronology methods such as U-Pb carbonate and fluorite dating to track the timing of faulting and fluid flow;
4. Investigate fluid inclusions and stable isotopes to track fluid sources; (5) Provide highly specialized, societally-urgent skills in the renewable energy sector.

Outcomes:

This project will provide you with world-class training in structural geology, geochronology, geochemistry and its application to geothermal energy research, offering close collaboration with industry partners and access to unique datasets, including drill core and hydrogeological test work collected from active geothermal developments. The research will deliver the first comprehensive temporal framework for post-Variscan fault reactivation and permeability evolution in SW England, providing a step-change in understanding how fault networks control geothermal fluid flow and lithium-bearing brines. The project will establish a regional tectonic and hydrothermal framework for Cornwall's emerging geothermal province and generate transferable insights into fault-controlled geothermal systems worldwide, supporting energy security, critical mineral supply and the transition to net zero. The results generated will underpin improved exploration models and aid in the development of novel approaches to reservoir modelling and resource estimation, establishing a criteria whereby the most permeable structures can be efficiently targeted and project risks significantly reduced.

Applicant requirements:

• We are looking for a student with a geological background; applicants should hold an Undergraduate (Hons)/ Masters degree in Geology/Geoscience/ Earth Science.
• We are looking for candidates with an interest in field structural geology, geochronology, geochemistry, and their application to critical mineral and geothermal systems. No prior analytical laboratory experience is required and full training will be provided, but previous experience would be desirable.
• Excellent written and verbal skills in English are essential.

Supervisors:

• Dr. Catherine Mottram
• Dr. Will McKenzie
• Dr. Robin Shail
• Dr. Alex Hudson

Funding Notes:

Fully funded place including home (UK) tuition fees and a tax-free stipend at UKRI rates. Additional funding to cover full overseas fees is available for a maximum of 6 studentships.

Enquiries email name and address:

TREES.Admissions@ucl.ac.uk

Application Web Page:

https://www.trees-dla.ac.uk/apply

References

Connolly, J., et al., (2024). Using U–Pb carbonate dating to constrain the timing of extension and fault reactivation... J.Geological Society, 181(5), jgs2024-021.

Monaghan, A et al., (2025) Geothermal Energy Use, Country Update for the United Kingdom. In: Shaping the Future: European Geothermal Congress.

Mottram, C. M., et al., (2020). Syncing fault rock clocks: Direct comparison of U-Pb carbonate and K-Ar illite fault dating methods. Geology, 48(12), 1179-1183.

Shail, R. K., & Alexander, A. C. (1997). Late Carboniferous to Triassic reactivation of Variscan basement in the western English Channel… J.Geological Society, 154, 163.

Shail, R. K., & Leveridge, B. E. (2009). The Rhenohercynian passive margin of SW England… Comptes Rendus. Géoscience, 341(2-3), 140-155.

Shaw, R. (2022) The potential for lithium in the UK. British Geological Survey, 8pp. (Minerals for the UK's Net Zero Transition, CR/22/123N)

Szanyi, J., et al., (2023). Geothermal energy and its potential for critical metal extraction—a review. Energies, 16(20), p.7168.