Further information

Research overview

Geology and resources of SW England, Cornwall and the Isles of Scilly

SW England is a superb natural laboratory that, in common with other basement massifs across western and central Europe, records the development and destruction of the Variscan mountain belt during and after the formation of Pangea. My research addresses regional geological evolution and the associated fundamental processes, i.e. Variscan / post-Variscan tectonics and its influence on, and interactions between, structural geology, sedimentation, magmatism, mineralisation and landscape development (further details via right-hand sidebar).

>YouTube ExeTalks video on the geology and resources of SW England (2021)

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The geological evolution of SW England resulted in an outstanding endowment of natural resources that underpinned a globally significant mining industry for much of the 18th-20th centuries, and world-leading research on 'Hot Dry Rock' geothermal energy in the 1970s-1980s. Kaolinite has been produced from altered granites for almost three centuries and remains a major UK industrial mineral export. Since the mid-2000s there has been a resurgence of exploration interest in the UK's most prospective region for the metals tungsten (W), tin (Sn), copper (Cu), lithium (Li) and for deep geothermal energy. The first 'new' metal mine worked the strategically important Hemerdon W-Sn deposit in Devon between 2015-18 and was reposible for the UK becoming the fourth biggest global tungsten producer in 2017-18. In 2019, the deepest onshore borehole in the UK (UD-1, 5057 m TVD / 5275 MD) was completed as part of the United Downs Deep Geothermal Power Project and Eden Geothermal Limited completed their first deep geothermal well in late 2021 that is, just, the longest in the UK (4867 m TVD / 5277 MD). These are nationally and internationally significant projects.  

The applied research that I undertake addresses how fundamental geological processes and regional geological evolution contribute, both positively and negatively, to these resources and their exploration and production (figure below). I've been involved in collaborative research and knowledge transfer with most of the resource companies who have operated in SW England and have received NERC-funding for both geothermal- and minerals-related research.  

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Current and recent funded research projects

Since 2009 I have generated PI income of £1.15M and my Co-I share of income is £0.14M.

• 2022- NERC, National Environmental Isotope Facility, grant-in-kind for collaborative study with Dr Simon Tapster - A deeper insight into batholith construction and its influence on geothermal heat production - a 4D view from the UD-1 borehole in Cornwall (supporting NERC iCASE PhD of Chris Dalby) 
• 2020-2023 European Regional Development Fund. Deep Digital Cornwall (Co-I). 
• 2020-2022 European Regional Development Fund (Priority Axis 4: Supporting the Shift Towards a Low Carbon Economy in All Sectors). Eden Geothermal (Co-I).
• 2019-22 NERC fourth round highlight topic: Deep subsurface heat as a potential major future energy resource - Geothermal Power Generated from UK Granites (GWatt) (NE/S003886/1, Exeter PI)
• 2018-22 NERC Industrial CASE PhD studentship with GeoScience Limited (industrial supervisor Dr Tony Batchelor) - Geological controls on upper crustal heat flow for deep geothermal energy in Cornwall (NE/R008612/1, Lead Supervisor)
• 2017-18 Satellite Applications Catapult Limited contract research - Space enabled exploration and monitoring of Cornwall lithium resources (PI).
• 2016- NERC Isotope Geosciences Facilities Steering Committee, grant-in-kind for collaborative study with Dr Simon Tapster (NIGL) - Long‐lived structural controls on magma genesis, crustal pathways and fluid traps in the post-orogenic SW England batholith: the key to forming the world‐class Hemerdon tungsten‐tin deposit?
• 2015-16 NERC Innovation Project - Tellus How - An exemplar approach for end-user innovation and follow up of major NERC environmental survey projects (NE/M021777/1, Co-I).
• 2014-18 NERC GW4+ DTP PhD - Advanced Geoscience Modelling of South West England using TELLUS high resolution multivariate data (joint with, and hosted by, the British Geological Survey).
• 2012-14 NERC/TSB Knowledge Transfer Partnership (No. 8750) with Imerys Minerals Ltd - Characterisation of the occurrence of critical metals (Nb/Ta/REE/W) + Sn within china clay operations and evaluation of processing strategies and the viability of extraction as a by-product (PI).
• 2010-12 EU FP7-ENV-2009-1 (Led by Geonardo Ltd., Hungary) - Impact Monitoring of Mineral Resources Exploitation (Co-I).

Collaboration and Knowledge Transfer

The knowledge and understanding associated with a long period of geological research in the region is underpinned by, and further contributes to, collaborative and contract minerals industry research / consultancy and knowledge transfer. Present and past collaborators include: British Geological Survey, Cornish Lithium, Cornish Tin, Cornwall Council, Cornwall Resources, CSM Associates, David Roche Geo Consulting, Eden Geothermal, EGS Energy, Elcon Western, GeoScience, Geothermal Engineering, Helford Geoscience, Imerys Minerals, JSC Altynamas, Menteri Besar Incorporated, Satellite Applications Catapult, Treliver Minerals, Tungsten West, Western United Mines and Wolf Minerals on projects that typically involve regional geology, structural geology, granites, mineralisation and/or mineralogical characterisation and their mineral / geothermal resource implications. The National Trust and The University of Plymouth have been collaborators on coastal landsliding projects.

External links for research outputs

• ResearchGate
• Google Scholar
• ORCiD

 

SW England Devonian

The Devonian System was proposed by Sedgwick and Murchison in 1839 on the basis of the distinctive marine fauna in SW England; 'Devonian' is retained but all its component stages are defined in mainland Europe. Studies of SW England regional geological evolution have been hindered by considerable lithostratigraphical and structural complexity. A 30-year re-mapping programme by the British Geological Survey has demonstrated how the Upper Palaeozoic stratigraphy relates to rifting, passive margin development and subsequent Variscan convergence.

Devonian successions in the Rhenohercynian Zone of SW England

The Devonian successions of SW England record the development, and subsequent closure, of a predominantly marine basin that was either marginal to, or succeeded, the Rheic Ocean (see Variscan Tectonics). The Devonian (and Carboniferous) stratigraphy and geological evolution are very similar to the Rhenohercynian Zone of the Variscan Orogen further east (France, Belgium, Germany) and the South Portuguese Zone. Overviews of Devonian basin development and lithostratigraphy are provided by Leveridge and Shail (2011a) and the broader Upper Palaeozoic tectonic evolution by Shail and Leveridge (2009).

Gramscatho Basin / Lizard Complex (Cornwall)

The Gramscatho Basin and Lizard Complex (see figure above) preserve partial evidence for the distal (highly attenuated + ocean floor) segment of the SW England Rhenohercynian passive margin. They also record convergent margin sedimentation, magmatism and metamorphism during the closure of this basin during (or possibly after) Rheic Ocean closure (Leveridge and Shail (2011b). Aspects of the lithostratigraphy of the Gramscatho and Looe basins on the north coast of Cornwall are described by Shail (1989) and Hollick et al. (2006). A view on the internal organisation of tectonostratigraphical units within the Lizard Complex is presented by Power et al. (1996)

Looe Basin felsic magmatism

Early Devonian syn-rift felsic magmatism is relatively rare but well known from the eastern Looe Basin in Devon. Penfound-Marks and Shail (2016) provide details of previously undescribed Early Devonian felsic igneous rocks, that they termed the Hoblyn’s Cove Felsite, that crop out in the structurally complex coastal section through the Start-Perranporth Zone between Ligger Point and Holywell Bay in Cornwall.

Lithogeochemistry of Devonian successions

A preliminary assessment of the baseline whole rock lithogeochemistry of Devonian successions in Cornwall, in areas remote from mineralisation, is provided by Scott et al. (2003).  

SW England Variscan tectonics

The Rhenohercynian / Rheic suture, that runs through the English Channel and Western Approaches, and lies immediately offshore of Cornwall, records the last occasion that British continental lithosphere formed part of a convergent plate margin. The suture forms the boundary between the Rhenohercynian and Saxothuringian zones of the Variscan orogen.

Plate tectonic models

There is no single widely accepted plate tectonic model for the Variscan evolution of this part of western Europe. Some of the admissible possibilities and some of the problems, based on data from SW England and adjacent areas, are outlined in Shail and Leveridge (2009). The Devonian and Carboniferous geology of SW England records the development and subsequent closure of either a: (1) marginal basin immediately north of the Rheic Ocean or (2) successor basin to the Rheic Ocean. Earlier work on the application of sediment provenance models to the tectonic environment of Rhenohercynian sedimentary rocks in Cornwall and Germany is presented in Floyd et al. (1991) and Floyd et al (1990). One of the challenges in tectonic reconstructions is that the nature of pre-Devonian basement in SW England is very poorly constrained. Indirect evidence suggests that it shares some characteristics with the Meguma Terrane in Maritime Canada (Nance et al., 2015). A recent appraisal of the tectonic significance of the suture south of SW England has been provided by Alexander et al. (2019) - see below.  

 

 

 

 

 

 

 

Variscan convergence in SW England

The proximal parts of the northern passive margin (Looe Basin northwards - see Devonian Stratigraphy) are represented by the infill of half / full graben formed by moderate thinning of continental lithosphere; these basins were subsequently strongly inverted during Variscan continental collision. The distal parts of the passive margin (partially accreted together with proximal syn-convergence sediments) are represented by the Gramscatho Basin / Start Complex / Lizard Complex - see below. The distal and proximal segments were juxtaposed along the Start-Perranporth Zone - a major D2 thrust zone; a substantive part of the intervening passive margin may have been occluded. Syn-convergence sedimentation in the later Carboniferous occurs within the Culm Basin and is primarily related to uplift along the frontal segment of the Bristol Channel - Bray Fault as SW England approached and docked with the remainder of southern Britain. Variscan thrust-related covergence had ceased in SW England by c. 305 Ma (late Carboniferous) and briefly replaced by a strike-slip regime before the onset of post-Variscan extension. Descriptions of outcrop-scale structures related to Variscan convergence are provided by Alexander and Shail (1995), Alexander and Shail (1996), Shail and Leveridge, 2009, Hughes et al. (2009) and Alexander et al. (2019). A preliminary evaluation of lineaments across SW England, using Object-Based Image Analysis, which in part reflects the convergence history, has been presented by Yeomans et al. (2018).

SW England post-Variscan tectonics

Variscan convergence ended in the late Carboniferous (c. 305 Ma). It was succeeded across NW Europe by a dextral transtensional regime that persisted through most of the Early Permian. Its effects in SW England were primarily manifested in the extensional reactivation of the Rheic-Rhenohercynian suture, Bristol Channel-Bray Fault and other Variscan thrust faults, and by the strike-slip reactivation of NW-SE Variscan transfer faults. The evidence for reactivation of the offshore Rheic-Rhenohercynian suture zone is summarised by Alexander et al. (2019). 

Onshore evidence for latest Carboniferous - Early Permian post-Variscan extension

During this latest Carboniferous - Early Permian extensional episode, a wide variety of regional D3 structures (folds, foliations, faults, shear zones), typically associated with a top-sense-of-shear to the SSE, were developed in Devonian / Carboniferous rocks and the earliest (>289 Ma) Cornubian granites. Descriptions of these structures, their kinematics, position in the regional deformation chronology and timing relative to granite generation and emplacement, are presented in Alexander and Shail (1995), Alexander and Shail (1996) and Hughes et al. (2009). A preliminary evaluation of lineaments across SW England, using Object-Based Image Analysis, which in part reflects the post-convergence history, has been presented by Yeomans et al. (2018).

 

 

Consequences of extension for magmatism and sedimentary basin development

The extension brought about lithospheric thinning that resulted in the generation and emplacement of lamprophyres, basalts and granites, and the development of 'red-bed' sedimentary basins (Shail and Wilkinson, 1994; Shail et al. 2003; Shail and Leveridge, 2009; Dupuis et al. 2015; Dupuis et al. 2016; Simons et al. 2016). The relationship between extensional reactivation of the Rhenohercynian-Rheic suture and Early Permian development of Plymouth Bay Basin is addressed by Harvey et al. (1994) and Alexander et al. (2019). The kinematics and palaeostress analyses of both D3 and post-D3 structures, developed during the latest Carboniferous to late-Triassic are summarised in Shail and Alexander (1997).

SW England granites

Cornubian Batholith and associated igneous rocks (Early Permian)

The Early Permian igneous rocks of SW England and the adjacent continental shelf form one of the major igneous provinces in the UK. The best known expression of felsic magmatism is the Cornubian Batholith, comprising composite granite plutons, stretching eastwards from beyond the Isles of Scilly, through Cornwall, to Dartmoor in Devon. It is associated with subtantial rhyolite / microgranite intrusive sheets ('elvans') and the remnants of formerly more extensive rhyolite lavas and pyroclastic rocks. The smaller and separate Haig Fras Batholith crops out on the sea floor almost 100 km NW of the Isles of Scilly.

Two-mica (G1) and muscovite (G2) granites

The batholith was constructed over almost 20 Ma during the Early Permian. The most recent classification of near-surface granites by Simons et al. (2016) defines five principal types (G1-G5). The earliest expression of magmatism are the two-mica (G1) and muscovite (G2) granites, represented by the upper parts of the Isles of Scilly, Carnmenellis and Bodmin Moor plutons, and associated dykes and lavas (292-290 Ma). There was a brief hiatus in magmatism from 289-286 Ma and the initial expression of the second stage of emplacement are two-mica (G2) stocks, e.g. Cligga Head (<286 Ma). 

 

 

 

 

 

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Biotite (G3), tourmaline (G4) and topaz (G5) granites

The latter magmatic epsiode is primarily represented by the biotite (G3) and tourmaline (G4) granites that form the dominant near-surface expression of the Land's End, St Austell and Dartmoor plutons. The tourmaline (G4) granites formed by differentiation of the biotite granite magmas and are likely precursors to magmatic-hydrothermal mineralisation. Topaz (G5) granites have a limited near-surface expression, primarily in the Tregonning and St Austell plutons and the Meldon Aplite and have the highest lithium contents within the batholith. 

 

 

 

 

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Contemporaneous mafic igneous rocks

Less well known are the mafic igneous rocks that occur: (1) around Exeter, at or near the base of Permian post-Variscan sedimentary successions (lamprophyre and basalt lavas / sills), (2) in the pre-Permian Variscan basement further west (lamprophyre dykes), and (3) within the Permian post-Variscan sedimentary basins of the western English Channel and SW Approaches.

Tectonic controls on magmatism and mineralisation

Magmas were generated episodically over a 20 Ma period from c. 292 to 274 Ma, primarily by extensional thinning of continental lithosphere previously thickened during Variscan convergence. Mafic igneous rocks resulted from mantle partial melting and felsic igneous rocks largely by partial melting of the lower crust, albeit strongly influenced by underplating / emplacement of mantle-derived melts. Felsic magmatism was restricted to relatively narrow zones in the immediate lower plate / footwall of the Rhenohercynian / Rheic suture (generating the Cornubian Batholith) and the frontal segment of the Bristol Channel Fault Zone (generating the Haig Fras Batholith). The thermal evolution of the lithosphere and onset of partial melting was controlled by superposition of post-Variscan extension and Variscan convergence.

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Work undertaken with others includes recognition of the role of extensional tectonics and mantle melting in lamprophyre and granite generation within the province (Shail and Wilkinson, 1994; Shail et al., 2003; Dupuis et al., 2015; Dupuis et al., 2016; Simons et al., 2016), characterisation of composite granite plutons (Powell et al., 1999; Salmon and Shail, 1999; Simons et al., 2016) and aplite-pegmatite sheets (Breiter et al., 2018), magmatic state fabric development (Kratinová et al., 2003; Kratinová et al., 2010), contact aureole tectonics and emplacement (Hughes et al., 2009; Pownall et al., 2012), characterisation of zircon chemistry (Breiter et al., 2016) and LA-ICPMS zircon dating (Neace et al., 2016).

The Lundy Granite (Palaeogene) . . . and now for something completely different . . . or is it?

The Lundy Granite, located in the Bristol Channel off the north Devon coast, forms part of the Lundy Igneous Complex, and is the southernmost substantive expression of magmatism within the British-Irish Palaeogene Igneous Province and the wider North Atlantic Igneous Province. Charles et al. (2017) provided the first U-Pb zircon ages for the granite and confirmed a Palaeocene age (59.8 ± 0.4 – 58.4 ± 0.4 Ma). Its Qz + Pl + Kfs + Bt ± Grt ± Tpz mineralogy and peraluminous character contrasts with similar age granites farther north but are similar to the granites of the Early Permian Cornubian Batholith.

The anomalous southerly location of the Lundy Igneous Complex is probably a consequence of mantle melting arising from the superimposition of localised lithospheric extension, related to intraplate strike-slip tectonics, with the distal ancestral Icelandic plume. Granite generation primarily reflects crustal partial melting during the emplacement of mantle-derived melts. The peraluminous character indicates a fundamental crustal source control between contrasting peri-Gondwanan (Lundy) and Laurentian basement provinces farther north.

 

SW England mineralisation

Distinct episodes and styles of mineralisation reflect the regional tectonic evolution of SW England (view 'metals + rocks' row in table).

Syn-rift mineralisation (Early Devonian - Early Carboniferous)

Devonian and Early Carboniferous syn-rift successions locally host low grade / tonnage SedEx and VMS mineralisation styles that subsequently underwent Variscan deformation and low-grade regional metamorphism; some was locally remobilised within . . .  

Late-orogenic mineralisation (Latest Carboniferous - ?earliest Permian)

Late-orogenic shear zone quartz-Sb-Au + base metal veins associated with late Variscan (latest Carboniferous-?earliest Permian) NW-SE strike-slip transfer faults, active during thrusting and early extensional recativation, are best known from North Cornwall but occur more widely (e.g. Camm et al., 1996), such as within the 'killas' in the Dolcoath section of South Crofty Mine, and typically have grades of up to 1-2 ppm Au over 0.2-0.3 m intersections.

Granite-related mineralisation (Early - Mid Permian)

Of overwhelming historical, and continuing present / future, economic significance are the Early-Mid Permian magmatic-hydrothermal W-Sn-Cu-Zn-Pb vein deposits associated with the Cornubian Batholith. The role of partial melting and fractional crystallisation in controlling variable melt enrichment in Li, Be, Ga, Nb, Ta, In, Sn, Sb, W and Bi across the different Cornubian granite suites (G1-G5) was modelled by Simons et al. (2017); Sn and B distributions were modelled by Williamson et al. (2010).

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Emplacement of these variable composition magma batches during pluton construction was associated with the release of enormous volumes of magmatic-hydrothermal fluids. These migrated through actively propagating, tectonically-controlled, extensional / strike-slip fault and joint systems and mixed to varying degrees with meteoric and other fluids (contact metamorphic / red-bed brines).

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The resulting mineralisation occurs both in the granites and their host rocks and may include multiple parageneses in zones of repeated fluid mixing. Quartz tourmaline cassiterite parageneses from the largely unmineralised southern lobe of the Land's End Granite are described by LeBoutillier et al. (2002). Polymetallic quartz-chlorite-sulphide-fluorite metasedimentary rock hosted assemblages from near surface in South Crofty Mine have been described by LeBoutillier et al. (2000) and across the province by LeBoutillier et al. (2003).

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The occurrence of a mantle helium signature in most magmatic-hydrothermal parageneses was outlined by Shail et al. (2003). A comprehensive description of indium mineralisation across SW England was provided by Andersen et al. (2016). Preliminary reports of the geological factors that influenced the formation of the world-class Hemerdon W-Sn deposit, being worked by Wolf Minerals, have been provided by Shail et al. (2017) and Tapster et al. (2017).

Cross-course mineralisation (Mid-Triassic)

Mid-Triassic 'cross-course' mineralisation, related to the migration of 'red-bed' basinal brines through granites and their host rocks, also occurs within the mafic/ultramafic rocks of the Lizard Complex (Power et al., 1997). A record of mining wastes within the contemporary sediments of the River Teign, largely related to cross-course mineralisation, is described by Simons et al. (2011).

Structural controls on mineralisation

The variable orientation of veins hosting granite-related magmatic hydrothermal mineralisation and basinal-brine cross-course mineralisation is partially explained by changing regional and local palaeostress regimes during the latest Carboniferous-late Triassic (Shail and Wilkinson, 1994; Alexander and Shail, 1995; Alexander and Shail, 1996; Shail and Alexander, 1997); see figure below. A preliminary evaluation of lineaments across SW England, using Object-Based Image Analysis, has been presented by Yeomans et al. (2018).

 

 

 

 

 

 

Estuary sediments

A record of granite-related and cross-course mineralisation, as well as china clay extraction, is preserved in estuary sediments around SW England; there are also some really interesting diagenetic minerals. A concise readable overview is provided by Pirrie and Shail (2018).

SW England geothermal

Overview

Cornwall and Devon have locally high surface heat flows associated with elevated levels of U, Th and K within the granites of the Cornubian Batholith. It is the most prospective area in the UK for the development of deep geothermal energy (Beamish and Busby 2016). Previous investigations include the £42M CSM Hot Dry Rock research programme (1973-1991), based at Rosemanowes Quarry in the Carnmenellis Granite, where several deep research boreholes were drilled to a maximum depth of 2600 m.

There has been a renewed impetus over the last decade to ensure that the regional potential for deep geothermal power is further investigated and developed; this forms one of the strategic priorities for Cornwall Council.

>Could Cornish granite unlock deep geothermal energy in England? 
Online article and interview in Power Technology (May 2019)

United Downs Deep Geothermal Power Project (St Day - Carn Marth Granite)

The United Downs Deep Geothermal Power (UDDGP) Project, run by Geothermal Engineering Limited, targetted a granite-hosted segment of the Porthtowan Fault Zone and is developing a 1-3 MW pilot power plant.

Drilling of the 5058 m (TVD) UD-1 production well, which is the UK's deepest onshore borehole, commenced on 7th November 2018 and was completed on 23rd April 2019. The 2214 m (TVD) UD-2 injection well was completed on 28th June 2019. An extended testing programme is currently taking place, before construction of the power plant.

The rationale and science behind the project are explained in this brilliant video. A summary of site selection and an initial assessment of the structurally-controlled reservoir from downhole data has been provided by Reinecker et al. (2021). 

Eden Geothermal Project (Bodelva - St Austell Granite)

Eden Geothermal Ltd has been set up by three partners: Eden Project, EGS Energy Ltd, and Bestec (UK) Ltd. The initial drill site is located to the north of the Eden Project biomes, in the southern part of the St Austell Granite, and has targetted the NNW-SSE "Great Cross-course" fault system.

Drilling of the first well, EG-1 (MD 5277 m BGL; TVD 4867 m BGL), commenced on 17th May 2021 and maximum depth was reached on 26th October 2021. It is presently (just!) the longest geothermal well in the UK. 

The Project will include a one-year period of heat production from the single deep well, using a ‘co-axial’ circulation system, that will be used to provide direct heat to existing facilities at Eden and to new greenhouses. This will be the first phase of an anticipated two well development. It will pave the way for the second phase and another deep well and an electricity plant.

The project is summarised here. 

My research related to deep geothermal energy

The geological uncertainties related to the development of deep geothermal largely relate to understanding regional to local variations in crustal heat flow and fracture permeability. These are closely aligned with my research interests in SW England granites, SW England mineralisation and post-Variscan tectonics. The geology-related deep geothermal research projects that I’m involved in are summarised below:
 

Eden Geothermal 

Exeter PI: Professor Hylke Glass; Exeter Co-I: Dr Robin Shail;

PhD title: Geological controls on heat production and the evolution of fracture systems. 

PhD student: Philip Henes

Supervisory team: Dr Robin Shail (lead), Professor Hylke Glass

The research will use data derived from well-cuttings and downhole geophysical logging to evaluate the geological controls on heat production and fluid flow in the vicinity of the test site. These data will help address how the distribution of heat-generating elements, U, Th, K, varies with depth and so contributes to the heat resource and geothermal gradient. Downhole geophysical logs will be used to determine the orientation, aperture, spacing, distribution and other characteristics of the fracture and vein populations. These are the primary controls on permeability and fluid flow. The vein systems reflect multiple episodes of fracture formation / reactivation and fluid flow - they are, in essence, markers of palaeo-geothermal systems. The nature of vein infills is strongly correlated with wall-rock alteration / strength of the host granite; this, together with re-fracturing and/or dissolution of vein infill exerts an important control on permeability and, potentially, the chemistry of contemporary fluids. The objective is to understand the extent to which multiple generations of fluid flow have contributed to: (1) enhancement, and (2) reduction of permeability. 

A second PhD project "Estimation of the geothermal resource" is being undertaken by Ben Adams and is supervised by Professor Hylke Glass (lead) and Dr Robin Shail. 

Funding: European Regional Development Fund + College of Engineering Mathematics and Physical Sciences

Geothermal Power Generated from UK Granites (GWatt)

NERC fourth round highlight topic (2019-2022): Deep subsurface heat as a potential major future energy resource (NE/S003886/1)

Exeter PI: Dr Robin Shail; Exeter Co-I: Dr Matthew Eyre

Research Fellow: Chris Yeomans

Exploitation of UK deep geothermal resources has been held back by knowledge gaps relating to permeability and fluid/heat flow at reservoir target depths of 3-5 km; the risks associated with these uncertainties have inhibited private investment. Geothermal Power Generated from UK Granites (GWatt) seeks to reduce these risks, and so contribute to the uptake of deep geothermal energy, by:

• Increasing knowledge of the geological conditions needed for deep fracture-controlled fluid flow within granitic rocks.
• Developing a quantitative understanding of the heat resource and sustainability of the geothermal reservoir.
• Constructing robust geological risk assessments based on well-established oil and gas uncertainty quantification and optimisation methods, with a view to reducing perceived risks.
• Applying the integrated results of site-specific research to new geothermal exploration models for other granites, particularly those in SW England.

The project consortium includes research, business and local government partners. Research collaboration between GWatt and the United Downs Deep Geothermal Power (UDDGP) Project will provide access to a unique resource of downhole fluids, rock samples, geophysical logs, flow data and seismic data. In addition to CSM, the project comprises the British Geological Survey (project co-ordinator) and Heriot-Watt University who provide complementary skills in deep geothermal resource assessments, deep fracture fluid flow, rock/fluid interactions, reservoir modelling and the quantification of geological uncertainties.

Funding: UKRI-NERC
 

Geological controls on upper crustal heat flow in Cornwall

NERC Industrial CASE PhD studentship with GeoScience Limited (2018-2022) "Geological controls on upper crustal heat flow for deep geothermal energy in Cornwall" (NE/R008612/1)

PhD student: Chris Dalby
Supervisory team: Dr Robin Shail, Dr Tony Batchelor (GeoScience Limited), Professor Frances Wall, Dr James Hickey

The purpose of the project is to address uncertainties regarding heat production and conduction models in the Cornish crust which include: (i) radioactive elements U, Th and K are not present in sufficiently high quantities within the previously investigated upper parts of the granite to account for observed heat flow, (ii) He-4 production from historical deep geothermal wells is higher than anticipated, (iii) geophysical modelling has progressively reduced the interpreted volume of the Cornubian granites. These inconsistences imply substantive heat source(s) may occur within, or below, the deeper parts of the batholith.

Drilling cuttings from the UDDGP Project will be used to evaluate mineralogical and geochemical changes in depth within the granite to evaluate heat production. These data will be complemented by those obtained during downhole logging. Comparisons between modelled heat production and measured heat flow data will be evaluated in terms of the potential role of upper crustal convective fluid flow and/or mid / lower crustal and mantle heat contributions (using existing deep geophysical data and an understanding of admissible scenarios during the post-Variscan tectonic evolution of SW England).

Funding: UKRI-NERC + GeoScience Limited

Teaching

I am Module Co-ordinator (MC) for Dynamic Planet (Year 1) and Structural Geology and Tectonics (Year 2). I contribute to several other undergraduate modules, primarily field-based skills teaching, and supervise Summer Vacation Projects. I also teach on the MSc Mining / Exploration Geology programme and supervise Research Project and Dissertation students - typically those with a SW England resources and/or structural geology focus.

• Year 1
  + Dynamic Planet (CSM1042) MC
  + Field Geology and Geological Maps (CSM1036)

• Year 2
  + Structural Geology and Tectonics (CSM2182) MC
  + Geological Mapping Techniques (CSM2184)
   
• Year 3
  + Exploration Techniques (Underground Geological Mapping) (CSM3151)
  + Summer Vacation Project (CSM3379)
   
• MSc
  + Ore Deposit Geology (CSMM195)
  + Research Project and Dissertation (CSMM047)

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