Understanding blockages in active geothermal systems: insights from clumped isotopes

Understanding blockages in active geothermal systems: insights from clumped isotopes

Supervisor: Dr John MacDonald (GES, University of Glasgow; john.macdonald.3@glasgow.ac.uk); Professor Bob Holdsworth (University of Durham); Dr Adrian Boyce (SUERC); Dr Sarah Milicich (Geological and Nuclear Sciences, New Zealand)

Description: Maximising the efficiency of low-carbon energy sources is of paramount importance if they are to fill the gap in energy generation as society increasingly moves away from fossil fuels. One such low-carbon energy source is high-enthalpy geothermal which is widely utilised in countries such as Iceland and New Zealand but is increasingly being developed in many other parts of the world such as East Africa. One of the major obstacles in maximising the efficiency of geothermal systems is the precipitation of minerals in fracture networks. Geothermal energy production relies on water circulating through fractures and being heated by warm or hot rocks. Minerals such as calcite can precipitate in these fractures, which over time reduces the efficiency of fluid flow and hence geothermal energy generation. An improved understanding of the geological conditions at which calcite precipitates in active geothermal systems will be invaluable in guiding remediation of this fracture filling and also for investigating the suitability of new sites for future geothermal energy generation.

The main goal of this project is to use ‘clumped’ isotopes to investigate the conditions at which calcite precipitates in fractures in active geothermal systems.

The clumped isotope method has great potential as a proxy for reconstructing past temperatures in a range of geological settings. This method is based on the temperature dependence of bonds between heavy carbon (13C) and oxygen (18O) isotopes in the carbonate mineral lattice. It has successfully been used as a temperature proxy in palaeoclimate studies using the common carbonate mineral calcite but is also attracting increasing interest as a method for determining temperatures of geological processes in the subsurface. There has been limited application of clumped isotopes to determine precipitation temperatures of fracture-filling calcites. There is therefore huge scope for developing clumped isotopes as a proxy for understanding the temperatures of fracture filling in geothermal systems.

Additionally, a key aspect of developing new geothermal resources, and prolonging the life of existing ones, is to understand the fluid reservoirs involved. Fracture-filling minerals such as calcite record such information and clumped isotope analysis also enables reconstruction of fluid δ18O values in addition to temperature. These fluid δ18O values can fingerprint whether the fluids in the geothermal system are meteoric, magmatic/metamorphic, or a combination of both.

This project offers an exciting opportunity for a student to apply the technique to active geothermal systems in New Zealand to better understand the evolution of geothermal systems.

Funding notes: IAPETUS’ postgraduate studentships are tenable for between 3 and 4 years, depending on the doctoral research project the student is studying and provides the following package of financial support:

  • A tax-free maintenance grant set at the UK Research Council’s national rate, which in 2017/18 is £14,553 (pending confirmation).
  • Full payment of their tuition fees at the Home/EU rate; &
  • Access to extensive research support funding.

Part-time award-holders are funded for between six (6) and eight (8) years and receive a maintenance grant at 50% of the full-time rate.

Eligibility: All applicants need to meet NERC’s eligibility criteria to be considered for an IAPETUS studentship and these are detailed in NERC’s current studentship handbook.
IAPETUS is only able to consider applications from Home/European Union candidates. International candidates are not eligible to be considered and where a candidate from another EU country has not been resident in the UK for 3 years or more prior to the commencement of their studies with IAPETUS, they will only be eligible for a fees-only studentship.

IAPETUS is looking for candidates with the following qualities and backgrounds:

  • A first or 2:1 undergraduate degree, or have relevant comparable experience;
  • In addition, candidates may also hold or be completing a Masters degree in their area of proposed study or a related discipline; &
  • An outstanding academic pedigree and research potential, such as evidenced through the publication of articles, participation in academic conferences and other similar activities.

How to Apply: Please refer to the following website for details on how to apply:

Deadline: 19 January 2018

Start Date: All studentships will commence in September/October 2018, except in exceptional circumstances.