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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 

Lead Supervisor: Marie Edmonds, Earth Sciences

Co-Supervisors: Owen Weller, Earth Sciences and Rebecca Paisley

This is a confirmed CASE project with Cornish Lithium

Brief summary: 
Lithium, a critical element for the energy transition, is enriched in some evolved igneous rocks - why and how?
Importance of the area of research concerned: 
Lithium is a critical element used in a range of technologies, including solar panels and batteries, and is a vital resource for enabling a low-carbon future. An important primary source of lithium are peraluminous granites enriched in lithium-mica, such as observed in parts of the Cornubian batholith in Cornwall. Key to understanding where and how lithium is enriched in granitic systems is quantifying how it behaves during prolonged magma crystallisation and degassing. We wish to understand how lithium partitions into different mineral phases, such as mica and plagioclase, and also into aqueous fluids that form during crystallisation of magmas. Granitic melts contain volatiles, such as water and the halogens chlorine and fluorine. When the melt exsolves volatiles, fluid-mobile elements like lithium and caesium, partition into it. In continental rhyolites, for example, lithium is often enriched in the rims of magmatic minerals, linked to gas fluxing, modified by diffusion. Combining studies of volcanic and plutonic systems will improve our understanding of lithium enrichment processes and ultimately inform the development of exploration vectors for viable lithium deposits.
Project summary : 
This project will reconstruct the behaviour of lithium in natural igneous rocks using observations and microanalysis in order to fill knowledge gaps which impede the development of genetic models to explain the petrogenesis of lithium-enriched deposits. It will address questions such as: how does the halogen content of a magma, in particular its fluorine content, impact phase equilibria, second boiling and lithium partitioning? Do fluids become enriched in the roof zones of plutons, similar to sub-volcanic magma reservoirs? Why are some granites enriched in lithium and others are not? Cornwall granites provide an ideal natural laboratory for this study as the exposed structural level allows close scrutiny of processing occurring at a critical interface: the roof of plutonic bodies that were once connected to a degassing volcanic system, now eroded away.
What will the student do?: 
Plutonic and volcanic rocks from a range of settings will be examined, including Cornish peraluminous granites (G1-G4), the Kingsand rhyolite, peralkaline rhyolite, and continental metaluminous rhyolite. Observations of elemental and isotopic Li concentrations will be made in minerals, glasses and whole rocks; and a framework of understanding will be constructed to describe how lithium may become enriched in granites and/or rhyolites via fractionation and degassing. Techniques will involve Secondary Ion Mass Spectroscopy (SIMS) at the NERC facility, supplemented by microanalysis using the Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN) and Electron Probe Microanalysis (EPMA) at the University of Cambridge.
References - references should provide further reading about the project: 
Simons B, Andersen JC, Shail RK, Jenner FE. Fractionation of Li, Be, Ga, Nb, Ta, In, Sn, Sb, W and Bi in the peraluminous early permian Variscan granites of the Cornubian Batholith: Precursor processes to magmatic-hydrothermal mineralisation. Lithos. 2017 May 1;278:491-512.
Benson TR, Coble MA, Rytuba JJ, Mahood GA. Lithium enrichment in intracontinental rhyolite magmas leads to Li deposits in caldera basins. Nature communications. 2017 Aug 16;8(1):1-9.
Li J, Huang XL, Wei GJ, Liu Y, Ma JL, Han L, He PL. Lithium isotope fractionation during magmatic differentiation and hydrothermal processes in rare-metal granites. Geochimica et Cosmochimica Acta. 2018 Nov 1;240:64-79.
Applying
You can find out about applying for this project on the Department of Earth Sciences page.
Prof Marie Edmonds
Department of Earth Sciences Graduate Administrator