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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 

Lead Supervisor:  Marie Edmonds, Earth Sciences 

Co-Supervisor: David Neave, University of Manchester and Madeleine Humphreys, Durham University

Importance of the area of research concerned: 
Lithium is a critical resource for the development of Li-ion batteries, in the quest for improved methods for storing energy. An important source of lithium is pegmatite deposits, which are late-stage, highly evolved crystalline products of the fractionation of water-rich continental magmas. However, we still have only a limited understanding of how lithium behaves in magmas. Specifically we wish to understand how lithium concentrations in magmas depend on mantle source, slab and crustal components; how lithium partitions into aqueous fluids during magma degassing, and how lithium partitions between melt and crystal phases. It has been shown recently that continental magmas may be particularly enriched in lithium (ref); and that lithium is often enriched in the rims of magmatic minerals (e.g. plagioclase), which has been variously linked to gas fluxing and fluid phase boiling and separation of a brine. Lithium diffuses extraordinarily fast, so these enrichments are also useful ‘speedometers’ of volcanic processes. It seems clear that vast holes in our knowledge about magmatic lithium remain, which prevent a full understanding of the provenance of lithium in hydrothermal deposits.
Project summary : 
This project will undertake to reconstruct the behaviour of lithium in natural volcanic systems during magma differentiation in different tectonic settings, which includes degassing, fractionation, and assimilation/mixing. This new understanding will have important implications for understanding the conditions under which lithium hydrothermal deposits are formed (and may point to new proxies); and also for understanding short timescale volcanic processes for which lithium makes an excellent chronometer owing to its fast diffusion rates in crystals.
What will the student do?: 
Volcanic rocks from three contrasting settings will be examined: a metaluminous arc andesite, a peralkaline rhyolite (with high halogen contents) and a continental rhyolite. Partitioning of lithium between silicate melt, crystals and an exsolved voaltile phase will be determined through analysis of elemental lithium (and other trace elements and volatiles) as well as lithium isotopes, using Secondary Ion Mass Spectroscopy at the NERC facility, supplemented by microanalysis using QEMSCAN and EPMA at the University of Cambridge. The observations will be used to understand the compatibility and volatility of lithium for different magma compositions and tectonic settings.
References: 
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):270.
Ellis BS, Szymanowski D, Magna T, Neukampf J, Dohmen R, Bachmann O, Ulmer P, Guillong M. Post-eruptive mobility of lithium in volcanic rocks. Nature communications. 2018;9.
Liu S, Li Y, Liu J, Ju Y, Liu J, Yang Z, Shi Y. Equilibrium lithium isotope fractionation in Li-bearing minerals. Geochimica et Cosmochimica Acta. 2018 Jun 15.
Applying
You can find out about applying for this project on the Department of Earth Sciences page.