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E432: The distribution of carbon in Earth's mantle (Lead Supervisor: John Maclennan, Earth Sciences)

Supervisors: John Maclennan (Earth Sciences), Oliver Shorttle (Earth Sciences/Institute of Astronomy) and John Rudge (Earth Sciences)

Importance of the area of research:

Carbon plays a crucial role in planetary evolution. Its partitioning between major geochemical reservoirs is a major control on the Earth's climate and habitability through time. However, estimates of the bulk carbon content of the mantle are extremely uncertain. A key part of this uncertainty stems from our poor understanding of how carbon varies in mantle materials. This project is focussed on improving our models of carbon distribution in the mantle.

Project summary:

We have recently made the exciting discovery of a suite of olivine-hosted melt inclusions from South Iceland with extremely high carbon contents with respect to other geochemically-related elements. These observations indicate that parts of the mantle under Iceland have carbon contents that are about an order of magnitude higher than previous estimates for the upper mantle. Our recent modelling also indicates that it is only possibly to robustly infer mantle carbon from melt inclusions when large numbers of measurements are available from suitable eruptions.  This project is therefore focussed on using olivine-hosted melt inclusions to better define the distribution of volatiles in Earth's mantle.

What the student will do:

The student will initially gather a sample suite from Iceland and other suitable oceanic settings. These samples will be added to material already available in Cambridge. The samples will be prepared for analysis using SEM, EPMA and Raman spectroscopy at Cambridge and ion-probe at national facilities. The data will be modelled using a new computational approach which permits the mantle signal of carbon variability to be extracted from the noise of shallow mixing and degassing. Finally, this variation in carbon will be linked to other geochemical indicators of mantle heterogeneity to both understand the origins of carbon variability and to explore its consequences for the Earth system.

Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.

References:

Shimizu, K., et al., 2016. Two-component mantle melting-mixing model for the generation of mid-ocean ridge basalts: Implications for the volatile content of the Pacific upper mantle. Geochim. Cosmochim. Acta 176, pp. 44-80. doi:10.1016/j.gca.2015.10.033

Saal, A.E., et al., 2002. Vapour undersaturation in primitive mid-ocean-ridge basalt and the volatile content of Earth's upper mantle. Nature, 419, pp. 451-455. doi:10.1038/nature01073

Le Voyer, M., et al., 2017. Heterogeneity in mantle carbon content from CO2-undersaturated basalts., Nature Communications., 8, 14062.

Follow this link to find out about applying for this project.

Other projects available from the Lead Supervisor can be viewed here.

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