Global biogeochemical cycling of Fe and S
Novel use and development of conventional geochemical (trace and REE) and isotopic (stable S and radiogenic Sr, Nd) techniques
Mössbauer spectroscopy, MC-ICP-MS, ICP-OES/AES, TIMS
Marine sediment diagenesis
Deep sea hydrothermal systems
Oceanography and deep sea exploration
Fostering interdisciplinary interactions throughout ocean and earth science
Research Fellow, University of Stirling
Active research projects:
The sedimentary iron cycle: a novel way to iron mineral characterization and separation
Reactive Fe mineral phases within the marine and terrestrial biosphere are an important component of global nutrient (particularly S, C, and obviously Fe) cycling, but difficult to characterise and quantify using standard mineralogical tools. Lengthy sequential extraction procedures that rely on reagent-specific mineral solubility are currently used to separate and define individual mineral phases. Although such methods are fundamental where mineral separation is required (e.g. investigating isotopic variation between specific mineral phases), Mössbauer spectroscopy offers a time-saving, indestructive, more accurate alternative for mineral identification, which can also be used in-situ. This project will cross-calibrate sequential Fe extraction and Mössbauer spectroscopic methods to advance the analytical accuracy of quantitative Fe mineral determination, particularly bioavailable Fe colloids and nanoparticulates.
Biogeochemical S cycling in the Kemp Caldera
From a geochemist’s perspective, marine sediment S transformations occur via heterogeneous reactions with sulfides, oxides, and other reduction/oxidation- or redox-competing chemical species. Microbiologists, however, view sediment S cycling as the transfer of metabolic energy by chemoautotrophic or heterotrophic bacteria. In this project, the stable isotopic S composition of bulk and individual sediment sulfur phases in the hydrothermally-influenced sediments of a Southern Ocean submarine caldera, will be combined with microbiological analyses to distinguish between inorganic and biogenic sediment S cycling.
Bell, J., Aquilina, A., Woulds, C., Glover, A., Little, C., Reid, W., Hepburn, L., Newton, J., Mills, R. (2016). Geochemistry, faunal composition and trophic structure in reducing sediments on the southwest South Georgia margin. Royal Society of Open Science, 3: 160284.
Aquilina, A., Connelly, D., Copley, J., Green, D., Hawkes, J., Hepburn, L., Huvenne, V., Marsh, L., Mills, R., Tyler, P. (2013). Geochemical and visual indicators of hydrothermal fluid flow through a sediment-hosted volcanic ridge in the central Bransfield Basin (Antarctica). PLoS One, 8(1): e54686.
Hepburn, L., Mills, R., Aquilina, A., Copley, J., Glover, A., Tyler, P. (2011). Subsurface biogeochemistry of hydrothermal flow at the Hook Ridge, Bransfield Strait. Mineralogical Magazine, 75(3): 1011.
Hernandez-Sanchez, M., Mills, R., Planquette, H., Pancost, R., Hepburn, L., Salter, I., FitzGeorge-Balfour, T. (2011). Quantifying export production in the Southern Ocean: Implications for the BaXS proxy. Paleoceanography, 26: PA4222.
Homoky, W., Hembury, D., Hepburn, L., Mills, R., Statham, P., Fones, G., Palmer, M. (2011). Iron and manganese diagenesis in deep sea volcanogenic sediments and the origins of pore water colloids. Geochimica et Cosmochimica Acta, 75: 5032–5048.