School of Earth and Environment

Romain Guilbaud Dr Romain Guilbaud

Visiting Research Fellow

Email address: r.j.guilbaud@leeds.ac.uk

Affiliation: Earth Surface Science Institute

Biography

My research interests focus on the extraction and the understanding of mineralogical and geochemical signals to reconstruct past biogeochemical processes and cycles.

I first did a Masters with Matthias Bernet and Pascale Huyghe at the University of Grenoble (France) where I studied how diagenesis altered the chemistry and the clay mineralogy of siliciclastic sediments in order to assess the sediment provenance and the depositional environment of the Himalayan foreland basin.

I then moved to Scotland for a PhD with Ian Butler (University of Edinburgh) and Rob Ellam (SUERC) on the experimental determination of Fe isotope fractionations within the Fe-S-H2O system at low temperature. The aim was to assess whether or not the Fe isotope compositions of sedimentary sulphides (pyrite in particular) could be used as a tracer for Archaean and Proterozoic microbial activity. This research led to collaborations with David Rickard at Cardiff University (formation and growth of FeS) and with Alan Matthews at the Hebrew University of Jerusalem (Cu isotope fractionations during the hydrothermal formation of CuS and CuFeS2).

My growing interest on the understanding of the evolution of biogeochemical processes on the early Earth led to work with Simon Poulton (first at Newcastle University and now at the University of Leeds as part of the Cohen Research Group) on the nutrient cycling during the Neoproterozoic era (1 to 0.542 Ga). I aim to better understand the supply and the redox-cylcing of major nutrients (e.g. P) in Neoproterozoic oceans which witnessed the abrupt appearance of animal Life and three major glacial events. Several marine successions capturing pre-, syn- and post-glacial sediments were sampled in the northern and southern China cratons. These transects constitute a potential archive of the biogeochemical response to the changes in ocean redox conditions and feedbacks associated with extreme climate change. My research combines both natural rock geochemistry (Fe and P speciation, stable isotopes of C and S, elemental analysis) and experimental work (mineral controls on nutrients in relation to the redox chemistry of the water column).

Memberships/Fellowships

2008-2011: member of the Mineralogical Society of Great Britain and Irland

2008-2010: sutdent representative of the Geochemistry Group committee (specialist group of the Mineralogical society)

Research Interests

Redox cycling of nutrients and bioessential transition metals of ancient oceans and implications for the evolution of life.

The behaviour of “non-traditional” isotope systems (in particular Fe and Cu) under diagenetic and hydrothermal conditions.

Development of experimental protocols for assessing geochemical mechanisms and pathways at low temperature (crystal nucleation, growth, surface charge evolution, adsorption, kinetic and equilibrium isotope exchange) within a range of geomaterial including oxygen sensitive species (aqueous species - clusters - nanoparticles - crystals).

Development of analytical procedures including the analysis of Fe isotope ratios, Fe sequential extractions, and the analysis of oxygen sensitive minerals.

Publications

Guilbaud, R., White, M.L., Poulton, S.W., 2013. Surface charge and growth of sulphated and carbonated green rust in aqueous media. Geochimica et Cosmochimica Acta, in press.

Guilbaud, R., Butler, I.B., Ellam, R.M., 2012. Response to Comment on "Abiotic pyrite formation produces a large Fe isotope fractionation". Technical Comment, Science, 335, 538.

Guilbaud, R., Bernet, M., Erens, V., Chirouze, F., Huyghe, P., Dupont-Nivet, G., 2012. On the influence of diagenesis on the original petrographic composition of Miocene-Pliocene fluvial sandstone in the Himalayan foreland basin of western-central Nepal. Journal of Asian Earth Sciences 44, 107-116.

Guilbaud, R., Butler, I.B., Ellam, R.M., 2011. Abiotic pyrite formation produces a large Fe isotope fractionation. Science, 332, 1548.

Guilbaud, R., Butler, I.B., Ellam, R.M., Rickard, D., Oldroyd, A., 2011. Experimental determination of the equilibrium Fe isotope fractionation between Fe2+aq and FeSm (mackinawite) at 25oC and 2oC. Geochim. Cosmochim. Act. 75, 2721-2734.

Huyghe, P., Guilbaud, R., Bernet, M., Galy, A., Gajurel, A., 2011. Significance of the clay mineral distribution in fluvial sediments of the Neogene and Recent Himalayan Foreland Basin (western-central Nepal). Basin Research, 23(3), 332-345.

Guilbaud, R., Butler, I.B., Ellam, R.M., Rickard, D., 2010. Fe isotope exchange between Fe(II)aq and nanoparticulate mackinawite (FeSm) during nanoparticle growth. Earth Planet. Sc. Let., 300, 174-183.

Guilbaud, R., Ellam, R.M., Butler, I.B., Gallagher, V., Keefe, K., 2010. A procedural development for the analysis of 56/54Fe and 57/54Fe isotope ratios with new generation IsoProbe MC-ICP-MS. Journal Analyt. Atom. Spect., 25, 1598-1604.