ARC Centre of Excellence for Core to Crust Fluid Systems

 

Dr Romain Tilhac

Research Interests

My research interests are centred on the composition and evolution of the Earth’s mantle, focusing on mass transfers occurring during arc magmatism. As a geochemist and trained structural geologist, my approaches include field studies of mafic and ultramafic terranes exposed in ophiolites and orogenic massifs, petrology, in situ and solution geochemistry and geochronology. By characterizing elemental mobility and isotopic fractionation, this aims to contribute to our understanding of the genesis of mantle-derived magmas, the nature and heterogeneity of their sources and the processes involved in their differentiation. I am especially interested in the petrogenesis of pyroxenites, emphasizing the role of melt-rock interaction and crystal segregation in the “lithospheric filter”. My PhD consisted in the petrology, geochemistry and radiogenic-isotope geochemistry (Sr-Nd-Hf-Os) of pyroxenites from the Variscan Cabo Ortegal Complex, Spain, and of their associated peridotites and chromitites. I proposed that these large amounts of pyroxenite represent delaminated segregates of Ca-rich magmas of picritic to boninitic affinities intruded in a Cadomian ensialic arc root. The significance of this lies in the broader topic of the debated contribution of arc magmatism as a crust-forming process contributing to the evolution of Earth’s geochemical reservoirs. In this respect, I also undertake analytical work as part of the TerraneChron^® methology (i.e. combined U-Pb zircon geochronology, in situ trace-element and Hf-isotope analysis) to study crustal evolution and associated metallogenic potentials with industry partners. Besides, I am collaborating with Macquarie’s Geophysics and Geodynamics (M3G) to model the intrinsic disequilibrium of trace-element fractionation associated with magmatic processes in the mantle, by implementing a thermodynamically consistent approach based on recently developed numerical tools.

Mantle harzburgite in Cabo Ortegal, Spain

Background

After a BSc and MSc in Earth and Planetary Sciences completed at Paul Sabatier University, Toulouse, France (2007-2011), with research experiences in structural geology and fluid-rock interaction in sedimentary rocks, I completed my PhD as a co-tutelle program between Macquarie University and my home university (2012-2016). I then took on a Research Associate position in the ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS). As for my personal background, I grew up in the French Pyrenees where I have been caving, hiking and rock climbing for a long time.

 

Sampling the pyroxenite-dunite association

Chromatographic separation of Sr, Nd and Hf for isotope analysis

Publications

Tilhac, R., Griffin, W.L., O’Reilly, S.Y., Ceuleneer, G., Schaefer, B., Henry, H., Grégoire, M. 2017. Radiogenic isotope geochemistry of Cabo Ortegal pyroxenites: origin and age of a sub-arc mantle domain. Goldschmidt Conference.

Oliveira, B., Afonso, J.C., Tilhac, R., Numerical Modelling of Multi-Phase Multi-Component Reactive Transport in the Earth’s interior. 2017. Goldschmidt Conference.

Henry, H., Afonso, J.C., Satsukawa, T., Griffin, W.L., O’Reilly, S.Y., Kaczmarek, M.-A., Tilhac, R., Grégoire, M., Ceuleneer, G. 2017. Goldschmidt Conference.

Tilhac, R., Grégoire, M., O’Reilly, S.Y., Griffin, W.L., Henry, H., Ceuleneer, G., 2017. Source and timing of pyroxenite formation in the sub-arc mantle: Case
study of the Cabo Ortegal Complex, Spain. Earth and Planetary Science Letters, 474, 490-502.

Henry, H., Tilhac, R., Griffin, W.L., O’Reilly, S.Y., Satsukawa, T., Kaczmarek, M.-A., Grégoire, M., Ceuleneer, G. 2017. Deformation of mantle pyroxenites provides clues to geodynamic processes in subduction zones: Case study of the Cabo Ortegal Complex, Spain. Earth and Planetary Science Letters, 472, 174-185.

Oliveira, B., Afonso, J.C., Zlotnik, S., Tilhac, R. 2017. Numerical Modelling of Multi-Phase Multi-Component Reactive Transport in the Earth’s interior. 2017. European Geosciences Union (EGU) General Assembly, 19, 18307.

Tilhac, R., Ceuleneer, G., Griffin, W.L., O’Reilly, S.Y., Pearson, N.J., Benoit, M., Henry, H., Girardeau, J. & Grégoire, M. 2016. Primitive arc magmatism and delamination: petrology and geochemistry of pyroxenites from the Cabo Ortegal Complex, Spain. Journal of Petrology, 57, 1921-1954.

Tilhac, R., Grégoire, M., Ceuleneer, G., O’Reilly, S.Y., Griffin, W.L., & Pearson, N.J. 2015. Metasomatized segregates of high-Ca boninites: Cabo Ortegal pyroxenites. Goldschmidt Conference, 3133.

Tilhac, R., O’Reilly, S.Y., Griffin, W.L., Pearson, N.J., Ceuleneer, G., & Grégoire, M. 2015. Multi-stage supra-subduction metasomatism in the Cabo Ortegal Complex, Spain. European Geosciences Union (EGU) General Assembly, 17, 454.

Tilhac, R., O’Reilly, S., Griffin, W.L., Pearson, N.J., Ceuleneer, G., González-Jiménez, J.M., & Grégoire, M., 2014. How mantle heterogeneities control supra-subduction metasomatism: constraints from the Cabo Ortegal Complex, Spain. AESC, Geological Society of Australia, Abstracts, 110, AESC, 22nd Australian Geological Convention, 301.

Perrin, C., Prestimonaco, L., Servelle, G., Tilhac, R., Maury, M., & Cabrol, P. 2014. Aragonite-calcite speleothems: identifying original and diagenetic features. Journal of Sedimentary Research, 84, 245-269.

Tilhac, R., Guillaume, D., & Odonne, F., 2013. Fluid circulation and deformational gradient in north-Pyrenean flyschs: example from the Saint-Jean-de-Luz basin (France). Tectonophysics, 608, 832-846.

Perrin, C., Prestimonaco, L., Servelle, G., Tilhac, R., Maury, M., & Cabrol, P. 2013, Growth and diagenetic history of aragonite-calcite speleothems, implications for environmental studies. 16^th ICS Proceedings, 2, 447-449.

Perrin, C., Prestimonaco, L., Servelle, G., Tilhac, R., Maury, M. & Cabrol, P., 2012. Aragonite-calcite speleothems (Hérault, France): Identifying original and diagenetic features. 29^th IAS Meeting of Sedimentology, 40.