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Dr Gautier Nicoli

Dr Gautier Nicoli

Metamorphic and Igneous Petrology

Gautier Nicoli is available for consultancy.

Department of Earth Sciences
Office M07
University of Cambridge
Downing Street
Cambridge
UK

CB2 3EQ
Office Phone: +44 (0) 1223 333474

Biography:

My research focuses on understanding the physical and chemical behaviour of fluids and magmas in the continental lithosphere. The strength of my approach is the investigation of crustal differentiation processes through the integration of field and petrographic observations with fluid dynamics and modelling. My main goals in the next few years are (i) to investigate the consequences of secular changes on the stabilisation of the continental crust and (ii) to understand how metamorphic processes influence the nature and the volume of deep volatile element cycles (e.g. H2O, CO2). This will lead to a better understanding of the fate of volatile elements during planetary differentiation, which is crucial for the emergence of life on Earth.

My D.Phil. focused on the chemical differentiation of the continental crust, with emphasis on the link between the magma, its source and resulting intrusions (e.g. S-type granite). I employed a spectrum of petrographic techniques including microscopy (optical and electron), high temperature geochronology (U:Pb zircon analyses) and phase equilibrium modelling (Theriak-Domino). I then performed the first ever thermodynamically-assisted disequilibrium melting study, which established essential constraints for our understanding of crustal differentiation, fluid diffusion and the stabilisation of the continental mass.

In my current position as a Postdoctoral Research Assistant at Cambridge, I am working on quantifying magma crystallisation processes using microstructural investigation of magmatic intrusions (e.g. sills, dykes and layered complexes). Our understanding of magma genesis is at the heart of crustal evolution. At high-temperature conditions, there is a strong geological feedback between metamorphic processes (i.e. equilibrium-based solid phase mineral reactions) and igneous processes (i.e. melt crystallisation and extraction). Using crystal size distribution methods and analogue experiments, I am developing an approach to parametrise crystallisation in a set of well-defined tabular intrusions in Scotland, with applications for understanding the evolution of the early magma ocean.

I am also currently developing a theoretical method to quantify the water budget of the upper continental crust in accretionary settings. Preliminary results have shown that minor compositional variations in the upper crust can lead to significant variations in the depth and sequence of devolatilization events. Such an approach provides an intellectual framework to further our ability to understand the behaviour of volatile elements in the crust and to quantify the volume of the deep-crustal-volatile-elements reservoir.

Research Interests

The research project I am currently developing engages with the ongoing debate of the complex interaction between deep volatile cycles (e.g. H2O, CO2) and plate tectonic processes in regulating the composition of Earth’s fluid envelopes (i.e. atmosphere and hydrosphere). The global carbon cycle plays an important role in the long-term self-regulation of the Earth system. Efforts have been made by volcanologists over the years to work out the global carbon cycle and the behaviour of carbon in the lithospheric mantle is relatively well understood. These studies, however often overlook the role played by the continental crust (~30 vol.% of Earth’s crust) and the mechanisms responsible for the fate and budget of carbon-rich fluids in the middle-to-lower continental crust remain unknown. My research will focus on the factors and processes that may influence carbon storage, including the thickness of the crust, crustal reworking (i.e. metamorphic reactions) and the secular evolution of the composition of the crust. To that end, I will focus on pristine fluid and melt inclusions in high-grade rocks. I propose an innovative and novel approach that will combine chemical and in situ isotopic compositions (δ13C) with phase equilibria modelling of melt and fluid inclusions. This research will lay the foundations for a new field of “Environmental Metamorphic Petrology”, which will integrate deep Earth mechanisms with external global cycles. This has implications for our understanding the origin and the development of life on Earth and the potential for life on other planets. This project has been currently shortlisted for a 2019 NERC IRF (NE/S014616/1: Carbon buffering in the continental crust).

I am also currently involved in an international project, between the UK, Denmark and Canada, on the Skaergaard layered intrusion in Greenland. Using microstructural studies, we aim to understand magma rheology and late fluid distribution in magma chambers. This topic has high economic potential (i.e. from platinum deposits found in layered intrusions) and will be, in time, used to apply for further funding schemes. 

 

Keywords

Petrology ; Microscopy ; Volcanology ; Geochemistry ; microstructure

Topics

  • Textural development in crystal mush
  • Icelandic Magmatism
  • Layered intrusions
  • Volcanology
  • Igneous petrology
  • Liquid immiscibility

Key Publications

In prep:

Nicoli, G., Matthews, S. & Holness, M.B. (in prep) The Little Minch Sill Complex’s plumbing system, Scotland: a phase equilibria perspective. For Lithos.

Nicoli, G., Holness, M.B., Maclennan, J. & Neufeld, J. (in-prep) Crystallisation processes in tabular mafic intrusions: Insights from particle size distributions in the Little Minch Sill Complex. for EPSL.

Nicoli, G., Vukmanovic, Z. Neufeld, J. & Holness, M.B. (in-prep) Early nucleation and crystal growth in mafic intrusions and lava flows: insights from NH4Cl-H2O experiments. for Journal of Fluid Mechanics.

Peer-reviewed:

Nicoli, G. (2019). Water budget and partial melting in an Archean crustal column: example from the Dharwar craton, India. Geological Society, London, Special Publications, 489, SP489-2018.

Nicoli, G., Holness, M.B., Neufeld, J. and Farr, R. (in-press) Microstructural evidence for crystallization regimes in mafic intrusions: a case study from the Little Minch Sill Complex, Scotland, Contributions to Mineralogy and Petrology. DOI: 10.1007/s00410-018-1525-7

Vezinet, A., Moyen, J. F., Stevens, G., Nicoli, G., Laurent, O., Couzinié, S., & Frei, D. (2017). A record of 0.5 Ga of evolution of the continental crust along the northern edge of the Kaapvaal Craton, South Africa: Consequences for the understanding of Archean geodynamic processes. Precambrian Research.

Nicoli, G. & Dyck B. Exploring the metamorphic consequences of secular change in the siliciclastic compositions of continental margins. Geoscience Frontiers - Special Issue (in press).

Nicoli, G., Thomassot, E., Schannor, M., Vezinet, A., & Jovovic, I. (2017). Constraining a Precambrian Wilson Cycle lifespan: An example from the ca. 1.8 Ga Nagssugtoqidian Orogen, Southeastern Greenland. Lithos DOI: 10.1016/j.lithos.2017.10.017

Nicoli, G., Stevens, G., Moyen, J. F., Vezinet, A., & Mayne, M. Insights into the complexity of crustal differentiation: K2O‐poor leucosomes within metasedimentary migmatites from the Southern Marginal Zone of the Limpopo Belt, South Africa. Journal of Metamorphic Geology DOI: 10.1111/jmg.12265.

Nicoli, G., Steven,s G. & Moyen, J-F, 2016. Diversity of burial rates in convergent settings with time . Scientific Reports, 6.

Laurent O., Nicoli G., Zeh A., Stevens G., Moyen J–F. & Vezinet A., 2014. Comment on Ultrahigh-temperature granulites and magnesian charnockites: evidence for the Neoarchean accretion along the northern margin of the Kaapvaal craton by Rajesh et al. Precambrian Research DOI: 10.1016/j.precamres.2014.07.010.

Nicoli G., Stevens G., Moyen J–F. & Frei D., 2014. Rapid evolution from sediment to anatectic granulite in an Archean continental collision zone: The example of the Bandelierkop Formation metapelites, South Marginal Zone, Limpopo Belt, South Africa. Journal of Metamorphic Geology, DOI: 10.1111/jmg.12116.

Nicoli G., Stevens G., Buick I.S., & Moyen J–F., 2015. Comment on Ultrahightemperature metamorphism from an unsual corundum + orthopyroxene intergrowth bearing Al-Mg granulite from the Southern Marginal Zone, Limpopo Belt, South Africa. Contribution to Mineralogy and Petrology, DOI: 10.1007/s00410-014-1022-6.

Taylor J., Nicoli G., Stevens G., Frei D. & Moyen J–F., 2014. The processes that control leucosome compositions in metasedimentary granulites: Perspectives from the Limpopo Belt (South Africa) South Marginal Zone anatectites. Journal of Metamorphic Geology, DOI: 10.1111/jmg.12087.

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