Expert Exchange: Assessing the History of Magmatic Emissions from the Neo-Tethyan Magmas and their Contribution to Early Cenozoic Climate Changes

Europlanet 2024 RI’s Expert Exchange Programme aims to support the planetary community to share expertise and best practice, and to prepare new facilities and services. The programme provides funding for short visits (up to one week).

Léa Ostorero of the Department of Earth and Environmental Sciences (DISAT) University of Milano-Bicocca, Milan, Italy, visited Pierre Bouilhol Université de Lorraine, Centre de Recherches Pétrographiques et Géochimiques (CRPG / CNRS) in France from 09-20 October and 2024 November 2023.

Motivations of the Visit

Magmatic melts and volatiles trapped in crystals as melt inclusions can record the storage conditions of the magmas and the pre-eruptive volatile contents. Based on the petrological records of volatiles within magmatic samples from Ladakh (India) and Iran, we aimed to retrieve their pre-eruptive CO₂ budget as a first step to reconstructing the time history of CO₂ emissions from the Neo-Tethyan margin and possible effects on the Early Cenozoic climate. Indeed, a climate warming and then cooling trend occurred during the Early Cenozoic and can be correlated with changes in the Neo-Tethyan magmatic activity.

With this visit, we analysed the CO₂ content in the melt inclusions of pyroxenes, feldspars and quartz from andesites and rhyolites from the study areas, with Secondary Ions Mass Spectrometry (SIMS), available at CRPG in Nancy (France). SIMS is an extremely versatile tool for analysis of glassy melt inclusions (Walter and Amelung, 2006; Esposito, 2021; Rose-Koga et al., 2021). Obtaining different pre-eruptive CO₂ budgets depending on the ages of the samples could help us unravel the relationships between plate tectonics, magmatism and climate.

Scientific outputs of the visit

SIMS uses a focused beam of primary ions to sputter secondary ions from the surface of a material. These ions are then accelerated and analysed by a mass spectrometer. SIMS is particularly useful in determining volatile element abundances (including C, O, H, for example) (Kent, 2008; Cannatelli et al., 2016) and provides sub-per mil precision analysis and a high resolution (Rose-Koga et al., 2021).

The visit was divided in two parts because when I first came to Nancy in October 2023, my SIMS session was cancelled due to a technical problem with the machine (the ion beam was not stable). I have been nevertheless able to prepare the samples on Indium mounts instead of resin mounts. Indium is a malleable metal, and allows positioning several crystals without the need to prepare a resin. Resin mounts are problematic, as they degas in vacuum, thus polluting the baseline signal. Indium mounts provides a better background for our purpose (Volatile analyses). I was able to come back in November 2023 to carry out SIMS analyses during one week.

The host group has a unique experience in carrying state of the art SIMS analyses, especially for volatiles, I thus benefited from their expertise. With the hosting researcher, I shared petrological observations on some thin sections I prepared and we had the opportunity to discuss the petrography of our samples.

The Expert Exchange thus allowed me to use SIMS facilities at CRPG in Nancy and acquire the first results of my postdoc. I also acquired new skills on how to prepare the samples, select standards before SIMS analyses, measure volatile data (e.g. CO₂, H₂O, F, Cl and S) in melt inclusions and process the volatile data after analyses. Overall, it allowed me to learn the inside-outs of SIMS analyses.

I also had the opportunity to give a seminar to the host group on my PhD and the first results of my postdoc, which was on “Crystals records: from magma dynamics before eruptions to climactic impacts”. This seminar allowed me to discuss the implications of the volatile analyses carried out at CRPG for my postdoc and find the best analytical conditions suitable for our samples during the SIMS session. It may also lead to future collaboration with other scientists from CRPG and other SIMS sessions in the future.

The measurements obtained during the visit will be processed and other data will be added to the SIMS analyses, to characterise volatile emissions from the magmas. SIMS analyses will allow us to quantify the role of CO₂ outgassing from the Neo-Tethyan magmatic arc in affecting Early Cenozoic climate. Unravelling the relationships between geodynamics and climate will help us framing current human-induced climate changes into the context of the natural climate variability, thereby improving our understanding of the functioning of the Earth System. This work is expected to result in at least one scientific publication in peer-reviewed journals.

References

• Cannatelli C, Doherty AL, Esposito R, et al (2016) Understanding a volcano through a droplet: A melt inclusion approach. J Geochemical Explor 171:4–19. https://doi.org/10.1016/j.gexplo.2015.10.003
• Esposito R (2021) Chapter 7: A protocol and review methods to select, analyze and interpret melt inclusions to determine pre-eruptive volatile contents of magmas. In: Fluid and Melt Inclusions: Applications to Geologic Processes. MAC, pp 1–32 Kent AJR (2008) Melt Inclusions in Basaltic and Related Volcanic Rocks. Rev Mineral Geochemistry 69:273–331. https://doi.org/10.2138/rmg.2008.69.8
• Rose-Koga EF, Bouvier A-S, Gaetani GA, et al (2021) Silicate melt inclusions in the new millennium: A review of recommended practices for preparation, analysis, and data presentation. Chem Geol 570:120145. https://doi.org/10.1016/j.chemgeo.2021.120145 Walter TR, Amelung F (2006) Volcano-earthquake interaction at Mauna Loa volcano, Hawaii. J Geophys Res Solid Earth 111:n/a-n/a. https://doi.org/10.1029/2005JB003861

Expert Exchange Objectives covered by this visit: Training, Early Career Support.

Find out more about the Europlanet Expert Exchange Programme.