# Noble gas signatures of fluids at Santorini and Milos
(Greece).

Alexis Bernard, Anne Battani, Jean-Paul Callot, Finlay M Stuart, Uğur Balci,
Domokos Györe

► To cite this version:

Alexis Bernard, Anne Battani, Jean-Paul Callot, Finlay M Stuart, Uğur Balci, et al.. Noble gas signatures of fluids at Santorini and Milos (Greece). Goldschmidt 2023, Jul 2023, Lyon, France. European Association of Geochemistry, Goldschmidt Abstracts. hal-04424109

HAL Id: hal-04424109

https://univ-pau.hal.science/hal-04424109v1

Submitted on 29 Jan 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Noble gas signatures of fluids at Santorini and Milos (Greece).

Alexis Bernard¹, Anne Battani¹, Jean-Paul Callot¹, Finlay Stuart², Uğur Balci², Domokos Gyore³.

¹Université de Pau et des Pays de l'Adour (UPPA), LFCR, Pau, France.

²Scottish Universities Environmental Research Centre (SUERC), East Kilbride, Scotland UK.

³Isomass Scientific Inc., Calgary, Alberta, Canada.

<figure><img src="image_2.png" /></figure>

<figure><img src="image_3.png" /></figure>

Compared to the last volcanic unrest of 2011-2012 at Santorini (cf. Rizzo et al. 2015, and references therein), the CO₂/CH₄ ratio, and the H₂ concentration measured between 2015 and 2023 do not show any significant variations, whereas the CO₂/³He ratio decreases and the helium concentration increases continuously (cf. Fig. 3.A, and 3.B). In the plot of Fig. 3.C we used a model of selective dissolution of gases in water, using boundary conditions close to those measured at the surface. We simulate an open-system condensation process under equilibrium conditions (cf. Rizzo et al. 2019, and references therein). Results show that the previously detected anomalies of the CO₂/³He ratio could be explained by a less important fraction of residual gas, after the preferential dissolution of the CO₂. The reasons for this increase of CO₂ dissolution will be investigated in more details through more advanced thermodynamic modelling, in which parameters such as temperature, pressure, pH and salinity can be varied.

## Conclusion

I. This study led to the identification of several origins of CO₂, N₂ and helium, as well as geographical variations in the geochemical signatures.

II. During the period 2015-2022, helium anomalies were explained by variations in surface parameters, such as gas-water equilibrium conditions.

## References

1. Bocchini et al. (2018). Tearing, Segmentation, and Backstepping of Subduction in the Aegean: New Insights from Seismicity. Tectonophysics 734 735: 96–118. https://doi.org/10.1016/j.tecto.2018.04.002.

2. Fischer et al. (2002). Subduction and Recycling of Nitrogen Along the Central American Margin. Science 297, 5584: 1154–57. https://doi.org/10.1126/science.1073995.

3. Hansen et al. (2019). Imaging Slab Detachment Within the Western Hellenic Subduction Zone. Geochemistry, Geophysics, Geosystems 20, 2: 895–912. https://doi.org/10.1029/2018GC007810.

4. Jolivet et al. (2013). Aegean Tectonics: Strain Localisation, Slab Tearing and Trench Retreat. Tectonophysics, 597 598. 1–33. https://doi.org/10.1016/j.tecto.2012.06.011.

5. Moreira et al. (2019). New Insights into the Plumbing System of Santorini Using Helium and Carbon Isotopes. Geochemical Perspectives Letters, 46–50. https://doi.org/10.7185/geochemlet.1914.

6. Porcelli et al. (2002). Noble gases in geochemistry and cosmochemistry. Reviews in mineralogy and geochemistry, 7: 550–64. https://doi.org/10.1016/S0078-9745(01)00022-6.

7. Rizzo et al. (2015). New mafic magma refilling a quiescent volcano: Evidence from He-Ne-Ar isotopes during the 2011–2012 unrest at Santorini, Greece. Geochemistry, Geophysics, Geosystems, 16, 798–814. https://doi.org/10.1002/2014GC005653.

8. Rizzo et al. (2019). Geochemistry of CO₂-Rich Gases Venting From Submarine Volcanism: The Case of Kolumbo (Hellenic Volcanic Arc, Greece). Frontiers in Earth Science: 60. https://doi.org/10.3389/feart.2019.00060.

9. Sachpazi et al. (2016). Segmented Hellenic Slab Rollback Driving Aegean Deformation and Seismicity. Geophysical Research Letters 43: 651–58. https://doi.org/10.1002/2015GL066818.

<figure><img src="image_4.png" /></figure>

GOLDSCHMIDT
LYON
2023
9-14 JULY

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

## Acknowledgments

Many thanks to the INGV for their contributions to the data. We thank Laurent Jolivet, Andrea Luca Rizzo, Walter D'Alessandro, Konstantinos Kyriakopoulos, and Guillaume Galliero for their help.

Laboratoire des Fluides Complexes et leurs Réservoirs (LFCR), bat. IPRA. UPPA (Pau, France). alexis.bernard@univ-pau.fr / +33 6 52 09 90 96

## Contact