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New insights into the plumbing system of Santorini using helium and carbon isotopes

M. Moreira1,

1Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France

J. Escartin1,

1Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France

L. Scelin1,

1Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France

L. Ruzié-Hamilton2,

2SEES - The University of Manchester, United Kingdom

P. Nomikou3,

3Faculty of Geology and Geoenvironment, National and Kapodistrian University of Athens, Panepistimioupoli, Zographou, Greece

C. Mével1,

1Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France

M. Andreani4

4Laboratoire de Géologie de Lyon, UMR 5276, ENS et Université Lyon 1, France

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Moreira, M., Escartin, J., Scelin, L., Ruzié-Hamilton, L., Nomikou, P., Mével, C., Andreani, M. (2019) New insights into the plumbing system of Santorini using helium and carbon isotopes. Geochem. Persp. Let. 10, 46–50.

Ship time was provided by the Eurofleets CALDERA 2012 Project (EU) and by HCMR (Greece). JE and CM were also partly supported by the DCO initiative from the Alfred Sloan Foundation.

Geochemical Perspectives Letters v10  |  doi: 10.7185/geochemlet.1914
Received 7 September 2018  |  Accepted 2 April 2019  |  Published 20 May 2019
Copyright © The Authors

Published by the European Association of Geochemistry
under Creative Commons License CC BY-NC-ND 4.0




Figure 1 (a) Synthetic topographic map (Nomikou et al., 2014

Nomikou, P., Parks, M.M., Papanikolaou, D., Pyle, D.M., Mather, T.A., Carey, S., Watts, A.B., Paulatto, M., Kalnins, M.L., Livanos, I., Bejelou, K., Simou, E., Perrose, I. (2014) The emergence and growth of a submarine volcano: The Kameni islands, Santorini (Greece). GeoResJ 1-2, 8-18.

) showing the position of hydrothermal outflow areas within the Santorin caldera. Two samples were collected at the ‘Reference’ site, which corresponds to near-bottom water away from hydrothermal sources and at the bottom of the northern basin of the caldera. The other samples were collected at the caldera hydrothermal field (CHF), which shows mounds of bacterial mat (b), and at the Kallisti Limnes (KL), which shows sub-sea pools with CO2-rich fluids (Camilli et al., 2015

Camilli, R., Nomikou, P., Escartin, J., Ridao, P., Mallios, A., Kilias, S., Argyraki, A., Andreani, M., Ballu, V., Campos, R., Deplus, C., Gabsi, T., Garcia, R., Gracias, N., Hurtos, N., Magi, L., Mevel, C., Moreira, M., Palomeras, N., Pot, O., Ribas, D., Ruzie, L., Sakellariou, D. (2015) The Kallisti Limnes, carbon dioxide-accumulating subsea pools. Scientific Reports 12152.

) (c and d). CHF and other hydrothermal areas throughout the caldera where observed in 2006 (Sigurdsson et al., 2006

Sigurdsson, H., Carey, S., Alexandri, M., Vougioukalakis, G., Croff, K., Roman, C., Sakellariou, D., Anagnostou, C., Rousakis, G., Ioakim, C., Godou, A., Ballas, D., Misaridis, T., Nomikou, P. (2006) Marine Investigations of Greece’s Santorini Volcanic Field. EOS 87, 337.

). The red open circle corresponds to the Mogi source model associated with the 2011 inflation event (Newman et al., 2012

Newman, A.V., Stiros, S., Feng, L., Psimoulis, P., Moschas, F., Saltogianni, V., Jiang, Y., Papazachos, C., Panagiotopoulos, D., Karagianni, E., Vamvakaris, D. (2012) Recent geodetic unrest at Santorini Caldera, Greece. Geophysical Research Letters 39, L06309.

). A and A’ indicate the ends of bathymetric profile in Figure 3.
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Figure 2 (a) Mixing diagram showing the 3He/4He ratio reported against 4He/22Ne (Ra is the helium atmospheric isotopic ratio). The mantle-derived end member has a 3He/4He ratio of ~ 7 Ra, identical to the value of the nearby Kolumbo volcano (Carey et al., 2013

Carey, S., Nomikou, P., Croff Bell, K., Lilley, M., Lupton, J.E., Roman, C., Stathopoulou, E., Bejelou, K., Ballard, R. (2013) CO2 degassing from hydrothermal vents at Kolumbo submarine volcano, Greece, and the accumulation of acidic crater water. Geology 41, 1035-1038.

; Rizzo et al., 2016

Rizzo, A., Caracausi, A., Chavagnac, V., Nomikou, P., Polymenakou, P., Mandalakis, M., Kotoulas, G., Magoulas, A., Castillo, A., Lampridou, D. (2016) Kolumbo submarine volcano (Greece) An active window into the Aegean subduction system. Scientific Reports 6, 1-9.

) suggesting a common mantle source. All samples from Palea or Nea Kameni (gases and fluid/melt inclusions in phenocrysts) show a different trend, with a lower 3He/4He ratio reflecting shallow crustal assimilation (Shimizu et al., 2005

Shimizu, A., Sumino, H., Nagao, K., Notsu, K., Mitropoulos, P. (2005) Variation in noble gas isotopic composition of gas samples from the Aegean arc, Greece. Journal of Volcanology and Geothermal Research 140, 321-339.

; Rizzo et al., 2015

Rizzo, A., Barberi, F., Carapezza, L., Di Piazza, A., Francalanci, L., Sortino, F., D'Alessandro, W. (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.

). The insert shows the 3He/4He ratio versus δ13C (b) and CO2/3He (c). The strong hyperbolic curvature of the mixing curve reported in insert (b) reflects the (4He/CO2)seawater/(4He/CO2)MORB ratio of ~0.024, explaining why the δ13C does not show a mantle value whereas helium almost does. Percentages that are indicated on the mixing curves represent the fraction of seawater-derived helium.
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Figure 3 Possible sources and transfer of magmatic CO2 and He within the Santorini caldera. Gases from Nea Kameni derive from a shallow reservoir, which is degassed and has assimilated crustal rocks, sampled by hydrothermal circulation (a, b). A pristine mantle signature is sampled by fluids at the Kalisti Limnes and hydrothermal areas. These fluids may either percolate through the volcanic shield and the pre-volcanic basement (c), or be supplied from a more central area and in association with recent magma chambers, if the fluids migrate along caldera walls and associated caldera faults (d).
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