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Response of a Hydrothermal System to Escalating Phreatic Unrest the Case of Turrialba and Irazú in Costa Rica (2007-2012)
Dmitri Rouwet
INGV, Bologna
Corresponding Author
ORCiD: https://orcid.org/0000-0003-3366-3882
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This study presents the first hydrogeochemical model of the hydrothermal systems of Turrialba and Irazú volcanoes in central Costa Rica, manifested as thermal springs, summit crater lakes, and fumarolic degassing at both volcanoes. Our period of observations (2007-2012) coincides with the pre- and early syn-phreatic eruption stages of Turrialba volcano that resumed volcanic unrest since 2004, after almost 140 years of quiescence. Peculiarly, the generally stable Irazú crater lake dropped its level during this reawakening of Turrialba. The isotopic composition of discharged fluids reveals the Caribbean meteoric origin; a contribution of “andesitic water” for Turrialba fumaroles up to ~50% is suggested. Four groups of thermal springs drain the northern flanks of Turrialba and Irazú volcanoes into two main rivers. Río Sucio (i.e. “dirty river”) is a major rock remover on the North flank of Irazú, mainly fed by the San Cayetano spring group. Instead, one group of thermal springs discharges towards the south of Irazú. All thermal spring waters are of SO4-type (i.e. steam heated waters), although none of the springs has a common hydrothermal end-member. A water mass budget for thermal springs results in an estimated total output flux of 187 ± 37 L/s, with 100 ± 20 L/s accounted for by the San Cayetano springs. Thermal energy release is estimated at 110 ± 22 MW (83.9 ± 16.8 MW by San Cayetano), whereas the total rock mass removal rate by chemical leaching is ~3,000 m3/y (~2,400 m3/y by San Cayetano-Río Sucio). Despite Irazú being the currently less active volcano, it is a highly efficient rock remover, which, on the long term can have effects on the stability of the volcanic edifice with potentially hazardous consequences (e.g. flank collapse, phreatic eruptions). Moreover, the vapor output flux from the Turrialba fumaroles after the onset of phreatic eruptions on 5 January 2010 showed an increase of at least ~260 L/s above pre-eruptive background fumarolic vapor fluxes. This extra vapor loss implies that the drying of the summit hydrothermal system of Turrialba could tap deeper than previously thought, and could explain the coincidental disappearance of Irazú’s crater lake in April 2010.
Keywords
Irazú and Turrialba volcanoes, phreatic eruptions, thermal springs, fluid geochemistry, crater lake disappearance, water budget analysis, hazard assessment
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Due to technical limitations, full-text HTML conversion of this manuscript could not be completed. However, the latest manuscript can be downloaded and accessed as a PDF.
Due to technical limitations, tables are only available as a download in the Supplemental Files section.
This is a list of supplementary files associated with this preprint. Click to download.
- Table1Rouwetetal.EPS.docx
Level variations of Irazú crater lake: levels of the lake were measured by comparing photos taken in different times according to the method established by Rouwet (2011).
- Table2Rouwetetal.EPS.docx
Temperatures, pH values, major elements concentrations, TDS (Total Dissolved Solids), isotope val-ues for the thermal springs and Irazú-Turrialba crater lakes. Isotope values for Irazú and Turrialba fumaroles are also reported. n.m., not measured; b.d.l., below detection limit; n.a., not analyzed. SC = San Cayetano, ST = Santa Teresita, OJA = Oja de Agua, HBA = Hervideros de Buenos Aires, IL = Irazú crater lake (E and N), IF = Irazú fumarole, BLP = Bajo Las Peñas, TL = Turrialba crater lake, TF = Turrialba fumarole.
- Table3aRouwetetal.EPS.docx
Temperature, chemical (pH, Cl, SO4) and isotope values of meteoric waters (AM), rivers and cold springs for Irazú (I) (a) and Turrialba (T) (b): n.m., not measured. Meteoric water values are general-ly assumed as corresponding to the rivers (Ríos and Quebradas), for which the average water dis-charges are reported. HBA and SC as in Table 2.
- Table3bRouwetetal.EPS.docx
- Table4Rouwetetal.EPS.docx
Minor and trace element composition of Irazú-Turrialba thermal springs and crater lakes (in microgram/L). n.m., not measured; b.d.l., below detection limit; n.a., not analyzed. Abbreviations as in Table 2.
- Table5Rouwetetal.EPS.docx
SO4 concentrations and discharge (QSO4) and water discharge (Q) of thermal springs and main riv-ers of Irazú and Turrialba. - = not applicable. Abbreviations as in Table 2.
- Table6Rouwetetal.EPS.docx
SO4/major elements ratios (e.g. SO4/Na; the ratio for Si is reported as SO4/SiO2) and major elements oxides discharge (e.g. QNa2O) for the studied thermal springs. Rock output rates for the springs are reported (in mg/s, corresponding to m3/y by assuming a rock density of 2,800 kg/m3), together with a total rock output for the whole of studied thermal springs. Abbreviations as in Table 2.
- GraphicalabstractRouwetetal.EPS2020.pdf
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This preprint is under consideration at Earth, Planets and Space. A preprint is a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Full paper
Response of a Hydrothermal System to Escalating Phreatic Unrest the Case of Turrialba and Irazú in Costa Rica (2007-2012)
Dmitri Rouwet
INGV, Bologna
Corresponding Author
ORCiD: https://orcid.org/0000-0003-3366-3882
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Under Review
Version 1
Posted 07 Jan, 2021
No community comments so far
Reviewer #1 agreed
On 13 Jan, 2021
Reviewers invited
Invitations sent on 10 Jan, 2021
Editor assigned
On 03 Jan, 2021
Editor invited
On 03 Jan, 2021
Submission checks complete
On 01 Jan, 2021
First submitted
On 29 Dec, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
License:
This work is licensed under a CC BY 4.0 License. Read Full License
This study presents the first hydrogeochemical model of the hydrothermal systems of Turrialba and Irazú volcanoes in central Costa Rica, manifested as thermal springs, summit crater lakes, and fumarolic degassing at both volcanoes. Our period of observations (2007-2012) coincides with the pre- and early syn-phreatic eruption stages of Turrialba volcano that resumed volcanic unrest since 2004, after almost 140 years of quiescence. Peculiarly, the generally stable Irazú crater lake dropped its level during this reawakening of Turrialba. The isotopic composition of discharged fluids reveals the Caribbean meteoric origin; a contribution of “andesitic water” for Turrialba fumaroles up to ~50% is suggested. Four groups of thermal springs drain the northern flanks of Turrialba and Irazú volcanoes into two main rivers. Río Sucio (i.e. “dirty river”) is a major rock remover on the North flank of Irazú, mainly fed by the San Cayetano spring group. Instead, one group of thermal springs discharges towards the south of Irazú. All thermal spring waters are of SO4-type (i.e. steam heated waters), although none of the springs has a common hydrothermal end-member. A water mass budget for thermal springs results in an estimated total output flux of 187 ± 37 L/s, with 100 ± 20 L/s accounted for by the San Cayetano springs. Thermal energy release is estimated at 110 ± 22 MW (83.9 ± 16.8 MW by San Cayetano), whereas the total rock mass removal rate by chemical leaching is ~3,000 m3/y (~2,400 m3/y by San Cayetano-Río Sucio). Despite Irazú being the currently less active volcano, it is a highly efficient rock remover, which, on the long term can have effects on the stability of the volcanic edifice with potentially hazardous consequences (e.g. flank collapse, phreatic eruptions). Moreover, the vapor output flux from the Turrialba fumaroles after the onset of phreatic eruptions on 5 January 2010 showed an increase of at least ~260 L/s above pre-eruptive background fumarolic vapor fluxes. This extra vapor loss implies that the drying of the summit hydrothermal system of Turrialba could tap deeper than previously thought, and could explain the coincidental disappearance of Irazú’s crater lake in April 2010.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Due to technical limitations, full-text HTML conversion of this manuscript could not be completed. However, the latest manuscript can be downloaded and accessed as a PDF.
Due to technical limitations, tables are only available as a download in the Supplemental Files section.