Origin of High Mg and SO4 Fluids in Sediments of the Terceira Rift, Azores-Indications for Caminite Dissolution in a Waning Hydrothermal System

C. Schmidt; C. Hensen; K. Wallmann; V. Liebetrau; M. Tatzel; S. L. Schurr; S. Kutterolf; L. Haffert; S. Geilert; C. Hübscher; E. Lebas; A. Heuser; M. Schmidt; H. Strauss; J. Vogl; T. Hansteen

doi:10.1029/2019GC008525

Origin of High Mg and SO₄ Fluids in Sediments of the Terceira Rift, Azores-Indications for Caminite Dissolution in a Waning Hydrothermal System

C. Schmidt^*, C. Hensen, K. Wallmann, V. Liebetrau, M. Tatzel, S. L. Schurr, S. Kutterolf, L. Haffert, S. Geilert, C. Hübscher, E. Lebas, A. Heuser, M. Schmidt, H. Strauss, J. Vogl, T. Hansteen

^*Corresponding author for this work

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Abstract

During R/V Meteor cruise 141/1, pore fluids of near surface sediments were investigated to find indications for hydrothermal activity in the Terceira Rift (TR), a hyperslow spreading center in the Central North Atlantic Ocean. To date, submarine hydrothermal fluid venting in the TR has only been reported for the D. João de Castro seamount, which presently seems to be inactive. Pore fluids sampled close to a volcanic cone at 2,800-m water depth show an anomalous composition with Mg, SO₄, and total alkalinity concentrations significantly higher than seawater and a nearby reference core. The most straightforward way of interpreting these deviations is the dissolution of the hydrothermally formed mineral caminite (MgSO₄ 0.25 Mg (OH)₂ 0.2H₂O). This interpretation is corroborated by a thorough investigation of fluid isotope systems (δ²⁶Mg, δ³⁰Si, δ³⁴S, δ^44/42Ca, and ⁸⁷Sr/⁸⁶Sr). Caminite is known from mineral assemblages with anhydrite and forms in hydrothermal recharge zones only under specific conditions such as high fluid temperatures and in altered oceanic crust, which are conditions generally met at the TR. We hypothesize that caminite was formed during hydrothermal activity and is now dissolving during the waning state of the hydrothermal system, so that caminite mineralization is shifted out of its stability zone. Ongoing fluid circulation through the basement is transporting the geochemical signal via slow advection toward the seafloor.

Original language	English
Pages (from-to)	6078-6094
Number of pages	17
Journal	Geochemistry, Geophysics, Geosystems
Volume	20
Issue number	12
DOIs	https://doi.org/10.1029/2019GC008525
Publication status	Published - 1 Dec 2019

Bibliographical note

Funding Information:
We thank Capt. D. Korte and his crew for the excellent support on board R/V Meteor during the Expedition M141/1. Without the great help on board of T. Schott, K. Meier, E. Horstmann, and T. Lux this study would not have been possible. We gratefully thank our colleagues B. Domeyer, A. Bleyer, R. Surberg, A. Bodenbinder, and A. Kolevica for their help in the shore-based laboratories at GEOMAR. We thank C. Faccenna, W. Bach, M. Ligi, B. Tutolo, and two anonymous reviewers for helpful comments. M141/1 was funded by the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium für Bildung und Forschung (BMBF) with additional support of FLOWS (EU-COST ES 1301). Data of this study can be found in the supporting information and can be accessed through the Pangaea data repository (https://doi.pangaea.de/10.1594/PANGAEA.907457).

Funding Information:
We thank Capt. D. Korte and his crew for the excellent support on board R/V during the Expedition M141/1. Without the great help on board of T. Schott, K. Meier, E. Horstmann, and T. Lux this study would not have been possible. We gratefully thank our colleagues B. Domeyer, A. Bleyer, R. Surberg, A. Bodenbinder, and A. Kolevica for their help in the shore‐based laboratories at GEOMAR. We thank C. Faccenna, W. Bach, M. Ligi, B. Tutolo, and two anonymous reviewers for helpful comments. M141/1 was funded by the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium für Bildung und Forschung (BMBF) with additional support of FLOWS (EU‐COST ES 1301). Data of this study can be found in the supporting information and can be accessed through the Pangaea data repository ( https://doi.pangaea.de/10.1594/PANGAEA.907457 ). Meteor

Publisher Copyright:
©2019. The Authors.

Funding

We thank Capt. D. Korte and his crew for the excellent support on board R/V Meteor during the Expedition M141/1. Without the great help on board of T. Schott, K. Meier, E. Horstmann, and T. Lux this study would not have been possible. We gratefully thank our colleagues B. Domeyer, A. Bleyer, R. Surberg, A. Bodenbinder, and A. Kolevica for their help in the shore-based laboratories at GEOMAR. We thank C. Faccenna, W. Bach, M. Ligi, B. Tutolo, and two anonymous reviewers for helpful comments. M141/1 was funded by the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium für Bildung und Forschung (BMBF) with additional support of FLOWS (EU-COST ES 1301). Data of this study can be found in the supporting information and can be accessed through the Pangaea data repository (https://doi.pangaea.de/10.1594/PANGAEA.907457). We thank Capt. D. Korte and his crew for the excellent support on board R/V during the Expedition M141/1. Without the great help on board of T. Schott, K. Meier, E. Horstmann, and T. Lux this study would not have been possible. We gratefully thank our colleagues B. Domeyer, A. Bleyer, R. Surberg, A. Bodenbinder, and A. Kolevica for their help in the shore‐based laboratories at GEOMAR. We thank C. Faccenna, W. Bach, M. Ligi, B. Tutolo, and two anonymous reviewers for helpful comments. M141/1 was funded by the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium für Bildung und Forschung (BMBF) with additional support of FLOWS (EU‐COST ES 1301). Data of this study can be found in the supporting information and can be accessed through the Pangaea data repository ( https://doi.pangaea.de/10.1594/PANGAEA.907457 ). Meteor

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Schmidt, C., Hensen, C., Wallmann, K., Liebetrau, V., Tatzel, M., Schurr, S. L., Kutterolf, S., Haffert, L., Geilert, S., Hübscher, C., Lebas, E., Heuser, A., Schmidt, M., Strauss, H., Vogl, J., & Hansteen, T. (2019). Origin of High Mg and SO₄ Fluids in Sediments of the Terceira Rift, Azores-Indications for Caminite Dissolution in a Waning Hydrothermal System. Geochemistry, Geophysics, Geosystems, 20(12), 6078-6094. https://doi.org/10.1029/2019GC008525

@article{16f0ff263ec9492c85a441fe72084773,

title = "Origin of High Mg and SO4 Fluids in Sediments of the Terceira Rift, Azores-Indications for Caminite Dissolution in a Waning Hydrothermal System",

abstract = "During R/V Meteor cruise 141/1, pore fluids of near surface sediments were investigated to find indications for hydrothermal activity in the Terceira Rift (TR), a hyperslow spreading center in the Central North Atlantic Ocean. To date, submarine hydrothermal fluid venting in the TR has only been reported for the D. Jo{\~a}o de Castro seamount, which presently seems to be inactive. Pore fluids sampled close to a volcanic cone at 2,800-m water depth show an anomalous composition with Mg, SO4, and total alkalinity concentrations significantly higher than seawater and a nearby reference core. The most straightforward way of interpreting these deviations is the dissolution of the hydrothermally formed mineral caminite (MgSO4 0.25 Mg (OH)2 0.2H2O). This interpretation is corroborated by a thorough investigation of fluid isotope systems (δ26Mg, δ30Si, δ34S, δ44/42Ca, and 87Sr/86Sr). Caminite is known from mineral assemblages with anhydrite and forms in hydrothermal recharge zones only under specific conditions such as high fluid temperatures and in altered oceanic crust, which are conditions generally met at the TR. We hypothesize that caminite was formed during hydrothermal activity and is now dissolving during the waning state of the hydrothermal system, so that caminite mineralization is shifted out of its stability zone. Ongoing fluid circulation through the basement is transporting the geochemical signal via slow advection toward the seafloor.",

author = "C. Schmidt and C. Hensen and K. Wallmann and V. Liebetrau and M. Tatzel and Schurr, {S. L.} and S. Kutterolf and L. Haffert and S. Geilert and C. H{\"u}bscher and E. Lebas and A. Heuser and M. Schmidt and H. Strauss and J. Vogl and T. Hansteen",

note = "Funding Information: We thank Capt. D. Korte and his crew for the excellent support on board R/V Meteor during the Expedition M141/1. Without the great help on board of T. Schott, K. Meier, E. Horstmann, and T. Lux this study would not have been possible. We gratefully thank our colleagues B. Domeyer, A. Bleyer, R. Surberg, A. Bodenbinder, and A. Kolevica for their help in the shore-based laboratories at GEOMAR. We thank C. Faccenna, W. Bach, M. Ligi, B. Tutolo, and two anonymous reviewers for helpful comments. M141/1 was funded by the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium f{\"u}r Bildung und Forschung (BMBF) with additional support of FLOWS (EU-COST ES 1301). Data of this study can be found in the supporting information and can be accessed through the Pangaea data repository (https://doi.pangaea.de/10.1594/PANGAEA.907457). Funding Information: We thank Capt. D. Korte and his crew for the excellent support on board R/V during the Expedition M141/1. Without the great help on board of T. Schott, K. Meier, E. Horstmann, and T. Lux this study would not have been possible. We gratefully thank our colleagues B. Domeyer, A. Bleyer, R. Surberg, A. Bodenbinder, and A. Kolevica for their help in the shore‐based laboratories at GEOMAR. We thank C. Faccenna, W. Bach, M. Ligi, B. Tutolo, and two anonymous reviewers for helpful comments. M141/1 was funded by the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium f{\"u}r Bildung und Forschung (BMBF) with additional support of FLOWS (EU‐COST ES 1301). Data of this study can be found in the supporting information and can be accessed through the Pangaea data repository ( https://doi.pangaea.de/10.1594/PANGAEA.907457 ). Meteor Publisher Copyright: {\textcopyright}2019. The Authors.",

year = "2019",

month = dec,

day = "1",

doi = "10.1029/2019GC008525",

language = "English",

volume = "20",

pages = "6078--6094",

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Schmidt, C, Hensen, C, Wallmann, K, Liebetrau, V, Tatzel, M, Schurr, SL, Kutterolf, S, Haffert, L, Geilert, S, Hübscher, C, Lebas, E, Heuser, A, Schmidt, M, Strauss, H, Vogl, J & Hansteen, T 2019, 'Origin of High Mg and SO₄ Fluids in Sediments of the Terceira Rift, Azores-Indications for Caminite Dissolution in a Waning Hydrothermal System', Geochemistry, Geophysics, Geosystems, vol. 20, no. 12, pp. 6078-6094. https://doi.org/10.1029/2019GC008525

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T1 - Origin of High Mg and SO4 Fluids in Sediments of the Terceira Rift, Azores-Indications for Caminite Dissolution in a Waning Hydrothermal System

AU - Schmidt, C.

AU - Hensen, C.

AU - Wallmann, K.

AU - Liebetrau, V.

AU - Tatzel, M.

AU - Schurr, S. L.

AU - Kutterolf, S.

AU - Haffert, L.

AU - Geilert, S.

AU - Hübscher, C.

AU - Lebas, E.

AU - Heuser, A.

AU - Schmidt, M.

AU - Strauss, H.

AU - Vogl, J.

AU - Hansteen, T.

N1 - Funding Information: We thank Capt. D. Korte and his crew for the excellent support on board R/V Meteor during the Expedition M141/1. Without the great help on board of T. Schott, K. Meier, E. Horstmann, and T. Lux this study would not have been possible. We gratefully thank our colleagues B. Domeyer, A. Bleyer, R. Surberg, A. Bodenbinder, and A. Kolevica for their help in the shore-based laboratories at GEOMAR. We thank C. Faccenna, W. Bach, M. Ligi, B. Tutolo, and two anonymous reviewers for helpful comments. M141/1 was funded by the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium für Bildung und Forschung (BMBF) with additional support of FLOWS (EU-COST ES 1301). Data of this study can be found in the supporting information and can be accessed through the Pangaea data repository (https://doi.pangaea.de/10.1594/PANGAEA.907457). Funding Information: We thank Capt. D. Korte and his crew for the excellent support on board R/V during the Expedition M141/1. Without the great help on board of T. Schott, K. Meier, E. Horstmann, and T. Lux this study would not have been possible. We gratefully thank our colleagues B. Domeyer, A. Bleyer, R. Surberg, A. Bodenbinder, and A. Kolevica for their help in the shore‐based laboratories at GEOMAR. We thank C. Faccenna, W. Bach, M. Ligi, B. Tutolo, and two anonymous reviewers for helpful comments. M141/1 was funded by the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium für Bildung und Forschung (BMBF) with additional support of FLOWS (EU‐COST ES 1301). Data of this study can be found in the supporting information and can be accessed through the Pangaea data repository ( https://doi.pangaea.de/10.1594/PANGAEA.907457 ). Meteor Publisher Copyright: ©2019. The Authors.

PY - 2019/12/1

Y1 - 2019/12/1

N2 - During R/V Meteor cruise 141/1, pore fluids of near surface sediments were investigated to find indications for hydrothermal activity in the Terceira Rift (TR), a hyperslow spreading center in the Central North Atlantic Ocean. To date, submarine hydrothermal fluid venting in the TR has only been reported for the D. João de Castro seamount, which presently seems to be inactive. Pore fluids sampled close to a volcanic cone at 2,800-m water depth show an anomalous composition with Mg, SO4, and total alkalinity concentrations significantly higher than seawater and a nearby reference core. The most straightforward way of interpreting these deviations is the dissolution of the hydrothermally formed mineral caminite (MgSO4 0.25 Mg (OH)2 0.2H2O). This interpretation is corroborated by a thorough investigation of fluid isotope systems (δ26Mg, δ30Si, δ34S, δ44/42Ca, and 87Sr/86Sr). Caminite is known from mineral assemblages with anhydrite and forms in hydrothermal recharge zones only under specific conditions such as high fluid temperatures and in altered oceanic crust, which are conditions generally met at the TR. We hypothesize that caminite was formed during hydrothermal activity and is now dissolving during the waning state of the hydrothermal system, so that caminite mineralization is shifted out of its stability zone. Ongoing fluid circulation through the basement is transporting the geochemical signal via slow advection toward the seafloor.

AB - During R/V Meteor cruise 141/1, pore fluids of near surface sediments were investigated to find indications for hydrothermal activity in the Terceira Rift (TR), a hyperslow spreading center in the Central North Atlantic Ocean. To date, submarine hydrothermal fluid venting in the TR has only been reported for the D. João de Castro seamount, which presently seems to be inactive. Pore fluids sampled close to a volcanic cone at 2,800-m water depth show an anomalous composition with Mg, SO4, and total alkalinity concentrations significantly higher than seawater and a nearby reference core. The most straightforward way of interpreting these deviations is the dissolution of the hydrothermally formed mineral caminite (MgSO4 0.25 Mg (OH)2 0.2H2O). This interpretation is corroborated by a thorough investigation of fluid isotope systems (δ26Mg, δ30Si, δ34S, δ44/42Ca, and 87Sr/86Sr). Caminite is known from mineral assemblages with anhydrite and forms in hydrothermal recharge zones only under specific conditions such as high fluid temperatures and in altered oceanic crust, which are conditions generally met at the TR. We hypothesize that caminite was formed during hydrothermal activity and is now dissolving during the waning state of the hydrothermal system, so that caminite mineralization is shifted out of its stability zone. Ongoing fluid circulation through the basement is transporting the geochemical signal via slow advection toward the seafloor.

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