Sulfate (re-)cycling in the oceanic crust: Effects of seawater-rock interaction, sulfur reduction and temperature on the abundance and isotope composition of anhydrite

Barbara I. Kleine; Andri Stefánsson; Robert A. Zierenberg; Heejin Jeon; Martin J. Whitehouse; Kristján Jónasson; Gudmundur Fridleifsson; Tobias B. Weisenberger

doi:10.1016/j.gca.2021.10.016

Sulfate (re-)cycling in the oceanic crust: Effects of seawater-rock interaction, sulfur reduction and temperature on the abundance and isotope composition of anhydrite

Barbara I. Kleine^*, Andri Stefánsson, Robert A. Zierenberg, Heejin Jeon, Martin J. Whitehouse, Kristján Jónasson, Gudmundur Fridleifsson, Tobias B. Weisenberger

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

At mid-ocean ridges (MORs), seawater carrying dissolved sulfate (SO₄) infiltrates the oceanic crust. Hydrothermal fluid emissions from such systems have much lower δ³⁴S and sulfur is mostly present as reduced sulfide, albeit in lower total sulfur concentrations than in seawater. This has been explained by anhydrite formation and sulfate reduction based on petrographic evidence and mass balance considerations. Here, we utilize the chemical and stable isotope (δ³⁴S, δ¹⁸O) systematics in natural anhydrite and pyrite from various locations along the submarine and on-land section of the Mid-Atlantic ridge near Iceland to quantify the key variables that control anhydrite formation and sulfate recycling in the oceanic crust. Hydrothermal anhydrite exhibited δ³⁴S values of +20.6 ± 1.0‰ and δ¹⁸O values between +2.4 to +25.3‰. Volcanogenic anhydrite in encrustations showed δ³⁴S values of −1.7 to +21.4‰ and δ¹⁸O values between +1.4 and +38.0‰. Hydrothermal pyrite exhibited δ³⁴S values ranging from +3.4 and +19.7‰. Comparison of the natural dataset with results from geochemical isotope modelling revealed that δ³⁴S and δ¹⁸O values of anhydrite and pyrite were dependent on the isotope composition of the source fluid, extent of water–rock interaction, temperature, and redox conditions. Departures of δ³⁴S and δ¹⁸O values in anhydrite from the source fluid were caused by progressive fluid-basalt interaction where lower δ³⁴S and δ¹⁸O values reflected a change in sources of S and O from solely fluid to basaltic origin. The δ¹⁸O values of anhydrite were additionally affected by temperature. Quantitative formation of anhydrite mainly occurred at temperatures < 150 °C, whereas at elevated temperatures (>200 °C) reduction of seawater-sulfate to H₂S and subsequent pyrite precipitation were found to limit anhydrite formation. Extending our calculations to the oceanic crust revealed that the majority of seawater-sulfate is sequestered into anhydrite (3–38 Tg S yr⁻¹) in vicinity of MORs at < 200 °C at shallow depth (<1500 m), with only a small portion of seawater-derived SO₄ discharged by high-temperature hydrothermal vents (0.1–3.4 Tg S yr⁻¹). However, sequestration of sulfur by anhydrite is not long-lasting due to retrograde dissolution of anhydrite. The removal of anhydrite upon cooling and aging of the crust may result in a return back to the oceans of 10–60% of the sulfur originally sequestered in anhydrite upon hydrothermal alteration in vicinity of MORs.

Original language	English
Pages (from-to)	65-90
Number of pages	26
Journal	Geochimica et Cosmochimica Acta
Volume	317
DOIs	https://doi.org/10.1016/j.gca.2021.10.016
Publication status	Published - 1 Jan 2022

Bibliographical note

Funding Information:
This project was financially supported by the University of Iceland Recruitment fund, the. International Continental Scientific Drilling Program (ICDP) through a grant to the SUSTAIN project, the Icelandic Science Fund, ICF-RANNÍS (project number: 163083-051), the Bergen Research Foundation and K.G. Jebsen Centre for Deep Sea Research at University of Bergen, Norway, the German Research Foundation (DFG), and DiSTAR, Federico II, University of Naples, Federico II, Italy. The University of Utah, USA and the two Icelandic power companies Reykjavík Energy and Landsvirkjun, contributed additional funds. HS Orka kindly provided access to the drill cuttings and core at Reykjanes. G.H. Gudfinnsson, H. Jeon and K. Lindén are thanked for assistance during sample preparation and data acquisition. We would like to thank J. G. Catalano and D.A.H. Teagle for careful editorial handling and three anonymous reviewers for their constructive reviews which significantly improved this study. This is NordSIMS contribution #692.

Funding Information:
This project was financially supported by the University of Iceland Recruitment fund, the. International Continental Scientific Drilling Program (ICDP) through a grant to the SUSTAIN project, the Icelandic Science Fund, ICF-RANNÍS (project number: 163083-051), the Bergen Research Foundation and K.G. Jebsen Centre for Deep Sea Research at University of Bergen, Norway, the German Research Foundation (DFG), and DiSTAR, Federico II, University of Naples, Federico II, Italy. The University of Utah, USA and the two Icelandic power companies Reykjavík Energy and Landsvirkjun, contributed additional funds. HS Orka kindly provided access to the drill cuttings and core at Reykjanes. G.H. Gudfinnsson, H. Jeon and K. Lindén are thanked for assistance during sample preparation and data acquisition. We would like to thank J. G. Catalano and D.A.H. Teagle for careful editorial handling and three anonymous reviewers for their constructive reviews which significantly improved this study. This is NordSIMS contribution #692.

Publisher Copyright:
© 2021 Elsevier Ltd

Other keywords

Anhydrite
Fluid-rock interaction
Mid-Atlantic ridge
Oceanic crust
Oxygen isotopes
Reaction path modelling
Sulfur isotopes

Access to Document

10.1016/j.gca.2021.10.016Licence: Unspecified

Cite this

Kleine, B. I., Stefánsson, A., Zierenberg, R. A., Jeon, H., Whitehouse, M. J., Jónasson, K., Fridleifsson, G., & Weisenberger, T. B. (2022). Sulfate (re-)cycling in the oceanic crust: Effects of seawater-rock interaction, sulfur reduction and temperature on the abundance and isotope composition of anhydrite. Geochimica et Cosmochimica Acta, 317, 65-90. https://doi.org/10.1016/j.gca.2021.10.016

@article{1b1ac15d3b11483bad72c87f0efd6134,

title = "Sulfate (re-)cycling in the oceanic crust: Effects of seawater-rock interaction, sulfur reduction and temperature on the abundance and isotope composition of anhydrite",

abstract = "At mid-ocean ridges (MORs), seawater carrying dissolved sulfate (SO4) infiltrates the oceanic crust. Hydrothermal fluid emissions from such systems have much lower δ34S and sulfur is mostly present as reduced sulfide, albeit in lower total sulfur concentrations than in seawater. This has been explained by anhydrite formation and sulfate reduction based on petrographic evidence and mass balance considerations. Here, we utilize the chemical and stable isotope (δ34S, δ18O) systematics in natural anhydrite and pyrite from various locations along the submarine and on-land section of the Mid-Atlantic ridge near Iceland to quantify the key variables that control anhydrite formation and sulfate recycling in the oceanic crust. Hydrothermal anhydrite exhibited δ34S values of +20.6 ± 1.0‰ and δ18O values between +2.4 to +25.3‰. Volcanogenic anhydrite in encrustations showed δ34S values of −1.7 to +21.4‰ and δ18O values between +1.4 and +38.0‰. Hydrothermal pyrite exhibited δ34S values ranging from +3.4 and +19.7‰. Comparison of the natural dataset with results from geochemical isotope modelling revealed that δ34S and δ18O values of anhydrite and pyrite were dependent on the isotope composition of the source fluid, extent of water–rock interaction, temperature, and redox conditions. Departures of δ34S and δ18O values in anhydrite from the source fluid were caused by progressive fluid-basalt interaction where lower δ34S and δ18O values reflected a change in sources of S and O from solely fluid to basaltic origin. The δ18O values of anhydrite were additionally affected by temperature. Quantitative formation of anhydrite mainly occurred at temperatures < 150 °C, whereas at elevated temperatures (>200 °C) reduction of seawater-sulfate to H2S and subsequent pyrite precipitation were found to limit anhydrite formation. Extending our calculations to the oceanic crust revealed that the majority of seawater-sulfate is sequestered into anhydrite (3–38 Tg S yr−1) in vicinity of MORs at < 200 °C at shallow depth (<1500 m), with only a small portion of seawater-derived SO4 discharged by high-temperature hydrothermal vents (0.1–3.4 Tg S yr−1). However, sequestration of sulfur by anhydrite is not long-lasting due to retrograde dissolution of anhydrite. The removal of anhydrite upon cooling and aging of the crust may result in a return back to the oceans of 10–60% of the sulfur originally sequestered in anhydrite upon hydrothermal alteration in vicinity of MORs.",

keywords = "Anhydrite, Fluid-rock interaction, Mid-Atlantic ridge, Oceanic crust, Oxygen isotopes, Reaction path modelling, Sulfur isotopes",

author = "Kleine, {Barbara I.} and Andri Stef{\'a}nsson and Zierenberg, {Robert A.} and Heejin Jeon and Whitehouse, {Martin J.} and Kristj{\'a}n J{\'o}nasson and Gudmundur Fridleifsson and Weisenberger, {Tobias B.}",

note = "Funding Information: This project was financially supported by the University of Iceland Recruitment fund, the. International Continental Scientific Drilling Program (ICDP) through a grant to the SUSTAIN project, the Icelandic Science Fund, ICF-RANN{\'I}S (project number: 163083-051), the Bergen Research Foundation and K.G. Jebsen Centre for Deep Sea Research at University of Bergen, Norway, the German Research Foundation (DFG), and DiSTAR, Federico II, University of Naples, Federico II, Italy. The University of Utah, USA and the two Icelandic power companies Reykjav{\'i}k Energy and Landsvirkjun, contributed additional funds. HS Orka kindly provided access to the drill cuttings and core at Reykjanes. G.H. Gudfinnsson, H. Jeon and K. Lind{\'e}n are thanked for assistance during sample preparation and data acquisition. We would like to thank J. G. Catalano and D.A.H. Teagle for careful editorial handling and three anonymous reviewers for their constructive reviews which significantly improved this study. This is NordSIMS contribution #692. Funding Information: This project was financially supported by the University of Iceland Recruitment fund, the. International Continental Scientific Drilling Program (ICDP) through a grant to the SUSTAIN project, the Icelandic Science Fund, ICF-RANN{\'I}S (project number: 163083-051), the Bergen Research Foundation and K.G. Jebsen Centre for Deep Sea Research at University of Bergen, Norway, the German Research Foundation (DFG), and DiSTAR, Federico II, University of Naples, Federico II, Italy. The University of Utah, USA and the two Icelandic power companies Reykjav{\'i}k Energy and Landsvirkjun, contributed additional funds. HS Orka kindly provided access to the drill cuttings and core at Reykjanes. G.H. Gudfinnsson, H. Jeon and K. Lind{\'e}n are thanked for assistance during sample preparation and data acquisition. We would like to thank J. G. Catalano and D.A.H. Teagle for careful editorial handling and three anonymous reviewers for their constructive reviews which significantly improved this study. This is NordSIMS contribution #692. Publisher Copyright: {\textcopyright} 2021 Elsevier Ltd",

year = "2022",

month = jan,

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doi = "10.1016/j.gca.2021.10.016",

language = "English",

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Kleine, BI, Stefánsson, A, Zierenberg, RA, Jeon, H, Whitehouse, MJ, Jónasson, K, Fridleifsson, G & Weisenberger, TB 2022, 'Sulfate (re-)cycling in the oceanic crust: Effects of seawater-rock interaction, sulfur reduction and temperature on the abundance and isotope composition of anhydrite', Geochimica et Cosmochimica Acta, vol. 317, pp. 65-90. https://doi.org/10.1016/j.gca.2021.10.016

Sulfate (re-)cycling in the oceanic crust: Effects of seawater-rock interaction, sulfur reduction and temperature on the abundance and isotope composition of anhydrite. / Kleine, Barbara I.; Stefánsson, Andri; Zierenberg, Robert A. et al.
In: Geochimica et Cosmochimica Acta, Vol. 317, 01.01.2022, p. 65-90.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Sulfate (re-)cycling in the oceanic crust

T2 - Effects of seawater-rock interaction, sulfur reduction and temperature on the abundance and isotope composition of anhydrite

AU - Kleine, Barbara I.

AU - Stefánsson, Andri

AU - Zierenberg, Robert A.

AU - Jeon, Heejin

AU - Whitehouse, Martin J.

AU - Jónasson, Kristján

AU - Fridleifsson, Gudmundur

AU - Weisenberger, Tobias B.

N1 - Funding Information: This project was financially supported by the University of Iceland Recruitment fund, the. International Continental Scientific Drilling Program (ICDP) through a grant to the SUSTAIN project, the Icelandic Science Fund, ICF-RANNÍS (project number: 163083-051), the Bergen Research Foundation and K.G. Jebsen Centre for Deep Sea Research at University of Bergen, Norway, the German Research Foundation (DFG), and DiSTAR, Federico II, University of Naples, Federico II, Italy. The University of Utah, USA and the two Icelandic power companies Reykjavík Energy and Landsvirkjun, contributed additional funds. HS Orka kindly provided access to the drill cuttings and core at Reykjanes. G.H. Gudfinnsson, H. Jeon and K. Lindén are thanked for assistance during sample preparation and data acquisition. We would like to thank J. G. Catalano and D.A.H. Teagle for careful editorial handling and three anonymous reviewers for their constructive reviews which significantly improved this study. This is NordSIMS contribution #692. Funding Information: This project was financially supported by the University of Iceland Recruitment fund, the. International Continental Scientific Drilling Program (ICDP) through a grant to the SUSTAIN project, the Icelandic Science Fund, ICF-RANNÍS (project number: 163083-051), the Bergen Research Foundation and K.G. Jebsen Centre for Deep Sea Research at University of Bergen, Norway, the German Research Foundation (DFG), and DiSTAR, Federico II, University of Naples, Federico II, Italy. The University of Utah, USA and the two Icelandic power companies Reykjavík Energy and Landsvirkjun, contributed additional funds. HS Orka kindly provided access to the drill cuttings and core at Reykjanes. G.H. Gudfinnsson, H. Jeon and K. Lindén are thanked for assistance during sample preparation and data acquisition. We would like to thank J. G. Catalano and D.A.H. Teagle for careful editorial handling and three anonymous reviewers for their constructive reviews which significantly improved this study. This is NordSIMS contribution #692. Publisher Copyright: © 2021 Elsevier Ltd

PY - 2022/1/1

Y1 - 2022/1/1

N2 - At mid-ocean ridges (MORs), seawater carrying dissolved sulfate (SO4) infiltrates the oceanic crust. Hydrothermal fluid emissions from such systems have much lower δ34S and sulfur is mostly present as reduced sulfide, albeit in lower total sulfur concentrations than in seawater. This has been explained by anhydrite formation and sulfate reduction based on petrographic evidence and mass balance considerations. Here, we utilize the chemical and stable isotope (δ34S, δ18O) systematics in natural anhydrite and pyrite from various locations along the submarine and on-land section of the Mid-Atlantic ridge near Iceland to quantify the key variables that control anhydrite formation and sulfate recycling in the oceanic crust. Hydrothermal anhydrite exhibited δ34S values of +20.6 ± 1.0‰ and δ18O values between +2.4 to +25.3‰. Volcanogenic anhydrite in encrustations showed δ34S values of −1.7 to +21.4‰ and δ18O values between +1.4 and +38.0‰. Hydrothermal pyrite exhibited δ34S values ranging from +3.4 and +19.7‰. Comparison of the natural dataset with results from geochemical isotope modelling revealed that δ34S and δ18O values of anhydrite and pyrite were dependent on the isotope composition of the source fluid, extent of water–rock interaction, temperature, and redox conditions. Departures of δ34S and δ18O values in anhydrite from the source fluid were caused by progressive fluid-basalt interaction where lower δ34S and δ18O values reflected a change in sources of S and O from solely fluid to basaltic origin. The δ18O values of anhydrite were additionally affected by temperature. Quantitative formation of anhydrite mainly occurred at temperatures < 150 °C, whereas at elevated temperatures (>200 °C) reduction of seawater-sulfate to H2S and subsequent pyrite precipitation were found to limit anhydrite formation. Extending our calculations to the oceanic crust revealed that the majority of seawater-sulfate is sequestered into anhydrite (3–38 Tg S yr−1) in vicinity of MORs at < 200 °C at shallow depth (<1500 m), with only a small portion of seawater-derived SO4 discharged by high-temperature hydrothermal vents (0.1–3.4 Tg S yr−1). However, sequestration of sulfur by anhydrite is not long-lasting due to retrograde dissolution of anhydrite. The removal of anhydrite upon cooling and aging of the crust may result in a return back to the oceans of 10–60% of the sulfur originally sequestered in anhydrite upon hydrothermal alteration in vicinity of MORs.

AB - At mid-ocean ridges (MORs), seawater carrying dissolved sulfate (SO4) infiltrates the oceanic crust. Hydrothermal fluid emissions from such systems have much lower δ34S and sulfur is mostly present as reduced sulfide, albeit in lower total sulfur concentrations than in seawater. This has been explained by anhydrite formation and sulfate reduction based on petrographic evidence and mass balance considerations. Here, we utilize the chemical and stable isotope (δ34S, δ18O) systematics in natural anhydrite and pyrite from various locations along the submarine and on-land section of the Mid-Atlantic ridge near Iceland to quantify the key variables that control anhydrite formation and sulfate recycling in the oceanic crust. Hydrothermal anhydrite exhibited δ34S values of +20.6 ± 1.0‰ and δ18O values between +2.4 to +25.3‰. Volcanogenic anhydrite in encrustations showed δ34S values of −1.7 to +21.4‰ and δ18O values between +1.4 and +38.0‰. Hydrothermal pyrite exhibited δ34S values ranging from +3.4 and +19.7‰. Comparison of the natural dataset with results from geochemical isotope modelling revealed that δ34S and δ18O values of anhydrite and pyrite were dependent on the isotope composition of the source fluid, extent of water–rock interaction, temperature, and redox conditions. Departures of δ34S and δ18O values in anhydrite from the source fluid were caused by progressive fluid-basalt interaction where lower δ34S and δ18O values reflected a change in sources of S and O from solely fluid to basaltic origin. The δ18O values of anhydrite were additionally affected by temperature. Quantitative formation of anhydrite mainly occurred at temperatures < 150 °C, whereas at elevated temperatures (>200 °C) reduction of seawater-sulfate to H2S and subsequent pyrite precipitation were found to limit anhydrite formation. Extending our calculations to the oceanic crust revealed that the majority of seawater-sulfate is sequestered into anhydrite (3–38 Tg S yr−1) in vicinity of MORs at < 200 °C at shallow depth (<1500 m), with only a small portion of seawater-derived SO4 discharged by high-temperature hydrothermal vents (0.1–3.4 Tg S yr−1). However, sequestration of sulfur by anhydrite is not long-lasting due to retrograde dissolution of anhydrite. The removal of anhydrite upon cooling and aging of the crust may result in a return back to the oceans of 10–60% of the sulfur originally sequestered in anhydrite upon hydrothermal alteration in vicinity of MORs.

KW - Anhydrite

KW - Fluid-rock interaction

KW - Mid-Atlantic ridge

KW - Oceanic crust

KW - Oxygen isotopes

KW - Reaction path modelling

KW - Sulfur isotopes

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U2 - 10.1016/j.gca.2021.10.016

DO - 10.1016/j.gca.2021.10.016

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AN - SCOPUS:85119121206

SN - 0016-7037

VL - 317

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EP - 90

JO - Geochimica et Cosmochimica Acta

JF - Geochimica et Cosmochimica Acta

ER -

Sulfate (re-)cycling in the oceanic crust: Effects of seawater-rock interaction, sulfur reduction and temperature on the abundance and isotope composition of anhydrite

Abstract

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