Isotopic composition of gypsum in the Macquarie Island ophiolite: implications for the sulfur cycle and the subsurface biosphere in oceanic crust
Isotopic composition of gypsum in the Macquarie Island ophiolite: implications for the sulfur cycle and the subsurface biosphere in oceanic crust
The O, S, and Sr isotope compositions were determined for 17 samples of gypsum that replaced anhydrite in the sheeted-dike complex of the Macquarie Island ophiolite. Elevated ?34S (26.2‰–29.0‰) and ?18O values (12.5‰–14.4‰) of gypsum compared to those of seawater sulfate are the result of microbial sulfate reduction. Low organic carbon contents and little sulfate reduction in sediments, plus a large basaltic Sr component in the gypsum (87Sr/86Sr = 0.70446–0.70524), indicate that the sulfate source was not pore waters in the overlying sediment. Low ?34S values of sulfide in basalt lavas are consistent with microbial reduction of seawater sulfate within the volcanic rocks. Tectonic activity at the slow-spreading ridge allowed evolved formation waters to enter hot sheeted-dike complex basement, resulting in heating and precipitation of anhydrite. Results show that microbes can leave geochemical tracers of their activity in oceanic basement and that anhydrite can be preserved in oceanic crust and may be of significance for the oceanic sulfur budget.
sulfates, hydrothermal processes, bacteria, biosphere, mid-ocean ridges.
549-552
Alt, J.C.
15bc6ffe-26c5-4c34-bb91-f4d076811e28
Davidson, G.J.
8e435558-c844-47b9-8aa1-1645a79dcc73
Teagle, D.A.H.
396539c5-acbe-4dfa-bb9b-94af878fe286
Karson, J.A.
d14d9503-4268-46a7-bdd7-7899a496dde6
2003
Alt, J.C.
15bc6ffe-26c5-4c34-bb91-f4d076811e28
Davidson, G.J.
8e435558-c844-47b9-8aa1-1645a79dcc73
Teagle, D.A.H.
396539c5-acbe-4dfa-bb9b-94af878fe286
Karson, J.A.
d14d9503-4268-46a7-bdd7-7899a496dde6
Alt, J.C., Davidson, G.J., Teagle, D.A.H. and Karson, J.A.
(2003)
Isotopic composition of gypsum in the Macquarie Island ophiolite: implications for the sulfur cycle and the subsurface biosphere in oceanic crust.
Geology, 31 (6), .
(doi:10.1130/0091-7613(2003)031<0549:ICOGIT>2.0.CO;2).
Abstract
The O, S, and Sr isotope compositions were determined for 17 samples of gypsum that replaced anhydrite in the sheeted-dike complex of the Macquarie Island ophiolite. Elevated ?34S (26.2‰–29.0‰) and ?18O values (12.5‰–14.4‰) of gypsum compared to those of seawater sulfate are the result of microbial sulfate reduction. Low organic carbon contents and little sulfate reduction in sediments, plus a large basaltic Sr component in the gypsum (87Sr/86Sr = 0.70446–0.70524), indicate that the sulfate source was not pore waters in the overlying sediment. Low ?34S values of sulfide in basalt lavas are consistent with microbial reduction of seawater sulfate within the volcanic rocks. Tectonic activity at the slow-spreading ridge allowed evolved formation waters to enter hot sheeted-dike complex basement, resulting in heating and precipitation of anhydrite. Results show that microbes can leave geochemical tracers of their activity in oceanic basement and that anhydrite can be preserved in oceanic crust and may be of significance for the oceanic sulfur budget.
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Published date: 2003
Keywords:
sulfates, hydrothermal processes, bacteria, biosphere, mid-ocean ridges.
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Local EPrints ID: 2102
URI: http://eprints.soton.ac.uk/id/eprint/2102
ISSN: 0091-7613
PURE UUID: 5b407e6a-6761-4a69-b6ce-17f2f5bc27f1
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Date deposited: 11 May 2004
Last modified: 16 Mar 2024 03:14
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Author:
J.C. Alt
Author:
G.J. Davidson
Author:
J.A. Karson
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