Insights into sulfur isotope systematics: experimental constraints, applications, and future directi

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Insights into sulfur isotope systematicsexperime
ntal constraints, applications, and future
directions David T. Johnston Department of
Geology and ESSIC University of Maryland
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An initial observation
Photochemical control
Biological control
Compiled from Farquhar 2000, 2002, Mozjsis 2003,
Ono 2003, Bekker 2004, unpublished data
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Mass-dependent fractionations
systematics
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Mass-dependent fractionations
systematics
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Mass-dependent fractionations
systematics
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Mass-dependent fractionations
systematics
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Utility of using D33S notation
systematics
Similar for 36S
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Mass-dependent fractionations
systematics
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Mass-dependent fractionations
systematics
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An initial observation
Photochemical control
Biological control
Compiled from Farquhar 2000, 2002, Mozjsis 2003,
Ono 2003, Bekker 2004, unpublished data
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Consideration of d34S versus D33S large D33S
scale
systematics
Compiled from Farquhar 2000, 2002, Mozjsis 2003,
Ono 2003, Bekker 2004, unpublished data
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Consideration of d34S versus D33S small D33S
scale
systematics
Unpublished data
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Controls on surface fractionations biological
cycling
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Sulfate reducing bacteria
Experimental constraints
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Sulfate reducing bacteria
Experimental constraints
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Sulfate reducing bacteria
Experimental constraints
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Sulfate reducing bacteria
Experimental constraints
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Sulfate reducing bacteria
Experimental constraints
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Sulfur disproportionating bacteria
Experimental constraints
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Comparing metabolisms
Experimental constraints
Disproportionation data
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Context for environmental application
Application
D33 for the 34 record?
MDF MIF
Modified from Canfield, 2001
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Application
Focusing on samples in blue Proterozoic Sulfate
Johnston et al. (in review)
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Modeling framework and application of
experimental fractionation factors
Application
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Predicted seawater sulfate values All solutions
presented
Application
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Predicted seawater sulfate values general
solutions presented
Application
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Proterozoic sulfate record all Neoproterozoic
data
Application
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Proterozoic sulfate record all
Paleo/Mesoproterozoic data
Application
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Proterozoic sulfate record Society Cliffs Fm.
(1200 Ma)
Application
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Proterozoic sulfate record Dismal Lakes Gp.
(1300 Ma)
Application
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Proterozoic sulfate record Helena Fm. (1450 Ma)
Application
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Bracketing the oxidation of the surface?
Application
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Proterozoic sulfate record McNamara Fm. (1750
Ma)
Application
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Proterozoic sulfate record McNamara Fm. (1750
Ma) alternative interpretation
Application
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Modeling framework and application of
experimental fractionation factors
Application
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Future directions
Focusing on samples in pink Proterozoic Sulfides
Johnston et al. (in prep)
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Future directions
Predicted isotopic compositions of sulfate and
sulfide
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Future directions
Apparent inconsistency multi-step evolution?
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Future directions
Understanding two stage evolution
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Future directions
Possible solution. Alternatives?
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Photochemical control
Biological control
Compiled from Farquhar 2000, 2002, Mozjsis 2003,
Ono 2003, Bekker 2004, unpublished data