Rebecca A. Neely
Molybdenum isotope behaviour in groundwaters and terrestrial hydrothermal systems, Iceland
Neely, Rebecca A.; Gislason, Sigurdur R.; Ólafsson, Magnus; McCoy-West, Alex J.; Pearce, Christopher R.; Burton, Kevin W.
Authors
Sigurdur R. Gislason
Magnus Ólafsson
Alex J. McCoy-West
Christopher R. Pearce
Professor Kevin Burton kevin.burton@durham.ac.uk
Professor
Abstract
Molybdenum (Mo) isotopes have proved useful in the reconstruction of paleoredox conditions. Their application generally relies upon a simplified model of ocean inputs in which rivers dominate Mo fluxes to the oceans and hydrothermal fluids are considered to be a minor contribution. To date, however, little attention has been paid to the extent of Mo isotope variation of hydrothermal waters, or to the potential effect of direct groundwater discharge to the oceans. Here we present Mo isotope data for two Icelandic groundwater systems (Mývatn and Þeistareykir) that are both influenced by hydrothermal processes. Relative to NIST 3134 = +0.25‰, the cold (<10 °C) groundwaters (δ98/95MoGROUNDWATER = −0.15‰ to +0.47‰; ) show little, if any, fractionation from the host basalt (MoBASALT = +0.16‰ to −0.12‰) and are, on average, lighter than both global and Icelandic rivers. In contrast, waters that are hydrothermally influenced (>10 °C) possess isotopically heavy δ98/95MoHYDROTHERMAL values of +0.25‰ to +2.06‰ with the possibility that the high temperature endmembers are even heavier. Although the mechanisms driving this fractionation remain unresolved, the incongruent dissolution of the host basalt and both the dissolution and precipitation of sulfides are considered. Regardless of the processes driving these variations, the δ98Mo data presented in this study indicate that groundwater and hydrothermal waters have the potential to modify ocean budget calculations.
Citation
Neely, R. A., Gislason, S. R., Ólafsson, M., McCoy-West, A. J., Pearce, C. R., & Burton, K. W. (2018). Molybdenum isotope behaviour in groundwaters and terrestrial hydrothermal systems, Iceland. Earth and Planetary Science Letters, 486, 108-118. https://doi.org/10.1016/j.epsl.2017.11.053
Journal Article Type | Article |
---|---|
Acceptance Date | Nov 28, 2017 |
Online Publication Date | Jan 28, 2018 |
Publication Date | Mar 15, 2018 |
Deposit Date | Apr 4, 2018 |
Publicly Available Date | Jan 28, 2019 |
Journal | Earth and Planetary Science Letters |
Print ISSN | 0012-821X |
Publisher | Elsevier |
Peer Reviewed | Peer Reviewed |
Volume | 486 |
Pages | 108-118 |
DOI | https://doi.org/10.1016/j.epsl.2017.11.053 |
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http://creativecommons.org/licenses/by-nc-nd/4.0/
Copyright Statement
© 2018 This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
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