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., and Burton, Kevin W. (2018) Molybdenum isotope behaviour in groundwaters and terrestrial hydrothermal systems, Iceland. Earth and Planetary Science Letters, 486. pp. 108-118.

[img] PDF (Published Version) - Published Version
Restricted to Repository staff only

View at Publisher Website: https://doi.org/10.1016/j.epsl.2017.11.0...
19


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‰; n=13) show little, if any, fractionation from the host basalt (δ98/95MoBASALT = +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‰ (n=18) 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.

Item ID: 65071
Item Type: Article (Research - C1)
ISSN: 1385-013X
Keywords: groundwater, hydrothermal, Mo isotopes, ocean mass balance
Copyright Information: © 2018 Elsevier B.V. All rights reserved.
Funders: Initial Training Network, MetTrans (MT)
Projects and Grants: MT grant number 290336
Date Deposited: 17 Dec 2020 03:08
FoR Codes: 37 EARTH SCIENCES > 3703 Geochemistry > 370302 Inorganic geochemistry @ 20%
37 EARTH SCIENCES > 3703 Geochemistry > 370303 Isotope geochemistry @ 50%
37 EARTH SCIENCES > 3707 Hydrology > 370703 Groundwater hydrology @ 30%
SEO Codes: 85 ENERGY > 8505 Renewable Energy > 850502 Geothermal Energy @ 50%
97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 50%
More Statistics

Actions (Repository Staff Only)

Item Control Page Item Control Page