The role of iron and manganese in elucidating the temperature of subseafloor hydrothermal reactions: insights from experimental and field data
2012-11
Loading...
View/Download File
Persistent link to this item
Statistics
View StatisticsJournal Title
Journal ISSN
Volume Title
Title
The role of iron and manganese in elucidating the temperature of subseafloor hydrothermal reactions: insights from experimental and field data
Authors
Published Date
2012-11
Publisher
Type
Thesis or Dissertation
Abstract
Field/experimental investigations demonstrate the chemistry of mid-ocean ridge
hydrothermal fluids reflects fluid-mineral reaction at temperatures higher than typically measured
at the seafloor. In order to better constrain sub-seafloor hydrothermal processes, we have
developed an empirical geothermometer based on the dissolved Fe/Mn ratio in high-temperature
fluids. Using data from basalt alteration experiments, the relationship; T(°C) = 331.24 +
112.41*log[Fe/Mn] has been calibrated between 350 °C and 450 °C. The apparent Fe-Mn
equilibrium demonstrated by the experimental data is in good agreement with natural vent fluids,
suggesting broad applicability. When used in conjunction with constraints imposed by quartz
solubility, associated sub-seafloor pressures can be estimated for basalt-hosted systems. This
methodology is used to interpret new data from 13°N on the East Pacific Rise (EPR) and the
Lucky Strike Seamount on the Mid-Atlantic Ridge where high-temperature fluids both enriched
and depleted in chloride, relative to seawater, are actively venting within a close proximity.
Accounting for these variable salinities, phase separation is also a dominant process affecting the
chemistry of hydrothermal fluids; and vapor-liquid partition coefficients for accessory metals
(Na-normalized as NaCl dictates phase equilibria) have therefore been experimentally derived for
temperature between 360 and 460 °C, where those > Na represent increasing affinity for the
liquid phase. These data reveal the relationship Cu(I) < Na < Fe(II) < Zn < Ni(II) ≤ Mg ≤ Mn(II)
< Co(II) < Ca < Sr < Ba and a dependence on the cationic radii. The depth below seafloor of the
magmatic heat source at Lucky Strike is greater than that of faster spreading systems such as EPR
9-13°N, which host higher temperature vents with greater transition metal concentrations. The
combined experimental/field data suggest the resulting increased residence time in the up-flow
zone allows re-equilibration at temperatures lower than those resulting in phase separation. Fluid
chemistry measured in the immediate aftermath of eruptions at EPR 9-10°N conversely shows
large deviations from Fe/Mn equilibrium consistent with partitioning due to phase separation. The
eruptive data also exhibit that P-T conditions were sufficiently extreme that Fe is behaving in a
volatile manner observed in the experiments and in some instances subseafloor halite saturation may have occurred.
Description
University of Minnesota Ph.D. dissertation. November 2012. Major: Geology. Advisor: William E. Seyfried, Jr. 1 computer file (PDF); ix, 130 pages.
Related to
Replaces
License
Collections
Series/Report Number
Funding information
Isbn identifier
Doi identifier
Previously Published Citation
Suggested citation
Pester, Nicholas Jon. (2012). The role of iron and manganese in elucidating the temperature of subseafloor hydrothermal reactions: insights from experimental and field data. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/151483.
Content distributed via the University Digital Conservancy may be subject to additional license and use restrictions applied by the depositor. By using these files, users agree to the Terms of Use. Materials in the UDC may contain content that is disturbing and/or harmful. For more information, please see our statement on harmful content in digital repositories.