Hydrothermal Plume Geochemistry along the East Lau Spreading Center

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Hydrothermal Plume Geochemistry along the East
Lau Spreading Center

• J A Resing, E Baker, F Martinez, N Buck, S
  Walker, J Seewald, G Proskurowski, J Lupton, G
  Wheat

Hydrothermal cell size Consistent with recent
observations of Tolstoy Modeling results of
Driesner and graduate students
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Two eruptions in the Northern Lau Basin North
East Lau Spreading Center West Mata Volcano

• Joe Resing, John Lupton, Ed Baker, Bob Embley,
  Marv Lilley,
• Sharon Walker, Susan Merle, Ron Greene
• Cruise Participants
• Gwen Hemery, Tamara Baumberger, Lucia Upchurch,
  Nick Dyriw, Peter Crowhurst, Jelena Puzic

Funding provided by The NOAA VENTS program NOAA
Ship Charter funds
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• Eruption along NELSC November 20
• Eruption West Mata November 26
• Incredible thanks to
• Geoff Lebon for SEM work (PMEL Carbon)
• Dana Greely for CO2 (PMEL Carbon)
• Ron Greene 3He
• Nathan Buck Trace metals
• Dave Butterfield Sulfate

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Tafu
Ridge eruption Near bottom T anomalies
Maka
Vertical Cast
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Ridge
Mata
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Large field view showing only shards
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Glass shards from lavas
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Quartz Shard
Alteration Phase
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NELSC eruption

• Elevated hydrogen coincident with glass shards
  implicates molten lava-seawater contact to form
  shallow plume.
• Hydrothermal particles may implicate dike
  emplacement into relic hydrothermal deposits.
• How will magmatic volatiles evolve, especially
  Sulfur, CO2 and Methane.

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Particles Dominated by sulfur and
Fe-oxyhydroxides
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Ca
Mg
S
Fe
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Mg
Si
Fe
Fe
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CO2 to 3He 8.6 X109 R/Ra 7.19
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Change in CO2 to change in pH demonstrates
fluids rich in both CO2 and acid.
slope 250 CO2 slope 360
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Change in CO2 to change in pH demonstrates
fluids rich in both CO2 and acid.
slope 250 CO2 slope 360
Sulfate anaylisis and sulfur abundance indicate
sulfurous acid. Absence of Al-sulfate
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W. Mata

• Boninitic Eruption?
• First observation of such
• Consistent with Boninites dredged by Faloon et
  al. (2007) in the region
• Is this incipient arc volcanism?
• Is this the forearc?
• Backscatter suggests a long lived and ongoing
  eruption.
• As this volcano/hydrothermal system evolves will
  the mafic source rocks continue to produce
  hydrogen and will this be reflected in the
  microbial population?
• Are the other volcanoes nearby active?

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Conclusions

• Two ongoing eruptions very close to one another
• W. Mata Arc like
• NELSC MOR-like
• Presence of Hydrogen and glass shards above NELSC
  eruption has implications about mega-plume
  formation and thus heat flux from the ridge crest
• Presence of Mg rich shards, hydrothermal
  precipitates, and leach products suggest an
  active Boninitic eruption (consistent with
  findings of Faloon et al., 2007)
• Extaordinarily high hydrogen must reflect both
  molten material and the ultra-mafic source rocks.
• Incredible opportunity for further study.

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