Antarctic Hydrothemal Vents and Plate Tectonics

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Antarctic Hydrothemal Vents and Plate Tectonics

• Steven Stevenoski

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Principle Investigators
Dr. Gary Klinkhammer Oregon State
University Marine Geophysics
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Principle Investigators
Dr. Larry Lawver University of Texas Institute
for Geophysics Marine Geophysics
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Why Look For Vents in Antarctica?
Plates Project - UTIG
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What are Vents?

• Located near regions of seafloor spreading.
• Locations where porous rock is in contact with
  the mantle.
• Areas where superheated water in contact with the
  mantle is released through the crust.
• A plume of dissolved minerals that precipitate
  rapidly in the water column.

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• When hot (350-400 deg C) chemically enriched
  fluids first emerge from a hydrothermal vent they
  are buoyant because they are hotter than the
  typical deep-ocean (about 2 deg C).

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• They are also saturated with all kinds of
  minerals which start to precipitate as soon as
  the fluid is cooled forming thick rising plumes
  of blue-black sulfide mineral smoke - hence
  their common name of 'black smokers'.

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• The plume that forms above any hydrothermal vent
  can typically rise 100-300m up above the seafloor
  before it is diluted enough and it no longer goes
  on rising.

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• Typically, by this stage, the water which reaches
  this non-buoyant stage represents a 10,0001
  dilution of vent-fluid with ordinary seawater
  which has been mixed in during the turbulent
  ascent of the plume.

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• Fortunately many of the chemicals in vent-fluids
  are concentrated up to 1 million times more
  strongly than ordinary seawater - so even after
  all that dilution they still contain 100 times
  more material than ordinary seawater.

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• These plumes spread out over kilometers and even
  tens of kilometers downstream from any vent-field
  - our record at present is about 50km from the
  source.

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Where do you look for vents in Antarctica?
Bransfield Straight
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• ZAPS, or zero angle photon spectrometer, has been
  used to look for Antarctic vents. The fiber optic
  spectrometer gives scientists a true picture of
  chemical changes in water over time.

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• Dählmann, A., Wallmann, K., Sahling, H., Sarthou,
  G., Bohrmann, G., Petersen, S., Chin, C.,
  Klinkhammer, G. Hot vents in an ice-cold ocean
  Indications for phase separation at the
  southernmost area of hydrothermal activity,
  Bransfield Strait, Antarctica, Earth Planet. Sci.
  Lett. 193 (3-4), 381-394 (2001)