Antarctic Hydrothemal Vents and Plate Tectonics Steven Stevenoski

Principle Investigators Dr. Gary Klinkhammer Oregon State University Marine Geophysics

Principle Investigators Dr. Larry Lawver University of Texas Institute for Geophysics Marine Geophysics

Why Look For Vents in Antarctica?

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.

When hot ( 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).

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'.

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

Typically, by this stage, the water which reaches this non- buoyant stage represents a 10,000:1 dilution of vent-fluid with ordinary seawater which has been mixed in during the turbulent ascent of the plume.

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.

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.

Where do you look for vents in Antarctica?

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.

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), (2001)