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Geochemical
Transport :
A
model for the deposition of hydrothermal manganese near ridge crests (Abstract)
Problem
Description:
Hydrothermal
discharges are most associated with of black, gray, and white smoking
chimneys or vents, the colors of which stem from precipitation reactions
when hot, anoxic chemically-rich hydrothermal fluids mix with oxygen -rich,
cold sea water. The precipitate forming the black, gray, and white smoker
plume stems are relatively large in size and these settle to the sea floor
nearby. In other cases, particles are formed over longer time scales and
are other much smaller in size. Dissolved Fe, for example, converts to
colloidal-size particulate Fe over tens of hours. Dissolved hydrothermal
Mn is taken up by capsuled-bacteria the small ( ~ 1 um dia) bacteria over
times scales of weeks to months. Capsuled bacteria in turn are subject
to removal from the water column by larger, more rapidly sinking particles
that scavenge and drag the bacteria to the sea floor. In this study the
removal of hydrothermal Mn from the water column and its deposition in
the sediments in the proximity of the ridge crest has been examined.
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Weight
percent of Mn in sediments (triangles) at Juan de Fuca ridge are
superimposed on distributions of model Mn flux to sediments (curves)
for varying off-axis advection velocities.
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for larger view
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