A model
for the deposition of hydrothermal manganese near ridge crests
Lavelle,
J.W., J.P. Cowen, and G.J. Massoth
Journal of Geophysical Research, 97(C5), 7413-7427 (1992)
Abstract:
A two-stage scavenging model is used to describe the transport of hydrothermal
Mn to the sediments adjacent to ridge crests. Dissolved Mn is hypothesized
to be scavenged by slowly settling metal-depositing capsuled bacteria which,
in turn, are incorporated into rapidly settling macroaggregates. Upon reaching
the seafloor, the Mn is subject to resuspension in particulate form and
to remobilization within the sediment column and release back into the water
column as dissolved Mn. Measured Mn distributions in the vicinity of the
southern Juan de Fuca Ridge and estimated values of process rate constants
are used to limit the range of possible model outcomes. The results present
a picture of water column distributions and fluxes of dissolved, fine particulate,
and large- particle associated Mn in a plume advecting off axis. The model
and best available parameter values suggest that more than 80% of the hydrothermal
Mn is deposited within several hundred kilometers of the ridge crest, though
dissolved Mn concentrations beyond that distance exceed background levels
by many times. The residence time of hydrothermal Mn in the water column
is of the order of several years. An off-axis component of advection of
the order of 0.1-0.3 cm/s is needed to make similar the model and measured
distributions of Mn depositing in the sediments.
|