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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.

model images, click for large size

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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Related Papers:

Lavelle, J.W. (1993): A model for estuarine sedimentation involving marine snow. In Nearshore and Estuarine Cohesive Sediment Transport A.J. Mehta (ed.), Coastal and Estuarine Study Series, American Geophysical Union, Washington, D.C., 148-166.

Cudaback, C.N., A.J. Paulson, and J.W. Lavelle (1991): A modeling study of the vertical distribution and transport of manganese in Puget Sound. NOAA Technical Memorandum ERL PMEL-93 (PB92-128644), 21 pp..

Lavelle, J.W., C.N. Cudaback, A.J. Paulson, and J.W. Murray (1991): A rate for the scavenging of fine particles by macroaggregates in a deep estuary. Journal of Geophysical Research, 96(C1), 783-790.

Feely, R.A., M. Lewison, G.J. Massoth, G. Robert-Baldo, J.W. Lavelle, R.H. Byrne, K.L. Von Damm, and H.C. Curl, Jr. (1987): Composition and dissolution of black smoker particulates from active vents on the Juan de Fuca Ridge. Journal of Geophysical Research, 92(B11), 11,347-11,363.
  Modeling focuses: Chronic focused-source | Event Plumes | Axial Valley transport | Ridge Flow | Geochemical Transport | Hydrographic-Tracer Relationships