A chemical model of the buoyant and neutrally buoyant plume above the TAG vent field, 26 degrees N, Mid-Atlantic Ridge

Journal Article · Thu Jul 01 00:00:00 EDT 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90285-5· OSTI ID:6248594

Rudnicki, M D; Elderfield, H ^[1]

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1. Cambridge Univ. (United Kingdom)

The kinetics of iron particle formation in the neutrally buoyant plume above the TAG vent field have been calculated from submersible-collected CTD data within the initial 150 m of plume rise. Results show that particles form by a two-stage process: about half the iron in the high temperature vent fluid is removed as sulfides within a few seconds of venting, and the remainder is removed by Fe[sup 2+] oxidation. The pseudo-first-order rate constant for the second process has been calculated (k[sub 1] = 0.329 min[sup [minus]1], similar to literature values for seawater) and gives a half-life time for Fe[sup 2+] in solution of 2.1 minutes. The kinetics of iron particle formation have been used in a conceptual model of the chemistry of the TAG plume. The average dilution at which iron oxyhydroxide particles form, [bar E][sub Fe], is [approximately]570 from which element/Fe ratios of particles at the top of the buoyant plume have been predicted. Oxyanion/Fe ratios can be chiefly accounted for by coprecipitation for Cr (71%), V (67%), As (45%), and P (42%) but Mo (0.1%) and U (0.02%) show anomalously low coprecipitation. Th/Fe and REE/Fe ratios are greater than can be accounted for by coprecipitation, demonstrating that scavenging occurs in the buoyant plume for these elements. A scavenging model has been fitted to trace metal data previously reported for neutrally buoyant hydrothermal plume particulate samples collected above the TAG vent field. Quantitative removal of vent fluid derived REE, with the possible exception of Eu, during buoyant plume rise means that hydrothermal activity has no direct impact on the seawater chemistry of the REE. If coprecipitation and scavenging within the TAG hydrothermal plume are typical, such processes during plume rise and dispersion play a significant role in the removal of reactive trace metals and oxyanions from seawater, at rates of the same order as those of river input to the oceans. 51 refs., 11 figs., 7 tabs.

• OSTI ID: 6248594
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 57:13; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
RARE EARTHS
MASS BALANCE
SCAVENGING
SEAWATER
CHEMICAL COMPOSITION
ARSENIC
CHROMIUM
COBALT
COPPER
COPRECIPITATION
ENVIRONMENTAL TRANSPORT
HYDROTHERMAL ALTERATION
IRON
LEAD
MATHEMATICAL MODELS
MOLYBDENUM
PHOSPHORUS
PLUMES
THORIUM
THORIUM 228
THORIUM 230
THORIUM 234
TIN
URANIUM
VANADIUM
ZINC
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ACTINIDES
ALPHA DECAY RADIOISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DAYS LIVING RADIOISOTOPES
ELEMENTS
EVEN-EVEN NUCLEI
HEAVY ION DECAY RADIOISOTOPES
HEAVY NUCLEI
HYDROGEN COMPOUNDS
INTERNAL CONVERSION RADIOISOTOPES
ISOTOPES
MASS TRANSFER
METALS
NEON 24 DECAY RADIOISOTOPES
NONMETALS
NUCLEI
OXYGEN COMPOUNDS
PRECIPITATION
RADIOISOTOPES
SEMIMETALS
SEPARATION PROCESSES
SPONTANEOUS FISSION RADIOISOTOPES
THORIUM ISOTOPES
TRANSITION ELEMENTS
WATER
YEARS LIVING RADIOISOTOPES
540320* - Environment
Aquatic- Chemicals Monitoring & Transport- (1990-)