The geochemical balance of the rare earth elements and neodymium isotopes in the oceans

Journal Article · Sat May 01 04:00:00 EDT 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90087-D· OSTI ID:6290069

Bertram, C J; Elderfield, H ^[1]

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1. Univ. of Cambridge (United Kingdom)

Profiles of REE concentrations and neodymium isotope measurements in the western Indian Ocean are consistent with published data from the other major oceans. REE concentrations show a strong hydrographic control. The influence of intermediate water masses is particularly significant. Surface water concentrations vary with salinity. Particulate REEs are less than 5% of dissolved concentration, except for Ce, where up to [approximately]20% of total REEs are present as >0.4 [mu]m particles. In contrast to dissolved profiles, concentration profiles of particulate REEs, including Ce, all increase with depth. REE concentrations correlate with silica over all but the deepest waters, although, in detail, correlations are complex. The neodymium isotopic composition of Indian Ocean seawater (avg. [epsilon][sub Nd(0)] = [minus]8.3) is intermediate between that for the Atlantic and Pacific oceans. Comparison of REE data from the major oceans shows that the HREEs behave more like Si than do the LREEs. Sm/Nd ratios are near-constant for all oceans, whereas Er/Nd ratios vary between the Atlantic, Indian, and Pacific oceans. The fractionation of the REEs in surface seawaters can be explained by fractionation factors relative to silica from [approximately]0.12 for La to 0.05 for Er. Use of a seven-box model shows that the interoceanic variations in neodymium isotopic compositions and Nd concentrations cannot be reconciled unless particle-water exchange is invoked. The degree of exchange required is consistent with particle residence times of [approximately]1--10 yr. 54 refs., 18 figs., 4 tabs.

• OSTI ID: 6290069
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 57:9; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540320* -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
ALPHA DECAY RADIOISOTOPES
ATLANTIC OCEAN
CERIUM
CHALCOGENIDES
CHEMISTRY
CONCENTRATION RATIO
DYSPROSIUM
ELEMENTS
ERBIUM
EUROPIUM
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GADOLINIUM
GEOCHEMISTRY
INDIAN OCEAN
INTERMEDIATE MASS NUCLEI
ISOTOPE RATIO
ISOTOPES
LANTHANUM
LUTETIUM
METALS
NEODYMIUM 143
NEODYMIUM 144
NEODYMIUM 148
NEODYMIUM ISOTOPES
NUCLEI
OXIDES
OXYGEN COMPOUNDS
PACIFIC OCEAN
PARTICLES
RADIOISOTOPES
RARE EARTH NUCLEI
RARE EARTHS
SAMARIUM
SEAS
SILICON COMPOUNDS
SILICON OXIDES
STABLE ISOTOPES
SURFACE WATERS
YEARS LIVING RADIOISOTOPES
YTTERBIUM