Rare-Earth distributions in the marine environment

Abstract

Analyses for the rare‐earth elements in sea water, in a phosphorite, and in a manganese nodule were made by neutron activation and X‐ray fluorescence techniques. These marine samples showed a depletion, in the heavier rare‐earth elements, relative to chondritic meteorites, beginning with samarium. Cerium was enriched in the manganese nodule, probably as a result of its oxidation to the 4+ valence state. The ratios of the rare‐earth abundances in the two minerals to those of sea water go through a maximum in the vicinity of samarium. The europium concentration, often anomalous in terrestrial minerals, was normal relative to the other rare earths in all of the samples. The sea water showed four times the concentration of rare earths at a depth of 4000 meters as compared with surface values.

Lanthanide tetrad effect observed in marine environment.

“…Effectively close relationship between phos phorite (GOLDBERG et al, 1963) and our sea water is shown in Fig. 5.…”

“…4. Like sea water analyzed by GOLDBERG et al (1963), our sample shows large negative Cc anomaly. Compared with the value Cc* estimated to fall on the La-Nd join, the depletion factor for the observed Cc value is 3.34(=Ce*/Ce).…”

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We have found that lanthanide tetrad effect (PEPPARD et al, 1969) is operative for heavy rare-earth elements (REE) in a phosphorite sample (GOLDBERG et al, 1963). Also it has been evinced that the similar effect is observed for REE in sea waters.

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“…Variation of log K with atomic number Z where K is the equilibrium distribution constant between an aqueous solution of 1.1 F LiBr + 0. SF HBr and the solution of 0.6F di(2-ethylhexyl) chloromethyl phos phonate in benzene, at 22° ± 2°C EXAMINATION OF DATA BY GOLDBERG et al GOLDBERG et al (1963) analyzed a surface sea water, a phosphorite and a manganese nodule for rare-earth elements, REE, i.e., lan thanides, employing the technique of neutron activation analysis.…”

“…It is understood (GOLDBERG et al, 1963) that the REE found in the oceanic phosphorite are very probably precipitated directly from sea water. It grasps and retains our attention that, as seen in Fig.…”