Rare earth elements in old biogenic apatites

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

DOI:https://doi.org/10.1016/0016-7037(93)90413-Q· OSTI ID:6185100

Grandjean-Lecuyer, P; Albarede, F ^[1]; Feist, R ^[2]

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1. Centre de Recherches Petrologiques et Geochimiques, Vandoeuvre-les-Nancy (France)
2. Universite de Montpellier 2 (France)

The REE distributions in individual Upper Devonian conodonts have been measured by ion probe. The patterns of all analyzed conodonts are enriched in middle REE (Eu-Gd) and have a weak or no Ce anomaly. Concentrations and La/Yb or La/Sm ratios vary very little within or among individuals from the same zone, which suggests that uptake or labile REE from sediments was essentially quantitative. Therefore, the REE signature of the primary carriers, probably organic and oxyhydroxides particulates from marine suspensions, was efficiently transferred to biogenic apatites and survived late diagenetic processes. REE patterns of conodonts do not resemble those of present-day seawater and post-Cretaceous biogenic phosphates, which are typically depleted in Nd and Sm with a negative Ce anomaly. Since REE distributions in the modern water column mimic those of nutrients, the authors assume that, in pre-Cretaceous seawater, they were not controlled by surface biological activity. They assume instead that REE in pre-Cretaceous seawater can be explained by mechanisms of desorption-adsorption on particle surfaces. Progressive extraction of LREE from river water by oxyhydroxides leads to precipitates enriched in middle REE. A simple quantitative model was calculated in order to illustrate the proposed mechanism. 43 refs., 5 figs., 1 tab.

• OSTI ID: 6185100
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 57:11; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CRETACEOUS PERIOD
COMPARATIVE EVALUATIONS
DEVONIAN PERIOD
FOSSILS
QUANTITATIVE CHEMICAL ANALYSIS
RARE EARTHS
CONCENTRATION RATIO
BIOLOGICAL PATHWAYS
ENVIRONMENTAL TRANSPORT
RIVERS
SEAS
CHEMICAL ANALYSIS
ELEMENTS
EVALUATION
GEOLOGIC AGES
MASS TRANSFER
MESOZOIC ERA
METALS
PALEOZOIC ERA
STREAMS
SURFACE WATERS
540320* - Environment
Aquatic- Chemicals Monitoring & Transport- (1990-)