Sur l'origine des phosphates de l'atoll corallien de Nauru

Autre(s) titre(s) On the origin of phosphates from the nauru atoll
Type Article
Date 1991
Langue(s) Français
Auteur(s) Bernat M, Loubet M, Baumer A
Source Oceanologica Acta (0399-1784) (Gauthier-Villars), 1991 , Vol. 14 , N. 4 , P. 325-331
WOS© Times Cited 4
Keyword(s) PHOSPHATES, ATOLLS, ISOTOPES, U, TH, SR
Résumé en anglais Phosphates from the Nauru atoll lie on a karstic structure developed at the expenses of a coral reef. These formations are fluorapatites low in carbonate, with less fluorine than common marine carbonate-fluorapatites (CFA). At least one of the deposits is from the last interglacial era (Th-230-U-234 dating). Rare Earth spectra seems to be affected by the dissolution-precipitation reactions leading to the formation of the carbonate-fluorapatite. But U and Sr isotopic ratios support the marine origin of most of these formations, except for one result, which give a Nd-143/Nd-144 ratio indicating a slight volcanic influence. Our results and the literature reports favorise the hypothesis that these phosphates originate from the endo-upwelling of phosphorus rich deep seawater through the fracturated and porous mass of the carbonated reef.
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