ORIGIN OF RARE-EARTH ELEMENTS IN CYANOBAC TERIAL MATS (KOPARA) FROM TIKEHAU ATOLL (TUAMOTU, FRENCH-POLYNESIA)

Concentration patterns of rare earth elements have been determined in a core sampled in a cyanobacterial mat (kopara) from Tikehau atoll (Tu amotu). These patterns show the marine origin of the analyzed elements . Enrichments in the kopara have been calculated with regard to concen trations of rare earth elements in two water columns from the Pacific Ocean. They would indicate, with the cerium anomaly, that the marine w ater which fed the kopara originated from Antarctic Intermediate Water . These results support the implication of endo-upwelling as the mecha nism of supplying REE and nutrients to the kopara and the filiation ko para-insular phosphorites.