Rare earth elements in ferromanganese nodules of the Chukchi Sea

Data on the morphology, microstructure, and chemical and mineral compositions of ferromanganese nodules (FMN) in the Chukchi Sea are presented. Specific features of the distribution and mineral modes of rare earth elements (REE) and yttrium are examined. The studied nodules are characterized by low contents of total REE along with negative Ce and weak positive (virtually neutral) Eu anomalies: Σ(REE) 185.26–299.10 ppm, Ce an 0.73–0.96, and Eu an 1.01–1.13. The Y/Ho ratio varies from 23.19 to 29.88; the ratio of light and heavy REEs (LREE/HREE) NASC , from 0.74 to 1.50. The presence of La-Ce-Pr-Nd-O and La-Ce-Pr-Nd-Al-O micrograins along with monazite, xenotime, and some other more exotic compounds has been established. The majority of geochemical indicators testify to the diagenetic origin of FMN. The most characteristic property of the studied nodules is high (Fe + Mn)/Ti module (up to 295.05).