The rhenium content was determined in 12 samples of oceanic phosphorites using kinetic and ICP-MS techniques, the latter of which appeared to be more correct. The rhenium content in the phosphorites from the ocea bottom ranges from 3 to 50 ppb, whereas the in the phosphorites from Christmas and Nauru islands is 1.3 and less than 1 ppb, respectively, corresponding to the average rhenium conent in sedimentary rocks (about 1 ppb). Rhenium does not show any relationship with phosphorus, aluminosilicates, or iron and manganese oxyhydroxides, but a correlation trend with organic carbon and total sulfur (partially bound in pyrite) is revealed. Enclosing reduced biogenic sediments enriched in hydrogenetic rhenium serve as a primary rhenium source for the phosphorites. The rhenium concentration in phosphorites possibly depends on the duration of their being in a reduced environment and on the conditions of their subsequent exposure at the ocean bottom.
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