(Table 2) Chemical composition and sulfur and iron speciations in phosphorites and host sediments from the Namibian-, Peru- and Chile shelves and from the Sea of Japan

Sulfur speciation was studied by chemical methods in recent, Pliocene-Pleistocene and Miocene phosphorites from the inner and outer Namibian shef, Late Quaternary phosphorites from the Peru-Chile shelf and Miocene phosphorites from some underwater highs of the Sea of Japan. Following concentrations (%) were measured: 0.25-1.147% of sulfate sulfur (S SO4), 0.012-1.473% pyritic sulfur (S pyr), 0.005-0.141% of organic sulfur (TOS), and <0.0001-0.04% of elemental sulfur (S°). Generally sulfate sulfur was predominant, but in some samples pyritic sufur was more abundant. (S SO4/S pyr) ratio varied from 0.36 to 18 in shelf phosphorites and increased to 37-52 in phosphorites from the Sea of Japan. The most part of sulfate sulfur seemed to be incorporated in apatite mineral of phosphorites. Samples enriched in organic matter were enriched in pyritic sulfur as well, but without direct correlation between them. Similar relation was found between organic matter and organic sulfur. Relative amount of non-pyritic Fe(II) in phosphorites from reducing environment was found to decrease with time along with their lithification owing to continuation of pyritization.