Chemical composition in phosphate materials from the ocean floor

Total Cl content varies from 0.05 to 4.25% in phosphorites and from 2.48 to 2.75% in recent phosphate-bearing sediments. Recent phosphorites are enriched in Cl relative to ancient ones.

Bound Cl content (not extractable by washing), which increases with lithification, varies from 0.17 to 0.60% in ocean and land phosphorites and from 0.02% to 1.30% in bone phosphate. Na content in most samples is higher relative to Na of NaCl due to its incorporation into the crystal lattice of apatite. However, the opposite relationship is observed in some samples indicating partial Cl incorporation into the anion complex of phosphate.