The Composition of Phosphatized Bones in Recent Sediments

Mineral and chemical compositions of bone phosphate were studied in two samples from the outer Namibian shelf sediments composed of fish skull fragments and whale ribbon. Fossilization of bones is accompanied by the accumulation of lithogenic components, iron, sulfur, rare earth and other trace elements (Ni, Cu, Co, Cd, Mo, La, Ce, Th, U, and others), whereas the organic and mineral carbon content decreases. The evolution of bone phosphate during fossilization consists in transition from primary hydroxylapatite to a gel-type material, which subsequently becomes globular and crystallizes as fluorcarbonate-apatite crystallites. Additionally, some authigenic minerals, including both relatively widespread minerals (pyrite, uraninite, and coffinite) and rare minerals (graphite and calcium and germanium oxides) are formed in the bones. A considerable proportion of uranium in bones consists of uranium minerals, which also contain rare earth elements.