FORMS OF GOLD AND PLATINUM IN PHOSPHORITES ON THE NAMIBIAN SHELF

Abstract

Overview of works devoted to geochemistry of rare and trace elements in phosphorites has revealed that they cannot concentrate noble metals (Au, Pt, and PGM). This statement is also valid for phosphorites on the ocean floor. However, the presence of Au has been reported in. For example, the content of native gold in the heavy fraction of phosphate sand from the Ukolov deposit (lower Santonian sediments, Kursk district) is as much as 36.4 mg/m3. The Au content based on phosphate nodule mass is three times higher (0.01–0.03 g/t). Gold occurs as nonrounded particles (up to 0.3 × 0.2 mm across) and coatings, suggesting the absorptional mechanism of their accumulation.