Some observations on the determination of platinum group elements and gold in black shales

The concentration levels and distribution features of the platinum group elements (PGE) in black shales with high carbon content from the Bureya Massif, Far East Russia are discussed. This study compares PGE and gold (Au) values in black shale ores from the eastern Bureya Massif. Mineralogical studies using SEM-EDS on PGE-bearing inclusions in black shales reveal that they always contain O and C along with Pt, Pd, Ir and Os. It is believed that PGE are present in the form of organometallic compounds which are extremely resistant to any exposure, including acid dissolution and fire assay procedures. There is a lot of variation in the concentration values obtained using different analytical methods. Observations, problems and possible causes for the erratic and low recoveries of Au and PGE in the highly carbonaceous black shales are discussed.