Phase Analysis of Pt, Pd and Au in Black Rock-type Platinum Group Element Minerals by ICP-MS

Black rock as an important carrier of platinum group elements was discovered in recent years. Due to the multiple origins and complex mineralization, the distribution and occurrence of platinum group elements in black rock are not clear, which is also the major reason why the analytical results of platinum group elements are unstable. According to the mineral properties and composition of black rock, the occurrences of Pt, Pd and Au in black rock could be divided into exchangeable phase, organic binding phase, sulfide bounding phase, and residue phase. The adsorption of Pt, Pd and Au from the organic carbon in black rocks was inhibited by adding potassium thiocyanate and sodium cyanide as desorbents. The distribution of Pt, Pd and Au in each phase was identified by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The results show that: (1) The ratios of the total extraction of each phase to the total amount of the element are 94.4%-101.0% for Pt, 95.8%-101.0% for Pd, and 96.7%-102.0% for Au, indicating good accuracy and reproducibility. (2) The enrichment of Pt, Pd and Au in black rock minerals not only shows the chalcophile affinity, but also shows obvious correlation with the geological conditions and geological setting of organic carbon formation. The results provide important information for studying the geochemical environment and the metallogenic regularity of the platinum group elements in black rocks.