SYNTHESIS OF PT- AND PD-SULPHIDES IN LOW TEMPERATURE (85°C) SOLUTIONS BUFFERED BY CLAY MINERALS AND GRAPHITE: PRELIMINARY RESULTS

Abstract

Some recent investigations of black shales reveal platinum-group element (PGE) concentrations in the ppm range. The low temperature nature of these mineralized sediments and their composition stimulated this first attempt to synthesize Pt- and Pd-phases in solutions at temperatures below 100°C under reducing conditions with H2S flow through the solution. Experiments under controlled Eh-pH with montmorillonite presaturated in Pd and Pt in different chloride solutions resulted in the formation of Pt- and Pd-sulphides. PtS- and PdS-stability fields are very close to each other in Eh-pH values (∼400mV, 9). These data are in good agreement with those determined for some base metal sulphides synthesized at similar temperature by other researchers. The results may support the role of clay minerals as possible concentrators for PGE in the sedimentary environment.