Mobility of dissolved palladium and platinum species under water-rock interaction in chloride media: modeling of PGE behavior under interaction of oceanic serpentinites with sea water derivates

To elucidate the possibility of PGE transfer by highly-salt chloride solutions, the palladium and platinum behavior was simulated in the conditions of low-temperature hydrothermal transformation of serpentinites of the oceanic crust. In dynamic water-rock experiments using columns lled with crushed ultrabasic rocks of the ocean oor (harzburgite serpentinites of mid-oceanic ridges with dierent degrees of carbonatization), it is established that the eciency of palladium transfer depends on the alteration (carbonatization) degree of peridotites and under the experimental conditions is 80–100%. It is assumed that the transport of palladium occurs as a result of the formation of a strong complex compound with thiosulfate ion, which is an intermediate oxidation product in the “sulphide-sulfate” system. Platinum, hydrolyzed at approximately neutral pH and not forming compounds with thiosulfate ion, is completely retained by serpentinites, possibly due to sorption interactions with silicates. Thus, the higher mobility of palladium during the low- temperature transformation of abyssal peridotites and the dependence of the character of its distribution in the studied rocks on the processes of serpentinization and carbonatization have been conrmed.