Trisulfur radical anion S3•--A major carrier for platinum in hydrothermal fluids.

Platinum (Pt) and other platinum group elements (PGE), including palladium (Pd), iridium (Ir), rhodium (Rh), ruthenium (Ru), and osmium (Os), have many advantageous characteristics, including catalytic properties, corrosion resistance, and high melting points (Table 1), which lend themselves to various applications ranging from automotive catalysts to pharmaceutics to use in jewelry (1). In particular, the chemical behavior of PGE is quite unique: On the one hand, they are inert and highly resistant to corrosion by most chemicals; on the other hand, they can serve as catalysts, accelerating the rates of many petrochemical reactions. However, PGE have very low elemental abundances in Earth's crust, all at part per billion (ppb) levels (Table 1) (2, 3). Hence, PGE-bearing ore deposits are a critical resource, and their extracted PGE metals are highly sought after by modern industries. To effectively utilize sparse PGE resources, it is essential to understand the formation of PGE ore deposits for their targeted exploration and to develop efficient chemical approaches for PGE extraction and separation. View this table: Table 1. Some characteristics of PGE and associated Au Although the natural abundances of PGE are low, fortunately, they are not evenly distributed within Earth and other planets. Because of their aversion to bonding with oxygen and their high affinity for reduced sulfur, PGE tend to either occur in the metallic state (siderophile, metal loving) or bond with sulfur or other group VA and VIA ligands (chalcophile, sulfur loving) to form mineral components (4). Consequently, PGE are concentrated in core-forming Fe-Ni alloys and in sulfide phases of PGE-bearing ore deposits (5). This distinct behavior of PGE, as well as their radioisotope systematics, can serve as indicators of many geological processes such as early solar system evolution, and planetary differentiation and formation (6). Of critical importance to PGE-bearing ore deposits is the enrichment of PGE … [↵][1]1Email: hxu{at}lanl.gov. [1]: #xref-corresp-1-1