HYDROTHERMAL PLATINUM-GROUP MINERAL OCCURRENCES IN WESTERN NORTH AMERICA: REVIEW AND META-ANALYSIS OF EXISTING GEOCHEMICAL DATA WITH IMPLICATIONS FOR MINERAL EXPLORATION

Dozens of instances of platinum-group element (PGE) mineralization have been documented in western North America. Apart from the Stillwater Complex and Alaskan-Ural type intrusions, these occurrences are not directly associated with the geologic settings traditionally expected to host large PGE ore deposits, such as volumetrically extensive layered mafic intrusions or ultramafic cumulate reefs. Instead, the occurrences assessed here are described from (1) Cu-Au porphyry deposits; (2) structurally controlled hydrothermal systems potentially distally related to mafic-to-ultramafic (meta)plutonic rocks; and (3) metalliferous carbonates/skarns. Despite the generally subeconomic status of these occurrences, they can exhibit localized high-grade (>1.5 g/ton total PGE) mineralization and as such offer unique insight into PGE behavior, especially in non- mafic-ultramafic magmatic systems where the mechanisms of PGE concentration remain unresolved. Here, a compilation and meta-analysis of available whole rock geochemical data from western North American PGE occurrences, including the Stillwater Complex, has been employed to identify significant geochemical trends, relationships, and correlations between precious metals (PGEs + Au), base and transition metals (Ni, Cu, Zn, Pb, Cr), and sulfur. Preliminary statistics and correlogram analyses indicate Ni to be highly correlated with PGEs across deposit types, thereby making it the most effective exploration vector for PGE mineralization. Copper, which is commonly associated with PGE ores, strongly correlates with PGEs in magmatic and hydrothermal settings, . Overlapping multi-element profiles across deposit-types further suggests that PGEs can be mobilized and concentrated in a wide variety of geologic conditions and environments ranging from shear zones to carbonate shelves, and that simple geochemical and statistical analyses can be powerful for their identification and interpretation. Lastly, this study highlights the collective promise of western North America with regards to the discovery of unconventional PGE resources.