Analytical Methods for the Highly Siderophile Elements

The highly siderophile elements (HSE) include the fifth-period transition metals ruthenium (Ru), rhodium (Rh), palladium (Pd), and the sixth-period transition metals rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt) and gold (Au). In addition to being iron-loving, these elements are also resistant to oxidation, have high melting temperatures and are important as industrial catalysts. HSE abundances in geologic materials vary significantly, ranging from ~1 mg/g in ore materials down to a few pg/g in basalts (Table 1). These elements comprise two long-lived radiometric decay schemes: 187Re decays to 187Os, and 190Pt decays to 186Os. View this table: Table 1 Range of HSE abundances, in ng/g, in selected rock types and in model upper mantle. The HSE have been targeted to address a wide variety of geochemical and cosmochemical questions. Early work suggested HSE concentrations can constrain Hadean mantle evolution (Chou 1978) and showed the geochronologic potential of the Re/Os isotope system (Herr and Merz 1955; Herr et al. 1961; Markey et al. 1998). More recent applications combine the Re–Os decay system with abundance data for the HSE to investigate the evolution of the planets and the moon (Day et al. 2010, 2016, this volume), the terrestrial mantle (Rehkamper et al. 1997; Aulbach et al. 2016, this volume; Harvey et al. 2016, this volume; Luguet and Reisberg 2016, this volume), impact craters (Koeberl and Shirey 1993), geochemistry and geochronology of ore formation (Markey et al. 1998; Barnes and Ripley 2016, this volume), tektites (Koeberl and Shirey 1993), as well as the formation and evolution of the continental curst (e.g., Peucker-Ehrenbrink and Jahn 2001). Non-mass dependent isotope variations in Re, Os, Ru, Pt and Pd are also present in some meteorites and lunar samples and arise from nucleosynthesis and cosmogenic radiation (Yokoyama and …