THE R<scp>e</scp>-O<scp>s</scp>ISOTOPE SYSTEM IN COSMOCHEMISTRY AND HIGH-TEMPERATURE GEOCHEMISTRY

TLDR

The Re‑Os isotope system, based on the long‑lived β‑decay of 187Re to 187Os, is widely used in cosmochemistry and high‑temperature geochemistry, and its siderophilic/chalcophilic behavior distinguishes it from other long‑lived radiogenic isotope systems. Re‑Os isochrons in magmatic iron meteorites indicate core crystallization within 10–40 Myr of Solar System formation, Earth's mantle shows chondritic Re/Os evolution driven by late accretion, oceanic basalts refine mantle component interpretations, ancient subcontinental lithospheric mantle is Re‑depleted and subchondritic in 187Os/188Os, and magmatic ore deposits display initial Os isotopic variations reflecting crustal versus mantle sources.

Abstract

▪ Abstract The Re-Os isotope sytem, based on the long-lived β − transition of 187 Re to 187 Os, has matured to wide use in cosmochemistry and high-temperature geochemistry. The siderophilic/chalcophilic behavior of Re and Os is different from that of the elements that comprise most other long-lived radiogenic isotope systems. Magmatic iron meteorites (IIIAB, IIAB, IVA, and IVB) have Re-Os isochrons that indicate asteroidal core crystallization within the first 10–40 million years of Solar System evolution. Rocks from Earth's convecting mantle show generally chondritic Re/Os evolution throughout Earth history that is explained by the addition of highly siderophile elements to the mantle after core formation via late accretion. Oceanic basalts have Os-isotope systematics that improve the detailed geological interpretation of extant mantle components. Some portions of ancient subcontinental lithospheric mantle are severely depleted in Re and have correspondingly subchondritic 187 Os/ 188 Os, indicating long-term isolation from the convecting mantle during the Archean-Proterozoic. Magmatic ore deposits have differences in initial Os isotopic composition traceable to the crustal vs mantle sources of the platinum-group elements and base metals.