Marc-Alban Millet

Whether Archean arc-like volcanism reflects subduction remains debated. We present high-resolution geochemical data from a well-preserved 3.13-3.10 Ga arc-like volcanic succession in Australia’s Pilbara Craton, a rare Archean analog of modern arc volcanism retaining fluid-mobile element concentrations consistent with primary magmatic values. The sequence records three primitive lava series typical of modern arcs: tholeiitic, calc-alkaline, and the oldest stratigraphically extensive genuine boninites. Geochemical modelling shows this melt diversity requires at least two mantle sources with distinct depletion histories. The mantle H ₂ O required for fluid-assisted melting to produce these lavas substantially exceeds primitive mantle, approaching the H ₂ O-saturated solidus of modern mantle wedges. We infer hydrous melting was triggered by dripduction, the short-lived inclined foundering of hydrated lithosphere without laterally continuous plate boundaries, in an off-plateau setting. Dripduction locally recycled surface water and generated arc-like magmas without self-sustained plate tectonics, possibly promoting mantle-ocean-atmosphere volatile exchange during the Archean.

The Archean to Paleoproterozoic Earth underwent significant changes in surface, crust and mantle systems, yet interactions between these reservoirs remain poorly constrained. Sanukitoids are generated by mantle–crust interaction, and thus provide a record of early Earth recycling processes. Here we combine Barium (Ba) and Magnesium (Mg) stable isotopes with radiogenic isotopes and elemental data from 3.4-2.1 Ga sanukitoids to trace crust-mantle interaction across this critical interval. Archean sanukitoids display highly variable Ba and Mg isotopic compositions, suggesting contributions from altered ocean crust, hydrothermal barite and/or sediment. In contrast, Paleoproterozoic sanukitoids show uniformly lighter isotopic signatures, closely resembling Phanerozoic arc magmas influenced by pelagic sediments. Importantly, Ba isotope fractionation before the Great Oxidation Event indicates local sulfate production and oxidized conditions in sanukitoid sources. These results reveal variable recycling of locally-oxidized ocean crust since the Paleoarchean, and confirm sanukitoids as a key archive of early Earth crust-mantle dynamics.

The landscape of academic publishing, including in geochemistry and cosmochemistry, is evolving toward greater openness and accessibility. This editorial outlines the vision for Advances in Geochemistry and Cosmochemistry, a diamond open access journal that eliminates article processing charges and prioritizes equitable access to scientific knowledge. The journal’s commitment to Open Science as well as diversity in authorship and editorial representation aims to address systemic inequities in research publishing. Drawing on the success of journals like Volcanica, we emphasize the importance of fostering inclusivity and interdisciplinary research in Earth and planetary sciences. By adopting a community-driven approach, Advances in Geochemistry and Cosmochemistry seeks to create a publishing platform that reflects the values of excellent and cutting-edge science, equity, diversity, and innovation, ensuring that knowledge is accessible to all, regardless of geographical or financial limitations.

Horse sacrifice and deposition are enigmatic features of funerary rituals identified across prehistoric Europe that persisted in the eastern Baltic. Genetic and isotopic analysis of horses in Balt cemeteries [1st to 13th centuries CE (Common Era)] dismantle prevailing narratives that locally procured stallions were exclusively selected. Strontium isotope analysis provides direct evidence for long-distance (~300 to 1500 kilometers) maritime transport of Fennoscandian horses to the eastern Baltic in the Late Viking Age (11th to 13th centuries CE). Genetic analysis proves that horses of both sexes were sacrificed with 34% identified as mares. Results transform the understanding of selection criteria, disprove sex-based selection, and elevate prestige value as a more crucial factor. These findings also provide evidence that the continued interaction between pagans and their newly Christianized neighbors sustained the performance of funerary horse sacrifice until the medieval transition. We also present a reference ⁸⁷ Sr/ ⁸⁶ Sr isoscape for the southeastern Baltic, releasing the potential of future mobility studies in the region.