Preprints
Filtering by Subject: Geochemistry
The magnitude of equilibrium isotope fractionation of Mg between forsterite, diopside and melt at liquidus temperatures
Published: 2026-01-12
Subjects: Earth Sciences, Geochemistry, Mineral Physics
We examine the equilibrium fractionation of Mg isotopes between forsterite, diopside, and a coexisting melt at liquidus temperatures using a combination of analyses of petrological-experiment products and atomic-scale simulations. Our experiment yields ∆²⁶Mgol/melt = -0.058 ± 0.032 ‰ (2s.e.) and ∆²⁶Mgcpx/melt = 0.060 ± 0.034 ‰ (2s.e.) for crystals grown from a near-cotectic basaltic melt in the [...]
Reviewing chronostratigraphic uncertainty of the Ediacaran-Cambrian transition
Published: 2026-01-02
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Geology, Stratigraphy
The Ediacaran-Cambrian transition archives the widespread disappearance of ‘Ediacaran-type’ soft-bodied biota and the appearance of most modern animal body plans, including a major diversification of skeletal animals and styles of animal-substrate interaction. Despite over a century of study, our ability to confidently reconstruct the series of macroevolutionary events that inform origination and [...]
Solubility and speciation of sulfur in silicate melts under crustal conditions
Published: 2025-12-13
Subjects: Earth Sciences, Geochemistry, Geology, Volcanology
We have determined the solubility of sulfur as either sulfide (S2-) or sulfate (S6+) in a wide range of silicate melts at 1 atm pressure and temperatures of 1050° to 1250°C. The method involved suspension of the melt in either a mixture of CO2-CO-SO2 (sulfide solubility) or SO2 and air (sulfate solubility) for periods of up to 120 hours. Sulfur concentrations, measured by electron microprobe were [...]
Recurrent evacuation of mantle mush by mafic recharge in ocean island basalts, recorded by La Palma clinopyroxene
Published: 2025-12-04
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics, Volcanology
Temporal variations in magma plumbing architecture and magmatic processes influence eruption priming and the interpretation of pre- and syn-eruptive signals. Yet, how these processes operate in low-flux volcanoes remains poorly constrained, leaving a key gap in understanding eruption precursors. Here we examine the temporal evolution of magmatic processes at La Palma, Canary Islands, a low-flux [...]
Oxidation state of Mayotte magmatic series: insights from Fe and S K-edge XANES spectroscopy
Published: 2025-11-28
Subjects: Earth Sciences, Geochemistry, Volcanology
Following the 2018-2020 Fani Maoré submarine eruption near Mayotte Island, Indian Ocean, multiple oceanographic expeditions provide unprecedented access to fresh alkaline volcanic glasses spanning basanite to phonolite compositions from the East-Mayotte Volcanic Chain (EMVC). We applied Fe and S K-edge X-ray Absorption Near-Edge Spectroscopy (XANES) to determine iron and sulfur oxidation states [...]
Crystalline silica content of natural, engineered, and synthetic stone products and their relation to silicosis policy development
Published: 2025-11-13
Subjects: Earth Sciences, Geochemistry, Geology, Materials Science and Engineering, Public Health
Crystalline silica minerals – quartz, cristobalite, and tridymite – are hazardous when inhaled. They are at least an order of magnitude more toxic than crystalline silica-free inert mineral dusts. Workplace exposure to hazardous levels of crystalline silica is entirely preventable, yet accelerated silicosis is emerging in developed countries, from the fabrication of crystalline silica-rich [...]
Effect of chemical disequilibrium during metal-silicate partitioning on the thermal state of the early core
Published: 2025-11-06
Subjects: Earth Sciences, Geochemistry, Geophysics and Seismology, Planetary Geology, Planetary Geophysics and Seismology
In this study, we improved a previously published numerical model linking the core composition to the core temperature during accretion by introducing the possibility of chemical disequilibrium during the segregation of the core in the magma ocean phase. Our study shows that at least 60% of the accreting metal needs to be equilibrated in order to obtain a chemically coherent Earth, thus favoring [...]
Radiogenic Sr-Nd-Pb isotope behavior in different grain-sized fine lithic materials during basalt weathering
Published: 2025-10-16
Subjects: Atmospheric Sciences, Climate, Earth Sciences, Geochemistry, Geology, Geomorphology, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Sedimentology, Stratigraphy
Radiogenic isotopes are widely used as sediment provenance tracers; however, their weathering response has not been fully established. This study investigates the weathering sensitivity of Sr-Nd-Pb isotopes in fine lithic fractions (FLF; grain size <2 μm, <5 μm, and <20 μm) capable of long-range transport. Geochemical and isotope compositions have been measured in the physicochemically [...]
Formation and fluxes of natural hydrogen in the crust and upper mantle
Published: 2025-10-10
Subjects: Biogeochemistry, Earth Sciences, Geochemistry
Molecular hydrogen (H2) is a fundamental component of planetary evolution and an important energy source for microbial life. It is now understood that natural mechanisms, spanning geological and biological processes, can produce high concentrations of hydrogen in natural fluids. Quantifying the processes that modulate natural hydrogen concentrations is necessary not only for conceptualising the [...]
Evidence for seawater Mg/Ca and dietary control on Mg incorporation in oyster shells
Published: 2025-09-18
Subjects: Geochemistry
The Mg/Ca ratio in bivalve shells has been investigated as a promising proxy for temperature reconstruction of the seawater. However, important discrepancies exist among the Mg/Ca-temperature calibrations reported for bivalves in the literature. These discrepancies currently limit the use of Mg/Ca for paleoclimate reconstructions based on bivalves and suggest that factors beyond temperature [...]
A Hybrid Iron/Green-Rust-Urea Model for Prebiotic Chemistry: A Synthesis of Testable Pathways for Planetary Astrobiology
Published: 2025-09-17
Subjects: Earth Sciences, Geochemistry, Planetary Geochemistry, Planetary Geology, Planetary Hydrology, Planetary Sciences
We propose a quantitative, testable framework for abiogenesis that links submarine alkaline vents, which supply H₂, ΔpH, and Fe/Fe–S catalysis, to subaerial hot-spring fields that provide wet–dry concentration and UV-driven photoredox chemistry. To bridge dilution between environments, we specify mobile “holding pens” (green-rust/iron flocs, silica mats, pumice rafts, and sea-surface [...]
Using X-ray Fluorescence to Detect Automobile Heavy Metal Pollution in Los Angeles Soils with Copper and Palladium as Indicators
Published: 2025-08-29
Subjects: Earth Sciences, Environmental Health and Protection, Environmental Indicators and Impact Assessment, Environmental Monitoring, Environmental Sciences, Geochemistry, Physical Sciences and Mathematics
This project evaluates the effectiveness of using portable X-ray Fluorescence (XRF) to detect soil composition matrices that show patterns of anthropogenic influence. We explore 26 areas within Los Angeles County, California, that have various amounts of traffic; classifying each locale as Urban or Recreational. The main elements of interest are copper and palladium. These indicators are largely [...]
An Ice Core Snapshot of Past Atmospheric Chemistry in Mt. Everest’s 'Death Zone'
Published: 2025-08-21
Subjects: Earth Sciences, Environmental Sciences, Geochemistry, Glaciology, Other Environmental Sciences, Physical Sciences and Mathematics
We present a unique atmospheric chemistry record from the highest ice core ever recovered (8020 m, South Col Glacier (SCG), Mt. Everest), that captures ~400 years of deposition during the latter half of the first millennium BCE. Due to recent glacier thinning, the upper ~2000 years of accumulation have been lost, however, this is the only ice core record ever recovered from the “Death Zone [...]
Controls on Mg isotopic fractionation between deep mantle phases and relict signatures of a terrestrial magma ocean
Published: 2025-08-08
Subjects: Geochemistry, Mineral Physics
We use density functional theory to investigate the fractionation of Mg isotopes between phases in the lower mantle. Our results support previous work and show that coordination number plays an important role in controlling isotopic fractionation, with bridgmanite (perovskite-structured MgSiO3) preferentially incorporating lighter Mg isotopes into its highly coordinated site compared to periclase [...]
A novel experimental V-Sc olivine-melt oxybarometer for arc magmas
Published: 2025-07-30
Subjects: Earth Sciences, Geochemistry
This manuscript is a preprint. A substantially revised and peer-reviewed version has been published in Geochimica et Cosmochimica Acta (DOI: https://doi.org/10.1016/j.gca.2025.12.025), which should be cited instead. Redox conditions significantly affect phase equilibria, the availability and mobility of heterovalent elements, including volatiles (i.e., S) and metals (e.g., Fe, Cu) in silicate [...]