Preprints
Filtering by Subject: Geochemistry
A New Paradigm for High-Level Radioactive Waste Disposal: Intrinsic Radionuclide Properties and Comparative Hazard
Published: 2026-01-21
Subjects: Environmental Engineering, Environmental Sciences, Geochemistry, Geology
This paper develops a hazard- and pathway-based framework for high-level radioactive waste (HLW) disposal grounded in intrinsic radionuclide decay characteristics, geochemical behavior, and comparative hazard. We examine the physical and geochemical properties of key radionuclides and quantify lifetime cancer risk from chronic ingestion on a per-unit-mass basis using established regulatory [...]
Magmatic degassing as the primary source of salt in Archean oceans
Published: 2026-01-21
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
The salinification of Earth’s early oceans impacted both the climate and the evolution of life. However, available halogen data of Archean seawater samples are at apparent odds with a conventionally assumed mantle origin of sea salt, highlighting a critical lack of mechanistic understanding of how the Archean oceans became salty. Here, we present new triple halogen (Cl-Br-I) data from high [...]
Petrological insights into magma storage and evolution at Rabaul Caldera, Papua New Guinea
Published: 2026-01-21
Subjects: Earth Sciences, Geochemistry, Volcanology
Rabaul is a caldera volcano in Papua New Guinea. Its most recent caldera-forming eruption occurred ~1400 years ago, with numerous intra-caldera eruptions since. Erupted whole rock compositions are commonly attributed to fractional crystallisation along a single liquid line of descent, but mafic mineral clots indicate mafic recharge and magma mixing also influence whole rock compositions. [...]
The magnitude of equilibrium isotope fractionation of Mg between forsterite, diopside and melt at liquidus temperatures
Published: 2026-01-11
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: 2026-01-01
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: 2025-12-12
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: 2025-12-03
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: 2025-11-27
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: 2025-11-12
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 and implications on the dynamics of metal/silicate segregation
Published: 2025-11-05
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 some amount of chemical disequilibrium during the segregation of the core in the magma ocean phase. At the minimum equilibrium rate in metal and silicate phases, the final temperature of the core by $\sim$ 250 K compared to the fully equilibrated [...]
Radiogenic Sr-Nd-Pb isotope behavior in different grain-sized fine lithic materials during basalt weathering
Published: 2025-10-15
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: 2025-10-09
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 [...]
Impact of sources and form of Mg on oyster shell Mg/Ca
Published: 2025-09-17
Subjects: Geochemistry
Mg/Ca in bivalve shells has been investigated as a promising temperature proxy, but several studies reported compositional shifts that hamper its accuracy. In particular, several models linking shell Mg/Ca and temperature have been published and an empirical difference in the seasonal amplitudes of shell Mg/Ca has been observed between two types of environmental settings: river output, open [...]
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 [...]