Preprints
Filtering by Subject: Geochemistry
Fingerprinting fluid source in calcite veins: combining LA-ICP-MS U-Pb calcite dating with trace elements and clumped isotope palaeothermometry
Published: 2020-07-15
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
Application of geochemical proxies to vein minerals - particularly calcite - can fingerprint the source of fluids controlling various important geological processes from seismicity to geothermal systems. Determining fluid source, e.g. meteoric, marine, magmatic or metamorphic waters, can be challenging when using only trace elements and stable isotopes as different fluids can have overlapping [...]
Alkenone isotopes show evidence of active carbon concentrating mechanisms in coccolithophores as aqueous carbon dioxide concentrations fall below 7 µmolL-1
Published: 2020-07-15
Subjects: Biogeochemistry, Climate, Earth Sciences, Geochemistry, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
Coccolithophores and other haptophyte algae acquire the carbon required for metabolic processes from the water in which they live. Whether carbon is actively moved across the cell membrane via a carbon concentrating mechanism, or passively through diffusion, is important for haptophyte biochemistry. The possible utilisation of carbon concentrating mechanisms also has the potential to overprint [...]
Seismological Expression of the Iron Spin Crossover in Ferropericlase in the Earth’s Lower Mantle
Published: 2020-06-29
Subjects: Earth Sciences, Geochemistry, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics, Physics, Quantum Physics, Tectonics and Structure
The two most abundant minerals on Earth which together make up over 90% of the Earth’s lower mantle are (Mg,Fe)O-ferropericlase (Fp) and (Mg,Fe)SiO3-bridgmanite (Bm). Iron in Fp undergoes a high-spin to low-spin (HS-LS) crossover that influences density, viscosity, elasticity, thermal conductivity, and elemental partitioning, however, the predicted effects of this transition are not apparent in [...]
Ancient siderites reveal hot and humid super-greenhouse climate
Published: 2020-06-19
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics
Ancient siderites reveal hot and humid super-greenhouse climate
Methane concentrations in streams reveal gas leak discharges in regions of oil, gas, and coal development
Published: 2020-06-18
Subjects: Earth Sciences, Environmental Indicators and Impact Assessment, Environmental Monitoring, Environmental Sciences, Geochemistry, Oil, Gas, and Energy, Physical Sciences and Mathematics, Water Resource Management
As natural gas has grown in importance as a global energy source, leakage of methane (CH4) from wells has sometimes been noted. Leakage of this greenhouse gas is important because it affects groundwater quality and, when emitted to the atmosphere, climate. We hypothesized that streams might be most contaminated by CH4 in the northern Appalachian Basin in regions with the longest history of [...]
Notes on statistical age dispersion in fission-track datasets: the chi-square test, annealing variability, and analytical considerations
Published: 2020-06-12
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
Notes on fission track statistics, the chi-square test, annealing (i.e. fission track age) variability, and analytical bias aimed at a general Earth scientist audience and for users of fission track data
Ancient siderites reveal hot and humid super-greenhouse climate
Published: 2020-06-10
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
Earth’s climate is warming as the rise in atmospheric CO2 (pCO2) contributes to increased radiative forcing. State-of-the-art models calculate a wide range in Earth’s climate sensitivities due to increasing pCO2, and, in particular, the mechanisms responsible for amplification of high latitude temperatures remain highly debated. The geological record provides a means to evaluate the consequences [...]
Sediment redox dynamics in an oligotrophic deep-water lake in Tierra del Fuego: insights from Fe isotopes
Published: 2020-06-10
Subjects: Earth Sciences, Fresh Water Studies, Geochemistry, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Sedimentology
Fe speciation and Fe isotopes have been widely used to reconstruct past basin dynamics and water redox conditions. However, sedimentation and early diagenesis of such proxies eventually alter any primary climate signal. In this work, we disentangled the processes occurring at the redox front below the sediment-water interface of a ventilated deep-water lake (Lago Fagnano, Argentina/Chile). A [...]
Description of the continuous nature of organic matter in models of soil carbon dynamics
Published: 2020-05-29
Subjects: Applied Mathematics, Earth Sciences, Environmental Microbiology and Microbial Ecology Life Sciences, Geochemistry, Life Sciences, Microbiology, Physical Sciences and Mathematics, Soil Science
The understanding of soil organic matter (SOM) dynamics has considerably advanced in recent years. It was previously assumed that most SOM consisted of recalcitrant compounds, whereas the emerging view considers SOM as a range of polymers continuously processed into smaller molecules by decomposer enzymes. Mainstreaming these new insights in current models is challenging because of their [...]
Preservation of Organic Carbon in Dolomitized Cambrian Stromatolites and Implications for Microbial Biosignatures in Diagenetically Replaced Carbonate Rock
Published: 2020-05-26
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Planetary Geology, Planetary Sciences
Stromatolites have been a major focus in the search for ancient microbial life, however, the organic carbon biosignatures of dolomitized stromatolites have not yet been fully characterized or correlated with their dolomitizing conditions. Although dolomitization rarely preserves microbial morphology, the presence of organic carbon can provide valuable information for characterization of fossils’ [...]
River sediment geochemistry as a conservative mixture of source regions: Observations and predictions from the Cairngorms, UK
Published: 2020-05-25
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics
The elemental composition of sediments in rivers is the product of physical and chemical erosion of rocks, which is then transported across drainage networks. A corollary is that fluvial sedimentary geochemistry can be used to understand geologic, climatic and geomorphic processes. We develop a simple methodology to predict elemental compositions of river sediments from digital elevation data and [...]
Cave airflow patterns control calcite dissolution rates within a cave stream: Blowing Springs Cave, Arkansas, USA
Published: 2020-05-25
Subjects: Earth Sciences, Environmental Sciences, Geochemistry, Geomorphology, Hydrology, Physical Sciences and Mathematics
Erosion rates within streams vary dramatically over time, as differences in discharge and sediment load enhance or inhibit erosion processes. Within cave streams, and other bedrock channels incising soluble rocks, changes in water chemistry are an important factor in determining how erosion rates will vary in both time and space. Prior studies within surface streams, springs, and caves suggest [...]
Upper mantle mush zones beneath low melt flux ocean island volcanoes: insights from Isla Floreana, Galápagos
Published: 2020-05-25
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics, Volcanology
The physicochemical characteristics of sub-volcanic magma storage regions have important implications for magma system dynamics and pre-eruptive behaviour. The architecture of magma storage regions located directly above high buoyancy flux mantle plumes (such as Kīlauea, Hawai’i and Fernandina, Galápagos) are relatively well understood. However, far fewer constraints exist on the nature of magma [...]
Holocene tephrochronology of Kerguelen Archipelago, Subantarctic Indian Ocean
Published: 2020-05-20
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics, Sedimentology, Stratigraphy, Volcanology
Up to now, no geochemical or geochronological data has been published about Holocene volcanic activity on the Kerguelen Archipelago. Here we present the first continuous Holocene chronology of volcanic eruptions on the archipelago. We compared sedimentological, geochronological and geochemical data from two lake sediment cores taken in two different depocenters of Lake Armor, located ca. 70 km [...]
Jarosite formation in deep Antarctic ice provides a window into acidic, water-limited weathering on Mars
Published: 2020-05-20
Subjects: Cosmochemistry, Earth Sciences, Geochemistry, Physical Sciences and Mathematics, Planetary Geochemistry, Planetary Glaciology, Planetary Sciences
Many interpretations have been proposed to explain the presence of jarosite within Martian surficial sediments, including the possibility that it precipitated within paleo-ice deposits owing to englacial weathering of dust. But until now a similar mechanism was not observed on Earth nor in other planetary settings. We report the first multi-analytical indication of jarosite formation within deep [...]