Preprints
Filtering by Subject: Geochemistry
The missing carbon budget puzzle piece: shallow-water hydrothermal vents contribution to global CO2 fluxes
Published: 2022-11-08
Subjects: Earth Sciences, Geochemistry, Geology, Planetary Biogeochemistry, Volcanology
The release of CO2 gases from volcanoes and their secondary geothermal manifestations are an important contributor to the global carbon budget. While degassing from mid ocean ridges is relatively well-constrained, the contribution of shallow submarine volcanic degassing to the atmosphere is less clear. Shallow-water hydrothermal vents are common seafloor features present at depths shallower than [...]
Oceanic redox conditions during the terminal Cambrian extinction event
Published: 2022-11-05
Subjects: Geochemistry
Marine animal diversity during the late Cambrian was reduced by a series of extinctions that have generally been attributed to oceanic anoxic events associated with positive carbon isotope excursions. Here we present carbon and uranium isotope ratios (δ13C and δ238U values) as proxies for global carbon cycle and oceanic redox conditions, respectively, from carbonate rocks of the Wa’ergang [...]
Short Communication: The Wasserstein distance as a dissimilarity metric for comparing detrital age spectra, and other geological distributions
Published: 2022-10-26
Subjects: Earth Sciences, Environmental Sciences, Geochemistry, Geology, Geomorphology, Stratigraphy, Tectonics and Structure
Distributional data such as detrital age populations or grain size distributions are common in the geological sciences. As analytical techniques become more sophisticated, increasingly large amounts of distributional data are being gathered. These advances require quantitative and objective methods, such as multidimensional scaling (MDS), to analyse large numbers of samples. Crucial to such [...]
Experimental comparisons of carbonate-associated sulfate extraction methods
Published: 2022-10-26
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
Carbonate-associated sulfate (CAS) refers to trace amounts of sulfate incorporated into carbonate minerals during precipitation. CAS has been the most commonly used approach to recover the paleo-seawater sulfate sulfur isotope composition (δ34Ssw) as carbonate rocks are more common and occur in less restricted marine environments than alternative sulfate-bearing minerals (such as gypsum and [...]
Multiple ocean oxygenation events during the Ediacaran Period: Mo isotope evidence from the Nanhua Basin, South China
Published: 2022-10-24
Subjects: Earth Sciences, Geochemistry, Geology
The Ediacaran Period (ca. 635–539 Ma) was an eventful interval in Earth history, during which a succession of biological and environmental changes, including episodic ocean oxygenation events (OOEs), may have paved the way for the Cambrian radiations of animal life. To better understand the evolution of ocean redox conditions and to estimate the extent of seafloor oxygenation during this period, [...]
Deterministic icehouse and greenhouse climates throughout Earth history
Published: 2022-10-06
Subjects: Climate, Geochemistry
Some theories posit that icehouse (with polar ice sheets) and greenhouse (ice-free) states throughout Earth history are not deterministic, but bistable—both states may occur for the same level of radiative forcing. If correct, then the climate state that persists for millions of years can depend on which state already existed, giving the system a `memory’ effect. However, on these timescales the [...]
Geochemical mapping by unmixing alluvial sediments: An example from northern Australia
Published: 2022-10-01
Subjects: Earth Sciences, Environmental Monitoring, Environmental Sciences, Geochemistry, Geomorphology, Natural Resource Economics, Sedimentology, Soil Science, Water Resource Management
Alluvial sediments have long been used in geochemical surveys as their compositions are assumed to be representative of areas upstream. Overbank and floodplain sediments, in particular, are increasingly used for regional to continental-scale geochemical mapping. However, during downstream transport, sediments from heterogeneous source regions are carried away from their source regions and mixed. [...]
Comparative study of alteration sequences in pegmatitic aluminium phosphates
Published: 2022-09-29
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics, Other Earth Sciences
Aluminium phosphates are mineral phases commonly occurring in rare-element pegmatites that record initial magmatic crystallization, metasomatic and hydrothermal replacements and precipitation and low-temperature alteration. Here we perform a comparative mineralogical study between several localities to assess similarities and variations in these parageneses and establish a general alteration [...]
All aboard! Earth system investigations with the CH2O-CHOO TRAIN v1.0
Published: 2022-09-24
Subjects: Climate, Earth Sciences, Geochemistry, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
Models of the carbon cycle and climate on geologic (>10^4 year) timescales have improved tremendously in the last 50 years due to parallel advances in our understanding of the Earth system and the increase in computing power to simulate its key processes. Despite these advances, balancing the Earth System's vast complexity with a model's computational expense is a primary challenge in model [...]
Characterisation of phosphate mineralogy in Montebras-en-Soumans Pegmatite, Massif Central, France
Published: 2022-09-22
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics
Montebras-en-Soumans pegmatitic cupola hosts large pods of phosphate composed of primary amblygonite-montebrasite. These aluminium phosphate masses are considerably altered by post-magmatic processes producing a number of secondary metasomatic hydrothermal phosphates (lacroixite, wardite, morinite, viitaniemiite, apatite, triplite, eosphorite) and low-temperature phosphates (apatite, crandallite, [...]
python-ags4: A Python library to read, write, and validate AGS4 geodata files
Published: 2022-09-21
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Environmental Engineering, Geochemistry, Geology, Geophysics and Seismology, Geotechnical Engineering
Data gathered from geotechnical, geoenvironmental, and geophysical investigations can be broadly described as "geodata". The AGS4 data format is one of the most widely used data transmittal formats for geodata and is used across the world. It is a plain text format consisting of multiple tables of comma-separated values, tied together with a robust data schema and a comprehensive suite of [...]
North Atlantic Drift Sediments Constrain Eocene Tidal Dissipation and the Evolution of the Earth-Moon System
Published: 2022-09-15
Subjects: Geochemistry, Geology, Sedimentology, Stratigraphy
Cyclostratigraphy and astrochronology are now at the forefront of geologic timekeeping. While this technique heavily relies on the accuracy of astronomical calculations, solar system chaos limits how far back astronomical calculations can be performed with confidence. High-resolution paleoclimate records with Milankovitch imprints now allow reversing the traditional cyclostratigraphic approach: [...]
A genetic model of the magnetite-apatite deposits on El Laco volcano by extrusion of iron-rich melt
Published: 2022-08-25
Subjects: Dynamical Systems, Earth Sciences, Fluid Dynamics, Geochemistry, Geology, Numerical Analysis and Scientific Computing, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Magnetite-apatite deposits are important sources of iron and other metals. A prominent exam- ple are the magnetite lavas at the El Laco volcano, Northern Chile. Their formation processes remain debated. Here, we test the genetic hypothesis that an Fe-rich melt separated from silicate magma and ascended along collapse-related fractures. We complement recent analy- ses with thermodynamic modelling [...]
Sampling across large-scale geological gradients to study geosphere-biosphere interactions
Published: 2022-07-25
Subjects: Biogeochemistry, Earth Sciences, Environmental Sciences, Geochemistry, Life Sciences, Microbiology
Despite being one of the largest microbial ecosystems on Earth, with >1029 microbial cells, many basic open questions remain about how life exists and thrives in the deep subsurface biosphere, inside Earth’s crust. Much of this ambiguity is due to the fact that it is exceedingly difficult and (often prohibitively expensive) to directly sample the deep subsurface, requiring elaborate drilling [...]
Evaluation of preservation protocols for oxygen-sensitive minerals within laminated aquatic sediments
Published: 2022-07-25
Subjects: Biogeochemistry, Environmental Sciences, Geochemistry, Sedimentology
Laminated sediments can record seasonal changes in sedimentation of material from anoxic waters, including minerals of the redox-sensitive elements Fe, Mn, and S that form under varying oxygen levels, mineral saturation conditions, and from microbial metabolism. However, preserving both the oxygen-sensitive minerals for identification is challenging when preservation of the spatial arrangement of [...]