Preprints
Filtering by Subject: Geochemistry
Evaluating the relationship between the area and latitude of large igneous provinces and Earth’s long-term climate state
Published: 2019-06-12
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Tectonics and Structure
One of the hypothesized effects of large igneous provinces (LIPs) is planetary cooling on million-year timescales associated with enhanced silicate weathering of the freshly-emplaced basalt. This study combines reconstructions of the original surface extent and emplacement ages of LIPs, a paleogeographic model, and a parameterization of LIP erosion to estimate LIP area in all latitudinal bands [...]
Comments on, Scaled Random Number Simulation of High Correlation Coeffieients for Gasoline Range Compound Concentrations (unpublished results), disclosed in EarthArXiv, 5 April, 2019, by Lloyd R. Snowdon.
Published: 2019-05-30
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics
The paper comments on disclosure EarthArXiv 5 April, 2019 by L. R. Snowdon discounting correlations between light hydrocarbons suggesting steady-state catalysis in the origin of petroleum. The correlations are shown to be valid and Snowdons arguments not relevant.
A constant Chinese Loess Plateau dust source since the Late Miocene
Published: 2019-05-30
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
The Pliocene-Pleistocene boundary marks a major change in global climate and East Asian monsoon dynamic. However, the role of the global atmospheric dust-cycle over this time is unclear; in particular, whether, changes in the dust cycle influenced climate change, or resulted from it. Chinese loess records past dust-cycle history and the influences of aridification and monsoon circulation over the [...]
Effect of solution chemistry on the iodine release from iodoapatite in aqueous environments
Published: 2019-05-24
Subjects: Chemistry, Earth Sciences, Geochemistry, Materials Chemistry, Physical Sciences and Mathematics
To ensure the safe disposal of nuclear waste, understanding the release process of radionuclides retained in the nuclear waste forms is of vital importance. Iodoapatite Pb9.85(VO4)6I1.7, a potential waste form for iodine-129, was selected as a model system for ceramic waste forms in this study to understand the effect of aqueous species on iodine release. Semi-dynamic leaching tests were [...]
Three Billion Year Secular Evolution of the Triple Oxygen Isotope Composition of Marine Chert
Published: 2019-05-07
Subjects: Earth Sciences, Geochemistry, Other Earth Sciences, Physical Sciences and Mathematics
The 18O/16O ratios of ancient marine minerals show a puzzling increase over geologic time. Long-term changes in temperature, seawater 18O/16O ratios, and post-depositional overprinting can all explain this trend, but few tracers can distinguish between these scenarios. Here, we report high-precision 18O/16O and 17O/16O ratios of cherts through 3.4 Ga of Earth′s history. We find that Phanerozoic [...]
Microstructural Constraints on Magmatic Mushes under Kīlauea Volcano, Hawaiʻi
Published: 2019-05-06
Subjects: Earth Sciences, Geochemistry, Geology, Mineral Physics, Physical Sciences and Mathematics, Volcanology
Distorted olivines of enigmatic origin are ubiquitous in erupted products from a wide range of volcanic systems (e.g., Hawaiʻi, Iceland, Andes). Investigation of these features at Kīlauea Volcano, Hawai’i, using an integrative crystallographic and chemical approach places quantitative constraints on mush pile thicknesses. Electron back-scatter diffraction (EBSD) reveals that the microstructural [...]
Terrestrial environmental change across the onset of the PETM and the associated impact on biomarker proxies: a cautionary tale
Published: 2019-04-28
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
The Paleocene-Eocene Thermal Maximum (PETM; ~ 56 million years ago (Ma) is the most severe carbon cycle perturbation event of the Cenozoic. Although the PETM is associated with warming in both the surface (~up to 8°C) and deep ocean (~up to 5°C), there are relatively few terrestrial temperature estimates from the onset of this interval. The associated response of the hydrological cycle during the [...]
A long-term, high-latitude record of Eocene hydrological change in the Greenland region
Published: 2019-04-26
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
A range of proxy approaches have been used to reconstruct short-term changes to Earth’s hydrological cycle during the early Eocene hyperthermals. However, little is known about the response of Earth’s hydrological and biogeochemical systems to long-term Cenozoic cooling, which began following the Early Eocene Climatic Optimum (53.3 – 49.4 million years ago; Ma). Here, we use the molecular [...]
Anomalous structure of MgCO3 liquid and the buoyancy of carbonatite melts
Published: 2019-04-23
Subjects: Earth Sciences, Geochemistry, Mineral Physics, Physical Sciences and Mathematics
MgCO3 is one of the most important components of mantle-derived carbonatite melts, and yet also one of the most difficult to study experimentally. Attempts to constrain its thermodynamic properties are hampered by decarbonation, which occurs at only ~500 °C, far below its metastable 1 bar melting temperature. Molecular dynamic simulations, however, can predict the thermodynamic properties of the [...]
Scaled Random Number Simulation of High Correlation Coefficients for Gasoline Range Compound Concentrations
Published: 2019-04-05
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics
It has been common practice to plot gasoline range parameters as absolute concentrations within crude oils of either single compounds, sums of compound pairs, or the square root of the products of concentrations of compounds. If a sample of crude such as a condensate has a relatively high concentration of volatile components, then the concentration of all of the gasoline range components tends to [...]
Determining cooling rates from mica 40Ar/39Ar thermochronology data: effect of cooling path shape
Published: 2019-04-02
Subjects: Earth Sciences, Geochemistry, Geology, Other Earth Sciences, Physical Sciences and Mathematics
Tectonic models are commonly underpinned by metamorphic cooling rates derived from diffusive-loss thermochronology data. Such cooling ages are usually linked to temperature via Dodson’s 1973 closure temperature (TC) formulation, which specifies a 1/time-shaped cooling path. Geologists, however, commonly discuss cooling rates as a linear temperature/time shape. We present the results of a series [...]
A macroscale hydrogeological numerical model of the Suio hydrothermal system (central Italy)
Published: 2019-04-01
Subjects: Earth Sciences, Environmental Sciences, Geochemistry, Geology, Natural Resources and Conservation, Physical Sciences and Mathematics, Water Resource Management
The complex behaviour of the Suio hydrothermal system (central Italy) and its potential exploitation as a renewable energy source are still unclear. To quantitatively evaluate the geothermal resource, the Suio hydrothermal system has been investigated with a hydrogeological numerical model that couples fluid flow, thermal convection, and transport of diluted species inside a hybrid [...]
Direct observations of the coupling between quartz dissolution and Mg-silicate formation
Published: 2019-03-19
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
Although quartz is a stable mineral at Earth surface conditions, field samples have shown its rapid dissolution in combination with the precipitation of Mg-silicate phases. Atomic force microscopy (AFM) experiments were performed to investigate the dissolution of quartz and the precipitation of secondary phases in high-pH, Mg-rich solutions both in-situ and ex-situ. Experiments were conducted at [...]
New insights on lake sediment DNA from the catchment: importance of taphonomic and analytical issues on the record quality
Published: 2019-02-27
Subjects: Earth Sciences, Ecology and Evolutionary Biology, Geochemistry, Geology, Life Sciences, Physical Sciences and Mathematics, Sedimentology, Soil Science, Terrestrial and Aquatic Ecology
Over the last decade, an increasing number of studies have used lake sediment DNA to trace past landscape changes, agricultural activities or human presence. However, the processes responsible for lake sediment formation might affect DNA archiving via taphonomic and analytical processes. It is crucial to understand these processes to ensure reliable interpretations for “palaeo” studies. Here, we [...]
Core Formation and Geophysical Properties of Mars
Published: 2019-02-25
Subjects: Earth Sciences, Geochemistry, Mineral Physics, Physical Sciences and Mathematics, Planetary Geophysics and Seismology, Planetary Sciences
The chemical and physical properties of the interiors of terrestrial planets are largely determined during their formation and differentiation. Modeling a planet’s formation provides important insights into the properties of its core and mantle, and conversely, knowledge of those properties may constrain formational narratives. Here, we present a multi-stage model of Martian core formation in [...]