Preprints
Filtering by Subject: Geochemistry
The Byers Basin: Jurassic-Cretaceous tectonic and depositional evolution of the forearc deposits of the South Shetland Islands and its implications for the northern Antarctic Peninsula
Published: 2019-07-31
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy, Tectonics and Structure
This paper addresses the Jurassic–Cretaceous stratigraphic evolution of fore-arc deposits exposed along the west coast of the northern Antarctic Peninsula. In the South Shetland Islands, Upper Jurassic deep-marine sediments are uncomformably overlain by a Lower Cretaceous volcaniclastic sequence that crops out on Livingston, Snow and Low islands. U-Pb zircon ages are presented for the upper [...]
The Gondwanan margin in West Antarctica: insights from Late Triassic magmatism of the Antarctic Peninsula
Published: 2019-07-31
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Triassic orthogneisses of the Antarctic Peninsula provide evidence for the Palaeozoic and Mesozoic geological evolution of southern Gondwana within Pangaea. These rocks are sporadically exposed in southeastern Graham Land and northwestern Palmer Land, although reliable geochronological, geochemical and isotopic data are sparse. We combine new geochronological (LA-ICP-MS zircon U-Pb), geochemical, [...]
Relationships between soil chemical properties and rare earth element concentrations in the aboveground biomass of a tropical herbaceous plant
Published: 2019-07-18
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Physical Sciences and Mathematics
The geochemical behavior of rare earth elements (REE) has been mainly investigated in geological systems where they represent the best proxies for processes occurring at the interface between different media. REE concentrations, normalized with respect to the upper continental crust, were used to assess their behavior. In this study, REE geochemical behavior was investigated in plant shoots of a [...]
δ13C values of bacterial hopanoids and leaf waxes as tracers for methanotrophy in peatlands
Published: 2019-07-09
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Physical Sciences and Mathematics
Methane emissions from peatlands contribute significantly to atmospheric CH4 levels and play an essential role in the global carbon cycle. The stable carbon isotopic composition (δ13C) of bacterial and plant lipids has been used to study modern and past peatland biogeochemistry, especially methane cycling. However, the small number of recent peatlands that have been characterised and the lack of [...]
The impact of Mg2+ ions on equilibration of Mg-Ca carbonates in groundwater and brines
Published: 2019-07-04
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics
At temperatures below 50°C, the Mg2+/Ca2+ values in groundwater and brines, irrespective of their origin - either carbonaceous or siliceous rocks/sediments - show a large spread. As shown by equilibria of surface layer composition of calcite in solutions containing Mg2+ , log10 (aMg2+ /a Ca2+) vary between minus infinity and +2.3, thereby covering thermodynamical equilibria between the minerals [...]
Tracing the migration of mantle CO2 in gas fields and mineral water springs in south-east Australia using noble gas and stable isotopes
Published: 2019-06-19
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics
Geochemical monitoring of CO2 storage requires understanding of both innate and introduced fluids in the crust as well as the subsurface processes that can change the geochemical fingerprint of CO2 during injection, storage and any subsequent migration. Here, we analyse a natural analogue of CO2 storage, migration and leakage to the atmosphere, using noble gas and stable isotopes to constrain the [...]
Stepwise chemical abrasion–isotope dilution–thermal ionization mass spectrometry with trace element analysis of microfractured Hadean zircon
Published: 2019-06-16
Subjects: Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
The Hadean Jack Hills zircons represent the oldest known terrestrial material, providing a unique and truly direct record of Hadean Earth history. This zircon population has been extensively studied via high spatial resolution, high throughput in situ isotopic and elemental analysis techniques such as secondary ionization mass spectrometry (SIMS), but not by comparatively destructive, [...]
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: 2019-05-08
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: 2019-04-29
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 [...]