Preprints
Filtering by Subject: Geochemistry
Rapid transformation of biogenic silica to authigenic clay during reverse weathering
Published: 2024-09-30
Subjects: Earth Sciences, Geochemistry
Formation of authigenic clay minerals during early diagenesis of marine sediments, termed “reverse weathering” (RW), is an important process for regulating ocean pH and atmospheric CO2 over geologic time scales. It is also considered a“missing sink” of the modern marine Si cycle. Although the importance of RW has been increasingly recognized, the rate and mechanisms of this process remain [...]
Improved Precision and Reference Materials for Stable Carbon Isotope Analysis in Basaltic Glasses using Secondary Ion Mass Spectrometry
Published: 2024-09-27
Subjects: Earth Sciences, Geochemistry, Volcanology
We introduce three new reference materials and a new high-precision set-up for stable carbon isotope analysis in basaltic glasses using large-geometry secondary ion mass spectrometry (SIMS) instrument. The new hydrous basaltic reference materials, characterised for carbon concentration and isotope composition by step-heating gas extraction and manometry followed by isotope ratio mass [...]
Assessing the timing of deep ocean oxygenation from uranium elemental and isotopic compositions of ophiolites
Published: 2024-09-26
Subjects: Earth Sciences, Geochemistry, Geology
The concentration of dissolved oxygen in the deep oceans has varied over Earth History, but the timing of the transition from anoxic to oxic deep oceans is debated. Under modern-day, oxic, deep ocean conditions, alteration of the upper sections of mafic oceanic crust with U-rich seawater leads to U enrichment, low Th/U ratios, and heterogeneous 238U/235U ratios relative to fresh mid-ocean ridge [...]
Nd isotopic equilibration during channelized melt transport through the lithosphere: a feasibility study using idealized numerical models
Published: 2024-09-12
Subjects: Earth Sciences, Geochemistry
Abstract {This study is motivated by the observed variability in trace element isotopic and chemical compositions of primitive (SiO$_2<$52 wt \%) basalts in southwest North America (SWNA) during the Cenozoic transition from subduction to extension. Specifically, we focus on processes that may explain the enigmatic observation that in some localities, basalts with low Ta/Th, consistent with [...]
Competitive and Cooperative Effects of Chloride on Palladium(II) Adsorption to Iron (Oxyhydr)oxides: Implications for Mobility During Weathering
Published: 2024-09-10
Subjects: Geochemistry
In surface and near-surface weathering environments, the mobilization and partial loss of palladium (Pd) under oxidizing and weakly acidic conditions has been attributed to aqueous chloride complexation. However, prior work has also observed that a portion of Pd is retained by iron (oxyhydr)oxides in the weathering zone. The effect chloride has on the relative amount of Pd mobilization versus [...]
Evidence supporting a broader than previously thought influence of solar activity over Earth system’s processes. Discussion of a possible mechanism.
Published: 2024-09-07
Subjects: Atmospheric Sciences, Earth Sciences, Geochemistry, Geology, Geophysics and Seismology, Meteorology, Oceanography and Atmospheric Sciences and Meteorology, Other Earth Sciences, Tectonics and Structure, Volcanology
In this article, I show lines of evidence supporting a modulation of volcanic activity and some weather phenomena by solar wind conditions in the near-Earth environment. On a daily timescale, a correlation is found between the LP earthquake activity of Kilauea volcano, related to magma transport, and the Bx component of the interplanetary magnetic field as measured in the OMNI database for [...]
Critical Review of the Article: "Evidence of Dark Oxygen Production at the Abyssal Seafloor" by Sweetman et al. in Nat. Geosci. 1–3 (2024)
Published: 2024-08-12
Subjects: Geochemistry
This review examines the findings and methodologies presented in Sweetman et al. (2024) (hereafter referred to as ‘the paper’). The paper presents findings contrasting those of all previous comparable work and has stirred international debate pertaining to deep-sea minerals. We identify significant issues in data collection, validation, and interpretation including unvalidated data collection [...]
Alteration processes of mantle peridotite in the Samail ophiolite inferred from independent component analysis of rock physical properties
Published: 2024-07-27
Subjects: Geochemistry, Mineral Physics, Multivariate Analysis
To quantify the alteration processes of mantle from geophysical data, an understanding of the relationship between alteration and the physical properties of mantle peridotite is essential. In this study, we employed independent component analysis (ICA) to evaluate variations in the physical properties of altered peridotites collected by the Oman Drilling Project, to understand the alteration [...]
Volcanic arc structure controlled by liquid focusing from the slab — evidence from boron isotopes and trace elements
Published: 2024-07-16
Subjects: Earth Sciences, Geochemistry, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Volcanology
The rates and pathways of material transport from subducting plates to arc volcanoes control the long-term chemical evolution of the atmosphere, continents, and mantle. Arc magma compositions are commonly used as proxies for the state of the slab directly below a volcanic vent, under the assumption of vertical transport from the slab to the surface. Here, we present new boron (B) isotope and [...]
Trace element and stable Sr isotope evidence for seamount-driven variations in subducted sediment and carbon recycling in Central America
Published: 2024-07-12
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics, Volcanology
Subduction zone fluxes control the long-term evolution of Earth’s interior, surface reservoirs, and climate. Tobetter constrain these fluxes, we present new δ⁸⁸Sr measurements of lavas and sediments from Nicaragua, a keysite of carbonate subduction. δ⁸⁸Sr data are interpreted alongside existing trace element data to assess the valueof Sr stable isotopes as a quantitative subduction tracer. Trace [...]
Interdiffusion of major elements at 1 atmosphere between natural shoshonitic and rhyolitic melts
Published: 2024-07-12
Subjects: Earth Sciences, Geochemistry, Volcanology
The diffusive mass exchange of eight major elements (Si, Ti, Al, Fe, Mg, Ca, Na, and K) between natural, nominally dry shoshonitic and rhyolitic melts was studied at atmospheric pressure and temperatures between 1230 and 1413 °C using the diffusion couple method. For six elements, effective binary diffusion coefficients were calculated by means of a concentration-dependent method to obtain an [...]
Pre-Cordilleran mantle metasomatism preserved in alkali basalts of Isla Isabel, México
Published: 2024-07-09
Subjects: Geochemistry, Geology
The presence of HIMU (high-238U/204Pb) signatures in ocean island basalts has long been used to argue that ancient oceanic crust has been tectonically recycled into the mantle sources of plume-derived volcanic hotspots such as St. Helena or Mangaia. However, alternative hypotheses regarding the origins of HIMU signatures have also been put forward. This paper addresses the origins of HIMU-like Pb [...]
Uranium-series isotopes as tracers of physical and chemical weathering in glacial sediments from Taylor Valley, Antarctica
Published: 2024-07-04
Subjects: Earth Sciences, Geochemistry, Glaciology, Soil Science
The McMurdo Dry Valleys of Antarctica formed by extensive glacial erosion, yet currently exhibit hyperarid polar conditions characterized by limited chemical and physical weathering. Efficient chemical weathering occurs when moisture is available, and polythermal subglacial conditions may accommodate ongoing mechanical weathering and valley incision. Taylor Valley hosts several Pleistocene [...]
Shallow storage conditions at Krafla IDDP-1 revealed by rhyolite-MELTS geobarometry, and implications for global shallow magmatism
Published: 2024-06-24
Subjects: Earth Sciences, Geochemistry, Geology, Other Earth Sciences, Volcanology
Identifying the storage depths of melt-dominated magma bodies prior to eruption is critical for understanding magma transport, eruption hazards, and magma body longevity. Rhyolite-MELTS has been used effectively to calculate pre-eruptive storage pressures for silicic magma bodies in the upper crust (~100-350 MPa), but its precision and accuracy in very low-pressure systems (<100 MPa) has not [...]
Diversity at Goldschmidt conference
Published: 2024-06-19
Subjects: Biogeochemistry, Cosmochemistry, Earth Sciences, Geochemistry, Planetary Biogeochemistry, Planetary Geochemistry, Planetary Sciences
The field of geochemistry has grown significantly over the past seventy years, contributing to our understanding of Earth's processes. However, geochemists often identify with broader fields like geology or oceanography, reflecting an identity crisis within the discipline. The Goldschmidt Conference, established in 1988, serves as a central international meeting for geochemists, promoting their [...]