Preprints
Filtering by Subject: Geochemistry
The link between water and ferric iron in Earth's lower mantle
Published: 2024-10-10
Subjects: Earth Sciences, Geochemistry, Mineral Physics
As the most massive geochemical reservoir, the lower mantle affects Earth's budget of volatile elements, including hydrogen or H2O. The properties of minerals in Earth's lower mantle are further affected by changes in the electronic configurations of iron cations, i.e., spin transitions. Potential feedback between deep H2O retention and spin transitions in mantle minerals, however, remain [...]
Questioning Dark Oxygen Production in the Deep-sea Ferromanganese Nodule Field
Published: 2024-10-04
Subjects: Earth Sciences, Geochemistry, Geology, Oceanography
Previous studies have concluded that the natural process where oxygen is consumed as decomposition of organic matter that supplied from shallow waters occurs on the deep-sea floor. Sweetman et al.1 presented the surprising observation that deep-sea ferromanganese nodules generate oxygen, which they labelled as dark oxygen production. The authors claimed that oxygen was generated through the [...]
Hadean-aged felsic sediments recycled through the deep mantle by early plate tectonics
Published: 2024-10-02
Subjects: Geochemistry, Geology
The unresolved question of when modern tectonic processes arose on Earth has restricted our understanding of how and how quickly Earth reached its present, habitable form. Plate tectonics, and in particular deep subduction, is central to many facets of habitability: it controls heat flow, biogeochemical cycling, and creates a variety of marine and terrestrial biomes that are crucial for [...]
Rapid transformation of biogenic silica to authigenic clay during reverse weathering
Published: 2024-10-01
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, with the timing of the transition from anoxic to oxic deep oceans 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: 2024-09-08
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 [...]
Seamounts control subducted carbonate recycling in Central America – evidence from stable Sr isotopes
Published: 2024-07-12
Subjects: Earth Sciences, Geochemistry, Physical Sciences and Mathematics, Volcanology
Accurate estimates of carbon recycling efficiency at subduction zones are crucial for understanding the long-term evolution of the planet’s climate. Estimating subducting carbon recycling efficiency is difficult, however, due to magmatic degassing deep within the crust. Stable strontium (δ88Sr) isotopes have the potential to serve as an additional proxy for carbonate recycling due to carbonate’s [...]
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 [...]