In the Earth’s crust, Ni is generally concentrated in mafic and ultramafic rocks and is coupled with Mg in Mg-olivine, Mg-pyroxene and spinel. Whether the Ni-rich, and in general, the mafic component of Australasian tektites and microtektites is terrestrial or meteoritic is still debated. To test the origin of the Ni-rich component, we studied the Ni versus Mg distribution in a large geochemical database

While nitrate (NO3-) serves as a vital nutrient for soil organisms, the lack of knowledge on its sources and cycling in Antarctic soils does not allow to predict the possible effects of climate and environmental changes on the functioning of terrestrial ecosystems. Thus, the NO3- and its stable isotopes of Δ17ONO3, δ15NNO3, and δ18ONO3 were analyzed in Antarctic soils, collected in coastal ice-free

Barium isotopes have been increasingly applied to trace igneous processes, but the applications are hindered by the lack of equilibrium Ba isotope fractionation factors between silicate minerals. In this study, the reduced partition function ratios (RPFRs) of the major Ba-hosting silicate minerals, including muscovite, phlogopite, tremolite, richterite, microcline, albite, and epidote, as well as witherite

Large Arctic rivers are an important source of iron (Fe) to the Arctic Ocean, though seasonal variations in the terrestrial source and supply of Fe to the ocean are unknown. To constrain the seasonal variability, we present Fe concentrations and isotopic compositions (δ56Fe) for particulate (> 0.22 µm) and colloidal (< 0.22 µm – 1kDa) Fe from the Lena River, NE Russia. Samples were collected every

Uranium is a redox-sensitive trace element that under certain sedimentary conditions will reflect changes in past biological productivity and/or deep ocean ventilation. Applications for the isotopic composition of U (234U:238U activity ratio, δ234U or the per mil deviation from secular equilibrium) as a paleoceanographic proxy, however, remain largely unexplored in pelagic sediments. We present δ234U

Branched and isoprenoidal glycerol dialkyl glycerol tetraethers (br- and isoGDGTs) are membrane lipids produced by bacteria and archaea, respectively. These lipids form the basis of several frequently used paleoclimatic proxies. For example, the degree of methylation of brGDGTs (MBT’5Me) preserved in mineral soils (as well as peats and lakes) is one of the most important terrestrial paleothermometers

The geochemistry of Ba is commonly used to study igneous processes and fluid-melt interaction in subduction zone and granitic environments. Recent advances in analytical techniques have also indicated that Ba isotope geochemistry has the potential to significantly augment these studies. Understanding the Ba isotope fractionation mechanisms is thus critical if this potential is to be fully realized

Exposed and un-remediated metal(loid)-bearing mine tailings are susceptible to wind and water erosion that disperses toxic elements into the surrounding environment. Compost-assisted phytostabilization has been successfully applied to legacy tailings as an inexpensive, eco-friendly, and sustainable landscape rehabilitation that provides vegetative cover and subsurface scaffolding to inhibit offsite

Large-scale helium accumulations are rarely reported in tectonically active continental subduction zones. This study shows geochemical variations in helium and other volatiles (N2, CO2, Ne and Ar) in hot springs from the India–Asia continental convergent margin (Indus–Yarlung suture, IYS) to the intracontinental extensional region in southern Tibet and identifies a 1200-km-long helium enrichment zone

Selenium (Se) isotopes have recently emerged as a potential proxy for tracing biogeochemical processes and reconstructing the evolution of global Se cycle in the oceans. However, little is known about Se isotope fractionation mechanism during the sequestration of dissolved Se oxyanions by marine ferromanganese oxides that are mainly composed of Fe and Mn (oxyhydr)oxides. Here we elucidate the molecular

Schwertmannite affects the mobility of antimony (Sb) in acid mine drainage, yet the Sb sorption mechanism remains elusive. In this study, the molecular-level mechanism and the driving force of Sb(V) immobilized on schwertmannite were investigated by a combination of wet chemistry, extended X-ray absorption fine structure (EXAFS) analysis, density functional theory (DFT) calculations, and a surface

Carbon dioxide removal (CDR) technologies at a gigaton scale need to be developed and implemented within the next decades to keep global warming below 1.5 °C. Coastal enhanced silicate weathering is one of the proposed CDR techniques that aims to accelerate the natural process of CO2-sequestration during marine chemical weathering of silicate minerals. To this end, finely ground rock containing olivine

Clay minerals and cyanobacteria occur ubiquitously in nature, and both independently influence trace metal cycling due to their high specific surface areas and reactivity. Although the surface reactivity of each is well-studied, the reactivity of clay-cyanobacterial aggregates has received less attention. Here, we performed potentiometric acid-base titrations and Cd adsorption experiments on various

The cumulative effects of heating, various melts/fluids, and tectonic stress from plume and convergent events can produce complex geochemical signatures in circum-cratonic mantle domains. The lithospheric mantle beneath the northwestern Tarim Craton witnessed the Tarim plume and multi-stage convergent events, thus providing a good opportunity to investigate the depletion and enrichment of circum-craton

The element release rates from naturally altered basalts were measured in batch experiments at 27 °C, and in mixed-flow experiments at 25 °C in reactive fluids initially consisting of pH 3 or 4 aqueous solutions. The basalts reacted in this study consist of 1) surface weathered basalts ranging in age up to 13 million years, and 2) hydrothermally altered basalts from zeolite to actinolite alteration

Slab dehydration at subduction zones has broad implications for arc magmatism, mantle heterogeneity and elemental cycling. We present the petrography, mineral chemistry and whole-rock potassium (K) and lithium (Li) isotopic compositions of subducted metabasites exhumed from serpentinite mud volcanoes from the Mariana forearc that were recovered during International Ocean Discovery Program Expedition

Position-specific (PS) carbon isotope compositions of light hydrocarbons such as propane and butane isomers (n-butane and i-butane) can provide a wealth of information on the history of natural gases in the subsurface reservoirs and other environments. For PS carbon isotope analysis of butane isomers, we have established a GC-pyrolysis-GC-isotope ratio mass spectrometry method with demonstrated accuracy

Exfiltration of anoxic phosphate-rich groundwater into surface water leads to the oxidation of dissolved Fe(II) and the formation of Fe(III)-precipitates that can retain phosphate (PO4) and thereby attenuate eutrophication. Fresh Fe(III)-precipitates transform into more stable phases over time, and retained PO4 may be released again. In parallel, CO2 outgassing can promote the formation of Ca-phosphates

It has been estimated that the acid mine drainage (AMD) impacted Odiel river basin in southern Spain supplies 0.37% and 15% of the global riverine fluxes of Cd and Zn to the oceans, respectively (Sarmiento et al., 2009). However, the behaviour of Cd and Zn in the Ria of Huelva estuary, which connects the Odiel and Tinto watersheds with the Gulf of Cadiz, has yet to be fully investigated. Furthermore

The occurrence of manganese (Mn) oxides on Mars is believed to be an indicator of an O2-rich paleoenvironment of Mars because Mn oxides often form through the oxidation of Mn(II) by O2 on the surface of Earth. An alternative formation pathway was recently proposed, in which Mn(II) is oxidized by bromate (BrO3-), a common oxidant in contemporary Martian regolith. However, the oxidation of Mn(II) by

The group 13 elements Ga and In are overabundant in bulk silicate Earth (BSE) when compared to lithophile elements of similar 50% nebular condensation temperature Tc50. To understand whether evaporation from silicate melts provides a more accurate description of volatility during the later stages of planetary accretion, namely, at higher temperatures and oxygen fugacities than in the solar nebula,

Nepheloid layers and turbidity currents transport large quantities of detrital sediments to deep-sea basins. Locally they may control seawater – detrital particle interactions and modify dissolved REE concentrations and εNd distributions of the oceanic margin. However, to date, such processes have been poorly documented, especially in oceanic margins characterized by contrasted mineralogical compositions

Heavy rare earth elements (HREE) are currently in high demand for use in high technology, renewable energy and low-carbon transport, but they are the least abundant in nature. Carbonatites are the primary source of REE; however, they are dominated by light REE (LREE). It remains unknown whether carbonatites have the potential to form economic HREE mineralization. Here we report a xenotime-bearing carbonatite

To investigate the use of cerium (Ce) in the upper continental crust (UCC) for tracing oxidative weathering, we measured the Ce anomaly (Ce/Ce*), the Ce stable isotope composition (δ142Ce), and the average Ce valence state (Ce#) in twenty-four glacial diamictite composites with depositional ages ranging from ∼2.9 to 0.3 Ga. We observe no distinguishable secular changes in Ce/Ce* (Ce/Ce* = 0.87–0.97)

Abstract not available

Micrometeorites (MMs) recovered from the Earth’s surface may have undergone significant changes prior to their collection, including weathering while residing in the terrestrial environment. These alteration processes, such as the precipitation of hydrous phases, may overprint both primary and atmospheric entry features, obscuring pre-existing material properties. In addition, weathering exerts a prominent

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are membrane-spanning lipids produced by bacteria that are ubiquitous in natural sedimentary archives and preserved over geologic timescales. The main influence on their distributions in the environment appears to be temperature, thus making them a potentially powerful proxy for paleotemperature reconstruction. Application of recent lacustrine

We have analyzed concentrations of Mo, Re and U in the suspended particles, water column, underlying carbonate-dominated sediments and pore waters of two contrasting marine lakes situated on the Adriatic Coast of Croatia. Our data are the first for Re in these lakes. Rogoznica Lake is mainly euxinic, but subject to occasional oxygenation events, whereas Mljet Island’s Malo Jezero is currently oxic

Giant clams are reef-dwelling bivalves that reach unusual sizes through a partnership with photosymbiotic algae. To date, no shell-based biogeochemical proxy has been found which directly records the photosymbiotic development and health of these animals. We present new results showing a size-related decline in nitrogen isotopic values of shell-bound organic matter from the hinge layers of giant clams

The U(Pb)-Pb age of zircon is commonly used to represent the crystallization age for igneous rocks due to its high closure temperature and robust resistance to impact disturbance. However, no zircon crystallization age has yet been reported for Chang'e-5 (CE-5) basalt due to their limited occurrence in mare basalt. In this study, rare zircon grains from CE-5 lunar samples were investigated by the in-situ

In continuation of our comprehensive study of the carbonaceous chondrites, we here present data for the CM chondrites. Our study’s aim is to determine the abundances and the average elemental compositions of the major and minor chondritic components. The overarching goal has been to explore the fundamental question of whether chondrules and matrix are complementary, i.e., genetically related, or if

Halogens are powerful tracers for the accretion of Earth’s volatiles. Their sensitivity to Earth’s differentiation, such as core formation, magma ocean crystallization, and planetary evaporation allows us to track such major events and the origin of Earth’s building blocks. Here we examine the role of magma ocean crystallization in fractionating F/Cl ratio of the BSE by experimentally determining the

To examine the alteration of river-derived sediments through a large estuary and the implications for elemental cycling and global climate, this study analyses lithium (Li) isotopes and elemental concentrations (e.g., Li, Na, Mg, K, Ca, Fe and Al) of both the dissolved load and different phases of the sediment load (i.e., exchangeable, carbonate, oxide, clay and residue) in the Amazon estuary. The

Sedimentary molybdenum (Mo) and uranium (U) enrichments have been widely used as a proxy for redox conditions in oxygen-depleted marine paleo-environments. However, in a dynamic upwelling system the seasonal fluctuations from oxic to completely anoxic-sulfidic bottom waters and lateral sediment transport can modify the primary Mo and U signal of the sediment, which in turn may impact paleo-redox interpretations

Photochemical transformation is a critical geochemical fate of terrestrial dissolved organic matter (DOM) that drains from forests to downstream water bodies. However, the photo-degradability and photo-transformation of terrestrial DOM from various sources are yet to be explored. Here, optical spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry were used to analyze photochemical

Marine barite is commonly used as a proxy to reconstruct past ocean productivity. Its distribution in the water column mirrors organic carbon fluxes since it precipitates within microenvironments in decomposing organic matter aggregates. Barite and barium proxies are therefore used to study various aspects of organic matter remineralization and the marine carbon cycle. Barite naturally occurs in a

In order to better constrain the Mg isotopic composition of the mantle, we have analysed twenty-eight samples of both oceanic and continental peridotite using a high-precision, critical mixture double spiking approach. The unaltered samples show no variability δ26Mg in outside analytical uncertainty and yield a value of −0.236 ± 0.006‰ (2 s.e.) for the accessible mantle, substantiating its non-chondritic

Strontium partitioning and isotope fractionation between aragonite and fluid have been determined experimentally at low values of the fluid saturation state (Ω) with respect to this mineral (1.1 ≤ Ωaragonite ≤ 2.2), and the measured isotope fractionation has been compared with the results of first-principles simulations. For the latter, Density Functional Theory (DFT) was used for estimation of the

Mare basalts collected at the Apollo 15 landing site can be classified into two groups. Based on differing whole-rock major element chemistry, these groups are the quartz-normative basalt suite and the olivine-normative basalt suite. In this study we use modelling of Fe-Mg interdiffusion in zoned olivine crystals to investigate the magmatic environments in which the zonation was formed, be that within

Coral reefs are marine environments where calcium carbonate production and dissolution along with photosynthesis and respiration can have a large impact on the daily biogeochemical cycles of seawater dissolved inorganic carbon (DIC), total alkalinity (TA), oxygen (O2), and major nutrients. Using seawater samples from Tetiaroa Atoll, French Polynesia, we apply isotope dilution thermal ionization mass

The isotopic analysis of moderately volatile elements such as K have gained significant interest in recent years as they possess the potential to help us better understand solar system formation. Even so, the precise K isotopic composition of CI chondrites, the most chemically primitive chondrite, has remained elusive. As the K elemental composition of CI chondrites matches well with the solar photosphere

Copper is a redox variable element that may occur as Cu0, Cu+, and Cu2+ in the Earth’s crust. The oxidation state will affect its partitioning between coexisting minerals, melts and fluids and hence its behaviour in magmatic processes. Copper bearing silicate glasses were quenched from melts with 23 synthetic compositions (19 CaO-Na2O-MgO-Al2O3-SiO2, two “granites” containing K2O±H2O, and Fe-bearing

Vanadium (V) is a redox-sensitive trace metal that typically exists in one of three oxidation states (+3, +4 and +5) in natural waters; a feature increasingly used in paleoredox studies of ancient marine sediments. However, our knowledge of V geochemistry in low-oxygen marine environments is still limited, especially regarding interactions of V with reduced iron minerals such as green rust. Carbonate

The stable oxygen and clumped isotope composition of brachiopod calcite are important proxies for the reconstruction of Phanerozoic seawater temperatures and δ18O values. The utility of brachiopods as a temperature archive is nonetheless challenged by indications that their shells precipitate out of isotopic equilibrium with ambient seawater, though the origin of disequilibrium effects has remained

Amorphous precursors to minerals have been observed in laboratory materials and in nature, including across diverse phyla. These metastable phases allow for the incorporation of cations at higher concentrations than classical crystallization pathways, thus, their chemistry and behavior have implications in an array of disciplines. Currently, little is known about the isotopic composition of the anion

Successful application of diffusion chronometry is based on detailed knowledge of diffusion parameters obtained from laboratory experiments, which also need to be upscaled to be applied to natural samples. While generally applicable, several examples of disagreement with other dating techniques and discrepancies with geological observations highlight the importance of validating diffusion parameters

Alkali-suite rocks constitute one of three major suites of lunar crustal rocks. As such, constraining their formation timescales and petrogenesis is important for understanding the earliest magmatic history of the Moon. However, the magmatic history of alkali-suite rocks is partly obscured by superimposed effects of major basin-forming impact events on the lunar nearside. Consequently, unambiguous

The volatile concentrations of the martian mantle and martian magmas remain important questions due to their role in petrogenesis and planetary habitability. The sulfur and chlorine concentrations, and their spatial distribution, in clinopyroxenes from nakhlites MIL 03346, Nakhla, and NWA 998 were measured to provide insight into these volatiles in the parental melts and source regions of nakhlites

Previous work on Cr isotope composition of the lithospheric mantle focused on shallow spinel-facies peridotites and invoked the effects of partial melting and metasomatism. However, little is known on the Cr isotope composition and behavior in the deeper and more voluminous garnet-facies mantle, notably during generation and passage of magmas and fluids. Here, we present Cr isotope data for 26 garnet

The uranium (U) isotope ratio (238U/235U, reported as δ238U) in marine carbonates is an important proxy for reconstructing changes in past oceanic redox conditions, based on the essential assumption that U in carbonates originates from dissolved U(VI) in seawater. However, diagenetic processes may induce the addition of isotopically heavy U(IV) into the carbonates, complicating the application of the

Chemical weathering is one of the most important processes on the Earth’s surface, and lithium isotopes have been used as a promising tracer of silicate weathering, as the secondary clay minerals precipitated during silicate weathering are thought to preferentially incorporate the lighter 6Li isotope. However, to utilize lithium isotopes as a geochemical tracer, it is essential to quantitatively understand

The growth and morphology of stromatolites have been previously linked to diverse microbial activities. However, the role of microbial metabolisms on carbonate formation during stromatolite growth remains controversial. Magnesium isotopes have been proposed to serve as a tracer of microbial carbonate formation, implying a potential biological isotope fractionation. To further elucidate whether Mg isotope

Vanadium (V) is a redox-sensitive trace metal. Interconversion between different vanadium species (e.g., VIII, VIV, VV) occurs rapidly in association with changes in redox conditions in natural environments. Different vanadium species exhibit variable geochemical behavior that impacts if and how they are sequestered into sediments, which makes vanadium a useful proxy for ancient ocean redox conditions

Apollo 15 quartz monzodiorites (QMDs) are reported to contain some of the most deuterium-depleted apatite found in lunar samples. In this study, apatite from six Apollo 15 QMDs, including three samples from 15405 not previously investigated, were analyzed for their H and Cl isotopes. Apatite in 15405 are extremely 2H (or D)-poor, with δD values ranging from – 658 ± 53 to − 378 ± 113 ‰, comparable to

Gabbroic and microgabbroic shergottites are intrusive igneous rocks on Mars and exhibit a wide variety of mineralogical and geochemical properties. However, their source reservoirs, magmatic processes and the link to other shergottite subtypes are not well constrained. Northwest Africa (NWA) 13581 is a newly found permafic olivine gabbro, representing a cumulate member in the shergottite group. This

Ediacaran (∼635–539 Ma) carbonate rocks record the largest negative carbonate-carbon isotope excursion in Earth history, termed the Shuram Excursion (SE). This event has been attributed to anaerobic oxidation of dissolved organic carbon as a result of enhanced weathering inputs of sulfate to the ocean during the amalgamation of Gondwana. However, the effect of carbon–sulfur cycle interplay on the net

Coupled reaction of Fe(II) oxidation and nitrate reduction plays an important role in biogeochemical cycling of Fe and N, but biologically redox-inert clay minerals are seldom considered in this process. Herein, we report significant effects of ethylenediaminetetraacetic acid (EDTA) and oxalate on microbial oxidation of structural Fe(II) in illite and montmorillonite when coupled with reduction of

Redox-driven copper (Cu) isotope fractionation has been widely observed in low-temperature weathering and hydrothermal processes. However, how Cu isotopes may fractionate during magmatic processes remain unknown. To address this issue, we studied MORB samples from the East Pacific Rise (EPR) at 10°30′N to explore the Cu isotope behavior during magma differentiation. These samples are globally ideal

Various interference reactions producing unwanted Ar isotopes from K, Ca, Cl and Ar require correction to satisfy the 40Ar/39Ar age equation. Using GEANT4, we design and build a model Cadmium Lined In Core Irradiation Tube (CLICIT) irradiation facility, as used in the Oregon State TRIGA Reactor (OSTR). We illustrate the complexity of the irradiation of geologic samples within this framework and determine

Thallium (Tl) isotopes are used to reconstruct changes in global ocean oxygenation by tracking changes in past sedimentary manganese (Mn) oxide burial. This utility is born out of the large positive Tl isotope fractionation associated with sorption onto Mn oxides. While it is understood that interactions between Tl and Mn oxides are mineral-specific, the associated effects on Tl isotope fractionation