Mid-Cretaceous marine Os isotope evidence for heterogeneous cause of oceanic anoxic events

During the mid-Cretaceous, the Earth experienced several environmental perturbations, including an extremely warm climate and Oceanic Anoxic Events (OAEs). Submarine volcanic episodes associated with formation of large igneous provinces (LIPs) may have triggered these perturbations. The osmium isotopic ratio (187Os/188Os) is a suitable proxy for tracing hydrothermal activity associated with the LIPs formation, but 187Os/188Os data from the mid-Cretaceous are limited to short time intervals. Here we provide a continuous high-resolution marine 187Os/188Os record covering all mid-Cretaceous OAEs. Several OAEs (OAE1a, Wezel and Fallot events, and OAE2) correspond to unradiogenic 187Os/188Os shifts, suggesting that they were triggered by massive submarine volcanic episodes. However, minor OAEs (OAE1c and OAE1d), which do not show pronounced unradiogenic 187Os/188Os shifts, were likely caused by enhanced monsoonal activity. Because the subaerial LIPs volcanic episodes and Circum-Pacific volcanism correspond to the highest temperature and pCO2 during the mid-Cretaceous, they may have caused the hot mid-Cretaceous climate.

Size and isotopic ratio measurements of individual nanoparticles by a continuous ion-monitoring method using Faraday detectors equipped on a multiple collector-ICP-mass spectrometer

We investigated the analytical capability of high-gain Faraday detectors equipped on a multiple collector-ICP-mass spectrometer (MFC-ICP-MS) in performing both size and isotopic ratio measurements on individual silver nanoparticles (Ag NPs)....

Spatial distribution of HOCN around Sagittarius B2

HOCN and HNCO abundance ratio in molecular gas can tell us the information of their formation mechanism. We performed high-sensitivity mapping observations of HOCN, HNCO, and HNC18O lines around Sagittarius B2 (Sgr B2) with IRAM 30m telescope at 3-mm wavelength. HNCO 404-303 and HOCN 404-303 are used to obtain the abundance ratio of HNCO to HOCN. The ratio of HNCO 404-303 to HNC18O 404-303 is used to calculate the optical depth of HNCO 04-303. The abundance ratio of HOCN and HNCO is observed to range from 0.4% to 0.7% toward most positions, which agrees well with the gas-grain model. However, the relative abundance of HOCN is observed to be enhanced toward the direction of Sgr B2 (S), with HOCN to HNCO abundance ratio of ∼ 0.9%. The reason for that still needs further investigation. Based on the intensity ratio of HNCO and HNC18O lines, we updated the isotopic ratio of 16O/18O to be 296 ± 54 in Sgr B2.

Measurements Isotopic Ratios Signature and Level Concentration of Pb and Sr from Several Romanian Wines

Authenticity, certification, and especially the origin of food has become an increasing priority among consumers and producers, in the case of wines, this is very important especially if commercial values are associated with the region of production. In the last decades, isotopic ratios of geological interest, such as Pb, and Sr, have gained interest in the tracking regional provenance of foods and especially of wine. The correlation of the Pb and Sr isotope ratios between soil and plant makes it an interesting tool for tracing the provenance of agricultural products such as grapes and wine. The purpose of this research was to assessment the Pb and Sr isotopic ratio to highlight geographical markers with a high degree of credibility in several Romanian wine-growing areas. The values of the 206Pb/207Pb, for the vine from Dealu Bujorului and Valea Călugărească vineyard show traces of lead atmospheric pollution, in Nicorești, Panciu, and Ștefăneți-Argeș vineyard the values of the isotopic ratio show traces of fly ashes, coals, or natural Pb and Greaca vineyard show traces of petrol, gasoline, combustion. Due to Pb, and Sr a separation on the vineyards and wine-growing centers, and also a separation of the wine samples was possible.

Quantitative Analysis of Nitrogen by Atom Probe Tomography Using Stoichiometric γ′-Fe4N Consisting of 15N Isotope

The nitrogen deficiency in steels measured by atom probe tomography (APT) is considered to arise from the obscurement of singly charged dimer nitrogen ions (N2+) by the iron-dominant peak (56Fe2+) at 28 Da. To verify this by quantifying the amount of N2+ ions, γ′-Fe4N consisting of the 15N isotope was prepared on iron substrates by plasma nitriding using a nitrogen isotopic gas (15N2). Although considerable amounts of 15N2+ were observed at 30 Da without overlap with any iron peak, the observed nitrogen concentrations of γ′-Fe4N were clearly lower than the stoichiometric composition (19–20 at%), using both pulsed voltage and pulsed laser atom probes. The origin of the missing nitrogen, excluding nitrogen obscured by other ion species, was predicted to be the occurrence of neutral nitrogen or nitrogen gas molecules in field evaporation. The generation rate of iron nitride ions (FeN2+) for 15N was significantly lower than that for 14N in γ′-Fe4N, which affected the amount of the missing nitrogen. The isotope effect suggests that the isotopic ratio cannot always be determined from only one ion species among the multiple species observed in the APT analysis. We discuss the mechanism of the isotope effect in FeN2+ formation by field evaporation.

Isotope geochemistry of gallium in hydrothermal systems

<p>Little is known about the isotope geochemistry of gallium in natural systems (Groot, 2009), with most information being limited to very early studies of gallium isotopes in extra-terrestrial samples (Aston, 1935; De Laeter, 1972; Inghram et al., 1948; Machlan et al., 1986). This study is designed as a reconnaissance for gallium isotope geochemistry in hydrothermal systems of New Zealand. Gallium has two stable isotopes, ⁶⁹Ga and ⁷¹Ga, and only one oxidation state, Ga³⁺, in aqueous media (Kloo et al., 2002). This means that fractionation of gallium isotopes should not be effected by redox reactions. Therefore the physical processes that occur during phase changes of hydrothermal fluids (i.e. flashing of fluids to vapour phase and residual liquid phase) and mineralisation of hydrothermal precipitates (i.e. precipitation and ligand exchange) can be followed by studying the isotopes of gallium. A gallium anomaly is known to be associated with some hydrothermal processes as shown by the unusual, elevated concentrations (e.g. 290 ppm in sulfide samples of Waiotapu; this study) in several of the active geothermal systems in New Zealand. The gallium isotope system has not yet been investigated since the revolution of high precision isotopic ratio measurements by Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) and so a new analytical methodology needed to be established. Any isotopic analysis of multi-isotope elements must satisfy a number of requirements in order for results to be both reliable and meaningful. Most importantly, the analysis must represent the true isotopic composition of the sample. Ion-exchange chromatography is generally utilised to purify samples for analysis by MC-ICPMS and exclude potential mass interfering elements but care must also be taken to recover as close to 100% of the element of interest as possible, as column chromatography can often result in fractionation of isotopes (Albarède and Beard, 2004). An ion exchange column chromatography methodology for the separation of gallium based on earlier work by Strelow and associates (Strelow, 1980a, b; Strelow and van der Walt, 1987; Strelow et al., 1974; van der Walt and Strelow, 1983) has been developed to ensure a quantitative and clean separation from the majority of elements commonly associated with hydrothermal precipitates and waters (i.e. As, Sb, Mo, Hg, W, Tl, Fe and other transition metals). A protocol to measure the isotopes of Ga was developed by the adaptation of methods used for other stable isotope systems using the Nu Plasma MC-ICPMS at the School of Geography, Environment and Earth Sciences, Victoria University of Wellington, NZ. Gallium isotopic ratios have been collected for a suite of samples representing the migration of hydrothermal fluids from deep fluids in geothermal reservoirs to the surface expression of hot spring waters and associated precipitates in hydrothermal systems. A range in δ⁷¹GaSRM994 values is observed in samples from Taupo Volcanic Zone geothermal fields from -5.49‰ to +2.65‰ in silica sinter, sulfide, mud and brine samples. Mineral samples from Tsumeb and Kipushi mines range from -11.92‰ to +2.58‰ δ⁷¹GaSRM994. Two rock standards, BHVO-2 and JR-2 were also analysed for gallium isotopes with δ⁷¹GaSRM994 values of -0.92‰ ±0.12‰ and -1.91‰ ±0.23‰ respectively.</p>

Isotope geochemistry of gallium in hydrothermal systems

<p>Little is known about the isotope geochemistry of gallium in natural systems (Groot, 2009), with most information being limited to very early studies of gallium isotopes in extra-terrestrial samples (Aston, 1935; De Laeter, 1972; Inghram et al., 1948; Machlan et al., 1986). This study is designed as a reconnaissance for gallium isotope geochemistry in hydrothermal systems of New Zealand. Gallium has two stable isotopes, ⁶⁹Ga and ⁷¹Ga, and only one oxidation state, Ga³⁺, in aqueous media (Kloo et al., 2002). This means that fractionation of gallium isotopes should not be effected by redox reactions. Therefore the physical processes that occur during phase changes of hydrothermal fluids (i.e. flashing of fluids to vapour phase and residual liquid phase) and mineralisation of hydrothermal precipitates (i.e. precipitation and ligand exchange) can be followed by studying the isotopes of gallium. A gallium anomaly is known to be associated with some hydrothermal processes as shown by the unusual, elevated concentrations (e.g. 290 ppm in sulfide samples of Waiotapu; this study) in several of the active geothermal systems in New Zealand. The gallium isotope system has not yet been investigated since the revolution of high precision isotopic ratio measurements by Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) and so a new analytical methodology needed to be established. Any isotopic analysis of multi-isotope elements must satisfy a number of requirements in order for results to be both reliable and meaningful. Most importantly, the analysis must represent the true isotopic composition of the sample. Ion-exchange chromatography is generally utilised to purify samples for analysis by MC-ICPMS and exclude potential mass interfering elements but care must also be taken to recover as close to 100% of the element of interest as possible, as column chromatography can often result in fractionation of isotopes (Albarède and Beard, 2004). An ion exchange column chromatography methodology for the separation of gallium based on earlier work by Strelow and associates (Strelow, 1980a, b; Strelow and van der Walt, 1987; Strelow et al., 1974; van der Walt and Strelow, 1983) has been developed to ensure a quantitative and clean separation from the majority of elements commonly associated with hydrothermal precipitates and waters (i.e. As, Sb, Mo, Hg, W, Tl, Fe and other transition metals). A protocol to measure the isotopes of Ga was developed by the adaptation of methods used for other stable isotope systems using the Nu Plasma MC-ICPMS at the School of Geography, Environment and Earth Sciences, Victoria University of Wellington, NZ. Gallium isotopic ratios have been collected for a suite of samples representing the migration of hydrothermal fluids from deep fluids in geothermal reservoirs to the surface expression of hot spring waters and associated precipitates in hydrothermal systems. A range in δ⁷¹GaSRM994 values is observed in samples from Taupo Volcanic Zone geothermal fields from -5.49‰ to +2.65‰ in silica sinter, sulfide, mud and brine samples. Mineral samples from Tsumeb and Kipushi mines range from -11.92‰ to +2.58‰ δ⁷¹GaSRM994. Two rock standards, BHVO-2 and JR-2 were also analysed for gallium isotopes with δ⁷¹GaSRM994 values of -0.92‰ ±0.12‰ and -1.91‰ ±0.23‰ respectively.</p>

Modeling of cosmic ray 22Ne-enrichment in compact star clusters

22Ne/20Ne isotopic ratio is found to be about 5 times higher in Galactic cosmic rays (GCRs) than in the solar wind. In this paper we develop the hypothesis that the 22Ne overabundance in CRs is generated in compact massive star clusters which contain populations of Wolf-Rayet stars. Winds of Wolf-Rayet stars are considered to have high content of 22Ne. We assume that particle acceleration occurs on the ensemble of strong shocks from the massive stars’ winds. We present a model of cosmic ray enrichment with 22Ne, adding isotopic yields from supernovae and taking into account the acceleration efficiency during the lifetime of the stars. The impact of the parameters (the initial mass function in the cluster, rotation velocity, black hole cut-off mass) is discussed. The energy balance for our model is calculated.