Sub‐Permil Interlaboratory Consistency for Solution‐Based Boron Isotope Analyses on Marine Carbonates     

Marcus Gutjahr  Louise Bordier  Eric Douville  Jesse Farmer  Gavin L. Foster  Ed C. Hathorne  Brbel Hnisch  Damien Lemarchand  Pascale Louvat  Malcolm McCulloch  Johanna Noireaux  Nicola Pallavicini  James W. B. Rae  Ilia Rodushkin  Philippe Roux  Joseph A. Stewart  Franois Thil  Chen‐Feng You 《Geostandards and Geoanalytical Research》2021,45(1):59-75

Boron isotopes in marine carbonates are increasingly used to reconstruct seawater pH and atmospheric pCO₂ through Earth’s history. While isotope ratio measurements from individual laboratories are often of high quality, it is important that records generated in different laboratories can equally be compared. Within this Boron Isotope Intercomparison Project (BIIP), we characterised the boron isotopic composition (commonly expressed in δ¹¹B) of two marine carbonates: Geological Survey of Japan carbonate reference materials JCp‐1 (coral Porites) and JCt‐1 (giant clam Tridacna gigas). Our study has three foci: (a) to assess the extent to which oxidative pre‐treatment, aimed at removing organic material from carbonate, can influence the resulting δ¹¹B; (b) to determine to what degree the chosen analytical approach may affect the resultant δ¹¹B; and (c) to provide well‐constrained consensus δ¹¹B values for JCp‐1 and JCt‐1. The resultant robust mean and associated robust standard deviation (s*) for un‐oxidised JCp‐1 is 24.36 ± 0.45‰ (2s*), compared with 24.25 ± 0.22‰ (2s*) for the same oxidised material. For un‐oxidised JCt‐1, respective compositions are 16.39 ± 0.60‰ (2s*; un‐oxidised) and 16.24 ± 0.38‰ (2s*; oxidised). The consistency between laboratories is generally better if carbonate powders were oxidatively cleaned prior to purification and measurement.  相似文献   

Analysis And Comparison Of Different Estimations Of Mars' Polar Motion     

Gauchez  Damien  Souchay  Jean 《Earth, Moon, and Planets》1999,84(1):33-51

We have summed up three recent modellings of Mars' polar motion (Hilton, 1992; Yoder and Standish, 1997; Zhang, 1998) from which we have studied in particular the Chandler wobble (CW) of the planet and expressions of its period T_CW. We add a fourth study (Kubo, 1991) which deals with the polar motion on the Earth, but whose the results can easily be applied to Mars. To conpare the different expressions of the period T_CW from the authors above, we have chosen common parameters of the planet coming from recent data and we have calculated values of the period corresponding to these parameters after having determined from analytical developments the moments of inertia of the core and of the mantle. We show how the different formula proposed by the authors lead to different values of T_CW and we study in particular the contribution of somc parameters such as the core radius, the mass of the core and the Love number of these values.  相似文献   

3D modelling of dreissenid mussel impacts on phytoplankton in a large lake supports the nearshore shunt hypothesis and the importance of wind-driven hydrodynamics     

Astrid N. Schwalb  Damien Bouffard  Leon Boegman  Luis Leon  Jennifer G. Winter  Lewis A. Molot  Ralph E. H. Smith 《Aquatic Sciences - Research Across Boundaries》2015,77(1):95-114

  相似文献   

Why do we build check dams in Alpine streams? An historical perspective from the French experience   总被引：1，自引：0，他引：1       下载免费PDF全文

Guillaume Piton  Simon Carladous  Alain Recking  Jean Marc Tacnet  Frédéric Liébault  Damien Kuss  Yann Quefféléan  Olivier Marco 《地球表面变化过程与地形》2017,42(1):91-108

  相似文献   

Comparison of Travel-Time and Amplitude Measurements for Deep-Focusing Time–Distance Helioseismology     

Majid Pourabdian  Damien Fournier  Laurent Gizon 《Solar physics》2018,293(4):66

The purpose of deep-focusing time–distance helioseismology is to construct seismic measurements that have a high sensitivity to the physical conditions at a desired target point in the solar interior. With this technique, pairs of points on the solar surface are chosen such that acoustic ray paths intersect at this target (focus) point. Considering acoustic waves in a homogeneous medium, we compare travel-time and amplitude measurements extracted from the deep-focusing cross-covariance functions. Using a single-scattering approximation, we find that the spatial sensitivity of deep-focusing travel times to sound-speed perturbations is zero at the target location and maximum in a surrounding shell. This is unlike the deep-focusing amplitude measurements, which have maximum sensitivity at the target point. We compare the signal-to-noise ratio for travel-time and amplitude measurements for different types of sound-speed perturbations, under the assumption that noise is solely due to the random excitation of the waves. We find that, for highly localized perturbations in sound speed, the signal-to-noise ratio is higher for amplitude measurements than for travel-time measurements. We conclude that amplitude measurements are a useful complement to travel-time measurements in time–distance helioseismology.  相似文献   

Ionospheric delay corrections for single-frequency GPS receivers over Europe using tomographic mapping   总被引：3，自引：2，他引：1  

Damien J. Allain  Cathryn N. Mitchell 《GPS Solutions》2009,13(2):141-151

The majority of navigation satellites receivers operate on a single frequency and experience a positioning error due to the ionospheric delay. This can be compensated for using a variety of approaches that are compared in this paper. The study focuses on the last solar maximum. A 4D tomographic imaging technique is used to map the ionospheric electron density over the European region during 2002 and 2003. The electron density maps are then used to calculate the excess propagation delay on the L1 frequency experienced by GPS receivers at selected locations across Europe. The excess delay is applied to correct the pseudo-range single frequency observations at each location and the improvements to the resulting positioning are calculated. The real-time tomographic technique is shown to give navigation solutions that are better than empirical modelling methods and approach the accuracy of the full dual-frequency solution. The improvements in positioning accuracy vary from day to day depending on ionospheric conditions but can be up to 25 m during mid-day during these solar maximum conditions at European mid-latitudes.

Damien J. AllainEmail:

  相似文献   

Peak Minerals: Theoretical Foundations and Practical Application     

Daniel May  Timothy Prior  Dana Cordell  Damien Giurco 《Natural Resources Research》2012,21(1):43-60

This article reviews the theoretical foundations for the concept of peak minerals; drawing on similarities and differences with peak oil as modelled using Hubbert style curves. Whilst several studies have applied peak modelling to selected minerals, discussion of the appropriateness of using Hubbert style curves in the minerals context remains largely unexplored. Our discussion focuses on a comparison between oil and minerals, on the key variables: rates of discovery, estimates of ultimately recoverable resources and demand and production trends. With respect to minerals, there are several obstacles which complicate the application of Hubbert style curves to the prediction of future mineral production, including the lack of accurate discovery data, the effect of uncertain reserve estimates, and varying ore quality and quantity. Another notable difference is that while oil is often combusted during use, minerals are used to make metals which are inherently recyclable. Notwithstanding, by using a range of estimates of resources and/or reserves, a period of time can be identified which indicates when a peak in minerals production may occur. This information may then be used to plan for a transition from using a potentially constrained resource, to using substitutes if available, or to reducing demand for that mineral in society.  相似文献   

Nickeliferous pyrite tracks pervasive hydrothermal alteration in Martian regolith breccia: A study in NWA 7533          下载免费PDF全文

Jean‐Pierre Lorand  Roger H. Hewins  Laurent Remusat  Brigitte Zanda  Sylvain Pont  Hugues Leroux  Maya Marinova  Damien Jacob  Munir Humayun  Alexander Nemchin  Marion Grange  Allen Kennedy  Christa Göpel 《Meteoritics & planetary science》2015,50(12):2099-2120

Martian regolith breccia NWA 7533 (and the seven paired samples) is unique among Martian meteorites in showing accessory pyrite (up to 1% by weight). Pyrite is a late mineral, crystallized after the final assembly of the breccia. It is present in all of the lithologies, i.e., the fine‐grained matrix (ICM), clast‐laden impact melt rocks (CLIMR), melt spherules, microbasalts, lithic clasts, and mineral clasts, all lacking magmatic sulfides due to degassing. Pyrite crystals show combinations of cubes, truncated cubes, and octahedra. Polycrystalline clusters can reach 200 μm in maximum dimensions. Regardless of their shape, pyrite crystals display evidence of very weak shock metamorphism such as planar features, fracture networks, and disruption into subgrains. The late fracture systems acted as preferential pathways for partial replacement of pyrite by iron oxyhydroxides interpreted as resulting from hot desert terrestrial alteration. The distribution and shape of pyrite crystals argue for growth at moderate to low growth rate from just‐saturated near neutral (6 < pH<10), H₂S‐HS‐rich fluids at minimum log fO₂ of >FMQ + 2 log units. It is inferred from the maximum Ni contents (4.5 wt%) that pyrite started crystallizing at 400–500 °C, during or shortly after a short‐duration, relatively low temperature, thermal event that lithified and sintered the regolith breccias, 1.4 Ga ago as deduced from disturbance in several isotope systematics.  相似文献   

Insights into estuarine benthic dissolved organic carbon (DOC) dynamics using δC-DOC values, phospholipid fatty acids and dissolved organic nutrient fluxes     

Damien Maher  Bradley D. Eyre 《Geochimica et cosmochimica acta》2011,75(7):1889-1902

Benthic dissolved organic carbon (DOC) flux rates and changes in DOC isotope ratios, along with nutrient fluxes, phospholipid fatty acids concentration and carbon isotope ratios were measured in productive estuarine sediments over a diel cycle to determine the mechanisms driving benthic-pelagic coupling of DOC. There was uptake of DOC during the dark and efflux during the light at all sites. DOC uptake rates were related to benthic respiration (dark O₂ uptake) and effluxes were coupled to the trophic status (ratio of production to respiration) of the sediments. Highest uptake and efflux rates were observed at two high nutrient concentration sites. The DOC:DON ratio of water column dissolved organic matter (DOM) decreased during the dark and increased during the light indicating preferential uptake and release of carbon rich dissolved organic matter. The calculated carbon isotope ratio of the DOC taken up by the benthos was significantly more depleted than the bulk water column DOC pool, suggesting preferential uptake of selected components of the water column DOC pool. Generally the isotope ratio of the DOC released during the light was more enriched than that taken up during the dark, which suggests that the benthos has the potential to significantly alter the estuarine DOC pool. Uptake and efflux were coupled to respiration and algal grazing/mineralization, therefore increased nutrient loading may shift the composition of the estuarine DOC pool through changes in the magnitude of benthic DOC fluxes. A combination of biological (diel shifts in DOC production and consumption) and abiotic processes (flocculation) appear to be driving the observed benthic DOC dynamics at the study sites. This study was the first to measure carbon isotopic changes in the water column DOC pool due to benthic processes, and shows that the benthos can alter the estuarine DOC pool through diel differences in DOC uptake and efflux.  相似文献   

CO2 geological storage: The environmental mineralogy perspective     

François Guyot  Damien Daval  Sébastien Dupraz  Isabelle Martinez  Bénédicte Ménez  Olivier Sissmann 《Comptes Rendus Geoscience》2011,343(2-3):246-259

Geological storage of carbon dioxide (CO₂) is one of the options envisaged for mitigating the environmental consequences of anthropogenic CO₂ increases in the atmosphere. The general principle is to capture carbon dioxide at the exhaust of power plants and then to inject the compressed fluid into deep geological formations. Before implementation over large scales, it is necessary to assess the efficiency of the process and its environmental consequences. The goal of this paper is to discuss some environmental mineralogy research perspectives raised by CO₂ geological storage.  相似文献