Analysis of individual fluid inclusions using synchrotron X-ray fluorescence microprobe: progress toward calibration for trace elements   总被引：1，自引：0，他引：1  

Bénédicte Ménez  Pascal PhilippotMichelle Bonnin-Mosbah  Alexandre SimionoviciFrançois Gibert 《Geochimica et cosmochimica acta》2002,66(4):561-576

A critical problem for conducting quantitative analysis of individual fluid inclusions using Synchrotron X-Ray Fluorescence (SXRF) technique relates to the standardization and the calibration of the X-ray spectra. In this study, different approaches have been tested for calibration purposes: (a) the use of chlorine when Cl content can be estimated either from melting point depressions of undersaturated fluid inclusions or from saturation limits for halite-bearing fluid inclusions, (b) the use of calcium from synthetic fluid inclusions of known CaCl₂ content as an external standard. SXRF analysis was performed on individual fluid inclusions from the Chivor and Guali emerald deposits, Columbia. These well-known samples contain a single fluid inclusion population for which detailed crush-leach analyses are available, thus providing a relevant compositional reference frame. Concentration estimates were also compared to Particle Induced X-ray Emission (PIXE) analysis carried out independently on the same fluid inclusions.Results of the calibration tests indicate that major (Cl, K, Ca, Fe, Mn) and trace element (Cu, Zn, As, Br, Rb, Sr, Ba, Pb) concentration estimates can be performed without precise knowledge of the analytical volume and the inclusion’s 3D geometry. Although the standard deviation of the SXRF results can be relatively high depending on the calibration mode used, mean concentration estimates for most elements are in good agreement with PIXE and crush-leach analysis. Elemental distributions within single fluid inclusions were also established. Associated correlation diagrams argue for the homogeneous distribution of most elements in the fluid inclusion. In contrast, Br shows a bimodal distribution interpreted to reflect a significant enrichment of the vapor portion of the inclusion fluid.  相似文献   

Power spectrum normalization and the non-Gaussian halo model     

Adam Amara  Alexandre Refregier 《Monthly notices of the Royal Astronomical Society》2004,351(1):375-383

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A first modeling of dynamic and static crustal strain field from near-field dilatation measurements: example of the 2013 $$M_w$$ 6.2 Ruisui earthquake,Taiwan     

Alexandre Canitano  Ya-Ju Hsu  Hsin-Ming Lee  Alan T. Linde  Selwyn Sacks 《Journal of Geodesy》2017,91(1):1-8

We analyze the high-resolution dilatation data for the October 2013 \(M_w\) 6.2 Ruisui, Taiwan, earthquake, which occurred at a distance of 15–20 km away from a Sacks–Evertson dilatometer network. Based on well-constrained source parameters (\(\hbox {strike}=217^\circ \), \(\hbox {dip}=48^\circ \), \(\hbox {rake}=49^\circ \)), we propose a simple rupture model that explains the permanent static deformation and the dynamic vibrations at short period (\(\sim \)3.5–4.5 s) for most of the four sites with less than 20 % of discrepancies. This study represents a first attempt of modeling simultaneously the dynamic and static crustal strain using dilatation data. The results illustrate the potential for strain recordings of high-frequency seismic waves in the near-field of an earthquake to add constraints on the properties of seismic sources.  相似文献   

Erratum to: Combined effect of pulse density and grid cell size on predicting and mapping aboveground carbon in fast-growing Eucalyptus forest plantation using airborne LiDAR data     

Carlos Alberto Silva  Andrew Thomas Hudak  Carine Klauberg  Lee Alexandre Vierling  Carlos Gonzalez-Benecke  Samuel de Padua Chaves Carvalho  Luiz Carlos Estraviz Rodriguez  Adrián Cardil 《Carbon balance and management》2017,12(1):14

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Using a WebMapping Platform to Engage Volunteers to Collect Data on Invasive Plants Distribution          下载免费PDF全文

Hélia Marchante  Maria Cristina Morais  Alexandre Gamela  Elizabete Marchante 《Transactions in GIS》2017,21(2):238-252

WebMapping and citizen science are increasing their importance as tools both in science communication and in gathering abundant data. Nevertheless, gathering good and plentiful data from citizens when the scientific theme is unknown to them is a demanding challenge. Invasoras.pt is a science communication endeavor that targets the general public and one of its core elements is a WebMapping platform that intends to engage volunteers to geolocate invasive plants in Portugal. Besides gathering data for scientific research and to support management, the platform raises awareness about invasive plants. The platform has been available since March 2013 and receives data from a smartphone application and a Web application. Validated sightings are shown on an online map. All data is available through a Google Fusion Table and GBIF database (open data logic). Several strategies (interactive contents, printed materials, workshops and social media) were used to overcome the challenges of engaging contributors and making them better skilled to contribute with good data. After two years of steady growth in members (ca. 600) and sightings (>5400) the results are better than expected particularly amongst a population not familiarized with either citizen science or invasive plants. The outcomes of the platform and the efficacy of each strategy are analyzed and the accuracy and usefulness of the data are discussed.  相似文献   

Analysis of snow-vegetation interactions in the low Arctic-Subarctic transition zone (northeastern Canada)     

Bruno-Charles Busseau  Alain Royer  Alexandre Roy  Alexandre Langlois  Florent Domine 《自然地理学》2017,38(2):159-175

Abstract

Recent studies have shown that northern vegetation has been growing in relation to a warming climate over the last four decades, especially across the transition zone between tundra and taiga. Shrub growth affects snow properties and the surface energy budget, which must be better studied to quantify shrub-snow-climate feedbacks. The objective of this research is to improve the characterization of the impact of shrubs on snow evolution, from its accumulation to its melt, using in-situ and satellite measurements. The research is presented for the Umiujaq site, Nunavik, representative of the low Arctic–Subarctic transition zone. Snow depth, measured along numerous transects spanning different land cover types is found to increase by a factor 2.5–3 between tundra and forest, while snow density decreases. This illustrates the trapping effect of vegetation well. Complementary, continuous snow depth measurements using weather stations from two sites (tundra with low shrubs and a small clearing with shrubs within the forest) show different site-dependent behaviors. Spatial analysis from high-resolution Pleiades images combined with Landsat (Normalized Difference Snow Index) and MODIS (Fractional Snow Cover) images suggest a slight delay in melt over open and dense forest areas compared to tundra and dense high shrubs.  相似文献   

Uncertainties in the SNOWPACK multilayer snow model for a Canadian avalanche context: sensitivity to climatic forcing data     

Kevin Côté  Jean-Benoît Madore  Alexandre Langlois 《自然地理学》2017,38(2):124-142

Abstract

As interest in outdoor activities in remote areas is increasing, there is a strong need for improved avalanche forecasting at the regional scale. Due to important logistical and safety matters, avalanche terrain measurements (avalanche observations, snowpack profiles, and stability tests) are not always possible for practitioners/forecasters. An interesting alternative would be to analyze the snowpack without these challenges by using snow model outputs. The SNOWPACK model is currently used operationally for avalanche forecasting and research in the Swiss Alps. Thus, this paper presents a summary of analyses that have been conducted to assess the potential of using the SNOWPACK model driven with both in-situ and forecasted meteorological data in three different Canadian climate and geomorphological contexts. A comparison of meteorological data from in-situ and predicted datasets for two winters shows that the GEMLAM weather model is the most accurate for the three climatic contexts of this project, but also showed a bias proportional to precipitation intensity/rate. Snow simulations forced with GEMLAM are the closest to field measurements. Finally, predictions of persistent weak layers have been validated using the InfoEx platform from Avalanche Canada. Crust and surface hoar formation dates agree with the information reported in InfoEx.  相似文献   

Succession of Permian and Mesozoic metasomatic events in the eastern Pyrenees with emphasis on the Trimouns talc–chlorite deposit     

Alexandre Boutin  Michel de Saint Blanquat  Marc Poujol  Philippe Boulvais  Philippe de Parseval  Caroline Rouleau  Jean-François Robert 《International Journal of Earth Sciences》2016,105(3):747-770

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Nitrogen uptake in light versus darkness of the seagrass Zostera noltei: integration with carbon metabolism          下载免费PDF全文

Ana Alexandre  João Silva  Rui Santos 《Marine Ecology》2016,37(5):1050-1056

We conducted a study that shows that light and dark conditions do not affect the uptake rates of ammonium and nitrate by the seagrass Zostera noltei. This is an important advantage over some seaweed species in which these rates are severely reduced at night. In the light, the ammonium uptake rates were initially higher (15 and 20 μmol·g^?1·h^?1) and stabilized at a rate of 5 μmol·g^?1·h^?1 after 1 h, whereas in the dark the rates remained constant at a rate of 10 μmol·g^?1·h^?1 over the first 180 min of incubation. The rates of nitrate uptake in the light were high within the first 120 min of incubation (7.2–11.1 μmol·g^?1·h^?1) and decreased afterwards to lower values (0.8–3.9 μmol·g^?1·h^?1), whereas in the dark the rates fluctuated around 0.0–11.1 μmol·g^?1·h^?1 throughout the whole incubation time (7 h). The soluble sugar content of Z. noltei leaves increased significantly with both ammonium and nitrate incubations in the light, indicating the metabolic outcome of photosynthesis. In the dark, there was no significant variation in either the soluble sugar or in the starch content of leaves, rhizomes or roots in either the ammonium or nitrate incubations. However, the total starch content of plants decreased at night whereas the total soluble sugars increased, suggesting a process of starch catabolism to generate energy with the consequent production of smaller monosaccharide products. The starch content of rhizomes decreased significantly during the light incubations with nitrate but not with ammonium. These results suggest that carbohydrate mobilization is necessary for Z. noltei to account for extra energetic costs needed for the uptake and assimilation of nitrate. Furthermore, our results suggest that nitrate uptake, at least during the day, requires the mobilization of starch whereas the uptake of ammonium does not.  相似文献   

New discoveries of vertebrate remains from the Triassic of Riba de Santiuste,Guadalajara (Spain)     

Mélani Berrocal-Casero  Julia Audije-Gil  Rui Alexandre Castanhinha  Juan Alberto Pérez-Valera  Vanda Faria dos Santos  Manuel Segura 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(4):526-541

The palaeontological sites of Riba de Santiuste and Sienes (Riba de Santiuste area) are located in the province of Guadalajara, Spain. They include a stratigraphic interval in Muschelkalk facies belonging to the “Cuesta del Castillo Sandstones” Formation and “Royuela Dolostones, Marls and Mudstones” Formation. These sites include numerous fossil plants, direct vertebrate remains, and vertebrate swim traces. The vertebrate remains correspond to a multitude of anatomical elements of Sauropterygia (Nothosauroidea, Placodontia) and possible Archosauria (Rauisuchia) remains. The fossil material attributed to nothosaurs includes teeth, coracoids, a thoracic vertebra, some isolated vertebral centra, humerus, rib fragments, and some dorsal and caudal vertebrae. The remains attributed to placodonts correspond to fragments of skull, quadrate, teeth and osteoderms. Other undetermined sauropterygian remains, such as ulnas, fragments of long bones, fragments of ribs, and articular facets of ribs have been also recovered. Additionally, a fragment of mandible and an intervertebral disk of indeterminate reptiles whose size could be compatible with archosaurs are also described. These bones are exceptionally well-preserved because the fossilization processes have preserved the microstructure of the tissues. The sites also show vertebrate traces, with parallel scratch impressions interpreted as swim traces. The relative stratigraphic position and the palaeontological content of these sites suggest a Ladinian age (Middle Triassic). The interpretation of the sedimentary facies here described also suggests that the sites could correspond to detrital-carbonate mixed deposits of coastal intertidal to supratidal environments.  相似文献