Chemical weathering of a granitic watershed: coupling Lithium isotopes and reactive transport modeling, preliminary results.

International audienceIn the present study, we report lithium concentrations and Li isotopic compositions for different samples within a granitic watershed (Margeride, France). We investigate unweathered bedrock and samples displaying different stages of weathering in order to characterize Li isotopic fractionation. This was achieved by coupling lithium isotope geochemistry and reactive transport modeling during granite weathering at the scale of this watershed. The following manuscript reports methodology and the preliminary data

Strontium isotope geochemistry of alluvial groundwater: a tracer for groundwater resources characterisation

International audienceThis study presents strontium isotope and major ion data of shallow groundwater and river water from the Ile du Chambon catchment, located on the Allier river in the Massif Central (France). There are large variations in the major-element contents in the surface- and groundwater. Plotting of Na vs. Cl contents and Ca, Mg, NO3, K, SO4, HCO3, Sr concentrations reflect water–rock interaction (carbonate dissolution for Ca, Mg, HCO3 and Sr because the bedrock contains marly limestones), agricultural input (farming and fertilising) and sewage effluents (for NO3, K, SO4), although some water samples are unpolluted. Sr contents and isotope ratios (87Sr/86Sr vary from 0.70892 to 0.71180 along the hydrological cycle) in the groundwater agree with previous work on groundwater in alluvial aquifers in the Loire catchment. The data plot along three directions in a 87Sr/86Sr v. 1/Sr diagram as a result of mixing, involving at least three geochemical signatures–Allier river water, and two distinct signatures that might be related to different water-rock interactions in the catchment. Mixing proportions are calculated and discussed. The alluvial aquifer of the Ile du Chambon catchment is considered, within the Sr isotope systematic, in a larger scheme that includes several alluvial aquifers of the Loire Allier catchment. Keywords: : Loire river, major and trace elements, Sr isotopic ratio, alluvial aquifer, hydrolog

Interaction eau-roche-CO2 en contexte de fuite contrôlée de CO2: apport du monitoring géochimique et isotopique lors d'un cas réel d'injection de CO2

Cette étude montre, dans un cas réel d'injection de CO2, comment une approche multi- isotopique (B, Li, S, O, Sr) combinée aux données chimiques permet (i) de tracer indirectement la réactivité et présence du CO2, (ii) de contraindre et comprendre précisément les interactions eau-roche-CO2 et les réponses isotopiques. L'originalité de ce travail consiste à utiliser des outils isotopiques développés dans les géosciences pour les appliquer à ce contexte particulier. L'idée majeure est d'utiliser ces outils comme traceurs des interactions eau-roche-CO2 afin de détecter toute anomalie de fuites de CO2 non décelables par les autres moyens de monitoring existant

Delta97/95Mo in molybdenites from the Azegour skarn (Morocco)

International audienceMolybdenum (Mo) isotopes are frequently used to investigate ocean and lake (paleo-)redox conditions. In the frame of mineral ressources, only few studies have been performed regarding Mo-Re-Os isotopes. The aim of this study is to understand the source, processes and mobility of metals concentrations using Mo isotopes on molybdenites in different ore deposits. The present study focuses on the Azegour skarn (Morocco). Located in the High-Atlas, the Azegour site is one of the rare Mo-W-Cu exploited skarns (three historic mines). It is formed by a granitic intrusion (271±3Ma) in cambrian volcano-sedimentary serie composed by schists, volcanic complex (andesites, pyroclastites) and carbonate formations (calcareous and dolomites). The skarn takes place in the carbonate formations where pyroxenites and grenatites occured. The grenatites being the Mo-bearing minerals in the form of molybdenites. Molybdenites sampling has been performed in the main mine (Azegour) and in the Tizgui mine (1km north of the Azegour mine). The Mo isotopic composition has been determined on molybdenites using a MC-ICP-MS Neptune after aquaregia dissolution and adjustment to [Mo] = 1µg.g-1. The δ97/95Mo ratios have been normalized to NBS3134 and a reproducibility of 0.07‰ (2σ) is reached. Presently, we have analysed 12 molybdenites from Azegour and 2 from Tizgui and 14 others are in progress. Regarding the first 14 samples, the δ97/95MoNBS ratios vary between -0.40 and 0.32‰ for Azegour and between 0.08 and 0.30‰ for Tizgui. It is worth noting that variations can occur either at the whole site (difference of about 0.72‰) but also at the cm scale in the same sample (here the largest observed difference is up to 0.40‰). Regarding the Azegour skarn, there is no direct relationship for explaining the Mo fractionation in molydbenites between the facies or the two sites of sampling. Different processes will be discussed to explain the observed variability (redox conditions prevaling during the molydbenites deposits, late metamophism phase...). Further investigations using Pb and S isotopic compositions will help deciphering the oxidation state and the origin of molybdenites regarding the possible different fluids

Boron Isotope Characterization to Design a Frame of Hydrogeological Functioning of a Wetland System (Massif Central, France)

AbstractMulti-isotopic approaches (Li, Sr, O, H), combined with hydrological tools, have been already appliedfor tracing the water and dissolved-element fluxes in a peatland in Central France. Here, we applied B isotopes. The δ11B ratios increase from river draining basalts (∼ 0‰) up to springs bordering the peatland (>+25‰). Peatland groundwaters have intermediate δ11B: 7.8 to 19.4‰. This range is accompanied by an increase in the Ca contents between the river draining basalts and water in the peatland. In aδ11B vs.Ca/B diagram, the role of water rock interaction and present day fertilizer inputs is evidenced, as for Sr isotopes

Maximizing cash flows in integrated resorts: An exploratory study of the highest and best use of available space

Through the analysis of the available literature, this exploratory study focuses on the concepts of direct and indirect contribution of amenities to the financial results of Integrated Resorts. In addition, the paper reviews the retail definition of highest and best use and evaluates its possible applications to the hospitality industry. Even if limited in number, studies in the field show that, with the appropriate statistical models, it is possible to estimate the indirect financial contribution of specific amenities to the profitability of Integrated Resorts. Moreover, an unprofitable amenity can justify its presence in an Integrated Resort only by indirectly contributing to the overall profitability of the company. Therefore, this study questions the general assumption, which is not based on empirical evidence, that including certain services in an Integrated Resort indirectly and positively impacts the overall financial performance of a company. Finally, this paper calls for future research on the topic for possible application to executives, developers, investors and customers in the hospitality industry as well as other service industries, including the retail sector

La Loire, usine à carbonates

Les matières en suspension estivales du cours moyen de la Loire ont une composition chimique et minéralogique très particulière : elles sont plus riches en silice, du fait de la présence de diatomées, et plus riches en calcium lié à la présence de cristaux de calcite endogénique, que dans le cours amont. En effet, dans ce tronçon ligérien, les blooms phytoplanctoniques, nombreux et denses, perturbent l'équilibre des carbonates dissous. La calcite peut alors se former directement dans les eaux de la Loire, phénomène qui est, à ce jour, peu décrit dans les fleuves des zones tempérées

Lithium isotopes in low and high temperature hydrosystems

International audienceAssessing the origin and behaviour of lithium and the distribution of Li isotopes in hydro-systems is of major importance in order to increase our knowledge of the lithium cycling at the Earth's surface. Lithium is a fluid-mobile element and due to the large relative mass difference between its two stable isotopes, it is subject to significant low and high temperature mass fractionation which provides key information on the nature of water/rock interaction processes. The main objective of the present work is to constrain the behaviour of Li and its isotopes by focusing on three different hydrosystems: rainwaters, river waters and deep geothermal waters

Evidence of hydrological control of Sr behavior in stream water (Strengbach catchment, Vosges mountains, France)

Strontium and particularly 87Sr/86Sr ratios in stream water have often been used to calculate weathering rates in catchments. Nevertheless, in the literature, discharge variation effects on the geochemical behavior of Sr are often omitted or considered as negligible. A regular survey of both Sr concentrations and Sr isotope ratios of the Strengbach stream water draining a granite (Vosges mountains, France) has been performed during one year. The results indicate that during low water flow periods, waters contain lower Sr concentrations and less radiogenic Sr isotope ratios (Sr=11.6 ppb and 87Sr/86Sr=0.7246 as an average, respectively) than during high water flow periods (Sr= 13 ppb and 87Sr/86Sr=0.7252 as an average, respectively). This is contrary to expected dilution processes by meteoric waters which have comparatively lower Sr isotopic ratios and lower Sr concentrations. Furthermore, 87Sr/86Sr ratios in stream water behave in 3 different ways depending on moisture and on hydrological conditions prevailing in the catchment. During low water flow periods (discharge < 9 l/s), a positive linear relationship exists between Sr isotope ratio and discharge, indicating the influence of radiogenic waters draining the saturated area during storm events. During high water flow conditions, rising discharges are characterized by significantly less radiogenic waters than the recession stages of discharge. This suggests a large contribution of radiogenic waters draining the deep layers of the hillslopes during the recession stages, particularly those from the more radiogenic north-facing slopes. These results allow one to confirm the negligible instantaneous incidence of rainwater on stream water chemistry during flood events, as well as the existence in the catchment of distinct contributive areas and reservoirs. The influence of these areas or reservoirs on the fluctuations of Sr concentrations and on Sr isotopic variations in stream water depends on both moisture and hydrological conditions. Hence, on a same bedrock type, 87Sr/86Sr ratios in surface waters can be related to flow rate. Consequently, discharge variations must be considered as a pre-requisite when using Sr isotopes for calculating weathering rates in catchments, particularly to define the range of variations of the end-members

Taxonomic Shifts in <em>Philornis</em> Larval Behaviour and Rapid Changes in <em>Philornis downsi</em> Dodge & Aitken (Diptera: Muscidae): An Invasive Avian Parasite on the Galápagos Islands

The parasitic larvae of Philornis downsi Dodge & Aitken (Diptera: Muscidae) were first discovered in Darwin’s finch nests on the Galápagos Islands in 1997. Larvae of P. downsi consume the blood and tissue of developing birds, causing high in-nest mortality in their Galápagos hosts. The fly has been spreading across the archipelago and is considered the biggest threat to the survival of Galápagos land birds. Here, we review (1) Philornis systematics and taxonomy, (2) discuss shifts in feeding habits across Philornis species comparing basal to more recently evolved groups, (3) report on differences in the ontogeny of wild and captive P. downsi larvae, (4) describe what is known about adult P. downsi behaviour, and (5) discuss changes in P. downsi behaviour since its discovery on the Galápagos Islands. From 1997 to 2010, P. downsi larvae have been rarely detected in Darwin’s finch nests with eggs. Since 2012, P. downsi larvae have regularly been found in the nests of incubating Darwin’s finches. Exploring P. downsi ontogeny and behaviour in the larger context of taxonomic relationships provides clues about the breadth of behavioural flexibility that may facilitate successful colonisation