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

Local policies for reducing the ecological impact of households: the case study of a suburban area in France

Abstract Since Rio, governments have increased measures to promote sustainable household consumption, but this has induced limited changes in consumers' daily practices. This article argues that one of the reasons behind the poor efficiency of these policies is the low level of consideration granted to local decision-making. The article discusses the results of a study which aims at better ascertaining the practices and representations of local government leaders in promoting sustainable development in households. We shall analyse the motivations, obstacles, interaction of players, communication and action plans associated with promoting sustainable development, in which individual will and effort are the keywords. The results obtained show how important it is to introduce better management systems for information and resource exchange between the different institutions involved. The study was carried out in a suburban area of south-west France counting 71 small towns and villages, characteristic of the spatial dynamics triggered by the global phenomenon of urbanisation

New Integrated High-Resolution Dinoflagellate Cyst Stratigraphy and Litho- and Chemostratigraphy from the Paris and Dieppe–Hampshire Basins for the “Sparnacian”

The Paris Basin represents an historical cradle of Palaeogene stratigraphy, where during the nineteenth century the Palaeocene Series and the “Sparnacian Stage” were established. As highlighted by Aubry et al. (2005), whereas the chronostratigraphic connotation of the “Sparnacian Stage” has been controversial since its definition, modern studies of the late Palaeocene–early Eocene interval have revealed that the so-called “Sparnacian” deposits encompass a remarkable and short (~170 kyr) episode of the Cenozoic, the Palaeocene–Eocene Thermal Maximum (PETM, ~55.8–55.6 Ma). Dinoflagellate assemblages from the “Sparnacian” of the Dieppe–Hampshire and Paris basins do not contain the key species Apectodinium augustum, whereas it is present in the northern Belgian Basin Tienen Formation and is coeval there with the CIE and the Apectodinium acme interval. However, our calibration of the Apectodinium acme to the CIE in the Dieppe–Hampshire and Paris basins suggests its attribution to the A. augustum zone. The absence of species A. augustum in the Anglo–Paris Basin may be explained by its restriction to more offshore conditions