An extraterrestrial trigger for the Early Cretaceous massive volcanism? Evidence from the paleo-Tethys Ocean

The Early Cretaceous Greater Ontong Java Event in the Pacific Ocean may have covered ca. 1% of the Earth's surface with volcanism. It has puzzled scientists trying to explain its origin by several mechanisms possible on Earth, leading others to propose an extraterrestrial trigger to explain this event. A large oceanic extraterrestrial impact causing such voluminous volcanism may have traces of its distal ejecta in sedimentary rocks around the basin, including the paleo-Tethys Ocean which was then contiguous with the Pacific Ocean. The contemporaneous marine sequence at central Italy, containing the sedimentary expression of a global oceanic anoxic event (OAE1a), may have recorded such ocurrence as indicated by two stratigraphic intervals with 187Os/188Os indicative of meteoritic influence. Here we show, for the first time, that platinum group element abundances and inter-element ratios in this paleo-Tethyan marine sequence provide no evidence for an extraterrestrial trigger for the Early Cretaceous massive volcanism

Stress Processes: An Essential Ingredient in the Entrepreneurial Process

The entrepreneurial process is associated with high uncertainty. Uncertainty is also a major source of stress. Therefore, a core aim of entrepreneurs is to reduce uncertainty to an extent that allows the entrepreneurial process to unfold. However, entrepreneurship scholars have insufficiently addressed stress processes that may be associated with this uncertainty. We argue that uncertainty is the concept connecting both the entrepreneurial and stress processes. We discuss the link between the two processes regarding: (1) opportunity recognition, (2) opportunity exploitation, and (3) associated outcomes. We then illustrate how future research should incorporate the interaction between the two processes using a morphological box and discuss how such research would change the way we specify entrepreneurial process models and study entrepreneurial behavior

3D Reactive Transport simulations of Uranium In Situ Leaching : Forecast and Process Optimization

International audience3D reactive transport model is an efficient tool to simulate ISR operation: indeed the whole process is based on reacting fluid circulation in porous media. The simulation can help quantify the processes at stake, and optimize the ore dissolution rate and the use of reagents. It can also be used to test the efficiency of alternative well patterns or to refine well screens vertical position within the ore body.The model relies on an appropriate description of uranium bearing aquifer. 3D geologic block models based on geological observations and geostatistical reconstruction were used. They describe the spatial distribution of both hydrodynamic and geochemical units (including uranium and other mineral concentrations). Also, a correct assessment of the chemical reactions (thermodynamic and kinetics) at stake is necessary.This study details the application of a 3D reactive transport approach (using the code HYTEC) at operation scale in Kazakhstan (technological blocks, approx. 70 wells each). Among other simulation results available, it has been shown that the evolution of the uranium concentration in the production wells and the acid consumption can be accurately forecasted. Moreover, various scenarios of operational optimization, mainly dedicated to well patterns and wells screen localization refinement, were simulated. The results assess the interest of using 3D reactive transport modelling tool for such optimization purposes

Revisiting amorphous organic matter in Kimmeridgian laminites: what is the role vulcanization process in the amorphization of organic matter ?

International audienc

Unravelling the origin of ultralaminae in sedimentary organic matter: the contribution of bacteria and photosynthetic organism

International audienc

Unravelling the origin of ultralaminae in sedimentary organic matter: the contribution of bacteria and photosynthetic organism

International audienc

Reactive transport simulation of uranium ISR: effect of the density driven flow

International audienceThe ISR (in situ recovery) operation of a perched uranium mineralization within a thick, permeable aquifer can become a sensitive issue. Indeed, density difference between the injected high-density acidic solutions and fresh groundwater can bring a high quantity of solutions toward the bottom of the aquifer. This phenomenon has to be taken into account from an operational point of view because the loss of solution can involve both an acid overconsumption and a lower production of uranium; and from an environmental point of view for the remediation of the exploited aquifer. The main topics of this study are: (1) to represent the hydrogeological behaviour of such an ISL operation for quantifying the lost part of uranium and acid linked to the density driven flow, (2) to test the sensitivity of operational parameters (flow rates, well field patterns, positioning of well screens) to optimize the uranium recovery and acid consumption. 3D simulations have been realised with a reactive transport code including a density driven flow module (code HYTEC). The simulations take into account for the reaction processes within the ore body: flow and transport of dissolved reagents, oxidative dissolution of uranium, effect of pH buffers. The results of simulations have shown that the permeability of porous media is a key parameter as it controls the rate of the solution sinking towards the bottom of the aquifer. Using a variety of injection scenarios and geometrical designs, the simulations indicate that possible means to reduce the solutions loss can be identified and tested with such a modelling approach