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Linking Fe-Ca metasomatism and hydrothermal sulfide mineralization in mantle rocks: insights from geochemistry and thermodynamic modeling
No full textInternational audienceUltramafic-hosted seafloor massive sulfide deposits have been reported in present-day oceanic settings over the past thirty years. These deposits and their fossil on-land analogs represent potential important resources for Cu, Co, Ni, Zn. However, developing comprehensive genetic models for deep-seatedhydrothermal processes is hindered by limited seafloor observations and reliance on large-scale geophysical studies. To overcome this issue, one can examine fossil systems, where hydrothermal plumbing architecture may be preserved. The Platta nappe (Swiss Alps) preserves a Jurassic hydrothermal system (the Marmorera-Cotschen Hydrothermal System; MCHS), where Cu-Fe-Co-Zn-Ni mineralization is associated with coeval Fe-Ca silicates (ilvaite, hydro-garnet, and diopside). The MCHS is hosted in serpentinites, which have been exhumed along a Jurassic paleo-detachment —a fossil analog ofa large-scale exhumation fault that forms oceanic core complexes at slow-spreading ridges— juxtaposing basalts onto serpentinites. The serpentinized footwall has numerous mafic intrusions, and the mafic-ultramafic rock contacts served as pathways for ore-forming fluids. Petrographic analyses and thermodynamic modeling indicate that Fe-Ca metasomatism occurred between 300‒360°C and at relatively low fO2 (from Magnetite-Native Fe to Fayalite-Magnetite-Quartz buffers), likely coeval with early-stage serpentinization. The composition of Fe-Ca silicates (Co, Ni, and REE contents, measured by in situ LA-ICP-MS) points to heterogeneous geochemical reservoirs involved during fluid-rock interaction. The geochemical compositions of Fe-Ca silicates in barren assemblages indicate an ultramafic-dominated system, while Fe-Ca silicates in mineralized assemblages point to an open-system, involving fluids derived from both mafic and ultramafic rocks. Mineralogical and geochemical signatures of Fe-Ca silicates in the MCHS do not support genetic relationships with common rodingitization. Our results suggest that Fe-Ca metasomatism may be a widespread deep-seated alteration along mafic-ultramafic rock contacts or in mantle rocks modified through melt-rock interaction accompanying mantle exhumation. We acknowledge JdC Fellowship (FJC2021-047190-I), funded by MCIN/AEI/10.13039/501100011033 with EU Next Generation Funds and funding from project PID2022-136471NB-C21 “The role of ultramafic rocks and related rocks in the sulfur and water cycles and their implications for the redox state of subduction zones (RUSTED)”, funded byMCIN/AEI/10.13039/501100011033 and by the ESF+
Chanter la gloire du roi en 1825 : le sacre de Charles X au temps du sacre des poètes
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Triassic Intracontinental Crustal Reworking of the Eastern Tianshan: New Insights From Late Triassic Adakitic and Low‐Sr/Y Granitoids in the Bogda Range
No full textInternational audienceAbstract Continental intraplate magmatism remains a fundamental challenge in Plate Tectonics. Triassic magmatism represents a critical phase in the evolution of the Central Asian Orogenic Belt and continues to provoke debate about its tectonic setting. This study presents an integrated analysis of field, petrographic, geochronologic, geochemical, and isotopic data from two newly identified Triassic granitoids in the Bogda Range: an adakitic porphyry and a low‐Sr/Y granite porphyry. Zircon U‐Pb dating yields nearly coeval crystallization ages of 221–220 Ma and 219–217 Ma, respectively. Both granitoids are characterized by high SiO 2 and K 2 O content, low MgO (Mg # ) and Ni content, and elevated K 2 O/Na 2 O and Th/Nb ratios. They have also depleted whole‐rock Sr‐Nd and zircon Hf isotopic compositions, indicative of juvenile crustal sources. The adakitic porphyry exhibits high Sr/Y and (La/Yb) N ratios, low Rb/Sr ratios, and weak Eu anomalies, suggesting derivation from garnet‐stable mafic lower crust. In contrast, the granite porphyry displays low Sr/Y and (La/Yb) N ratios, consistent with a plagioclase‐stable source. By integrating these results with regional data, we propose that the diversity of Triassic magmatism in the Eastern Tianshan is due to the reworking of juvenile and ancient crust at different depths and temperatures, resulting in arc‐like geochemical signatures. This process was associated with transcurrent tectonics and variable mantle contributions in a continental intraplate setting
L'acteur tiers : garant de l'engagement des producteurs au sein des circuits courts alimentaires de proximité ?
No full textInternational audienceThe development of collective actions, such as the creation of platforms, helps to sustain local, short food supply chains by connecting small-scale producers with customers who require large-volume processing and a variety of customer types, such as catering companies and individuals. Producers' commitment to creating and developing these meta-organisations is an important issue. Some research highlights the essential role played by third parties in structuring a network's collective actions. By studying three platforms, we demonstrate how the various roles played by third parties — architect, conductor and guardian — facilitate producer engagement.Le développement d'actions collectives de type plateformes permet de pérenniser les circuits courts alimentaires de proximité en mettant en relation de petits producteurs avec des clients nécessitant de traiter des volumes importants et des clients très différents (restauration collective ou particuliers). L'engagement des producteurs dans la création de ces méta organisations, puis dans leur développement est un enjeu important. Certaines recherches soulignent que les acteurs tiers jouent un rôle essentiel dans la structuration des actions collectives d'un réseau. A travers l'étude de trois plateformes, nous montrons comment les différents rôles tenus par l'acteur tiers -architecte, chef d'orchestre, gardien permettent le développement de l'engagement des producteurs
Design Innovations and Performance Assessment of Small Wind Turbines: A Review for Decentralized and Off-grid Applications
No full textInternational audienceThis study provides a critical and comparative review of recent technological innovations in small wind turbines (SWTs), with a focus on their relevance for decentralized energy production in both urban and remote environments. It is based on a descriptive and analytical evaluation of technologies reported in the scientific literature from 2019 to 2024. Five representative SWT models are selected, Liam F1 UWT, Aeroleaf, IceWind, AeroMINE, and Harmony, covering both horizontal and vertical axis designs, including drag-based, lift-based, and pressure-gradient-based systems. A multi-criteria assessment framework is applied, considering performance under low to moderate wind conditions, as well as factors such as aerodynamic configuration, materials, installation context, and cost-effectiveness. Particular attention is paid to turbine start-up thresholds, acoustic levels, urban integration, and turbulence tolerance. The analysis shows that while some models such as Harmony and AeroMINE offer adaptability to complex wind profiles in urban areas, others like IceWind and Liam F1 are more suited for remote or low-noise environments. The role of aerodynamic design, ranging from Savonius and Darrieus profiles to helical blades and motionless Venturi-based systems, is highlighted as a key determinant of performance. The study concludes with recommendations for enhancing durability, scalability, and hybrid potential in future SWT developments
Altered development in rodent brain cells after 900 MHz radiofrequency exposure
No full textInternational audienceHealth risks related to 900 MHz 2 G frequency exposure remain inconclusive under current regulatory standards. Research into potential long-term effects is ongoing, particularly as the use of mobile networks and wireless devices increases. This study investigates the effects of non-thermal exposure levels of mobile phone 900 MHz radiofrequency electromagnetic field (RF-EMF) on rodent neurodevelopment. In vivo, the effects of pre- and post-natal 0.08 and 0.4 W/kg specific absorption rate (SAR) exposure were assessed for their impact on the proteomic profile at postnatal day 0 (PND 0). Brain-derived neurotrophic factor (BDNF), BrdU+ proliferative cells, synaptogenesis, and oxidative stress in the hippocampus and cortex of rat pups were studied at PND 8 and PND 17. Effects of the lowest SAR (0.08 W/kg) were assessed in vitro to afford mechanistic data regarding neural stem cells (NSCs) differentiation. In vivo results showed a decrease in BDNF level and BrdU+ proliferative cells with a decrease in synapse balance (excitatory synapses/inhibitory synapses). In vitro, at 0.08 W/kg there was an increase in Ki-67 + proliferative cells, apoptosis, and double-strand DNA breaks in NSCs. A lower ratio of B1 cells (primary progenitors of NSCs) among total cerebral cells and a higher ratio of oligodendrocyte progenitor cells and astrocytes were observed in the exposed NSCs. Our findings suggest that key cellular events for brain ontogenesis are likely to undergo changes with RF-EMF 900 MHz exposure during early development. These support the hypothesis that the developing central nervous system is vulnerable to RF-EMF exposures in rodents at regulatory thresholds
Drought-Induced Epigenetic Memory in the cambium of Poplar Trees persists and primes future stress responses
No full textInternational audienceUnderstanding how perennial plants such as trees perceive, integrate and memorize environmental stresses like water deficit is crucial in the context of climate change. We investigated short-term and transannual memory of water deficit in cambium derived tissues of poplars ( Populus spp .) using two contrasting genotypes and four genetically modified epitypes with altered DNA methylation machinery. We found persistent changes in hormone profiles, gene expression and DNA methylation one week after stress relief, consistent with a molecular short-term stress memory. These signatures revealed distinct adaptive strategies between genotypes and marked variability between epitypes, demonstrating that both genetic and epigenetic backgrounds drive stress memory. Trees already exposed to water deficit in Year 1 showed distinct physiological and molecular responses when subjected to a second water deficit in Year 2, supporting the persistence of a long-term trans-annual memory possibly involved in tree priming. The higher molecular plasticity observed in the intrinsically more sensitive genotype contrasted with the higher stability observed in the intrinsically more tolerant genotype. The number of memory genes was limited, but the results suggested that stable drought-induced DNA methylation changes, particularly in the CG context, contribute to long-term stress imprinting. Our findings highlight the cambium as a reservoir for stress memory in trees and suggest that DNA methylation dynamics shaped by genetic predisposition, acting through cis- and trans-regulatory routes, may help fine-tuning growth vs. survival strategies across longer time frames. These insights open perspectives for harnessing epigenetic variation in tree breeding and management under increasing drought frequency
A novel meta-learning-based spatio-temporal modeling approach for thermal error prediction of multiple machine tools with few labeled data
No full textInternational audienceThermal errors have a significant effect on the machining accuracy of high-precision machine tools. Developing a high precision and robust thermal error prediction model plays an important role in compensating thermal error and improving machining accuracy. Due to the inherent discrepancies between the machine tools, there exists certain differences in the distribution of thermal error data among different machine tools. Therefore, the thermal error prediction model developed for one machine tool may not be directly applicable to others. To address the aforementioned issue, a novel spatio-temporal thermal error prediction method based on meta-learning is proposed in this paper. This method aims to enhance the robustness of the model under varying operating conditions of a single machine tool, and improve generalization across multiple machine tools. Firstly, a small amount of operational data is collected from each machine tool for subsequent modeling and training purposes. Subsequently, a novel spatio-temporal modeling approach called Stacked Graph Attention Network (SGAT)-Transformer is employed for thermal error modeling. In this framework, the SGAT is responsible for extracting the spatial characteristics of the thermal error, while the Transformer captures the temporal dependencies and time-interaction behaviors associated with these errors. Additionally, to enhance the robustness and generalization ability of the SGAT-Transformer model, this paper introduces a meta-learning approach known as Model-Agnostic Meta-Learning (MAML), which enables rapid adaptation to unknown operating conditions. Finally, two validation cases are designed to further assess the model's robustness and generalization capacity
Halogens in proto-Iceland plume basalts
No full textInternational audienceMelt inclusions in olivine phenocrysts from high 3He/4He proto-Iceland plume (PIP) basalts from Baffin Island and West Greenland have elevated Br/Cl ratios, extending to values significantly above those found in mid-ocean ridge basalt (MORB) and ocean island basalt (OIB). Chlorine isotope compositions are indistinguishable from MORB-source mantle and high Br/Cl occurs in the absence of geochemical indicators for serpentinite, altered oceanic crust or sediment. The highest Br/Cl occurs in melt inclusions from basalts with the highest 3He/4He. The high Br/Cl ratios are at the high end of the range of putative Earth-source meteorites (CI- and CM-type carbonaceous chondrites). The PIP melt inclusion compositions are consistent with the addition of a small volume of halogen-rich, high Br/Cl chondritic material to halogen-depleted, low Br/Cl mantle