CD : Les pegmatites archéennes à lithium-césium-tantale (LCT) d'Eeyou Istchee Baie-James, Québec: contraintes pétro-génétiques et tectoniques // CD : Archean lithium-caesium-tantalum (LCT) pegmatites of Eeyou Istchee Baie-James, Québec: petro-genetic and

Ce projet porte sur la compréhension et la caractérisation des processus géologiques, notamment tectoniques et magmatiques, liés à la mobilité du lithium et éléments accompagnateurs à savoir césium et tantale, lors de la mise en place de pegmatite LCT d'âge archéen.
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The Archean eon is marked by the formation and ultimate stabilization of cratons, leading to the long-term preservation of early continental crust and associated metallogenic systems (Cawood et al., 2022). It encompasses the Primitive (~3.8–3.2 Ga) and Juvenile (~3.2–2.5 Ga) Earth phases. The exceptional endowment of Archean terranes in Li-rich pegmatite deposits is paradoxical, given the prevailing view that continental crust during the Archean was immature, more mafic and consequently depleted in lithophile and incompatible metals compared to its Proterozoic and Phanerozoic counterparts (McCauley and Bradley, 2014).
This project aims to develop an integrated litho- and petro-structural model for the emplacement of lithium-bearing pegmatites, focusing on the role of structural pathways in magma/fluid migration and metal (re-)concentration processes. The study focuses on the Eeyou Istchee James Bay region (EIBJ), across the Opinaca and La Grande subprovinces, which represent contrasting lithotectonic domains. The spatial distribution of LCT pegmatites, mainly hosted in La Grande greenstone belts around the Opinaca metamorphic dome, suggests a strong genetic and structural link between both subprovinces.
The project is structured around two complementary axes:
(1) Litho-structural framework and timing of lithium-bearing magmatism.
We will constrain the tectono-metamorphic evolution of the Opinaca–La Grande transition, a key zone for magma transfer, through integrated structural analysis, field transects, and petrochronology (U–Pb dating on zircon, monazite, and ore minerals). These data will be combined with thermodynamic modeling (P–T–t–X paths) and regional geophysical datasets (from SIGEOM) to establish a robust geodynamic framework.
(2) Magmatic–hydrothermal processes and metal enrichment.
This axis focuses on investigating the magmatic-hydrothermal and metal (re-)mobilization in Archean pegmatites. The project will assess the role of metasomatism (as albitization), fluid–rock interaction, and sub-solidus processes in metal (Sn, Nb, Ta) transport and (re-)precipitation. This will be achieved through coupled crystallochemical analyses (micas, oxide minerals) and fluid inclusion studies (microthermometry and trace elements).
By combining multi-scale structural, geochemical and fluid inclusions, and petrochronological approaches, this project will provide new constraints on the formation of Archean rare-metal pegmatites.
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Début de la thèse : 01/10/2026

Public funding alone (i.e. government, region, European, international organization research grant)

Concours pour un contrat doctoral

Université de Lorraine

607 SIReNa - SCIENCE ET INGENIERIE DES RESSOURCES NATURELLES

Diplôme de Master en Géologie, spécialités Ressources minérales ou domaines connexes. Des compétences en géologie structurale, pétrologie et inclusions fluides sont des atouts. Excellentes compétences en communication écrite et orale (l'anglais est requis).
Master's degree in Geology, with a specialization in Mineral Resources or related fields. Skills in structural geology, petrology, and fluid inclusions are an asset. Excellent written and verbal communication skills (English required).