PhD position in geology: Mineral system at the sedimentary basin scale (M/F)

Job Description

Thesis Subject

Mineral system, an integrated approach at the sedimentary basin scale: the case of Pb-Zn(-Ge) deposits in the axial zone of the Central Pyrenees

Scientific Context: The most striking feature of metals contained in sedimentary basins is their ubiquitous association with organic matter-rich layers. One of the major fundamental questions is: what is the role of organic matter in a deposit's mineral system: source, transport, or trap? The study of such complex systems (fluids-organic matter-metals) requires a synergy of complementary approaches at the interface between geosciences, physics, and chemistry, applicable across a very wide range of scales, from the molecule to the metallogenic province. This synergy takes shape within the PEPR ORGMET, a major unifying project, under which this PhD thesis will be conducted. Based on an integrated approach to the mineral system at the basin scale, it will contribute to revising the potential of strategic minerals in the Pyrenees.

Scientific Objectives: The candidate will build upon the study of Paleozoic organic matter-rich sedimentary basins in the axial zone of the Central Pyrenees, which host Pb-Zn(-Ge) deposits. The objective of this thesis is to study and define, at the scale of these basins, the geological architectures (structural and stratigraphic) and their emplacement history. This will be achieved by integrating the various elements of the mineral system leading to the formation of a Pb-Zn(-Ge) deposit: potential metal sources, tectonic and thermal drivers, potential carrier fluids, fluid migration pathways, and trapping mechanisms. Such a regional approach, innovative in the Pyrenees, will allow for a better positioning and understanding of the interactions between the different components of the mineral system.

Methodological Approaches:
• Compilation and analysis of existing data
• Fieldwork campaigns for geological surveys and sampling
• Mineralogical and geochemical characterization of samples
• Structural modeling, using the balanced cross-section technique (MOVE software), and basin analysis
• Low-temperature thermochronology
• Raman spectroscopy and vitrinite reflectance
• LA-ICP-MS imaging for in situ U-Pb dating of carbonate minerals
• Thermal modeling

The analyses and modeling will be carried out in collaboration with other partner laboratories of the PEPR ORGMET.

Expected Results: This research will be carried out in several stages:
1. Geometric analysis of the current structural and stratigraphic architecture along regional cross-sections integrating known deposits, and their relationships with organic matter-rich layers;
2. Dating and characterization of the major tectonic and thermal events that affected the Paleozoic basins;
3. Reconstruction of the different deformation stages of the Paleozoic basins from an initial state representing the basins at the end of the Ordovician;
4. Mineralogical and geochemical characterization of the mineralizations;
5. Structural and thermal modeling of the different deformation stages, integrating the potential origins and migration pathways of mineralizing fluids, as well as trapping processes and zones. The geometric and temporal relationships between fluids and organic matter-rich layers will be established.

Supervisors:
• Director: P. Baby
• Co-Director: G. Pokrovski
• Co-supervisor: S. Brusset
• Co-supervisor: G. Hoareau

Candidate Profile and Required Skills: The candidate must have field experience in mineralized and altered rocks, basin analysis, balanced cross-section construction, and the use of thermochronological data. They must be proficient in structural modeling software such as MOVE, as well as thermal modeling software. Knowledge of transmitted and reflected light petrography is required, and the candidate should be familiar with fluid inclusions and the application of stable isotopes. They must demonstrate the ability to integrate spatial and temporal data at the sedimentary basin scale to characterize its mineral system.

References :
Baby, P., Prudhomme, A., Brusset, S., Robert, A., Roddaz, M., Calderon, Y., Eude, A., Gil, W., Hermoza, W., Hurtado, C., Brichau, S., Calvès, G., Antoine, P.-O., & Salas-Gismondi, R. (2025). The Northern Central Andes and Andean tectonic evolution revisited: An integrated stratigraphic and structural model of three superimposed orogens. In Earth-Science Reviews (Vol. 260, p. 104998). Elsevier. https://doi.org/10.1016/j.earscirev.2024.104998
Carquet A., Féraud J. (2001) Etude bibliographique des mines de zinc et plomb de Sentein et Bulard (Ariège) en appui aux études archéologiques des concessions minières orphelines: reconnaissance, potentiel minier et géologie. Étude réalisée dans le cadre des actions de Service public du BRGM 00-DEP-409 Rapport BRGM/RP-50917-FR.
Centrella S., Beaudoin N.E., Derluyn H., Motte G., Hoareau G., Lanari P., Piccoli F., Pecheyran C., Callot J.P. (2021) Micro-scale chemical and physical patterns in an interface of hydrothermal dolomitization reveals the governing transport mechanisms in nature: Case of the Layens anticline, Pyrenees, France. Sedimentology 68, 834-854. https://doi.org/10.1111/sed.12808
Galdos R., Vallance J., Baby P., Salvi S., Schirra M., Velasquez G., Viveen W., Soto R., Pokrovski G.S. (2024) Origin and evolution of gold-bearing fluids in a carbon-rich sedimentary basin: A case study of the Algamarca epithermal gold-silver-copper deposit, northern Peru. Ore Geology Reviews 166, 105857. https://doi.org/10.1016/j.oregeorev.2023.105857
Groves D.I., Santosh M., Müller D., Zhang L., Deng J., Yang L.-Q., Wang Q.-F. (2022) Mineral systems: Their advantages in terms of developing holistic genetic models and for target generation in global mineral exploration. Geosystems and Geoenvironment 1(1), 100001. https://doi.org/10.1016/J.GEOGEO.2021.09.001
Cugerone A. (2019) Impact of recrystallization and metamorphism on the mobility of germanium and related elements in orogenic Pb-Zn deposits : example of the Pyrenean Axial Zone mineralizations (France-Spain). Earth Sciences. Université Montpellier.
Hoareau G., Claverie, F., Pecheyran, C., Barbotin, G., Perk, M., Beaudoin, N. E., Lacroix, B., & Rasbury, E. T. (2024): The virtual spotapproach: a simple method for image U-Pb carbonate geochronology by high-repetition rate LA-ICP-MS, EGUsphere [preprint].
https://doi.org/10.5194/egusphere-2024-2366
Poitrenaud T., Marcoux É., Augier R., Poujol M. (2021) The perigranitic W-Au Salau deposit (Pyrenees, France): Polyphase genesis of a late Variscan intrusion related deposit. BSGF - Earth Sciences Bulletin 192. https://doi.org/10.1051/BSGF/2020044
Pokrovski G.S., Dubessy J. (2015) Stability and abundance of the trisulfur radical ion S3
- in hydrothermal fluids. Earth and Planetary Science Letters 411, 298-309. https://doi.org/10.1016/j.epsl.2014.11.035
Pokrovski G.S., Kokh M.A., Guillaume D., Borisova A.Y., Gisquet P., Hazemann J.-L., Lahera E., Del Net W., Proux O., Testemale D., Haigis V., Jonchière R., Seitsonen A.P., Ferlat G., Vuilleumier R., Saitta A.M., Boiron M.-C., Dubessy J. (2015) Sulfur radical species form gold deposits on Earth. Proceedings of the National Academy of Science of the US (PNAS) 112(44), 13484–13489.
https://doi.org/10.1073/pnas.1506378112
Pokrovski G.S., Kokh M.A., Desmaele E., Laskar C., Bazarkina E.F., Borisova A.Y., Testemale D., Hazemann J.L., Vuilleumier R., Ferlat G., Saitta A.M. (2021) The trisulfur radical ion S3 •− controls platinum transport by hydrothermal fluids. Proceedings of the National Academy of Sciences of the USA - PNAS, 118 (34), e2109768118. https://doi.org/10.1073/pnas.2109768118
Pokrovski G.S., Stefánsson A.S., Kouzmanov K. (2025) Sulfur in hydrothermal fluids. Chapter 4. In: The Role of Sulfur in Planetary Processes: from Cores to Atmospheres. D Harlov, GS Pokrovski (eds.), Springer Nature (accepted).
Vallance J., Galdos R., Balboa M., Berna B., Cabrera O., Huisa F., Baya C., de Vyver C. van Viveen W., Béziat D., Salvi S., Brusset S., Baby P., Pokrovski G.S. (2024) Combined effect of organic carbon and arsenic on the formation of sediment-hosted gold deposits: A case study of the Shahuindo epithermal deposit, Peru. Economic Geology 119(1), 85-112. https://doi.org/10.5382/econgeo.5040

Your Work Environment

The PhD thesis will be conducted within the framework of the PEPR "Sous-sol, bien commun" ORGMET project (https://www.soussol-bien-commun.fr/fr/appel-projets-2024/orgmet-role-du-carbone-organique-dans-formation-des-ressources-des-metaux), based in the GEOEX team at the Géosciences Environnement Toulouse laboratory (GET - UMR 5563). The project will benefit from active collaborations with the Laboratoire des Fluides Complexes et Réservoirs at UPPA (Pau) and the Autonomous University of Barcelona (Spain). It will require substantial fieldwork in the highest elevation areas of the Central Pyrenees.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

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