Job description
CIFRE PhD thesis proposal :
Post-orogenic reactivation of rift-related faults: Tectonic evolution, structural and petrophysical description, and implications for fluid circulation
Host University: Cergy Paris University, France
Supervisors:
- Geoffroy Mohn, Jean-Baptiste Regnet, Philippe Robion (CY Cergy Paris University)
- Laetitia Le Pourhiet (Sorbonne University), Thibault Duretz (Frankfurt University)
- Sébastien Chevrot (OMP, Toulouse)
- Rodolphe Lescoutre (Mantle8, Grenoble)
Context
Accelerating the global energy transition necessitates the identification and development of efficient low-carbon and renewable energy sources. Among the emerging candidates, natural hydrogen (also called white/geologic hydrogen) is gaining attention as a promising, sustainable and potentially abundant energy resource. Recent advances in natural hydrogen exploration emphasize serpentinization—the hydration of ultramafic rocks—as one of the most efficient geological processes for hydrogen generation.
As part of this course on natural hydrogen exploration, understanding present-day deformation in mountain belts is fundamental, not only to assess seismic hazards, but also to identify the primary sources (meteoric infiltration, deep basinal brines, dehydration/metamorphism-related fluids, and de-serpentinization reactions) and pathways of water within the crust. Indeed, the availability, circulation, and long-term evolution of water remain among the most critical yet poorly-constrained parameters controlling hydrogen production along mountain belts. Together with the volume of mantle rocks, water acts as the limited factor for hydrogen production in these systems, and its flux, renewal, and chemical evolution are governed by the tectonic and hydrological evolution of the crust. In that aspect, recent studies suggest a structural relationship between present-day seismicity in post-orogenic belts and the reactivation of rift-inherited structures (Fillon et al., 2021; Lescoutre et al., 2025), which may facilitate the deep infiltration of meteoric water. Yet the extent, controlling factors, and trigger of such localized deformation remain poorly understood. Because these fault zones commonly connect to exhumed mantle bodies at depth (Zwaan et al., 2025), they may act as persistent hydrological networks, channelling fluids to great depths (Simpson, 2024). Such plumbing systems could sustain ongoing serpentinization of ultramafic rocks, maintaining continuous natural hydrogen production over geological timescales. However, the flux, rate, structural control, and temporal variability of water circulation within these fault systems—and their influence on the efficiency and persistence of serpentinization—remain largely unconstrained.
Profile required
Main objectives:
The objectives of this PhD are threefold:
- To investigate the present-day seismicity distribution in selected orogens (e.g., Pyrenees) and their link with rift-inherited structures, in particular the location of the former rift necking zones. With help of geological and geophysical data (together with the help of Mantle8 in-house technologies), the aim is to propose coherent 2-D geological cross-sections and 3-D geological models within the orogens, using geological modelling software (Move, Petrel). These geological cross-sections and 3-D models should account for the pre-orogenic rifted margin template and highlight the relationship between the present-day earthquake distribution and the former rift architecture. The location and structural evolution of the former exhumed mantle domain in the orogenic belt will be documented. Structural/petrological fieldwork to complement dataset could be envisaged.
- To determine and characterize rift-inherited post-orogenic deformation zones (thickness, structures, porosity, permeability, mineralogy, fluids geochemistry) and related meteoric water inflow. To do so, field work will be conducted in targeted areas to describe, measure, and sample deformation zones. Subsequent petro-physical (porosity and permeability characterization, acoustic and electrical analyses and geomechanical property) and geochemical (whole rock and mineral) analysis of field samples in world-class laboratories (Cy Cergy Paris University) would help further characterize these structures and their importance for fluid migration within the crust. These results will provide critical new constraints for fluid circulation along fault zone.
- To model the circulation of water at depth along faults that originally formed during lithospheric extension and possibly reactivated during orogenic and post-orogenic events. Based on the data collected during the previous objectives of the PhD and the determined geological template, the numerical modelling will aim to evaluate fluxes, rates, and water penetration depth along seismically active fault.
Altogether, the results developed in this PhD would represent a substantial step into the comprehension of natural hydrogen systems and especially the structures controlling the water supply towards mantle rocks at depth. Eventually, a coherent tectono-thermo-hydro-physical model highlighting the controlling factors for hydration of mantle bodies along mountain belts and the production of natural H2 represents the ultimate objective of this PhD.
Candidate profile:
We are seeking a highly motivated, multidisciplinary student eager to engage with a broad range of geoscience topics, including tectonics, structural geology, petrophysics, hydrogeology, and geochemistry. A solid background in tectonics/structural geology, petrophysics, and fluid dynamics is essential. Given the importance of both field investigations and 3D geological interpretations, the ideal candidate will demonstrate a genuine interest in fieldwork, supported by strong knowledge in structural geology, petrology, and petrophysics. Experience with programming languages (e.g., Python, Matlab) as well as proficiency in numerical modelling, will be considered a strong asset.
We offer the opportunity to pursue a PhD in collaboration with leading researchers and industry experts, providing a foundation for careers in both academia and the energy/resource industry. Although the primary focus is natural hydrogen exploration, the research themes and methodologies are broadly applicable to geothermal systems and mineral resource studies (e.g., lithium).
Company description
🇬🇧 Mantle8 is a deep-tech exploration company dedicated to unlocking the potential of natural hydrogen as a new clean energy resource.
By combining advanced geoscience, subsurface modeling and cutting-edge simulation technologies, Mantle8 develops innovative exploration methods to identify and evaluate natural hydrogen systems deep within the Earth.
Our multidisciplinary team brings together geoscientists, engineers, data scientists and explorers who share a common ambition: advancing scientific understanding while building the foundations of a new energy frontier.
From regional exploration concepts to prospect generation and technological development, Mantle8 works at the intersection of research, innovation and industrial application to accelerate the emergence of natural hydrogen as part of the global energy transition.
At Mantle8, exploration is not only about discovering new resources — it is about expanding knowledge, challenging assumptions and building solutions for the future of energy.
Why is everything in English if Mantle8 is based in the heart of the French Alps?
Because Mantle8 is an international adventure.
As of March 2026, our team includes 21 people representing 9 different nationalities. This diversity is one of our greatest strengths, and English is the language that allows everyone to collaborate, debate ideas and build things together.
We love our home in the French Alps, but inside Mantle8 our common ground is English — from meetings and technical discussions to emails and, yes, even our jokes.
So if you’re thinking about joining us, English is not just helpful — it’s essential to be part of the conversation.
🇫🇷 À propos de Mantle8
Mantle8 est une entreprise deep-tech d’exploration dédiée à révéler le potentiel de l’hydrogène naturel comme nouvelle ressource d’énergie propre.
En combinant géosciences avancées, modélisation du sous-sol et technologies de simulation de pointe, Mantle8 développe des méthodes d’exploration innovantes permettant d’identifier et d’évaluer les systèmes d’hydrogène naturel présents en profondeur dans la Terre.
Notre équipe pluridisciplinaire réunit géoscientifiques, ingénieurs, data scientists et explorateurs partageant une ambition commune : faire progresser la connaissance scientifique tout en construisant les bases d’une nouvelle frontière énergétique.
De la génération de concepts d’exploration régionaux à l’identification de prospects et au développement technologique, Mantle8 opère à l’interface entre recherche, innovation et application industrielle afin d’accélérer l’émergence de l’hydrogène naturel dans la transition énergétique mondiale.
Chez Mantle8, l’exploration ne consiste pas seulement à découvrir de nouvelles ressources — il s’agit aussi d’élargir la connaissance, de remettre en question les certitudes et de construire des solutions pour l’énergie de demain.
Pourquoi tout est-il en anglais alors que Mantle8 est basée au cœur des Alpes françaises ?
Parce que Mantle8 est avant tout une aventure internationale.
Début mars 2026, notre équipe compte 21 personnes représentant 9 nationalités différentes. Cette diversité est l’une de nos plus grandes forces, et l’anglais est la langue qui nous permet de collaborer, de débattre d’idées et de construire ensemble.
Nous sommes très attachés à notre ancrage dans les Alpes françaises, mais chez Mantle8 notre langue commune est l’anglais — que ce soit pour les réunions, les discussions techniques, les e-mails et, oui, même nos blagues.
Donc si vous envisagez de nous rejoindre, l’anglais n’est pas seulement utile : il est essentiel pour faire partie de l’aventure.
On 5/29/2026