Doctoral position in isotope geochemistry for marine authigenic clay formation and the silicon cycle
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Doctoral position in isotope geochemistry for marine authigenic clay formation and the silicon cycle
100%, Zurich, fixed-term
We are seeking a curious and motivated doctoral student to join the Earth Surface Geochemistry group at ETH Zurich in order to study the formation of authigenic clay minerals in the laboratory and natural environment and explore their impact on the global cycle of silicon and its isotopes.
Marine authigenic clay formation, sometimes called "reverse weathering," is being increasingly recognised as an important facet of the series of Earth surface processes that interact to regulate ocean chemistry, elemental cycles, and the exogenic carbon cycle.
Project background
In modern marine sediment, small-scale and poorly ordered authigenic clays form during early diagenesis when two key ingredients are present: reactive silica, usually the hard parts of siliceous organisms like diatoms; and reactive metal phases like iron (oxyhydr)oxides and aluminium oxides sourced from the continents. As a consequence, the marine biogeochemical cycle of silicon is a key control on marine authigenic clay formation in the modern ocean, and how this process may have changed in Earth's past.
At the same time, numerous lines of evidence suggest that authigenic clay formation strongly fractionates the stable isotopes of silicon, such that silicon isotopes may prove to be a sensitive tracer of the processes involved in early silica diagenesis -- but also that authigenic clay formation, and how it has changed in the past, may exert an important influence on the marine isotope mass balance of silicon.
With this background, this research project aims to resolve key existing uncertainties regarding the influence of authigenic clay formation on silicon and its isotopes, thus allowing a better understanding of its systematics in the modern system, and of how micro-scale clays can influence global elemental cycles through Earth's history.
Job description
Your research will be situated at the interface between isotope geochemistry and the characterisation of small-scale authigenic minerals using advanced imaging techniques. You will work on a diversity of samples ranging from experimentally precipitated phyllosilicates to natural marine sediment. Your tasks will centre around:
- using isotope geochemical methods to process synthesised and natural samples for analysis of Si stable isotope composition by MC-ICP-MS
- characterising the nature and structure of experimental and naturally-occurring authigenic clay minerals using advanced microscopic analyses (FTIR, SEM-EDX, TEM-SAED)
- analysing the chemical composition of reactive silica pools in natural marine sediment by ICP-MS, and using statistical techniques to infer their nature
- interpreting your results in the context of the broader literature, and understanding their implications for the global silicon cycle
- presenting your results at international conferences and in peer-reviewed journals
While most samples have already been sourced, there are opportunities to participate in oceanographic sampling campaigns with project partners.
Profile
We are looking for a motivated candidate with:
- an MSc degree in earth or environmental sciences or a related field
- a strong interest in isotope geochemistry and advanced imaging methods
- curiosity about the diversity and complexity of marine authigenic minerals
- committment to accurate and precise lab analyses
- good command of English (spoken and written)
- the ability to work independently as well as in a collaborative environment
Prior experience in clay mineralogy, isotope geochemical techniques (clean laboratory work, column chromatography, MC-ICP-mass spectrometry), or electron microscopic imaging are an advantage but not a prerequisite.
Workplace
Workplace
We offer
- A collegial and collaborative research group studying the geochemistry of the surface Earth system
- Continued education and opportunities for networking through international conferences
- State-of-the-art mass-spectrometric facilities
- A large instrument park of electron microscopic facilities via ETH Zurich's ScopeM centre
- Secured funding for a 4-year doctoral position
We value diversity and sustainability
Curious? So are we.
We look forward to receiving your online application with the following documents:
- a CV
- a brief motivation letter
- the names of three referees
Further information about the Earth Surface Geochemistry group can be found on our website. If you have any questions regarding the position, you are welcome to contact Dr. Gregory de Souza (gregory.desouza@eaps.ethz.ch).
Evaluation of applicants will begin on 15 January 2026 and will continue until the position is filled. Early applications are encouraged.