The behaviour of metal isotopes in organic-rich black shales during diagenesis and catagenesis
Lead partner: University of Oxford, UK
Marie Curie fellow: Hanne Wouters, Belgium (ESR, PhD student)
Non-traditional stable metal isotopes are powerful proxies to constrain primary organic productivity (e.g. Cd and Ni isotopes) and the redox state of the depositional system (e.g. Mo, Cr and Fe isotopes). Organic-rich black shales are typically enriched in metals, and the relative concentrations and the isotope signatures in these types of sediments provide a wealth of information on present and past depositional environments. One of the key uncertainties in deriving information on palaeo-redox and palaeo-productivity levels from black shales is the behaviour of metals and their isotopes during post-depositional processes such as burial and heating. Catagenesis and the generation of oils that are known to be enriched in metals, may also significantly modify the metal composition of post-generation black shales. Samples to be collected from the field and from Shell’s proprietary sample collection will represent a range of sediments, including those showing a range of maturation effects. The aim is to complement and integrate natural data on sediments and environmental samples with experimental results using “simulated hydrocarbon generation experiments” under lab-controlled conditions.
The principal goals are:
(1) Constrain the processes resulting in depositional and post-depositional isotope fractionation;
(2) Evaluate the use of metal isotopes to determine depositional environments;
(3) Assess the potential of isotopes as a novel indicator of maturity.