WELCOME TO MY HOMEPAGE
Associate Professor of Geochemistry / Maître de Conférences en Géochimie
Institut de Physique du Globe de Paris - Université Paris Diderot
Laboratoire de Géochimie des Isotopes Stables
& Laboratoire de Géochimie et Cosmochimie
IPGP - Bureau 515
1 rue Jussieu
75238 Paris cedex 05, France
Phone : +33 (0)1 83 95 74 34
Fax : +33 (0)1 83 95 77 07
Reconstruction of Precambrian environments and ecosystems
My current research is essentially based on the reconstruction of paleo-environments and ecosystems using ancient sedimentary rocks from the Precambrien era (older than 540 Ma). I use stable isotope compositions (C, N, Fe, O, H, S) together with chemical and mineralogical compositions to provide constraints on the oldest traces of microbiological activities.I focuss my work on three different types of parallel and complementary approaches: (1) studies on ancient sedimentary rocks, (2) laboratory experiments to determine reliable traces of microbial activity, and (3) studies on modern analogues of ancient environments (such as anoxic lakes or oceanic bassins) for characterizing all the physico-chemical processes, from water column variations to sedimentary transformations and record.
Geochemical behavior of fluid-mobile elements during alteration and subduction of oceanic crust
The chemical composition of oceanic lithosphere formed at mid-ocean ridges is modified (i) on oceanic seafloor through seawater-crust interaction, and subsequently (ii) in subduction zones through dehydration processes related to compaction and metamorphic mineralogical transformations. Understanding the chemical changes associated with these processes is crucial to constrain the chemical evolution of mantle and surface reservoirs over geological time. I am particularly interested in unraveling behaviors, fluxes and isotopic signatures of fluid-mobile elements exchanged during these geochemical processes.
Nitrogen geodynamic cycle from Archean to Present
One of the most exciting issue of nitrogen (N) geochemical studies concerns global geodynamic cycle. Nitrogen of the Earth mantle is depleted heavy isotope relative to surface reservoirs (atmosphere, hydrosphere and crust). In contrast, surface material recycled to the mantle via subduction zones is enriched in heavy isotope and is thus very distinct from most mantle rocks. Considering the degassing of mantle nitrogen depleted in heavy isotope at mid-ocean ridges and the recycling of nitrogen enriched in heavy isotope in subduction environment, the difference in isotopic composition between internal and external reservoirs of the Earth was more pronounced in the past than currently. The origin of this isotopic imbalance between mantle and exosphere is still enigmatic and requires systematic studies of various rocks over the geological record.