Time: 9:00-10:30, 26th October (Friday)
Venue: Lecture Hall 221, Institute of Surface-Earth System Science (Building No. 16), Tianjin University
Speaker:Dr. Julien Bouchez, Institut De Physique Du Globe De Paris (IPGP)
Abstract: Lithium (Li) isotopes (ratio 7Li/6Li, expressed as δ7Li) are a powerful tracer of silicate weathering regimes at the Earth surface, as they are strongly fractionated by the formation of secondary weathering products, and as Li is not significantly involved into biological cycling nor is contained into carbonates rocks. Nevertheless, the application of Li isotopes to detrital or authigenic archives (for tracing past changes in continental weathering) requires a careful examination of how Li isotopes behave at the modern Earth surface in a variety of contexts. In this presentation, we will discuss (1) how source rock types affect Li isotopes in large river sediments; (2) how isotopes of river dissolved Li can be linked to weathering regimes; and (3) how large river dissolved and particulate Li can be used to probe the dynamics of Earth surface processes.
Biography of the speaker: Dr. Julien Bouchez is a CNRS (National Center for Scientific Research) research scientist working at IPGP since 2013, chairman of the IPGP Research Theme ‘Earth System Science’. He authored and co-authored more than 30 SCI papers (H-index =17) including articles published in Nature, Nature Geosciences and other first-rank journals in Earth Sciences. The research of Dr. Julien Bouchez focuses on the effects of chemical weathering, erosion, and river transport on global biogeochemical cycles, using in particular isotope geochemistry of non-traditional stable isotopes (B, Li, Si, Mg, Sr, Ba…) to study the dynamics of the so-called "Critical Zone". The objects of his studies cover a wide range of spatial scales from weathering profiles to the largest world's riverine systems (including the Amazon, MacKenzie and Ganges-Brahmaputra), through small catchments. He himself developed the analysis of some stable isotopes of alkali-earth metals and alkali metals. Besides, Dr Julien Bouchez developed numerical models to interpret variations of non-traditional stable isotopes in the Critical Zone and relate them to surface processes. During his postdoc at the Helmoltz Center in Postdam, he also contributed to the development of a new approach to calculate denudation and erosion rates using meteoric cosmogenic 10Be.
