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Dr. Bernard Bourdon
Laboratoire de Géologie de Lyon (France)
Bernard Bourdon is a geochemist and cosmochemist at the Ecole Normale Supérieure in Lyon and he has been investigating the formation and early evolution of the Earth and planets using isotope tools. A significant part of his research activity has focused on the development of U-series nuclides for geochemical applications. After a PhD at Columbia University (Lamont-Doherty Earth Observatory), he was a professor at the Institut de Physique du Globe in Paris and at the ETH Zurich before moving to Lyon. He was a co-convener of the Goldschmidt 2011 in Prague and currently serves as the president of the European Association of Geochemistry. He was an Editor-in-Chief for Chemical Geology and he is now a member of the Board of Reviewing Editors for Science.
Models for the formation and composition of the Earth usually focus on specific characteristics of its chemical or isotope composition and use chondritic meteorites as the main building blocks. In this context, carbonaceous chondrites, notably the CI chondrites give the best match for refractory lithophile element in the Earth’s mantle and are often used as a starting material. In contrast, the enstatite chondrites show an almost perfect match with many isotope systems, including oxygen, chromium, nickel and titanium. There are several processes that can modify the composition of the planetary materials that have formed the Earth, including thermal processing leading to volatile depletion (partial condensation or evaporation), grain sorting, impact-driven processes or metal segregation. In this presentation, I will examine the possible role of these processes in light of our recent isotope observations with a focus on isotopes and show how the processing of various chondritic materials is required to explain the composition of the Earth.