Invited by Prof. CHEN Jiubin of the State Key Laboratory of Environmental Geochemistry (SKLEG), Prof. Jerome Gaillardet，a well-known Geochemist from the Institut de Physique du Globe de Paris (IPGP) and Sorbonne Paris Cite University visited IGCAS.

Prof. Jerome Gaillardet presented a seminar titled “Isotope systematics in the Mackenzie river basin, Northern Canada” on August 24. The seminar was hosted by CAS Academician LIU Congqiang.

Academician LIU Congqiang hosting the seminar	Prof. Jerome Gaillardet at his presentation

In his presentation, Prof. Jerome Gaillardet first emphasized the importance of studying chemical weathering, and then focused on the Mackenzie basin and showed that the chemical weathering rate of the mountains was lower than that of plains. After introducing the detailed properties of the various isotopes in Mackenzie River and the relations amongst those isotopes including Sr, O, Li, B and Mg, he revealed the following results: 1) Sr isotopes were not affected by isotopic fractionation at all, and therefore they could be used to distinguish between carbonate weathering and silicate weathering; 2) the sulfates in Mackenzie river basin were predominantly derived from the oxidation of sulfides, although in the carbonate weathering-dominated basin; 3) the Li, B and Mg isotopic data indicated that those elements were mainly derived from silicate weathering; 4) most importantly, the correlations found between the different isotopic systems were totally out of expectation, e.g. Li isotope ratio showed a negative correlation with B isotope ratio, whereas it showed a positive correlation with Mg isotope ratio. This observation was explained by the fact that B isotope ratio was mainly controled by the water residence time, while the Li isotope ratio was likely to be impacted by secondary mineral formation. At the end of his presentation, Prof. Jerome Gaillardet shared a view of his future studies, followed by a heated discussion with the audience.

During his stay, Prof. Jerome Gaillardet also had thorough discussions with the group members of Prof. FENG Xinbin, Prof. LIU Yun, Prof. LIU Zaihua and Prof. LI Xinqing, respectively.

Professor Jerome Gaillardet received his Ph.D. from University Paris 7 and presently works in IPGP and Sorbonne Paris Cite University. He is a well-known geochemist in the fields of chemical weathering, non-traditional stable isotopes, and global carbon cycle. He currently holds various senior positions including Director of the Laboratoire de Geochimie et Cosmochimie, National Coordinator of the French Network of drainage basins (RBV) and committee member of Sorbonne Paris Cite University.He won the Price Etienne Roth from French Academy of Science in 2002.  He was then honored as Gast Lecturer of European Association of Geochemistry and presented a plenary lecture in Goldschmidt Conference 2008. In addition, He is also the editor of a number of top journals such as GCA and Chemical Geology, and will serve as the General Secretary of GES in 2014.　

(Provided by CAI Hongming, translated by CHEN Jiubin and XIAO Yi)