HR: 0830h
AN: V51C-0305    [PDF]
TI: Origin of the dissolved U-Sr fluxes in the Himalayan rivers: cases of the Indus, Ganges and Brahmaputra
AU: * Schmitt, A
EM: schmitt@illite.u-strasbg.fr
AF: CGS-EOST, 1 rue Blessig 67000 CGS - EOST, 1, rue Blessig, Strasbourg, 67000 France
AU: Chabaux, F
EM: fchabaux@illite.u-strasbg.fr
AF: CGS-EOST, 1 rue Blessig 67000 CGS - EOST, 1, rue Blessig, Strasbourg, 67000 France
AU: France-Lanord, C
EM: cfl@crpg.cnrs-nancy.fr
AF: CRPG, 15 rue N.D. des pauvres, Vandoeuvre-les, 54501 France
AU: Singh, S
EM: sunil@prl.ernet.in
AF: Chemistry Laboratory Physical Research Laboratory, Navrangpura, Ahmedabad, 380009 India
AU: Veizer, J
EM: veizer@science.uottawa.ca
AF: Ottawa-Carleton Geoscience Ottawa-Carleton Geoscience Centre, University of Ottawa, Ottawa, ON KIN 6N5 Canada
AU: Veizer, J
EM: veizer@science.uottawa.ca
AF: Institut f�r Geologie, Mineralogie und Geophysik, Ruhr Universit�t, Bochum, 44780 Germany
AU: Karim, A
EM: karim_a@mercer.edu
AF: EGR 101C Environmental Science Dept Mercer university Mercer University, 1400 Coleman Avenue, Macon, GE 31207-0001 United States
AB: The rivers draining the Himalaya are recognised as major contributors to the dissolved riverine flux to the oceans, with a non-negligible effect on the global budget of elements such as Sr and U. The precise characterisation of the different sources contributing to these fluxes is important and has to be done to model correctly the Himalayan river chemical flux variations through time, in response to climatic or tectonic variations and to better constrain the impact of these rivers on the U and Sr oceanic budget. The recent study of the Ganges watershed has shown the potential of the U-Sr combined isotopic analyses to reach this objective (Chabaux et al., 2001). We propose to extend this approach for the two other main Himalayan rivers: the Brahmaputra and the Indus. Our results show that the U and Sr fluxes carried by the Brahmaputra are not only controlled by the Himalayan end-member identified during the study of the Ganges watershed, but also by a chemical flux coming from the Tibetan plateau and another one specific of the plain formations. These two latter fluxes contribute to the U and Sr dissolved budget of the Brahmaputra during the dry season, and at different intensities for these two elements. During the monsoon, their impact seems to be negligible compared to the flux coming from the Himalayan chain. As a first approximation therefore, the annual hydrological cycle of the Brahmaputra river would have a U-Sr systematics very close to that of the Ganges river. By contrast, for the Indus River, in addition to the Himalyan flux, U and Sr dissolved budget is significantly affected by chemical fluxes from the Tibetan plateau, the plain and also from the West Pakistan Fold belt. The input of the Punjab river, the main Indus tributary that strongly influences the U-Sr budgets, on the Indus can be explained in terms of mixing between the Himalayan and the plain end members. These results will be used to constrain the response of U and Sr fluxes of the Himalayan river system to climatic variations and to discuss the impact of these variations on U and Sr oceanic budgets. Chabaux F., Riotte J., Clauer N. and France-Lanord C. (2001) GCA 65(19), 3201-3217
DE: 1030 Geochemical cycles (0330)
DE: 1040 Isotopic composition/chemistry
DE: 1806 Chemistry of fresh water
DE: 1815 Erosion and sedimentation
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting