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Li isotopes in the middle Yellow River: Seasonal variability, sources and fractionation

Gou, L-F; Jin, Z; Pogge Von Strandmann, PAE; Li, G; Qu, Y-X; Xiao, J; Deng, L; (2019) Li isotopes in the middle Yellow River: Seasonal variability, sources and fractionation. Geochimica et Cosmochimica Acta , 248 pp. 88-108. 10.1016/j.gca.2019.01.007. Green open access

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Abstract

To evaluate the roles of climate and hydrology in continental-scale silicate weathering, we applied Li isotopes to the Yellow River and systematically investigated seasonal Li flux, Li isotopic compositions and potential sources. We collected samples from the middle reaches of the Yellow River weekly over the full hydrological year of 2013. We find that the dissolved Li is mainly derived from silicates and evaporites in the arid to semi-arid Yellow River basin. Silicate weathering of loess during the monsoonal season dominates the Li flux in the middle reaches of the Yellow River, with a positive relationship between dissolved Li flux and physical erosion rate. Evaporite contribution for riverine Li was relatively constant in the middle reaches of the Yellow River but slightly increased after the storm event, with an average proportion of ∼25%, which might represent the proportion of evaporite contribution to global oceans. Seasonal variations in the riverine Li isotopic compositions are dominantly controlled by temperature with a fractionation gradient as −0.182‰ per °C over the full year with deviations likely driven by re-dissolution of suspended particulate matter, extreme hydrological events, and groundwater contribution. Temperature dependent δ7Li value variation of river water inputted into oceans indicates that Cenozoic climate cooling itself may be able to explain ∼2‰ of the 9‰ rise of Cenozoic seawater δ7Li value (Misra and Froelich, 2012). The seasonal variation in riverine Li isotopes highlights that erosion and weathering of loess may provide valuable clues on secular chemical weathering and seawater δ7Li variation spanning a range of time scales.

Type: Article
Title: Li isotopes in the middle Yellow River: Seasonal variability, sources and fractionation
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.gca.2019.01.007
Publisher version: https://doi.org/10.1016/j.gca.2019.01.007
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Li isotopes, Temperature dependency, Seasonal variation, Loess weathering, The Yellow River, The Chinese Loess Plateau
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10066836
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