Riverine dissolved lithium isotopic signatures in low-relief central Africa and their link to weathering regimes

Henchiri, Soufian; Gaillardet, Jérôme; Dellinger, Mathieu; Bouchez, Julien; Spencer, Robert G.M.

doi:10.1002/2016gl067711

Riverine dissolved lithium isotopic signatures in low-relief central Africa and their link to weathering regimes

Henchiri, Soufian; Gaillardet, Jérôme; Dellinger, Mathieu; Bouchez, Julien; Spencer, Robert G.M.

Authors

Soufian Henchiri

Jérôme Gaillardet

Mathieu Dellinger

Julien Bouchez

Robert G.M. Spencer

Abstract

The isotopic composition of dissolved lithium (δ7Li) near the Congo River mouth varied from 14‰ to 22‰ in 2010 and was negatively correlated to discharge. From the relationship between dissolved δ7Li and strontium isotopes, we suggest that this large variation is due to mixing of waters from two contrasting continental weathering regimes. One end-member (high δ7Li ≈ 25‰) represents waters sourced from active lateritic soils covering the periphery of the basin (Li highly sequestered into secondary mineral products) and another representing blackwater rivers (low δ7Li ≈ 5.7‰) derived from the swampy central depression where high organic matter content in water leads to congruent dissolution of the Tertiary sedimentary bedrock. This suggests that the lithium isotopic signature of tropical low-relief surfaces is not unique and traces the long-term, large-scale vertical motions of the continental crust that control geomorphological settings. This evolution should be recorded in the oceanic secular δ7Li curve.

Citation

Henchiri, S., Gaillardet, J., Dellinger, M., Bouchez, J., & Spencer, R. G. (2016). Riverine dissolved lithium isotopic signatures in low-relief central Africa and their link to weathering regimes. Geophysical Research Letters, 43(9), 4391-4399. https://doi.org/10.1002/2016gl067711

Journal Article Type	Article
Acceptance Date	Mar 18, 2016
Online Publication Date	May 6, 2016
Publication Date	May 16, 2016
Deposit Date	Aug 2, 2017
Publicly Available Date	Oct 13, 2017
Journal	Geophysical Research Letters
Print ISSN	0094-8276
Electronic ISSN	1944-8007
Publisher	Wiley
Peer Reviewed	Peer Reviewed
Volume	43
Issue	9
Pages	4391-4399
DOI	https://doi.org/10.1002/2016gl067711

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Copyright Statement
Henchiri, S., J. Gaillardet, M. Dellinger, J. Bouchez, and R. G. M. Spencer (2016), Riverine dissolved lithium isotopic signatures in low-relief central Africa and their link to weathering regimes, Geophysical Research Letters, 43, 4391-4399, doi:10.1002/2016GL067711. To view the published open abstract, go to https://doi.org/ and enter the DOI.