Pogge von Strandmann, Philip AE;
Cosford, Lara R;
Liu, Chun-Yao;
Liu, Xianyi;
Krause, Alexander J;
Wilson, David J;
He, Xiaoqing;
... Burton, Kevin W; + view all
(2023)
Assessing hydrological controls on the lithium isotope weathering tracer.
Chemical Geology
, 642
, Article 121801. 10.1016/j.chemgeo.2023.121801.
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Abstract
To investigate the impact of riverine discharge and weathering intensity on lithium isotopes (δ7Li) in a mono-lithological terrain, this study examines the dissolved load and leached suspended load (exchangeable, oxide, and clay fractions) from Icelandic rivers spanning a wide range of discharge, weathering rates, and weathering intensity. The δ7Lidissolved co-varies inversely with the discharge, confirming that water-rock interaction time is a primary control on the secondary mineral formation that fractionates Li isotopes. The “boomerang” shape observed in global rivers between the weathering intensity (i.e. W/D = weathering rate/denudation rate) and δ7Lidissolved also exists for these basaltic rivers at low to medium W/D. However, these rivers do not extend to such low δ7Lidissolved values as seen in the global compilation at low W/D, indicating that there is a lithological control on this relationship arising from the type of the lithology-specific secondary minerals forming and their precipitation rates. In addition, the Δ7Lix-dissolved between each leached solid phase and the dissolved load also co-varies with discharge. At low discharge (long water-rock interaction times), Δ7Lix-dissolved values agree with experimentally-determined equilibrium values, whereas less fractionated values are observed at higher discharge (shorter water-rock interaction times). As a result, there is a different relationship between W/D and Δ7Liclay-source in this basaltic terrain than previously reported from global multi-lithological river sediment samples, with clay leachates from Iceland more closely mimicking the boomerang shape of the dissolved load. However, the relationship between δ7Li and weathering processes is complicated because the fractionation between the clay fraction and the dissolved load is not constant but varies with both W/D and discharge. Overall, this study confirms the utility of Li isotopes as a tracer of modern and palaeo-weathering processes, and also has important implications for the specific interpretations of detrital δ7Li values, which may be more sensitive to weathering parameters than previously thought.
| Type: | Article |
|---|---|
| Title: | Assessing hydrological controls on the lithium isotope weathering tracer |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.chemgeo.2023.121801 |
| Publisher version: | https://doi.org/10.1016/j.chemgeo.2023.121801 |
| Language: | English |
| Additional information: | Other analyses and PPvS and AJK were funded by ERC grant 682760 CONTROLPASTCO2. For the purpose of open access, the author has applied a ‘Creative Commons Attribution (CC BY) licence’ to any Author Accepted Manuscript version arising. |
| Keywords: | Silicate weathering, Basalt weathering, Secondary mineral formation, Clay formation, Weathering intensity |
| 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/10180142 |
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