Branson, O and Uchikawa, J and Bohlin, MS and Misra, S (2024) Controls on Li partitioning and isotopic fractionation in inorganic calcite. In: Geochimica et Cosmochimica Acta, 382 . pp. 91-102.
|
PDF
Geo_Cos_Act_Vol_382_Oct_2024.pdf - Published Version Download (1MB) | Preview |
|
|
PDF
geo_cos_act_382_2024.pdf - Published Supplemental Material Download (751kB) | Preview |
Abstract
The δ7Li of marine carbonates has been interpreted as an archive of the evolution of seawater δ7Li, and therefore continental weathering, through geological time. However, little is known about the incorporation of Li into calcium carbonate minerals and, consequently, the controls on Li partitioning (DLi) and isotopic fractionation (�7Lisolid-fluid) associated with Li incorporation. Crucially, we lack a fundamental understanding of how Li partitioning and �7Lisolid-fluid change in response to the chemical and physical conditions of crystal formation. Here, we present DLi and �7Lisolid-fluid data from a series of inorganic calcite precipitation experiments where temperature, and solution pH and dissolved inorganic carbon (DIC) were independently varied. We find DLi values in the range 0.8�1.5 � 10�3, which show no relationship with temperature, a strong positive correlation with pH, and a weak positive correlation with DIC. At face value, these patterns are inconsistent with the results of previous precipitation studies. However, the correlations with pH and DIC are consistent with a strong precipitation rate control on DLi that aligns well with previous data, with a likely secondary influence from the incorporation of Li-HCO30 ion pairs from solution. We find �7Lisolid-fluid values in the range �6 to �2 �, which show no relationship with temperature or pH, and a weak positive correlation with DIC and crystal precipitation rate. These results do not agree with previously published data. Considered alongside previously published data, we observe no consistent relationship between �7Lisolid-fluid and any reported physical or chemical experimental parameter, highlighting the need for substantial further work to determine whether systematic controls on Li isotopic fractionation exist in carbonate minerals, and whether they may be environmentally significant. © 2024 The Authors
| Item Type: | Journal Article |
|---|---|
| Publication: | Geochimica et Cosmochimica Acta |
| Publisher: | Elsevier Ltd |
| Additional Information: | The copyright for this article belongs to authors. |
| Department/Centre: | Division of Mechanical Sciences > Centre for Earth Sciences |
| Date Deposited: | 22 Sep 2024 09:38 |
| Last Modified: | 22 Sep 2024 09:38 |
| URI: | http://eprints.iisc.ac.in/id/eprint/86257 |
Actions (login required)
 |
View Item |
