Experimental constraints on Li isotope fractionation during the interaction between kaolinite and seawater

In this study, to better understand the factors controlling concentration and isotope composition of lithium (Li) in ocean, we investigated behaviour Li during interaction kaolinite with artificial seawater. Dissolution Li-free seawater at acidic conditions (exp. 1) results a strong preferential release light isotopes, ?7Liaq-kaol ? ?19‰, likely reflecting both breaking 6LiO bonds over 7LiO from isotopically lighter AlO6 octahedral sites. Sorption experiments on 2) revealed partition coefficient between fluid up 28, an isotopic fractionation ?24‰. Thermodynamic calculation indicates authigenic smectites formed dissolution pH 8.4 3). The formation phase strongly removed solution (with solid equal 89) led increase ca. 25‰ ?7Li. This can be described by Rayleigh model early stage experiment rapid clay precipitation, followed, longer reaction time, equilibrium much slower removal aqueous via co-precipitation adsorption. Both processes are consistent factor ??20‰. These have implications for interpreting continental marine waters. For instance, 6Li observed far-from-equilibrium could explain transient enrichments soil profiles. With regard evolution ?7Li geological time scales, our experimental suggest that detrital material discharged rivers ocean ensuing “reverse chemical weathering” potential impact signature through neoformation minerals.