Article Dans Une Revue Geochimica et Cosmochimica Acta Année : 2026

Lithium Isotopic Composition of Fluid Inclusions provides insights into Fluid–Rock Interaction in Subducted Sediments and Sources of Mud Volcano Fluids

Résumé

Lithium isotopes have been widely used to investigate fluid-mediated processes in subduction.

However, direct analysis of pore fluids in metamorphic rocks remains challenging due to prohibitive depths at which these processes occur. To evaluate the potential of Li concentration and isotopic composition recorded in fluid inclusions, we employed a crush-leach technique to +9.5‰), and Shimanto (+2.5‰ to +10.4‰) is primarily governed by the presence of Li-bearing mineral phases during vein formation-particularly chlorite, white mica, and paragonite-and their capacity to retain lithium. In closed systems, δ 7 Li values of pore fluids can be explained by Rayleigh fractionation during the crystallization of chlorite, illite/phengite, and paragonite, which dominantly incorporate 6 Li, leaving the fluids enriched in 7 Li and therefore having heavier δ 7 Li values. Conversely, in open systems, continuous Li removal from the rocks results in decreasing δ 7 Li values of pore fluids, though their Li concentrations remain comparable to those in closed systems. Similarities in Li concentrations and δ 7 Li values between leachates and mud volcano fluids in modern examples of subduction zone forearcs further confirm that such fluids dominantly originate from subducted sediments. Collectively, this study demonstrates the capability of Li isotope systematics of fluid inclusions to effectively contribute to the understanding of fluid-rock interactions in subducted lithologies.

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Cite 10.5281/zenodo.18246443 Article Rajič, K. (2026). Supporting Information for the manuscript by Rajič et al. Lithium Isotopic Composition of Fluid Inclusions provides insights into Fluid–Rock Interaction in Subducted Sediments and Sources of Mud Volcano Fluids, accepted for publication in Geochimica et Cosmochimica Acta. Zenodo. https://doi.org/10.5281/ZENODO.18246443

Dates et versions

insu-05483181 , version 1 (29-01-2026)
insu-05483181 , version 2 (16-02-2026)

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Kristijan Rajič, Antonin Richard, Hugues Raimbourg, Tomáš Magna, Clément Herviou, et al.. Lithium Isotopic Composition of Fluid Inclusions provides insights into Fluid–Rock Interaction in Subducted Sediments and Sources of Mud Volcano Fluids. Geochimica et Cosmochimica Acta, 2026, 416, pp.279-293. ⟨10.1016/j.gca.2026.01.026⟩. ⟨insu-05483181v2⟩
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