FluidNET Science Conference Abstract - Potential lithium enrichment above migmatite terrains
Creators: name: Leo Kriegsman
name: Elisa Oliveira da Costa
name: Barbara E. Kunz
name: Dörte Jordan
Publisher: name: Zenodo
Year: 2024

description: Potential lithium enrichment above migmatite terrains

 

Kriegsman L.M.1,2*, da Costa, E.O.3, Kunz, B.E.3 and Jordan D.A.A.1,2

1 Dept. of Research & Education, Naturalis Biodiversity Center, Darwinweg 2, 2333 CR, Leiden, Netherlands

2 Faculty of Geosciences, University of Utrecht, Heidelberglaan 8, 3584 CS, Utrecht, Netherlands

3  School of Environment, Earth and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, United Kingdom

* corresponding author: leo.kriegsman@naturalis.nl

 

Partial melting is a key factor in the transfer of many critical metals from the deep continental crust to mid-crustal levels via granitoids. The transition zone between these crustal levels is characterized by migmatite-rich domains that record melt production, melt loss and melt crystallization. Migmatites are also affected by melt influx from deeper levels, and they release massive amounts of fluid during cooling. Such fluids invade and modify adjacent metasedimentary units - as will be highlighted by an example from the Pyrenees -, but are also partly transferred to shallower levels, potentially carrying elements like lithium, the key commodity on which we focus in this work.

 

Several processes may act in tandem to enrich Li concentrations by a factor of up to ~100: protolith enrichment, partial melting, and fractional crystallization [1]. At a late stage of the latter process, supercritical fluids unmix from the last silicate melt and may transfer up to 50% of the available Li [calculated after 2]. Where the fluids invade overlying medium-grade domains, the commonly observed retrogression of cordierite and biotite may enrich the fluids even further in Li [3]. This may eventually lead to epigenetic Li enrichment, and deposits, without the need for directly underlying granite intrusions, although granites are likely to co-exist in migmatite terrains and overlying medium- to high-temperature metamorphic domains at low to medium pressures [4].

 

An even more exciting scenario is when the Li-enriched fluids infiltrate closed basins that are forming evaporites, such as the Permian Zechstein deposits. In that case, salar deposits like those in Bolivia and Chile are possible. In conclusion, we believe that the late-Hercynian period in Europe with its large-scale mid-crustal melting and its extensive overlying salt deposits may harbour significant Li deposits that may help Europe to develop sustainable mining on its own territory. This could be the focus for a follow-up programme after FluidNET.

 

References:

[1] da Costa E.O., Kriegsman L.M., Kunz B.E., Warren C.J. and Argles T.W. Submitted to Geology.

[2] Yuan Y., Chen B., Shang L., Sendula E. and Chou I.-M., 2023. Ore Geology Reviews 162: 105685

[3] da Costa, E.O., Warren C.J., Kunz B.E., Kriegsman L.M. and Argles T.W. Metamorphic Studies Group - Research in Progress meeting, University of Oxford, 4-5 April, 2023. Programme & abstracts, p. 20.

[4] Pesquera A., Roda‑Robles E., Gil‑Crespo P.P., Valls D. & Torres Ruiz J., 2020. Nature Sci. Rep. 10: 10828.

 

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 956127