GEOCHEMISTRY OF SURFACE WATERS AROUND FOUR HARD-ROCK LITHIUM DEPOSITS IN CENTRAL EUROPE

Hard-rock lithium (Li) deposits are becoming more important as they are much more geographically abundant compared to Li brines [1]. The European Union, for example, aims to create a vertically integrated supply chain consisting of mining of the Li ores through processing and electric vehicle assembly all within the continent [2]. Europe contains multiple interesting Li hard-rock deposits, consisting of spodumene pegmatites and Li-mica granites. The largest Li hard-rock deposit in Europe is Cínovec [3] on the border of Czech Republic (CZE) and Germany (GER). Little is known about aqueous geochemistry near such Li deposits [1]. Lithium is used in medicine to treat bipolar disorder but is known to cause serious side effects (e.g., renal failure, dizziness, poor memory [4]). The EPA recommends a Li limit for drinking water of 0.7 ppm [5]. Li-micas are typically also rich in fluorine (F). Fluoride in drinking water is one of ten elements of concern identified by the WHO, and is known to cause fluorosis above 1.5 ppm [6].

This study examined three Li-mica and one spodumene deposits in CZE, GER, and Austria, including the Cínovec deposit. A total of 47 surface water samples were collected to analyze whether Li and/or F leaches into the waterways near such deposits in elevated amounts. In the Cínovec and Homolka (CZE) deposits, several water samples are enriched (max of 36 ppb) relative to typical Li concentrations (≤ 20 ppb [7]) in surface waters, but they do not surpass the EPA-recommended threshold. Three of the ten samples from the Cínovec deposit are above the WHO 1.5 ppm drinking water limit for F (max of 3.8 ppm) and may pose a public health risk. Geochemical inverse modeling as well as saturation-index calculations, both done in PHREEQC, suggest that the Li is derived from zinnwaldite (a Li-mica present in local rocks), F from a combination of zinnwaldite and fluorite, and that Li is scrubbed by clays from the waterways, offering a natural remediation strategy.

[1] Bradley et al., (2017) USGS Report 2010-5070-0. [2] Lebedeva et al., (2017) EC Report JRC105010. [3] Gourcerol et al., (2019) Ore Geol. Rev.109, 494-519. [4] Mayo Clinic (accessed 1/2021) Lithium (Oral Route) [5] Tripathi, (2011) Virginia Department of Health, access. 1/2021. [6] WHO, (1999) Geneva, Switzerland, access. 1/2021. [7] Kavanagh et al., (2018) Resources 7, 57, 1-29.