Rare Earth Elements (REE) in Al- and Fe-(Oxy)-Hydroxides in Bauxites of Provence and Languedoc (Southern France): Implications for the Potential Recovery of REEs as By-Products of Bauxite Mining

Bauxites in southern France (Provence and Languedoc) have been exploited since the
beginning of the last century. Though most of the deposits are now subeconomic or mined-out,
these bauxites represent model analogs for other economic bauxites of the world. These Cretaceous
karst-type deposits lie directly on Jurassic carbonates, and have been formed through a combination
of di erent processes: in-situ alteration of siliciclastic sediments deposited on carbonate platforms,
and reworking of early bauxites in the karst network. In this study, we present preliminary bulk
rock geochemical and in-situ laser ablation (LA) -ICP-MS analyses on Al- and Fe-oxy-hydroxides of
Provence (Les Baux-de-Provence) and Languedoc (Villeveyrac, Loupian) bauxites, with the aim of
evaluating the concentrations of rare earth elements (REEs) and their deportment in these minerals.
REEs have total average concentrations of 700 mg/kg in the analyzed samples, which are mostly
composed of boehmite,
-AlO(OH), and Fe-oxy-hydroxides (hematite and goethite). Maximum
REEs concentrations are commonly associated with positive Ce anomalies in chondrite-normalized
patterns. In contrast with other examples from the literature, it has been observed that high REE
concentrations also occur in samples apparently devoid or poor of REE-minerals. In these samples,
the total amount of REEs is positively correlated with that of Ga (commonly contained in boehmite).
LA-ICP-MS trace element analyses on boehmite and Fe-oxy-hydroxides have shown that while the
Al-hydroxide contains the suite of REEs, goethite and hematite are preferentially enriched only in
Ce. Considering that Al-hydroxides are digested during the Bayer process, an interesting issue to
develop in the future is whether (and how) REEs released during Al-hydroxide digestion could be
recovered together with Al from the pregnant leach liquor, as routinely done for Ga.