The Abruzzi bauxite district includes the deposits located on the Campo Felice plateau and those of the Monti d’Ocre, which had been mined in the first part of the 20th century. Bauxite is of the karst type, with textures ranging between oolitic and oolitic-conglomeratic, the latter suggesting a partial reworking of evolved lateritic soils. The high contents of Al₂O₃ and Fe₂O₃ (average values 53.76 and 21.76 wt %, respectively) are associated with the presence of boehmite, hematite, and minor goethite. SiO₂ and TiO₂ have average values of 7.79 and 2.75 wt %, corresponding to the presence of kaolinite, anatase and rutile. Among the minor so-called “bauxitophile” elements V, Co, Ni, Cr and Zr, the most enriched is Cr, with an average value of 0.07 wt %. Nickel has an average value of 210.83 ppm. Vanadium shows an average value of 266.57 ppm, whereas the average Co concentration is 35.89 ppm. The total rare earth elements (REE) concentration in the sampled bauxite sites is variable between ca. 700 and 550 ppm. Among REEs, the most abundant element is Ce, with Ce anomalies commonly associated with authigenic REE-fluoro-carbonates, probably produced after the REEs remobilization from primary detrital minerals and their precipitation in neo-formed phases during the bauxitization process. Scandium and Ga occur in small amounts (57 and 60 ppm, respectively), but geochemical proxies of their remobilization and uptake in neo-formed minerals (Fe- and Al-(hydr)oxides, respectively) have been observed. The mean Eu/Eu* and Al₂O₃/TiO₂ ratios and the Ni-Cr contents of the Abruzzi bauxites suggest that the parent rock of these deposits was a material of acid affinity, likely corresponding to volcanic tephra or eolic loess-type sands.

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 different 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, γ-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.

The Cornubian Batholith (SW England) is an archetypal Variscan rare metal granite with potential for Li-mica mineralization. We present a petrographic, trace element and multivariate statistical study of micas from the Cornubian Batholith granite series and related hydrothermally altered units to assess the role of magmatic vs subsolidus processes and of fluxing elements (F and B) on the Li cycle during the evolution of the system. The mica types are as follows: (1) magmatic, which include Fe-biotite, protolithionite I and phengite-muscovite from the most primitive granites, and zinnwaldite I from more fractionated lithologies; (2) subsolidus, which encompass high-temperature autometasomatic Li-micas and low-temperature hydrothermal muscovite-phengite. Autometasomatic species include protolithionite II, zinnwaldite II and lepidolite, which were observed in the most fractionated and hydrothermally altered units, and occur as replacements of magmatic micas. Low-temperature hydrothermal Li-poor micas formed via alteration of magmatic and autometasomatic micas or as replacement of feldspars, and albeit occur in all studied lithologies they are best represented by the granite facies enriched in metasomatic tourmaline. The evolution of micas follows two major trends underlining a coupling and decoupling between the Li(F) and B fluxes. These include as follows: (1) a Li(F)-progressive trend explaining the formation of protolithionite I and zinnwaldite I, which fractionate Li along with Cs, Nb and Sn during the late-magmatic stages of crystallization, and of zinnwaldite II and lepidolite forming from the re-equilibration of primary micas with high-temperature Li-B-W-Tl-Cs-Mn-W-rich autometasomatic fluids; (2) a Li(F)-retrogressive trend explaining the low-temperature hydrothermal muscovitization, which represents the main Li depletion process. Trace element geochemistry and paragenesis of late muscovite-phengite support that muscovitization is a district-scale process that affected the upper parts of the granite cupolas through acidic and B(Fe-Sn)-saturated hydrothermal fluids associated with metasomatic tourmalinization, which were mixed with a low Eh meteoric component.