Special Issue "Bauxite Deposits"

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: closed (31 May 2018).

Special Issue Editor

Prof. Dr. Giacomo Oggiano
E-Mail Website
Guest Editor
Department of Nature and Land Sciences, Universita degli Studi di Sassari, Sassari, Italy
Interests: structural control and geodynamic setting of ore deposits

Special Issue Information

Dear Colleagues,

Bauxite is a chemical sediment that, in addition to being the principal ore of aluminium, is largely employed in several productions, such as alumina, cement, refractories, absorbent, proppant, REE sources, etc. New uses can be proposed day-by-day—including its byproduct in a circular economy—and this helps keep its market value high.

For geologists dealing with geodynamics, bauxite and laterite are effective palaeoclimatic, palaeogeographic and palaeoenvironmental proxies indicative, not only of general tropical latitudes and moosonal climate, but also of local uplift rate and drainage conditions.

Several high field strength elements accumulate in bauxite, such as gallium, REE, and titanium, which can be profitably recovered avoiding environmental issues. It is not surprising that, not only econimic geologists, but also geochemists and geologists dealing with paleogeography are increasingly involved in research concerning bauxite.

Prof. Dr. Giacomo Oggiano
Guest Editor

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Keywords

  • wheathering
  • palaeoclimate
  • alumina
  • REE
  • aluminium

Published Papers (3 papers)

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Research

Open AccessArticle
Mineralogical and Geochemical Features of Cretaceous Bauxite from San Giovanni Rotondo (Apulia, Southern Italy): A Provenance Tool
Minerals 2018, 8(12), 567; https://doi.org/10.3390/min8120567 - 04 Dec 2018
Abstract
In this study, the mineralogical and chemical compositions of bauxite from San Giovanni Rotondo (SGR) on the Gargano Promontory (northern Apulia, Italy) are presented and discussed with the aim of assessing the nature of its source material. Bauxite from the SGR, which is [...] Read more.
In this study, the mineralogical and chemical compositions of bauxite from San Giovanni Rotondo (SGR) on the Gargano Promontory (northern Apulia, Italy) are presented and discussed with the aim of assessing the nature of its source material. Bauxite from the SGR, which is known as the “Montecatini mine”, was exploited intensively until the 1970s to recover alumina. As with most of the autochthonous peri-Mediterranean bauxites, the studied deposit is a karst bauxite with a massive, matrix-supported texture and an oolitic structure. Boehmite and hematite are the main mineral phases, and anatase, rutile, and kaolinite are present in lesser amounts along with detrital zircons and monazite grains. Calcite is abundant only in the deposit’s lower portion, triggering a significant dilution effect on trace element concentrations. However, with respect to the average crust and chondrite compositions, strong enrichments of trace metals (up to 10X Upper Continental Crust’s (UCC)) and rare earth elements (REEs, up to 800X chondrite) exist throughout the studied deposit. The distribution of REEs, the (La/Yb)N and Eu/Eu* ratios, and an Eu/Eu* versus Sm/Nd diagram have been used for determining the bauxite’s provenance. These geochemical proxies point to a parental material consisting of a mixture of distant magmatic and siliciclastic components. Full article
(This article belongs to the Special Issue Bauxite Deposits)
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Open AccessArticle
Geochemical Characterization of Bauxite Deposits from the Abruzzi Mining District (Italy)
Minerals 2018, 8(7), 298; https://doi.org/10.3390/min8070298 - 12 Jul 2018
Cited by 8
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Bauxite Deposits)
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Open AccessArticle
Rare Earth Element Phases in Bauxite Residue
Minerals 2018, 8(2), 77; https://doi.org/10.3390/min8020077 - 24 Feb 2018
Cited by 11
Abstract
The purpose of present work was to provide mineralogical insight into the rare earth element (REE) phases in bauxite residue to improve REE recovering technologies. Experimental work was performed by electron probe microanalysis with energy dispersive as well as wavelength dispersive spectroscopy and [...] Read more.
The purpose of present work was to provide mineralogical insight into the rare earth element (REE) phases in bauxite residue to improve REE recovering technologies. Experimental work was performed by electron probe microanalysis with energy dispersive as well as wavelength dispersive spectroscopy and transmission electron microscopy. REEs are found as discrete mineral particles in bauxite residue. Their sizes range from <1 μm to about 40 μm. In bauxite residue, the most abundant REE bearing phases are light REE (LREE) ferrotitanates that form a solid solution between the phases with major compositions (REE,Ca,Na)(Ti,Fe)O3 and (Ca,Na)(Ti,Fe)O3. These are secondary phases formed during the Bayer process by an in-situ transformation of the precursor bauxite LREE phases. Compared to natural systems, the indicated solid solution resembles loparite-perovskite series. LREE particles often have a calcium ferrotitanate shell surrounding them that probably hinders their solubility. Minor amount of LREE carbonate and phosphate minerals as well as manganese-associated LREE phases are also present in bauxite residue. Heavy REEs occur in the same form as in bauxites, namely as yttrium phosphates. These results show that the Bayer process has an impact on the initial REE mineralogy contained in bauxite. Bauxite residue as well as selected bauxites are potentially good sources of REEs. Full article
(This article belongs to the Special Issue Bauxite Deposits)
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