Gabriella Lucchetti

Genetic evolution of nanocrystalline Fe oxide and oxyhydroxide assemblages from the Libiola mine (eastern Liguria, Italy) structural and microstructural investigations

The Libiola Fe-Cu-sulphide mine, near Sestri Levante (eastern Liguria), represents one of the most extensively exploited sulphide deposits in Italy. In this area, active Acid Rock Drainage (ARD) processes are evident. The major resulting mineral phases are Fe oxides and oxyhydroxides, occurring in varicoloured crusts on the surface of waste rocks and in unconsolidated muds. In this study, the Fe assemblages of the waste rock were investigated by microchemical (SEM), structural (XRD), microstructural (TEM) and spectroscopic (DRS, IR, μ-Raman) techniques, in order to determine the phase composition, the textural relations among the minerals and their genetic evolution. They are characterized by intimate intergrowths of hematite and goethite with minor quartz and lepidocrocite; in some samples, the presence of very minor schwertmannite was detected. TEM and HR-TEM observations revealed that hematite is present within pseudo-elliptical bodies as pseudo-hexagonal to subrounded nanocrystalline lamellae (from 18.9 to 26.5 nm in diameter), whereas goethite occurs either as parallel intergrowths of acicular crystals (from 10 to 16.3 μm in length) or as sheaf-like assemblages. On the basis of the present data, the studied Fe oxide and oxyhydroxide assemblages are found to represent distinct spatial and temporal stages of a nano-scale evolution process.

Microfungi in highly copper-contaminated soils from an abandoned Fe-Cu sulphide mine: growth responses, tolerance and bioaccumulation.

Copper is one of the most dangerous soil contaminants. Soils affected by high copper concentrations show low biodiversity and, above all, inadequate environmental quality. Microorganisms such as fungi can play a key role in metal-polluted ecosystems via colonization and decontamination. The study is devoted to characterize the microfungal community in highly Cu-contaminated bare soil from derelict Fe-Cu sulphide mines and to isolate microfungal strains able to tolerate and accumulate Cu. 11 Different taxa to be isolated has been isolated during two sampling campaigns (in Autumn and in Spring). Among these, Clonostachys rosea, Trichoderma harzianum, and Aspergillus alliaceus were tested at increasing Cu(II) concentrations and showed a Cu(II)-tolerance capability ranging from 100 to 400 mg L(-1). Moreover, the strains of T. harzianum and C. rosea presented a high Cu(II)-bioaccumulation capability, 19628 and 22,222 mg kg(-1), respectively. These microfungi may be fruitfully exploited in mycoremediation protocols.

Clay mineral mixtures as alteration products in pillow basalts from the eastern flank of Juan de Fuca Ridge: a TEM-AEM study

Abstract Transmission electron microscope-analytical electron microscope analyses have been carried out on secondary minerals from pillow basalts with various degrees of alteration from the Juan de Fuca Ridge (ODP Leg 168). The electron microscopic data indicate that the alteration products consist mainly of phyllosilicate mixtures. The least altered sample shows poorly crystalline phyllosilicates occurrring as flakes with 10 Å-spaced lattice fringes. They have compositions of celadonite mixed with smectite and/or Fe oxyhydroxides and Mg-rich smectite. Proceeding towards older, more altered basalts, the alteration products consist of: (1) poorly crystalline celadonite mixtures and Mg-rich smectite; and (2) phyllosilicates with a higher degree of crystallinity, showing lattice fringes with 9.1 Å-spacing and with a talc-like composition. Changes in phyllosilicate association occur as the type of alteration changes from an oxidizing, water-dominated system (occurrence of celadonite mixtures with Fe hydroxides) to a reducing, rock-dominated system (occurrence of Fe-smectite and talc-like mixtures).

Reppiaite, Mn5(OH)4(VO4)2, a new mineral from Val Graveglia (Northern Apennines, Italy)

Reppiaite occurs in manganese ores at the Gambatesa Mine, near Reppia village (Val Graveglia, Italy), mainly associated with a Mn-sheet silicate and Mn — Ca-carbonates. It was found in small amounts of very minute tabular crystals, (100) flattened, grown in fracture. Reppiaite, with ideal formula Mn5(0H)4(V04)2, crystallizes in C2/m space group with a = 9.604(2) k,b = 9.558(2) Ä, c = 5.393(1) Ä and β = 98.45(1)°. The strongest lines in the X-ray powder pattern are = 2.68 Ä and d2oo — 4.76 Ä. It is orange-red in colour, transparent, biaxial negative with 2 V large and slightly pleochroic. Microprobe analyses reveal a partial As substitution for V, leading to the empirical formula Mns.oi tOH^.^KV! 65As0.35)O8.02]· The crystal structure of reppiaite is constructed of a quasi cubic close-packing of oxygens and hydroxyl groups, whose layers are stacked parallel to (100). The structure, refined to Λ = 0.038, consists of Mn octahedral layers bound together by isolated (V,As) tetrahedra and hydrogen bonds. Among the minerals, whose chem.cal formula has the same atomic proportions of reppiaite, only cornubits shows very similar structural features.

Application of synchrotron radiation-based techniques (μ-XRD, μ-XRF, and μ-XANES) to study Fe-rich hardpans within waste-rock dump

Recently, several techniques based on synchrotron radiation have been applied to environmental sciences giving the possibility for non-destructive investigations with micrometer spatial resolution. In particular, a combination of synchrotron methods (μ-XRF, μ-XRD, and μ-XAS) have been undertaken to investigate the metals speciation in mine wastes and soils. With this work, after a review on the mineralogical aspects of sulphide-rich waste-rock deposits and the application of synchrotron- based techniques for their characterization, we present a combined synchrotron-based μ-XRD, μ-XRF, and μ-XANES study to determine the mineralogy and the elemental distribution of metals in partially altered sulphide-mineralization fragments deposited within an open-air waste-rock dump (Libiola mine, eastern Liguria, Italy). The selected samples are composed of heterogeneous assemblages of Fe-bearing precipitates formed as a consequence of Fe-Cu sulphide alteration processes that occur within the main waste rock dump of the mining area. The results evidenced that the authigenic iron-rich phases generally contain signifi cant amounts of hazardous elements such as Cu, Zn, Mo, As, and Se. Moreover, a signifi cant mineralogical control on the mobility of these elements have been observed; in particular, the goethite-rich assemblages show high affi nity for Cu and Zn, whereas hematite-rich assemblages selectively concentrate As, Se, Mo, Cu and Zn.

Structural studies on synthetic and natural Fe-Sb-oxides of MO2 type

Structural refinements were performed on synthetic and natural Fe-Sb-oxides of MO 2 type according to the Rietveld method. The refinement in the P4 2 / mnm space group confirms that the synthetic phase (Fe 3 + Sb 5 + )O 4 , corresponding to squawcreekite, is characterised by a rutile-type structure. In contrast to the compositional and structural data (ideally Fe 2 + Sb 5 + 2O 6 with a trirutile-type structure) implicitly accepted by the IMA Commission on New Minerals and Mineral Names, also tripuhyite seems to crystallize with a rutile-type structure in the P4 2 /mnm space group and its composition is based on an equimolar ratio between Fe and Sb.

Isothermal-isobaric mineral equilibria in braunite-, rhodonite-, johannsenite-, calcite-bearing assemblages from Northern Apennine metacherts (Italy)

Abstract Johannsenite coexisting with rhodonite (mol% CaSiO 3 up to 24–25) and calcite (mol% MnCO 3 up to 4) occurs in veins and fracture fillings in braunite (+quartz±hematite) deposits within metacherts at Gambatesa Mine, Val Graveglia, Italy. Primary sedimentary Mn-oxide and hydroxide ores re-equilibrated to braunite+quartz layers and developed Mn-silicate and carbonate assemblages during folding and CaCO 2 metasomatism under prehnite-pumpellyite facies metamorphic conditions. The observed braunite-, rhodonite-, johannsenite- and calcite-bearing assemblages equilibrated at constant P and T as a result of progressive infiltration of Ca-rich, CO 2 − -bearing, relatively reducing hydrous fluids. The observed paragenetic equilibria are discussed in a μO 2 μCO 2 isothermal-isobaric diagram.

Mineralogical and chemical variations of ochreous precipitates from acid sulphate waters (asw) at the Roşia Montană gold mine (Romania)

The mineralogical and chemical variations of ochreous precipitates forming from acid sulphate waters discharged from the lowest mine adit (“Sf. Cruci din Orlea”) of the Roşia Montană Gold Mine (Romania) were investigated by a multianalytical approach (XRPD, IR, TEM, ICP) applied to surface precipitates and associated waters. The mineralogy of the precipitates changed significantly as a consequence of the variations in the chemical parameters of the circulating solutions (mainly pH, Eh, and sulphate concentrations) which were mainly controlled by mixing with unpolluted waters of Roşia River. Ochreous precipitates are characterized by high concentrations of potentially toxic elements (PTEs; in particular Cr, Co, Ni, Cu, Zn, As, Cd, and Pb) and consist of a mixture, in variable proportion, of jarosite and schwertmannite, which represent the stable secondary minerals along the investigated transect of Roşia River. Particular regard is given to the ability of authigenic phases to selectively scavenge selected PTEs from contaminated solutions during their genesis and minerogenetic evolution. Furthermore, laboratory kinetic batch experiments on natural heterogeneous samples of ochreous precipitates were carried out to investigate the release processes involving PTEs and to verify the type and the amount of elements that can be temporarily/permanently trapped by the solid phase from the contaminated solutions. The comparative analysis of the precipitates and waters of the Roşia Montană mining area indicated that the role of secondary minerals as “mitigating agents” can be limited because even minor pH–Eh oscillations would cause mineralogical transformations that could lead to trace elements mobilization in the environment.

Mcalpineite from the Gambatesa mine, Italy, and redefinition of the species

Abstract Mcalpineite has been found in the Gambatesa mine (eastern Liguria, Italy). It occurs in a quartz vein mainly as yellowish green earthy crusts consisting of poorly crystallized mcalpineite intergrown with an unidentified Cu-Te phase, as well as quite pure aggregates of well euhedral emerald green crystals (individually reaching up to 50 μm), associated with black fragments of paratellurite (TeO2) and weissite (Cu2-xTe). The chemical formula of this rare mineral, found at the McAlpine mine (typelocality; California, U.S.A.) and at the Centennial Eureka mine (Utah, U.S.A., co-type locality), was originally given Cu3TeO6·H2O. X‑ray powder diffraction and selected-area electron diffraction data of mcalpineite are in good agreement with those of synthetic Cu3TeO6. In addition no evidence for structural OH group was detected by micro-Raman analysis carried out on samples from Gambatesa, Centennial Eureka, and McAlpine (co-type sample) mines. Taking into account structural, topological, and experimental evidence, the crystal structure and chemical composition of mcalpineite must be revised: the mineral crystallizes in the Ia3̄ space group and the correct chemical formula is Cu3TeO6.

Solid state miscibility in the pseudo-binary TiO2—(FeSb)O4 system at 1373 K

Abstract The tetragonal rutile-type (FeSb)O4 compound was synthesized reacting Fe2O3 and Sb2O3 in O2. Solid solubility in the pseudo-binary TiO2—(FeSb)O4 (rutile — tripuhyite) system was investigated annealing powder mixtures characterized by different TiO2/(FeSb)O4 molar ratios in an O2 flux. Complete miscibility was found in the whole compositional range at 1373 K. The crystal structures of (FeSb)O4 and selected terms of the (Ti2xFe1–xSb1–x)O4 solid solution (0 ≤ x ≤ 1) were refined from X-ray powder diffraction data using the Rietveld method. Selective broadening of the X-ray lines was observed and analyzed by means of the Gaussian quadratic plot. Line broadening is probably related to a phase transformation taking place at low temperature, as suggested by the excess molar volume of the solid solution. As a result local chemical inhomogeneity and microstrain in the direction perpendicular to the 00l lattice planes for compositions 0.2 ≤ x ≤ 0.6 are generated.