Laboratory incubation experiments are useful for deciphering the slag solubilization potential as well as the susceptibility of solids to abiotic and biotic dissolution. Here, the potential release of elements has been examined using fungus Aspergillus niger as biotic agent and sterile medium as abiotic control. As a ubiquitous environmental microorganism, A. niger produces organic acids that enhance acidification and dissolution of metal-bearing phases. Results show that at a pulp density of 10% and after 30 days of incubation, A. niger leached up to 30% of Cu and 57.4% of Zn compared to only 2.5% in the sterile medium. Overall, biotic incubation plays a more important role in the dissolution of amorphous slag, whereas its contribution to crystalline slag dissolution is more complex and strongly dependent on host minerals that accommodate major elements. Fungus enhanced the leaching of major elements by factors up to 2.5–4.2 while metal leaching was increased by factor up to 5.2 relative to abiotic conditions. Regardless of the type of slag, higher element leaching was observed when the biomass fraction was considered, enhancing the element yield by up to 4.1 × 103-fold relative to the dissolved metal fraction in the biotic solution. These findings suggest that fungal bioleaching of Cu metallurgical slags is a promising approach for treating them as secondary resources although further optimization steps are still required.
This niobium–tantalum study was conducted in the Wiśniówka massif (Holy Cross Mts., south-central Poland) hosting Upper Cambrian hydrothermal stratiform pyrite–goethite–hematite–REE mineralization. The distinctly higher Nb and Ta enrichments were found in organic-rich clayey-silty shales (7.52–28.99 and 0.54–1.84 mg/kg) than in interbedded quartzites/quartzitic sandstones (0.10–2.63 and <0.01–0.12 mg/kg). Bulk chemical analysis revealed the highest determination coefficients (R 2) for the following chemical pairs: Nb/Ta–Rb (0.95, 0.95), Nb/Ta–TiO2 (0.93, 0.94), Nb/Ta–V (0.94, 0.95), Nb/Ta–K (0.93, 0.93), and Nb/Ta–Al2O3 (0.91, 0.92) pointing to the substitution of these two elements for titanium in the TiO2 polymorph crystal structure and partly to their adsorption on clay minerals and organic matter (distinct affinity to vanadium). The relationship of Nb and Ta to TiO2 mineral phases was confirmed by electron microprobe analysis exhibiting mean contents of Nb (0.18 wt%) and Ta (0.02 wt%). The Nb/Ta ratio shows a narrow dispersion of values (∼16.0) for carbonaceous clayey-silty shales, tuffites/bentonites, and pyrite FeS2 regardless of Nb concentrations, representing intermediate values between the upper continental crust (∼13.3) and the Earth’s mantle (∼17.5). This narrow Nb/Ta ratio may also suggest lower fractionation of both metals in hydrothermally-affected sediments.
Chevkinite-group minerals are rare earth element (REE) carriers in alkaline magmatic and metasomatic systems, yet their hydrothermal stability and alteration pathways remain poorly constrained. We experimentally investigated the hydrothermal transformation of chevkinite (Cvk)-(Ce) under conditions relevant to alkaline rock environments, with particular emphasis on the formation and composition of secondary monazite (Mnz)-(Ce). Twenty-four cold-seal autoclave experiments were conducted at 500–600°C and 200–400 MPa for durations of 21–63 days, using natural Cvk-(Ce) from the Diamer district (Pakistan) together with quartz, albite, and variable accessory components, and reacting them with F- and Ca-bearing aqueous fluids. Mnz-(Ce) crystallized in 200 MPa in six experiments, typically as microcrystalline aggregates (<20 µm) surrounding or replacing primary Cvk. The main associated phases were britholite-(Ce) and titanite. Electron backscattered diffraction confirmed full crystallinity, while electron probe microanalysis) showed that all products are compositionally homogeneous Mnz-(Ce) with dominant phosphate components (∼97.7 wt%), minor silicate substitution (∼2.3 wt%), and no significant REE fractionation relative to the precursor Cvk. Experimental results indicate that Mnz-(Ce) formation is promoted by F- and P-rich fluids and inhibited by high Ca, Fe, and Al activities, which instead favour epidote-supergroup minerals and britholite. Systems with low Ca preferentially stabilized Mnz-(Ce) and albite. These experiments demonstrate that Mnz-(Ce) can form readily during hydrothermal alteration of Cvk -(Ce) under closed-system conditions, providing new constraints on REE mobility, mineral stability, and metasomatic processes in alkaline geological environments.
Petrological observations and major elements analyses in olivine crystals in small xenoliths (>1.5 cm in diameter) from the Jeziorna locality, SW Poland, are presented. The olivines show very large variations in the composition of Mg, Fe, Ca and Ni, which suggests the influence of many possible factors, such as (1) regional variability of the samples; (2) changes in temperature during movement and storage of Cenozoic magmas; (3) weathering; and (4) the interaction of basaltic magma with xenoliths in the mantle or during magma ascent. The latter processes are the final changes recorded in the olivine composition. This study contributes to our understanding of which of the changes in chemical composition can be attributed to these final changes, whether they occur only at the xenolith–host rock contact, or whether they also change the olivine composition inside the xenolith.
Lamprophyre Clan Rocks (LCRs) such as lamprophyres, lamproites and kimberlites are reported from many parts of the cratonic areas in India, especially the diamondiferous Eastern Dharwar Craton (EDC). Although the most common hosts of diamonds are kimberlites and lamproites, different types of lamprophyres elsewhere in the world are also reported to contain diamonds. Owing to the fact that the lamprophyres and kimberlites in the Wajrakarur Kimberlite Field (WKF) are cogengetic, this study attempts for the first time to validate the diamond potentiality of WKF lamprophyres situated at Korrakodu, Kadiri, Kalagalla, Udiripikonda, Sivarampet, Khaderpet, Lattavaram (P-8) and Mudigubba using geochemical data. The geochemical plots of selected cationic wt.% for major oxides and trace elements show that Khaderpet and Lattavaram aillikites (ultramafic lamprophyres) are diamondiferous, with plausible chances of diamond incidences in the Kadiri and Mudigubba calc-alkaline lamprophyres. The trace-element plot of Ta and Sc also shows that the Khaderpet and Lattavaram lamprophyres are diamondiferous. The geochemical data reveal that diamond grade (DG) values are inversely proportional to TiO2 content. It is also observed that the WKF lamprophyres contain some of the diamond indicator minerals. This study shows that the ultramafic lamprophyres of Khaderpet and Lattavaram, have DG values of Kadiri and Mudigubba lamprophyres showing DG values of 5.42 and 7.32 respectively and warrant detailed investigation. The higher DG values for Khaderpet (6.73) and Lattavaram (3.84) are consistent with exploration results. To date, no drilling has been conducted on the WKF lamprophyres except Khaderpet and Lattavaram; all the other lamprophyre outcrops are amenable for further exploration and drilling to ascertain their diamond potential and enhance understanding of the mantle systematics of this region.
