Mineral Systems Research Articles

Structural Controls on the Origin and Emplacement of Lithium-Bearing Pegmatites

Abstract Exploration and mining of lithium pegmatites has increased in recent years to meet the growing demand for critical metals, which are required for electric-powered transportation as well as sustainable energy production and storage. Pegmatite deposits produced approximately 60% of global lithium production in 2018, the vast majority of which was from spodumene pegmatites. However, there is lack of comprehensive models linking mineral system evolution and structural controls of lithium pegmatites. The majority of studies on lithium pegmatites have focused on chemical fractionation and assume that pegmatites have evolved from a parental granitic source, yet problems emerge when the connection between the granitic source and the pegmatite bodies is not obvious. This lack of connection has given rise to an alternative model of pegmatite formation, the anatectic model. In the anatectic model, granitic pegmatites form from granitic melts produced by partial melting of a suitable lithology, typically pelitic metasediments, without forming a large granitic body followed by fractional crystallization. Here, we first examine the formation of granitic melts related to anatexis, as well as how regional crustal structures influence chemical composition, crustal migration, and melt accumulation within the crust. We next examine the Wekusko Lake pegmatite field located in Manitoba, Canada, in terms of the probable melt source migration, the relationship between crustal-scale strain-zones and spatial pegmatite emplacement, and the chemical fractionation trend that records the formation of lithium-enriched pegmatites.

Changes in crop rotation productivity and stability of agrocenoses with prolonged use of fertilizers

The article considers the results of many years of field experiment (1968-2018) conducted in the Central part of the Non-Chernozem zone of Russia (Vladimir region). The research was carried out during eleven rotations of the four-field grain crop rotation. The study shows the effect of use of organic and mineral fertilizers applied in various doses and combinations on crop rotation yield, fertility of sod-podzolic sandy loam soil. It was found that the organomineral fertilizer system (manure 10 t/ha + N50P25K60) provided stable crop rotation productivity (on average for eleven rotations) at the level of 39.9 c. e./ha, or 79.7 % higher than the control without fertilizers. The mineral fertilizer system at medium doses of fertilizers (N50P25K60) was at the level of the organomineral system. The organic system was inferior in efficiency to the mineral system, both at medium doses (manure 10 t/ha) and at elevated doses (manure 20 t/ha). At the same time, the long-term use of organic fertilizers provided an increase in the humus content, depending on the dose of litter manure, by 16-36 % compared to the initial values. The use of organic fertilizers led to the stabilization of the content of available forms of potassium in the soil at an average and elevated level, respectively. Stabilization of the content of mobile phosphorus in the soil at the level of average supply was noted in mineral, organomineral and organic fertilizer systems, respectively, with low and medium doses. When using increased doses of fertilizers, there is a further increase in the content of nutrients in the soil. Growing crops in crop rotation without the use of organic and mineral fertilizers gradually led to a decrease in yield. The use of fertilizers provided greater stability of crop yields over the years of the study compared to the variant without fertilizers. The soil in the variants with organic (manure 20 t/ha) and organomineral (manure 10 t/ha + N50P25K60) fertilizer systems was characterized by high values of the main physiological groups of microorganisms. The ratio of the number of amylolytic and proteolytic microorganisms was 1.1-1.2, that indicated a balance in the processes of mineralization of organic matter in the soil and its humification.

Feasibility Evaluation of Highwall Mining in Open-Pit Coal Mine Based on Method of Integrated Analytic Hierarchy Process–Fuzzy Comprehensive Evaluation–Variable Weight Theory

Highwall mining is a method that involves using a continuous highwall miner system (CHM) to extract coal from the remaining coal seams, which has proven to be an effective and safe method for extracting coal after open-pit mining. However, application cases globally have shown that the feasibility of highwall mining in open-pit coal mines is subject to geological conditions, mining techniques, and other factors. If application conditions are not suitable, equipment may be trapped under collapsed coal–rock masses and unable to be retrieved, resulting in severe safety issues for slope stability. To meet the real-world demand for extracting the remaining coal in open-pit coal mines in China, it is urgent to conduct a feasibility evaluation of highwall mining in these areas. This paper establishes a mathematical evaluation framework for assessing the feasibility of highwall mining by summarizing a large number of engineering application cases globally and analyzing various technical characteristics such as geological deposit conditions, mining techniques, and technical equipment. The analytic hierarchy process (AHP), fuzzy comprehensive evaluation (FCE) and variable weight theory (VWT) are utilized in conjunction to form this framework, which includes four secondary indicators: geological deposit factors, mining technique factors, safety impact factors, and economic evaluation factors, and 20 tertiary sub-indicators, along with their corresponding characteristic values. The feasibility sub-set is divided into four categories: infeasible, basically feasible, relatively feasible, and highly feasible, and the values of the sub-indicators strictly follow and represent these four levels of feasibility. Weight vectors for the sub-indicators are obtained through a judgment matrix established within the mathematical evaluation framework. The fuzzy relationship matrix of the sub-indicators is constructed using fuzzy mathematical membership functions, and the final feasibility evaluation is determined through two-level comprehensive evaluation. The accuracy of the model is verified using the characteristic parameters of open-pit coal mines under two different conditions (JZT coal mine in Inner Mongolia, China, and GC coal mine in Australia). The results demonstrate that the maximum evaluation membership degree for the JZT mine is 0.7113, belonging to the “highly feasible” level, while the GC mine is 0.3304, belonging to the “basically feasible” level, which aligns well with real-world usage, proving that the evaluation model can effectively reveal the performance and membership degree of each indicator in different application cases. By quantitatively characterizing the feasibility level of highwall mining technology under different application conditions, this evaluation model can provide scientific guidance for coal mining enterprises to introduce CHM for highwall mining operation in open-pit coal mines.

Chemistry and boron isotope composition of tourmaline as a robust tool to characterize the origin of porphyry molybdenum systems: The case of Donggebi deposit in East Tianshan, China

Tourmaline is a chemically and mechanically stable mineral that commonly occurs in hydrothermal mineral systems, and has been used to trace the mineralization processes of many genetic types of ore deposits. Here we apply tourmaline chemistry and isotopic composition to trace the genesis of a porphyry Mo system for the first time. Tourmaline is widespread in the Donggebi Mo deposit in East Tianshan, NW China, where it occurs in five distinct associations: type PG disseminated in the porphyritic granite, TS as hydrothermal tourmalite in the country rocks (strata), V1 in quartz-molybdenite vein, V2 in quartz-polymetallic sulfide vein, and V3 quartz-calcite-fluorite vein. All the tourmaline types belong to the alkali group, with the V3 being schorl and the other types being dravite and schorl. The PG-type tourmalines partly inherit the features of the porphyritic granite, and are rich in F, Na, Al and Sc, and poor in Fe, Mg, Ca, Sr, Ba, Pb, V and Mo compared to the other types. They have low Fe3+ concentrations and low Fe3+/(Fe3++Fe2+) ratios, suggesting a reducing fluid system. They also display weaker Eu-depletion (with an average (Eu/Eu*)N value of 0.96) than the porphyritic granite, and are considered to be the products of interaction of the reducing fluids and the granites. The average (Eu/Eu*)N values of tourmalines decrease from 6.66 of type V1, 5.65 of type V2, to 4.80 of type V3, indicating that the fluids became progressively less reducing along with sulfide precipitation. The δ11B values of the tourmalines range between −15.9 ‰ and −12.5 ‰, resembling those of S-type granites or clastic sediment-sourced hydrothermal fluids. The tourmaline grains in our study do not display any remarkable δ11B variation from the cores to rims, indicating that the δ11B values of the fluids and their source were relatively constant.

Critical Minerals for a Carbon-Neutral Future

The Earth Mapping Resources Initiative is filling data gaps and fostering more holistic understanding of critical mineral resources in the United States using a novel mineral systems framework.

KARAKTERISTIK MINERALOGI PADA VEIN TEMBAGA KLUWIH, PACITAN, JAWA TIMUR

The southern mountains of Java are a path of copper-gold mineralization that has proven to have high economic value. Pacitan is part of the geological system and mineralization of the southern mountains, which are part of the Sunda Arc magmatism. The research area is located in the copper mining location in Kluwih village, Tulakan, Pacitan, East Java. The presence of copper mineralization in the form of massive sulfide/sulfosalt veins in the Kluwih area is evidence of an epithermal mineralization system which is rare and has not been studied intensively. This study intends to carry out mineralogical tests both physically and chemically for the characteristics and mineralogical composition of vein in the Kluwih area. The research was conducted using geological mapping methods in mine tunnels, rock sampling, laboratory analysis using petrographic methods, ore microscopy, rock geochemistry using ICP OES/MS – XRF – AAS, mineralogy using SWIR and XRD spectral analysis. The geomorphology of the Kluwih area and its surroundings consists of the morphology of alluvial plains and intrusive hills. Lithology is composed of volcanic–subvolcanic rocks in the form of porphyry dacite, dacite, dacite breccia, and alluvium. Mineralization forms in structural openings that cut and alter dacite rocks and dacite breccias. The alteration that develops in the Kluwih area, especially in the area around the mine (tunnel) is dominated by kaolinite-illite, pyrophyllite-little-sericite, chloritization, and mineralization found in the form of veins that have massive sulphide composition with the dominant internal texture being breccia. The texture or structure of the mineralization is in the form of brecciation (hydrothermal breccia), sulfide-pyrophyllite-kaolinite, quartz- sulfide/sulfosalt, and massif sulfide/sulfosalt. The results showed that the ore had a density of 4.65 gr/cm3 while the highly argillic altered side rocks had a density of 2.54 gr/cm3. In the ore, visible massive sulfide/sulfosalt minerals consist of mosaic bonds and intergrowth between similar or different minerals. The detected ore minerals are pyrite, enargite, covellite, chalcopyrite, and bornite. Enargite and pyrite are the dominant metallic minerals found in ores. Enargite crystals appear to have a size of 56 - 160µm, pyrite accumulates in anhedral crystal forms with a size of 120 - 900µm and inclusions in enargite measuring 50 - 140µm, along with covellite-chalcopyrite ± bornite minerals with a fine size of 5 - 20µm. The geochemistry of the ore is seen as sulfide filling, as evidenced by the SiO2 value of only 4.5% followed by metal enrichment in the form of 27.6% Fe, 12.6% Cu, 4.15% As, and 46.2% S. Alteration minerals which is present is probably a mica group such as phengite with a marked presence of elements of 0.7% MgO and 1.9% Al2O3. The geochemistry of the side rock is seen to have a high SiO2 value of 71.7%, followed by a high alkaline element forming alteration minerals such as pyrophyllite with an Al2O3 value of 15.3% with a low total Ca-Na-K value of 0.25%, and there is residual TiO2 by 0.38%. Terraspectral analysis and XRD confirmed that the main peaks were pyrophilite-phengite, followed by the minerals enargite and pyrite. The Kluwih vein is a copper vein associated with advanced argillic alteration, as part of a rich high sulfidation epithermal system with Cu-Au-As-Sb mineralization.

Discovery, geological setting and mineralization of the Shuvuutai molybdenum deposit, central-southern Mongolia

We document the newly discovered Shuvuutai Molybdenum (Mo) porphyry deposit located in the central-east Mongolian volcanic/-plutonic belt of the southern Altaids. The deposit is characterized by quartz vein- and veinlet-disseminated-type Mo ore bodies mainly hosted in a Late Permian-Early Triassic granitic intrusion. In this study, we provide a detailed study that integrates detailed geology with petrographic, mineralogic, geochemical, and geochronologic date to determine the tectonic setting of the deposit. Fluid inclusion analysis is used to reconstruct the fluid evolution history of the Shuvuutai Mo mineralization system and to understand the origin of the deposit. The ore bodies occur mainly as veins, lenses, and pods in positions from inner intrusions through contact zones to the host rocks distal to causative intrusions. The host rocks are variable in lithology, including granites, porphyries, volcanic breccias and tuffs, and sedimentary rocks. Outward from ore bodies to host rocks, the wall rock alteration is zoned from potassic (K-feldspar-quartz-mica), through phyllic (quartz-sericite-chlorite-epidote), to propylitic or argillic alterations. Two samples from porphyry stock intrusions at Shuvuutai were selected for U–Pb zircon geochronology and trace element composition studies, including the ore-hosting monzodiorite porphyry and quartz syenite porphyry. Our new ages are consistent with, or slightly postdate published zircon U-Pb ages of early phase of monzodiorite porphyry (268–232 Ma) and the main phase of quartz syenite porphyry (251.6 ± 1.7 Ma). Hydrothermal mineralization generally includes four stages, from early to late, represented by (1) potassic feldspar-quartz veins or veinlets, (2) quartz-molybdenite stockworks, (3) quartz-sulfide stockworks, and (4) quartz ± carbonate veins or veinlets. The ore-forming fluids were initially magmatic in origin and show high-temperature and high-salinity, containing daughter mineral and CO2-bearing fluid inclusions; and eventually evolved to low-temperature, low-pressure, low-salinity and CO2-poor meteoric water. S isotopic compositions of sulfides from the Shuvuutai Mo porphyry deposit indicate that the source of the ore-forming material was derived from the felsic magma. The Central-Eastern Mongolian volcanic-plutonic belt continues from Mongolia into northeast China, where similar Mo deposits are not yet recognized, suggesting that a new exploration strategy, based on the characteristics and history of the Shuvuutai discovery, is needed for the Chinese segment of the Altaids.

The gold mineral systems of the West Qinling orogen, central China: New insight from the Baguamiao gold deposit

The Baguamiao gold deposit is the first large deposit discovered in the West Qinling orogen in central China in the 1990 s. However, the occurrence of invisible gold in the deposit has not been reported. There is also no consensus on whether magmatic activity is involved in the gold mineralization, the style of mineralization, and the mechanism of gold precipitation. In this study, the in-situ trace elements, and chemical mapping of pyrite and pyrrhotite in the Baguamiao gold deposit were carried out for the first time. These data combined with the C-H-O isotope data of quartz, ankerite and calcite were used to determine mineralization process. In the Baguamiao gold deposit, five types of pyrite (Py0 to Py4) and pyrrhotite (Po0 to Po4) were identified, corresponding to the sedimentary-diagenetic period and four stages of mineralization (Stage I to Stage IV), respectively. From stage I to stage IV, gold mineralization in pyrite and pyrrhotite occurs as either visible or invisible crystals. The latter occurs dominantly as lattice-bound solid solutions (Au+) and is related to the content of Cu and Te. Co and Ni contents and Co/Ni ratios indicate that pyrite and pyrrhotite are magmatic-hydrothermal origin and affected by fluid-rock interaction. The change of Se and Te concentrations in pyrite and pyrrhotite indicates that oxygen fugacity (ƒO2) was increased from stage I to stage II, and then decreased during stage III and stage IV. In addition, the δ18O values of quartz, calculated δ18OH2O values of the ore-forming fluids and δ13C values range from 16.9 to 20.3 ‰, 7.7 to 12.9 ‰, and − 19.3 to + 0.2 ‰, respectively. Such isotopic signature records typical characteristics of orogenic gold deposit. The ore-forming fluid is a mixed hydrothermal solution involving metamorphic water, magmatic water, and meteoric water, and mixed with marine carbonate and sedimentary organic matter. Gold was precipitated by phase separation, fluid-rock interaction, and fluid mixing. Combined with the tectono-magmatic evolution, metamorphic deformation, and gold mineralization age of the West Qinling orogen, it can be concluded that with the closure of the Mianlue portions of the East Paleo-Tethys Ocean, the Baguamiao gold deposit was formed in the post-collisional extensional environment between the South China Block and the North China Block in the Late Triassic and is an orogenic gold deposit reference to the crustal continuum model.

Controversial Issues Related to Dye Adsorption on Clay Minerals: A Critical Review.

This critical review points out the most serious and problematic issues to be found in the literature on the adsorption of dyes on clay minerals. The introduction draws attention to the fundamental problems, namely the insufficient characterization of adsorbents, the influence of impurities on the adsorption of dyes, and the choice of inappropriate models for the description of the very complex systems that clay minerals and their systems represent. This paper discusses the main processes accompanying adsorption in colloidal systems of clay minerals. The relationship between the stability of the colloidal systems and the adsorption of dye molecules is analyzed. The usual methodological procedures for determining and evaluating the adsorption of dyes are critically reviewed. A brief overview and examples of modified clay minerals and complex systems for the adsorption of organic dyes are summarized. This review is a guide for avoiding some faults in characterizing the adsorption of organic dyes on clay minerals, to improve the procedure for determining adsorption, to evaluate results correctly, and to find an appropriate theoretical interpretation. The main message of this article is a critical analysis of the current state of the research in this field, but at the same time, it is a guide on how to avoid the most common problems and mistakes.

Ab-initio calculations and molecular dynamics simulations of In, Ag, and Cu replacing Zn in sphalerite: Implications for critical metal mineralization

Sphalerite has been recognized as the most important carrier mineral of the critical metal of indium (In), which mainly exists in sphalerite lattice through isomorphous substitution for Zn. It is widely reported that there are two significant coupled substitution schemes, namely Ag++In3+→2Zn2+ and Cu++In3+→2Zn2+, for In entering sphalerite in natural mineralization. However, there is still little known about physicochemical constrains on these two substitution reaction processes, which hinders the understanding of In mineralization. Thus, the current study uses ab-initio calculations and molecular dynamics simulations to investigate the replacement processes of Zn by In, Ag and Cu in sphalerite. The doped systems of Zn30InAgS32 and Zn30InCuS32, which correspondingly represent the products of the two substitution processes, were constructed by using 2 × 2 × 2 supercell model of sphalerite. Molecular dynamics method was employed to simulate the doped models, obtaining average configurations and formation energies at different temperatures. Then, ab-initio calculations were utilized to study the population values and electronic properties of the simulated configurations. In order to simulate a system close to natural mineralization conditions, a constant pressure of 30 MPa was set in molecular dynamics simulations, as this pressure level can represent the average metallogenic pressure observed in magmatic-hydrothermal deposits associated with In-bearing sphalerite. The temperature parameters were tested within the range of 175 °C to 400 °C, covering the known possible ore-forming temperatures. The simulation results show: (1) it is more stable for In to enter sphalerite via the coupled substitution scheme of Cu++In3+→2Zn2+ than that of Ag++In3+→2Zn2+; (2) the favorable temperatures for the two substitution processes are 225–250 °C and 325–350 °C; and (3) the changes in chemical reactivity caused by temperature fluctuations during the substitution processes of Zn by In, Ag and Cu may lead to the cyclic oscillation distribution that is commonly observed for In within sphalerite in magmatic-hydrothermal mineralization systems. This discovery not only shows the physicochemical properties of In-rich sphalerite formed by the two reaction processes of replacement of Zn, but more importantly, provides deep insights into the natural mineralising process of In at the atomic or/and molecular scale.

Re-examination of the Aïn Allegua-Aguiba celestite-Pb-Zn salt diapir-related Mississippi Valley-type deposits (Nappes zone, Northwestern Tunisia): New conceptual model

The celestite-rich and Pb-Zn-poor Aïn Allegua deposits are located at the northeastern extremity of the Dougas diapir in the Nappes zone of northern Tunisia. The Sr-Ba-Zn-Pb mineral system studied in this paper is enclosed in a Triassic breccia, labeled cap rock, located between the Triassic diapir and the surrounding Cretaceous to Lutetian marine sediments. It consists of evaporite dissolution float breccia where Triassic dolostone clasts are floating in a Triassic matrix of anhydrite and argillites. Five mineralizing stages are recognized, which are from early to late: celestite (stage 1); hydrothermal dolomite (stage 2); crosscutting galena-barite or sphalerite-galena-barite-calcite (stage 3); (4) fracture and karst filled by barite, celestite, and galena (stage 4); and late supergene mineralization (strontianite, smithsonite, and cerussite) (stage 5). The present study shows that the celestite and Pb-Zn mineralization formed from the circulation in the cap rock of at least three fluids: (1) fluid A (100–150 °C; 10 to 25 wt% NaCl eq.) deposited the celestite; (2) fluid B (125 to 185 °C; 29 to 34 wt% NaCl eq.) deposited the hydrothermal dolomite, and (3) fluid C (temperatures around 90 °C; 14 to 22 wt% NaCl eq.) deposited the calcite that accompanied sphalerite and galena precipitation. The δ34S values for sphalerite and galena fall within a narrow range from + 10.4‰ to + 18.9‰ (avr. 13‰) indicating a homogeneous source of sulfur. The δ34S values of celestite and barite are also relatively homogeneous from + 14.7 to + 23‰ (ave. + 16.5‰) and match those of Tunisian Triassic gypsum and Triassic marine sulfates (δ34S = +15‰). The temperature of deposition together with sulfur isotope data indicate that the reduced sulfur in sulfides was derived through thermochemical sulfate reduction of Triassic sulfate. The lead isotopes in galena show that Pb, and probably Zn and Ba were extracted from the upper crustal rocks. Part of the strontium is derived from the Triassic anhydrite and the other part is probably transported to the cap rock in formation waters. The tectonic setting, the carbonated nature of the host rocks, the epigenetic style of the mineralization, and the mineral associations, together with fluid inclusions data and sulfur and lead isotopes show that the Aïn Allegua deposit belongs to the diapir-related Mississippi Valley-type (MVT) deposits of the Eastern Maghreb salt diapirs province, that formed, as the most of the MVT deposits and districts in the world, from basinal brines with no mixing with metamorphic and/or magmatic fluid or involvement of a heat source from a concealed sill or magmatic intrusion.

In situ trace element compositions of sulfides constraining the genesis of the worldclass Shuangjianzishan Ag-Pb-Zn deposit, NE China

The worldclass Shuangjianzishan Ag-Pb-Zn deposit, containing proven reserves of >21,665 t of silver @128.5 g/t, >3.3 Mt of lead @1.6 wt%, and >1.9 Mt of zinc @0.6 wt%, is the largest silver deposit in Asia. This giant Ag mineralization system has attracted extensive attention since its discovery. However, the incorporation mechanism of Ag in ore sulfides and the deposit genetic type are still greatly debated. We have conducted in situ LA-ICP-MS trace element analyses for sulfides in this deposit to address the above issues. Three paragenetic stages of mineralization were recognized at Shuangjianzishan, including pyrite + quartz + K-feldspar stage (I), galena + sphalerite + Ag-bearing sulfosalt + quartz + calcite + chlorite + sericite stage (II), and post-ore quartz stage (III). Most sulfides and silver minerals were deposited in stage II. In situ time-resolved depth profiles, principal component analysis (PCA), and correlation plots of trace element for sulfides indicate that trace elements are dominantly present in sulfides as solid solutions and nano-inclusions, and less as micro-inclusions. For silver, the most critical element in the studied deposit, its substitution mechanisms vary largely among sphalerite, pyrite, and galena. In sphalerite, Ag enters the crystal lattice associated with coupled substitution of Zn by Fe, Sn, Sb, and Ga. In pyrite, Ag enters the lattice through the coupled substitution of Fe by Cu, Zn, and Sn. In galena, Ag enters lattice by the coupled substitution of Pb by Sb and Zn. Based on the GGIMFis geothermometer calculations, the temperatures for ore stage II range from 290° to 333 ℃ (mean of 319 ℃), which are almost identical to the results of the sulfur isotope geothermometry and fluid inclusion thermometry from the previous studies. Furthermore, the trace element distributions in the Shuangjianzishan sulfides, e.g., the enrichment of Fe, Mn, Sn, Cu, Ag, Sb and Pb and the depletion of Ga, Ge, Co and In in sphalerite, as well as the geological and geochemical features, infer that the studied deposit is similar to the typical epithermal type deposit. We therefore propose that the worldclass Shuangjianzishan Ag-Pb-Zn deposit is an epithermal deposit, and this contribution indicates that in situ LA-ICP-MS trace element analysis of sulfides could help shed light on identifying the genetic type for the hydrothermal ore deposits.

Carbon emission free preparation of calcium hydroxide with calcium carbide slag (CCS) through micro-bubble impurities removal

Calcium hydroxide is a widely used bulk chemical, and traditional limestone calcination to prepare hydrated lime emits large amounts of CO2. Calcium carbide slag (CCS) is a waste residue with calcium hydroxide as the main component emitted by the PVC industry, which can be directly used to prepare calcium hydroxide. However, CCS has problems such as high impurity content, complex impurity occurrence state, and difficult separation. In this paper, the raw CCS and products under different separation conditions were prepared, and the presence state of main elements (Ca, Al, Si, Fe, C, Mg) in the CCS were studied by using XRD, XRF, XPS, SEM-EDS, and EPMA + SXES. According to the presence state of impurities, the microbubble strengthens in combination with agents used for deep directional separation of impurities in CCS, and DFT is used to calculate the surface binding energy between each component and agent in CCS. The results demonstrated that CaC2 and C wrap each other in CCS. Morphological and elemental chemical analyses of the dissociated residues revealed the existence of Si in the form of SiC and SiO2. Fe and C existed as particles of FeSi and carbon respectively. Al exists in the form of CaAl2O4 and Al2O3. Mg is loaded on the SiC in the form of Ca–Al–Mg mineral system. After the separation of microbubble equipment strengthens in combination with agents, the acid insoluble content can be reduced from 1.99% to 0.76%. At the same time, the yield can also reach 71.34%, and all indicators meet the standard indicators of industrial calcium hydroxide. The results can provide a new zero-carbon preparation pathway for calcium hydroxide.

Variscan structural evolution and metallogenic implications at the paleozoic maider basin, eastern anti-atlas, Morocco

In the Moroccan eastern Anti-Atlas, the Paleozoic Maider basin, hosts a range of economic mineral deposits, including Cu, Pb, Fe, and barite forming an important mineralized vein system. In this study, detailed mapping of fractures and veins, structural analysis, and measurements have been integrated to understand the structural control, the tectonic evolution, and fault kinematic history in the Paleozoic outcrops of the Southern margin of the Maider basin. The structural analysis shows two folding phases: (i) a first phase, which generates WNW-ESE-trending folds, in response to an NNE-SSW compression, likely, of Late Westphalian age. And (ii) a second phase which develops N–S metric folds, under a NE-SW to E-W compression, compatible with the Late Variscan shortening, known in the East Anti-Atlas and the Ougarta belt during the Stephano-Autunian period. Moreover, three main fault systems were distinguished: WNW-ESE to E-W, NE-SW and scarcely N–S. These fault systems record evidence of a previous extensional tectonic event that probably corresponds to the Devonian extensional event. During the late Variscan shortening, these faults were reactivated into a left-lateral strike-slip movement with a small reverse component for the WNW-ESE to E-W faults, and right lateral strike-slip motion for NE-SW ones. The mineralization primarily takes place within a vein-type system, which is predominantly found in a network of faults oriented between N30 and N60. These ore bodies present frequently lenticular and banded geometries, and do not show any evidence of deformation, suggesting probably a post Variscan emplacement age. Thus, we could link the mineralization emplacement to the Triasic Central Atlantic rifting.

A national-scale mineral potential assessment for carbonatite-related rare earth element mineral systems in Australia

The production of rare earth elements is critical for the transition to a low carbon economy. Carbonatites (>50% carbonate minerals) are one of the most significant sources of rare earth elements (REEs), both domestically within Australia, as well as globally. Given the strategic importance of critical minerals, including REEs, for the Australian national economy, a mineral potential assessment has been undertaken to evaluate the prospectivity for carbonatite-related REE (CREE) mineralisation in Australia. CREE deposits form as the result of lithospheric- to deposit-scale processes that are spatially and temporally coincident.Building on previous research into the formation of carbonatites and their related REE mineralisation, a mineral system model has been developed that incorporates four components: (1) source of metals, fluids, and ligands, (2) energy sources and fluid flow drivers, (3) fluid flow pathways and lithospheric architecture, and (4) ore deposition. This study demonstrates how national-scale datasets and a mineral systems-based approach can be used to map the mineral potential for CREE mineral systems in Australia.Using statistical analysis to guide the feature engineering and map weightings, a weighted index overlay method has been used to generate national-scale mineral potential maps that reduce the exploration search space for CREE mineral systems by up to ∼90%. In addition to highlighting regions with known carbonatites and CREE mineralisation, the mineral potential assessment also indicates high potential in parts of Australia that have no previously identified carbonatites or CREE deposits.

Genesis of the Taoguanping molybdenum deposit in the Northern Qinling Belt, Central China: Constraints from geology, fluid inclusions, and H–O–S isotopes

The Taoguanping molybdenum deposit is located in the west of the Mangling pluton in the Northern Qinling Belt, but its fluid characteristics and ore-forming process are unclear, hindering the understanding of its ore genesis and genetic model. The paragenetic sequence of the Taoguanping molybdenum deposit can be divided into: quartz–K-feldspar–sulfide stage (Stage I), quartz–polymetallic sulfide stage (Stage II), and quartz–calcite stage (Stage III). Stage I is characterized by disseminated molybdenite mineralization associated with siliceous and K-feldspar alteration in the medium- to fine-grained monzogranite, representing the early mineralization. Stage II is the main mineralization featured by coarse-grained quartz–sulfide veins, e.g., quartz–molybdenite and quartz–biotite–molybdenite ± pyrite ± chalcopyrite veins, crosscutting monzogranite and host rocks. Stage III is late hydrothermal veins to crosscut former minerals. Detailed fluid inclusion study shows that temperature and salinity of fluids decreased from Stage I (peaks at ca. 320–380 °C and 3.7–13.6 wt% NaCl eqv.), through Stage II (peaks at ca. 260–300 °C and 1.2–11.8 wt% NaCl eqv.) to Stage III (peaks at ca. 180–220 °C and 0.4–8.9 wt% NaCl eqv.), accompanied by fluid mixing and boiling. The H–O isotopes of quartz (δDfluid = –72‰ to –53‰ and δ18Ofluid = 9.1–10.9‰) suggest Stage II fluids are magmatic–hydrothermal origin mixed with minor meteoric water. The in-situ sulfur isotope of pyrite (–33.4‰ to –13.4‰ and 0‰ to 7.8‰) indicates Stage II fluids being mainly magmatic–hydrothermal origin, with participation of strata materials inferred by presence of Stage II euhedral to anhedral pyrite with inclusion-rich domains and CH4 in Stage II fluid inclusions during fluid–rock interaction. In combination of this study and regional tectonic setting, we propose that the Taoguanping molybdenum deposit underwent porphyry and hydrothermal vein-type mineralization, contributed by medium- and fine-grained monzogranite and possible granite porphyry, respectively, which should be ascribed to a porphyry mineralization system and formed in a post-collisional setting during the Late Mesozoic.

The metasedimentary-hosted Nyangoubé gold prospect, northwest Côte d’Ivoire: Geochemical and mineralogical characterization of associated hydrothermal alteration

The Nyangoubé gold prospect, located in northwestern northwest of Côte d’Ivoire in Africa, is a feature of the Bagoé furrow of the Birimian of the West African Craton. This study is aimed at characterizing the geochemical and mineralogical signatures of hydrothermal alterations associated with the gold mineralization of Nyangoubé gold prospect to provide guidelines for mining exploration. Microscopic petrographic analysis and geochemical characteristics from elemental contents analyzed by X-ray fluorescence (XRF) and inductive coupled-plasma mass spectrometer (ICP-MS) were studied using alteration diagrams and by calculating mass balances and describing thin sections. The results indicate that the host rocks have been affected by silicification, carbonation, sericitization, chloritization, sulphidation and albitization. Hydrothermal alterations associated with the mineralization systems resulted in the destruction of plagioclase in the metasediments studied. The latter was replaced by sericite, chlorite, carbonates, quartz, and sulphides in varying proportions, depending on the intensity of each type of alteration linked to the formation of each mineral. The mass balance calculations show a gradual increase in the concentrations of Au, W, V, As and Pb as well as K2O, CaO, Na2O and Fe2O3 which could be vectoring parameters towards gold mineralization. The mineralogical assemblage as sericite-chlorite-pyrite, chlorite-pyrite±sericite, carbonate-sericite and chlorite-carbonate revealed by hydrothermal alteration trends in the host rocks could also help identify potential gold corridors in the area of study and its peripheries.

Magnetite trace element characteristics and their use as a proximity indicator to the Avoca Tank Cu-Au prospect, Girilambone copper province, New South Wales, Australia

AbstractThe Avoca Tank orebody is one of a series of copper-rich orebodies occurring within the Girilambone Cu province of central New South Wales. Mineralisation at Avoca Tank is hosted within several narrow, chloritic, greenschist-facies shear zones which developed ~430 Ma (U-Pb titanite) within metasedimentary rocks around the margins of an Ordovician (ca. 470 Ma) mafic sill complex. Mineralisation at Avoca Tank preserves an early oxide phase (sulfide barren) as magnetite-rich shears that are overprinted by a pyrite-chalcopyrite-rich sulfide phase. The mineralogical and chemical footprint surrounding sulfide mineralisation is narrow (<50 m) offering limited ore vectoring using mineralogical and chemical change. However, magnetite-rich shears occur external to and within sulfide mineralised intervals, and magnetite within these shears displays distinctive trace element variation depending on proximity to Cu mineralisation. Changing magnetite trace element chemistry with increasing Cu abundance at Avoca Tank is best represented by two ternary systems. A ternary plot of Ni-V-Ti effectively separates magnetite from unmineralised zones via Ni abundance, while the ratio of Ti to V effectively separates magnetite from low-, moderate- and high-grade Cu zones. A ternary plot of Sn (100*Sn)-Zn-Ni effectively discriminates between unmineralised, low-grade and combined moderate- to high-grade zones. The greatest control here is the ratio of Zn to Sn, but the inclusion of Ni abundance provides a greater separation between low- versus combined high- and moderate-grade ore. Many of the trace element trends recorded in magnetite are mirrored in the overprinting sulfides. We propose a two-phase mineralising system, with initial development of chemically uniform, sulfide barren magnetite-chlorite-rich shear zones in proximity to the margins of older mafic sills. A subsequent, and potentially hotter (+60 °C), fluid harvested the early oxide for Fe, with the partial replacement, recrystallisation and re-equilibration magnetite within a sulfide-rich hydrothermal fluid under greenschist facies metamorphic conditions. As many known orebodies in the Girilambone Cu province are associated with magnetite-rich gangue, magnetic surveys are an effective exploration technique. Based on this pilot study, mapping trace element variation in magnetite within these bodies is an additional ore-vectoring technique in the search for economic Cu mineralisation in this province.

Cobalt Prospectivity Using a Conceptual Fuzzy Logic Overlay Method Enhanced with the Mineral Systems Approach

AbstractThis paper describes mineral prospectivity research conducted in Finland to predict favorable areas for cobalt exploration using the “fuzzy logic overlay” method in a GIS platform and public geodata of the Geological Survey of Finland. Cobalt occurs infrequently as a core product in mineral deposits. Therefore, we decided to construct separate conceptual mineral prospectivity models within the Northern Fennoscandian Shield, Finland, for four deposit types: (1) “Orthomagmatic Ni–Cu–Co sulfide deposits,” (2) “Outokumpu-type mantle peridotite-associated volcanogenic massive sulfide (VMS)-style Cu–Co–Zn–Ni–Ag–Au deposits,” (3) “Talvivaara black shale-hosted Ni–Zn–Cu–Co-type deposits” and (4) “Kuusamo-type (orogenic gold with atypical metal association) Au–Co–Cu–U–LREE deposits”. In addition, we created a model combining till geochemical data with data derived from bedrock drilling and mineral indications, including boulders and outcrops. The mineral prospectivity models were statistically tested with the “receiver operating characteristics” method using exploration drilling data from known mineral deposits as validation sites. In addition, the predictive performance of the models was evaluated by using success rate curves, where the number of previously identified deposits was compared with the area coverage of the predicted highly favorable areas. These results indicate that the knowledge-driven mineral prospectivity method using parameters derived from mineral systems models is effective in defining favorable exploration target areas at the regional scale. This study's innovation lies in its comprehension of the process of evaluating mineral prospectivity when the commodity of interest is not the primary commodity within the mineral system.

Experimental and modeling investigation of dual-source iron release in water-solid-gas interaction of abandoned coal mine drainage.

After mine closure and flooding, abandoned iron-prone devices and equipment (e.g., steel bolts and ground support meshes) and iron-bearing minerals (e.g., pyrite) form a dual-source iron pollution system in mine groundwater. Dual-source iron contributes to the water-solid-gas interaction in abandoned coal mines and the release of iron at different periods after mine closure, posing environmental risks in groundwater and discharging acid mine drainage, which contains large amounts of iron. In this study, a series of hydrochemical experiments were conducted to simulate the iron release process of the dual-source system, and electrochemical experiments were carried out to reveal the reaction mechanism, characterize the dual-source iron pollution release mode and quantify the release rate ratio. PHREEQC package was used to simulate the long-term hydrogeochemistry reactions of the water-solid-gas interaction to determine the key factors and suitable conditions that inhibit dual-source iron release. The results show that the dual-source system of iron-bearing minerals (pyrite) and steel bolts promote iron release from each other. The resulting calculated annual iron release indicated that the overall iron release rate ratio is: dual-source > bolt > pyrite, indicating that mine water would remain acidic for a long time due to the continuous release of iron from the system. Numerical modeling results show that maintaining the environment temperature below 25°C and the pH above 3.5 is an effective way to reduce the iron release rate.