Minerals, Volume 12, Issue 8 (August 2022) – 144 articles

We provide results of a comprehensive mineralogical and microstructural study of relict lherzolites of the main ore field and fresh rocks from a deep structural borehole drilled in the south-eastern part of the Kempirsay massif. Olivine and orthopyroxene from lherzolites contain numerous pieces of evidence of material redistribution at different scales caused mainly by solid-state processes, such as plastic flow of mantle, syntectonic recrystallization, and annealing. The results of deformation-induced processes at the submicron scale are recorded by optical and electronic microscopy. In olivine, the plastic deformation caused segregation of impurities at structural defects. As a result, abundant tiny rods of newly formed Cr-spinels occurred inside its grains. Moreover, in enstatite, deformation caused partial or complete chemical decomposition with exsolution of diopside, pargasite and spinel lamellae up to the formation of a “fibrous” structure. In other cases, it provided partial or complete recrystallization to form new phases of enstatite-2, forsterite, diopside, pargasite, and spinel. Petrographic observations are validated by geochemical data, i.e., regularly decreasing concentrations of minor elements in neoblasts compared to large grains (porphyroclasts). Further redistribution of spinel grains with the formation of chromitite bodies is witnessed by their permanent association with the most mobile phase of the upper mantle, i.e., olivine, which is the only mineral that remains stable under the intense plastic flow. An increased concentration of Cr-spinel grains during formation of massive chromitites could appear under conditions close to pressure sintering, as evidenced by stressed textures of ores and an increased grain size compared to disseminated chromitites. The formation of unique chromitite deposits is associated with integration of numerous disparate podiform bodies into “ore bunches” due to the tectonic impact in the shear-compression regime. This was most likely associated with transition of the rifting (spreading) regime to that of the upper mantle of the fore-arc basin. Full article

Rare earth elements and yttrium (REY) are essential for manufacturing technologies vital to economic and national security. As the demand for REY increases and conventional ores become depleted, attention is turning to unconventional resources like coal as a source for these elements. As the nation’s second-largest coal producer, West Virginia (WV) has the potential to transition into producing REY. This study utilizes open-access coal chemistry data from the USGS COALQUAL database in order to assess the potential of WV coal deposits as resources for REY and to gain insight into elemental modes of occurrence and possible enrichment mechanisms. Results suggest that clay minerals dominate the inorganic fraction of most samples and that REY concentrations are primarily proportional to the inorganic content. A few samples deviate from this trend due to mineralogic differences and impacts of post-depositional processes, including possible hydrothermal fluid influences. An ash-basis economic assessment identified 71 promising samples in the data set. The majority of promising samples were sourced from lower to lower-middle Pennsylvanian coal seams in the Kanawha, New River, and Pocahontas formations. Future studies should investigate these deposits using direct analytical methods to better characterize vertical and lateral heterogeneity in REY concentrations and confirm modes of occurrence. Full article

Alluvial placer gold deposits that accumulate in streams across the globe are essentially allochthonous sedimentary deposits that are transported from their source to their location of deposition. The purpose of this study was to find placer gold deposits in alluvial sediments along the Indus River in the NW Himalaya of Pakistan. The investigated region was divided into five clusters based on river morphology. The research focused on mineralogical distribution, sediment source, gold transport distance, elemental composition, and gold concentration in river sediments. Throughout, during the deposition at point and channel bars, the mixed source of alluvial sediments was revealed by its mineralogical composition. However, the SEM analysis demonstrated that the gold grains had a high flatness index, indicating that they had been transported a significant distance. The elemental composition of several samples revealed a significant concentration of silicon dioxide, iron oxide, and alumina oxide transported from the Himalaya. The study of the trace elements indicated gold and related base metals with granitic provenance were transported from an acidic/granitic source. Based on gold concentration, it is demonstrated that the left riverbank (clusters C1, C2, and C3) has a higher concentration of gold deposits and higher potential for economic gold exploration than the right bank (clusters C4 and C5) due to the lower velocity of running water in the study area. The findings revealed that the studied area has good potential for commercial exploration of gold resources, and the workflow can be adopted in any region with a similar geological setting and morphology. Full article

The Gangdese magmatic rocks of the southern Lhasa terrane, are generally thought to be an important window to witness the formation and evolution of the Neo-Tethys oceanic opening, subduction, and closure, and India-Eurasian continental collision. We investigated a new occurrence of granodiorite in the Nuocang district of western Gangdese, southern Lhasa terrane, and conducted a series of analyses on their petrology, chronology, and geochemistry. The Nuocang granodiorites have the zircon U-Pb ages of 151–154 Ma, which suggest that Late Jurassic granitoids are present in the western Gangdese of southern Lhasa terrane. They are relatively high in SiO₂, Al₂O₃, low K₂O, Na₂O, and Sr/Y ratios, enrichments of LILE and LREE, and depletion of HFSE, with the positive correlation between Rb and Th, and negative correlations between SiO₂ and P₂O₅, Rb, and Y, showing the features of I-type granites. The relatively high (⁸⁷Sr/⁸⁶Sr)_i values from 0.712231 to 0.712619, low εNd(t) values from −9.56 to −8.99, together with the negative εHf(t) values from −10.8 to −5.0 (mean value −8.9) suggested that the Nuocang granodiorites probably sourced from the partial melting of the ancient Lhasa terrane, with parts of mantle materials involving in. Combined with the previous geochronology and geochemical data of Mesozoic magmas in the Gangdese belt, as well as the Late Jurassic granodiorite, in this paper, we propose that the Nuocang granodiorites formed in a continental margin arc environment triggered by the northward subduction of Neo−Tethys oceanic crust. Full article

There is an increasing demand to simulate and optimize the performance and profit of comminution circuits, especially in low-grade ore processing, as is the case with critical metals minerals. Recent research has shown that the optimization result is greatly influenced by quality aspects of the products, such as cost, profit, and capacity. This paper presents a novel approach to performing a multi-objective technical and economic analysis of tantalum ore processing to increase the production of critical metals minerals. The article starts with mineral composition analysis to highlight the potential of strategies for balancing the process layout for maximized production. The introduction of a combined technical and economic analysis presents the possibility of improving the profit by rearranging the mass flow given the rock’s mineral composition. Results show that selective comminution can improve process capacity by 23% and decrease production cost by 10% for the presented case. Full article

This study aims to compare two approaches for the reserve calculation of cement raw material by geological sections and structural maps. The first is legally based, and its accuracy is approved by periodical calculation of the exploited material on site. In this research, it was crucial to determine deviation in the calculation approach, i.e., geological section volume calculation versus the volume obtained as a software solution estimated as a number of cells between two structural maps, i.e., maps interpolated at the top and bottom of the analysed lithological unit. Due to complex mineralogy, raw cement needs different energy consumption that directly affects the procedure of cement production, e.g., increases in air pollution through CO₂ emissions. The research area was the exploitation field “St. Juraj–St. Kajo,” situated near the town of Split, region of Dalmatia, Southern Croatia. In the deposit, there are seven different lithological units, and all were technologically divided based on their chemical compounds. The lithology included dominantly marl and sandstone with occasional alternations of the conglomerate. Although in the geological sense it is considered a single unit, it partially contains interlayers in the form of lenses such as limy (calcitic) marl, clacisiltite (clayey limestone), and clayey marl. Generally, the knowledge of interlayers’ existence is more important than their exact quantity because it affects expectations of a nonuniform material’s technological quality at the location. For the purpose of the analysed lithological unit calculation, the volumes of the interlayers within were determined as well. Using geological sections for volume calculation is based on the calculation of the block volume (V) between two parallel vertical sections (P₁, P₂), which is obtained as a product of the mean areas (Paverage) of adjacent parallel sections (P₁, P₂) multiplied by the distance between them (d). Structural maps represent the calculation of the volume of the analysed object under a function f (x, y) defined by a double definite integral. Comparison of research results encourages the use of software solutions for the volume calculation of cement raw material volume in the future. Full article

The present field and petrographic investigations of the Tortonian to Gelasian Siwalik Group in the core of the Hazara-Kashmir Syntaxis have been carried out to comprehend the middle stage Himalayan orogeny that resulted from the collision of Indian and Asian plates. The Chinji, Nagri, Dhok Pathan, and Soan Formations of the Siwalik Group were deposited by river meandering flood plains, braided rivers, and alluvial fan systems, respectively. The Siwalik Group is classified into seven major facies and many minor facies based on sedimentological properties. According to the petrographic analysis, the Siwalik Group sandstone is classified as litharenite and feldspathic litharenite petrofacies. The sandstone of the Siwalik Group is texturally mature, but compositionally it is immature. The data shown on the tectonic discrimination diagrams point to a recycled orogen provenance field for the Siwalik sandstone. In addition to quartz and feldspar, the sandstone includes clasts of volcanic, metamorphic, and sedimentary rock types. The igneous and metamorphic rock clasts were derived from the Lesser and Higher Himalayas. The sedimentary lithic fragments, on the other hand, are derived from both the earlier molasse and pre-molasse rocks. The presence of lithic fragments of the earlier molasse sandstone in the Siwalik sandstone indicates that the Siwalik Group sandstones were deposited during the Middle Stage of the Himalayan orogeny. The paleoclimatic conditions were semi-arid to semi-humid during the Siwalik Group’s deposition. The presence of clay minerals in the shale reveals the intense chemical weathering processes that occurred during their deposition on the flood plains of the river meandering system. Full article

In this study, the Lagrange element strength reduction method is used to explore slope stability and as an evaluation method of underground mining of end-slope coal in a rock-stability analysis. A numerical analysis model is established herein using the geological conditions for mining in a coordinated open pit with an underground mining area of the Anjialing Open-Pit Mine and Underground No. 2 Mine. Additionally, the evolution law of slope stability in open-pit end-slope mining is studied using the proposed numerical simulation method. According to our findings, the steps show obvious horizontal movement and deformation under the influence of underground mining disturbances. Taking the horizontal displacement at the slope tops of the steps as the deformation index, the entire disturbed slope is divided into four regions: upper, middle-upper, middle-lower, and lower steps. When a step is fully affected by underground mining, its subsidence value first increases rapidly and then slowly. An exponential function is used to reflect the change rule in the step-subsidence value as the working face advances. In the underground mining process, the critical sliding surface of the slope develops along the soft rock or coal seam, showing an L-shaped or a W (double L)-shaped broken line. As the working face advances, the initial position of the sliding mass is unchanged while the cutting position alternately changes up and down in the weak plane. The safety factor suddenly drops when the advancing distance exceeds a certain value. Full article

Ordinary chondrites are the most common type of chondrites. As a non-destructive, rapid, and semi-quantitative technology, Raman spectroscopy is widely used in geoscience. This paper presents the results of a Raman spectroscopic study that we conducted for 16 ordinary chondrites with different chemical groups and variable degrees of shock metamorphism. We found that: (1) the relationship between the Fe composition of olivine and pyroxene and the characteristic peaks of the Raman spectrum established by predecessors cannot be refined to the range of meteorites, the shock on meteorites also affects the Raman spectral characteristics of minerals and (2) the full width at half maximum (FWHM) of the shocked minerals (including high-pressure minerals) in meteorites increases in the Raman spectrum, however, no clear numerical relationship with pressure was found. Based on these data, we assess that the feasibility of Raman spectroscopy for the classification of chemical group and shock metamorphism in ordinary chondrites is not well established. Full article

The paper is focused on the analysis of the relation between the stability of the flotation process and the efficiency of Machine Learning (ML) algorithms based on the flotation froth images. An ML process should enable researchers to construct Artificial Intelligence (AI) algorithms for flotation process control. The image of the flotation froth includes information characterizing the flotation process. The information can be extracted with the aid of the Image Recognition (IR) algorithms based on the ML. This enables construction of a flotation process control system in the mineral processing plant, which is based on the recognition of images of the flotation froth. The IR algorithms do not provide stable image recognition results and are not efficient in the situation where the parameters of the flotation process are highly unstable. The classification results were equal to 75.11% and 69.62% for a stable and unstable process, respectively. The experimental data collected at the Polish Pb/Zn mineral processing plant provided better insight to the relationships between the flotation process parameters and ML efficiency. These relationships were analyzed, and guidelines for the construction of the ML process for flotation process control have been formulated. Full article

Autotrophic acidophilic bacteria Acidithiobacillus ferrooxidans is a model species for studying metal bioleaching from low-grade sulfide ores and concentrates. Arsenopyrite gold-bearing concentrates are refractory and often processed using biohydrometallurgical approaches; therefore, it is important to develop methods to improve arsenopyrite bioleaching. In the present work, we have studied the possibility of improving arsenopyrite concentrate bioleaching by the strain of A. ferrooxidans. For this purpose, we have analyzed the genome of the strain A. ferrooxidans TFBk to reveal the genes potentially important in the bioleaching process. Genes determining resistance to arsenic, as well genes involved in the utilization of C₁-compounds and resistance to oxidative stress, were revealed. Therefore, the possibility of increasing the rate of arsenopyrite concentrate bioleaching using C₁-compounds (methanol and formate) was studied. Formate was able to increase both the biomass yield of the strain A. ferrooxidans TFBk as well as the bioleaching rate. In addition, the effect of redox potential increase by means of the addition of sodium persulfate in the medium on arsenopyrite concentrate bioleaching was studied. It was shown that the addition of 0.1% sodium persulfate stimulated strain growth, while a higher concentration inhibited it. Despite this, the rate of concentrate bioleaching increased in the presence of 0.5–1.0% of persulfate, which may be explained by the interactions of added oxidizer with concentrate components. Full article

Rock materials are often affected by water in underground engineering. In this study, the mechanical and failure characteristics of tuff under different moisture content were studied using laboratory tests. The moisture content variation of tuff was studied in water absorption tests, and the mechanical and failure characteristics of tuff under different moisture contents were studied through uniaxial compression tests with a Micro-II acoustic emission (AE) control acquisition system. The results showed that the moisture content of tuff increases rapidly at the initial stage of water absorption tests and stabilizes after 180 h of immersion. According to the results of uniaxial compression tests, both uniaxial compressive strength and elasticity modulus decreased with the increase in moisture content. The AE parameters analyses showed that, when the moisture content increased, the accumulated AE counts and energy gradually decreased, and the “quiet period” at the initial stage of uniaxial compression tests lasted longer, and the RA (rise time⁄amplitude)–AF (AE counts⁄duration) distribution and the failure characteristics verified that the failure patterns evolved from shear failure to tensile failure. Scanning electron microscopy was used to observe the morphology of the fracture surface and analyze the influence of moisture content on the fracture characteristics of the tuff at the mesoscopic level. The results of this research can be used as a basis for studying the influence of water on tuff. Full article

Multiple episodes of dolomitization of the shallow marine carbonates of the Late Kingriali Formation resulted in regional scale mappable dolostone geobodies in the Kohat and Potwar sub-basins. With the exception of few unaltered patches of the host limestone, more than 90% of the carbonates of the studied formation are diagenetically altered by replacive dolomites with associated dolomite cementation. Petrographical and geochemical data interpretation reveals that during the initial stage of dolomitization, the precursor limestone was significantly modified by the fabric-retentive replacive dolomite (RD-I) and produced bulk dolostones with non-planar-a to planar-s crystals. Neomorphic recrystallization (RD-II) was observed as an overgrowth of the already formed RD-I dolomite crystals during progressive dolomitization. The seawater at shallow depths is enriched with Fe-ions due to its interaction with Fe-rich beds within the studied formation. The modified seawater actively participated in the formation of ferroan replacive dolomites (RD-III). Stable isotopic composition of the unaltered Echinoderm plates, calcite cement (CC-I), and RD-I demonstrates signatures of δ¹⁸O and δ¹³C within the limit of late Triassic marine seawater or modified seawater. Depletion in the stable oxygen isotopic composition (from −0.99‰ to −3.75‰ V-PDB) demonstrates that RD-II and RD-III were formed in a sequence with progressively higher temperature fluids than normal seawater. Precipitation of dolomite cements as cavity filling rhombs (DC-I) and crystal overgrowth (DC-II) with highly depleted δ¹⁸O values (−5.44‰ to −7.45‰ V-PDB) illustrates dolomite cementation at higher temperatures and greater depths. The highly depleted values of δ¹⁸O (up to −9.16‰ V-PDB) and (up to 0.42‰ V-PDB) for δ¹³C of saddle dolomite (SD-I) indicate the precipitation of SD-I as a cavity filling dolomite at considerable depth. Calcite cementation and calcitization actively participated in the early, middle, and late diagenetic modifications as interpreted from their petrographic and stable isotopic studies. Porosity enhancement is clearly demonstrated by dissolution, stylolization, fracturing, and replacement dolomitization. Dolomite and calcite cementation had a negative impact on the reservoir character and occluded the dolostone porosity to a greater extent. Full article

A diamond plate cut out of a transparent, colorless octahedral diamond crystal of gem quality, with a small chromite inclusion in the core, sampled from the XXIII CPSU Congress kimberlite (Yakutia, Mirny kimberlite field, vicinities of Mirny city), has been studied by several combined methods: absorption spectroscopy at different wavelengths (UV-visible, near- and mid-IR); photoluminescence, cathodoluminescence, and Raman spectroscopy (local version) and lattice strain mapping; birefringence in cross-polarized light; and etching. The diamond plate demonstrates a complex growth history consisting of four stages: nucleation and growth to an octahedron → habit change to a cuboid → habit change to octahedron-1 → habit change to octahedron-2. The growth history of the diamond records changes in the crystallization conditions at each stage. The revealed heterogeneity of the crystal structure is associated with the distribution and speciation of nitrogen defects. The results of this study have implications for the information value of different techniques as to the diamond structure defects, as well as for the as yet poorly known evolution of the subcontinental lithospheric mantle in the Siberian craton, recorded in the multistage growth of the diamond crystal. At the time of writing, reconstructing the conditions for each stage is difficult. Meanwhile, finding ways for such reconstruction is indispensable for a better understanding of diamond genesis, and details of the lithosphere history. Full article

Copper content in copper smelter slag exceeds that in copper ores, which has attracted increasing interest to recover copper from this by-product of pyrometallurgical copper production. The isopropanol-sulfuric acid-ozone system has been tested under different conditions to extract this metal from copper smelter slag containing chalcopyrite as a copper mineral. Isopropanol as a solvent played a key role in increasing the copper recovery to 87% after 5 h of leaching, while the use of an aqueous solution of sulfuric acid allowed only 13% of copper to be recovered. Iron extraction under these conditions was only 10%. The role of ozone was spectroscopically proven to oxidize ferrous ions to form ferric ions, which are effective oxidizers of chalcopyrite. The presence of copper in solution in the form of cuprous (Cu⁺) ions was proven electrochemically. The increased copper extraction in the solution was caused by the stabilization of cuprous ions by isopropanol. The limiting stage of the process was the chemical reaction on the chalcopyrite surface with the activation energy of 73.4 kJ mol⁻¹. Full article

Paleoproterozoic tectonic evolution of the northern North China Craton has been a hot research topic. We firstly identified a 1.85 Ga hornblendite from the Gaositai mafic–ultramafic complex, in northern Hebei. Systematic studies of petrology, zircon U-Pb geochronology, and in situ mineral major and trace elements of hornblendite are the key to revealing the petrogenesis of the Paleoproterozoic ultramafic rock and the tectonic evolution of northern North China Craton. LA-ICP-MS zircon U-Pb dating suggests the Gaositai hornblendite formed at 1851 ± 44 Ma. The late Paleoproterozoic ultramafic rocks, together with coeval post-collisional granites, formed a bimodal igneous assemblage. Both hornblende and its equilibrium melt compositions show strongly fractionated HREE patterns, relative enrichments in LREEs and LILEs, and depletions in HREEs and HFSEs. The phlogopite-bearing hornblendite magma could have originated from a hydrous garnet-facies mantle source metasomatized by slab-derived silicate melt. Furthermore, the variations of major and trace elements in hornblende from core to rim also reveal the mineral fractional crystallization and magma recharge. Zircon trace elements, melt composition equilibrium with hornblendes, and the bimodal igneous assemblage suggest that the generation of the Gaositai Paleoproterozoic hornblendite was likely the product of post-collisional extension related to the collision between eastern and western North China blocks. Full article

Determining absolute ages of orogenic faults is critical to understanding the deformation process in the upper crust, but obtaining age remains a problem due to the lack of readily available techniques. Carbonates occur as veins in faults in a range of geological settings, and thus it is a suitable mineral for U-Pb geochronology. Here, we apply the new approach of U-Pb dating on syn-tectonic dolomite veins from the Gelouang gold deposit in the western Qinling Orogen to unravel the absolute timing of the fault formation shedding new light on the regional upper crustal deformation archive. In situ LA-ICP-MS U-Pb dating of dolomite yielding a successful age of 115–112 Ma demonstrates that the dolomite precipitated coeval with tectonic events ascribed to the post-orogenic deformation phase in the Qinling Orogen. This event is possibly correlated with broader intracontinental processes and might be an inevitable response to the extensional deformation of the Qinling Orogen. The presented LA-ICP-MS dolomite U-Pb age successfully represents the age of a specific structure that encompasses the intracontinental process in the Qinling Orogen. Moreover, it demonstrates the utility of the method to decipher a response to complex deformation histories on a regional scale. Full article

Tectonic events caused by paleoearthquakes are reflected in sediments. Outcrops and cores from the Chang-7 Member of the Late Triassic Yanchang Formation, Ordos Basin in Northern China, yield a wide variety of soft-sediment deformation structures (SSDSs), many of which are laterally extensive for more than 150 km. They include various types of folds, soft-sediment liquefaction flow deformation (liquefied sand dyke, liquefied breccia), gravity-driven deformation (load structures, ball-and-pillow structures), hydroplastic deformation (loop bedding, convolute deformation), and brittle deformation (intrastratal and stair-step faults, cracks). In most cases, deformation resulted in hybrid brittle-ductile structures exhibiting lateral variation in deformation style. These occur in delta front to semideep-to-deep lake sands and mudstones (shales). The seismites recognized in outcrops and cores indicate earthquakes with magnitudes (Ms) between 6 and 8, which are interpreted as a response to orogenic events related to the collision of the South China Block (SCB) and North China Block (NCB) during the Late Triassic period. Systematic study of the spatial and temporal distribution of these seismites improves the understanding of the tectonic context and evolutionary history of sedimentary basements. This study can provide a new perspective on the evolution of tectonic activities in the basin. Full article

Iron oxide-apatite (IOA) deposits are important sources of iron. The role of evaporite layers in the formation of IOA ore deposits remains controversial. The Luohe deposit in eastern China and the El Laco deposit in Chile are representative IOA deposits. In this study, the S isotope characteristics of these two deposits are revisited. The formation of the Luohe ore deposit is closely related to marine evaporite layers in the Middle Triassic Dongma’anshan Formation. At Luohe, most of the sulfides and sulfates have high δ³⁴S_V-CDT values (concentrated from 6‰ to 10‰ and 16‰ to 20‰, respectively). The δ³⁴S_V-CDT values of sulfates are similar to those of marine evaporite layers (28–30‰) in the Dongma’anshan Formation. Estimates show that 46–82% of sulfur in the Luohe deposit is derived from marine evaporite layers. Unlike the Luohe deposit, the El Laco ore deposit formed in close relation to terrestrial evaporite layers from the Cretaceous-Tertiary Salta Group. At El Laco, the sulfides and sulfates have lower δ³⁴S_V-CDT values of −2.3‰ to −0.9‰ and 6.8‰ to 10.5‰, respectively. The δ³⁴S_V-CDT values of sulfates from the El Laco deposit are similar to those of sulfates from terrestrial evaporite layers (9.5‰) in the Salta Group. Estimates reveal that more than 70% of sulfur comes from terrestrial evaporite layers. These results indicate that evaporite layers have been involved in IOA ore-forming systems of both hydrothermal and magmatic deposits. Evaporite layers are proposed to have played key roles in the ore-forming processes of the Luohe and the Laco deposits and in other IOA deposits elsewhere. Full article

Quartz is one of the most abundant minerals. Used in a variety of materials, it preserves geological history and reflects alteration conditions. Data were collected (>2400 data points) from more than 40 ore deposits to understand its internal texture and geochemistry. Cathodoluminescence imaging is a technique for examining the internal texture of quartz that may reveal information about the crystal’s origin and evolution. The dominant trace elements in quartz lattice are Al, P, Li, Ti, Ge, K, and Na. These, combined with internal texture, can distinguish quartz from different origins and can differentiate between different types of ore deposits, as each type of ore deposit has its own unique CL characteristics. Therefore, Al did not correlate with cathodoluminescence (CL) in epithermal Au-Sb-Hg, Carlin-type Au, epithermal Ag, or shale-hosted Zn deposits. Epithermal base metal and porphyry-Cu-type deposits were intermediate, and Mississippi-Valley-type, epithermal Au-Ag, and porphyry Cu-Mo deposits were characterized for Al correlation with CL. Furthermore, Gigerwald, Rohdenhaus, and Westland deposits had Li/Al ratios less than one, suggesting that H (as hydroxyl substituting for oxygen) completed the charge. However, trace elements (i.e., Ge, Sb, Ti, and Al), sector zoning, and resorption surfaces were vital parameters to differentiate between magmatic and hydrothermal quartz. Additionally, titanium and aluminum were the most important trace elements. Their values could be used to differentiate between different quartz types. Among them, hydrothermal and pegmatitic quartz were characterized by lower temperatures and Ti concentrations. Rhyolitic quartz was characterized by the lowest Al, the highest temperatures, and lower Al/Ti ratios. Aluminum, Li, and H were most important in hydrothermal and metamorphic quartz, but magmatic quartz was generally enriched with Ti. Full article

Intimate knowledge of the mineralogical assembly of the Yushui complex ore rich in Cu, Pb, and Ag is essential if efficient separation processing is to be conducted. With the aid of testing instruments, such as scanning electron microscope (SEM), X-ray diffractometer (XRD), and mineral liberation analyzer (MLA) combined with energy-dispersive X-ray analysis (EDX), the texture, such as the size distribution, dissemination, and association of the minerals, was investigated. The results demonstrate that the ore consists of 35 categories of minerals, assaying Cu 7.99%, Pb 9.39%, and Zn 1.96% in the forms of chalcopyrite, galena, and sphalerite, respectively, and silver assaying 157.9 g/t is closely associated with these sulfides; sulfides are present in amounts of 80.31% of the total, traditional gangues only 19.69%, and pyrite as a Cu-Pb-Zn-Ag carrier mineral up to 44.80%. According to the characteristics of the ore, the innovative process of flash copper flotation in weak acidic pulp and lead flotation, followed by further copper recovery, was developed. The closed-circuit test shows that copper concentrate assays Cu 16.33%, Pb 7.98%, Ag 242 g/t at Cu recovery of 86.67%; lead concentrate contains Pb 46.23%, Cu 3.75%, Ag 165 g/t at Pb recovery of 56.84%; total recovery of silver in both concentrates is 75.57%. Full article

The evolution of the eastern Paleo-Asian Ocean (PAO) has controlled the formation of the southeastern Central Asian Orogenic Belt (CAOB). However, the evolution history and final closure time of the eastern PAO still remain controversial, which greatly restricts understanding of the formation process of the CAOB. To address these issues, we provide detailed zircon chronology and Hf isotope and geochemical data of Paleozoic to Triassic magmatic rocks in the southeastern CAOB. We have identified four periods of magmatism as evidenced by: Early Silurian quartz diorites (434.7 Ma), Early Devonian monzogranites (394.2 Ma), Middle Permian granites (260.2–264.5 Ma) and Late Permian-Early Triassic syenogranite (250.8–253.6 Ma). These rocks have features of low MgO and mantle-compatible elements, are enriched in Th, U, K, Pb, Sr, Zr and Hf and depleted in Nb, Ta, La, Ce, P, and Ti. The quartz diorites belong to the medium-K calc-alkaline series with εHf(t) values of −0.76 to 2.21, indicating that they may be derived from partial melting of mafic lower crust with minor contribution of mantle magma. The monzogranites and syenogranite have high Zr + Nb + Ce + Y (260–390; 261–461 ppm, respectively), total alkali contents (9.98–10.80; 8.46–9.29 wt.%, respectively), and high zircon saturation temperature (807–840; 810–885 °C). They can be classified as A-type granites. Monzogranites have εHf(t) values (between −1.20 and +3.34); hence, we believe that they were derived from the crust modified by mantle-derived fluids or melts. Syenogranite have high εHf(t) values (5.49–11.36), and we suggest that they were derived from the juvenile lower crust that originated from the depleted mantle. The granites have high Sr/Y ratios (118–257), low Y (1.42–2.82 ppm), and Yb (0.31–0.41 ppm), consistent with the features of adakite. Considering the εHf(t) isotopic values (2.99–8.50), we suggest that they originated from thickened juvenile lower crust. Combining the results from our own and previous studies, we propose a new evolution model of the eastern PAO from Paleozoic to Triassic. It can be divided into two stages: (1) Late Cambrian to Early Devonian; (2) Early Permian to Triassic. The first stage is the evolution of the Bainaimiao ocean (secondary ocean basin of the PAO), which closed in the Late Silurian and led to the Bainaimiao arc accretion to the North China Cratons. The second stage is the final closure of the eastern PAO during the Late Permian (~254 Ma). Full article

The origin of Middle Jurassic evaporites in the Qamdo Basin is still controversial because palaeontological studies have reported that they have both marine and continental characteristics. The ⁸⁷Sr/⁸⁶Sr ratios of the gypsum in the Middle Jurassic Dongdaqiao Formation in the Qamdo Basin range from 0.707602 to 0.708163, which are higher than that of contemporaneous seawater. Model calculations suggest that continental water prevailed over seawater during the precipitation of these evaporites. However, the majority of the gypsum samples have δ³⁴S values of 15.3‰ to 16.3‰, which are consistent with that of contemporaneous seawater. This range of values (15.3‰ vs. 16.3‰) was likely caused by S isotope fractionation during evaporation because the δ³⁴S values and Sr contents are negatively correlated. The δ³⁴S values of the other three gypsum samples are 20.0‰, 20.5‰, and 20.8‰, which are significantly higher than that of Middle Jurassic seawater. The trace element compositions and scanning electron microscopy (SEM) observations indicate that these elevated δ³⁴S values were caused by bacterial sulphate reduction (BSR). The Sr and S isotope systematics of the gypsums from the Dongdaqiao Formation demonstrate that the parent brines from which the evaporites precipitated were marine based with a large quantity of continental input. A comparison of the lithologies and Sr isotope compositions of the Middle Jurassic sequences in the Qamdo and Qiangtang Basins revealed that the Qiangtang Basin was mainly recharged by Jurassic seawater, while the Qamdo Basin was primarily recharged by continental water with some seawater-derived overflow from the Qiangtang Basin. Full article

Coal mine reuse involves complex environments such as chemical erosion and dynamic perturbation. Therefore, the effect of chemical erosion on the dynamic behavior of the red sandstone was studied by split Hopkinson pressure bar (SHPB) tests under the strain rates of 70~125 s⁻¹. The full-field deformation of the sample was then recorded through high-speed 3D digital image correlation (3D-DIC) technique. The dynamic deformation characteristics, especially the lateral strain, were extracted by averaging the lateral strain field by pixels. Also, the fracture behavior was investigated based on the evolution of strain localization in the strain field. The results indicated that the deformation field evolution of the sample is controlled by the chemical erosion effect and the loading strain rate. The chemical erosion lowers the stress threshold for strain localization and accelerates its expansion rate, which is closely related to the dynamic strength degradation of the sample. In contrast, the loading strain rate increases the dynamic strength but advances the occurrence of strain localization and shortens the time to the peak stress. The normalized stress thresholds for the initiation and development of cracks inside the sample under dynamic loading are reduced by chemical erosion, with the two thresholds dropping to 10%~30% and 20%~70% of the peak stress, respectively. The minimum thresholds for the initiation and development of cracks inside the red sandstone under dynamic loading are 11% and 24% of the peak stress, respectively. Full article

Innovation has an important role in improving the productivity, safety and sustainability of mining operations. Historically, ore transport was done by diesel trucks, but with the commitment to reduce CO₂ emissions and increase mine safety, mining companies have invested in innovative, more sustainable ore transport technologies. The innovative truckless system, with the intensive use of belt conveyors to transport the ore from the mine to the processing plant, represents a huge project and capital investment. However, operation costs are lower when considering the decrease of fuel use and also maintenance expenses. This paper presents an economic analysis of a mine-to-crusher model to estimate and minimize the operating expenses of an open-pit iron mine located in northern Brazil. The activities at this truckless mine consist of drilling and blasting, loading and primary crushing. In this study, the calibration of the mine-to-crusher model was based on rock fragmentation from the blasting phase. The costs of each mine operation phase were estimated for an optimum 80% passing size (P₈₀). The calibration was conducted with the values of technical and economic parameters in 2019. By considering the structural lithologies of canga and jaspillites, we concluded that the P₈₀ value that minimizes costs might be in the range from 0.31 to 0.34 m. Full article

Cemented paste backfill (CPB) is a sustainable mining method that has been increasingly utilized. Demand for high-performance and low-cost binder material is one of the limitations in CPB utilization. This work aims to examine a new, green, and economical steel-slag-based binder for CPB and to explore valorization techniques of steel slag (SS). Proportioning experiments were performed to obtain the best binder recipes for various steel slag dosages. The hydration heat, hydration products, and pore structure of a high-volumetric steel slag binder (H-SSB) were further inspected. Results show that the H-SSB, which contains 50 wt.% of SS, has a competitive strength performance superior to ordinary Portland cement (OPC) regardless of its 30–50% lower cost than OPC. The 7-day and 28-day strengths of H-SSB CPB are 1.24 and 0.74 MPa, respectively, which meets the meets of most free-standing backfill applications. The H-SSB generates less hydration heat and a larger amount of gel and ettringite hydrates than OPC in its early hydration, which can reduce the thermal expansion risks and strengthen the mechanical properties of CPB. Though the H-SSB CPB has a larger porosity than OPC-CPB at 28-day curing (45% vs. 37%), most pores are small and uniform in diameter (500–2000 nm), which is less harmful to CPB strength development. The H-SSB has secondary hydration effects in the long-term age, which can fill and refine the pore structure. The proposed H-SSB has benefits in reducing backfill costs, minimizing green gas emissions, and extending steel slag valorization techniques that can promote sustainable development of the mining and steel industries. Full article

The Heilongjiang Duobaoshan area is located at the confluence of the Great Xing’an Range and the Lesser Xing’an Range, and the area has undergone a complex magmatic and tectonic evolutionary history resulting in a complex and diverse geological background for mineralization. As a result of this geological complexity and the multi-period nature of mineralization, the geochemical data of the area are usually not satisfied with a single statistical distribution form, so traditional statistical methods cannot adequately explore and identify the distribution of deep-seated information in the geochemical data. Based on the above problems, this paper adopts a multivariate component data analysis method to process 14 mass fraction data elements, namely Ag, As, Au, Bi, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, W, and Zn, in the 1:50,000 soil geochemical data from the Duobaoshan area of Heilongjiang. The spatial distribution and internal structural characteristics of raw, logarithmic transformation and isometric logarithmic ratio (ILR) transformed data were compared using exploratory data analysis (EDA); robust principal component analysis (RPCA) was applied to obtain the PC1 and PC2 principal component combinations associated with mineralization, and a spectrum–area (S–A) fractal model was further used to decompose the geochemical anomalies of the PC1 and PC2 principal component combinations as composite anomalies. The results show the following: (i) The data transformed by the isometric logarithmic ratio (ILR) eliminate the influence of the original data closure effect, and the spatial scale of the data is more uniform; the data are approximately normally distributed, based on which RPCA can be applied to better explore the correlation between elements and the pattern of co-associated combinations. (ii) The S–A method was further used to decompose the composite anomalies of the PC1 and PC2 principal component combination in the study area. The anomalous and background fields of the screened-out PC1 and PC2 principal component combinations reflect anomalous information on mineralization dominated by Au mineralization. Moreover, the anomaly and background information after extraction were in good agreement with the known Au deposits (points), and many geochemical anomalies with prospecting potential were obtained in the periphery, providing a theoretical basis and exploration focus for the next step in the searching and exploring of the study area. Full article

The submarine camera system is one of the most effective detection methods for detecting seabed hydrothermal sulfide. The position fixing of camera equipment is generally achieved by the ultra-short baseline (USBL) positioning systems. The dynamic changes in the marine environment and the loss of acoustic signals lead to many abnormal points in the USBL positioning data. The existing methods cannot perform position fixing correction for USBL positioning data with many scattered abnormal points. This paper selects and focuses on the seabed camera data of the XunMei mineralization area acquired from the China South Atlantic voyage and employs the DTW optimization algorithm to solve this problem. This method is implemented based on Python language and an ArcGIS technical environment, and a total of 97,469 topographic profiles with 10 m spacing are extracted from the topographic data of the object area with 1m accuracy. Moreover, the highest similarity (95.9%) is obtained between the bathymetric profile of the camera survey line and the above topographic profile. The results indicate that the proposed algorithm is fast and effective, and the positioning correction accuracy of the deep-sea near-bottom camera data can reach the meter level (determined by the topographic data accuracy). Moreover, the solution can provide services for accurately position fixing near-bottom exploration equipment and its exploration data. It can also solve the problem of underwater position fixing problem that a GPS cannot solve. Full article

This paper demonstrates that intercalating Na⁺ homoionic vermiculite with Fe³⁺ polyhydroxy cations (1:1 molar ratio OH⁻ to Fe³⁺) significantly improved the affinity of the clay mineral-based sorbent toward phosphate. Kinetic experiments revealed that adsorption is fast, approaching an equilibrium within about 200 min of contact time, and that the rate-limiting step is the intraparticle diffusion. Adsorption isotherms fitted to the Freundlich equation and a two-site Langmuir model, consistent with the heterogeneity of adsorption sites. The separation factor derived from the Langmuir constant revealed that the adsorption was favorable and even irreversible for high-affinity minor adsorption sites. The adsorption capacity was 299 ± 63 μmol g⁻¹ (9.3 ± 2.1 mg P g⁻¹), a value similar to several other clay-based phosphate adsorbents. Application to reservoir water spiked with 10 mg L⁻¹ in P removed about 71% of the available phosphate. Full article

In order to clarify the mechanical properties and energy changes of coal samples under the influence of mining depth, a mechanical test analysis method to determine that the increase in mining depth increases the loading rate has been developed. Taking the Wudong Coal Mine as an example, a mechanical test analysis of coal samples is carried out. The results show that the surface deformation and failure of coal samples in the loading process presents four stages. That is, the evolution process of ‘complete coal sample’–‘partial failure-failure extension’–‘overall instability’. The maximum temperature of a coal sample when it is destroyed shows an obvious nonlinear increasing trend with the increase in loading rate. With the increase in loading rate, the strength and elastic modulus of coal samples decrease gradually. The cumulative total energy and elastic energy of coal samples are linearly positively correlated with the loading rate. The research results provide ideas for rational control of mining intensity and determination of productivity in steeply inclined thick coal seams for deep mining. Full article