Ore Deposits Research Articles

High temperature transformations and thermal expansion of halotrichite FeAl<sub>2</sub> (SO<sub>4</sub>)<sub>4</sub>⋅22H<sub>2</sub>O

Halotrichite is a widespread mineral in post-volcanic environments and oxidation zones of ore deposits. Halotrichite is stable at temperature up to 70 °C; further heating leads to the formation of an X-ray amorphous phase I. There are reflections of millosevichite (prevailing) and mikasaite appearing in the range of temperatures 340–660 °C. Millosevichite and mikasaite are decomposing at temperatures 660 °C with the formation of an X-ray amorphous phase II. According to data of the synchronous thermal analysis, the transition from halotrichite into anhydrous sulfates is accompanied by the loss of H2O molecules, which makes about 42.9 wt %, the transition to the X-ray amorphous phase II is caused by the loss of SO3, which is ca. 37.4 wt %, associated with two endothermal effects. The thermal expansion of halotrichite is sharply anisotropic, the maximum expansion is determined by the shear deformations of the lattice in its monoclinic plane along the bisectrix of the obtuse angle β, and the minimum one – in the direction of strong S–O–Fe bonds inside [Fe(SO4)(H2O)5]0 complexes. The significant volumetric expansion of halotrichite (9(3)∙10-5 ºC-1) occurs due to the determing role of hydrogen bonds in composition of the crystal structure.

Study of Galena Ore Powder Sintering and Its Microstructure

Galena is a natural mineral enriched with lead sulfide (PbS). It typically forms in hydrothermal veins associated with igneous rocks and can also occur as a gangue mineral in other ore deposits. PbS is of special importance for scientific research applications due to the possibility of tuning its semiconductor energy gap using nanotechnology in conjunction with powder metallurgy as an easy, controllable production route. In this paper, almost pure PbS was successfully produced starting from a high ratio of PbS phase galena ore. As-received galena lumps were roughly pulverized and milled to produce four particle size ranges of 38, 63, 125, and 250 µm prior to compaction and sintering in a vacuum (pre-flushed with argon gas). SEM coupled with the EDAX analysis unit was employed to investigate the microstructure and chemical composition of the as-received galena and the subsequent products after sintering. The chemical analysis confirmed the high ratio of PbS compound in the as-received galena and sintered products with approximately 85% Pb and 13% S mass ratio. The sintering process of the galena powder was carried out at different values of temperature, time, and compaction pressure. Additionally, the effect of length to diameter ratio of compacted and sintered samples was investigated. XRD analysis confirmed the existence of the PbS phase in the as-received and sintered samples at 700 °C with approximately 98 wt.%, as well as a new phase that is formed at 800 °C with a lower percentage. The micro-hardness of the as-received and sintered samples was measured and compared with the as-received galena ore. The results showed a significant reduction in the hardness of sintered galena powder compared with the bulk as-received galena by 52%. Furthermore, a relative sintered density of 99.3% for the as-received galena density signifies a novel result using powder metallurgy techniques.

“Hidden” mineralogical-geochemical zonality revealed by the laser microanalysis of sulfides at the Kyzyk-Chadr deposit, Republic of Tyva

A comprehensive study of the Kyzyk-Chadr porphyry copper deposit included determination of the composition and spatial distribution of trace elements in ore-forming sulfide minerals over the ore- hosting rock volume. The study was carried out using the mass spectrometric analysis with laser ablation of the analyzed material. Steady qualitative and quantitative elements of a “hidden” mineralogical and geochemical zonality have been identified, that are expressed in variations in the concentration of trace elements and their ratios in pyrites and chalcopyrites over the volume of the ore-bearing porphyry copper stockwork. The identified regularities correlate with the established centrifugal vector and concentric pattern of the mineralogical ore-metasomatic zonality of the ore deposit.

Carbon and water footprint of battery-grade lithium from brine and spodumene: A simulation-based LCA

Increasing demand for lithium driven by e-mobility spurs the expansion of lithium projects and exploration of lower-grade resources. This article combines process simulation (HSC Chemistry) and life cycle assessment tools to develop life cycle inventories considering declining ore grades scenarios for battery-grade Li2CO3 production from pivotal sources and regions (Salar de Atacama - brine and Greenbushes - spodumene). Depending on the ore grades, climate change results range from 5,0 to 25,0 kgCO2eq/kg Li2CO3 for brine and from 17,1 to 22,3 kgCO2eq/kg Li2CO3 for spodumene. Water consumption for brine varies from 0,2 to 7,7 m3/kg Li2CO3, depending on flow accounting, while for spodumene, it ranges from 0,2 to 0,5 m3/kg Li2CO3. The research shows that decreasing ore grade can lead to a fivefold increase in the carbon footprint for brine-based production and a 1.3-fold increase for spodumene. This underscores the importance of decarbonizing energy provision for lithium production to guarantee a sustainable battery supply chain. This research offers insights into using process simulation to enhance existing LCA studies in the raw materials industry and further develop inventory datasets, considering variations such as deposit ore grades.

Geological and isotopic reference points of the age of gold deposits of the Solovyovsky gold ore center in the Amur province

The data are presented on the geological and isotopic age of gold deposits of the Solovyovsky gold ore center in the Amur province, assigned to the gold-polymetallic, gold-sulfide-quartz, and goldquartz formation types. It is demonstrated that the geological and isotopic age of the most productive ore deposits of the gold-polymetallic (Berezitovoe) and gold-sulfide-quartz (Kirovskoe) types is Early Cretaceous according to geological data and Barremian (in the range of 131–125 million years) according to isotopic determinations. The geological age of poorly productive ore deposits of the gold-quartz type is difficult to determine due to the fact that the host rocks are most often represented by gneisses and crystal shales of Precambrian age. The isotopic age of formation of the Snezhninka and Zolotaya gora gold-quartz deposits is, respectively, Late Triassic (212 million years) and Late Jurassic (155 million years).

High-precision microcline 40Ar/39Ar dating by combined techniques

K-feldspar is one of the most common minerals applied for 40Ar/39Ar dating because of its high K content and ubiquitous presence. Excess 40Ar in K-feldspar resulting in unreliable ages has long been reported, however, its occurrence and trapping time are still inconclusive. Combined argon extraction techniques, including laser step heating, and step crushing, as well as succedent furnace incremental heating, have been applied to six microcline samples from two hydrothermal ore deposits in South China, to address these issues. Two microcline samples (09SZ37 & 39) measured by all the above three gas extraction techniques yield flat age spectra and concordant inverse isochron ages respectively. However, one sample (09NL10) produces a flat spectrum but with abnormally low radiogenic 40Ar, and the other three samples obtain uneven age spectra, by laser heating. All six samples measured by step crushing yield quite similar age spectra characterized with declining staircases for the first several steps, and followed with very flat plateaus of high-precision plateau ages for the subsequent later crushing steps. The declining sections with abnormally old ages indicate that excess 40Ar (and obvious atmospheric argon) was trapped in the microcracks and the secondary fluid inclusions. The data points corresponding to age plateaus well define inverse isochron ages which are in consistence with their plateau ages respectively. Furthermore, the crushed powders of all six samples by further furnace step heating also yield very flat age spectra, whose plateau ages are well concordant with those obtained by the foregoing step crushing experiments. The trapped excess 40Ar caused the total fusion ages of laser heating 0.7–17.8% older than their true ages. Mineral grains of ca. 0.10 mm may effectively remove excess 40Ar in microcracks and secondary fluid inclusions, proposed for direct 40Ar/39Ar step heating. Stepwise crushing, combined with furnace heating, is not only very useful to date fluid inclusions, but also robust to remove excess 40Ar and obtain more precise true ages for K-bearing minerals, e.g., K-feldspar, amphibole, tourmaline, and so on.

Indian ore deposits: current genetic understandings

Indian ore deposits: current genetic understandings

Pyrite geochemical fingerprinting on skarn ore-forming processes: A case study from the Huangshaping W–Sn–Cu–Pb–Zn deposit in the Nanling Range, South China

Pyrite geochemistry has been extensively used to reveal ore-forming processes in diverse ore deposits, but its application in skarn systems is not well understood. The Huangshaping deposit in the Nanling Range (South China) uniquely develops W–Sn–Pb–Zn and Cu–Pb–Zn skarn mineralization systems, and both two systems have formed multi-types of pyrite, which provides a good window to reveal the mineralization histories of different skarn systems using pyrite trace element geochemistry. In the Cu–Pb–Zn system, texturally homogeneous Py1 mainly occurs in calcite veins within the host rock, whereas texturally homogeneous Py2 in the calcite-sulfide stage mainly occurs in skarn orebodies. Py3 in the siderite-sulfide stage replaces Py2 and commonly develops abundant pores or fractures, resembling the “bird's eye” texture. In the W–Sn–Pb–Zn system, Py4 in calcite veins can be divided into the oscillatory-zoned Py4a and irregular Py4b under BSE, and Py4b commonly replaces Py4a as veins or overgrowth. Texturally homogeneous Py5 in the calcite-sulfide stage occurs in skarn orebodies and is replaced by Py6 with a “bird's eye” texture in the siderite-sulfide stage.In the Cu–Pb–Zn system, Py1 may have formed by fluid cooling during its ascent along the hydraulic fractures indicated by its enrichment of Co, Ni, As, Sb, and Tl, whereas Py2 is likely formed under higher temperature and pH conditions caused by intense fluid-rock interactions evidenced by its depletion of Co, Ni, As, Sb, and Tl as well as its enrichment of Zn and Ag. In the W–Sn–Pb–Zn system, Py4b has higher contents of Co, Ni, As, Sb, and Tl than Py4a and similar contents of Ag, Zn, and Mo with Py4a, suggesting that decreasing temperature may have controlled the formation of Py4b. Py5 is featured by the depletion of As, Sb, Tl, and Mo as well as the enrichment of Zn and Ag, indicating that Py5 is likely formed under higher temperature and pH conditions resulting from the intense fluid-rock interactions. Marcasite replaces pyrrhotite and then is replaced by pyrite may be an important precipitation mechanism for pyrite with a “bird's eye” texture (Py3 and Py6) in both two skarn systems at Huangshaping. This study demonstrates that fluid-rock interaction is an important mechanism for sulfide precipitation at Huangshaping, which shows that pyrite geochemistry has good potential to reveal mineralization histories in skarn systems.

Silicate melt immiscibility as the cause of large-scale rare-metal mineralization in a peralkaline granite system: The case of the Baerzhe deposit in NE China

The Early Cretaceous peralkaline Baerzhe pluton hosts a potentially large REE-Nb-Zr-Be deposit in inner Mongolia, northeastern China. The mechanism responsible for the extreme enrichment of rare metals and rare earth elements in the pluton is still ambiguous. This study presents new evidence for silicate melt immiscibility as the key mechanism at Baerzhe using amphibole-group minerals from spherulite granite, which contains spherulites with abundant REE- and HFSE-bearing minerals. The spherulite from the transsolvus granite is composed of two distinct zones, i.e., a dark-colored core consisting of arfvedsonite aggregates and a light-colored rim consisting mostly of quartz and feldspar, rare amphibole, and abundant HFSE- and REE-bearing minerals. Four types of amphibole (AmpI, Amp-IIa, Amp-IIb and Amp-III) from the transsolvus granite and one type (Amp-IV) from the subsolvus granite are recognized, and all of them are magmatic fluoro-arfvedsonite. The earliest phase consists of euhedral inclusions of Amp-I within quartz or feldspar. They show an enrichment in HREEs relative to LREEs and a depletion in medium REEs, consistent with the REE pattern controlled by the mineral lattice. This implies that Amp-I likely formed in an initial homogeneous mel relatively depleted in REEs; thus, the mineral structure played a dominant role in REE partitioning. Compared with other types of amphiboles, Amp-IIa and Amp-IIb from the spherulite phase display the highest REE contents, with flat LREEs and MREEs and a slight upward HREE pattern. Combined with the significant accumulation of REE- and HFSE-bearing minerals in the rim zone, differences in REE patterns among different amphibole types imply that the spherulite crystallized in a volatile-rich silicate melt and was probably the product of silicate melt immiscibility. Interstitial Amp-III with lower REE contents from the matrix phase crystallized in the separate volatile-poor silicate melt. The Amp-IV from the subsolvus granite has the lowest CaO content, with strong depletion in LREEs relative to HREEs, suggesting a more evolved melt composition. It is concluded that silicate melt immiscibility may serve as an important key mechanism that occurred in the early stage of magmatic evolution, resulting in the enrichment of REEs and HFSEs, which played a critical role in the formation of large to giant ore deposits such as the Baerzhe deposit.

Origin of fluids in the Lancangjiang tin belt, southwestern Yunnan Province, China: Evidence from trace element and boron isotopic compositions of tourmaline

The Lancangjiang tin belt is located on the eastern margin of the Tibetan Plateau, which is in the northern part of the Southeast Asian tin belt that contains Sn, W, and base metal ore deposits. Tourmaline alteration and high B contents are typical features of the magmatic–hydrothermal systems in the Lancangjiang tin belt. Our new data for tourmaline intergrown with cassiterite reveal complex geochemical features that provide important insights into the origins of ore-forming fluids in this B-rich tin belt. Most of the tourmaline in the Sn deposits and metamorphic rocks belongs to the alkali-group dravite series, except for some that is part of the X-vacant group. The tourmaline compositions differ among the ore districts, but all exhibit Fe-poor (0.61–1.08 apfu) and Mg-rich (1.43–2.06 apfu) compositions, with Fe/(Fe + Mg) = 0.18–0.46. Most trace elements in the tourmaline occur at low contents (<50 ppm), including the large-ion lithophile elements (e.g., Cs and Ba) and high-field-strength elements (e.g., Nb, Ta, Hf, and Th). However, some trace elements (e.g., Zn, Sr, and V) and Sn have high contents (up to several hundreds or thousands of ppm). The δ11B values of tourmaline from the Sn deposits range from −14.7 ‰ to −11.3 ‰, except for those in the Man Makhsan Sn deposit, which range from −12.0 ‰ to −8.1 ‰. The δ11B values (−14.7 ‰ to −8.1 ‰) and the positive correlation between Sn contents and Nb/Ta, Al/Ga, and K/Cs ratios in the ore-related tourmaline indicate that the exsolved ore-forming fluids were derived from highly fractionated S − type granitic magmas. The fluids were mainly B-, Sn-, and Al-enriched. The low Fe/(Mg + Fe) ratios, high oxygen fugacity, and Al saturation were favorable for cassiterite precipitation, and are proxies for the ore-forming potential of large-scale Sn deposits.

Application of portable multi-component gas analyzer to mineral exploration in semi-arid steppes of northern China: A case study from the Qinjiaying Ag–Pb–Zn prospect

Soil gases, particularly sulfur gases, have not been widely used in mineral exploration due to their high mobility and reactivity. However, our team developed a portable multi-component gas analyzer (PMGA) capable of on-site and real-time measurement of H2S, SO2, CH4, and CO2 concentrations in soil gas. This study showcases the applicability and effectiveness of PMGA in the geochemical exploration of concealed ore deposits in the Qinjiaying Ag–Pb prospect in semi-arid steppes. Comparison tests between different analyzers and periods were conducted in the Qinjiaying Ag–Pb prospect. The results showed that PMGA has high stability, consistency, and reproducibility. Then, soil gas geochemical surveys were carried out by applying PMGA along eight prospecting lines, with three prospecting lines passing through the known mineralized zone and the remaining five prospecting lines focusing on the covered areas. Three composite anomalies of H2S, SO2, CH4, and CO2 were identified. The No. 1 soil gas anomaly corresponds well to the known No. I mineralized zone. The No. 3 gas anomaly is characterized by large-scale and strong multi-gas anomalies, indicating the presence of great prospecting potentials. Finally, drilling verification revealed a medium-sized Ag–Pb–Zn deposit in the No. 3 gas anomaly. The results demonstrate that PMGA is a powerful tool for mineral exploration in the study area. This successful practice provides a paradigm for applying PMGA in mineral exploration in semi-arid steppes.

Biogeochemical prospecting of metallic critical raw materials: soil to plant transfer in SW Ciudad Real Province, Spain

The soil–plant transfer of trace elements is a complex system in which many factors are involved such as the availability and bioavailability of elements in the soil, climate, pedological parameters, and the essential or toxic character of the elements. The present study proposes the evaluation of the use of multielement contents in vascular plants for prospecting ore deposits of trace elements of strategic interest for Europe. To accomplish this general goal, a study of the soil–plant transfer of major and trace elements using Quercus ilex as a study plant has been developed in the context of two geological domains with very different characteristics in geological terms and in the presence of ore deposits: the Almadén syncline for Hg and the Guadalmez syncline for Sb. The results have made it possible to differentiate geological domains not only in terms of individual elements, but also as a combination of major and trace elements using Factor Analysis. The bioconcentration factors have demonstrated the uptake of macronutrients and micronutrients in very high concentrations but these were barely dependent, or even independent of the concentrations in the soil, in addition to high values of this factor for Sb. The Factor Analysis allowed for the differentiation of geogenic elements from other linked to stibnite ore deposits (Sb, S, and Cu). This element (Sb) can be uptake by Quercus ilex via the root and from there translocating it to the leaves, showing a direct relation between concentrations in soil and plants. This finding opens the possibility of using Quercus ilex leaves for biogeochemical prospecting of geological domains or lithological types of interest to prospect for Sb deposits.

International Association on the Genesis of Ore Deposits

International Association on the Genesis of Ore Deposits

Geological setting, lead-zinc mineralization characteristics and its potential prospects in the Na Bop - Pu Sap area, Cho Don, Northeastern Vietnam

The Lo Gam structural zone is recognized as a crucial area for the occurrence of lead-zinc deposits in Northeast Vietnam, encompassing the distinguished territories of Cho Dien and Cho Don. Specifically, within the Cho Don area, the Na Bop-Pu Sap area emerges as particularly noteworthy owing to the considerable scale and quality of its lead-zinc ore deposits. In order to comprehensively investigate the geological attributes and lead-zinc mineralization phenomena prevalent in Na Bop-Pu Sap, a suite of analytical techniques including petrographic analyses, mineralogical examinations, scanning electron microscopy (SEM), and ICP-MS were employed. Furthermore, stable isotope investigations and single mineral sphalerite analyses were conducted to assess the origin of metal constituents and the physicochemical conditions conducive to ore genesis. The Na Bop-Pu Sap area is under the influence of the NW-SE fault system, with the ore structure predominantly manifesting as bands and veins aligned parallel to the foliations of hosted rock. This configuration suggests a close association between the formation of lead-zinc ore and the foliation processes occurring within the shear zones. The assemblage of ore minerals within the region primarily comprises galena, sphalerite, pyrite, pyrrhotite, and arsenopyrite. Integration of S and Pb isotopic analyses alongside single mineral sphalerite assessments reveals that the ore-forming solutions emanate from both magmatic activity and sedimentary sources, with lead-zinc ore deposition occurring at temperatures ranging from low to medium. Projections suggest that the Na Bop-Pu Sap mining area may exhibit relative degrees of erosion extending to depths of approximately 600 meters below the existing terrain surface. This comprehensive examination of the ore characteristics in the Na Bop-Pu Sap mine area yields invaluable insights, thereby advancing our understanding of the potential for deep-seated lead-zinc mineral resources within the Northeastern Vietnam.

Spectrometric borehole logging in mineral exploration and mining

Borehole logging tools based on pulsed neutron technology are used to infer geophysical parameters such as bulk density. If fitted with a gamma-ray spectrometer, they may also measure elemental mass fractions of a variety of formation elements. Spectrometric borehole logging tools of this kind are established in the oil and gas industry. With the demand for mineral resources surging, cost- and time-efficient measurement techniques are increasingly needed in mineral exploration. Their ability to detect multiple elements that are building blocks of minerals makes spectrometric borehole logging tools popular in mineral exploration and mining grade control. In this article, the potential of the OreLog pulsed neutron gamma spectrometric downhole logging tool is demonstrated at Erzberg Mountain (Styria, Austria). Erzberg hosts the largest known siderite deposit in the world, and open-pit mining is used to extract iron ore. The aim was to obtain a more detailed and faster geochemical characterization of iron ore deposits prior to blasting. Elemental logs were acquired with highest accuracies for Fe, Ca, and Mn, followed by Si, Mg, K, and S. The tool mapped a 2D cross section of formation element concentration within a few hours, which agrees with orogenetic fault and geologic contact lines. Mineralogical information retrieved from elemental logs confirmed the interlaced mineralogy of the site. It is dominated by a carbonate body, hosting an intergrowth of Mg-rich siderite (sideroplesite) and a solid solution of dolomite/ankerite/kutnohorite. In addition to the tool's potential for enhanced real-time mining control, the benefit of continuous depth-resolved elemental logs is seen in the possibility to deduce a more refined and reliable geochemical and mineralogical model of the deposit. The information-rich data stream opens applications beyond grade control and exploration, such as data assimilation with gravity models or geologic model building.

Social License, Mine Closure, and the Exploration Geologist

Editor’s note: The aim of the Geology and Mining series is to introduce early career professionals and students to various aspects of mineral exploration, development, and mining in order to share the experiences and insight of each author on the myriad of topics involved with the mineral industry and the ways in which geoscientists contribute to each. Abstract This paper describes the potential value that can be gained when exploration geologists, early in the project life cycle, contribute to aspects of project development that have historically been outside of their purview. Increasingly strong societal pressures are being directed toward exploration and mining to ensure (1) an enduring social license to operate is in place and (2) closure and postclosure mine liabilities are fully addressed and funded. These actions are consistent with the professional and ethical obligation of caring for human and ecological well-being over both the short and long term. The roles and responsibilities of exploration geologists are evolving as a result. A singular focus on searching for and assessing the nature of ore deposits from a technical perspective has expanded to include (1) contributing to building the foundation for a social license to operate and (2) capturing increasing amounts of data and information relevant to the full mine life cycle, up to and including the closure and postclosure phases of activity. These activities are additional to the traditional geologic role of the exploration geologist and will further enhance the value of an exploration project, despite the rare transition of an exploration target to an operating mine. This expanded role is critical for aligning industry and social values, strengthening trust in the mining industry, and enhancing the appeal of the mining industry as a desirable career option.

Analytic continuation: A tool for aeromagnetic data interpretation

Extending potential-field data to vertical complex-plane slices provides opportunities, unique to analytic functions, for subsurface imaging. We begin with an existing numerical method for differentiation by integration using Cauchy's integral formula. An example from data over northern Ontario, Canada, illustrates better conditioning compared to derivatives computed using finite differences. Next, these quantities are used for analytic continuation using rational complex-series expansion (Padé approximation). This method provides stable downward continuation to distances that are significantly greater than are achievable by Taylor series and spectral methods. A synthetic test confirms that the rational approximant faithfully reproduces the magnetic response of a thin sheet. A sign reversal of the total field, coincident with the origin of the sheet, features prominently on this example. We also provide synthetic results for sheets with finite depth extent, point sources, thin slabs, and contacts. These also exhibit polarity flips near the source location. Further, these provide a template for interpreting the source geometry using the shape of the approximating function. Additional synthetic tests illustrate an automatic method for locating closely spaced random assemblages of isolated poles. We apply our methods to a deposit-scale heliborne survey over a recently discovered volcanogenic massive sulphide ore deposit in a Canadian greenstone belt. The analytically continued profile over the deposit suggests the presence of a subvertical thin sheet of unknown depth extent. This interpretation coincides with a sulphide ore body that has been previously delimited by several drill holes. Some known prospects near this deposit are also imaged on maps and profiles of the Padé approximant.

Nickel recovery in tailling from the Chromite beneficiation process in Mau Lam, Thanh Hoa by the reduction roasting-magnetic separation process

In Thanh Hoa province, large chromite ore deposits were discovered. These types of ores also contain significant quantity of nickel metal, with total nickel reserves estimated to be over three million tones. According to the practices of mining and beneficiation of these chromite ores, nickel is discarded in the waste dumps as a non-valuable metal and has not been recovered ever. Through many years of mining and processing of chromite ores, large dumps are formed to such huge volumes that can be considered as a significantly secondary resource of valuable nickel metal. Nickel exists in the form of laterite ores so that it is difficult to be recovered. Currently, there is no commercial technology available for recovery of nickel or other valuable metals from this type of raw material sources. This article presents some research results on applying the reduction calcination – magnetic separation process for recovery of nickel. In particular, some important reduction operating variables such as temperature, calcination time, fuel coal ratio, and Na2SO4 additive were investigated. From the tailing samples of the Mau Lam – Thanh Hoa chromite beneficiation process, important optimal reducing conditions have been determined including 1,1000C of reduction temperature, 8% of anthracite coal, 8% of Na2SO4 additive, and the reduction time of 90 minutes. The reduced product was finely grounded and separated at a magnetic field of 0.3T using the wet magnetic separator. At optimal operating variables, the nickel content of the final nickel concentrate was 4.02% Ni and the overall nickel recovery was 91.2%. The positive results necessarily lead to a need to continue researching the possibility of practical application to recover nickel and thus contribute to the rational utilization of mineral resources of the country.

Near-Infrared Spectroscopic Study of Biotite–Phlogopite (Mg# = 30~99): OH-Stretching Modes and Mg# Content Prediction Equation

Biotite–phlogopite minerals are a complete Mg–Fe isomorphism series of phyllosilicates. A Fourier transform infrared spectroscopy (FTIR) and electron microprobe analysis (EMPA) were conducted on end-member phlogopite, Mg–biotite, and annite samples. In the mid-infrared region, absorption peaks were observed at 460, 1000, 3680, and 3710 cm−1 in the biotite group. Samples with higher Mg content exhibited stronger peaks assigned to OH vibrations and a weak absorption peak at 810 cm−1. In the near-infrared region, combination peaks were observed near 4200, 4300, and 4450 cm−1, with wavenumbers showing a linear inverse relationship with the Mg# [=100 × Mg/(Mg + FeT)] value. For annite, combination peaks occurred at 4173, 4292, and 4439 cm−1, decreasing by 10–15 cm−1 compared to end-member phlogopite. Judging the fundamental peaks of the combination band contributes to identifying suitable near-infrared characteristic peaks for quantitative research. The 4300 cm−1 absorption peak in biotite–phlogopite was assigned to OH-bending and -stretching vibrations, making it suitable for mineral identification and Mg# estimations across all biotite groups. The 4450 cm−1 characteristic peak, assigned to Al–O-stretching vibrations and OH-stretching vibrations, is suitable for accurately predicting Mg# values in high AlVI samples. The first overtones of biotite–phlogopite appeared at 7250 cm−1, with an average factor of 1.955 between the fundamental and corresponding overtones. This study aims to refine the patterns of OH-stretching vibrations and characteristic peak shifts in the near-infrared spectral region of phyllosilicate minerals, providing data references for planetary spectroscopy and ore deposit studies.

Predicting the magnitude of technogenic earthquakes during underground mining of the Zhezkazgan ore field

Purpose. Determining a relationship between the shear/failure of the rock mass and the technogenic earthquakes caused by them during underground mining of ore deposits with the derivation of an equation for the dependence of the technogenic earthquake indicators for the conditions of the Zhezkazgan copper-ore field. Methods. The research methodology consists of studying and analyzing early research on technogenic earthquakes by the method of statistical data processing. Calculation of rock mass deformation distribution in the study area is based on numerical modeling in the Comsol Multiphysics 5.6 and MATLAB 2020 software package environment. Calculations are performed based on solving a plane problem using the Finite Element Method (FEM). Findings. Based on the transition from the failure area to subsidence and shear values of the overlying rock mass stratum, an equation for the dependence of the earthquake magnitude on the numerical values of the mass subsidence or shear has been obtained. Originality. For the first time, based on the physics and geomechanics of rock mass shear processes, empirical-analytical formulas have been obtained that make it possible to predict the technogenic earthquake magnitude during underground mining of ore deposits in the conditions of the Zhezkazgan copper-ore field. Practical implications. Preliminary predictive calculations made by the obtained formulas for the conditions of the active mine No. 31 of the East-Zhezkazgan mine, ТОО Kazakhmys Smelting, show acceptable results of magnitude value, comparable to in-situ measurements during field mining. This prediction makes it possible to pre-calculate the technogenic earthquake magnitude at the stage of designing mining operations and make appropriate scientifically sound decisions during further mining of the field.