Mining District Research Articles

Environmental and human health risks of potentially harmful elements in mining-impacted soils: A case study of the Angouran Zn–Pb Mine, Iran

The soil pollution status, levels of exposure, and potential ecological and health risks to workers and residents by potentially harmful elements (PHEs) in the Angouran mining area (Iran), the biggest Zn–Pb mine in the Middle East, were studied. To this aim, topsoil (0–5 cm) samples (n = 63) from different land-uses were analyzed for their total PHEs concentrations. Mine worker's blood analysis and in vitro digestion extractions were applied in conjunction with human health risk assessment (HHRA) to assess the potential health impacts by exposure to PHEs. The maximum PHEs total concentrations were found in the soils near the waste rock dumps. HHRA indicated that ingestion of soils may induce a non-carcinogenic risk due to As and Pb (for both age groups of children and adults), while dermal contact for children may induce the same type of risk due to Cd, and Pb. The carcinogenic risks (CRs) of As, Cd, Cr, and Ni through ingestion route were above the acceptable value of 1 × 10−4, and children may face greater health risks. The average blood Zn, Pb, and Cd levels in the mine workers largely exceeded the safe concentration for adults, while 30% of the workers were tested positive for As in blood. In vitro digestion extractions indicated that the highest bioaccessible contents of As, Cd, Pb, Ni and Zn were found for the industrial-residential and mine soils in the area, while those of Cr and Cu were observed in the agricultural use soils. This study illustrates that a combination of techniques, including geochemical analysis, in vitro bioaccessibility extractions, HHRA, and blood analysis, is a workable integrated approach for evaluating pollution and health risks in mining districts.

Orogenic magmatism along the transition Precordillera-Sierras Pampeanas, between 29° and 31° S, Argentina

New geochemical data and petrological analysis of Neogene volcanic units from the Pampean Flat Slab Segment (29°-31°SL) are presented in this contribution. Rocks were collected along a cross-section from the Western Sierras Pampeanas to the Eastern Precordillera. The outcrops delimit areas with a sub-parallel disposition to the orogenic front and main Andean regional structures. The study involves several volcanic rocks of the Formación Cerro Morado, sampled from the Huachi eruptive center and the Helvecia and Portezuelo de Los Burros mine districts, with thick lava flows and pyroclastic rocks. Lavas and breccias from several medium size outcrops near Huaco are also analyzed. To the NE, near the town of Guandacol, the Unidad Volcánica El Corral crops out. These rocks constitute the easternmost outcrops of the Precordillera in San Juan. We also studied rocks from the La Ciénaga volcano of the Sierra del Pocho Volcanic Field within the Sierras Pampeanas of Cordoba, which are the easternmost magmatic expression of the volcanic arc in this shallow subduction zone of the Central Andes.The new geochemical and isotopic data obtained from Formación Cerro Morado and lava flows belonging to the Unidad Volcánica El Corral, and its comparison with new geochemical data of the La Ciénaga volcano of the Sierra de Pocho show that these rocks result from the melting of two sources coming from two different types of crustal basements (Precordillera and Sierras Pampeanas). We found a magmatic association with similar geochemical features within the Formación Cerro Morado in Huachi region and Helvecia mine and Agua de Los Burros. It shows abundant hydrothermal fluids, which are often related to mineralization of economic interest.On the other hand, the rocks of the Formación Cerro Morado from Huaco, of the Unidad Volcánica El Corral and El Pocho Volcanic Field have a similar isotopic signature that allows us to infer the participation of the underlying Sierras Pampeanas Crust in their development. This feature leads us to interpret the continuity of the Sierras Pampeanas Basement Crust below the Western Precordillera.

Geología, alteración hidrotermal y mineralogía del sistema de vetas Sofía-Julia-Valencia, distrito minero Andacollo, Neuquén, Argentina

The Sofía-Julia-Valencia vein system, located in the Andacollo mining district in central west Argentina, is hosted by ENE-WSW oriented strike-slip faults which are the result of reactivation of normal faults affecting Carboniferous to Jurassic rocks during Upper Cretaceous-Paleogene. These veins contain a total resource of 22,900 Oz of gold with 5.5-6.7 g/t AuEq. Geologic mapping and a U-Pb age of 71±1Ma in zircon, obtained in an altered and mineralized dacitic dyke of the district, allowed to associate the mineralizing event to the Naunauco Andesitic belt magmatism (Upper Cretaceous-Paleogene) and to the Cretaceous-Paleogene Metallogenic Belt of the Andes in southwestern Argentina. The ore bodies are made up of multiple veins and veinlets that, from oldest to youngest, correspond to: (1) scarce early quartz+pyrite+molybdenite+iron poor-sphalerite veinlets, (2) quartz+epidote+calcite±albite (apatite+rutile+titanite+light rare earth elements bearing phosphates) associated with quartz+biotite, epidote (actinolite)+chlorite+calcite, with pyrite+pyrrhotite±chalcopyrite±(iron rich-sphalerite), marcasite veins. These veins are cut and reopened by (3) polymetallic veins and veinlets formed by quartz+sericite±carbonates (chlorite), with iron-gold rich sphalerite+silver rich-galena+chalcopyrite+pyrite, native gold±arsenopyrite±(pyrrhotite, bornite, argentite). Pyrite (4) and (5) carbonate+framboidal pyrite veinlets cuts all the previous ones. Multistage carbonate generation brecciate and cut previous veins and veinlets. Quartz shows granular, comb textures and some calcites developed platy textures. Four hydrothermal alteration types affected the veins host rock: (1) patches of early potassic alteration; (2) widespread propylitic alteration with disseminated sulfides; (3) later phyllic alteration overlapped to the previous ones; and (4) late supergene alteration. The sphalerite and chlorite composition in the veins (1 and 2) along with their mineral assamblages indicates they were formed by initially alkaline fluids (e.g., feldspar stable) with intermediate sulfur and oxygen fugacity and mesothermal temperature conditions (~400-240 °C), that evolved to conditions of lower sulfur (e.g., pyrrhotite stable) and oxygen fugacity, temperature

Structures, deformation history and dynamic background of the Qianyingzi Coal Mine in the Huaibei Coalfield, eastern China

The Qianyingzi Coal Mine is located in the west of the Suxian Mining District of the Huaibei Coalfield, eastern China. The study on structural development patterns and genetic mechanisms in this mine lays an important foundation for safe and efficiently underground mining, and is also the key to understanding the regional tectonic evolution. In this study, based on the analysis of three-dimensional seismic, drilling and underground measured data and regional tectonic correlation, the structures, evolution history and dynamic background of the Qianyingzi Coal Mine are discussed. The Carboniferous-Permian coal measure strata in the mine are generally a gentle syncline with a NNE-trending axis, and cut by a series of faults. The faults developed in this mine are mainly medium- and small-sized with a throw of less than 20 m, and the number of reverse faults is significantly greater than that of normal faults. The strikes of reverse and normal faults are both mainly NE, followed by NNE and nearly N‒S. According to the characteristics of structural geometry, tectonic association, fault property and cross-cutting relation, the structural deformation of coal measure strata in the Qianyingzi Coal Mine can be divided into five stages, and the corresponding tectonic stress fields are NWW‒SEE compressive stress, nearly E‒W compressive stress, NW‒SE compressive stress, nearly E‒W and NW‒SE extensional stresses, respectively. It developed the Fengjia Syncline with a NNE-trending axis in the first stage and nearly N‒S-striking reverse faults in the second stage, which were the results of foreland deformation and subsequent continent-continent collision during the convergence of the North China Craton and South China Plate in the Indosinian period. The NNE-striking reverse sinistral faults and NE-striking reverse faults developed in the third stage is related to the rapid oblique subduction of the Izanagi Plate toward the East Asian continental margin at the beginning of the Early Cretaceous in the western Pacific region. Later, the fourth and fifth stages of the nearly N‒S- and NE-SW-striking normal faults were developed under the backarc extensional background in eastern China during the Early Cretaceous. These new results can be used to guide the rational arrangement for underground mining and also provide a new understanding for regional tectonic evolution of the Huaibei Coalfield.

A novel non-destructive workflow for examining germanium and co-substituents in ZnS

A suite of complementary techniques was used to examine germanium (Ge), a byproduct critical element, and co-substituent trace elements in ZnS and mine wastes from four mineral districts where germanium is, or has been, produced within the United States. This contribution establishes a comprehensive workflow for characterizing Ge and other trace elements, which captures the full heterogeneity of samples through extensive pre-characterization. This process proceeded from optical microscopy, to scanning electron microscopy and cathodoluminescence (CL) imaging, to electron microprobe analysis, prior to synchrotron-based investigations. Utilizing non-destructive techniques enabled reanalysis, which proved essential for verifying observations and validating unexpected results. In cases where the Fe content was <0.3 wt% in ZnS, cathodoluminescence imaging proved to be an efficient means to qualitatively identify trace element zonation that could then be further explored by other micro-focused techniques. Micro-focused X-ray diffraction was used to map the distribution of the non-cubic ZnS polymorph, whereas micro-focused X-ray fluorescence (μ-XRF) phase mapping distinguished between Ge4+ hosted in primary ZnS and a weathering product, hemimorphite [Zn4Si2O7(OH)2·H2O]. Microprobe data and μ-XRF maps identified spatial relationships among trace elements in ZnS and implied substitutional mechanisms, which were further explored using Ge and copper (Cu) X-ray absorption near-edge spectroscopy (XANES). Both oxidation states of Ge (4+ and 2+) were identified in ZnS along with, almost exclusively, monovalent Cu. However, the relative abundance of Ge oxidation states varied among mineral districts and, sometimes, within samples. Further, bulk XANES measurements typically agreed with micro-focused XANES (μ-XANES) spectra, but unique micro-environments were detected, highlighting the importance of complementary bulk and micro-focused measurements. Some Ge μ-XANES utilized a high energy resolution fluorescence detector, which improved spectral resolution and spectral signal-to-noise ratio. This detector opens new opportunities for exploring byproduct critical elements in complex matrices. Overall, the non-destructive workflow employed here can be extended to other byproduct critical elements to more fully understand fundamental ore enrichment processes, which have practical implications for critical element exploration, resource quantification, and extraction.

A Non-Invasive In Situ Spectroscopic Analysis of Cinnabar Minerals to Assist Provenance Studies of Archaeological Pigments

This study presents a non-invasive in situ methodology based on the use of portable elemental (energy dispersive X-ray fluorescence spectroscopy, EDXRF) and molecular (Raman spectroscopy) spectroscopic-based instrumentation as a tool to obtain preliminary information to assist subsequent provenance studies of archaeological cinnabar pigments in the laboratory. In this work, six cinnabar mineral ores, extracted from the Almadén mining district and an original raw pigment coming from the Archaeological Park of Pompeii have been analyzed. As the detection capacities and spectral resolution of the portable instruments are usually poorer than the equivalent benchtop equipment, a comparative study of the in-situ and laboratory results was conducted. Afterward, chemometric data treatment was performed considering both the molecular and elemental information. According to the elemental results, it was not possible to find a strong concordance between the cinnabar ores and the pigment from Pompeii, suggesting the need for additional methodologies in the laboratory (isotope ratio analysis) to complete a proper provenance study. However, this approach was useful to classify the ores according to their mineralogical differences. Therefore, this methodology could be proposed as a useful tool to conduct a representative sampling of the cinnabar mineral ores to be considered in a provenance study of archaeological cinnabar pigments.

Trace metal contamination status in soils of the abandoned gold mining district of Bindiba (East Cameroon): Pollution indices assessment, multivariate analysis and; geostatistical approach.

The online version contains supplementary material available at 10.1007/s40201-023-00849-y.

Retention potential of a drained wetland in the Lusatian lignite mining district, Briesener Niedermoor, Germany, Europe

Acid mine drainage (AMD) is one of the most important global causes for polluted water. It occurs in mining areas due to oxidation of sulfide minerals. Depending on hydrological conditions, wetlands are considered suitable for passive treatment of AMD. The aim of the study was to characterize the long-term retention performance of a drained wetland, Briesener Niedermoor, in an iron and sulfate contaminated catchment area. The site is located in the Lusatian lignite mining district, Germany. Hydrological and hydrochemical measurements as well as time series of groundwater and surface water were evaluated and saturation conditions of iron species were determined using Phreeqc Interactive and EH–pH diagrams for the Fe–S–K–O–H system. Progressing peat degradation due to drainage leads to a hydraulic behaviour of the wetland that is more comparable to a rain bog than a fen, and thus to more pronounced oxic conditions. Groundwater feeds the wetland with significant loads of iron and sulfate, which are temporally stored in the wetland. At low surface water discharge, iron is removed and weak acidic pH is buffered by the dominant phase of schwertmannite (Fe8O8(OH)6SO4), usually during summer months. In winter, greater water availability initializes a high source strength from the wetland, that cannot be retarded. Thus, only during summer, there is a retention potential; in winter, the retention potential is not strong enough to prevent an inflow of iron and sulfate. Only a significant rewetting of the wetland may result in a restoration of the retention potential of the wetland Briesener Niedermoor.

Metallogeny and exploration strategy for volcanic rocks hosting world class Be-U-F mineralization at Spor Mountain, Utah, U.S.A.

We report new geochemical data (major-elements, trace-elements, and Nd-Pb isotopes) for the Spor Mountain Formation (SMF), a volcanic sequence that hosts the largest deposit of beryllium in the world. Understanding the genesis of the deposit is critical for improved recognition of regional exploration targets containing additional volcanic-hosted beryllium resources. The deposit occurs in an area of extensive alkalic rhyolitic ash flow tuffs and calderas underlain by Paleozoic and older limestone, dolomite, shale, and quartzite. The lower fluorite and bertrandite-rich tuff and upper topaz-rich rhyolite of the SMF have overlapping zircon crystallization ages (25.59 + 0.29/−0.45 Ma). Enrichment of Be, U, and F is a key attribute of the SMF inherited from melting heterogeneous source materials and magma hybridization in the continental lithosphere. Two mineralization stages are implicated: magmatic, and hydrothermal/metasomatic. The magmatic stage occurred early, as indicated by the high beryllium content in early-crystallizing zircon. The post-magmatic/hydrothermal stage involved F-rich fluids that reacted with glass and carbonate nodules in the tuff to form bertrandite (and U-rich fluorite and opal) and high-grade mineralization. The rhyolite best displays the magmatic stage of enrichment. The SMF is alkaline. Chondrite-normalized REE patterns for tuff and rhyolite are regular, stacked subparallel, and imply a shared source derivation and evolution. The tuff and rhyolite plot along a sub-vertical array for Pb isotopes and suggest they are cogenetic; both have negative values of εNd. Pb isotopic ratios for SMF do not match the slopes, initial isotopic values, or estimated basement ages of precious and base metal mining districts in Utah; thus, they do not share a source region or evolution. Crustal ages from Nd isotopes (average TDM ~ 2.29 Ga) are older than basement ages obtained by Pb isotopes. The deposit occurs in a transitional area of thinned crust near the boundary between two basement domains, the eastern Great Basin and Colorado Plateau, which have contrasting ages. Many geochemical attributes are shared between SMF and the Ermakovka deposit in Russia: they represent the world's major commercial Be deposits. Rare-metal indices of granite-related mineralization show that SMF resembles other global beryllium-bearing granitic deposits. Despite this coincidence, none of these examples matches the mineralogy, geologic setting, or type of rare metal mineralization at Spor Mountain.

Revitalisering van het mijnverleden in Heerlen door hybride taalculturele praktijken

Revitalisation of Heerlen’s coal mining past through languagecultural practices
 This paper examines how inhabitants of Heerlen relate to the coal mining past of this city through a variety of languagecultural practices that cut across diverse media forms and genres, both textual (poems, rap songs), visual (portrait photography, material commodities), and digital (posts on Facebook, YouTube videos). Through these practices people in Heerlen express, repeat, and renew their individual and collective memories of Heerlen as the centre of the former Eastern Mining District in the twentieth century. We argue that Heerlen is undergoing a process of revitalisation that creates social personae, embedded locally, which are labelled tuupisch (typical). From a normative perspective, performances of identity and memory attributed and/or imagined as linked to this tuup (type) are often parodic and hybrid in character. Through an analysis of various examples, the paper demonstrates the critical potential of such hybrid languagecultural practices to contest dominant perspectives on the city’s mining heritage, to renegotiate place-based identities, and to establish new forms of cultural memory

Tailings Utilization and Zinc Extraction Based on Mechanochemical Activation.

The significant containment of the global mining industry is caused by the problem of the transition to sustainable metal extraction and the integrated use of technogenic raw materials from the tailings of ore processing. The modeling of metal leaching processes using mechanical activation of polymetallic raw material components is particularly important in expanding the application of mining tailings as inert fillers of filling mixtures. This study is aimed at detecting the rotor speed factor on the chemical and mechanochemical effect of zinc yield growth from polymetallic tailings of the mining industry. In this regard, the purpose of this study was to improve the modeling of metal leaching processes using mechanical activation by improving the compositions of the filling mixtures. The methodology of the work included several comprehensive studies: the mechanical activation of tailings during zinc leaching from pulp in the DESI-11 disintegrator; the activation of enrichment tailings and the formation of a filling mass with different parameters of the component composition; the curing of cubic samples and their testing on the IP-1250 press. The Vi Improved text editor was used to prepare the algorithms for deterministic methods of three-dimensional interpolation in the Python language. The experimental results were graphically displayed using Gnuplot. The study of the agitation leaching of the waste obtained from the Sadonskiy mining district results in the fact that the NaCl mass concentration decreased from 13 to 1% and the H2SO4 concentration stabilization within 0.5 to 0.6% led to a 3-time increase in the zinc yield from the pulp, according to the polynomial law (from 28 to 91%). The obtained results expand the idea of the mechanism of the strength gain by the filling mass under mechanical activation on the components of the filling mixture, as well as changes in the efficiency of zinc leaching at different ratios of two types of lixiviants (sulphuric acid and sodium chloride) in the leaching solution.

Assessment of the Condition of Soils before Planned Hard Coal Mining in Southern Poland: A Starting Point for Sustainable Management of Fossil Fuel Resources

In Poland’s largest mining district, the Upper Silesian Coal Basin, there is a growing interest in resource development by small operators. Some concession areas are not yet directly affected by the mining industry. The objects of this research are two such areas and the goal is to determine a load of heavy metals (HM) in soils prior to mining projects and to assess the extent of their contamination at this stage. The metals studied were Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, while HM contamination was assessed using the Contamination Factor (CF), Contamination Degree (CD), Pollution Load Index (PLI), and Geoaccumulation Index (Igeo). The Ecological Risk Potential Index (ER) and Comprehensive Potential Ecological Risk Index (PERI) were also employed. The pre-mining areas are close to an area where mining was terminated before 2000. For this area, we performed the same set of analyses as for the pre-mining areas studied. HM concentration levels and pollution indices in post-mining areas are significantly higher than in pre-mining areas. The results obtained in the post-mining area give an idea of the expected type and scale of potential threat to soils from mining and can form the basis for monitoring environmental contamination in subsequent investment and operation phases, as well as help develop and implement timely methods to prevent the increase in heavy metal immission to soils during mining activities. We believe that the presented approach of assessing the condition of soils starting at the pre-mining stage can support the sustainable management of energy resources in the cases studied and elsewhere.

Dependence of bioavailability of lead compounds in soils on the type and source of contamination (the example of Mexico City and mining area of Parral, Mexico)

Evaluation and monitoring of soil contamination with heavy metals relies in most cases on their bulk concentrations whereas the risks of negative effects on human health depend upon the content of their bioavailable forms. The paper presents the study of the dependence of lead bioavailability in the surface soil horizons upon the contamination type and source. Two territories in Mexico with sharp difference of the source of pollution: Mexico City megapolis where the lead in soils originates from the ethyl gasoline burning and mining district in the south of Chihuahua State where the mine tailings are the source of the toxic elements including lead. Bulk lead concentrations were measured by the X-ray fluorescence method, bioavailability was estimated by the method imitating the effect of the stomach and intestine solutions. The research has shown that both in Mexico City (especially in its central part) and in the mining district in the Chihuahua State bulk lead concentrations are several times higher than the background values. The soils of the mining district have average bulk lead concentrations 787,5 mg/kg and show the average bioavailability values 64% whereas in the Mexico City megapolis average bulk concentrations of lead are lower - 324,7 mg/kg but bioavailability reaches 83% and in some samples even 100%. These results support the conclusion that despite lower bulk lead concentrations in Mexico City the risk of its negative effect on humans is higher than in the mining district polluted with the wastes of mining industry. The explanation of the observed tendency is that the chemical form of lead has a major influence on its bioavailability. Dependence of bioavailability upon the bulk concentrations within each study territory has not been established.

Integrating Aster Images Processing and Fieldwork for Identification of Hydrothermal Alteration Zones at the Oumjrane-Boukerzia District, Moroccan Anti-Atlas

Mapping from remote sensing has become more effective in the field of geology, mainly in lithological discrimination and identification of hydrothermal alteration zones. The use of this technique consists in obtaining information about the rock mass and the main ones existing in the inaccessible areas. Satellite data from the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) sensor represent a favorable potential for detecting the spectral signatures of mineral zones and identifying their nature. These data are more reliable in places where the climate is arid with less abundant vegetation, as at the Oumjrane-Boukerzia mining district. This region which is part of the Eastern Anti-Atlas, is composed of several mineralized veins which still require detailed studies and exploration by the technique of remote sensing. In this work we applied several processing techniques on ASTER imagery such as Colored Composition, Principal Component Analysis and Ratio Bands. The use of the reports of the specialized Bands makes it possible to identify some hydrothermal alteration minerals within the mining district of Oumjrane Boukerzia. These minerals are represented mainly by iron oxides and hydroxides (Hematite, jarosite, limonite and goethite), carbonate minerals (dolomite, calcite), clay minerals (Illite, kaolinite and chlorite) and quartz minerals. This work allows us to produce a map of hydrothermal alteration zones which can be used as a valuable reference in the strategy of mining exploration for the base metals (Cu, Pb, Zn and Ba), in the mining district of Oumjrane-Boukerzia and in the entire Eastern Anti-Atlas.

Monitoring sedimentary areas from mine waste products with Sentinel‐2 satellite images: A case study in theSEof Spain

AbstractTorrential rainfall regimes, among others, are the origin of accelerated soil erosion. The Spanish southeastern Mediterranean region is characterised by an arid climate regime affected by extreme erosion episodes with an important loss of sediments. Soil erosion effects are even more noticeable in areas where soil has been anthropically degraded, as in the mining district ofSierra Minera de Cartagena. The present research focuses on monitoring and mapping the changes in the sediment distribution of iron oxides and hydroxyl (OH−) bearing minerals caused by a cold drop known in Spanish as 'DANA' in September 2019 on theRambla del Beal. This shortramblais fed by sediments from its drainage basin and by mining residues, irrigating a wide agricultural area. When discharges overflow theramblachannel, residues spread over its floodplain and reach the ecological protected coastal lagoonMar Menor. The objective of the study was mapping the mineral distribution of the mining materials eroded from the source areas and sedimented inRambla del Bealduring a DANA. The study was carried out using a pre‐ and a post‐DANA image from the Sentinel‐2 satellite. After masking vegetation, urban areas and water bodies, different band ratios (B4/B3, B11/B12, B8A/B6) and a Spectral Angle Mapper (SAM) classification were applied. Sediment deposits were identified in wider areas after the DANA. Iron oxides increased their extension by 11.08% in the central area (B3/B4 with R2of 0.84) and hydroxyl‐bearing minerals increased by 8.95% in theRambla del Beal's headwaters (B11/B12 withR2of 0.71). The SAM classification (with a 0.1 rad threshold and an overall accuracy of 87.33%) allowed the differentiation and classification of two ferric iron oxides (haematite and goethite) and one iron hydrous sulphate mineral (jarosite). Additionally, band ratio images were spatially overlaid with the soil land uses map layer of the cadastre in order to plot the land uses most affected by the transported sediments during the DANA. These results highlighted agricultural land as the areas (land uses) most affected by iron oxides deposition, as oxidation processes occur more rapidly in these areas. However, grassland and scrubland were the areas with the highest content of hydroxyl‐bearing minerals, as water is accumulated in these places, which favours hydrolysis reactions.HighlightsTorrential events can relocate large volumes of contaminated sediments from former mining areas.Sentinel‐2 allows monitoring mine waste iron‐sulphate changes caused by weathering alteration.Spatial mineralogical pattern in sediments is controlled by geomorphology and flood dynamics.The proposed digital image analysis allows mapping short‐term evolution of mine waste sediments.

THE RUSH STARTED HERE, PART III: ‘THE STREETS ARE PAVED WITH GOLD’—SPECULATION, GREED, AND DISAPPOINTMENT, 1849–2010

ABSTRACT Profitable gold mining began in the United States with the accidental discovery in 1799 of a seventeen-pound gold nugget in Cabarrus County, North Carolina. North Carolina’s gold production peaked between the 1830s and 1840s as hundreds of mines contributed hundreds of thousands of dollars a year to the national economy, necessitating the 1837 construction of a federal Branch Mint in Charlotte to process Piedmont gold. Gold mining suffered a major decline in North Carolina after the discovery of the richer and more extensive gold deposits in California in 1848. However, the North Carolina gold miners who did not join the western rush continued to work the shafts of the Piedmont using increasingly sophisticated European and South American technology, as well as new innovations such as hydraulic mining techniques from California, until the advent of the Civil War. From the end of Reconstruction (1877) to 1920, gold mining in North Carolina was sporadic and often funded by outside investors or used as a ruse in gold and stock scams. Copper mining, with gold and silver as secondary products, using increasingly complex technology and associated environmental issues, drove most of the mining fervor during this period. Following the Great Depression of the 1930s, gold production slowly increased until the Second World War, but never became a major industry as they were out-competed by the more profitable gold fields in the western United States, Alaska, Canada, Australia, and South Africa. From the 1970s to today, dependent upon the price of gold in the market and the requirements of environmental regulation, prior mining districts in North (and South) Carolina have continued to be examined, explored and cautiously mined using cyanide heap leach techniques. Although few in number, these limited lease mining projects have extracted over two million troy ounces of gold and nearly a million troy ounces of silver by 2010. Future extraction by the ongoing Haile Mine (South Carolina) project will increase this amount substantially in the next decade. Nevertheless, Cabarrus County continues to hold the world’s record for producing the greatest number of large (a pound or more) gold nuggets and was the epicenter of North America’s first gold rush.

Nature inspired synthesis of magnetite nanoparticle aggregates from natural berthierine.

We investigate the origin of the magnetite nanoparticle aggregates (MNAs) from the Peña Colorada iron-ore mining district (Mexico) to devise a nature inspired synthesis process. Three types of samples were used: natural MNAs recovered from the mine, concentrated magnetite microparticles as reference material, and thin berthierine films used to synthesize MNAs. The chemical, mineralogical, crystallographic and rock magnetic properties were determined by polarized microscopy, high-resolution transmission electron microscopy, electron microprobe, X-ray diffraction, Mössbauer spectroscopy, and thermomagnetic and hysteresis measurements. MNAs were synthesized in the lab with the following steps. We start with berthierine thin films, which are heated to temperatures between 495 and 510 °C leading to formation of numerous stable magnetite nanocrystals. They grow at a temperature above 650 °C. Space restrictions lead to the formation of dense MNAs. Smaller MNAs, <200 nm, with a Curie temperature of 650 °C, shows superparamagnetic behavior. While larger MNAs, >7 μm, show Curie temperature of 578 °C and ferromagnetic behavior. Based on present observations, we suggest that MNAs in the Peña Colorada iron-ore formed in a marine environment, where berthierine formation was accelerated by Fe-rich hydrothermal springs that supplied iron and increased the temperature. Most notably, our laboratory experiments mimicked natural conditions and were able to successfully nucleate and grow magnetite nanoparticles which developed into MNAs. These MNAs were similar to those recovered from the Peña Colorada iron-ore deposit. This study, thus, provides a nature inspired method for synthesis of magnetite nanoparticles and its aggregates.

Chemical pollution peculiarities of the Nadiya mine rock dumps in the Chervonohrad Mining District, Ukraine

Purpose. The research purpose is to study the peculiarities of chemical pollution of the Nadiya mine rock dumps in the Chervonohrad Mining District, depending on the relief conditions and slope exposure, as well as to analyze the general trends in the distribution of chemical elements compared to the natural background. Methods. The chemical pollution differentiation of the Nadiya mine rock dumps at the level of ecotopes is studied on the basis of dispersion analysis; multidimensional ordination of ecotopes in the space of geochemical indicators – based on the Principle Component Analysis; a typological scheme of mine rock dump ecotopes is constructed based on discriminant analysis; statistical processing of chemical pollution parameters. Findings. It has been determined that the level of chemical pollution of the Nadiya mine rock dumps is characterized by significant heterogeneity even within the same slope exposure. Similarity in the distribution of chemical elements makes it possible to distinguish 6 of their associations, the main of which are I (Mg, Ca, S) and II (Al, Fe, K, Si). An analysis of the dependence between the chemical element concentrations indicates a close link between many parameters. It has been revealed that the closest dependence on the anthropogenic load intensity is demonstrated by such elements as Mg, Pb, Sn, Fe, Al, Cu, P, Ni, Zn. It has been determined that the difference between the ecotopes of different dump exposures is explained mainly by the level of Ca and Al concentration. Originality. It has been revealed for the first time that the Nadiya mine rock dumps of the Chervonohrad Mining District are characterized by an ecological space, which is assessed on the basis of the ordination of ecotopes on the axes of complex geochemical gradients of the environment. The typological scheme of mine rock dumps reflects the gradient of soil cover chemical pollution compared to the natural background. Practical implications. By determining the geochemical conditions of ecotopes in a certain period of time, it is possible to identify their position in the ecological-cenotic space of dump vegetation, as well as to predict the stability and possible changes in the vegetation cover as a result of various forms of anthropogenic impact.

Plant diversity and species composition of the abandoned mines of the Iglesiente mining district (Sardinia, Italy): A restoration perspective

The ‘metalliferous ring’ of Iglesiente was for centuries the most important mining district of Italy. After a marked decline in mining activities, alternative management strategies were proposed to face issues mainly related to unemployment and environmental pollution. We focused on the coastal section of the mining district, in order to evaluate the development of vegetation after disturbance and assess the conservation value of the study area. The floristic composition in terms of species richness, number of endemics, evenness, life form diversity, vegetation and cryptogamic covers were analysed for 96 vegetation samples. Three main plant assemblages with 227 vascular plant species and 18 endemics were described. The most influential variable in determining species composition was the herbivory, which negatively affects species richness, endemic species richness and life form diversity and, positively, the evenness. Other influential variables were elevation, positively associated with species and endemic species richness, and the degree of debris/rock flow, which negatively influences species richness and life form diversity. Soil grain size positively influences evenness and negatively life form diversity and vegetation cover. The number of years of mining inactivity was only positively influencing life form diversity. Each identified community, especially those characterised by perennial herbs and small shrubs, can provide surrogate habitats for many endemic plants, which can be in turn used for phytostabilization and remediation. Further indications for strategic management of these mining environments, where policy and long-term monitoring are necessary interrelated strategies, were provided.

Evaluating determinants of treatment outcomes among tuberculosis patients in the mining district of Butha Buthe, Lesotho

Before the COVID-19 pandemic, tuberculosis (TB) was the leading infectious cause of death globally. In low- and middle-income countries (LMIC) including Lesotho, treatment outcome is lower than the recommended rate and poor TB treatment outcomes remain a programmatic challenge. The aim of this study was to determine unfavourable treatment outcomes and associated risk factors among TB patients in Butha Buthe district. This was a retrospective record review of TB patients registered between January 2015 and December 2020. Data were collected from TB registers and patients' files and entered Microsoft Excel 2012. Analysis was conducted using R and INLA statistical software. Descriptive statistics were presented as frequencies and percentages. The differences between groups were compared using Pearson's X 2 test in bivariate analysis. Frailty Cox proportional hazards model was used to determine the risk of unfavourable outcomes among the variables. A total of 1792 TB patients were enrolled in the study with about 70% males (1,257). Majority (71.7%) of the patients were between 20 and 59 years old, with 48% of the patients being unemployed. Almost a quarter of the patients (23.1%) had unfavourable outcomes with death (342 patients) being the most common unfavourable outcome. Our study has shown that patients older than 59 years, and unemployment increased the risk of having unfavourable treatment outcomes. Death was the most common unfavourable outcome followed by lost-to-follow up. We also observed that the patients in the initiation phase of treatment died at a faster rate compared to those in the continuation phase (p=0.02). TB treatment programs should have efficient follow-up methods geared more toward elderly patients. Active case finding to identify population at risk should be part of a TB program which would improve early diagnosis and treatment initiation. Patients in the intensive phase of the treatment program should be monitored more closely to determine adverse drug effects and nutritional requirement to prevent death during this phase of treatment.