Metal Sulfide Ores Research Articles

Unveiling different pyrrhotite superstructures in copper-gold ore samples: Insights from advanced spectroscopic and microscopic characterization

Pyrrhotite exhibits diverse non-stoichiometric superstructures with varied surface reactivities, causing contradictory flotation behaviors in industrial processes. The challenges in managing pyrrhotite in processing plants stem from the lack of systematic mineralogical techniques to distinguish its superstructures in low-grade ore samples without any preprocessing, such as purification or manual sample picking. This study established a comprehensive technique to differentiate between pyrrhotite superstructures in low-grade metal sulfide ores using spectroscopic and microscopic methods. The examined samples came from a natural copper–gold orebody from Western Australia and the flotation concentrate of the ore. Initial identification of pyrrhotite through XRD confirmed the presence of pyrrhotite in the samples but failed to discern magnetic and nonmagnetic pyrrhotite superstructures due to the samples' low pyrrhotite content and XRD peak overlaps. In this regard, magnetic colloid technique (MCT) was utilized to effectively identify the presence of both magnetic and nonmagnetic pyrrhotite superstructures in the samples. Energy-dispersive X-ray spectroscopy (EDS) analysis revealed the Fe:S (at.%) ratio ranging from 0.840 to 0.930 for both the ore and the flotation concentrate, affirming the presence of both magnetic and nonmagnetic pyrrhotite with possible 4C, 5C and 6C superstructures. Based on the information obtained from XRD, MCT and EDS, Electron Backscatter Diffraction (EBSD) analysis successfully solved the challenge of identifying pyrrhotite superstructures. By comparing Kikuchi patterns from various zones with different Fe:S ratios to reference patterns, the EBSD confirmed the presence of 4C, 5C and 6C pyrrhotite superstructures in the examined samples. This methodology establishes a comprehensive framework for identifying pyrrhotite superstructures in complex ore samples, offering insights for industrial applications.

Depression mechanism of Na2CS3 on pyrite in lime- CuSO4 system

The unavoidable presence of ionic substances in the ore pulp can adversely effects on the separation of pyrite from other valuable metal sulfide ores. Developing new reagents to eliminate this effect is of great significance. In this study, a novel approach was proposed to depress pyrite by utilizing sodium trithiocarbonate (Na2CS3) as a depressant in the lime-CuSO4 system. The results of the micro-flotation experiments showed that a low dosage of Na2CS3 in the lime-CuSO4 system could effectively depress pyrite. The presence of CuSO4 in the solution which improves the ability of BX to adsorb on the surface of the pyrite was also revealed by the analysis of LEIS, UV–Vis, and contact angle, while the addition of Na2CS3 effectively hindered the adsorption of BX. XPS and SEM-EDS analysis results showed that Na2CS3 forms a complex with Cu2+ and adsorbs onto the pyrite surface, thereby impeding the adsorption of the collector and effectively depressing pyrite.

Biofilm formation and development during the pyrite bioleaching of moderately thermophilic microorganisms

Bioleaching is a process that uses microorganisms to recover metals from intractable metal sulfide ores. Metal sulfide bioleaching is an interfacial process, and biofilm growth is crucial during the early phases. To study the interactions between microbes and minerals during the bioleaching of moderately thermophilic microorganisms, the formation and development of biofilms on pyrite coupons incubated in shake flasks for 40 days were evaluated. The biofilm biomass progressively increased as bioleaching proceeded. The most extensive biofilm was formed on day 30, when bacteria were attached to the mineral surface or submerged in extracellular polymeric substances. Confocal laser scanning microscopy indicated that the biofilm biomass of pyrite on day 40 was 6.55, 5.28, 3.17, and 1.70 times higher than that on days 5, 10, 20, and 30, respectively. Extracellular protein content exhibited an increasing trend throughout the process, whereas extracellular polysaccharides played a significant role during the early stages. Live/dead staining showed the highest mortality rate of 94% when cells were in contact with pyrite in the early stage, and the percentage of live bacteria increased in the later period. In the bioleaching environment, mature biofilms appeared to form relatively quickly after day 20. Real-time quantitative fluorescent quantitative analysis indicated that biofilm formation played an important role in defense against hostile external environments. In this study, biofilm formation and the associated RNA transcript numbers of moderately thermophilic microorganisms during pyrite bioleaching were investigated, contributing to the understanding of cell-mineral interactions.

Sulphate-reducing bacteria-mediated pyrite formation in the Dachang Tongkeng tin polymetallic deposit, Guangxi, China

Mediation by sulphate-reducing bacteria (SRB) is responsible for pyrite (FeS2) formation. The origin of the Dachang tin polymetallic ore field is related to the mineralisation of submarine hydrothermal vent sediments. Here, we investigated SRB in these ores via morphological, chemical, and isotopic analyses. Polarised and scanning electron microscopy indicated that trace SRB fossils in the metal sulphide ore were present in the form of tubular, beaded, and coccoidal bodies comprising FeS2 and were enclosed within a pyrrhotite (FeS) matrix in the vicinity of micro-hydrothermal vents. The carbon (C), nitrogen (N), and oxygen (O) contents in the FeS2 synthesised by SRB were high, and a clear biological Raman signal was detected. No such signals were discerned in the peripheral FeS. This co-occurrence of FeS, FeS2, and the remains of bacteria (probably chemoautotrophic bacteria) was interpreted as the coprecipitation process of SRB-mediated FeS2 formation, which has, to the best of our knowledge, not been reported before. Our study also illustrates that combined energy-dispersive X-ray spectroscopy, Raman spectroscopy, and isotopic analysis can be used as a novel methodology to document microbial-mediated processes of mineral deposition in submarine hydrothermal vent ecology on geological time scales.

An appraisal of the principal concerns and controlling factors for Arsenic contamination in Chile

Although geogenic Arsenic (As) contamination is well-recognized in northern Chile, it is not restricted to this part of the country, as the geological conditions favoring As release to the human environment exist across the country as well, although not at the same level, based on comparatively fewer studies in central and southern Chile. The present work provides a critical evaluation of As sources, pathways, and controls with reports and case studies from across the country based on an exhaustive bibliographic review of its reported geogenic sources and processes that affect its occurrence, systematization, and critical revision of this information. Arc magmatism and associated geothermal activities, identified as the primary As sources, are present across the Chilean Andes, except for the Pampean Flat Slab and Patagonian Volcanic Gap. Metal sulfide ore zones, extending from the country’s far north to the south-central part, are the second most important geogenic As source. While natural leaching of As-rich mineral deposits contaminates the water in contact, associated mining, and metallurgical activities result in additional As release into the human environment through mining waste and tailings. Moreover, crustal thickness has been suggested as a principal controlling factor for As release, whose southward decrease has been correlated with lower As values.

A new organosilane passivation agent prepared at ambient temperatures to inhibit pyrite oxidation for acid mine drainage control

Acid mine drainage (AMD) is a significant environmental problem caused by the oxidation of pyrite and other metal sulfide ores. Organosilane passivation is an effective strategy to inhibit pyrite oxidation. However, synthetic organic silane passivation agents generally require temperatures of 50–80 °C, resulting in high energy consumption and high synthesis cost. In this study, a 3-aminopropyltrimethoxysilane -methyltrimethoxysilane (APS-MTMS) coatings was successfully prepared at ambient temperatures of 15–40 °C as a passivation agent to inhibit pyrite oxidation. Chemical leaching tests were used to study the inhibition performance of APS-MTMS for pyrite oxidation. The experimental results showed that the release of the total Fe from APS-MTMS-coated pyrite was 11.31 mg/L after chemical oxidation for 7 hours, and the passivation rate can reach 77.78%. The contact angle of the APS-MTMS-coated pyrite was significantly larger (140.4°) than that of the bare pyrite (58.8°), indicating that APS-MTMS prompted the formation of a superhydrophobic surface of pyrite, improving the oxidation resistance. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied to probe the interaction mechanism of APS-MTMS with pyrite. The results indicated that APS accelerated the Si–O–Si formation by amino protonation and enriched a crosslinked network of Si–O–Si and Fe–O–Si on the pyrite surface to prevent pyrite oxidation. This study provides a novel method for preparing organosilane passivation materials at ambient temperatures for AMD control.

Characterization and simulation of graphite edge surfaces for the analysis of carbonaceous material separation from sulfide ores by flotation

The efficient processing of base metal sulfide ores and sulfidic gold ores is sometimes compromised by the presence of carbonaceous material (CM). One common way of dealing with the CM problem is to pre-float the CM before the flotation of the sulfide minerals. Most CM exhibits some crypto crystalline graphitic structure. Although the graphite face surface has been studied extensively and is well described, the structural and surface properties of the graphite edge surface are more complex. In this study, the surface topography, graphitic structure, and functional features of the highly ordered pyrolytic graphite (HOPG) edge surface are reported to help provide a fundamental understanding of the behavior of CM in sulfide flotation separations. Surface structural defects, disordered atomic structure, and polar groups (C-O and C=O) were found from Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Raman, and X-ray Photoelectron Spectroscopy (XPS) analyses. The armchair and zigzag edge surfaces of graphite have been examined by ab-initio and Molecular Dynamics (MD) simulation to describe the experimental results, including wetting characteristics based on contact angle measurements. Polar oxygen species, such as C-O-C and C=O bonds, were identified during oxidation of the graphite edge surfaces by ab-initio simulation of the surface reaction with oxygen molecules. MD simulations indicated complete wetting of the simulated oxidized graphite edge surfaces by water, whereas previous experimental contact angle measurements at the HOPG edge surface (40°) revealed some hydrophobic character, which indicate the complex heterogenous nature of the edge surfaces.

Effect of diurnal temperature range on bioleaching of sulfide ore by an artificial microbial consortium

Temperature is considered to be one of the main factors affecting bioleaching, but few studies have assessed the effects of diurnal temperature range (DTR) on the bioleaching process. This study investigates the effects of different bioleaching temperatures (30 and 40 °C) and DTR on the bioleaching of metal sulfide ores by microbial communities. The results showed that DTR had an obvious inhibitory effect on the bioleaching efficiency of the artificial microbial community, although this effect was mainly concentrated in the early and middle stages (0–18 days) of exposure, gradually decreasing until almost disappearing in the late stage (18–24 days). Extracellular polymeric substance (EPS) analysis showed that DTR did not change the composition of the EPS matrix (humic acid-like substances, polysaccharides and protein-like substances), but had a significant effect on the generative behavior of EPS, inhibiting the secretion of EPS during the early and middle stages of the bioleaching process. However, the continual increase in EPS secretion in the bioleaching system gradually reduced the adverse effects of DTR on mineral dissolution. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy- energy dispersive spectrometry (SEM-EDS) analysis of the bioleached residue showed that DTR had no obvious effect on the mineralogical characteristics of sulfide ore. Therefore, in industrial sulfide ore bioleaching applications, in order to accelerate the artificial microbial community start-up process, temperature control measures should be increased in the bioleaching process to reduce the adverse effects of DTR on mineral dissolution.

Diffusible signal factor signaling controls bioleaching activity and niche protection in the acidophilic, mineral-oxidizing leptospirilli

Bioleaching of metal sulfide ores involves acidophilic microbes that catalyze the chemical dissolution of the metal sulfide bond that is enhanced by attached and planktonic cell mediated oxidation of iron(II)-ions and inorganic sulfur compounds. Leptospirillum spp. often predominate in sulfide mineral-containing environments, including bioheaps for copper recovery from chalcopyrite, as they are effective primary mineral colonizers and oxidize iron(II)-ions efficiently. In this study, we demonstrated a functional diffusible signal factor interspecies quorum sensing signaling mechanism in Leptospirillum ferriphilum and Leptospirillum ferrooxidans that produces (Z)-11-methyl-2-dodecenoic acid when grown with pyrite as energy source. In addition, pure diffusible signal factor and extracts from supernatants of pyrite grown Leptospirillum spp. inhibited biological iron oxidation in various species, and that pyrite grown Leptospirillum cells were less affected than iron grown cells to self inhibition. Finally, transcriptional analyses for the inhibition of iron-grown L. ferriphilum cells due to diffusible signal factor was compared with the response to exposure of cells to N- acyl-homoserine-lactone type quorum sensing signal compounds. The data suggested that Leptospirillum spp. diffusible signal factor production is a strategy for niche protection and defense against other microbes and it is proposed that this may be exploited to inhibit unwanted acidophile species.

A novel approach for metal extraction from metal sulfide ores with NH4Cl: A combined DFT and experimental studies

Chalcocite (Cu2S) is the main source for metallurgical production of copper worldwide but it usually co-exist with nickel sulfide in nature. To develop an efficient and green process for the separation and extraction of valuable metals from high-grade matte, we performed density functional theory (DFT) calculations and experimental studies to elucidate chlorination mechanism of Cu2S with ammonium chloride (NH4Cl). First, NH4Cl can react with Cu2S directly in the absence of O2, leading to the formation of H2S and NH3 with negative adsorption energies. Second, O2 can promote the chlorination process by providing adsorbed O and promoting the dissociation of HCl decomposed from NH4Cl, leading to the formation of H2O and CuCl species eventually. Besides, SO2 generated at the Cu2S surface after O2 dissociative adsorption, may leading to the generation of Cl2. Finally, the chlorination can also be achieved by the interaction between Cu2S and Cl2, which is favored thermodynamically and kinetically. Based on the computational results, low-temperature roasting experiments were performed. Cu2S was successfully converted into the corresponding metal chloride (CuCl) by NH4Cl in the absence of O2, but the chlorination process is incomplete with unreacted Cu2S. However, the conversion from Cu2S to CuCl is complete under air atmosphere, consistent with our computational results. Furthermore, metallic copper was successfully obtained at the cathode through electrodeposition with CuCl. The present study reveals detailed reaction mechanism between Cu2S and NH4Cl, and shows the chlorination of Cu2S by NH4Cl followed by electrodeposition of the resulting CuCl as a highly efficient and green process.

Degradation of various thiol collectors in simulated and real mineral processing wastewater of sulfide ore in heterogeneous modified manganese slag/PMS system

Residual flotation reagents (FRs) in mineral processing wastewater (MPW) cause serious organic pollution and difficult to discharge or recycle of MPW. In this study, the degradation of 100 mg/L of FRs (butyl xanthate (BX), diethyl dithiocarbamate (DDTC), ester-200 (Z-200) and butyl amine (BA)) commonly used for metal sulfide ore flotation were investigated by heterogeneous advanced oxidation process (AOPs) adopting peroxymonosulfate (PMS) as oxidants and modified manganese slag as metal-base catalyst (MS-N3H). The results showed MS-N3H/PMS system had higher degradation capacity than other reports, by which 100% of DDTC and 97.3% of BX could be degraded in 10 min, also 93.2% of Z-200 and 85.6% of BA were degraded in 30 min, respectively. The differential behaviours in degradation of thiol collectors (TCs) were correlated to their molecule structures and affected by their HMO index. However, the good water solubility of BX made it as the most degradable reagents in competitive system. The catalytic reactions of Z-200 and BA were pH-dependent processes which were dominated by the PMS ionization and base activation. Inorganic ions had little effects on reactions except for SiO32−, but the negative effect could be alleviated by the integrated process. Higher mineralization degrees of C, S and N elements indicated that TCs and their by-products were removed by the MS-N3H/PMS with higher degradation rates. Further, the catalyst showed superior regeneration ability and the system could be effectively used in real MPW treatment with relatively high removal efficiency of total organic carbon (TOC).

Arsenic: its chemistry, its occurrence in the earth and its release into industry and the environment

Arsenic is widespread in the environment where it occurs combined with metals and sulfur and as secondary minerals in combination with oxygen. Its atomic structure allows it to be trivalent or pentavalent, and its properties lead to its classification as a metalloid in the periodic classification of the elements. Arsenic trioxide is a by-product of the smelting of metal sulfide ores and can contaminate other industrial products such as sulfuric acid. Arsenic from mineral deposits can also be solubilized and be present in groundwater, where it presents a health and environmental hazard, and in the sea, where it can be taken up by marine animals in the form of arseno-betaines. Although arsenates resemble phosphates in their chemistry, and can be transported with them in living systems, arsenate cannot replace phosphate in plant and animal metabolism as has sometimes been postulated.

Enhanced microbial corrosion of stainless steel by Acidithiobacillus ferrooxidans through the manipulation of substrate oxidation and overexpression of rus.

Acidithiobacillus ferrooxidans cells can oxidize iron and sulfur and are key members of the microbial biomining communities that are exploited in the large-scale bioleaching of metal sulfide ores. Some minerals are recalcitrant to bioleaching due to the presence of other inhibitory materials in the ore bodies. Additives are intentionally included in processed metals to reduce environmental impacts and microbially influenced corrosion. We have previously reported a new aerobic corrosion mechanism where A. ferrooxidans cells combined with pyrite and chloride can oxidize low-grade stainless steel (SS304) with a thiosulfate-mediated mechanism. Here we explore process conditions and genetic engineering of the cells that enable corrosion of a higher grade steel (SS316). The addition of elemental sulfur and an increase in the cell loading resulted in a 74% increase in the corrosion of SS316 as compared to the initial sulfur- and cell-free control experiments containing only pyrite. The overexpression of the endogenous rus gene, which is involved in the cellular iron oxidation pathway, led to a further 85% increase in the corrosion of the steel in addition to the improvements made by changes to the process conditions. Thus, the modification of the culturing conditions and the use of rus-overexpressing cells led to a more than threefold increase in the corrosion of SS316 stainless steel, such that 15% of the metal coupons was dissolved in just 2 weeks. This study demonstrates how the engineering of cells and the optimization of their cultivation conditions can be used to discover conditions that lead to the corrosion of a complex metal target.

Integrating Geophysical Attributes with New Cuckoo Search Machine-Learning Algorithm to Estimate Silver Grade Values–Case Study: Zarshouran Gold Mine

The exploration methods are divided into the direct and indirect categories. Among these, the indirect geophysical methods are more time- and cost-effective compared with the direct methods. The target of the geophysical investigations is to obtain an accurate image from the underground features. The Induced polarization (IP) is one of the common methods used for metal sulfide ore detection. Since metal ores are scattered in the host rock in the Zarshouran mine area, IP is considered as a major exploration method. Parallel to IP, the resistivity data gathering and processing are done to get a more accurate interpretation. In this work, we try to integrate the IP/RS geophysical attributes with borehole grade analyses and geological information using the cuckoo search machine-learning algorithm in order to estimate the silver grade values. The results obtained show that it is possible to estimate the grade values from the geophysical data accurately, especially in the areas without drilling data. This reduces the costs and time of the exploration and ore reserves estimation. Comparing the results of the intelligent inversion with the numerical methods, as the major tools to invert the geophysical data to the ore model, demonstrate a superior correlation between the results.

The importance of edaphic niches functionality for the sustainability of phytomanagement in semiarid mining impacted ecosystems

Mining activities on metal sulphide ores are considered one of the most environmentally damaging anthropogenic activities worldwide, mainly due to the production of metal(loid)- enriched tailings. The objective of the work was to elucidate which factors, including edaphic, vegetation and microbiological aspects, determine soil functionality in the phytomagement of mine tailings piles in semiarid areas. For this purpose, a field study was conducted using a transect experimental design in a former mining area located in southern Spain. Soil characteristics, including edaphic parameters, bacterial and fungal compositions, were determined. The variation in edaphic parameters (pH, electrical conductivity, organic carbon, particle size distribution, etc) through the deterioration transect caused a decrease in plant and microbial diversities, as well as in microbial productivity measured by enzymatic activities. Variation in bacterial relative abundances through the transect was better explained by soil fertility related factors, such as organic matter, pH, salinity, enzymatic activities or microbial biomass (which in turn were related to the presence of plants), than by metals concentrations. The presence of vegetation at the tailings allowed the transition from lithotrophic bacterial orders which dominated in bare tailings areas (e.g. Acidimicrobiales, Chromatiales) to organotrophic oriented orders (e.g. Cytophagales, Actinomycetales). Vegetated patches at the tailings pile and its borders shared some organotrophic bacteria with control forest samples (e.g. Rhizobiales), indicating that natural plant mediated successional processes might stimulate biogeochemical cycles similar to those occurring at non-polluted systems. This functionality of the impacted sites, which include unfavourable edaphic conditions, should be taken into account in the phytomanagement of mine tailings, since it may support its long-term sustainability. Unlike bacteria, variations in fungal relative abundances through the transect were not clearly explained by soil parameters or the presence of plants. Other factors related to spatial distribution or the type of organic substrates may be more determinant in the case of fungi.

Explosion Pressure and Minimum Explosible Concentration Properties of Metal Sulfide Ore Dust Clouds

The explosion pressure and minimum explosible concentration (MEC) properties of metal sulfide ore dust clouds are valuable for the prevention and control of metal sulfide ore dust explosions. In this study, a 20 L explosion sphere vessel was used to investigate the effect of sulfur content, particle size, and concentration on the explosion pressure and minimum explosible concentration of metal sulfide ore dust clouds. Four samples with different sulfur contents were selected (30%–40%, 20%–30%, 10%–20%, and 0%–10%). Before and after the explosion, samples were tested by X-ray diffraction. The results indicate that the metal sulfide ore dust is explosive dust with St1 grade explosion pressure. With an increase in concentration, the maximum explosion pressure increased at first and then decreased. With an increase in sulfide content, the explosion pressure of metal sulfide ore dust increased, while the minimum explosible concentration decreased. As particle size decreased, the MEC also decreased. The sulfur content, particle size, and concentration of metal sulfide ore dust were the main factors affecting the explosion hazard.

Effect of Desliming of Tailings on the Fresh and Hardened Properties of Paste Backfill Made from Alkali‐Activated Slag

Cemented paste backfill (CPB) allows environmental friendly management of potentially hazardous tailings generated from milling of nonferrous metal sulphide ores by placing such tailings into the underground mined‐out openings. The components of CPB are tailings, water, and binders. These components significantly affect the physicomechanical, workability, and geotechnical properties of CPB. Ordinary Portland cement (OPC) is the commonly used binder for CPB operations. The effects of the tailings characteristics and OPC are extensively studied in the study area. The beneficial effect of the use of alkali‐activated slags (AASs) on the mechanical and durability properties of CPB of sulphide‐rich tailings has been recently reported. Therefore, this study especially focused on the effect of desliming of the tailings on the workability properties of sulphide‐rich tailings CPB containing AAS besides hardened properties. In this scope, the water‐retention capacities of full (FT) and deslimed tailings (DT) and the workability characteristics of CPB mixtures were studied. DT was found to decrease the water‐retention capacity, leading to denser CPB mixtures. In addition, DT‐AASs usage produced no adverse effect on the workability of fresh CPB materials. LSS‐S (slag activated with liquid sodium silicate) improved the flowability of CPB mixtures owing to its dispersant effect. Desliming also modified the tailing properties by removing fine particles and improved the main geotechnical parameters of CPB.

Depression of pyrite in a low-alkaline medium with added calcium hypochlorite: Experiment, visual MINTEQ models, XPS, and ToF–SIMS studies

Ca(ClO)2 is a promising depressant for differential flotation of base metal sulfide ores. However, limited studies have been conducted on the depression mechanism of Ca(ClO)2 for pyrite. This study investigates the effect of Ca(ClO)2 on pyrite flotation with butyl xanthate (KBX) in a low-alkaline medium. The addition of Ca(ClO)2 at pH 8.7 enhances pyrite hydrophilicity and decreases flotation recovery by ∼60%. Solubility tests and Visual MINTEQ model analysis indicate that Ca(ClO)2 promotes the dissolution of pyrite and produces more hydrophilic species on the pyrite surface. Contact angle measurement results confirm that adding Ca(ClO)2 increases the number of hydrophilic species. XPS study indicates that the depressing effect of Ca(ClO)2 on pyrite is due to the formation of CaSO4 and Fe(OH)3 and the adsorption of Ca(OH)+ on the surface. ToF–SIMS results provide strong evidence that adding Ca(ClO)2 increases the amount of hydrophilic species and decreases dixanthogen adsorption onto the pyrite surface. The thickness of the whole formed hydrophilic species is approximately 41.7 nm, and the thickness of the formed dixanthogen is few nanometers. Based on semiquantitative determination, the number of hydrophilic species follows the order of hydroxy calcium > iron carbonyl > hematite > calcium sulfate > calcium carbonate. Overall, hydrophilic species reduce adsorption of dixanthogen and significantly reduce the flotation performance of pyrite.

Sulfide ore prospecting in carbon-containing stratum using comprehensive time-domain induced polarization and controlled-source audio-frequency magnetotellurics

Carbon-bearing stratum normally features low resistance and high polarization. If the lithostratigraphy of the exploration area contains large amounts of carbon, the induced polarization anomaly caused by metal sulfide ore bodies will be inundated by the high polarization of carbon-containing wall rock. In this work, we adopted time-domain induced polarization (TDIP) and controlled-source audio-frequency magnetotellurics (CSAMT) on deep prospecting of the carbon-bearing stratum of the Ar Horqin Banner, Inner Mongolia. The underground medium is divided into target geologic bodies according to the geological information within the known exploration line borehole, and the physical properties of various target geologic bodies are calculated using weighted averages to build a geologic-geophysical model that can fit the observation data. Consequently, we can determine the range and morphological characteristics of the electrical properties of the ore-bearing geologic bodies in the inversion results in the study area. Then we can use the characteristics summarized from the known exploration line to interpret unknown exploration line. Results indicated that, when the difference in physical properties between the ore body and interference wall rock is not clear, the geologic body can be classifi ed via the paragenetic (associated) assemblage relations of the underground medium. Geological interpretation is guided by the comprehensive physical properties of ore-bearing geologic bodies to avoid interferences.

Marine Mineral Exploration With Controlled Source Electromagnetics at the TAG Hydrothermal Field, 26°N Mid‐Atlantic Ridge

AbstractSeafloor massive sulfide (SMS) deposits are of increasing economic interest in order to satisfy the relentless growth in worldwide metal demand. The Trans‐Atlantic Geotraverse (TAG) hydrothermal field at 26°N on the Mid‐Atlantic Ridge hosts several such deposits. This study presents new controlled source electromagnetic, bathymetric, and magnetic results from the TAG field. Potential SMS targets were selected based on their surface expressions in high‐resolution bathymetric data. High‐resolution reduced‐to‐the‐pole magnetic data show negative anomalies beneath and surrounding the SMS deposits, revealing large areas of hydrothermal alteration. Controlled source electromagnetic data, sensitive to the electrical conductivity of SMS mineralization, further reveal a maximum thickness of up to 80 m and conductivities of up to 5 S/m. SMS samples have conductivities of up to a few thousand Siemens per meter, suggesting that remotely inferred conductivities represent an average of metal sulfide ores combined with silicified and altered host basalt that likely dominates at greater depths.