Massive Sulfide Research Articles

Seismic Imaging of Mineral Exploration Targets: Evaluation of Ray- vs. Wave-Equation-Based Pre-Stack Depth Migrations for Crooked 2D Profiles

Seismic imaging is now a well-established method in mineral exploration with many successful case studies. Seismic data are usually imaged in the time domain (post-stack or pre-stack time migration), but recently pre-stack depth imaging has shown clear advantages for irregular/sparse acquisitions and very complex targets. Here, we evaluate the effectiveness of both ray-based and wave-equation-based pre-stack depth imaging methodologies applied to crooked-line 2D seismic reflection profiles. Seismic data were acquired in the Kylylahti mining area in eastern Finland over severely folded, faulted and subvertical Kylylahti structure, and associated mineralization. We performed 3D ray-based imaging, i.e., industry-standard Kirchhoff migration and its improved version (coherency migration, CM), and wave-equation-based migration, i.e., reverse time migration (RTM) using a velocity model built from first-arrival traveltime tomography. Upon comparing the three different migrations against available geological data and models, it appeared that CM provided the least noisy and well-focused image, but failed to image the internal reflectivity of the Kylylahti formation. RTM was the only method that produced geologically plausible reflections inside the Kylylahti formation including a direct image of the previously known shallow massive sulfide mineralization.

Genesis of greenockite (CdS) and associated sulphide‐gold mineralization from Mahakoshal belt, Central Indian Tectonic Zone

The Zn‐Cd‐S critical minerals system is a significant mineralogical indicator of hydrothermal ore‐forming processes. The understanding of greenockite (CdS) formation in natural mineral systems is very restricted due to low crustal abundances (Cd <0.2 ppm). We report the first occurrence of greenockite from the Bagada orogenic gold prospect, Paleoproterozoic Mahakoshal belt, Central Indian Tectonic Zone (CITZ). This provides an ideal opportunity to access the occurrence and its genesis. Greenockite occurs in discrete sheared quartz veins hosted in phyllites. Sulphide mineralization is closely associated with hydrothermal chlorite alterations. Pyrrhotite, arsenopyrite, pyrite, and chalcopyrite assemblages are formed at high temperatures, while sphalerite and galena precipitated when the temperature decreased. Greenockite, native silver and bismuth with gold precipitated during the breakdown of arsenopyrite to scorodite in progressively oxidizing conditions. Greenockite precipitation occurred in a transforming hydrothermal environment from a reducing to an oxidizing one during late‐stage hydrothermal alteration. Sphalerite and chlorite thermometry yielded temperatures in the range from 266 to 366°C for this late‐stage hydrothermal alteration. Textural relations show two modes of occurrence of greenockite, one (Gck‐1) as exsolution within sphalerite (Sp‐2) and the other (Gck‐2) occurring as a discontinuous rim replacing the Cd‐rich sphalerite (Sp‐3). The Gck‐1 contains high Zn and low Cd, while as compared to Gck‐2. Zinc and Cd in greenockite show diadochy relation (Zn2+ ↔ Cd2+). Laser ablation ICPMS analyses of sphalerite (Sp‐2) reveal remarkably high Cd contents (1.9–12 wt%). Cd >0.02 ppm suggests possible Cd derivation from sphalerite (Sp‐2) under variable fS2, T, pH, fO2 conditions, fluid–rock interaction, and change in the Zn/Cd ratio. Sphalerite compositions display a low Zn/Cd (av.22) ratio and high temperature of formation, with characteristics intermediate between volcanogenic massive sulphides (VMS) and magmatic‐hydrothermal Cu‐Pb‐Zn system.

MINDeSEA: exploring seabed mineral deposits in European seas, metallogeny and geological potential for strategic and critical raw materials

Abstract This study summarizes a compilation of studies and cartographical work on seabed mineral deposit types in pan-European seas developed under the GeoERA-MINDeSEA project. In total, 692 occurrences and 1194 individual mineral samples of volcanogenic massive sulfides and hydrothermal mineralization, ferromanganese crusts, phosphorites, marine placer deposits, polymetallic nodules, and their associated strategic and critical raw material (CRM) elements have been characterized. The GeoERA-MINDeSEA project has been built based on extensive studies carried out previously, which include geophysical surveys, sampling stations, underwater photography and remotely operated vehicle (ROV) surveys, and mineralogical, geochemical and isotopic studies. This study develops pan-European and national databases, and expands strategic and CRM knowledge through a compilation of mineral potential and metallogenic studies of CRM resources in European seas. For the first time, the GeoERA-MINDeSEA portal publishes harmonized marine mineral resource information, case studies and maps, and identifies potential areas for responsible resource exploration and extraction, strategic management, and marine spatial planning. This study also provides recommendations for future target areas, studies and standards to be used across Europe as part of this project.

On the matildite–bohdanowiczite solid-solution series

AbstractA high-grade ore sample from the Cu–Zn–Au Photo Lake volcanogenic massive sulfide deposit (Flin Flon–Snow Lake greenstone belt, Manitoba, Canada) contains a Bi–Ag sulfo-selenide with a composition situated approximately in the middle of the S–Se substitution range (Se ≈ 0.86 apfu and S ≈ 1.05 apfu). These new data, combined with a literature compilation of all publicly available matildite and bohdanowiczite compositional data, reveal a nearly complete range of S–Se substitution between these two minerals, with only the section between BiAgSe0.78S1.18 and BiAgSe0.25S1.75 – about a quarter of the complete S–Se range – not yet documented. These observations suggest that a complete solid-solution series between matildite and bohdanowiczite, as previously suspected, might exist and in a manner similar to the galena–clausthalite complete solid-solution series.

Archean Pb isotope variability tracks crust-mantle fractionation, granite production, and ore deposit formation

Various geological processes that affect Earth's crust may be encoded into isotopic tracers preserved in rocks and minerals. The enhanced sensitivity of U, Th, and Pb to crustal fractionation processes allows Pb isotopes to complement information from the Nd and Hf isotope systems. However, melt fractionation, crustal contamination and recycling, hydrothermal fluid flow and fluid-rock interaction, and other processes in the continental crust can lead to mixing of Pb isotopic signatures. Here, we report new Pb isotopic data from granite-K-feldspar and integrate these data with published Pb isotope ratios from granite K-feldspar and Pb-rich ores across the Yilgarn Craton in Western Australia. The aim of this study is to explore how the variability of Pb isotope ratios and derivative parameters can be used to gain information on specific geological processes occurring throughout the crustal column. We develop a model that subdivides different sampling media into chemical process groups and links their initial Pb signatures to Pb source regions and fractionation processes at various locations within the crust and upper mantle. Equilibration of Pb signatures with a primary mantle source reservoir (in part represented by volcanic-hosted massive sulfides) is contrasted with granite formation in the mid to lower crust (granite K-feldspar), and mineralization of ore deposits in the mid to upper crust (Pb-rich ores). Spatial trends similar to those in Nd and Hf isotopic data are recorded by Pb isotopic derivative parameters (μ = source 238U/204Pb, ω = 232Th/204Pb, and Δt - the difference between true sample age and Pb model age) calculated for komatiite-hosted Ni sulfide ores, granite K-feldspar, and volcanic-hosted massive sulfide (VHMS) ores. The significance of subtle differences in absolute values of derivative parameters is supported by the diversity of Pb isotope ratios, Pb model ages, and ∆t as tracked by a statistical metric, quantifying the variability of Pb sources involved in the formation of different chemical process groups. Generally greater variety in an older terrane (Youanmi) documents more ancient and recycled continental crust as compared with more homogeneous Pb isotopic signatures in a younger terrane (Eastern Goldfields Superterrane). The Pb signatures are interpreted, in part, to relate to the timing of source fractionation in the upper mantle with a legacy of this source signal preserved through various depths in the lithospheric section. The least radiogenic VHMS ore samples appear to provide a good approximation of mantle Pb signatures, indicated for example by a deficit in 206Pb and 208Pb relative to the other process groups. A significant heterogeneity recorded in Pb isotopic data from Pb-rich gold ores is explained by the interplay of hydrothermal fluids with diverse sources leading to the mineralization of gold deposits (e.g., leaching of Pb from surrounding rocks or fluid mixing). Such gold ore Pb signatures are distinct from other process groups, which together track sources less heterogeneous in age and/or U and Th.

Mineralogy and geochemistry of platinum-group elements in the zoned mafic-ultramafic intrusions of the Uralian Platinum belt, Russia

Three styles of platinum-group element mineralization occur within the Ural-Alaskan type complexes of the Uralian Platinum belt: chromite-platinum, noble metal, and noble metal-copper ones. They are associated with dunite and chromitite (chromite-platinum), pyroxenite (noble metal) and gabbro (noble metal-copper). Three common platinum group element distribution patterns are observed for dunite and chromitite: (1) M-shaped (defined by positive Ir and Pt anomalies); (2) with positive Ir-Rh(Pt) anomalies; and (3) W-shaped with positive Os and Pt, or Os and Rh anomalies. In contrast, pyroxenite and gabbro are enriched in Pd and Au. The PGM assemblages correlate to the PGE + Au distribution patterns as exemplified by the predominance of Ir-rich Pt-Fe alloys within dunite and chromitite. The noble metal assemblages of pyroxenite and gabbro comprise tellurides, arsenides, and various Pd minerals, as well as native gold and Au-Ag alloy. An indicative Pd/Ir ratio in a succession dunite-chromitite-gabbro increases from 0.04 to 148 with a maximum value of ~5000 in massive sulfide ore of the Volkovsky that is attributable to the contrasting magma compositions defining chromite vs sulfide controls over PGE concentration.

Genetic relationship between the Maoping Pb-Zn deposit and paleo-oil reservoir in the northern Yunnan-Guizhou depression: Evidence from bitumen trace elements and the in-situ sulfur isotope of pyrite associated with bitumen

The coexistence of numerous Mississippi Valley-type (MVT) Pb-Zn deposits and oil/gas reservoirs in the world demonstrates that a close genetic link between them. The northern Yunnan–Guizhou depression (NYGD) is a tectonic unit containing Pb–Zn deposits, paleo-oil reservoirs and shale gas. However, previous studies on the relationship between hydrocarbon accumulation and Pb–Zn mineralization have been ignored. The Maoping Pb–Zn deposit is a large-sized MVT deposit in the NYGD where a large amount of solid bitumen (i.e., a paleo-oil reservoir) occurs, and it is an ideal area to study the relationship between hydrocarbon accumulation and lead–zinc mineralization. In this paper, the bitumen and pyrite associated with bitumen from the Xujiazhai (discovered in this study) and Xiaocaoba paleo-oil reservoirs and the Maoping Pb–Zn deposit are researched. Geological observation has revealed that bitumen occurs in dissolution pores, fractures and intercrystalline pores in dolomite of the Upper Devonian and Carboniferous. The bitumen from Xujiazhai, Maoping and Xiaocaoba with high and similar Raman equivalent reflectance (RmcRo%) indicates they are in over-mature level and may be derived from the cracking of early-accumulated crude oils. The bitumen in the Xujiazhai paleo-oil reservoir and Maoping deposit has an abundant Pb and Zn content, indicating petroleum liquids may act as the transporting agents of metallogenic metal elements, carrying them to sites where mineralization may take place. The source rocks may have provided not only the oil for paleo-oil/gas reservoirs, but also a portion of ore metals for the Pb-Zn mineralization. The bacterial sulfate reduction (BSR) and thermochemical sulfate reduction (TSR) processes were recorded by the pyrite in the paleo-oil reservoir, which was consistent with the mechanism of reduced sulfur formation in the Maoping deposit. In addition, the large negative (−27.7‰ to −5.7‰) and positive (.9‰ to 19.2‰) δ34S values of the pyrite associated with the bitumen in the paleo-oil reservoir were similar to those of the sulfide in the Maoping deposit. We believe that the formation and evolution of the paleo-oil reservoirs are closely related to the metallogenic process of the Maoping Pb–Zn deposit, and the sulfides in them have the same sulfur source and formation mechanism as reduced sulfur. BSR phenomena could occur in prior to migration of the hydrocarbons into the reservoir or low mature oil stage in paleo-oil reservoir; a small amount of H2SBSR was combined with metal ions in ancient oil reservoirs and deposits to form early subhedral, xenomorphic granular, fine-grained strawberry aggregate pyrite and/or gelatinous sphalerite. The paleo-gas reservoir formed by the evolution of the paleo-oil reservoir in the main metallogenic period potentially participated in the mineralization; that is, organic gas acted as a reducing agent and transformed SO42− in the upper Devonian Zaige Formation gypsum strata on the periphery of the Maoping lead–zinc mining area into H2STSR through TSR, providing reduced sulfur and creating the environmental conditions for mineralization. During or after the transformation of the paleo-oil reservoir to a paleo-gas reservoir, the decoupling of metals and organic complexes may have provided the ore metals for mineralization. Massive sulfide precipitation may have occurred during or after the paleo-oil reservoir cracked into the paleo-gas reservoir.

Comparison of Handheld and Echelle Spectrometer to Assess Copper in Ores by Means of Laser-Induced Breakdown Spectroscopy (LIBS)

Its properties make copper one of the world’s most important functional metals. Numerous megatrends are increasing the demand for copper. This requires the prospection and exploration of new deposits, as well as the monitoring of copper quality in the various production steps. A promising technique to perform these tasks is Laser Induced Breakdown Spectroscopy (LIBS). Its unique feature, among others, is the ability to measure on site without sample collection and preparation. In this work, copper-bearing minerals from two different deposits are studied. The first set of field samples come from a volcanogenic massive sulfide (VMS) deposit, the second part from a stratiform sedimentary copper (SSC) deposit. Different approaches are used to analyze the data. First, univariate regression (UVR) is used. However, due to the strong influence of matrix effects, this is not suitable for the quantitative analysis of copper grades. Second, the multivariate method of partial least squares regression (PLSR) is used, which is more suitable for quantification. In addition, the effects of the surrounding matrices on the LIBS data are characterized by principal component analysis (PCA), alternative regression methods to PLSR are tested and the PLSR calibration is validated using field samples.

New Mineral Occurrences in Massive Sulfide Deposits from Mănăilă, Eastern Carpathians, Romania

The massive sulfide deposits (VMS) from Mănăilă are associated with the metamorphic formations of the Tulgheș Lithogroup from the Bucovinian Nappes of the Crystalline-Mesozoic Zone in the Eastern Carpathians, Romania. The following types of ore were identified: pyrite-polymetallic, pyrite copper, compact and precompact copper, and quartz-precompact copper. The polymetallic mineralization consists of pyrite, chalcopyrite, sphalerite, galena, and subordinately arsenopyrite and tennantite. The copper, especially the quartz-copper mineralizations, have a distinct mineralogical composition compared to the other metamorphosed mineralizations of the Tulgheș Lithogroup. These types of deposits from Mănăilă contain large amounts of bornite and chalcocite along with chalcopyrite. Tennantite is abundant and has up to a 3.57 wt.% of bismuth. Wittichenite was identified for the first time in the metamorphic mineralizations and mawsonite was identified as the first occurrence in Romania. An unnamed mineral with the formula: Cu,Fe11Pb,AgS7 was also identified, belonging to the sulfides group. The compact and precompact pyrite-rich ores, located in sericite ± quartzite schists and covered by rhyolitic metatuffs, are of hydrothermal-sedimentary type metamorphosed in the greenschist facies. The source of the quartz-copper mineralization would be the retromorphic or metasomatic hydrothermal solutions that circulated through major fractures.

Filizchay pyrite-polymetallic deposit (the southern slope of the Greater Caucasus) – as a typical representative of the SEDEX type pyrite deposits


 
 
 The article has been devoted to one of the largest deposits of the southern slope of the Greater Caucasus – the Filizchay pyrite-polymetallic deposit. It has been found that the main morphology peculiarity of the pyrite-polymetallic deposit of the Filizchay deposit is that it is a single, compact sheet-like body composed mainly (at 90-95%) by the aggregates of the sulfide ores which are based on pyrite, sphalerite, galena and to a far lesser extent chalcopyrite and pyrrhotite. The carbonate minerals played a subordinate role in the deposit composition and quartz, sericite and chlorite – even less. The pyrite –polymetalic ores of the deposit are characterized by the following main mineralogical-textural varieties of ores: layered-bedded pyrite-polymetallic, massive sulfur-pyrite, massive pyrite-polymetallic, spotted-disseminated pyrite-polymetallic and vein-disseminated pyrite-polymetallic. The vein-disseminated ores are adjacent to the deposit on the footwall and are considered as independent bodies. Two industrial-techno- logical types of ores, oxidized and pyrite-polymetallic, have been distinguished at the deposit. The latter is in turn divided into two grades: mixed and primary ores. These three varieties of ores differ in the content of the oxidized lead forms. The ores with a content of the oxidized lead speciation above 60% have been classed as oxidized ores, those from 20% to 60% as mixed and those below 20% as primary. The Filizchay deposit consists of thin-bedded massive sulfides with shales, siltstones or sandstones interbeds («ore flysch») which have been formed exclusively or mainly as a result of the exhalative processes on the seabed and differ from massive sulfide deposits in volcanic rocks. On the basis of this and also according to the geological structure, the reserves of the valuable Zn + Pb components of the deposit belong to the SEDEX type that is the most important source of lead, zinc and silver. The deposit had been developing for a long time starting from the period of sedimentation and up to the ore’s formation of the copper-pyrrhotite stage. The lower age limit of the mineralization is determined by the presence of the hydrothermal-sedimentary ores of the Upper Pliensbachian. The upper age limit is established by the presence of the pebbles of the hydrothermally altered rocks and by their sulfide ores in the conglomerates underlying the deposits of the lower parts of the Upper Jurassic.
 
 

Authigenic Ti mineralization as an indicator of halmyrolysis of carbonatesulfide-hyaloclastite sediments in Urals massive sulfide deposits

Research subject. The horizons of ferruginous sedimentary rocks in the massive sulfide deposits of the Urals.Aim. To estimate the Ti behavior upon halmyrolytic transformation and lithogenesis of calcareous hyaloclastites and carbonatesulfide-hyaloclastite sediments.Materials and methods. Microtextures of authigenic aggregates of Ti minerals (anatase, rutile, titanite) in jasperites and gossanites of various Urals massive sulfide deposits were studied. The minerals were identified using microscopic and electron microscopic methods, as well as electron back-scattered diffraction.Results. Upon partial halmyrolysis of calcareous hyaloclastites, Ti was removed with the formation of authigenic anatase rims around hematitized hyaloclasts. The full transformation of hyaloclastites to hematite-quartz jasperites resulted in decomposition of authigenic Ti minerals. Authigenic rutile and titanite formed in gossanites (hematite-quartz and hematite-chlorite products of submarine oxidation of calcareous sulfide-hyaloclastite sediments). The occurrence of abundant bacteriomorphic structures in corroded hyaloclasts indicates a significant role of bacteria in halmyrolysis.Conclusions. Titanium for the formation of Ti minerals in ferruginous sediments was sourced from hyaloclastites. The halmyrolysis of calcareous hyaloclastite sediments and related formation of jasperites occurred under alkaline conditions favorable for the transportation of Ti in the form of hydroxycarbonate complexes. The formation of rutile instead of anatase was associated with lower pH values (<5) due to oxidation of pyrite in sulfide-bearing hyaloclastite sediments. Titanite formed as a result of further alteration of Ti-bearing phases. Our results solve the fundamental problem of Ti mobility during halmyrolysis of hyaloclastites, which contradicts its commonly accepted immobility in hydrothermal processes.

The improvement of sparsity gravity inversion using an adaptive lanczos bidiagonalization method

Inversion of gravity data is one the important steps in the interpretation of practical data. The detection of sharp boundaries between anomalous bodies and host rocks is an interesting point in the geological frameworks. The gravity inversion with sparsity constraint is a useful method to recover block subsurface density distribution, which is efficiently used for the quantitative interpretation of gravity data. The reweighted regularized method is a useful method to solve the inverse problem. However, in this type, we must face the updating gravity forward matrix and large matrix operation. The application of Lanczos bidiagonalization method can reduce the size of data and matrix in the inversion to resolve the large scale inversion problem. However, a very important problem is not resolved, which is update of reweighted forward matrix and new Lanczos bidiagonalization matrix. Here, an adaptive Lanczos bidiagonalization method is studied to select the Lanczos bidiagonalization factor. And a new projected method with adaptive Lanczos bidiagonalization method is study to avoid the updating sparsity reweighted function. We calculate the reweighted forward matrix and Lanczos bidiagonalization matrix only one time, which can essentially reduce the computational complexity. The inversion results of synthetic data show that the new improved method is faster and better than common reweight regularized Lanczos bidiagonalization method to produce an acceptable solution for focusing inverse problem. The improvement of adaptive Lanczos bidiagonalization in sparsity gravity inversion is also tested on gravity data collected over the Mobrun massive sulfide ore body in Noranda, Quebec, Canada. The inversion results indicate a remarkable correlation with true structure of the ore body that is achieved from drilling data.

Investigating Metals and Metalloids in Soil at Micrometric Scale Using µ-XRF Spectroscopy—A Case Study

Micrometric 2D mapping of distinct elements was performed in distinct soil grain-size fractions of a sample using the micro-X-ray Fluorescence (µ-XRF) technique. The sample was collected in the vicinity of São Domingos, an old mine of massive sulphide minerals located in the Portuguese Iberian Pyrite Belt. As expected, elemental high-grade concentrations of distinct metals and metalloids in the dependence of the existent natural geochemical anomaly were detected. Clustering and k-means statistical analysis were developed considering Red–Green–Blue (RGB) pixel proportions in the produced 2D micrometric image maps, allowing for the identification of elemental spatial distributions at 2D. The results evidence how elemental composition varies significantly at the micrometric scale per grain-size class, and how chemical elements present irregular spatial distributions in the direct dependence of distinct mineral spatial distributions. Due to this fact, elemental composition is more differentiated in coarser grain-size classes, whereas griding-milled fraction does not always represent the average of all partial grain-size fractions. Despite the complexity of the performed analysis, the achieved results evidence the suitability of µ-XRF to characterize natural, heterogeneous, granular soils samples at the micrometric scale, being a very promising investigation technique of high resolution.

Deep-sea mineral deposits as a future source of critical metals, and environmental issues - a brief review

For the whole world to deliver net zero by 2050, large-scale mining is more critical for metals such as lithium, cobalt, platinum, palladium, REE, gallium, tungsten, tellurium, and indium as these metals are essential for green technology applications such as making wind turbines, solar panels, fuel-cells, electric vehicles, and data storage systems required to transition to a low-carbon economy. Since land-based mineral deposits are depleting fast, seabed resources are seen as a new resource frontier for mineral exploration and extraction. They include mainly deep-ocean mineral deposits, such as massive sulfides, manganese nodules, ferromanganese crusts, phosphorites, and REE-rich marine muds. Manganese nodules contain mainly manganese and iron, but also valuable metals like nickel, cobalt, and copper, as well as REE and platinum, which are used in making several high-technology and green technology products. For example, deep-sea mud enriched in REE (> 2000 µg/g) was found in the western North Pacific Ocean. High concentrations of REE range from 1,727 to 2,511 μg/g in the crust samples collected from the Afanasy Nikitin Seamount (ANS) in the Indian Ocean. However, these deposits usually have lower REE grades than land-based REE deposits such as carbonatite-hosted deposits but form greater potential volumes. Though the mining companies and their sponsoring countries are in the process of developing the required technologies to mine the three deep-sea environments: abyssal plains, seamounts, and hydrothermal vents, due to severe concerns about the possible environmental damages, the International Seabed Authority (ISA) has not granted any mining permissions so far, although deep-sea mining becomes inevitable in the future green energy revolution.

Study of the effects of roasting and sodium thiosulfate on the extraction of silver from Volcanic Massive Sulfide ore

The main objectives of this article were to firstly decrease the amount of sulfide in the (Volcanic Massive Sulfide –VMS) in the eastern Sudan (Ariab) area through a roasting pretreatment, secondly determine the best and optimum (thiosulfate concentration – ammonia concentration – copper sulfate concentration - leaching time – pH) for extracting silver sulfide metal (Ag2S) also known as argentite from the same ore, thirdly using sodium cyanide concentration equal to the optimum thiosulfate concentration obtained from the experiments to determine which solvent is better at the same concentrations thiosulfate or cyanide.The leaching process took place at different concentrations, times, following a roasting pre-treatment at (300–400-500–600-700 °C), The Analytics of (ICP) and (XRF) showed that silver concentration is (10.91 PPM), iron is (15.76 PPM) and copper is (119.16 PPM), and the (SEM) analysis showed that Sulfur is present in the proportion of (26 %) in the ore, and from the study of fractions it became clear that the highest presence of silver was at the size (-106 + 75) micron.It was found that the best roasting temperature was (700 °C), and the best extraction using sodium thiosulfate was (61.06 %) at thiosulfate concentration (0.2 M) and ammonia concentration (0.2 M), time (6) hours, copper sulfate concentration (0.05 M), pH (10) and pulp density (25 %) at room temperature. As for sodium cyanide at the same concentration (0.2 M), it was found that the extraction was (49.47 %) at time (6) hours, pH (10), and pulp density (25 %). At room temperature, it was clear that cyanide was less efficient at (0.2 M) concentration than thiosulfate in dissolving silver.

Automated Detection of Hydrothermal Emission Signatures From Multibeam Echo Sounder Images Using Deep Learning

Seafloor massive sulfide deposits have attracted attention as a mineral resource, as they contain a wide variety of base, precious, and other valuable critical metals. Previous studies have shown that signatures of hydrothermal activity can be detected by a multi-beam echo sounder (MBES), which would be beneficial for exploring sulfide deposits. Although detecting such signatures from acoustic images is currently performed by skilled humans, automating this process could lead to improved efficiency and cost effectiveness of exploration for the seafloor deposits. Herein, we attempted to establish a method for automated detection of MBES water column anomalies using deep learning models. First, we compared the “Mask R-CNN” and “YOLO-v5” detection model architectures, wherein YOLO-v5 yielded higher F1 scores. We then compared the number of training classes and found that models trained with two classes (signal and noise) exhibited superior performance compared with models trained with only one class (signal). Finally, we examined the number of trainable parameters and obtained the best model performance when the YOLO-v5l model with a large trainable parameters was used in the two-class training process. The best model had a precision of 0.928, a recall of 0.881, and an F1 score of 0.904. Moreover, this model achieved a low false alarm rate (less than 0.7%) and had a high detection speed (20−25 ms per frame), indicating that it can be applied in the field for automatic and real-time exploration of seafloor hydrothermal deposits.

Impacts of the first deep-sea seafloor massive sulfide mining excavation tests on benthic communities

Japan undertook the first ever tests of deep-sea seafloor massive sulfide (SMS) excavation in 2017 in the Okinawa Trough. This study examines infauna from several nearby stations before and up to 3 yr after disturbance. Distance from excavation, current direction, seafloor topography, and modeled and observed deposition were used to classify the level of impact of each station. Metal concentrations were analyzed, as were nanofauna (2-32 µm), meiofauna (32-300 µm), and macrofauna (>300 µm). Elevated Cd, Pb, Hg, Zn, Fe, and Cu were confirmed as indicators of sedimentation from the SMS extraction. Benthic communities appeared altered by the disturbance test, with different size classes showing different levels of response and recovery. Nanofaunal and meiofaunal abundances appeared to take several weeks to show impacts from the disturbance and may have returned to pre-test levels within 1 yr, but changes to nematode community structure persisted longer. In contrast, macrofaunal abundances and diversity appeared to decrease immediately, and possibly remained depressed compared to pre-test levels at impacted sites at least 3 yr later. In addition, meiofaunal nematode:copepod ratio and macrofaunal percent composition of polychaetes, along with several nematode taxa, may serve as useful bioindicators of SMS mining. The small scale of disturbance requires caution when extrapolating to full-scale mining, but these results suggest current direction and topography greatly influence the extent of mining impacts; in addition, several metals may be useful for identifying the mining footprint. Biological results indicate that larger macroinfauna may be less resistant and resilient to mining impacts than smaller meiofauna and impacts from even small-scale mining activities may persist for at least 3 yr.

Distribution of critical metals in evolving pyrite from massive sulfide ores of the Iberian Pyrite Belt

With >90 known deposits containing original reserves of >2400 Mt of sulfide ore, the Iberian Pyrite Belt (IPB) is the largest volcanogenic massive sulfide (VMS) province on Earth. In these evolving mineral systems, texturally different pyrite exhibits characteristic mineralogy and trace element fingerprints. Pyrite (Py-1), which is well preserved in the polymetallic ores that crystallized at the earliest stage of VMS deposit formation, consists of kernels of pyrite framboids surrounded by concentric colloform bands and ended by faceted outlines. It is rich in some metals like Pb, Zn, Sb and As (mostly hosted as nano-to-micron-sized particles, including galena, tetrahedrite and arsenopyrite) but depleted in Cu, Co and Bi. In contrast, pyrite from the pyritic and Cu-rich ore overprinted by late fluids exhibits spongy-looking (Py-2) or homogenous (Py-3) cores surrounded by external facets with crystallographic continuity across the whole single grains due to re-crystallization. Py-2 is depleted in most trace elements with the exception of Au and Bi, which occur both in solid solutions and as nano-to-micron-sized inclusions. Py-3 has the highest Cu, Ag, Co and Ni (mainly associated to nano-to-micron-sized particles of tennantite, chalcopyrite and gersdorffite) and the lowest Au contents in the form of native gold. The progressive increase in metal contents from inner to outer parts of Py-1 matches with the onset of the economic metal endowment of VMS deposits in the IPB, whereas Py-2 and Py-3 are associated with metal shoot processes that led to both leached and high-grade ores, very likely when mafic rocks were emplaced into the footwall of the deposits.

Exceptional preservation of organic matter and iron-organic colloidal mineralization in hydrothermal black smoker-type sulfide mineralization from the Paleoarchean seafloor

Fossil organic matter (OM) in Paleoarchean rocks is an invaluable tracer of ancient life, yet it is often contentious due to low preservation potentials of its original organic molecular characteristics under generally high metamorphic grades. This study reports on exceptionally preserved OM within black smoker-type sulfide mineralizations from the 3.24 billion-years-old Sulphur Springs volcanic-hosted massive sulfide deposit, East Pilbara Terrane, northwestern Australia. Fine scale mineralogical and organic molecular variations – documented by SEM and TEM techniques, Raman and FTIR Spectroscopy, as well as ToF-SIMS analysis – trace the formation of millimetre-scale pyritic hydrothermal orifices. Overmature OM (≳200–250 °C) enriched in aromatic hydrocarbons occurs within earliest formed colloform-banded pyrite that could have precipitated at high temperature upon mixing of hot hydrothermal fluids with cold seawater. In contrast, mature OM (within the catagenesis window; ∼100–150 °C) with lower proportions of aromatic hydrocarbons occasionally occurs alongside pyrite within barite near the inner paleofluid conduits of the hydrothermal orifices. A deposition of this OM generation from cooler fluids enriched in sulfate during waning hydrothermal activity is corroborated by its association with original mineralogy, particularly the occurrence of isolated nanoinclusions of OM within hydrothermal barite away from grain boundaries or fissures and cracks, which renders impossible an origin from post-depositional hydrocarbon migration. When compared to the overmature OM within colloform-banded pyrite, the better-preserved inner OM not only contains less abundant, smaller, and less ordered aromatic hydrocarbons, but also higher amounts of aliphatic molecules with longer chain lengths and higher proportions of carbonyl and amide functional groups. Although the latter characteristics are consistent with contributions by microbial biomass, abiotic origins are equally plausible because hydrothermal processes can produce OM with similar organic molecular attributes. Irrespective of these uncertainties on the ultimate sourcing of OM, common intergrowths of the cooler OM with nanoscopic iron oxides – hematite and lesser magnetite – hint at its hydrothermal deposition from colloidal particles that have been stabilized by iron-organic complexation. Further research is required to ascertain the significance of this process for the hydrothermal cycling and release of organic carbons and bound iron into the Paleoarchean oceans. Collectively, our results show that ancient marine hydrothermal systems can preserve OM with differing degrees of thermal degradation, which allows for insights into its sourcing, cycling, and deposition.

The state of gold in phases of the Cu-Fe-S system: In situ X-ray absorption spectroscopy study

Chalcopyrite and bornite are the main Au-bearing minerals at Cu porphyry deposits, volcanogenic massive sulfide (VMS) deposits, Cu-Ni deposits of the mafic magmatic complexes, and ores of submarine sulfide edifices. Bornite and intermediate solid solutions with wide compositional variations (bnss and iss – high-temperature chalcopyrite, correspondingly), which can scavenge economic concentrations of Au, appear in the Cu-Fe-S system at ore-forming conditions. However, the state of Au in bnss and iss is yet unknown. To solve this conundrum, we synthesized samples with net chemical composition of bnss and iss, studied them by in situ X–ray absorption spectroscopy (XAS), and used the experimental data to explain the Au distribution among natural ore-forming minerals. The sulfide samples were obtained at 495–700 °C in Au-saturated system by means of salt flux method. The bnss contained ∼1.2–1.6 log units more Au than iss: up to 18 wt.% Au in bnss vs 0.4 wt.% Au in iss at 700 °C. An increase of temperature resulted in the sharp increase of Au concentration in both phases, ∼1 log unit per 100 °C at f(S2) close to S(l) saturation. Analysis of Au L3-edge spectra recorded at 25–675 °C revealed that at 25 °C Au exists mainly in the metallic state. At t > 500 °C the spectral features of Au° disappear, and “chemically bound” Au predominates. The Au form of occurrence in the iss field is interpreted as Au-bearing clusters with a stromeyerite-like (CuAgS) structure. Digenite Cu2–xS and bnss contain Au in a mixture of stromeyerite-like and petrovskaite-like (Au0.8Ag1.2S) clusters. The chemical composition of both forms is close to CuAuS, where the nearest Au neighbors are two S atoms at RAu-S = 2.34–2.36 Å. Results of the present study allow to determine the state of Au and its concentration in the main Cu-bearing minerals of sulfide ores as a function of the T-f(S2)-compositional parameters. Due to the sharp increase of the CuAuS clusters stability with increasing temperature, in high-temperature ores formed at t > 350 °C Au enriches Cu-bearing minerals in comparison with Cu-free or Cu-deficient ones. As a result, in these ores native gold, being a product of decomposition of the Au-bearing clusters, is associated with Cu-rich minerals – chalcopyrite, bornite, digenite, chalcocite.