Polymetallic Sulfide Deposits Research Articles

Geophysical VLF prospecting for vein-type gold-bearing polymetallic sulphide deposits in the Sudetes (SW Poland)

Geophysical VLF prospecting for vein-type gold-bearing polymetallic sulphide deposits in the Sudetes (SW Poland)

Carbonate rocks as natural buffers: Exploring their environmental impact on heavy metals in sulfide deposits

Carbonate rocks are closely related to the genesis and spatial distribution of polymetallic sulfide deposits. The natural buffering of carbonate rocks can reduce the ecological impact of heavy metals produced by mining and smelting. Ignoring the buffering effect of carbonate rocks on the heavy metals in the mine environment leads to inaccurate ecological risk assessment, wasting land resources and funds. This study investigates Cd, Zn, and Pb distribution and speciation in the water and soil-rice system in the polymetallic sulfide deposit at Daxin, Guangxi. The study aims to reveal the effects of the natural buffering of carbonate rocks on the migration and transformation of heavy metals. The results show that the water Zn and Cd concentrations decreased from 1857.0 to 0.9 mg L−1 to 0.16 and 0.001 mg L−1, respectively, from the mining area to 4 km downstream. The natural buffering of carbonate increases the water pH from 2.80 to 7.64, resulting in a tendency for Cd, Zn, and Pb to separate from the aqueous phase and enrich the sediments. Soil Cd content in the mining area reached 110.0 mg kg−1 (mean value 55.88 mg kg−1), and rice Cd seriously exceeded the maximum limit. However, the weathering of carbonate reduces the migration ability and bioavailability of Cd. Soil Cd is mainly in the Fe–Mn bound and carbonate-bound fractions, resulting in lower Cd content in downstream soils (mean value 2.73 mg kg−1). Soil CaO, tFe2O3, and Mn hindered the uptake of soil Cd by rice rendering a lower exceedance of Cd in downstream rice. Therefore, this study recommends a farmland management plan under the premise of rice Cd content and integrated soil Cd content, which ensures food safety and fully utilizes farmland resources. This result provides a scientific basis for ecological risk assessment, mine environmental protection, and management in the carbonatite sulfide mine environment.

A case study on marmatite- pyrite/pyrrhotite selective flotation with two-step pulp regulation

Zinc occupies a vital position in modern industrial production, and zinc metal is mainly extracted from marmatite or sphalerite. Marmatite or sphalerite is often associated with pyrite and pyrrhotite in natural polymetallic sulfide deposits. Therefore, how to well achieve the selective separation of marmatite or sphalerite from associated pyrite and pyrrhotite is an important issue, because it is directly related to the efficient and sustainable utilization of zinc-bearing sulfide mineral resources. In this paper, a systematic research taking the selective separation of marmatite from high-sulfur sulfide ores as its core, was conducted. The results confirmed that pulp redox potential (Eh) as well as dissolved oxygen (DO) dominated the selective separation of marmatite from associated pyrite and pyrrhotite, and the Zn recovery and Zn grade of zinc concentrates could be greatly improved by controlling Eh. As a result, an effective and feasible operating mechanism with two-step Eh regulation was first established. The findings are expected to help scholars understand the marmatite-pyrite/pyrrhotite (Zn-S) selective flotation better, favor the beneficiation of high-sulfur polymetallic sulfide ores in study or practice, and provide important inspirations for the theoretical research or practical utilization on other similar sulfide resources, especially those containing pyrrhotite.

Genesis of the Questa Mo Porphyry Deposit and Nearby Polymetallic Mineralization, New Mexico, USA

Abstract The Oligocene Latir magmatic center in northern New Mexico is an exceptionally well exposed volcano-plutonic complex that hosts a variety of magmatic-hydrothermal deposits, ranging from relatively deep, F-rich porphyry Mo mineralization to shallower epithermal deposits. We present new whole-rock chemical and isotopic data for plutonic rocks from the Latir magmatic center, including extensive sampling of drill core samples of intrusive rocks from the Questa porphyry Mo deposit. These data document temporal chemical trends of porphyry-related mineralization that occurred after caldera-forming magmatism and during postcaldera batholith assembly. Silicic magmas were generated multiple times throughout the history of the Latir magmatic center, but few are associated with the formation of a mineral deposit. Whole-rock trace element ratios and Sr, Nd, and Pb isotope compositions vary throughout the protracted history of silicic magmatism. The caldera-forming ignimbrite and early phase of postcaldera intrusions are unmineralized, more enriched in high field strength elements, and generally contain less radiogenic Sr and Pb and more radiogenic Nd than later intrusions. The Questa porphyry Mo deposit formed immediately after the most isotopically primitive phase of the batholith was assembled, ruling out simple reworking of juvenile mantle-derived crust as the source for mineralizing magmas. Rhyolite dikes associated with polymetallic sulfide deposits intruded ~800 k.y. after Mo mineralization, and Nd isotope data indicate that these dikes are associated with different batches of magma and are unrelated to the Mo-mineralizing intrusions at the Questa mine. Together, these data indicate that the source of magmas changed significantly throughout the 10-m.y. history of the magmatic center. We assess multiple genetic models for porphyry-related magmatism against this data set, favoring models with discrete periods of magma genesis from a deep hybridized zone in the lower crust giving rise to the punctuated periods of mineralization. These observations suggest that the formation of mineral deposits within a central magmatic locus is likely the result of the piecemeal assembly of individual hydrothermal-magmatic systems, and that distal and younger polymetallic mineralization commonly observed near known porphyry deposits represents decoupled processes.

Origin of Groundwater Salinity in the Draa Sfar Polymetallic Mine Area Using Conservative Elements (Morocco)

In the Marrakech region of Morocco, where water resources are particularly limited, excessive salinity has been measured in the water from some wells intended for human consumption and irrigation. Moreover, the start-up of a mine for the exploitation of a polymetallic sulfide deposit and the progress of the exploitation work have revealed the existence of very saline deep groundwater with a total mineralization of over 80 g/L. The hydrogeochemical study using conservative elements has helped to understand the origin of the groundwater salinity in the Draa Sfar mine and to assess the contribution of the deep salinity source to the high salinities observed in the mine. The groundwater of the shallow aquifer shows almost constant Br−/Cl− and Na+/Cl− ratios, independent of the chloride content. The constant ratios of these conservative elements indicate a single autochthonous origin of Cl−, Br− and Na+, and groundwater salinity is diluted by recharge water containing low concentrations of these elements. Regarding the mine groundwater, the high Li+/Cl− ratio and Br−/Cl− ratios in the range measured on the leachates of the rocks extracted from the mine indicate that the pore water is the reservoir for dissolved chloride and the salinity of the mine’s groundwater results from a mixture between these pore waters and fresh meteoric water that seeps in from the surface and recharges the entire aquifer. This porewater would be a remnant of the hydrothermal fluids that formed the sulfide deposit.

Area-based management tools to protect unique hydrothermal vents from harmful effects from deep-sea mining: A review of ongoing developments

The deep seabed in areas beyond national jurisdiction, or what is referred to as “the Area,” is the common heritage of humankind, safeguarded by mandating the International Seabed Authority (ISA) to protect the marine environment and to regulate all mining-related activities on the seabed in areas beyond national jurisdiction. So far, the ISA has 7 contracts for polymetallic sulfide (PMS) exploration. PMS deposits are located at and near deep-sea hydrothermal vents, one of the most remarkable ecosystems on Earth. Where hot and mineral rich vent fluids escape from the earth's crusts, minerals precipitate and are deposited, and unique biomass rich microbial and animal communities are thriving. Several intergovernmental organizations suggest that active vents classify as areas in need of conservation. The ISA is currently developing regional environmental plans for PMS and has set some first steps to protect active vents from mining impacts. We review the current regulatory and policy framework for deep-sea spatial management, and set it into the environmental context. We conclude that all current management measures of the ISA would not be suited to protect the marine environment from harmful mining impact. We recognize that ISA's area-based management tools are under development, and suggest that improvements can be achieved by studying and recognizing the ecological attributes of ecosystems and their connectivity, as well as governance connectivity, taking into account area-based management tools of different users in the same area.

Benthic biology in the Polish exploration contract area of the Mid-Atlantic Ridge: The knowns and the unknowns. A review

In February 2018, the Government of Poland and the International Seabed Authority signed a 15-year contract for exploration of polymetallic sulfide deposits on a section of the Mid-Atlantic Ridge extending between the Hayes, Atlantic and Kane transform faults (32°45.378’ N, 39°57.760’ W to 26°14.411’ N, 44°18.008’ W). The contractor is obliged to collect data on the contract area environment and its ecosystem components. In this context, it is important that the contractor establishes a sound starting point which further baseline investigations can be referred to. Such a starting point involves assessment of currently held information and, most importantly, knowledge gaps on the ecosystem components in the area of exploration (and of potential future exploitation). Of major importance here is the knowledge on benthic communities, as it is the benthos that will be most affected by any human intervention in the area of interest. Based on available published evidence, we have reviewed the present state of knowledge on benthic communities in the Polish exploration contract area (PECA). In the process, we have identified important knowledge gaps that will need to be addressed during exploration surveys. These include, but are not limited to, the distribution and structure of benthic communities throughout the contract area, the spatial and temporal variability of those communities, possible differences between communities inhabiting active and inactive vent fields, connectivity issues and the recovery potential. Special consideration should be given to Lost City, a geologically and ecologically unique hydrothermal field which has been a focus of international research and an important conservation target.

Numerical Simulation Study on the Relationships between Mineralized Structures and Induced Polarization Properties of Seafloor Polymetallic Sulfide Rocks

The induced polarization (IP) method plays an important role in the detection of seafloor polymetallic sulfide deposits. Numerical simulations based on the Poisson–Nernst–Planck equation and the Maxwell equation were performed. The effects of mineralized structures on the IP and electrical conductivity properties of seafloor sulfide-bearing rocks were investigated. The results show that total chargeability increases linearly as the volume content of disseminated metal sulfides increases when the volume content is below 20%. However, total chargeability increases nonlinearly with increasing volume content in vein and massive metal sulfides when the volume content is below 30%. The electrical resistivity of disseminated metal sulfides mainly depends on the conductivity of pore water. The electrical resistivity of vein and massive sulfides mainly depends on the volume content and the length of sulfides. Increase in the aspect ratio (0.36 to 0.93) of seafloor massive sulfides causes relaxation time constants and total chargeability to decrease. Relaxation time constants and total chargeability also decrease with increase in the tortuosity of seafloor vein sulfides from 1.0 to 1.38. This study is of great value for the electrical survey of seafloor polymetallic sulfide deposits.

Mineralogy of the Imalia Au-Sn-bearing polymetallic sulfide deposit, Mahakoshal belt, Central India

The Au-Sn-bearing, polymetallic sulfide deposit at Imalia in the western part of Mahakoshal belt, Central India is hosted by recrystallized dolostone and subsidiary phyllitic dolostone. These host rocks are transected by shallow level intrusion of quartz porphyry dykes. There are two major NS trending ore zones (∼1.5 km cumulative length) and a subsidiary-one, confined to fractures and shears in the dolostones or along its contact with the intrusive dykes. Polyphase mineralization include: irregularly disseminated pyrite crystals of diagenetic/metamorphic origin, patchy to stringery Pb-Zn sulfide ores showing pervasive metamorphic fabric, dominant massive vein type pyrite-arsenopyrite ores with significant amounts of invisible gold and tin. Other ore minerals include cassiterite, molybdenite, wolframite and roquesite in a magnetite-rich oxidic halo, and electrum, enargite/luzonite, wittichenite, ourayite, eclarite, aikinite and idaite in the sulfidic veins. Some tentatively identified ore minerals in these veins include calaverite, proustite, famatinite, sakuraiite, and tenorite. Pyrite contains structurally located invisible gold as high as 17.6 ppm whereas arsenopyrite contains a maximum of 20–24 ppm Au. Pyrite also contains unusually high Sn (upto 2673 ppm). The mineralogical assemblage of rare phases and their paragenesis in the Imalia vein type ores reflect the high sulfur (log fS2 = −9 to −13 bar) and oxygen (logfO2 = −32 bar) fugacities at a temperature range of 350 °C to 250 °C (according to thermometric calculations) during their emplacement.

Non-Vent Megafaunal Communities on the Endeavour and Middle Valley Segments of the Juan de Fuca Ridge, Northeast Pacific Ocean

There has been increasing interest in mining polymetallic sulfide deposits at deep-sea inactive hydrothermal vents, leading to the development of regulations to minimize risk to the marine environment. While an extensive body of literature exists on the ecological communities at active vents, fauna at inactive hydrothermal vents and the vent periphery are poorly described and their vulnerability to disturbance is unknown. We examined patterns in abundance of non-vent epibenthic megafauna on two segments of the Juan de Fuca Ridge, Northeast Pacific Ocean. Video footage was collected by the remotely operated vehicle ROPOS during four dives at the Endeavour Segment and two dives at Middle Valley in August 2016. At the Endeavour Segment, the substrate is characterized predominantly by basalt and edifices of hydrothermal sulfide that range in hydrothermal activity from inactive to vigorous, high-temperature venting. In contrast, Middle Valley is heavily sedimented and most hydrothermal activity is low-temperature diffuse flow. While inactive substrates at both sites harboured slow-growing sessile fauna, the dominant members of the community differed between sites. At Endeavour, the most abundant morphotaxa included rossellid vase sponges, alcyonacean corals, and crinoids. Estimated richness and total abundance of morphotaxa was higher on hard substrates than sedimented substrates and highest on inactive chimneys. At Middle Valley, the most abundant morphotaxa included antipatharian corals, anemones, and ascidians. Species richness was higher on inactive chimneys and mixed substrates than sediment. The abundance of some megafauna varied with proximity to active vents. At Endeavour, deep-water corals were nearly absent within 25 m of active chimneys and very few occurred between 26 and 50 m from active chimneys. Rossellid vase sponges were in low abundance within 25 m of active chimneys but were more abundant than corals at 26-50 m from active chimneys. This project contributes baseline data on megafaunal assemblages on inactive hydrothermal vents and can provide the basis for more focused research on the structure and function of inactive vent ecosystems.

Effect of peracetic acid as a depressant on the flotation separation of chalcopyrite from arsenopyrite

• Separation of arsenopyrite from chalcopyrite hindered by similar floatabilities. • Depression of arsenopyrite flotation required for better separation. • Effect of peracetic acid as a depressant of arsenopyrite was investigated in this study. • Found to greatly aid in flotation separation under neutral pH conditions. Arsenopyrite is an arsenic-bearing mineral that frequently occurs with chalcopyrite in polymetallic sulphide deposits. Their separation via existing methods and reagents involved in the flotation process, however, remains sub-par due to difficulties in the effective depression of arsenopyrite. In this study, the eco-friendly organic oxidant of peracetic acid (PAA, CH 3 C( O)OOH) was used for the first time ever to effectively depress arsenopyrite under conditions of neutral pH. Flotation experiments, adsorption tests, zeta potential analysis, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) were performed to investigate the depression mechanism of PAA on arsenopyrite. Single mineral flotation results showed PAA to have a massive depressive effect on arsenopyrite, reducing its froth recovery from 90% to 3% but only marginally affecting the froth recovery of chalcopyrite. Mixed minerals and bench-scale flotation tests further verified that PAA was an efficient arsenopyrite depressant. Adsorption test results, meanwhile, indicated that PAA could significantly reduce the adsorption of xanthate on the surface of arsenopyrite, but not on that of chalcopyrite. Zeta potential measurements, on the other hand, suggested a strong interaction between the surface of arsenopyrite and PAA compared with chalcopyrite, which induced a positive shift of zeta potential on the arsenopyrite surface. XPS analysis demonstrated that PAA only slightly oxidizes the surface of chalcopyrite, and a very small amount of iron oxide, sulfur oxide and copper oxide were generated, indicating that the surface was still hydrophobic. On the contrary, PAA could strongly oxidize the surface of arsenopyrite and generate a large number of oxygen-containing species, such as As(III)–O, As(V) − O, Fe(III) − O, Fe(III)–SO, SO 3 2− , and SO 4 2− . This was supported by measuring the contents of these oxides of iron, sulphur, and arsenic on the surface of arsenopyrite, which were found to increase from 47.13% to 88.56%, 14.95% to 45.49%, and 45.94% to 81.57%, respectively. Finally, hydrophilic oxide films containing AsO 2 − , AsO 3 − , SO 3 2− , Fe(OH) 3 , FeAsO 4 , and Fe 2 (SO 4 ) 3 were formed on the arsenopyrite surface, which further contributed to its depression.

DNA Barcoding of Scavenging Amphipod Communities at Active and Inactive Hydrothermal Vents in the Indian Ocean

Hydrothermal vent areas have drawn increasing interest since they were discovered in 1977. Because of chemoautotrophic bacteria, they possess high abundances of vent endemic species as well as many non-vent species around the fields. During the survey conducted by the Bundesanstalt für Geowissenschaften und Rohstoffe (Federal Institute for Geosciences and Natural Resources, BGR) to identify inactive polymetallic sulfide deposits along Central and Southeast Indian Ridges, the INDEX project studied the scavenging amphipod community at three newly discovered hydrothermal fields. A sample consisting of 463 representatives of Amphipoda (Malacostraca: Crustacea) was collected by means of baited traps in active and inactive vents of three different sites and subsequently studied by both morphological and genetic methods. Molecular methods included the analysis of two mitochondrial (cytochrome c oxidase subunit I [COI] and 16S rRNA) and one nuclear (18S rRNA) genes. By six delimitation methods, 22 molecular operational taxonomic units (MOTUs) belonging to 12 genera and 10 families were defined. The existence of potential species complexes was noted for the representatives of the genus Paralicella. The inactive site, where 19 species were found, showed higher species richness than did the active one, where only 10 taxa were recorded. Seven genera, Ambasiopsis, Cleonardo, Eurythenes, Parandania, Pseudonesimus, Tectovalopsis, and Valettiopsis, were observed only at inactive sites, whereas Haptocallisoma, was collected exclusively at active ones. The species Abyssorchomene distinctus (Birstein and Vinogradov, 1960), Hirondellea brevicaudata Chevreux, 1910, and Hirondellea guyoti Barnard and Ingram, 1990, have been previously reported from vent sites in the Atlantic or Pacific oceans. The present study provides the first report of Eurythenes magellanicus (H. Milne Edwards, 1848) and five other already described species in the Indian Ocean. The addition of 356 sequences strongly increases the number of amphipod barcodes in reference databases and provides for the first time COI barcodes for Cleonardo neuvillei Chevreux, 1908, Haptocallisoma abyssi (Oldevig, 1959), Hirondellea guyoti, Tectovalopsis fusilus Barnard and Ingram, 1990, and the genera Haptocallisoma, Pseudonesimus, and Valettiopsis.

Composition of volatiles of sulfide deposits and carbonate structures in submarine hydrothermal fields of the Mid-Atlantic Ridge

In this study, the composition of fluid inclusions in minerals from polymetallic sulfide deposits Ashadze-1, Semenov-2, Krasnov, Rainbow and from the Lost City carbonate structures of hydrothermal fields in the Atlantic Ocean was determined using pyrolysis-free gas chromatography–mass spectrometry.It was found out that sulfides and anhydrite from the hydrothermal ore crystallized in reducing conditions with the active participation of hydrocarbons, including high-molecular, sulfonated, nitrogenated and halogenated compounds as well as water and carbon dioxide.On the other hand, carbonate structures formed in considerably more oxidizing conditions, for which the main components of volatiles were СО2 and Н2О. The amount of detected hydrocarbons, including sulfonated, nitrogenated and halogenated compounds is significantly smaller compared to sulfides of ore vent structures.

The megalopal stage of the hydrothermal vent crab Austinograea rodriguezensis Tsuchida amp; Hashimoto, 2002 (Decapoda: Bythograeidae): a morphological description based on CLSM images.

The Bythograeidae is unique amongst brachyuran crab taxa as it is the only family where all 6 genera and 16 species are endemic to hydrothermal vents. During the research conducted by German Federal Institute for Geosciences and Natural Resources to identify inactive polymetallic sulphide deposits along Central and Southeast Indian Ridges, the INDEX project collected from hydrothermal vent fields 6 Bythograeidae megalopae. Entire specimens and dissected appendages were stained, mounted on slides and examined using Light Microscopy and Confocal Laser Scanning Microscopy. Additional molecular analysis using mtCOI confirmed the identification of the specimens as Austinograea rodriguezensis Tsuchida Hashimoto, 2002. The megalopal stage of A. rodriguezensis shows similarities and distinctions between the characters of two other bythograeid megalopae, Bythograea thermydron Williams, 1980, and B. microps Saint Laurent, 1984. Unlike other brachyuran megalopae, B. thermydron and A. rodriguezensis lack long serrate setae and stout serrate spines on the dactylus of the fifth pereiopod. In both species no coxal spines on the pereiopods were observed. The elliptical carapace of B. thermydron is broader than long vs longitudinally rectangular in A. rodriguezensis. This carapace shape resembles B. microps more than B. thermydron, however, the dorsal surface of B. microps carapace is densely covered in short setae vs only covered with short setae on the anterior 1/4 and the posterior 1/6 length of carapace in A. rodriguezensis. Furthermore, the amount of plumose natatory setae on the pleopods in B. microps is in total larger and more variable, than in A. rodriguezensis. Bythograeid megalopae seem quite generalized and miss specific features that reveal them distinctively as endemic vent crab. A distinction from other species is possible by observing the unique combinations of certain characters. This is the first megalopal stage description of Austinograea and the fourth within the Bythograeidae.

Image and Point Data Fusion for Enhanced Discrimination of Ore and Waste in Mining

Sensor technologies provide relevant information on the key geological attributes in mining. The integration of data from multiple sources is advantageous in making use of the synergy among the outputs for the enhanced characterisation of materials. Sensors produce various types of data. Thus, the fusion of these data requires innovative data-driven strategies. In the present study, the fusion of image and point data is proposed, aiming for the enhanced classification of ore and waste materials in a polymetallic sulphide deposit at 3%, 5% and 7% cut-off grades. The image data were acquired in the visible-near infrared (VNIR) and short-wave infrared (SWIR) regions of the electromagnetic spectrum. The point data cover the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral regions. A multi-step methodological approach was developed for the fusion of the image and point data at multiple levels using the supervised and unsupervised classification techniques. Several possible combinations of the data blocks were evaluated to select the optimal combinations in an optimised way. The obtained results indicate that the individual image and point techniques resulted in a successful classification of ore and waste materials. However, the classification performance greatly improved with the fusion of image and point data, where the K-means and support vector classification (SVC) models provided acceptable results. The proposed approach enables a significant reduction in data volume while maintaining the relevant information in the spectra. This is principally beneficial for the integration of data from high-throughput and large data volume sources. Thus, the effectiveness and practicality of the approach can permit the enhanced separation of ore and waste materials in operational mines.

Application of Knowledge-Driven Methods for Mineral Prospectivity Mapping of Polymetallic Sulfide Deposits in the Southwest Indian Ridge between 46° and 52°E

As a product of hydrothermal activity, seafloor polymetallic sulfide deposit has become the focus of marine mineral exploration due to its great prospects for mineralization potential. The mineral prospectivity mapping is a multiple process that involves weighting and integrating evidential layers to further explore the potential target areas, which can be categorized into data-driven and knowledge-driven methods. This paper describes the application of fuzzy logic and fuzzy analytic hierarchy process (AHP) models to process the data of the Southwest Indian Ocean Mid-Ridge seafloor sulfide deposit and delineate prospect areas. Nine spatial evidential layers representing the controlling factors for the formation and occurrence of polymetallic sulfide deposit were extracted to establish a prospecting prediction model. Fuzzy logic and fuzzy AHP models combine expert experience and fuzzy sets to assign weights to each layer and integrate the evidence layers to generate prospectivity map. Based on prediction-area (P-A) model, the optimal gamma operator (γ) values were determined to be 0.95 and 0.90 for fuzzy logic and fuzzy AHP to synthesize the evidence layers. The concentration-area (C-A) fractal method was used to classify different levels of metallogenic probability by determining corresponding thresholds. Finally, Receiver Operating Characteristic (ROC) curves were applied to measure the performance of the two prospectivity models. The results show that the areas under the ROC curve of the fuzzy logic and the fuzzy AHP model are 0.813 and 0.887, respectively, indicating that prediction based on knowledge-driven methods can effectively predict the metallogenic favorable area in the study area, opening the door for future exploration of seafloor polymetallic sulfide deposits.

Research is needed to inform environmental management of hydrothermally inactive and extinct polymetallic sulfide (PMS) deposits

Polymetallic sulfide (PMS) deposits produced at hydrothermal vents in the deep sea are of potential interest to miners. Hydrothermally active sulfide ecosystems are valued for the extraordinary chemosynthetic communities that they support. Many countries, including Canada, Portugal, and the United States, protect vent ecosystems in their Exclusive Economic Zones. When hydrothermal activity ceases temporarily (dormancy) or permanently (extinction), the habitat and associated ecosystem change dramatically. Until recently, so-called “inactive sulfide” habitats, either dormant or extinct, received little attention from biologists. However, the need for environmental management of deep-sea mining places new imperatives for building scientific understanding of the structure and function of inactive PMS deposits. This paper calls for actions of the scientific community and the emergent seabed mining industry to i) undertake fundamental ecological descriptions and study of ecosystem functions and services associated with hydrothermally inactive PMS deposits, ii) evaluate potential environmental risks to ecosystems of inactive PMS deposits through research, and iii) identify environmental management needs that may enable mining of inactive PMS deposits. Mining of some extinct PMS deposits may have reduced environmental risk compared to other seabed mining activities, but this must be validated through scientific research on a case-by-case basis.

Fusion of Mid-Wave Infrared and Long-Wave Infrared Reflectance Spectra for Quantitative Analysis of Minerals.

Accurate quantitative mineralogical data has significant implications in mining operations. However, quantitative analysis of minerals is challenging for most of the sensor outputs. Thus, it requires advances in data analytics. In this work, data fusion approaches for integrating datasets pertaining to the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral regions are proposed, aiming to facilitate more accurate prediction of SiO2, Al2O3, and Fe2O3 concentrations in a polymetallic sulphide deposit. Two approaches of low-level data fusion were applied to these datasets. In the first approach, the pre-processed blocks of MWIR and LWIR data were concatenated to form a fused data block. In the second approach, a prior variable selection was performed to extract the most important features from the MWIR and LWIR datasets. The extracted informative features were subsequently concatenated to form a new fused data block. Next, prediction models that link the mineralogical concentrations with the infrared reflectance spectra were developed using partial-least squares regression (PLSR), principal component regression (PCR) and support vector regression (SVR) analytical techniques. These models were applied to the fused data blocks as well as the individual (MWIR and LWIR) data blocks. The obtained results indicate that SiO2, Al2O3, and Fe2O3 mineral concentrations can be successfully predicted using both MWIR and LWIR spectra individually, but the prediction performance greatly improved with data fusion; where the PLSR, PCR, and SVR models provided good and acceptable results. The proposed approach could be extended for online analysis of mineral concentrations in different deposit types. Thus, it would be highly beneficial in mining operations, where indications of mineralogical concentrations can have significant financial implications.

Data Fusion for the Prediction of Elemental Concentrations in Polymetallic Sulphide Ore Using Mid-Wave Infrared and Long-Wave Infrared Reflectance Data

The increasing availability of complex multivariate data yielded by sensor technologies permits qualitative and quantitative data analysis for material characterization. Multivariate data are hard to understand by visual inspection and intuition. Thus, data-driven models are required to derive study-specific insights from large datasets. In the present study, a partial least squares regression (PLSR) model was used for the prediction of elemental concentrations using the mineralogical techniques mid-wave infrared (MWIR) and long-wave infrared (LWIR) combined with data fusion approaches. In achieving the study objectives, the usability of the individual MWIR and LWIR datasets for the prediction of the concentration of elements in a polymetallic sulphide deposit was assessed, and the results were compared with the outputs of low- and mid-level data fusion methods. Prior to low-level data fusion implementation, data filtering techniques were applied to the MWIR and LWIR datasets. The pre-processed data were concatenated and a PLSR model was developed using the fused data. The mid-level data fusion was implemented by extracting features using principal component analysis (PCA) scores. As the models were applied to the MWIR, LWIR, and fused datasets, an improved prediction was achieved using the low-level data fusion approach. Overall, the acquired results indicate that the MWIR data can be used to reliably predict a combined Pb–Zn concentration, whereas LWIR data has a good correlation with the Fe concentration. The proposed approach could be extended for generating indicative element concentrations in polymetallic sulphide deposits in real-time using infrared reflectance data. Thus, it is beneficial in providing elemental concentration insights in mining operations.

The impact of hydrothermal mineral replacement reactions on the formation and alteration of carbonate-hosted polymetallic sulfide deposits: A case study of the Artemis prospect, Queensland, Australia

Hydrothermal sulfidation of carbonate rocks and the reverse replacement of sulfides by carbonates are important processes responsible for the formation and subsequent alteration of ore deposits. These processes have been recognized in the case study of the Artemis Zn-Cu-Au prospect, which is located in the Cloncurry district within the Eastern Succession of the Mount Isa Inlier, NW Queensland, Australia. The high-grade polymetallic mineralization displays a complex association of massive sulfides and carbonates hosted in a vertical marble lens adjacent to garnet-bearing schist, staurolite-muscovite schist, and quartzo-feldspathic psammite. Petrographic analyses of drill core specimen by optical and electron microscopy, micro-X-ray florescence elemental maps, electron probe microanalyses, cathodoluminescence, and bulk geochemistry suggested three major stages of mineralization: (i) pre-ore stage marble (calcite-0); (ii) ore stage involving sulfidation of the marble and precipitation of calcite-1 and spherical sulfide inclusions in the first episode and the formation of calcite-2 and massive sulfide in the second episode; and (iii) post-ore stage involving replacement of sulfides by calcite-3 and garnet.Mineral replacement reactions are dominant processes in rocks of ore stage and post-ore stage. The ore stage involved the dissolution of coarse and pristine calcite-0 (Ca0.95Mn0.3Fe0.2CO3) and the precipitation of sulfides and calcite-1 (Ca0.96Mn0.3Fe0.1CO3) and calcite-2 (Ca0.96Mn0.3Fe0.1CO3). The sulfide assemblage consists of pyrrhotite, sphalerite, chalcopyrite, galena, arsenopyrite, cobaltite, costibite, Bi, cubanite ± Ag-sulfides and Au, in decreasing order of abundance. In episode 1, calcite-1 contains spherical sulfide inclusions while in episode 2, calcite-2 envelopes calcite-1. The replacement of Co-rich arsenopyrite (Fe0.75Co0.26As1.13S0.83) by relatively Co-poor arsenopyrite (Fe0.86Co0.15As0.99S0.99) via a coupled dissolution-precipitation reaction occurred in episode 2. Based on arsenopyrite geothermometry, the temperatures for the first and second episode are 650 ± 50 and 450 ± 70 °C, respectively. Micro-XRF elemental maps of the garnet-bearing schist, adjacent to the sulfidized marble, revealed the sulfidation front where pre-ore garnet and amphibole were replaced by pyrrhotite, chalcopyrite, Au, biotite, and muscovite. In the post-ore stage, calcite-2 was partially replaced by siderite and calcite-3 (Ca0.94Mn0.4Fe0.2Mg0.1CO3), which shows sectoral and oscillatory zoning. Galena was replaced by calcite-3 as documented by embayed lobate grain boundaries between these minerals, and pyrrhotite Fe(1-x)S, (x = 0.091–0.119) was pervasively replaced by garnet (Mn1.2Fe1.2Ca0.6)Al2Si3O12. The microscale investigations of the mineralization processes in the Artemis orebody document the impact of hydrothermal mineral replacement reactions on metal sequestration. Mineral replacement reactions facilitate the formation of ore-deposits and subsequent alteration processes, which may lead to the loss of economic value of the deposit.