Submarine Mine Research Articles

Physical model of solid minerals transportation from Arctic shelf seabed using soil-ice bodies

The projected increase in demand for some metals required for various industries, including transition to clean energy sources, shall force people to look for new deposits and the development of such deposits shall become progressively complicated. Arctic shelf is one of the promising mineral sources, but its areas are hardly explored and developed. The reasons include the absence of mining technologies that could ensure the efficient development of subsea solid mineral deposits. This study proposes a mining technology that enables transportation of minerals from the seabed to the water surface using the ice that covers the valuable mineral particles suspended by means of loosening and continuous supply of cooling agent to the submarine mining face. The technology implies formation of soil-ice bodies comprising an ice component with pores and mineral particles. The detailed study of the proposed technology and its application conditions included the development of a theoretical model of soil-ice bodies emersion from the seabed to the water surface with account of ice component melting.

Biogeochemical impact of historical submarine mine tailings on benthic ecosystems in the Repparfjord (Northern Norway)

Historical copper mine tailings deposited in the Repparfjord, Northern Norway, provided new insight into the biogeochemical impact of submarine tailings disposals on high-latitude coastal ecosystems. The submarine tailings disposal in the Repparfjord represents a product of mining activities between 1972 and 1979. Their environmental impact has been extensively studied during the last decade, but geochemistry of the sediment pore water, which is crucial to assess and monitor the in-situ metal leaching and bioavailability, has never been analysed. The actual impact on the benthic fauna remains poorly known. Therefore, this study couples the pore water chemistry and the foraminiferal analysis obtained from selected sediment cores (gravity core, multicore, box cores) to examine metal stability and the past and current status of the foraminifera community. We measured down-core sulfate and trace metal concentrations and Eh-Ph and applied the Shannon index, the AZTI's Marine Biotic Index (F-AMBI) index and the foraminiferal abnormality index. This study confirms the ongoing leaching of Cu from the underlying mine tailings and release across the sediment-water interface. Leaching of Ni, Zn and Pb have been attributed to weathering of natural bedrock lithologies. The original benthic foraminiferal community disappeared almost entirely during the disposal period, and now it is dominated by stress-tolerant and opportunistic species like Bulimina marginata and Spiroplectammina biformis. Anyhow, against previous assumptions, the community composition changed, while the overall diversity and abnormalities (FAI) shell formation is unaffected by elevated Cu concentrations.

Fractal Evolution Characteristics of Isolation Layers in a Submarine Gold Mine: A Case Study

The establishment of an isolation layer in submarine mining has been a persistent challenge. In the context of this research, we conducted a similarity simulation test to preliminarily assess the interaction between the thickness and extent of the isolation layer. Subsequently, we introduce an innovative approach that integrates fractal theory and the Bonded Block Model (BBM) to simulate undersea isolation layer mining. The validation of this method relies on on-site borehole scanning and displacement monitoring, which depict the intricate fractal evolution of fractures and predict the optimal thickness of the isolation layer. Our findings affirm the robustness and validity of this method. Evaluation of the fractal dimensions of fractures reveals that a critical threshold of 1.7 is essential to prevent structural failure of the isolation layer, while a limit of 1.5 is necessary to avoid significant water ingress. Remarkably, the correlation dimension of the settlement time series closely aligns with the fractal dimension of the fractures, underscoring the feasibility of ensuring the safety of isolation layer mining through real-time settlement monitoring.

Impacts of climate change on metal leaching and partitioning for submarine mine tailings disposal.

At present, there are no standardised tests to assess metal leaching during submarine tailings discharge. In this study the influence of variables known to affect metal mobility and availability (dissolved organic carbon (DOC), pH, salinity, temperature, aerated/anoxic conditions) along with variables affected by the discharge conditions (flocculant concentration, suspension) were studied in bench-scale experiments. The leaching tests were developed based on the case of a copper mine by Repparfjorden, northern Norway, which is planned to re-open in 2022. The experiments, which had three week duration, revealed low (<6%) leaching of metals. Multivariate analysis showed that all variables, apart from DOC, highly influenced leaching and partitioning of at least one metal (Ba, Cr, Cu, and/or Mn). The high quantity of the planned annual discharge of mine tailings to the fjord (1-2milliontonnes) warranted estimation of the leached quantity of metals. Multivariate models, using present-day conditions in the fjord, estimated leaching of up to 124kg Ba, 154kg Cu and 2400kg Mn per year during discharge of tailings. Future changes in the fjord conditions caused by climate change (decreased pH, increased temperature) was predicted by the multivariate models to increase the leaching up to 55%, by the year 2065. The bench-scale experiments demonstrated the importance of including relevant variables (such as pH, salinity, and temperature) for metal leaching and -partitioning in leaching tests. The results showed that metal leaching during discharge is expected and will increase in the future due to the changed conditions caused by the foreseen climate change, and thereby underline the importance of monitoring metal concentrations in water during operations to determine the fate of metals in the fjord.

A Case Study on Deformation Failure Characteristics of Overlying Strata and Critical Mining Upper Limit in Submarine Mining

Unlike land mining, the safety of seabed mining is seriously threatened by an overlying water body. In order to ensure the safety of subsea mining projects, it is of great importance to understand the failure characteristics and influencing factors of overlying strata deformation. Focusing on the Sanshandao Gold Mine, a typical submarine deposit in China, geomechanical model testing and numerical simulations were carried out. The results show that in the mining of a steeply dipping metal ore body, subsidence deformation mainly occurs on the hanging wall; the subsidence center is located on the surface of the hanging wall, and the uplift center is located on the upper surface of the ore body. The critical mining upper limit, which represents the minimum thickness of the reserved isolation pillar between the overlying seawater and the goaf, was determined to be 50 m in the Xinli mine; fault slip would occur if this critical value was exceeded. The dip angle and thickness of the ore body were negatively correlated with the vertical surface deformation. As the dip angle and thickness increased, the critical upper mining limit increased. When the fault was located in the footwall, the critical upper mining limit increased as the distance between the fault and the ore body increased, and the failure mode of the goaf was fault slip. When the fault was located in the hanging wall, the final failure mode of the goaf changed to a combined failure mode of overlying rock collapse as well as fault slip. These research results provide a theoretical basis for the selection of the reserved pillar height in the Xinli mining area, as well as a reference for safe mining practices under similar geological conditions.

Submarine mineral resources: A potential solution to political conflicts and global warming

Global warming is the biggest problem that humanity is facing. Most climate scientists agree on how human intervention has affected the atmospheric change in the past two centuries, leading to a rise in global temperature by 1 °C. This is mainly due to the high production of CO2 by the energy sector, which is why it is necessary to promote accelerated growth in the renewable energy market. However, there is a shortage of critical materials in the Earth's crust, wherein China (the largest producer) has a monopolistic position in the rare earth market. This situation restricts the growth of the cleaner energies market and, in turn, generates significant political conflicts between the world's great powers. The vast mineral wealth that is available in the seabed might provide several critical metals, highlighting a large concentration of rare earth, which makes deep-sea mining a great alternative to satisfy the demand for these resources. However, the environmental damage in the marine ecosystem due to large submarine mining is still unknown, leaving us a critical question: Is large submarine mining a viable solution to the problems of market and environmental issues?

The Application of Destress Mining Technology in Deep High Stress Stope of a Submarine Mine

Feng, P.; Yang, X.; Guo, Q.; Wang, H., and Wan, C., 2020. The application of destress mining technology in deep high stress stope of a submarine mine. In: Liu, X. and Zhao, L. (eds.), Today's Modern Coastal Society: Technical and Sociological Aspects of Coastal Research. Journal of Coastal Research, Special Issue No. 111, pp. 34–38. Coconut Creek (Florida), ISSN 0749-0208.The deep ore rock of a submarine gold mine had strong rock burst tendency. The difference between its maximum principal stress and minimum principal stress was large, and the surrounding rock deformation and failure were serious. A combined regional and local destress mining technology for the high stress submarine environment was proposed and applied to deep stope in coastal deposit. Regionally, the stope structure and stope sequence were optimized to reconstruct the favorable ground stress environment. Locally, the destress engineering was arranged rationally to interfere with the transmission path of the maximum principal stress. Meanwhile, the pillar was supported by flexible cooperative support with shotcrete and anchor net. The (stress and strain) in situ monitoring indicated that the stress in submarine stope appeared three-dimensional balanced distribution after destress, and the surrounding rock deformation of submarine roadway tended to be stable, achieving the expected destress mining effect in coastal high stress deposit.

A la cumbre por un valle. Adolphe Desoignie, un ingeniero de minas pionero en la Asturias protoindustrial

Los años centrales del siglo XIX son uno de los vacíos más llamativos de la historiografía sobre la industrialización asturiana, puesto que constituyen el punto de despegue del proceso. En estas páginas se glosan las aportaciones técnicas de uno de los primeros ingenieros de minas que trabajaron en la región, el belga Adolphe Desoignie, que contribuyó a la transferencia de tecnología avanzada entre Centroeuropa y Asturias en esta fase liminar y decisiva. En 2019 se cumplieron 180 años de la puesta en marcha la primera mina submarina documentada en Europa. Pese a ello, como otros coetáneos, no ha tenido la repercusión que merece en la literatura científica.

High-resolution numerical modelling of a marine mine tailings discharge in Western Norway

Waste from mining operations includes mine tailings, a slurry of fine-grained mineral particles and processing chemicals that remains after the desired compounds have been extracted from the ore. In some cases, the method of disposal is to place tailings into the marine environment; this is known as Submarine Tailings Placement (STP). To understanding the environmental impact of releasing large amounts of mine tailings into the marine system, multiple processes must be well characterised, including those relating to the transport and fate of the disposed material.We applied a set of high-resolution models for wind, hydrodynamics, and sediment transport to simulate a submarine mine tailings discharge in a Norwegian fjord. The transport model includes processes to account for the effect of flocculation on mine tailings transport and fate. We calculated the mean tailings sedimentation rate in the fjord, which is closely related to the environmental footprint of the STP. Comparisons with measurements of winds, currents, turbidity, and sedimentation rates were made to evaluate the model, and we found overall reasonable agreement. We investigated discharge scenarios during 2013 and identified a strong wind event around November 17, which caused increased particle dispersal. The increased mixing caused by the strong winds were seen in elevated turbidity measurements, as well as increased modelled suspended sediment concentration.

Distribution, deposition and impact of submarine mine tailings disposal on the fjord bottom in Frænfjorden, western Norway

Distribution, deposition and impact of submarine mine tailings disposal on the fjord bottom in Frænfjorden, western Norway

Distribution, deposition and impact of submarine mine tailings disposal on the fjord bottom in Frænfjorden, western Norway

Distribution, deposition and impact of submarine mine tailings disposal on the fjord bottom in Frænfjorden, western Norway

Stability of Cu-Sulfides in Submarine Tailing Disposals: A Case Study from Repparfjorden, Northern Norway

Mine tailings that were produced during the exploitation of the Ulveryggen siliciclastic sediment-hosted Cu deposit in northern Norway were disposed into the inner part of Repparfjorden from 1972 to 1978/1979. This study focuses on the mineralogy and geochemistry of the submarine mine tailings and underlying natural marine sediments from the inner part of Repparfjorden, as well as on the primary Ulveryggen ore. The ore mineralization from the neighboring Nussir carbonate sediment-hosted Cu deposit was studied too, due to the forthcoming mining of both deposits. Bornite and chalcopyrite are the major Cu-sulfides, and are characterized by low concentrations of potentially toxic elements including Cd, Hg, and As. The tailing material occupies the uppermost 9 cm of Repparfjorden sediments. It is characterized by predomination of a silty component with elevated Cu (up to 747.7 ppm), Ni (up to 87 ppm), and Cr (up to 417 ppm) concentrations. The high Cu concentration is related to the deposition of mine tailings. In contrast, Ni and Cr concentrations are close to those in naturally occurring stream sediments from the feeding river, Repparfjordelva, reflecting the compatibility of these elements with hosting mafic volcanics, which are widely spread in the Repparfjord Tectonic Window. Copper in the uppermost part of the sediments is bound to the acid-soluble fraction while Ni and Cr are bound to the residual fraction. Artificial placement of large masses of fine-grained material, i.e., smothering, resulted in a diminished biological activity and/or physical distortion of mostly benthic fauna, which was reflected in total organic carbon (TOC) values as low as 0.15% in the uppermost strata. Sulfide minerals are found both in natural marine sediments and in the mine tailings. They are generally well-preserved with an exception for chalcopyrite from the uppermost part of the submarine tailing, which shows signs of incipient weathering. Thermodynamic modeling confirmed that redox potential and pH are important factors in the weathering of sulfides. Available ligands contribute to the Cu speciation. In near-neutral to slightly alkaline conditions a presence of carbonates can lead to the mobilization of Cu in form of CuCO3 complexes.

Experimental Platform Development of Similar Simulation and Mechanical Test for Undersea Metal Mining

With the depletion of shallow metal resources in the land, the development of seabed resources has become a new direction. In order to achieve safe and efficient exploitation of seabed metal mineral resources, a similar simulation test platform was established for seabed mining of metal minerals in this paper. Similar simulation materials and the best material ratios were selected to make simulated specimens. A series of mechanical pressurization devices and model sample were prototyped and submarine simulation mining test was conducted. During the simulation mining test, stress and strain changes and microscopic observations of crack evolution were monitored by the static strain test system. These indicators revealed the characteristics of ore-rock mechanical change in the development of submarine mental resources. By exploring the best safe thickness of seabed resource mining, it provides effective data reference for subsequent seabed resource development, so as to realize safe and efficient mining.

Optimal path planning based on A* algorithm for submarine mining vehicle

Deep sea mining, as a frontier area in China, urgently needs to make progress in automatic navigation technology. In order to improve the operation efficiency of the seabed mining machine on the soft seabed, the submarine mining vehicle which complete the mining work in a certain mining area need to enter the next mining area quickly and economically. As a classical algorithm, the majority of scholars consider that A * algorithm is the most practical path planning search algorithm. Considering the limitation of operation conditions, the three-dimensional diagram is transformed into two-dimensional diagram by interpolation method when the seabed terrain conditions allow, and then the obstacles can be marked in two-dimensional diagram. A* algorithm was applied into the path planning of mining truck. The simulation results of the paper show that path cost, turning time and turning mode should be considered in the process of avoiding obstacles.

Dissimilatory bioreduction of iron(III) oxides by Shewanella loihica under marine sediment conditions

Shewanella is a genus of marine bacteria capable of dissimilatory iron reduction (DIR). In the context of deep-sea mining activities or submarine mine tailings disposal, dissimilatory iron reducing bacteria may play an important role in biogeochemical reactions concerning iron oxides placed on the sea bed. In this study, batch experiments were performed to evaluate the capacity of Shewanella loihica PV-4 to bioreduce different iron oxides (ferrihydrite, magnetite, goethite and hematite) under conditions similar to those in anaerobic sea sediments. Results showed that bioreduction of structural Fe(III) via oxidation of labile organic matter occurred in all these iron oxides. Based on the aqueous Fe (II) released, derived Fe(II)/acetate ratios and bioreduction coefficients seem to be only up to about 4% of the theoretical ones, considering the ideal stoichiometry of the reaction. A loss of aqueous Fe (II) was caused by adsorption and mineral transformation processes. Scanning electron microscope images showed that Shewanella lohica was attached to the Fe(III)-oxide surfaces during bioreduction. Our findings suggest that DIR of Fe(III) oxides from mine waste placed in marine environments could result in adverse ecological impacts such as liberation of trace metals in the environment.

Application of Multivariate Statistical Analysis to Identify Water Sources in A Coastal Gold Mine, Shandong, China

Submarine mine water inrush has become a problem that must be urgently solved in coastal gold mining operations in Shandong, China. Research on water in subway systems introduced classifications for the types of mine groundwater and then established the functions used to identify each type of water sample. We analyzed 31 water samples from −375 m underground using multivariate statistical analysis methods. Cluster analysis combined with principle component analysis and factor analysis divided water samples into two types, with one type being near the F3 fault. Principal component analysis identified four principle components accounting for 91.79% of the total variation. These four principle components represented almost all the information about the water samples, which were then used as clustering variables. A Bayes model created by discriminant analysis demonstrated that water samples could also be divided into two types, which was consistent with the cluster analysis result. The type of water samples could be determined by placing Na+ and CHO3− concentrations of water samples into Bayes functions. The results demonstrated that F3, which is a regional fault and runs across the whole Xishan gold mine, may be the potential channel for water inrush, providing valuable information for predicting the possibility of water inrush and thus reducing the costs of the mining operation.

Environmental adaptive management: Application on submarine mine tailings disposal.

Marine tailings disposal from mineral production is expected to have an environmental impact. In this case study we use a discharge of limestone processing tailings to a Norwegian fjord to describe an adaptive management process. The aim of the paper is to describe the development of an environmental adaptive management system (EAMS), contrasted with management simply based on the quantity of the discharge. The main driver for developing a new management system for the submarine tailings deposits was a desire to establish a system based on what was perceived as important to all stakeholders, that is, environmental impact. Involvement of stakeholders is essential, and a resource group with members from fisheries, local interest organizations, scientists, independent experts, and managers from the mining company jointly defined common sets of acceptance criteria to evaluate impact. Introduction of an EAMS has resulted in a change in the company's view of the impact their activity has on the environment and in an increased willingness to initiate monitoring and research to reduce knowledge gaps and uncertainty and impact on the marine environment. Environmental adaptive management has facilitated the development of a more ecologically relevant, integrated, and focused submarine tailings deposits management. Integr Environ Assess Manag 2019;15:575-583. © 2019 SETAC.

The influence of Magnafloc10 on the acidic, alkaline, and electrodialytic desorption of metals from mine tailings

Repparfjorden in northern Norway has been partly designated for submarine mine tailings disposal when the adjacent Cu mine re-opens in 2019. In order to increase sedimentation, the flocculant, Magnafloc10 is planned to be added to the mine tailings prior to discharge into the fjord. This study investigated the feasibility of reducing the Cu concentrations (375 mg/kg) in the mine tailings by applying electrodialytic extraction, including potential optimisation by adding Magnafloc10. In the acidic electrodialytic treatment (pH < 2), Magnafloc10 increased the extraction of Cu from the mine tailings particles from 76 to 86%, and the flocs with adsorbed metals were separated from the tailings solids by the electric field (1 mA/cm2). The electric energy consumption increased with the use of Magnafloc10 (from 17 to 30 kWh/g Cu extracted), due to lower conductivity in the liquid phase and clogging of the membrane by the flocs. In the alkaline electrodialytic treatment (pH > 12), Magnafloc10 reduced the extraction of Cu from 17% to 0.7%, due to the flocs remaining in the tailing slurries. The electric energy consumption per extracted Cu was similar in the acidic and alkaline electrodialytic treatments without the addition of Magnafloc10. In the alkaline electrodialytic treatment, the extraction of other metals was low (<2%), however longer treatment time is necessary to achieve similar Cu extraction as in the acidic electrodialysis. Depending on the target and timescale for treatment, acidic and alkaline electrodialysis can be employed to reduce the Cu concentration in the mine tailings thereby reducing the metal toxicity potential.

Post-depositional behaviour of mercury and arsenic in submarine mine tailings deposited in Buyat Bay, North Sulawesi, Indonesia

The post-depositional geochemical behaviour of mercury and arsenic in submarine mine tailings from the Mesel Gold Mine in Buyat Bay, North Sulawesi, Indonesia was assessed by in situ sampling of tailings porewaters using dialysis arrays and seawater and fish monitoring. Under steady-state conditions one year after cessation of tailings discharge, the calculated arsenic efflux incrementally added 0.8 μg/L of arsenic to the overlying seawater. The mercury efflux across the tailings-seawater interface was negligible. The arsenic and mercury concentration in seawater bottom samples monitored biannually during a 9-year post-closure program were 1.54 μg/L and <0.05 μg/L, respectively. Analysis of 650 fish tissue samples, from the post-closure monitoring had mean mercury and arsenic concentrations consistently below the FAO/WHO CODEX, and Australian and New Zealand National Food Standards, respectively. The results of the porewater, seawater and fish tissue demonstrate that the arsenic and mercury-bearing bearing compounds in the tailings are geochemically stable.

Effects of submarine mine tailings on macrobenthic community structure and ecosystem processes

A mesocosm experiment with intact benthic communities was conducted to evaluate the effects of mine tailings on benthic community structure and biogeochemical processes. Two types of tailings were supplied from process plants using flotation and flocculation chemicals, while a third type was absent of added chemicals. All tailings impacted the sediment community at thin layers, and through more mechanisms than merely hypersedimentation. In general, the strongest impact was observed in a very fine-grained tailings containing flotation chemicals. The second strongest occurred in tailings with no process chemicals. The tailings with flocculation chemicals initiated the weakest response. Fluxes of oxygen, nitrate and ammonium provided some indications on biodegradation of organic phases. Release of phosphate and silicate decreased with increasing layer thickness of all three tailings. A threshold level of 2cm was identified both for faunal responses and for fluxes of phosphate and silicate. The particular impact mechanisms should receive more attention in future studies in order to minimize the environmental risk associated with tailings disposal.