Kinetics of sulfide mineral oxidation in seawater: Implications for acid generation during in situ mining of seafloor hydrothermal vent deposits

Bilenker, Laura; Romano, Gina Y.; McKibben, Michael A.

doi:10.1016/j.apgeochem.2016.10.010

Cited by 34 publications

(20 citation statements)

References 43 publications

(51 reference statements)

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“…Whilst there is still the potential for toxicity and leaching, the in situ extraction is argued to pose less of a risk as a result of the larger grain sizes of the arising particulates (less surface area available for leaching as well as a quicker settling rate, reducing the time the sulphide is exposed for leaching) (Gwyther, 2008). In particular, a study by Bilenker et al (2016) suggests that acid generation during in situ mining is slow and unlikely to be problematic.…”

Section: Discussionmentioning

confidence: 99%

“…The majority of previous dissolution studies are related to terrestrial acid mine drainage arising from mine flooding and leaching of tailings piles by meteoric waters (Acero et al, 2009;Bonnissel-Gissinger et al, 1998;Constantin and Chiriţă, 2013;Descostes et al, 2004;Kwong et al, 2003;McKibben and Barnes, 1986;Moses et al, 1987). A small number of dissolution studies of specific sulphide minerals in seawater have been undertaken (Bilenker, 2011;Bilenker et al, 2016;Feely et al, 1987;Romano, 2012) and demonstrate the large difference in oxidation rates between different sulphide minerals, in particular, the two order of a magnitude difference in abiotic oxidation rates between pyrrhotite and chalcopyrite. These rates quantitatively predict that any acid production from 'in situ' mining of SMS deposits will be buffered by advecting seawater and that mine waste has the potential to persist on the seafloor for years without complete oxidative transformation (Bilenker et al, 2016).…”

Section: Equationmentioning

confidence: 99%

“…A small number of dissolution studies of specific sulphide minerals in seawater have been undertaken (Bilenker, 2011;Bilenker et al, 2016;Feely et al, 1987;Romano, 2012) and demonstrate the large difference in oxidation rates between different sulphide minerals, in particular, the two order of a magnitude difference in abiotic oxidation rates between pyrrhotite and chalcopyrite. These rates quantitatively predict that any acid production from 'in situ' mining of SMS deposits will be buffered by advecting seawater and that mine waste has the potential to persist on the seafloor for years without complete oxidative transformation (Bilenker et al, 2016). However, these studies are typically undertaken with relatively large grain size fractions > 45 m and are representative of 'in situ' mining/extraction rather than the potentially more impactful dewatering and return processes that involves grains < 8m.…”

Section: Equationmentioning

confidence: 99%

“…It has also been reported in numerous dissolution studies (Ahonen et al, 1985;Berry et al, 1978;Jyothi et al, 1989;Mehta and Murr, 1983, 1982, Natarajan, 1988, 1985, Natarajan and Iwasaki, 1983Yelloji Rao and Natarajan, 1989) that the presence of bacteria such as Thiobacillus ferroxidans in a polymetallic sulphide mixture can accelerate galvanic interactions signifcantly. Whilst the role of microbes is highly important in the longer-term, in-situ, natural oxidation of seafloor sulphide ore deposits, it has been suggested that abiotic oxidation rates of sulphide minerals are more relevant to the oxidation of sulphides during seafloor mining (Bilenker et al, 2016;McBeth et al, 2011). It is postulated that bacterial colonization of freshly ground mineral surfaces is unlikely under the rapid time spans of mining (<30 minutes based on mining scenarios outlined by Nautilus Minerals Inc.…”

Section: Toxicity Potentialmentioning

confidence: 99%

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Experimental leaching of massive sulphide from TAG active hydrothermal mound and implications for seafloor mining

Fallon

Niehorster

Brooker

et al. 2018

Marine Pollution Bulletin

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Seafloor massive sulphide samples from the Trans-Atlantic Geotraverse active mound on the Mid-Atlantic Ridge were characterised and subjected to leaching experiments to emulate proposed mining processes. Over time, leached Fe is removed from solution by the precipitation of Fe oxy-hydroxides, whereas Cu and Pb leached remained in solution at ppb levels. Results suggest that bulk chemistry is not the main control on leachate concentrations; instead mineralogy and/or galvanic couples between minerals are the driving forces behind the type and concentration of metals that remain in solution. Dissolved concentrations exceed ANZECC toxicity guidelines by 620 times, implying the formation of localised toxicity in a stagnant water column. Moreover, concentrations will be higher when scaled to higher rock-fluid ratios and finer grain sizes proposed for mining scenarios. The distance at which dilution is achieved to meet guidelines is unlikely to be sufficient, indicating a need for the refinement of the mining process.

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Section: Discussionmentioning

confidence: 99%

Section: Equationmentioning

confidence: 99%

Section: Equationmentioning

confidence: 99%

Section: Toxicity Potentialmentioning

confidence: 99%

See 2 more Smart Citations

Experimental leaching of massive sulphide from TAG active hydrothermal mound and implications for seafloor mining

Fallon

Niehorster

Brooker

et al. 2018

Marine Pollution Bulletin

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“…Whilst slower, there have also been studies reporting bioleaching of sulfide minerals at neutral pH conditions [21,22]. It has been postulated that colonization of freshly ground mineral surfaces is unlikely under the rapid time spans of mining (<30 min based on mining scenarios) [23,24]. However, bioleaching does have the potential to be a concern if mining occurs over months of operation as well as once any fine sulfide material has settled after initial extraction and dewatering [4].…”

Section: Introductionmentioning

confidence: 99%

Geological, Mineralogical and Textural Impacts on the Distribution of Environmentally Toxic Trace Elements in Seafloor Massive Sulfide Occurrences

et al. 2019

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With mining of seafloor massive sulfides (SMS) coming closer to reality, it is vital that we have a good understanding of the geochemistry of these occurrences and the potential toxicity impact associated with mining them. In this study, SMS samples from seven hydrothermal fields from various tectonic settings were investigated by in-situ microanalysis (electron microprobe (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)) to highlight the distribution of potentially-toxic trace elements (Cu, Zn, Pb, Mn, Cd, As, Sb, Co, Ni, Bi, Ag and Hg) within the deposits, their minerals and textures. We demonstrate that a combination of mineralogy, trace element composition and texture characterisation of SMS from various geotectonic settings, when considered along with our current knowledge of oxidation rates and galvanic coupling, can be used to predict potential toxicity of deposit types and individual samples and highlight which may be of environmental concern. Although we cannot quantify toxicity, we observe that arc-related sulfide deposits have a high potential toxicity when compared with deposits from other tectonic settings based on their genetic association of a wide range of potentially toxic metals (As, Sb, Pb, Hg, Ag and Bi) that are incorporated into more reactive sulfosalts, galena and Fe-rich sphalerite. Thus, deposits such as these require special care when considered as mining targets. In contrast, the exclusive concern of ultra-mafic deposits is Cu, present in abundant, albeit less reactive chalcopyrite, but largely barren of other metals such as As, Pb, Sb, Cd and Hg. Whilst geological setting does dictate metal endowment, ultimately mineralogy is the largest control of trace element distribution and subsequent potential toxicity. Deposits containing abundant pyrrhotite (high-temperature deposits) and Fe-rich sphalerite (ubiquitous to all SMS deposits) as well as deposits with abundant colloform textures also pose a higher risk. This type of study can be combined with “bulk lethal toxicity” assessments and used throughout the stages of a mining project to help guide prospecting and legislation, focus exploitation and minimise environmental impact.

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Impacts of deep‐sea mining on microbial ecosystem services

Orcutt

Bradley

Brazelton

et al. 2020

Limnology & Oceanography

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Interest in extracting mineral resources from the seafloor through deep-sea mining has accelerated in the past decade, driven by consumer demand for various metals like zinc, cobalt, and rare earth elements. While there are ongoing studies evaluating potential environmental impacts of deep-sea mining activities, these focus primarily on impacts to animal biodiversity. The microscopic spectrum of seafloor life and the services that this life provides in the deep sea are rarely considered explicitly. In April 2018, scientists met to define the microbial ecosystem services that should be considered when assessing potential impacts of deep-sea mining, and to provide recommendations for how to evaluate and safeguard these services. Here, we indicate that the potential impacts of mining on microbial ecosystem services in the deep sea vary substantially, from minimal expected impact to loss of services that cannot be remedied by protected area offsets. For example, we (1) describe potential major losses of microbial ecosystem services at active hydrothermal vent habitats impacted by mining, (2) speculate that there could be major ecosystem service degradation at inactive massive sulfide deposits without extensive mitigation efforts, (3) suggest minor impacts to carbon sequestration within manganese nodule fields coupled with potentially important impacts to primary production capacity, and (4) surmise that assessment of impacts to microbial ecosystem services at seamounts with ferromanganese crusts is too poorly understood to be definitive. We conclude by recommending that baseline assessments of microbial diversity, biomass, and, importantly, biogeochemical function need to be considered in environmental impact assessments of deep-sea mining.With increasing demand for rare and critical metals-such as cobalt, copper, manganese, tellurium, and zinc-there is increasing interest in mining these resources from the seafloor (Hein et al. 2013; Wedding et al. 2015;Thompson et al. 2018). The primary mineral resources in the deep sea that attract attention fall into four categories (Figs. 1, 2): (1) massive sulfide deposits created at active high-temperature hydrothermal vent systems along mid-ocean ridges, back-arc spreading centers, and volcanic arcs, from the mixing of mineral-rich, advecting hydrothermal fluids with bottom seawater; (2) similar deposits at inactive hydrothermal vent sites, where fluid advection has ceased but mineral deposits remain; (3) polymetallic nodules that form on the seafloor of the open ocean

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Kinetics of sulfide mineral oxidation in seawater: Implications for acid generation during in situ mining of seafloor hydrothermal vent deposits

Cited by 34 publications

References 43 publications

Experimental leaching of massive sulphide from TAG active hydrothermal mound and implications for seafloor mining

Experimental leaching of massive sulphide from TAG active hydrothermal mound and implications for seafloor mining

Geological, Mineralogical and Textural Impacts on the Distribution of Environmentally Toxic Trace Elements in Seafloor Massive Sulfide Occurrences

Impacts of deep‐sea mining on microbial ecosystem services

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