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By James R. Hein

Rodriguez Seamount, located 150 km off the central California coast at the base of the continental slope, was studied using the ROV Tiburon aboard MBARI?s R/V Western Flyer, October 13-16, 2003. Fe-Mn crust and rock samples were collected along the SW flank of the seamount at water depths from 700 to 2100 m; bottom-water dissolved oxygen content (O2) and temperature were determined at each sample site. Fifty-three samples of bulk crusts, crust layers, and surface scrapes (~0.5 mm) were analyzed for 59 elements. Data allow for the correlation of crust compositions with precisely known water depths and seawater O2 measured at the actual site of sample collection. This is the first detailed study of Fe-Mn crust compositions in a region of strong continental-margin upwelling. Compared to open-ocean seamount Fe-Mn crusts, Rodriguez crusts have significantly higher (2-6 fold) mean concentrations of Fe (26.9%), Al (1.65%), Si (13.0%), Cr (82 ppm), Th (64 ppm), and Ag (1.7 ppm); and significantly lower (2-8 fold) mean concentrations of Ca, P, Bi, Co, Cu, Ni, Tl, and especially Te (8.2 times lower). All but one Fe/Mn ratio are >1 compared to <1 ratios for open-ocean crusts. O2 contents (0.35-2.03 ml/L) are nearly perfectly corrected with water depth and elements correlated with one are correlated with the other. The Fe-Mn surface scrapes represent 60-450 ka (mean 150 ka) of growth, whereas the dissolved oxygen contents of seawater represent an instant in time. Assuming that the entire sample set was affected uniformly by oceanographic changes, we suggest that correlation of elements with O2 may reflect oceanographic processes. O2 has a negative correlation with P, V, As, Fe, U, Be, Pb, Cr, Mg, Y, Bi, Te, and REEs (except Ce) and a positive correlation with aluminosilicate-hosted elements (Al, K, Rb, Cs). This later relationship is related solely to water depth, indicating that detritus shed down the seamount slopes accumulates in greater abundances in deeper-water crusts. Si/Al ratios indicate that the detritus includes a large component of biosilica produced by upwelling-mediated high productivity. These observations are supported by positive correlations of aluminosilicate-hosted elements with crust growth rates (range 1.2-13.0 mm/Myr). In contrast, other elements (Sr, Co, Mn, Mg, Te, As, Mo, V, W, U, Ti, Ni, REEs, etc.) are negatively correlated with growth rates. Growth rate has a weak positive correlation with O2. These compositional characteristics indicate that even though low-O2 seawater acts as a reservoir for Mn and associated elements and produces slow growth rates, which would allow for the concentration of elements and surface oxidation processes to occur, the high rate of input of detritus and high bioproductivity ameliorate the strong concentration of most metals. This dilution is significantly enhanced by the doubling of FeOOH in the crusts--the main cause of the generally high growth rates compared to open-ocean crusts. The high growth rates limit the oxidation of Co, Tl, and especially Te on the crust surface, which is reflected by their relatively low concentrations. Within the range of oxygen contents measured, O2 has less of an influence on crust chemistry than does the availability and incorporation of FeOOH and detritus.

Jan 1, 2004

The Brothers hydrothermal system is host to two very contrasting vent fields and to date, is the only known example of this kind for any submarine arc volcano in the world. Firstly, there is the NW caldera field. It is perched on the caldera walls and is up to 1,200 years old, and represents a more ?mature? system dominated by water/rock interactions, though there is also evidence for magmatic contributions to the hydrothermal fluids. It is host to relatively high temperature (~300°C), focused venting of metal-rich fluids. Large Cu- and Zn-rich sulfide chimneys occur at this site, with high concentrations (up to 90 ppm) Au apparent in some chimneys. Vent fluids of the NW caldera site show sub-seafloor phase separation is occurring at this site. Silica concentrations in these vent fluids are consistent with the vent fluid temperatures. Secondly, there is the cone vent field that is much younger, and which sits atop the summits of a main cone (the Upper cone) and an adjacent satellite cone (the Lower cone) that occur inside the caldera, near the southern caldera walls. This field is dominated by S-rich vents with vent fluids more diffuse, lower in temperature (<120°C), very gassy and acidic (to pH 1.9), and relatively metal-poor. Fluids of the cone site have Mg and SO4 concentrations higher than seawater values, indicating these ions have been added to the hydrothermal fluid and are not being depleted via normal water/rock interactions. Variability occurs between the two cone vent fields, with the diffuse discharge observed at the Upper cone volumetrically small and chemically different from the Lower cone. For example, from the vent fluid Mn, Li, Rb, and Cs concentrations, it is apparent that the Lower cone has experienced a lower degree of water/rock interaction (i.e., more reaction) than the Upper cone. Vent fluid pH is higher for Lower cone, consistent with more reaction and neutralization of acidic gases. Fe/Mn is lower at the Lower cone due to decreased Fe solubility at the higher pH. The lowest pH sample (1.9) is from the Upper cone that has 39.4 mmol/kg of SO4, consistent with input of magmatic SO2 and disproportionation to sulfuric acid and S or H2S. Thus, the Upper cone site could be interpreted to have a shorter reaction path and residence time between the point of magmatic degassing and the seafloor venting than the Lower cone site. Isotopic compositions of the NW caldera and cone vent fluids show evidence for magmatic water with negative dD and d180 values, while 3He/4He values show the Brothers hydrothermal system has shifted towards more magmatic conditions over the past several years with both sites affected by magmatic events. Similarly, vent fluid sulfide d34S values and those for sulfide minerals from NE caldera chimneys also indicate disproportionation reactions involving magmatic SO2. Minerals such as chalcopyrite, bornite, chalcocite, covelllite and euhedral grains of hematite occurring in high temperature chimneys from the NW caldera site are consistent with a more oxidizing, magmatic fluid, while bulk sulfide geochemistry data show evidence for a higher temperature suite of elements (e,g., Mo, Co, Se) associated with Cu-rich chimneys. Gold mineralization occurs in these high temperature chimneys and is associated with the most recent deposition of high concentrations of Cu, where d34S values are most negative. Geophysical evidence suggests that the top of a magma chamber occurs ~2.5 km below the caldera floor, beneath the cone site in the SSE quadrant of the volcano. Very low velocities of <1 km-2 are seen in the seismic data between the magma and the seafloor, and are indicative of gas release. Harmonic tremor data provide evidence for a 500 m pipe-like ?conduit? located above the magma chamber (and below the cone), linking it with the overlying hydrothermal system, providing a mechanism for magma-derived metals to enter the hydrothermal system under the cone site. The NW caldera and cone sites are considered to represent stages along a continuum between magmatic-hydrothermal and water/rock-dominated end-members.

Jan 1, 2010

By Karsten Hagenah, Tor Jensen, Jens Laugesen, Øyvind Fjukmoen, Lucy Brooks

"The methods and technologies to be used for environmental monitoring of seabed mining activities are a key issue. Due to the large water depths, there are special challenges with respect to the monitoring equipment that is suitable. DNV GL has built up substantial experience of environmental monitoring from oil & gas projects in deep waters in the Norwegian Sea.Monitoring equipment and experiences from the oil & gas sector can to a large extent be applied to seabed mining.BackgroundThe International Seabed Authority is currently developing an environmental management strategy for the Area (ISA, 2017) as a part of the work on the regulations for exploitation for mineral resources in the Area.The draft environment strategy contains provisions related to monitoring and reporting of the activities. An Annex (Annex III) of the draft document describes the format and content of the environmental management and monitoring plan.The monitoring plan should contain, inter alia: ?Technology to be deployed.?Monitoring frequency of respective elements/components of the Marine Environment.?Monitoring procedures required to implement the Monitoring programme.?Details of the environmental monitoring stations across the Environmental Impact Area.?Monitoring specifics e.g. water quality; sedimentation rates; sound; plume extent; etc., as well as relevant Environmental Targets.?Monitoring of Mining Discharges.?Processes for Monitoring reviews and Environmental audits."

Jan 1, 2017

By Jae-Hyung Park

Since the Industrial Revolution, the land resources have been decreased rapidly as the industrialization. And this phenomenon brings to our mind an interest in deep-sea resource(manganese nodule). Hence, Korea has been participated in the development project of exploiting manganese nodule since 1983. Hwang and cho(1998) studied the economic efficiency evaluation of manganese nodule carrier. But they used the TAMU(Texas A&M University) model, and assumed deadweight and velocity of bulk-carrier. If we use some optimization technique, more economic manganese nodule carrier can be selected and evaluated without limited assumption. In this study, we evaluated the economic efficiency of manganese nodule carrier using genetic algorithms(GAs).

Jan 1, 2003

By Glen Smith

Nautilus Minerals is the world leader in exploration and development of deep ocean seafloor massive sulphide (SMS) resources. The company is currently focused on generating its resource pipeline in the Western Pacific and its first development project for recovery of high-grade copper, gold and silver mineralisation from its Solwara 1 site in the Bismarck Sea, Papua New Guinea. The Solwara 1 site is located at a water depth of 1,600 ? 1,800 meters. Over 150 SMS seafloor surface samples have been collected from chimney structures during dives made by remote operated vehicles (ROVs). In order to obtain an understanding of the sub-surface mineralisation, Nautilus carried out 4 drilling programs between 2006 and 2010 which allowed the calculation of a Canadian NI43-101 compliant resource estimate. The initial 2006 campaign was based on conventional offshore surface driven drill equipment. In conjunction with the subsea remote technology industry, Nautilus subsequently developed an ROV operated seafloor drill system with improved drill core recovery and efficiency. This technology was developed further with a 2010 - 2011 drill program to increase the available geological knowledge at Solwara 1 and adjacent prospects. his paper will provide an overview of Nautilus? SMS drilling requirements and recap the evolution of drilling technology and operations undertaken at Solwara 1 from 2006 to 2011. The paper will also discuss the potential of further developments in drilling techniques and equipment to increase or improve drilling depth, efficiency and data quality.

Jan 1, 2011

By Tatiana ?. Sedysheva, Vladimir V. Ivanov, Michail E. Melnikov, Irina A. Pulyaeva

"INTRODUCTIONHydrogenetic Fe-Mn crusts are ubiquitous in the ocean basins and play an important role in marine mineral-deposit research because of their widespread occurrence and high concentrations of valuable and rare metals. Directed research, which started in the last quarter of the 20th century, has provided significant results, with substantial amounts of data produced on Fe-Mn crusts structure, composition, and distribution in the global ocean [3, 4 - 8]. Now, commercial interests gain more and more attention. Mining systems are being developed which involve fragmentation of the crusts and their separation from the substrate. The effectiveness of such activities greatly depends on physico-mechanical characteristics of the crusts and rocks on which they form. This determines the importance of the engineering geological study of the objects.This article comprises the results of the engineering geological studies of the crusts samples (72 samples) and their underlying rock substrates (75 samples), which were carried out during the research cruises 6-06, 6-07, 6-08, 6-13 (2006-2013) on the Magellan Seamounts guyots in the Western part of the Pacific Ocean by the specialists of the State Scientific Centre Yuzhmorgeologia [10 - 13, 19, 20]. The authors of the article directly participated in the studies mentioned above.MethodsEngineering geological studies were carried out on board of the research vessel Gelendzhik and in the laboratories of NPA «Sevmorgeologiya». The studies involved the determination of the following parameters:"

Jan 1, 2017

By Elizabeth McIsaac, Wylie Spicer

"In July 2016 the International Seabed Authority (the “ISA”) released a first working draft of its mineral exploitation regulations as well as the standard contract terms for mineral resources in the Area, for which stakeholder input was sought in late 2016. In January of 2017 the ISA released a discussion paper on environmental matters related to these draft regulations. The ISA is now in the process of further developing its draft exploitation regulations and standard contract terms to ensure that seabed mining is carried out in an environmentally sound way for the common benefit of mankind.As the regulator of the “Area”, the ISA can draw lessons from onshore mining regulators and offshore petroleum regulators for their experiences in legislative drafting to smoothly and safely oversee project development, implementation, and closure. However, one of the unique challenges that the ISA faces in regulating private industry is its status as an international organization and not a sovereign nation, which results in a significantly different legal relationship between the regulator and the regulated. The result is that the exploitation contract is the sole legal connection between the mining proponent and the regulator for the exploitation phrase of the project.Accordingly, in the regulatory development process, the ISA must carefully consider which rights and obligations are set out in the exploitation contract versus the regulations. This decision will dictate the flexibility the ISA will have to modernize the conduct required of mining proponents in response to changing best practices in the industry, technological progress, and advances in the understanding of the marine ecosystem. As the first working draft of the exploitation regulations sets out an initial contract period of twenty years, it is crucial for the ISA to carefully consider the rights, obligations, and procedures it agrees to in the exploitation contract, as unilateral amendment will not be possible after contract execution."

Jan 1, 2017

By Tony van der Steen

Subsea mining system are designed for the following, principally different, tasks: Dreding - The destruction and removal of seabed sediments overlaying the bedrock. Cleaning - The competence of the system to systematically remove the deposits from an undulating hard bedrock with irregular pulleys, channels and fissures. Factors that influence the choice of dredging equipment for a specific project are project requirements such as environmental conditions, location and water depth. However, the most important selection criteria are soil conditions. As a consequence, possible dredging systems, must be evaluated for the following, principally different, characteristics: Dredging proficiency - The destruction of the strata by the equipment. System stability - The capability of the soil to support the subsea equipment The above parameters are determined by the strength characteristics and the bearing capacitv_ of the soil. The author describes the processes involved in excavating the subsea deposits and (transporting the gathered soil as a water-soil mixture to the surface using different excavation and transport methods.

Jan 1, 1998

By Isobel Yeo, Florent Szitkar, Sven Petersen, Sebastian Graber, Nico Augustin, Marcel Rothenbeck, John Jamieson

"INTRODUCTIONSeafloor massive sulfides (SMS) along mid-ocean ridges are often seen as a possible future contribution to a secure metal supply for global human needs. A growing interest over the past few years resulted in six national exploration licenses and one application pending, covering 10,000 km2 each, that have been brought before the UN International Seabed Authority (ISA) since 2011. Each contractor has to explore these 10,000 km2 within the 15-year runtime of the contract. However, the need to define areas that are not economically interesting is more pressing, as 50% of the 100 license blocks have to be returned to ISA after only eight years - hopefully areas that do not contain large and economically interesting SMS deposits. Current geochemical prospecting technologies, however, have mainly been developed for the search for active hydrothermal systems (e.g. hydrothermal vents and associated black smokers) that can easily be traced through physical and chemical anomalies in the water column (temperature, chemical variations of elements such as Mn, Fe, redox potential, and/or the particle concentration in the water column). Such plume surveys have been a primary tool for exploration of SMS systems, but they only identify active, and therefore mostly young and small hydrothermal systems. In a recent high-resolution AUV survey performed within the EU-FP7 funded project “Blue Mining”, we covered 47 km2 along the TAG segment of the Mid-Atlantic Ridge to test exploration methodology for fast and reliable exploration of larger areas of the seafloor for inactive seafloor massive sulfide occurrences using the autonomous underwater vehicle (AUV) “Abyss”."

Jan 1, 2017

By Andrew E. Grosz

The Atlantic Continental Shelf (ACS) of the United States includes about 391,000 km2 extending from the shoreline to the 200-m isobath. It varies in width from a fraction of a kilometer (offshore of southern Florida) to about 150 km (offshore of Cape Cod, MA). The contained volume, of sand and gravel is estimated to be on the order of 3-7 x 1.011 m3. Concentrations of potentially commercially important heavy minerals (HM) exist locally, particularly in high-energy depositional environments (for example in channels, tidal deltas, ridge and swale areas, and submerged former shoreline complexes). Recently completed and ongoing studies of HM assemblages in vibracore samples from the south shore of Long Island Sound, NY, offshore of Ocean City, NJ, offshore of Cape May, NJ, offshore of the mouth of Chesapeake Bay, VA, offshore of Myrtle Beach, SC (grab samples), and the ACS offshore of Florida provide the information base for this presentation (Table 1). The surficial sediments of the ACS contain local concentrations of HM that compare favorably to those in currently mined onshore deposits as shown

Jan 1, 1988

By Michael R. Gipp

Marine Mining Inc. is currently exploring for marine alluvial gold and diamonds on a prospecting licence over a concession that covers 10,000 km2 of the continental shelf of Ghana. The boundaries of the concession extend from 0 30&apos;W to 2 40&apos;W, and between the shoreline and approximately the continental shelf edge north of 4 30&apos;N. This concession extends from Kikam Beach in the west, to Senya Beraku in the east, a distance of approximately 240 km, and seaward an average of about 40 km. The concession is entirely underwater, with the exception of the estuaries of the Ankobra and Pra Rivers. Ghana has been a large source of alluvial gold, with historical production exceeding 25 million ounces. Southwestern Ghana is characterized by Precambrian rocks, which have been folded into a number of NE-SW trending synclines and anticlines. The most significant feature of the Birimian rocks is the presence of evenly spaced gold-bearing greenstone belts. They are 10-15 km wide, separated by about 90 km, separate basins filled by folded metasediments and granitoids. The rivers that enter the concession drain most of the exposed gold-bearing belts of Ghana. Given that approximately 2 km of erosion has taken place since the Mesozoic, and that gold mines on these belts boast proven reserves of over 55 million ounces, it is likely that large amounts of gold have been eroded out and carried to the sea. Coastal fractures, related to Precambrian structures reactivated during Mesozoic rifting, are responsible for the physiography of the coastal area, which consists of high-relief horsts separated by grabens that have been occupied and infilled by rivers or by finer sediments during times of elevated sea level. These fractures were loci of gold mineralization during the Precambrian, and are the source of alluvial gold in rivers confined by them.

Jan 1, 1998

By Robert G. Ditchburn

The NW caldera hydrothermal vent field at Brothers volcano, of the Kermadec-Tonga arc, has associated massive sulfide mineralization. This includes an abundance of black smoker chimneys that contain significant concentrations of copper, lead, zinc and gold (de Ronde et al., 2005; de Ronde et al, 2010, under review). [ ] The oldest volcanic massive sulphide (VMS) samples recovered so far from Brothers have been dated using radiometric methods at GNS Science and found to be c. 1000 years old. By contrast, a volcanic cone that has formed in the southern part of the caldera has no associated VMS. Only elemental sulphur and Fe-oxide crusts are present here, samples of which have been analysed for their trace elements. From d34S values of sulfates and native sulfur, and the volume of gas (dominated by CO2 and H2S) discharging at the cone site, elements being deposited here are considered more directly magmatic in origin (de Ronde et al., 2005; 2010 under review). It has been discovered that deep-seated changes in volcanic activity at Brothers affect the NW caldera and cone site simultaneously, though the mineralogy at each site is so very different. Thus, the cone site is being studied to determine if elements being deposited there can be used as predictors of potential future VMS mineralisation as similar sites have been found at other volcanoes along the Kermadec arc and elsewhere. The frequency of these deep-seated magmatic events is considered important in the formation of Cu-Au-rich mineralization along arcs. The analysis of Fe within resulting hydrothermal plumes (surveyed by surface vessels), and trace elements in rock and mineral samples, are used to help determine the influence of magmatic contributions to the hydrothermal system. To verify that plumes are a reliable proxy for hydrothermal events depositing iron on the seafloor, Fe-oxide crusts from Brothers volcano cone have been dated to see if their emplacement coincides with highly Fe-enriched plumes in the water column. The radiometric dating techniques developed for barite-rich VMS, i.e. using 228Ra and 226Ra, were unsuitable for the Fe-oxide crusts because 210Pb was the only isotope detected by gamma spectrometry. Therefore, new techniques using 210Pb, 10Be and arsenic have been established.

Jan 1, 2010

By Maria Baker, Kristina Gjerde, Lisa Levin, Verena Tunnicliffe, Lenaick Menot, Rachel Boschen

Deep-sea mining is rapidly approaching the test-mining phase to prepare for commercial mining in multiple oceans, both in areas within and beyond national jurisdiction. The first test-mining operations are likely to focus on seafloor massive sulfides found at active and inactive hydrothermal vents within national jurisdictions – possibly in the coming months. Beyond national jurisdictions, the International Seabed Authority (ISA) is developing the regulations to oversee exploitation of polymetallic nodules, massive sulfides and cobalt crusts. The Deep Ocean Stewardship Initiative (DOSI) minerals working group has, over the last 3 years, made formal submissions on the regulatory framework, on the draft exploitation regulations, on the article 154 review of ISA and on the initial environmental regulations. In advance of both test and commercial mining, we urgently need to identify and develop comprehensive, ecosystem-based management practices for deep-ocean environments subject to mineral extraction. Transparent criteria for deep-sea institutional and corporate social responsibility also need to be established. Proactive development of management practices, frameworks and policy prior to the onset of mining will facilitate some degree of protection and preservation of the marine environment, whilst enabling the use of seabed mineral resources. The DOSI minerals working group constitutes a broad spectrum of scientific, industry, legal and policy expertise. We provide expert opinion, both in collated and individual response forms, on deep-sea mining related concerns to ISA and national bodies. Our publications and workshops on key concepts raise awareness and provide scientific updates on ecosystems targeted for mining. See http://www.dosiproject. org minerals working group and join us to further this work.

Jan 1, 2017

By T. E. Sedysheva

The study of Co-rich manganese crusts has reached the level which allows to start prospecting works in the observable future, and furthermore, probably, exploitation of ore deposits. In this connection, among other goals, the necessity to analyze a distribution of ore bed parameters in details is quite urgent. Foremost, these are crust thicknesses in connection with landforms and elements of submarine mountains relief. This report is based on representative sampling made in course of research cruises run by SSC Yuzhmorgeologiya over guyots of the Magellan Seamounts. Crustal covers could overlie seafloor surfaces which are confined to a various landforms and elements of relief under the condition, that they are free of sediments. These are planed parts of a summit surfaces, edges, spurs, rectilinear parts of slopes, intermountain saddles and volcanic edifices. It is known, that crustal thicknesses are different at a various forms of relief [1]. We processed statistically the data around crustal thicknesses, which were sampled by dredging and submersible drilling (Tables 1, 2).

Jan 1, 2010

By Mark Lee, Isobel Yeo, Sarah Howarth, Christian Millo, Javier González Sanz, Paul Lusty, Bramley Murton, Pierre Josso

"Seafloor cobalt-rich ferromanganese crusts represent the most important yet least explored resource of ‘E-tech’ elements on the planet (Hein et al. 2003; ISA, 2008; Hein et al. 2010; Hein et al. 2013). These polymetallic deposits form a continuum from nodules rich in manganese and cobalt to crusts rich in tellurium and the heavy rare earth elements (HREE). It is this combination of traditional (base) metals and the extreme enrichment of ‘E-tech’ elements that makes seafloor ferromanganese oxide deposits particularly interesting to both science and society. Recent estimates of the global resource, based on the sparse data available, infers a dry mass of ferromanganese crusts on the seafloor of 35 x 109 tonnes (35GT). Of this, 3.7 GT is predicted in the Indian Ocean, 8 GT in the Atlantic, and 23 GT in the Pacific (Hein et al. 2013).At a global scale, the processes controlling the formation and distribution of ferromanganese (Fe-Mn) crusts are reasonably well understood (e.g. Hein et al. 2000; Verlaan et al. 2004; Cronan 2006; Halbach et al. 1989; Usui and Someya, 1997; Hein et al. 2000; Hein et al. 2003; Hein et al. 2009; Hein et al. 2010; Hein et al. 2013; Muiños et al. 2013; Marino et al., 2016). However, much of this knowledge is drawn from sparse sampling at a regional to ocean basin scale. As a result, there remains a fundamental gap in understanding of the role of local-scale factors, such as micro-topography, ocean currents and upwelling, sedimentation rates, micro-organisms, water mass composition and biological productivity, that are considered potentially crucial to controlling the growth and composition of Fe-Mn crusts. Indeed, quantitative, particularly temporal, information relating to these processes and their relative importance in deposit formation is almost completely absent. Hence, to make any significant advance in understanding these deposits require significant new research."

Jan 1, 2017

By Gérald Riverin

Over the past century, exploration methods for volcanogenic massive sulphide deposits have evolved in response to a decreasing number of discoveries made by traditional surface prospecting and by ground and airborne geophysics. Statistical trends support the concept that fewer and fewer outcropping and sub-cropping VMS discoveries will be made in the future. In turn, this creates new opportunities to develop more sophisticated exploration models and techniques to explore at greater depth and to make blind discoveries. Current exploration models include various combinations of geological, geochemical and geophysical criteria which have been based on the results of land-based VMS research. The role of seafloor research in the development of these models has so far been only of a subordinate nature, perhaps due to a lack of direct involvment of the exploration industry in the seafloor research, and vice-versa for the seafloor researchers in VMS exploration. Another contributing factor is that exploration relies on exploration criteria that result from detailed geological, geochemical and geophysical studies of both footwall and hanging wall rocks, studies that are not possible in modern sea floor environments. Nevertheless, seafoor research has contributed to our understanding of the growth of sulphide mounds, the mechanism of sulphide deposition and of the chemistry of fluids involved in VMS systems. In particular, the role of structure and of tectonic setting has been clarified through observation of active seafloor hydrothermal systems. In turn, observations made in land-based VMS research has helped seafloor researchers to focus on key issues which, will eventually contribute to improved exploration models.

Jan 1, 1998

By Jeremy Spearman, Alan Cooper, Mark Lee, Jon Taylor, Michael Turnbull, Neil Crossouard, Bramley Murton

"SUMMARYSeamounts are underwater mountains caused by volcanic activity. They are of great oceanographic interest because of their local and basin-scale influence over ocean systems, their often unique ecosystems, and because they are associated with the formation of ferromanganese (Fe-Mn) crusts. These crusts are of particular interest to scientists because they are rich in some of the rare elements increasingly required for development of renewable technologies. When the possibility of mining such seamounts is considered, an inter-disciplinary study of seamount hydrodynamics, crust formation and ecosystem sensitivity is required. MarineE-tech is one such multi-disciplined project that has been commissioned to address these different aspects in order to improve understanding of the viability and desirability of mining Fe-Mn crusts. This paper describes a key part of this study, namely the development of a model, informed by hydrographic observations, of the currents around one such seamount and the in situ validation of a sediment disturbance plume model as a pre-cursor to assessment of the potential effects of mining activity.INTRODUCTIONFerromanganese crusts are thought to form by precipitation of iron and manganese oxides from oxygen depleted mid-water known as the oxygen minimum zone (OMZ). Oxidation rich waters, typically at depths of about 800-2200 m (Hein et al, 2000). This range of depths coincides with the flanks and summits of many seamounts. The ferromanganese crusts found on seamounts have been found to have high concentrations of rare elements, like Tellurium, that are considered critical to low-carbon energy production. Seamounts are complex environments: in terms of the local hydrodynamics that tend to trap water over the seamount due to the Taylor Cap effect (e.g. Chapman and Haidvogel, 1992) and which can enhance the productivity of seamount waters through upwelling (Lavelle and Mohn, 2010), in terms of the microbiological activity that leads to the precipitation of the Fe-Mn crusts, and also in terms of the often unique ecosystems that are the product of the “island” nature of seamounts and the upwelling of nutrients. The understanding of this complexity is a necessary journey towards the realization of viable, yet environmentally responsible, mining schemes. The formation of crusts will be influenced by the local (and larger-scale) hydrodynamics. The exploration of promising crust sites could be made much more efficient by understanding where the most prospective deposits are likely to occur. Knowing how to remove these crusts without impacting significantly on the local environment will be a pre-requisite for such mining to be acceptable to the public and funders alike."

Jan 1, 2017

By Tetsuo Yamazaki

Seafloor massive sulfides (SMS) in the western Pacific have received much attention as resources for gold, silver, copper, zinc, and lead (Lenoble, 2000). Since the end of the 1980s, SMS have been found in the back-arc basin and on oceanic island-arc areas. The typical representatives found are in the Okinawa Trough and on the Izu-Ogasawara Arc near Japan (Halbach et al., 1989; Iizasa et al., 1999), in the Lau Basin and the North Fiji Basin near Fiji (Fouquet et al., 1991; Bendel et al., 1993), and in the East Manus Basin near Papua New Guinea (PNG) (Kia and Lasark, 1999). The higher gold, silver, and copper contents in one of the areas increased the chance for profitable mining operation, which was considered by a private company (Malnic, 2001). The company gathered investment money and announced to start the commercial mining from 2010 (www.nautilusminerals.com). On the basis of geological information of the Sunrise Deposit of the Myojin Knoll on the Izu-Ogasawara Arc (Iizasa et al., 1999) and geotechnical characteristics of SMS (Yamazaki and Park, 2003), some preliminary economic validation analyses of the SMS mining in small production scale were reported by one of the authors (Yamazaki et al., 2003; Yamazaki and Park, 2005; Yamazaki, 2007). The results showed high profitability of the SMS mining.

Jan 1, 2011

By Irina Melekestseva

The Cu-Zn massive sulfides from the basalt-hosted Semenov-2 hydrothermal field (13°31.13´ N, 44°59.03´ W, MAR) are enriched in Au (22?188 ppm) and Ag (127?1787 ppm) [Ivanov et al., 2008] and elevated contents (ppm) of Se (269?289), Sn (123?125), and Sb (72?75). These may indicate heterogeneous substrate rocks and possible ultramafic rocks. Based on phase analysis, 70% of the gold in the massive sulfides is free. LA-ICPMS analysis has shown that the main carrier of the invisible gold is covellite (22.51? 226.64 ppm). Covellite is also characterized by elevated contents of Se, Mo, Sn, Te, Au, Bi, As, Ag, Sb, Tl, and Pb relative to the primary sulfides.

Sep 14, 2011

By Henk van Muijen, Jan Willem de Wit

1.1 Profile IHC Holland Merwede IHC Holland Merwede is world market leader in the construction of specialist dredging equipment and large-size custom-built offshore vessels. The clients of IHC Holland Merwede include major dredging companies, oil and gas exploration groups, offshore contractors and government authorities. IHC Holland Merwede is focused on the continuous development and innovation of technology to ensure maximum performance and efficiency of its designs and constructions supplied to the dredging and offshore industries. IHC Holland Merwede has a staff of approximately 2,000 at its locations in Hardinxveld- Giessendam, Kinderdijk, Krimpen aan den IJssel, Sliedrecht, Delfgauw, Goes, Hendrik Ido Ambacht and Heusden. Besides worldwide representations, IHC Holland Merwede has branches in China, Houston (USA), India, the Middle East and Singapore. 1.2 Mission IHC Holland Merwede’s mission is to optimize value by anticipating and satisfying its client’s requirements, with efficient advanced technology solutions. The group’s aim is to be consistently at the forefront of technology development, in the business sectors in which it operates.