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By Gary J. Massoth

Wherever hydrothermal fluids vent from the seafloor they will buoyantly rise (up to 100?s of meters) while mixing with seawater before attaining density equilibrium and dispersing laterally as neutrally buoyant plumes commonly 50 to several 100?s of meters in thickness and with order-of-magnitude or greater breadth. Although these plumes are typically >10,000-fold dilutions of vent fluids they can be reliably detected using sophisticated physical sensing and chemical techniques. Hence, hydrothermal plumes are spatially large targets compared to the actual sites of seafloor fluid discharge and resulting mineralization. For this reason plume prospecting techniques evolved over the past 20+ years have been widely used to systematically explore over 10% of the 60,000-km-long system of mid-ocean ridge (MOR) spreading centers for hydrothermal activity. While plume detection and gradient mapping can be used to home in on venting sites, plume chemical signatures provide additional insight regarding the nature of the fluids being discharged on the seafloor. We have applied the systematic plume prospecting techniques developed on MORs to the volcanic frontal arc setting as part of the NZAPLUME (New Zealand American PLUme Mapping Expedition) surveys. NZAPLUME I in March 1999 marked the first systematic reconnaissance of any intra-oceanic arc for submarine hydrothermal activity. Seven of thirteen previously mapped volcanoes that comprise a 260-km-long section of the southern Kermadec arc northeast of New Zealand were confirmed to be hydrothermally active. On average, one hydrothermally active volcano was found along each 35 km of arc front, a rate comparable to slow- and intermediate-rate spreading MORs. During NZAPLUME II in May 2002, thirteen previously unknown volcanoes and 8 satellite cones were first swath mapped for bathymetric detail and then surveyed using plume prospecting techniques. Three active venting sites were discovered along this 580 km-long arc section, bringing the total to 10, or 39% of 26 volcanoes surveyed overall, still an appreciable frequency rate for venting sites compared to MORs. While only chemical results for NZAPLUME I are available, the arc plumes characterized so far are chemically diverse and rich compared to MOR plumes. This diversity and enrichment was most evident as ultra-high concentrations of CO2, sulfur gases (St = SO2 + H2S), and Fe within plumes over several volcanoes. We suggest the fluids discharging from the seafloor at these sites are volcanic fluids, i.e., hybrid fluids comprised of MOR-like hydrothermal fluids evolved from seawater-rock reaction and fluids exsolved from magma as acid volatiles and liquid brines.

Jan 1, 2002

By M. F. Dibble

The technology available for mining of underwater mineral resources such as placers and phosphorite, typically occurring with variable amounts of overburden, has remained largely unchanged for decades. The traditional bucket ladder dredge with maximum digging depth of 48 m and monthly capacities about 500,000 m3 still reins as the only heavy duty mining system capable of working the tough materials characteristic of heavy metal placers. Attempts at adapting the bucket wheel cutter-suction dredge to these severe conditions have not yet been successful except in moving small volumes from shallow depths. High capital cost (20-30 million U.S. dollars), high cost of overburden removable, and turbidity generation for the bucket ladder are often significant negative factors in mining operations where this system remains the only viable alternative. The Japanese continue to advance the technology of their submersible dredge pump system powered by specially adapted, direct drive electric motors. Present systems are designed primarily for working surficial deposits of aggregate to depths as great as 90 meters, the pump suspended by cable from a surface vessel with an eductor pipe leading from the pump to the vessel. Such a system may prove adaptable to a variety of surficial deposits including phosphorite, shell and heavy minerals in addition to aggregate. However promising for the exploitation of surficial deposits, little advantage can be expected for the deeper buried and more difficult deposits.

Jan 1, 1986

By P. A. Rona

The first hydrothermal mineral deposits found at a seafloor spreading center were discovered in the Red Sea by multi-national research vessels between 1963 and 1965. At that time, the deposits were considered a special case related to continental rifting and an early stage of opening of an ocean basin. Since that time, examples of almost all major varieties of volcanic- and sediment-hosted hydrothermal deposits associated with basaltic rocks in the geologic record have been found at present spreading centers. Review of over 100 hydrothermal mineral occurrences presently known at oceanic ridges and rifts indicates that a range of deposit sizes from small to large (> 1 x 106 tonnes) occurs at all seafloor spreading rates. However, larger deposits but fewer per unit length of spreading axis appear to form at slow- than at intermediate- to fast-spreading centers based on available data. Larger deposits are more common in sediment-hosted than in volcanic-hosted settings regardless of spreading rate. A spectrum of hydrothermal deposit varieties (stratiform, stockwork and disseminated sulfides; various forms of sulfate, carbonate, silicate, oxide and hydroxide deposits) occurs in almost all of the tectonic settings. High-intensity, ore-forming, subseafloor, hydrothermal convection systems that conserve heat and mass and concentrate hydrothermal precipitates are extremely localized by anomalous physical and chemical conditions relative to nearly ubiquitous low-intensity hydrothermal activity at and flanking seafloor spreading axes at all spreading rates. Two distinct shapes of volcanic-hosted

Jan 1, 1989

By Randolph A. Koski

Recent investigations located at least six major massive sulfide deposits (dimensions measured in tens to hundreds of meters) within a 50-km-long segment of Escanaba Trough, the sediment-covered axial valley of southern Gorda Ridge. The sediment fill is intercalated silt and sand turbidites and hemipelagic mud with a maximum thickness of 500 m. Several volcanic edifices, spaced at approximately 15-km intervals along the ridge axis, penetrate and locally breach the sediment. The largest sulfide deposits form mounds and ridges on the steep flanks of structurally unstable sediment-capped blocks that have been uplifted above the volcanic edifices; both sediment and sulfide deposits are undergoing rapid erosion and redeposition. Although hydrothermal activity appears to be absent at most sulfide fields, 220°C fluids are discharging from the tops of sulfide mounds near 41°00'N lat, 127°31'W long. Recent pillow lavas and sheetflows erupted onto the sediment-covered sea floor less than 500 m away from the active vent field. The massive sulfide deposits have compositional characteristics that differ from deposits formed on sediment-free spreading axes. The Escanaba Trough deposits include Fe- and Cu-rich, Zn- and Pb-poor massive sulfide mounds, polymetal (Zn-Fe-Pb-Cu-As-Ag-Sb-Sn) sulfide vent structures, abundant barite-rich chimneys, crusts, and sinter cones, and thermogenic petroleum in the sulfide and sediment. Sulfate-rich crusts have high Au values ranging between 2 and 10 ppm. The unusual mineral assemblage at Escanaba Trough

Jan 1, 1989

By Richard H. T. Garnett

The first, profitable, marine placer mining started with tin 100 years ago but no major industry developed until the mid-20th. Century. Dredging at sea yielded cassiterite in both South Thailand and Indonesia, and remains an important state-run industry in the latter country. Malaysia and Russia have also contributed production, and the coastal waters of Tasmania and England have been explored. Marine placer deposits of gold have been examined in New Zealand, Chile, Argentina, Russia and West Africa. Philippino deposits were dredged during the 1930s. Fifty years later, at Nome in Alaska, gold was recovered by dredging from the offshore, and the technical/economic benefits of a seabed-deployed crawler were first demonstrated. Off the coast of Namibia placer diamonds were recovered by airlift mining during the 1960’s, but De Beers effectively started the existing marine diamond industry in 1989. The Wirth drill and a crawler continue to be used by the company, and plans recently have been announced for operations in South African waters. Other commodities such as mineral sands, platinum group minerals, and chromite have been investigated offshore in several worldwide localities.

Aug 24, 2006

By Jonguk Kim

The North Fiji Basin (NFB) is a mature intraoceanic back arc basin with an age of ~12 Ma. Recent volcanism and spreading activity are focused along the Central Spreading Ridge (CSR), A ridge segment more than 800 km long, composed of four main segments, the N160°, N15°, north-south (N-S), and southernmost segments from north to south. The dominant volcanic rock in the entire central spreading ridge is normal mid-ocean ridge basalt (N-MORB), very similar to those emplaced along mid-oceanic ridges. Conversely, influence of an oceanic island basalt (OIB) source increases northward from 18°20'S. Several basalts which show a significant subduction-related component are also observed in the southern part of the NFB. Hydrothermal activity along the spreading centers of the North Fiji Basin was investigated by several previous works, especially by the STARMER project in 1989 and 1991. Both extinct and active hydrothermal vents are found on the N15° and N-S segments. In contrast, only traces of hydrothermal activity have been found on the N160° segment. Although high temperature activity and related massive sulfide deposit on the N15° segment was further investigated by several follow-up studies, no systematic survey for other hydrothermal sites was conducted after their discovery. In 2012 and 2013, KIOST performed two hydrothermal expeditions aboard the R/V Onnuri in the three targeted areas of hydrothermal activity along the CSR of North Fiji Basin. All targeted areas include sites for hydrothermal activity reported in previous works. Occurrence and distribution of hydrothermal plume were investigated by combined

Sep 14, 2011

By Timothy F. McConachy, Christopher J. Yeats, Ray Binns

Various kinds of sediment-hosted polymetallic sulfide deposit are known on land in ancient marine sequences, many tending to be larger and more valuable than massive sulfide deposits genetically associated with volcanic host rocks. Often such deposits are attributed to subhalative or shallow sub-seafloor precipitation processes, and structural control by faulting is commonly evident. Apart from the famous but anomalous Red Sea metallic oozes and several NE Pacific sites (Middle Valley, Escanaba Trough, Guaymas Basin), however, modern analogs of the sediment-hosted polymetallic sulfide category are lacking. Some deposits hosted by volcaniclastic rocks, such as JADE (Okinawa Trough) and Suzette (Eastern Manus Basin) are strictly sediment-hosted, but their formation is associated with the igneous activity and they are better considered a variant of the more abundant volcanic-associated polymetallic sulfide deposits.

Aug 24, 2006

By Hyun Sub Kim

Subsea mineral deposit exploration aboard the R/V Onnuri was performed along the northern Central Indian Ridge (CIR) between 8°S and 17°S in December 2009 ~ January 2010 (09IR Leg01 and 09IR Leg02) and December 2010~ January 2011 (10IR Leg01, 10IR Leg02, and 10IR Leg03). Final goal of the expedition for the first Korean research cruise on mid ocean ridge system is to define seafloor massive sulfide ore bodies through searching the active hydrothermal vents nearby spreading centers as well as to elucidate the nature of spreading segments of the northern CIR area where no systematic survey have been operated before by mapping and sampling of volcanic rocks. The preliminary result of topographical interpretations of bathymetry clearly display ocean core complex between 10°S and 11°S. The ocean core complex is featured by topographic-high area with corrugated surface. Lineaments of corrugations of the ocean core complex are clearly perpendicular to abyssal hill direction which is triggered by symmetric-normal faults. Ocean core complex are favor for hydrothermal fluid path because of the long-lived faults. In further exploration, more detailed examination, including systematic CTD casting and tows, need to narrow down actual venting site around ocean core complex. Magnetic field survey is able to estimate the location of hydrothermal vents with the properties that high temperature of hydrothermal fluids over Curie-point can cause thermal demagnetization. In magnetization intensity map, most of low magnetization zones are located at the nodal point over the ridge axis and the ocean core complex.

Jan 1, 2011

By Robert Corcoran, Piotr Jasiobedzki, Roy Jakola, Michael Jenkin

Vast mineral resources of copper, zinc, cobalt and gold have been identified off the coast of Papua New Guinea at depths exceeding 2,000 meters. Accessing them in a cost effective manner and without destroying the marine habitat requires overcoming numerous technical and operational challenges. Although there are a number of deep-sea mining operations underway worldwide, the depths encountered are significantly less than will be required to mine these ore deposits. To date, only the oil industry has developed technologies for successfully accessing reserves at depths of 3,000m.

By Paulo Chaves, Márcia Gonçalves, João R. S. Carvalho, Fernando J. A. S. Barriga, Edgar Carrolo, Tiago Luna, Ricardo Rato, Anabela Bento

INTRODUCTION For the last decades, deep-sea marine resources such as seabed massive sulfides (SMS), polymetallic nodules and ferromanganese crusts (Fe-Mn crusts) have received an ever- increasing amount of attention worldwide for their abundance in critical metals and potential commercial value. This interest has mostly been driven by the growing world demand for raw materials, in particular for high- and green-technology applications (e.g., hybrid and electric cars, batteries, photovoltaic solar cells, cell phones, super magnets), as well as by industrialized countries governments other than BRICS states need to secure a more diversified supply of metals, resulting in a new deep ocean exploration boom. Since the oceans and its resources are increasingly seen as indispensable for humans needs and their challenges in the decades to come, this boom increments pressure on marine areas, either in international or within countries economic exclusive zone (EEZ). Since 2002, the International Seabed Authority (ISA) has signed up 29 contracts with several entities and national governments from multiple countries (e.g., Japan, China, Germany, France, Russia, India, Rep. of Korea, UK, Canada, Brazil) for exploration for deep-sea mineral resources in international waters, either for scientific or commercial proposes, which together cover over 1.3 million km2 [1]. In turn, over 300 exploration licenses, covering more than 650,000 km2, have been granted within the EEZ of Pacific countries such as Papua New Guinea, Tonga, Fiji, Solomon Islands and Vanuatu [2, 3]. This number is expected to increase very rapidly, as 77 countries have proposed to the United Nations the extension of their continental shelf in order to extend their EEZ and jurisdiction over potential deep-sea mineral resources [4]. Its estimated that 42% of the potential areas for SMS occurrences, 54% for cobalt-rich Fe-Mn crusts, and 19% for polymetallic nodules lie within the EEZ of coastal countries [5]. In addition, a huge amount of seafloor is yet to be explored and evaluated. Combined, the size of the granted exploration areas represents less than 10% of the overall area thought as most favorable for the occurrence of the 3 types of deep-sea mineral resources above mentioned. This means that today’s assessments on deep-sea mineral resources are only a rough approximation.

Jan 1, 2018

By Michael Goldin, Jonathan Ladner, Thomas Peacock, Nathaniel Johnson, Patrick Haley, Kris van Nijen, Andrew Rzeznik, Pierre Lermusiaux, Matthew Alford, Carlos Munoz-Royo

Surface processing vessels for deep-sea nodule mining operations will produce dewatering plumes that will be released at some depth into the ocean water column. We are studying all aspects of this part of the nodule mining process. First, we have developed analytical and numerical models to determine the effects of highly non-uniform, realistic stratifications on forced, compressible plumes with finite initial size. The classical plume model is developed to take into account the effects of compressibility and thermal conduction through the dewatering pipe. Our results show how small-scale features of a realistic stratification can have a large effect on a plume, and provide a basis for determining at what depth dewatering plumes can be released. These results form the basis for our PLUMEX field experiments, in which we will study the dynamics of dewatering plumes over the course of one week of field tests from the vessel R/V Sally Ride. The field experiments will use a Remotely Operated Vehicle (ROV) and a Phased-Array Doppler Sonar (PADS) system to study the characteristics of the dewatering plumes. The subsequent transport of the material in the dewatering plume will be monitored via shipboard surveys and, potentially, Autonomous Underwater Vehicle (AUV) operations, and these studies will be integrated with near real-time, data assimilating numerical model predictions. The ultimate goal of this project is to develop a field validated, recommend strategy for the release and monitoring of dewatering plumes, to help inform the development of ISA regulations and the planning of industrial operations.

Jan 1, 2017

By Seung-Kyu Son, Michael T. Chandler, Youngtak Ko, Gyuha Hwang

Over the past decade, sea-floor hydrothermal vent fields have been studied by many researchers because of their commercial potential of mineral resources and the origins of Earth’s life. Approximately 300 of these are reported as massive sulfide deposits near the mid-ocean ridge, most of which are located in the Atlantic and Pacific ridges. However, only fourteen deposits have been identified in the Indian mid-ocean ridges. The Central Indian Ridge (CIR) between 8°S and 12°S is composed of three segments with a slow full- spreading rate of 33-37 mm/yr. The hydrothermal activity at the slow-spreading center can be generated along the ridge axis attended by volcanism or along the tectonic features, such as oceanic core complexes (OCCs). OCC is an exposed mantle rocks composed of peridotite and ultramafic rocks uplifted through long-lived detachment fault processes which can also lead to extensive hydrothermal circulation near the slow-spreading center. Therefore, the identification of OCC’s properties will be an important indicator for finding the sea-floor hydrothermal vents. To study hydrothermal activity of the CIR, Korea Institute of Ocean Science and Technology (KIOST) have conducted expeditions using R/V Onnuri over four years (2009-2011, 2017). High-resolution bathymetry and backscatter data was obtained during expeditions using multibeam echo system of EM120 in 2009-2011 and deep-tow side-scan sonar system of IMI-30, which has more higher resolution than EM120, in 2017. In this study, we use these high-quality data for constraining location and size of OCC. We also analyze the geophysical and morphotectonic characteristics of OCC gathering high-resolution bathymetric map and backscatter image.

Jan 1, 2018

By Sven Petersen, Iain J. Stobbs, Bramley J. Murton, Paul A. J. Lusty

"INTRODUCTIONIt is widely thought that seafloor massive sulphide (SMS) deposits, the modern analogue of volcanogenic massive sulphide (VMS) deposits, present a potential global resource for base (Cu, Zn) and precious metals (Au, Ag). In addition, SMS deposits can be enriched in ‘critical metals’ including Se, Te, Tl [1], which are essential for use in the construction of modern and green technologies. Globally over 340 high temperature hydrothermal sites have been identified at a range of ocean spreading centres [2], significant massive sulphide deposit formation has been recorded at 165 of these sites [3].To date only 13 deep sea sulphide deposits have undergone intrusive investigation (drilling or coring) and of these, only 6 sites have published tonnage estimates [2]. Almost all research and drilling of SMS deposits has been focused on active systems, the investigation of the morphology, subsurface structure and mineralogy of hydrothermally extinct seafloor massive sulphide (eSMS) deposits is almost non-existent.As such, little is known about the mechanisms that operate post-SMS formation and which have an impact on the preservation and hence resource value of SMS. Identifying these generic processes and mechanisms, and the extent to which they impact the resource grade, is critical in evaluating the global potential of SMS."

Jan 1, 2017

By S. Rajendran

Gas Hydrates (Methane Hydrates) are solid, ice-like substances composed of water and natural gas. They occur naturally in areas of the world where methane and water combine at appropriate conditions of temperature and pressure and are found in ocean bottom sediments and in some permafrost areas. Besides temperature and pressure, factors like bathymetry, sediment thickness, sedimentation rates, and total organic carbon content (TOC) also control gas hydrate formation in the ocean basins. The stability of gas hydrates depends on the critical combination of high pressure and low temperature (0 - 17 bars, 0 - 25°C), which in turn is dependent on the mix of gases from which the mineral is formed. As the critical parameters can be altered by deposition, erosion, slumping, formation or melting of ice cover, rise and fall of sea level, and sudden temperature changes induced by tectonic activities, current flow, or volcanisms, the gas hydrates tend to be very unstable. The Indian offshore is promising for the occurrence of gas hydrates in a total of about 80,000 km2 area in the bathymetry range of 700 to 3000 m as reported in earlier surveys. A gas hydrate stability zone thickness map was prepared using bathymetry and sea bottom temperatures along the continental margins of India. This map is expected to provide the depth window while searching for Bottom Simulating Reflectors (BSR). The study indicates that a minimum water depth of 750 m is required for the formation of gas hydrates, above which the chances for gas hydrate occurrence appear minimal despite other favorable conditions like organic-rich sediments, etc. Single-channel seismic analog records (Gupta et al., 1998) indicate that the Western Continental Margin of India (WCMI) offers a greater promise for gas hydrate occurrences, particularly with regard to the number of BSRs traced on the analog records as compared to earlier surveys.

Jan 1, 2005

By Akira Usui, James R. Hein, Rachel Dunham

Ferromanganese crusts are found on most hard-rock substrates in the deep ocean (800-3,000 m). Their distributions on seamounts are complex and controlled by a wide-variety of factors including seamount morphology, current patterns, mass wasting, substrate rock type and age, subsidence history, and others. However, the development of this potential resource ultimately depends on this distribution, as well as on the small-scale topography, grade, and tonnage. The parameters that will ultimately be used to define a mine site are unknown, but reasonable assumptions based on 25 years of data collection can be used to bracket likely permissive characteristics.

By S. Kim Juniper

The discovery of chemosynthetic-based ecosystems at hydrothermal vents in the deep ocean was arguably one of the most important findings in biological science in the latter half of the 20th century. More than 100 vent fields have been documented along the 60,000 km global mid-ocean ridge system. Over 500 new animal species, over 80% of which are endemic to the vents, have been described from this environment. Unusual, highly evolved symbioses between invertebrates and chemolithautotrophic bacteria are common at vents, producing concentrations of biomass that rival the most productive ecosystems on Earth. Hydrothermal vents ecosystems, because of their very limited area and the presence of endemic species, are highly vulnerable to human disturbance. Mining for polymetallic sulphide deposits poses the greatest future physical threat to hydrothermal vents and their biological communities. However, there is more immediate concern about the impact of concentrated scientific research activities. Some sites have been revisited by several research expeditions per year for more than a decade. As vent sites become the focus of intensive, long-term research, oversight organizations are discussing mitigative measures to avoid significant loss of habitat or oversampling of populations. Canada recently became the first national jurisdiction to set aside a hydrothermal vent site as a Marine Protected Area.

Jan 1, 2001

By Samantha Smith

Nautilus Minerals (Nautilus) is following the lead of the petroleum industry as it strives to tap vast offshore resources. Planning is well underway for the Solwara 1 Project in the Bismarck Sea, Papua New Guinea (PNG) to recover high-grade seafloor massive sulphide deposits in 1600 m water depth. The deposit contains an average copper grade >10 times higher than a typical land-based porphyry copper mine. The high grades combined with a relatively small amount of overburden ensure the Solwara 1 Project will have a significantly smaller physical footprint than its land-based counterparts. Offshore minerals production also has the advantage of minimal social disturbance. Nautilus is dedicated to setting a high environmental and social responsibility standard. Nautilus recognises the importance of transparent and inclusive stakeholder engagement and has taken a proactive approach to involve as many key stakeholders as possible. One of the first steps in the permitting process in PNG is the preparation of the Environmental Inception Report, which describes the project, its envisaged impacts and the proposed studies for the Environmental Impact Assessment (EIA). Local (PNG-based) and international environmental scientists, anthropologists, NGOs and other experts were involved in the definition of studies conducted for the Solwara 1 EIA and a team of world-leading experts was involved with carrying out the studies, culminating in the preparation of the Environmental Impact Statement (EIS). To ensure transparency, collaborating researchers are free to publish their findings. Following its submission, the EIS was made available for public review and public hearings were held at several locations. The EIS has also undergone a rigorous independent review by PNG government-engaged consultants. Outside the permitting process, Nautilus works alongside government officials to carry out ongoing community consultations. Information dissemination and feedback acquisition has also occurred through the Nautilus website and attendance at a number of international conferences, workshops, and meetings. This paper will outline the leading edge approach Nautilus has taken in completing the environmental impact statement for the world?s first deep seafloor copper-gold mine. In addition, this paper will review the permitting process and the government and stakeholder engagement undertaken as part of Nautilus? desire to ?do it right? in this exciting new industry.

Jan 1, 2010

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'W to 2 40'W, and between the shoreline and approximately the continental shelf edge north of 4 30'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 Irina Dobretsova, Anna Sukhanova, Anatoly Kondratenko, Svetlana Babaeva, Sergey Andreev

"With the acceptance of an application and a signed contract for prospecting deep-sea sulfides (2012) between the Russian Federation and the ISA, at present it is particularly important to assess the quality of oceanic sulfide minerals and to reliably estimate their resources.Some procedures of geochemical classification (chemical analyses, mineral composition of SMS) and calculations (density of ore, density of the mineral part of the ore, porosity and moisture contents) were used for estimation of mineral resources potential.The key characteristics for estimating the predicted resources of hydrothermal ore fields are the metal contents and the density of wet and dry sulfide ores. However, in the future it is impossible to provide an estimate of the predicted resources without taking into account the following important factors:- the quantitative ratio of main sulfide minerals;- proportion of non-metallic components (opal, quartz, talc);- the replacement of primary minerals by copper sulfides;- texture-structural features of sulfide ores.The offered mineral classification of the SMS is based on the prevalence of minerals in the ores and partly on their composition. The main ore-forming minerals of SMS are pyrite, chalcopyrite and sphalerite. Sulfide mineralization is accompanied by the presence of nonmetallic minerals, where quartz and opal prevail, and where we also meet aragonite, talcochlorite and anhydrite."

Jan 1, 2017

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