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By D. J. Scarratt

Fisheries make a significant regional contribution to the economy of Canada. In the Atlantic Region, over 70 thousand workers depend on the primary or secondary fishing industry. Fisheries are vulnerable to pre-emption of space by other marine industries and to contamination by chemical discharges. Markets may be affected even by the threat that products may be tainted. Fish may be killed by drags and dredges, and their physiology and behaviour affected by suspended sediments are stirred up by mechanical devices. Virtually no evidence exists of adverse impacts £ran ocean mining on fisheries, but projections from other marine activities such as fishing itself, dredging and other marine discharges give reason for caution. Department of Fisheries and Oceans policy calls for review of ocean mining proposals to ensure adequate protection of fish stocks, fishing activities and fish habitat, and compensation for losses attributable to any industrial project. Adverse impacts can be minimized by careful attention to details of location, technology and timing, and to close co-operation and information exchange between industry and the regulatory agencies.

Jan 1, 1985

By Richard Mills

Autonomous Underwater Vehicles (AUVs) are proven technologies used across market segments for survey, exploration and environmental monitoring tasks. When coupled with other autonomous platforms or sensor packages AUVs become part of an holistic system approach to exploration and environmental assessment and monitoring. Recent developments have seen AUVs deployed remotely with instantaneous access to data via the cloud. Our goal is to deliver the capabilities of each of these elements and present a cohesive data set with automated processing tools over a cloud based interface. nmanned Technology AUVs The HUGIN AUV System is the most commercially successful AUV ever built. Operated as a single vehicle, or as part of a swarm, HUGIN’s area coverage rate is unrivalled. Equipped with a comprehensive sensor package including Kongsberg’s synthetic aperture sonar, it collects a data set. Some of these data are processed in-mission to enable operators to readily access it when the vehicle is recovered. HUGIN is well suited to mining survey and exploration. Capable of reaching 6000 metre depths and conducting missions greater than 60 hours, HUGIN collects seabed sonar imagery, sub-bottom profiles, laser and camera images plus environmental data, with sensors running concurrently.

Jan 1, 2018

By M. Geoghegan

Under the provisions of the U.N. Law of the Sea Convention Ireland is likely to have mineral rights to an area of continental shelf some six times its present land area. Apart from the major potential hydrocarbon basins which are currently the focus of active commercial exploration, little is known about the mineral resources of this vast area. In recent years a variety of mineral resources however have been identified from the coastal region. These include Sand and Gravel aggregates, Calcaraeous Algae (Lithothamnion), Heavy Mineral Sands and Coal deposits. The potential also exists in the coastal zone for buried placer deposits and base metal deposits. Several million cubic metres of gravel and hundreds of millions of cubic metres of sand have been identified by the Geological Survey of Irelands (G.S.I) Marine Unit off the east coast. The greater part of these deposits lies within the 10 metre depth contour and are easily recoverable. Irish aggregate needs at present are well supplied by onshore Pleistocene glacial deposits. Commercial interest in offshore deposits is in supplying coastal areas which are locally poor in aggregate and major coastal construction works. The possibility of supplying the large British and Continental European Market nearby also exists.

Jan 1, 1988

By W. C. Burnett

The land phosphate deposits of the U.S. southeastern coastal plain have long been a major factor in the world trade of phosphate rock (Fig. 1). As recently as 1979, deposits of North Carolina and Florida alone accounted for about 33 percent of the entire world's phosphate exports. This situation is changing, however. World production increased by ~9 %, yet the U.S. share was down to ~28% in 1984. A complex interaction of economic and political factors combined with increasing costs of raw materials, production, and transportation have led to this systematic erosion of the U.S. market share. Changing land-use patterns within the southeast, environmental pressures, exhaustion of shallow high-grade resources in Central Florida, and the increased pressure from expanding low-cost production in other countries throughout the world account for much of the present difficulty in the U.S. phosphate industry. Considering this depressed environment -- what are the prospects for development of offshore resources? A summary of new research on offshore phosphorite within the U.S. Exclusive Economic. Zone (EEZ), as well as an attempt to place possible development of these resources within the current economic setting, is the purpose of this presentation. We will emphasize work in progress on a major offshore deposit along the U.S. Atlantic Margin as well as new research on Pacific Ocean occurrences of phosphorite on seamounts and insular slopes within U.S. waters.

Jan 1, 1986

By Tetsuo Yamazaki

Natural methane hydrate has been scientifically studied as a carbon reservoir globally. However, in Japan, the potential for energy resource has been industrially highlighted. There is less domestic oil and natural gas resources in Japan, but many potential deposition areas for methane hydrate in ocean around Japan are the reasons. Less CO2 discharge from methane compared with coal, oil and conventional natural gas when the same calorie value we get is considered as the advantage for energy resource. However, because methane hydrate distributes in shallower sediment layer in ocean floor, accidental leakage of methane may occur while we utilize methane hydrate. Methane itself has 21-times impact on the greenhouse effect, if it reaches the atmosphere. Therefore, it is necessary to estimate the behavior in the environment after the leakage, if we want to use methane hydrate as energy resource. The mass balance after leakage of methane on seafloor and in water column is numerically studied through the analyses of methane emissions from natural cold seepages and hydrothermal activities in this research. The outline structure of mass balance ecosystem model shown in Fig. 1 is introduced. A numerical early diagenetic model CANDI (Carbon And Nutrient Diagenesis) developed by Boudreau (1996) for simulating the biogeochemical processes such as organic matter, oxidant, nutrient, bi-product, and pH diagenesis in aquatic surface sediments and C. CANDI improved by Luff and Wallmann (2003) for describing the formation process of calcium carbonates in CANDI are used as bases of the ecosystem modeling in surface sediment layer around seafloor methane emission. Two functions such as methane bubble dissolution and bacterial methane oxidation in water column are added to an existing physical plume dispersion model by Doi et al. (1999).

Jan 1, 2005

By Kira Mizell, James Hein

"INTRODUCTIONThe majority of studies on the genesis of ferromanganese crusts focus on the adsorption and accumulation of metals, and therefore cations, especially those of economic interest. From these studies, a first-order electrochemical model has been proposed based on the zero point of charge of the manganese and iron oxides at typical seawater pH, which assumes that positively charged ions will bind to the negatively charged manganese oxide phase and neutral and negatively charged ions will bind to the slightly positively charged iron oxide phase (e.g. Koschinsky and Halbach,1995; Hein et al., 2013). While the theory behind this model is sound, and it has been consistent for many elements, other elements may not follow the model (Koschinsky and Hein, 2003), and thus requires additional investigation and validation. As a new approach to understanding element accumulation in ferromanganese crusts and to test the proposed electrochemical model, this study investigates the surface chemistry of the halogens, which occur as negatively charged ions in seawater and have high and consistent concentrations in seawater.ResultsBulk Halogen ConcentrationsTo determine the distribution of halogens in ferromanganese crusts, an initial dataset of 24 FeMn crusts (24 bulk and 19 layer samples) from throughout the global ocean, including the Arctic and the Southern Oceans, has been analyzed for chlorine and fluorine content using ion-selective electrode. Although both Cl and F are conservative in seawater, their content in crusts shows striking variability (Cl: 326 - 13310 ppm; F: 146 – 1048 ppm for non-phosphatized crusts) and has no obvious geographic relationship to ocean basin and no correlation with water depth, latitude, or longitude. We plan to have bromine concentration data to present at the time of this conference."

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 David Heydon

NAUTILUS MINERALS is a leader in the commercial exploration for and evaluation of seafloor massive sulfide (?SMS?) deposits. Nautilus has exploration licences covering 15,000 sq km of seafloor in Papua New Guinea and is evaluating other areas in the Western Pacific. The Nautilus Western Pacific Gold-Copper project is an interesting case study of the interaction of the disciplines of Science, Engineering and Environmental Science to solve and attend to the challenges of a project without precedence. The Science books of geology and marine biology with respect to seafloor massive sulfides are still being written or at best are thin volumes with recognition still we know very little at this time. Science?s early discoveries and study of these mineral processes on the seafloor provided invaluable data from which to develop an exploration strategy and the genesis of Nautilus itself. The Engineering required for development of such deposits is a combination of yet to be tested ?theory and engineering principles? and adaptation of best practice from other fields such as oil/gas and telecommunication cable laying. The Environmental guidelines for exploring these deposits, let alone mining them, is at the moment still being debated by a panel of experts chosen by the International Seabed Authority.

Jan 1, 2005

By T. Schoening

The exploration of the seafloor regarding the abundances of poly-metallic nodules has received growing attention recently. Image-based exploration using cameraequipped deep-sea observation systems has been introduced successfully to increase spatial resolution in the exploration process but the evaluation and interpretation of the huge amount of image data creates a serious bottleneck. In this paper we present a new software solution to the problem of automatic detection and segmentation of poly-metallic nodules in underwater images, which is not only accurate but so fast that real time image analysis is definitely in reach. Thus, an application on an AUV (Autonomous Underwater Vehicle) seems possible in the near future.

Sep 14, 2011

By Fernando J. A. S. Barriga

"Recent concerns over the availability of many mineral raw materials, and newly available technological developments, produced renewed interest in deep-sea mining. However, environmental concerns, with variable degrees of justification, are raising opposition to the concept. The forecast for the behavior of consumption versus availability of many raw materials, nearly all critical metals, arguably show that consumption will grow much faster than resource discovery onshore. Finding new sources of raw materials seems inescapable. The deep seafloor stands out as the only likely candidate.Sea Floor Mining and the EcosystemMarine mining has already started, decades ago, for diamonds, currently up to depths near 400m. Although the industry recognizes there is a footprint, it considers the footprint quite minor, because the area mined is small: in Namibia, where offshore diamond mining is now 70% of the country’s total, only 3% of the concession of 3,700 sq miles (9600km2) have been mined. As plans to mine deep-sea massive sulphide deposits and polymetallic nodules progress, the environmental concerns grow. Some of these concerns are as follows:?The deep-sea ecosystems are composed of long-lived species, with low rates of reproduction. The environment may not recover from mining on a human time scale;"

Jan 1, 2017

By Stanley R. Riggs

Onslow Bay is a broad, shallow, high-energy shelf system bounded by the Cape Lookout and Frying Pan shoals. It is generally a sediment-starved shelf system dominated by hardbottoms with a scattered and discontinuous veneer of mobile Holocene sediments. Phosphate-rich beds of the Miocene Pungo River Formation crop out in a belt 150 km long and up to 50 km wide across the continental shelf in Onslow Bay, North Carolina. Previous research has demonstrated that a few of these beds contain vast quantities of potentially economic phosphate resources that occur in the surface and shallow subsurface sediments. Onslow Bay contains five phosphate-bearing beds predicted to include up to 20.7 billion tons of in-place phosphate concentrate with total sediment grades ranging up to 22.9% P2O5 and adjusted average concentrate grades of 29.8% P2O5. These phosphates are lithologically and chemically similar to phosphates currently being mined in the nearby Aurora phosphate district in North Carolina. Various lithologies of the Pungo River Formation and associated rock units of Oligocene and Quaternary age crop out on the sea floor to form extensive hardbottom habitats that dominate almost 100% of Onslow Bay. A large proportion of these hardbottoms appear to be sea floor deserts, whereas others are virtual oases with rich associations of benthic organisms. These important differences in benthic community structure appear to be greatly influenced by one or more of the following variables: 1) geologic framework (geologic formation, hardbottom composition, morphology, and spatial orientation relative to dominant currents and waves), 2) texture, movement, and accumulation of surface sediments, and 3) flow rates and chemical composition of discharged submarine groundwater.

Jan 1, 1992

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 can combine at appropriate conditions of temperature and pressure and are found in the 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 sea. The stability of gas hydrates depends on the critical high pressure ? low temperature combination (0 - 17 bars, 0 - 25°C), which in turn dependent on the mix of gases from which the mineral is formed. As the critical parameters can be altered by deposition, erosion or slumping of sediments, formation or melting of ice cover, rise and fall of sea level and sudden temperature changes induced by tectonic activities, current flows or volcanisms, the gas hydrates tend to be very unstable. The Indian offshore is promising with 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 the 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 the ?Bottom Simulating Reflectors? (BSR). The study indicates that a minimum water depth of 750 m is required for the formation of gas hydrates, and above which the chances for gas hydrates occurrences appear minimal despite other favourable conditions like presence of sediment rich organic content etc. Single channel seismic analog records (Gupta et al., 1998) suggests that Western Continental Margin of India (WCMI) offers greater promise with to gas hydrate occurrences, particularly with regard to the number of BSRs traced on the analog records as compared to the earlier surveys.

Jan 1, 2002

By Wiebe Boomsma

This is a framework study financed by the Maritime Innovation Programme of The Netherlands and several institutions actively involved in the research of the environmental impact of deep sea mining; IHC Mining, MTI Holland, Delft University of Technology, NIOZ, IMARES, Boskalis Westminster, AllSeas and TNO. For this framework study the following mining activities have been identified to be relevant to assess the ecological impact of a deep sea mining operation: a) excavation, b) tailings return, c) vertical transport, d) vessel operations, e) ore transport and f) general operations. For this paper, only one mining activity has been selected as an example for the assessment of ecological effects. This is one of the main activities introduced by the new technology envisaged for developing deep sea mining: tailings return.

Sep 14, 2011

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

This paper discusses operational environmental threshold levels for exploitation of mineral resources in the deep sea. Such criteria are needed to be able to monitor and control deep sea mining with respect to the stringent environmental requirements that are needed. It is recommended to use existing environmental threshold levels for comparable underwater activities. Fields of application are mainly but not exclusively seabed mining operation activities under the governance of the International Seabed Authority (ISA). The threshold levels and limits mentioned in this paper are proposed recommendations based on other activities than seabed mining but are a proven and accepted approach in other maritime industry activities. An example of such other activities with proven and accepted environmental threshold levels are Oil & Gas exploitation activities in the sea. Background The first exploitation of mineral resources in international waters is coming closer. Presently regulations for exploitation for mineral resources in the Area are being developed by the International Seabed Authority (ISA). The ISA regulations will contain the framework related to environmental monitoring of exploitation. However, the regulations will not contain operational environmental threshold levels for the Contractor.

Jan 1, 2018

By Igor E. Mikhaltsev

The goal of investigation of the midwaters and of the bottom of the world - ocean versus technological possibilities. Manned vehicles and maximum depth decision. The methods of solving of the problem. The science and technology alloy. Mutual venture of Academy of Sciences of the USSR and, Rauma-Repola Oy of Finland. MIR-1 and MIR-2 - as twins. No reasons of copy "Sea Cliff" and "Nautilus". Six landmarks of specificity of "MIR"-type submersibles. The manned spheres and three ballast spheres are made of maraging steel; the electric power resource (100 kwh) and maximum underwater speed (5 knots) is two times more than of the analogous vehicles while the batteries are of NiFe type; the MIR submersibles have the seawater ballast (and trim) system which means practically unlimited vertical manoeuvrability ; and the weight in air is equal to "Nautilus" - 18,6 tons (in case of equal energy resource the weight of MIR-1 or MIR-2 would be 17 tons). Some remarks on standard life support (248 man-hours) safety systems and specificity of launch & recovery system.

Jan 1, 1988

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

This paper describes operational environmental threshold levels for exploitation of mineral resources in the deep sea. Such criteria are needed to be able to monitor and control deep sea mining with respect to the stringent environmental requirements that are needed. It is recommended to use existing environmental threshold levels for comparable activities where such are existing. Fields of application are mainly but not exclusively seabed mining operation activities under the governance of the International Seabed Authority (ISA). The threshold levels and limits mentioned in this paper are proposed recommendations based on other activities than seabed mining but are a proven and accepted approach in other maritime industry activities. An example of such other activities with proven and accepted environmental threshold levels are Oil & Gas exploitation activities in the sea. Background The first exploitation of mineral resources is coming closer. At the moment regulations for exploitation for mineral resources in the Area are being developed by the International Seabed Authority (ISA). The ISA regulations will contain the framework related to environmental monitoring of exploitation. However, the regulations will not contain operational environmental threshold levels for the Contractor.

Jan 1, 2018

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 Charles L. Morgan

The Minerals Management Service of the U.S. Department of the Interior and the State of Hawaii Department of Planning and Economic Development are investigating the cobalt-rich ferromanganese oxide crust deposits found within the Exclusive Economic Zones (EEZ) of the Hawaiian Islands and Johnston Atoll. The objective of this investigation is to complete a preliminary resource assessment and an Environmental Impact Statement for potential leasing of mineral rights to these crusts. The results of this effort will be summarized and published in a Draft Environmental Impact Statement in March 1986. Three oceanographic cruises to deposit sites in the Hawaiian Islands EEZ were conducted by the University of Hawaii in 1984. As a result, data and sample analysis yielded the following resource estimates (in thousand tonnes): (1) total crusts - 378,500; (2) cobalt - 2,500; (3) manganese - 76,200; (4) iron - 59,700; and (5) nickel - 1,400. These estimates do not include key factors such as deposit continuity, recoverability, and environmental sensitivity. A preliminary attempt to quantify some of these factors for one particular deposit is in progress and will consist of detailed field studies followed by laboratory analysis. Similar evaluations of the Johnston Island EEZ have also begun and are based upon field work conducted by West German researchers and the U.S. Geological Survey. The Johnston Island EEZ appears to have crust resources about as large as those contained in the entire Hawaiian EEZ.

Jan 1, 1985

By Hunsoo Choi, Sang-Mo Koh

Manganese nodule, the aggregate of fine grained manganese oxide minerals, is very brittle and fragile. In exploitation of manganese nodule, manganese nodules are easily broken into small pieces or powder during collecting and lifting from the sea floor. The broken manganese nodule under few millimeters and bottom sediment pumped up with manganese nodule affect to the lifting process. In this study, we tried to understand the physical properties of the powdered manganese nodule and bottom sediment, and to know the effect which may be rised to the actual mining of manganese nodules.

By J. W. Jamieson

"The future of the marine mining industry is tied to the resource potential of the seafloor. Everything from economic feasibility, policy decisions and environmental impact assessments to extraction techniques and mining tool design rely on an understanding of the size, composition, and distribution of the deposits. Development and regulatory decisions must ultimately be tied to not only the grade and tonnage estimates of individual deposits or groups of deposits, but also an understanding of the uncertainty of these estimates. Here, we will discuss how seafloor massive sulfide (SMS) deposit grades and tonnages are evaluated, and the sources of the uncertainties associated with these values.TONNAGE UNCERTAINTYFirst-order tonnage (size) estimates for SMS deposits are primarily determined from calculating the volumes of material that occurs as positive bathymetric features on the seafloor. The extent of sulfide mineralization on the seafloor can be determined either from visual surveys (camera-tow, remotely-operated vehicle (ROV), or human-occupied submersible surveys) or from volume calculations of bathymetric features identified from digital elevation models of the seafloor, or a combination of both methods. For bathymetric models to be used to identify deposits in the absence of visual groundtruthing, data resolution of 1 m or less is generally required to confidently identify a feature as being hydrothermal in origin (as opposed to a volcanic or tectonic feature), and therefore near-bottom multibeam data acquisition (e.g., using autonomous underwater vehicle (AUVs) or remotely operated vehicles (ROVs) is required (Fig. 1). Specific characteristics of bathymetric features, such as shape, slope angles and surface roughness can be used to identify features of hydrothermal origin (Fig. 1). However, so far, bathymetric features mapped at a resolution of ~1 m cannot be relied upon to unambiguously distinguish a sulfide mound, and the additional use of multiple AUVmounted sensors, such as magnetometers, which can be used to detect hydrothermal upflow zones, or self-potential sensors, which detect electrical fields related to the oxidation of sulfide minerals, can increase the confidence that a bathymetric feature is indeed a sulfide body, without the need for expensive and time-consuming visual surveys (c.f. Petersen et al., this volume)."

Jan 1, 2017