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By R. Moss

Gold and silver are important byproducts of mining volcanogenic massive sulfide (VMS) deposits. Both metals occur in VMS deposits ranging in age from the Archean to the currently forming massive sulfides found on the ocean floor. The gold- and silver-rich deposits on the modern seafloor are geographically diverse and occur in several different tectonic settings (Figure 1a,b) including seamounts (e.g. Franklin Seamount, Papua New Guinea), unsedimented mid ocean ridges (e.g. TAG and Snakepit, Mid Atlantic Ridge), sedimented mid ocean ridges (e.g. Escanaba Trough) and back-arc basins (e.g. Manus Basin, Papua New Guinea). Interestingly, the most gold- and silver-rich deposits are found in the back-arc basins of the western Pacific, commonly associated with differentiated volcanic rocks such as the dacite-rhyodacite suite at PACMANUS in the eastern Manus Basin. This suggests that different, or more efficient, mechanisms are concentrating precious metals in such back-arc settings. Such mechanisms may include leaching of volcanics enriched in gold (e.g. rifted arc crust) or silver (e.g. continental crust) and/or the introduction of gold into a hydrothermal system by a magmatic fluid. The gold content of modern seafloor precipitates varies from a few ppb up to a high of 54 ppm reported from eastern Manus Basin (1). The Jade Deposit in the Okinawa Trough has the highest silver contents with values up to 1.1% (2). Both gold and silver are preferentially concentrated in late-stage, low temperature precipitates with zinc-rich assemblages being favoured in most cases. Gold is found as relatively pure native gold and sub-microscopic inclusions in gold-rich deposits, but occurs predominantly as sub-microscopic inclusions and possibly as solid solution in the gold-poor deposits (3). Silver occurs as rare silver minerals such as acanthite and native silver in the silver rich Jade deposit (2), but more commonly in the silver-containing minerals tetrahedrite and tennantite, as is the case in the PACMANUS deposit. Tetrahedrite is also known to be an important host of silver in ancient VMS deposits (4). More abundant sulfides can contribute significantly to the silver balance. In the silver-poor deposits at 21 N East Pacific Rise, silver is contained entirely within chalcopyrite, isocubanite, pyrite, marcasite, sphalerite/wurtzite and galena. In this case silver may be present as sub-microscopic inclusions of silver minerals or in solid solution.

Jan 1, 2011

By Walter L. O?Niell

The Continental Shelf Division of the Marine Minerals Technology Center has recently completed field tests of the percussion- waterlift drill and the vibracore/vibralift convertible drill. The two systems have been modified from existing drills to increase their effectiveness and flexibility for nearshore minerals exploration. Originally the percussion-waterlift drill was designed for iand based operations, but it has been modified for use in protected shallow water areas. This drill is easily maintained, inexpensive to construct and operate, and is able to accurately recover representative samples from a variety of sedimentary deposits. Sampling is accomplished using either a reverse circulation method for the recovery of a slurry of sediment cuttings and water or employing a thin walled "Shelby tube" to core zones of interest. The vibracore/vibralift convertible drill is a modification of the remote placer drill (RPD). By combining these drills into one convertible system, it is possible to recover continuous cores of unconsolidated fine-grained sediments (vibracore), a slurry of clay to gravel size sediments over 1.0 meter intervals (vibralift), and to sample sedimentary material in environments where indurated

Jan 1, 1991

By Benjamin W. Haynes

The Federal government has a lengthy history in supporting and conducting research in the ocean mining and minerals field. The Federal effort has been and is currently focused primarily in four agencies: the National Oceanic and Atmospheric Administration (NOAA) within the Department of Commerce, and the Geological Survey (USGS), the Bureau of Mines (BuMines), and more recently the Minerals Management Service (MMS) within the Department of the Interior. While NOAA and the USGS have played dominant roles in mapping and geologic studies, and the MMS has recently provided funding for several task force studies within the Exclusive Economic Zone (EEZ) , the Bureau of Mines has conducted research in mining technology, minerals processing, resource definition, and economic evaluation of minerals from the seabed for over 20 years. These studies have yielded considerable minerals information regarding manganese nodules and crusts, placers, mineral sands, phosphorites, and sulfides. This paper reviews the past achievements in ocean mining and minerals programs starting in the late 1960's, describes current research and information efforts, and presents an outlook for Bureau of Mines research and information gathering efforts. Specific topics

Jan 1, 1989

By Robert M. Owen

The reconstruction of ocean history has been a major focus of marine research over the past decade. A significant outcome of these investigations is the recognition that certain types of marine mineral deposits are linked to regional to global scale changes in ocean composition and climate conditions. Manganese-bearing deposits are of particular interest in this regard because changes in their occurrence, distribution and/or composition are responsive to both biochemical and geological factors. Analyses of such deposits whose formation spans critical age/epoch boundaries thus provide clues concerning the interplay of different process during anomalous periods in Earth history. Recent studies demonstrating this deposit - event - process relationship include: (1) Changes in the bulk chemical composition of ferromanganese crusts during the Late Miocene-Early-Pliocene (-7-3 Ma) that coincide with a period of enhanced biological productivity in the eastern equatorial Pacific upwelling zone; (2) The formation of large statiform manganese deposits at the Cenornanian- Turonian Boundary (-92 Ma) in association with widespread oceanic anoxia; and (3) Increased deposition of hydrothermal precipitates caused by tectonic reorganizations at the Paleocene - Eocene boundary (-55 Ma) that resulted in global-scale changes in atmospheric and oceanic circulation and climate.

Jan 1, 1995

By Tetsuo Yamazaki

Natural methane hydrate has been scientifically studied as a global carbon reservoir. However, in Japan, it?s potential as an energy resource has been industrially highlighted, because there are few domestic oil and natural gas resources in Japan, but many potential deposition areas for methane hydrate in the sea around Japan. Less CO2 discharge from methane compared with coal, oil and conventional natural gas for the same calorie value is considered an advantage for its use as an energy resource. Because methane hydrate is distributed at shallow depth in sediments on the ocean floor, accidental leakage of methane may occur while we utilize methane hydrate. Methane itself has a considerable impact on the greenhouse effect, if it reaches the atmosphere. Therefore, it is necessary to estimate its behavior in the environment after leakage if we want to use methane hydrate as energy resource. The mass balance after leakage of methane on the seafloor and in the water column can be studied through the analyses of natural cold seepages and hydrothermal activity.

Jan 1, 2004

Ancient volcanogenic Cu-Zn-Pb-Ag-Au massive sulfide ores commonly have associated with them along strike and in the immediate hanging wall a distinctive sediment that is thin, usually cherty and metal enriched, and generally referred to as an "exhalite horizon" or "tuffaceous exhalite". Typical examplks include the 13 Ma tetsusekiei of the Kuroko deposits of Japan (Kalogeropoulos and Scott, 1983, Econ. Geol.) and the 2700 Ma contact tuffs of Noranda, Canada (Kalogeropoulos and Scott, 1989, Can. J. Earth Sci.) and Key Tuffite of Mattagami, Canada (Liaghat and McLean, 1992, Explor. Min. Geol.). Attempts to use trace element distributions as lithogeochemical guides to ore have been largely unsuccessful. Exhalites have been considered to be the products of seafloor hydrothermal activity that is peripheral to the main ore-producing vents. However, large actively-forming polyrnetallic sulfide deposits at the Explorer mid-ocean basalt spreading ridge (1 850 m depth) in the NE Pacific and the eastern Manus back-arc dacitic spreading center (1650 m depth) in the western Pacific have demonstrated that the exhalite horizons are more likely produced by fallout of particulates from the main hydrothermal plume. In a typical hydrothermal plume, grains of >27 µm represent up to 97% of the mass (although only 2% of the population) of the particulates and are calculated by Stokes equations to fall from the plume to the seafloor within a few krn of their source. The particles are primarily composed of anhydrite, barite, amorphous silica, iron oxyhydroxides and metal sulfides and oxides. Plumes are subject to bottom currents which push them in preferred directions, just like smoke plumes in the atmosphere are subject to the vagaries of wind direction. Bottom currents in the deep ocean can be 50 m/min or

Jan 1, 1993

By Tina Schneider

Scientists show that polymetallic nodules and massive sulfides from deep sea mining contain valuable metals. These metals have the potential to overcome future shortages of supply. Hence, companies, government agencies and industrial associations increasingly evaluate deep sea mining as a promising supplement of land mining. Technologies to extract, exploit, transport and smelt polymetallic nodules and massive sulfides industrially are still in conceptual stage and not sufficiently advanced for operation. According to the International Seabed Authority, large scale exploitation would require a successful pilot mining test in order to demonstrate e.g. the technological feasibility but also the conservation of environmental systems services. At the same time, NGO´s and a some scientists point out that large scale extraction of polymetallic nodules and massive sulfides could disturb the habitat of benthic organisms, with unknown long-term effects. Aside from the direct impacts of mining, indirect consequences about leakage are likely. In the oral presentation I will show how companies, government agencies, scientists and association/interest groups perceive and assess economical/technological, social and environmental risks and opportunities of deep sea mining. In order to analyze the perspectives of each stakeholder group on deep sea mining, we conducted 15 interviews with four stakeholder groups and a large scale survey (n = 500, return rate = 13 %) in Germany. We used the concept of sustainability with its economical/technological, ecological and social dimensions for the interpretation of the results. The empirical research shows the following core results:

Jan 1, 2018

By Tobias Hens, Andrew Frierdich, Barbara Etschmann, Joël Brugger, Barrie Bolton

"Advancing our knowledge about trace metal distribution and abundance provides insight into formation, alteration, and trace element enrichment processes of ferromanganese nodules and crusts. A fundamental understanding of these mechanisms, in turn, has implications for the selective recovery of critical metals and the development of sustainable hydrometallurgical techniques. Synchrotron-based X-ray Fluorescence (SXRF) is a powerful, state-of-the-art analytical tool that can examine geochemical features of Fe-Mn nodules and crusts, such as abundance and distribution of trace elements, in an integrated and efficient manner. By correlating trace element composition and Mn oxidation states in these highly complex samples, it can be determined whether these parameters are related to the Mn oxide mineralogy (vacancy content of crystal lattice) and chemistry.In this study, eleven Fe-Mn nodule and crust samples from three circum-Australian locations – the South Tasman Rise, Lord Howe Rise, and Coral Sea – were analyzed at the Australian Synchrotron, Victoria, Australia. Micrometer-scale spatial resolution of geochemical features, such as concentric growth structures and element distribution, was achieved with high sensitivity (Fig. 1). For instance, Ni could be detected at 10's of ppm to 1 wt% levels. Information on other redox-sensitive trace elements, which are present at 10-1000 ppm levels (e.g., Cu, Co, Ti), were gained by means of fully quantitative elemental composition maps."

Jan 1, 2017

By Tobias Hens, Andrew Frierdich, Joël Brugger

The rapid advancement of green technologies in recent years is closely tied to an ever- increasing demand for raw materials. Innovative forms of zero-emission transportation and sustainable power generation will require a variety of traditional metals such as Ni and Co, but also many non-traditional metals (e.g., REY). Many of these elements are known to be highly enriched in deep-sea ferromanganese (Fe-Mn) nodules and crusts. However, unlocking these metals from their deposits through metal processing is – aside from deposit exploration and production – expected to be a critical component that will affect the overall economics of the marine mining value chain. Hence, research and development of tailored metal processing solutions which can target specific metals of interest in Fe-Mn nodules and crusts, is required. Dynamic mineral recrystallization (DMR) of Fe-Mn oxide phases is a geochemical process that may have notable potential for hydrometallurgical applications. We have recently demonstrated that Ni can effectively be cycled between deep-sea Fe-Mn nodules and crusts and solutions through dynamic mineral recrystallization. DMR occurs in nature as abiotic background process during biogeochemical Mn cycling when dissolved Mn(II) is in direct contact with Mn oxides. Trace metals which are incorporated in the Mn host phases, are cycled between solid phase and solution via coupled dissolution (trace metal release) – reprecipitation (trace metal incorporation) mechanisms.

Jan 1, 2018

By Valery M. Yubko

During the last ten years seven applications for nodule-bearing areas of the World Ocean Floor International Region (IR) have been made by national companies of Russia (Yuzhmorgeologiya), France (IFREMER/AFERNOD), Japan (DORD), India (The State Department of Sea Resources Development), China (COMRA), Korea (KORDI) and the Interokeanmetal Joint Organization (IOM) of some East European countries and have been registered by the Preparatory Commission of the United Nations International Seabed Authority (ISA). Besides these groups registered within Resolution 11 of the Final Act of the III United Nations Conference on the Law of the Sea there are four international consortia registered in the USA [Kennecott (KCON), Ocean Mining Associates (DMA), Ocean Management Incorporated (OMI), and Ocean Minerals Company (OMCO)], which have interest in areas in the IR and can be considered as potential applicants. All registered areas (with the exception of the Indian Ocean) including the areas of potential applicants and also 6 areas, reserved for the ISA are located in the Clarion-Clipperton Zone of the Pacific Ocean. If within each area not less than one deposit of polymetallic nodule-bearing ores can be discovered, then, the total number of such deposits, for the present moment, is 20.

Jan 1, 1994

By Mark D. Hannington

Results of the R/V Sonne Cruise (Edison) to the Tabar-Feni Arc from March 11 to April 5, 1994, a joint German-Canadian research cruise aboard the vessel R/V Sonne, undertook detailed mapping of the Tabar-Feni island chain, Papua New Guinea. The Tabar-Feni chain is host to several large porphyry stocks and epithermal gold deposits, including the giant Ladolam gold deposit on the island of Lihir (minimum 19 million oz. Au). The principal objective of the cruise was to map the seafloor in the vicinity of recently active alkaline volcanic islands in the Tabar-Feni chain and to characterize the tectonic setting of large high-level porphyry and epithermal gold deposits in the region. Additional work was carried out on shallow-water hot springs associated with mineralized geothermal systems on the volcanic islands. Complete sets of 1:50,000 scale (20-m contour) maps of the seafloor were produced for each of the four island groups (Feni, Tanga, Lihir, Tabar). The Lihir group was the most active and the most interesting. At least 4 (and probably 6 or 7), previously unknown volcanic cones were discovered within about 10 miles south of Lihir. The volcanoes are clearly very young and appear to have erupted along extensional faults produced by regional plate rotation. This recent volcanic activity appears to reflect recent forearc extension and represents the southward propagation of volcanic activity towards New Ireland. One volcanic cone at 1,490 m water depth is hydrothermally active, with very large areas of diffuse venting (100-200 m across), densely populated by beds of giant clams (probably calyptogena). Other vent-specific fauna are also present, including crabs, snails, sulfide worms, scale worms, limpettes, etc. The clam beds sit on a crust of hydrothermally baked and indurated, sulfidic, hyaloclastite-rich muds. The mineralization consists mainly of fine-grained disseminated pyrite and amorphous Fe-sulfides. A second, much larger cone at a depth of 1,070 m is capped by massive vesicular lavas which are intensely fractured and mineralized. Abundant sulfides and amorphous silica occur in stockwork-like veins which

Jan 1, 1994

By Alexander Malahoff

Mineral zonation studies were conducted on hydrothermal vents of two hot spot volcanoes. One study site is located within the Axial Caldera of the axial hot spot volcano of the Juan de Fuca Ridge. The young high-temperature hydrothermal vent field consisting of two polymetallic sulfide chimneys, five meters high, located at 130°01.5'W, 45°56.5'N, along a fault complex at the base of the southwestern wall of Axial Caldera was sampled during four ALVIN dives in 1983. Temperatures of up to 270°C were measured within the orifice of one of the chimneys, which was then broken off and recovered with the submersible. Both black and white "smoke" was observed to be emanating from the one chimney sampled. The high-temperature chimney extends directly from a field of broken lobate lavas which are located at a water depth of 1,550 meters, about 200 meters east of the caldera wall. The chimney makes one of the shallowest active high-temperature vents studied to date. The vent is surrounded by clumps of vestimentiferan worms and is located within an elongate field of red-colored iron smectite blankets and chimneys. The low-temperature field forms a ribbon 150 meters wide, extending for about 1,300 meters at the base of the wall. Chemical analyses of the hydrothermal deposits ranging from the polymetallic sulfides of the chimney to the outer zones of the low-temperature field show a range of elemental assemblages consistent with temperature zonation around the vent. Chemical zonation within the high-temperature

Jan 1, 1988

By Wilhelm Schwarz

Manganese nodules lay in vast areas of the deep sea floor. Ideal harvesting conditions for a manganese nodule field are dense nodule abundances of nodules between 20 and 60 mm diameter and a metal content as high as possible. With regard to the development of collector technology, the properties of the deep sea soil, in which the nodules are embedded and to which the nodules stick, are of major interest. The forces for loosening the nodules have to be provided by the collector. For this purpose water jets and/or mechanical devices can be employed. For the choice of the best collecting procedure, various criteria, such as collecting rate, energy consumption and the environmental impact on the eco system of the deep sea floor, have to be considered and weighted as to their importance. Nowadays, the concept of a mining system with a flexible transport hose and a self propelled collecting machine is increasingly accepted among the expert community. With regard to the trafficability of the deep sea soil with a self propelled mining machine, the mechanic properties of the soil and the morphology of the deep sea floor are of special importance. The manganese nodule fields, which are interesting with regard to their recoverability, are mostly in the areas of tectonic fracture zones, at which the morphology of the sea floor is formed by vulcanic activities. In these areas, deep sea mountains, pits and other obstacles exist that have to be driven around if not trafficable.

Jan 1, 2003

By Charles W. Finkl

Coastal and marine aggregate (sand and gravel) mining on US continental shelves is a major activity that supplies industrial and commercial demands for these raw materials. Because Pacific, Atlantic, and Gulf coasts contain significant shoreline segments that are in a critical state of erosion, sand-gravel and mixed sediment (sands with a high percentage of silt-plus-clay) deposits are mined in efforts to mitigate land loss. Sandy shores, and to a limited extent gravel coasts, erode by shoreline retreat due to relative sea-level rise and sediment starvation in littoral drift patterns. Mostly gravel shores occur in high latitudes and shorelines often advance seaward due to isostatic rebound following the LGM (Last Glacial Maximum 18,000 YBP). Sandy and fine-grained shores occurring in middle and low latitudes of the conterminous United States are problem coasts that require beach renourishment and reconstruction of barrier islands. Muddy coasts of the Mississippi Delta region are especially problematic because some islands are literally disappearing in response to subsidence. Replacement of sediments lost to the littoral drift system or returned to sedimentary sinks by drowning is thus a critical endeavor that involves annually dredging hundreds of millions of cubic meters of sediments from the continental shelf area. The types of shelf sediments that are amenable to marine mining techniques, their occurrence, and means of detection are highlighted in this paper. Minable Sediments on the Continental Shelf Wide varieties of sedimentary bodies that occur on the continental shelf are amenable to mining for beach renourishment and barrier island (beach-dune-marsh system) reconstruction. Relict terrestrial deposits make up a small but important proportion of shelf sediments that were deposited on coastal plains, now drowned by the post-glacial sea-level rise to form continental shelves. Examples of these deposits include drowned moraines, outwash plains, eskers, and kettles along the northern Atlantic coast in addition to siliciclastics along middle latitude Pacific, Atlantic, and Gulf coasts. Special cases include carbonate sequences along tropical costs of Florida and the muddy coasts of deltas, mostly in Louisiana. Specific types of minable deposits thus include shoreface attached sand sheets, dunes, and ridges in addition to offshore inter-reefal sands (between coral reefs in the Florida Reef Tract), bank deposits, and sand waves (ridges) that extend into US territorial waters. Nearshore siliciclastics include ebb-tidal deltas and bars. Drowned river valleys occur along all three US coasts and can be exploited for their fluvial sands if the covering mud sheets are thin.

Jan 1, 2005

By Frans van Grunsven, Cees van Rhee, Geert Keetels

One of the obstacles during the initial phases of project development is the assessment of the environmental impact. Mining residue, consisting of fine seafloor sediments, are to be discharged subsea to mitigate the impact of these suspended particles. In order to test the effectiveness of discharging in proximity of the seabed, a numerical model is developed within the open source software package OpenFoam. Dedicated laboratory experiments for numerical model validation are discussed within this paper. INTRODUCTION Siltation is considered one of the major pressures on the environment for a seabed mining operation. Siltation is defined as the pollution of water by a high concentration of suspended sediments like clay or silt. This can be caused by two main activities during the mining process: the spill loss during the excavation and the return flow of undesired seafloor sediment after ore filtration on the ship. In a concentrated cloud, these fine particles form a so-called turbidity plume. Prediction of the size of these plumes and the created layer thickness of deposited sediment is a crucial part of the environmental impact assessment. The challenge in predicting the behaviour of these plumes is found in the wide range of scales involved in the process. At the point of origin, the turbidity plumes spread mainly under the influence of turbulent whirls created by an initial momentum and a buoyancy difference due to the presence of the suspended sediment particles. If carried by ambientcurrents, these plumes can spread for several kilometres before blending in the background.

Jan 1, 2018

By Audrey Boissier, Marie-Anne Camon, Cecile Cathalot, Yves Fouquet, Laurent Bignon, Arnaud Agranier, Ewan Pelleter, Sylvain Bermell, Florian Besson

INTRODUCTION In October 2014, on behalf of the French government, Ifremer, along with the International Seabed Authority (ISA), signed a contract to start a detailed exploration program for seafloor massive sulfide (SMS) deposits in the work plan located on the slow spreading Mid-Atlantic ridge (MAR). The contract has a fifteen-year lifetime and the related exploration program must include the outline of SMS deposits and a resource assessment, as well as detailed environmental base line studies in the contract area. The exploration for SMS deposits generally includes detection of hydrothermal plume anomalies, acquisition of surface and near-bottom geophysical data, sampling operations from the research vessel (e.g. dredges, cores), and dive operations. The environmental studies include, among others, short and long-term oceanographic measurements, water column studies, biodiversity evaluation close and far from SMS deposits, characterization of natural hydrothermal plumes and related sedimentation. The HERMINE research cruise held from March 13th to April 28th 2018 (R/V Pourquoi Pas?) was the first cruise dedicated to exploration of active and inactive SMS and to the quantification of natural chemical input to the water column. The HERMINE cruise strategy was built up around three main objectives: (i) regional exploration including the detection of plume anomalies and the research of SMS deposits, (ii) local exploration of a SMS district and (iii) integrated study of a natural hydrothermal plume. This 3-in-1 cruise required us to optimize the switch between dives and surface operations. Day-time was devoted to dive operations whereas night-time was mostly dedicated to CTD/Rosette operations. The Nautile HOV (Human Occupied Vehicle) was well suited to the working time schedule of the cruise because it was time efficient in shorter (i.e. < 10h) dives due to fast descent and ascent speed, fast submerged forward speed, high maneuverability and the ability to carry heavy science payload as well as large volume of samples. Regional Exploration The first seventeen days of the HERMINE cruise were devoted to regional exploration, i.e. the detection of new plume anomalies and the research of new sulfide mineralization in the French work plan (10 000 km2; 6 clusters).

Jan 1, 2018