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By Peter M. Bartlett

The Republic of South Africa ranks among the world leaders in both reserves and production of numerous land-based mineral commodities. Over the last three decades, however, South Africa has also identified several commodities that may exist in commercial quantities in the marine environment. The major targets include 1) placer diamonds; 2) titanium- and zirconium-rich beach sands; 3) sedimentary and concretionary phosphorite and glauconite deposits; 4) manganese nodules; and 5) hydrocarbons. South Africa ranks second in world reserves of diamonds and has potentially enormous sea resources. Diamonds are currently recovered on the Atlantic side from ancient beach gravels in the Northwest Cape Province and from the seabed south of the Orange River to Lamberts Bay. Approximately 100,000 carats (or just 1% of South Africa's total annual production) are produced each year from offshore operations. DeBeers is investing approximately $5 million per year on sea prospecting activities and currently operates three vessels in offshore recovery operations. Diamonds recovered at sea will remain a small percentage of total production because of huge land-based reserves that are mined at a fraction of the cost of seabed operations.

Jan 1, 1986

By James R. Hein

Manganese nodules from the Cook Islands (CI) Exclusive Economic Zone (EEZ) are compositionally different from other nodule fields. CI nodules have relatively high cobalt concentrations and low nickel, copper, and manganese concentrations (e.g. Hein and Petersen, 2013). This reflects the predominantly hydrogenetic (seawater source) origin for metals in the CI nodules versus dual seawater-pore water sources for most other nodules. The concentrations of many critical and strategic metals have not been previously analyzed for CI nodules, so comparisons with other nodule fields have been limited. To address this, we analyzed a set of nodules distributed throughout the CI EEZ for a complete set of 67 elements, including all of the metals that may be of economic interest, such as the rare earth elements (REEs), yttrium, tellurium, niobium, zirconium, tungsten, titanium, and others (see selected elements in Table 1). In addition, we recalculated the tonnages of nodules and contained metals from nodule abundance areas (in square kilometers) determined by GIS ArcMap calculations based on JICA/MMAJ (2001) nodule distributions. The nodule tonnage calculated and summed from each abundance sector yields a total inferred resource estimate of 9.66 billion tonnes of nodules covering an area of 1.21 million square kilometers; using a cut-off of 6 kilograms of nodules per square meter, yields a median tonnage of 8.59 billion tonnes of nodules covering 687,647 square kilometers (Table 2).

Sep 14, 2011

By David Huber, John Halkyard

Deep Reach Technology, Inc. recently completed a multi-year cooperative research project for the U S Army Research Laboratory for the purposes of investigating recovery of rare earth elements from the seabed. This research led to the discovery of a potentially economical deposit in the Exclusive Economic Zone of the Cook Islands. In order to further develop this resource, Ocean Minerals LLC (OML) was formed in 2016 to explore the development of a deep-sea mining project to recover rare earth elements and scandium from the upper 10m of sediment in promising areas of the Cook Islands Exclusive Economic Zone. OML and the Cook Islands Investment Corporation signed an Agreement in 2016 giving OML exclusive rights to explore a 12000 sq km area and option rights over an additional 48,000 sq km. This poster presents the current status and activities related to this project.

Jan 1, 2017

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 J. R. Hein

East Diamante is a submarine volcano in the southern Mariana arc that is a complex caldera about 10 km x 5 km (elongated ENE-WSW), and breached on its northern and southwestern sectors. A large field of barite-sulfide mounds was discovered in June 2009 and revisited in July 2010 aboard the R.V. Natsushima using the Hyper-dolphin ROV. The mound field occurs on the NE flank of a cluster of resurgent domes inside the caldera. The mound field extends for more than 100 m long and is about 30 m wide, and is aligned along a NE-SW rift valley. A sample of dacite yielded a 40Ar/39Ar age of 20,000±400 years. Individual mounds are typically 1-3 m tall and 0.5-2 m wide, with lengths from about 3 to more than 5 m. The mounds are composed of barite-dominant layers interbedded with Zn-sulfide-rich barite layers. Rare inactive spires and chimneys cap some mounds. Fe and Mn oxides are currently forming small (<1 m diameter, ~0.5 m tall) subsidiary mounds on the top of some of the sulfate/sulfide mounds and drape the flanks of others. Both diffuse- and focused-flow fluids emanate from the subsidiary oxide mounds. Ages of the basal sulfate/sulfide mounds cluster around 4,000 years old based on 226Ba/Ba, whereas the oxides are less than 5 years old based on 228Th/228Ra. Most mound and chimney samples are dominated by barite and amorphous silica; sulfides occur in variable amounts that in decreasing order of abundance include sphalerite, galena, pyrite, and chalcopyrite. Anglesite, cerrusite, and a Pb phosphate occur as late-stage interstitial phases. Some mound samples have fragmental textures; layered clasts composed of chalcopyrite and pyrite may have been derived from collapsed chimneys. Despite the abundance of barite, samples contain high concentrations of Zn (to 23 Wt.%), Pb (to 13 wt.%), Ag (to 500 ppm), and Au (to 15 ppm). Copper is enriched in a few mounds samples, up to 3 wt.%, but is typically <1 wt.%. Other significant metal enrichments include Sb (to 1320 ppm), Cd (to 1180 ppm), and Hg (to 55 ppm).

Jan 1, 2011

By Cornel E. J. de Ronde

Brothers volcano (34°51.7?S, 179°03.6?E) is a large caldera volcano that forms part of the active Kermadec arc south of 32° S, NE of New Zealand. It is an elongate edifice striking NW-SE that is ~11-13 km long by 7-8 km across. The caldera has a basal diameter of 3-3.5 km and is surrounded by 350-450 m high walls with the floor 1,850 m deep. A volcanic cone of dacite composition rises 350 m from the caldera floor and partially coalesces with the southern caldera wall. Much of the caldera construction and the location of the hydrothermal vent sites are controlled by intersecting basement structures. Three hydrothermal sites have been recognized at Brothers; NW caldera, SE caldera and cone. Multiple hydrothermal plumes were mapped from the bottom of the caldera upwards to a depth of 900 m and originate from two of the sites; one on the NW caldera wall the other atop the cone. Analyses of these plumes show that the two vent sites are chemically distinct. The cone site itself hosts three distinct vent fields (summit, upper flank, NE flank) that in 1999 had plumes (mainly from the summit) containing relatively high concentrations of gas with a shift of -0.27 pH units (proxy for CO2) and H2S concentrations up to 4,250 nM, particulate Cu (PCu) of 3.4 nM, total dissolvable Fe (TDFe) of 4,720 nM, TDMn up to 260 nM and Fe/Mn values between 4.4 and 18.2. However, in 2002 plumes from the summit vent field had noticeably lower concentrations of PCu (0.3 nM), TDFe (175 nM), and Fe/Mn values of 0.8, although similar TDMn (220 nM) and shift in pH (-0.22) suggesting a state of flux for this site. By contrast, plumes originating from the NW caldera site have much less gas with a pH shift of -0.09 units and no detectable H2S, TDFe up to 955 nM, TDMn up to 150 nM, and Fe/Mn values of 6.4, and have not changed their composition over the same three year interval indicating a more chronic hydrothermal system. Plume d3He results show helium is decoupled from more near-surface vent fluid sources although a shift in R/Ra values from 6.1 ± 0.5 in 1999 for the combined vent sites to 7.2 ± 0.1 in 2002 indicates a less radiogenic input of helium over three years, suggestive of a greater magmatic input to the system.

Jan 1, 2004

By Jonguk Kim

Hydrothermal sulfides were recovered from the16°50?S triple junction area in the North Fiji Basin, at a water depth of ca. 1900 m. The chimney samples can be divided into three groups according to their major metal contents: 1) type 1 (Fe-Cu-rich), 2) type 2 (Fe-Cu-rich with minor Zn), and 3) type 3 (Zn-rich) chimneys. Type 1 chimneys are mainly composed of chalcopyrite and pyrite, and are enriched in elements commonly precipitated under high temperature conditions (> 300°C), such as Cu, Co, Mo, and Se. Type 3 chimneys consist dominantly of sphalerite and marcasite with traces of pyrite and chalcopyrite, and are enriched in elements commonly associated with low temperature (150 to 250°C), such as Zn, Cd, Pb, As, and Ga. Type 2 chimneys show mineralogy similar to that of type 1 chimneys but their metal contents range between type 1 and type 3 samples. Trace element compositions of basaltic rocks indicate that magma generation in the triple junction area was influenced by two different sources: N-MORB and E-MORB. Sulfur and lead isotope patterns of the hydrothermal chimneys show distinct differences between the type 1 and type 3 chimneys. For example, type 1 sulfides are depleted in 34S and have lower Pb isotope ratios compared to type 2 and 3 chimneys. The d34S values (0.4 to 5.6?) of chimney sulfides are typical range of sulfur isotope composition of sediment free mid-ocean ridge hydrothermal system. Type 2 and 3 sulfides show slightly higher d34S values than type 1 sulfides, which can be explained by subsurface boiling of hydrothermal fluids followed by mixing of saline solutions with ambient seawater. Lead isotope compositions of the chimneys indicate that the Pb in type 1 and type 3 chimneys originates from hydrothermal leaching of N-MORB and E-MORB volcanic rocks, respectively. Considering that both these chimneys are located in the same area, our model suggests that type 1 chimneys formed by hydrothermal circulation controlled by an intrusion of N-MORB magma; the fluids were not influenced by boiling during the formation of type 1 chimneys. In contrast, type 3 chimneys are younger and were formed by hydrothermal circulation closely related to E-MORB magma intrusion at shallower depth. The necessary conditions for phase separation of the hydrothermal fluids that formed the type 3 chimneys might result from changed P-T conditions in a shallower high-temperature reaction zone beneath the hydrothermal venting site. Under these conditions the fluid may cross the two-phase boundary for seawater, ensuring subcritical phase separation. The mineralogical and geochemical properties of these chimneys suggest that type 1 and type 3 chimneys were probably black smoker and white smoker, respectively. Type 2 chimneys might be product of low-temperature replacement of type 1 chimneys, which is related to formation of type 3 chimneys.

Jan 1, 2005

By Usui Akira

Mode of occurrence and compositional variations of iron-manganese deposits from seamounts around the NW Pacific submarine island-arc area are described on the basis of on-site description during the Moana Wave Cruise MW9507 and other Japanese cruises, as well as geochemical and mineralogical analyses and dating on collected samples. Hydrogenetic and hydrothermal iron-manganese crusts occur at more than 80 sites out of 150 dredge hauls within a small area of 200x 200 km in the back arc region. The hydrogenetic crusts may have grown continuously at slow rates, but 2-3 times faster than those from the Central Pacific, associated with depletion of Co, Cu, and Ni contents. The site-maximum thickness of the hydrogenetic deposits trends to increase with the increase of distance from the active volcanic chain or the age of substrate volcanic rocks. Also the observed great local variations in thickness within single sites and on small scales may be resulted from post-depositional geological activity at the seamounts such as calcareous sedimentation, collapse of volcanic body and mass wasting,. On the other hand, the rapid hydrothermal manganese mineralization has occurred in place and time during arc volcanism and rifting and is still in progress at modern active areas. The ninety ICP/ES chemical plus XRD analysis show that these deposits are of distinct composition by origin or topographic provinces, but small-scale variation of the deposits of each origin and micro-scale depth variation are not clear.

Jan 1, 2000

By Sabrina Warwas, Thomas Kuhn

"Due to rising prices and increasing demand of raw materials over the last years, marine mineral resources including manganese nodules have become a focus of study for industry and science. Marine ferromanganese nodules consist of micro-layers of different chemical and mineralogical composition which incorporate metals of high economic interest (Ni, Cu, Co, Zn, Mo, Li, rare earth elements; Hein & Koschinsky, 2015).The varying composition of the layers depends on different growth processes, such as hydrogenetic (metal precipitation from the water column under oxic conditions; Mn/Fe = 3), diagenetic (metal precipitation from the sediment pore water) under oxic (Mn/Fe 3-10) or suboxic (Mn/Fe = 10) conditions; (Wegorzewski & Kuhn, 2014) or hydrothermal (metal precipitation from low-temperature hydrothermal fluids; Kuhn et al., 2003).METHODSIn this study, manganese nodules from three different locations of the Atlantic Ocean (Galicia Bank; Vema-Fracture-Zone and Brazilian Basin) were analyzed for their geochemical and mineralogical composition. Detailed information about the samples are given in table 1. The geochemical and mineralogical composition of bulk nodules were determined by XRF, ICP-MS/OES as well as XRD and the single micro-layers by high resolution analyses with electron microprobe and LA-ICP-MS."

Jan 1, 2017

By S. Jeffress Williams

The topic area for this paper covers the United States portion of the northern Gulf of Mexico, extending from the Rio Grande delta east to the Florida peninsula. Declaration of an Exclusive Economic Zone in 1983 expanded Federal economic jurisdiction on the continental margins from 12 to 200 nautical miles seaward from the coast. The nation-wide area of the EEZ totals 3 million square nautical miles, with approximately 186 thousand square nautical miles in the Gulf of Mexico. In the Gulf, the continental shelf has an area of 81 thousand square nautical miles, extending to a depth of 600 ft. and having widths of 6 to 120 nautical miles. Specific areas on the shelf offer the greatest potential for containing aggregate and other hard mineral resources. The primary geomorphic features along the Gulf coast include: barrier islands, chenier plains, tidal inlets, bays and lagoons, estuaries, and deltaic headlands. These features are composed of terrigenous siliclastic sediments, except for the west Florida coast, south of 29°N latitude, which is dominated by carbonate sediments. On the shelf, the primary features are linear sand shoals and associated sand sheets, relict delta lobes and channels, and banks related to salt diapirs and coral reefs. The composition and distribution of sediments in these coastal and shelf features are determined by numerous geologic factors including: seabed topography; riverine sediment discharge; sediment dispersal patterns due to currents, waves, storms and tides; tectonics and subsidence; and repeated fluctuations in sea level.

Jan 1, 1986

By Johnson R. Cann

Ocean floor sulfide deposits are now known from many parts of the world mid-ocean ridge system and from some seamounts. Clearly they can be expected to occur commonly on the ocean floor. However, only two or three of the known deposits appear to approach the million-ton size, and in none of the deposits has the grade been well-defined. Can knowledge of the processes that happen within the hydrothermal plumbing below deposits help define the conditions under which large, high-grade deposits form? Here I review present knowledge of ocean-floor hydrothermal processes to attempt a first answer to this question. There are three sources of information about these processes. The solutions emerging from active systems must be compatible with patterns of alteration that underlie the volcanogenic sulfide deposits of ophiolite complexes, which are slices of ocean crust thrust onto land. Both of these types of evidence can be linked by computer modelling of the exchange of heat and metals between rocks and flowing water.

Jan 1, 1988

By Lisa Koch, Eleanor Martin

"Each underwater mining project is different. However, most have one thing in common: To be successful. We will draw on our experience advising hundreds of international clients each year on mining, offshore oil & gas and shipping matters to highlight some legal, commercial and practical issues to consider when structuring underwater mining projects. We will look at new ways of allocating risks and rewards in order to obtain much needed investment for underwater mining projects to commence both the exploration and exploitation phase.HighlightsRisk profileWe will look at a typical underwater mining project from the viewpoint of an investor and highlight some of the perceived risks, and potential mitigants.Contractual structureWe will analyse how the mining industry and oil & gas service industry have responded to low commodity prices to examine innovate contractual arrangements with suppliers and stakeholders, and how they can be tailored to the underwater mining industry. FinancingWe will explore some potential financing structures which could be relevant to the underwater mining industry."

Jan 1, 2017

By J. Bruce Gemmell

ODP Leg 158 drilled seventeen holes into the active TAG hydrothermal mound and underlying stockwork, 26°N, Mid-Atlantic Ridge. Drilling in five different areas, including a high-temperature black smoker complex and a lower-temperature white smoker vent field, revealed the multi-stage depositional history and character of sub-seafloor mineralization and alteration. The upper portion of the mound consist of massive pyrite and pyrite breccias which are underlain by pyrite-anhydrite breccias and then by quartz-pyrite breccias. Quartz-pyrite breccias grade down into silicified wallrock breccias. Chloritised basalt breccias occur at depths greater than 100 m. Several stages of quartz-pyrite±chalcopyrite veins occur in the stockwork zone and lower portions of the mound, whereas anhydrite±pyrite±chalcopyrite veins occur within the upper parts of the mound. Recovery of unaltered basalt near the edges of the mound has constrained the extent of the stockwork zone to a pipe-like feature 80 meters in diameter. A detailed sulfur isotope investigation of sulfides and sulfates within mound and the underlying stockwork zone has revealed the overall range of sulfide d34S analyses to be 0.35% to 10.27%. Anhydrite has a tight range of d34S values 20.55% to 21.56%. There are distinct differences in d34S values between the different textural types of pyrite (massive sulfide, breccia clasts, disseminations associated with alteration, and veins). The massive sulfide and breccia clasts have a similar distribution of d34S values (6%-8%), however the d34S values of the disseminated pyrite associated with the alteration are distinctly heavier (8%-10%). Vein sulfides have the lightest d34S values (5%-7%). Sulphur-isotope values at TAG are, in general, the heaviest reported for unsedimented mid-ocean ridge deposits.

Jan 1, 1998

By Irina A. Pulyaeva

Hydrogenetic Fe-Mn crusts are ubiquitous in the ocean basins and play an important role in marine mineral-deposit research because of their widespread occurrence and high concentrations of valuable and rare metals. Directed research, which started in the last quarter of the 20th century, has provided significant results, with substantial amounts of data produced on Fe-Mn crusts structure, composition, and distribution in the global ocean. Detailed study of several seamounts has given confidence about the scale of Fe-Mn crust development and their characteristics. Now, commercial interests gain more and more attention. However, at the same time some theoretical questions related to Fe-Mn crust history including controls on metal sources and concentrations have not yet been answered. Here, we present the overview of age, composition, distribution, and geological setting of hydrogenetic Fe-Mn crusts from Pacific and Atlantic seamounts and discuss the geological evolution and conditions that led to the formation of potentially economic concentrations of metals. The age, composition, and distribution of Fe-Mn crusts in the Atlantic and Pacific oceans were determined by using a Fe-Mn deposits database compiled from our original data, published papers, published databases, and other international sources. Comparative analysis of Fe-Mn deposits from the Atlantic and Pacific oceans shows that there are similarities in basic characteristics of crust formation in both oceans. Simultaneously, there are significant differences in the scale of Fe-Mn crust distribution and composition that can be explained by differences in geological settings and characteristics of the deposition environment.

Jan 1, 2011

By James R. Hein

Ferromanganese oxyhydroxide crusts (Fe-Mn crusts) precipitate out of cold ambient seawater onto hard-rock surfaces at water depths of about 600-4000 m throughout the ocean basins. Fe-Mn crusts concentrate most elements in the Periodic Table above their mean concentration in the earth&apos;s crust (continental plus oceanic crust), except for the major rock-forming oxides and also notably gold and palladium. Tellurium is concentrated greater than any other element relative to its earth&apos;s crust mean (about 1 ppb). For example, mean contents of the elements heretofore known to be most enriched in crusts, Mo, Tl, Sb, Co, Mn, Bi, As, Se, and Pb are enriched 100 to 1000 times over their earth&apos;s crust mean, whereas the mean Te content in Fe-Mn crusts is enriched about 50,000 times. However, the distribution of Te in the earth is poorly known. Estimates of the mean Te content of the earth&apos;s crust range from 0.36 to 10 ppb, with 1 ppb being the most commonly cited mean content (compilations in Levinson, 1974 and Govett, 1983). If we took the highest estimate of 10 ppb, then Te would be enriched in Fe-Mn crusts five times more than the next most enriched element, or 5000 times the estimated maximum mean earth&apos;s crust.

Jan 1, 2000

By V. K. Banakar

The occurrence of hydrogenous ferromanganese encrustations (Fe-Mn crusts) on the Cretaceous age Afanasiy-Nikitin Seamounts (ANS) in the eastern Equatorial Indian Ocean (EEIO) was first reported by Banakar et al. (1997, Marine Geology). The major element composition of the samples from the upper flank of the ANS (~1650 m water depth) indicated enrichment of Co up to 0.9 % (Parthiban and Banakar, 1999, Indian Mineralogist). Subsequently a project supported by the Department of Ocean Development to explore the ANS for Co-enriched Fe-Mn crusts was launched in 2002 by the National Institute of Oceanography. Sampling at regular depth intervals along two transects on the slopes of the northern elevated region of the ANS was carried out. The Fe-Mn oxide deposition is evident on almost all types of substrates viz., basalts, conglomerate limestone, fossil corals etc., and the thickness of the oxide layer varies from a patina to 7 cm. The Fe-Mn crust growth is evident only above a water depth of 3200 m, below which semi-lithified carbonate ooze is dominant. The ANS Fe-Mn crusts from all the water depths exhibit Mn/Fe < 1.5 suggesting pure hydrogenetic accumulation of metal-hydroxides. Bulk sample Ce-contents for a few selected depth-representative samples are remarkably high, up to 3700 ppm with an average of ~2500 ppm. The positive Ce-anomaly decreases from ~8 at 1600 m depth to ~1.6 at 3200 m depth, which is in contrast to the modern dissolved oxygen depth-profile in the region. This observation suggests that major time-period of the Fe-Mn crust accretion history is dominated by ambient waters with lower-oxygen at deeper depths than at the intermediate depths. This in turn probably suggests a major reorganization in the deep-intermediate hydrography of the region in the past.

Jan 1, 2005

By Malcolm Clark, Robin K. H. Falconer

There are a number of likely impacts from mining operations, but a key issue is uncertainty about the environmental effects of sediment plumes created by disturbance to the seafloor and discharge of processed waters. The New Zealand National Institute of Water and Atmospheric Research (NIWA) is undertaking a research project to improve understanding of such impacts (relevant to both mining and trawl fisheries), by examining the extent and persistence of sediment plumes, the immediate impact and subsequent recovery of seafloor exposed to these plumes, and the effect on functioning of ecologically significant species. The project will use a combination of field survey experimentation with in situ observations and controlled laboratory-based experiments. The field work begins in May 2018 when an area of up to 1km2 at depths of 400-500 m on the Chatham Rise, 450 km east the New Zealand South Island will be subjected to disturbance by an upgraded former NOAA Benthic Disturber. The suspended sediment load created by the disturbance will be tracked and monitored, with the effects on seafloor animals examined by pre-and post-disturbance sampling. A wide range of seafloor sampling, benthic landers, towed cameras, oceanographic moorings and water column monitoring will be carried out over a three week period. Monitoring surveys will be repeated in 2019 and 2020 to determine the longer-term resilience and recovery of disturbed communities. The laboratory-based side of the programme, also starting in 2018, involves holding live deep-sea corals and sponges in tanks at NIWA, and exposing them to various levels and duration of particle loads in the water in order to reveal lethal thresholds as well as sub- lethal effects of settled and suspended sediment.

Jan 1, 2018

By C. Wildman

Prospectivity modeling of seafloor massive sulphide (SMS) deposits has been completed over the Kermadec Arc-Colville Ridge area using the GIS based weights of evidence and fuzzy logic modeling techniques. SMS deposits are the current equivalent of ancient onshore volcanogenic massive sulphide (VMS) ore deposits. These high-grade deposits are formed on the seafloor and commonly consist of a black smoker and metal rich sediment mound complex resulting from the discharge of hydrothermal fluids (up to 400°C) from fractures on the seafloor. Metal sulphides are continuously precipitated in response to mixing of high-temperature hydrothermal fluids with ambient seawater. Accumulation of metal sulphides has led to SMS deposits being potentially major sources of copper, zinc, lead and other metals such as gold, silver, which to date remain untapped. Modeling of SMS deposits was undertaken to illustrate the power of GIS modeling for seafloor resource evaluation and how it can be used to quickly identify and rank in terms of the most likely prospective areas of the seafloor where new SMS deposits might exist. The mineral deposit modeling was constrained by the mineral systems concept which defines those parts of a mineralisation system that are critical to the ore-forming process. The deposits are typically formed in extensional tectonic settings, including both submerged tectonic margins and sea-floor spreading. Volcanic vent systems and underlying dykes, stocks and sills are the sources of heat that are responsible for converting sea water drawn down through fractures in the oceanic crust into an ore-forming hydrothermal fluid. This fluid is then capable of leaching metals and elements from surrounding footwall rocks, which are then transported upwards via the convection of hydrothermal fluids. The ore materials are then precipitated within the black smoker field as massive sulphides due to the mixing of high-temperature (250-400°C), metal-rich hydrothermal fluids with cold (about 2°C) oxygen bearing seawater.

Jan 1, 2011

By Georgy A. Cherkashov

Two principal types of the hydrothermal fields in Atlantic - axial and off-axis - could be established based on their structural setting in the rift zone of the Mid-Atlantic Ridge (MAR) (Figure1). The first (axial) type is represented by five high- and three low-temperature hydrothermal sites (Table 1). All of these fields are connected with young axial effusive volcanism and related to large linear volcanic ridges or central volcanoes at the inner floor of the rift valley. The hydrothermal activity here is controlled by the intersection between longitudinal magma feeding faults and transverse weakened zones characterized by high permeability. [ ] The hydrothermal sites of the second (off-axis) type (such as Rainbow, TAG, 24°30?N, Logatchev, newly discovered 13°N (Figure 2) and possibly 16°48?N sites) are related to large tectonic dislocations forming marginal scarps of the rift valley as well as transverse discontinuities.

Jan 1, 2003

By Timm Schoening, Greinert. Jens, Iason –. Zois Gazis

"Ferromanganese nodules are again of interest because of their high concentrations of Ni, Co, Cu as well as REE. With regards to an operational underwater mining industry, one of the main questions and important requests is to finding a method that can predict the abundance of nodules with high accuracy within reasonable time spans, without many requirements for ground truth data; and all these on an operational scale and ideally automated. In this regard, we present results of a study based on the combination of highresolution multibeam and optical data acquired by an AUV using specific machine learning techniques to reveal a detailed distribution of the Mn-nodules in correlation to the seafloor terrain. The accuracy of the method employed and results gained were validated and approved through comprehensive statistical analysis and by comparison to box-core data.Study AreaOur study area (AUV survey block G77) is located in the Clarion-Clipperton Zone (CCZ) (Eastern Central Pacific Ocean), an area that has been receiving international research and industrial attention for many years already (e.g. McKelvey et al., 1979; Bernhard and Blissenbach, 1988, von Stackelberg and Beiersdorf, 1991, Jeong et al. 1996). Block G77 covers an area of 9.5km2 in a depth between -4478m and -4536m. The area is characterised by gentle slopes 0-5° (0-3° in most of the area and only in the outer parts of the Block slopes can exceed 5°). The seafloor is characterised by moderate to low rugosity, the only exception being a small area in the eastern part, where sub-recent smallscale volcanic activity created 15 cone-shaped morphological features of up to 55m height and 150m width that are clustered in an area of 700 x 380m (Figure 1)."

Jan 1, 2017