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By Sung-Hyun Park

Core sediment samples collected from the KODOS area of the Clarion-Clipperton Fracture Zone in the NE Equatorial Pacific were analyzed for chemical and mineralogical compositions to investigate the depth- and time-related variation of paleoenvironmental and paleoceanographic conditions during their deposition. These core sediments are divided into three layers from top to bottom by its color; 1) brown layer (Unit I), 2) pale brown layer (Unit II), and 3) black brown layer (Unit III). Geochronology of 10Be indicated the depositional age of Quaternary for Units I and II and of late Pliocene for Unit III with a potential short hiatus between them. Analyses of interelemental correlation identified three major groups of elemental groups that show moderate-to-strong correlations: 1) Al, Ti, K, and Fe representing for terrestrial alumino-silicate fraction of sediments, 2) Ca, P, REEs, Cu, and Zn for biogenic apatite, and 3) Mn, Ni, and Co for hydrogenous Mn-oxide. With an exception, Fe content was very high and showed fair correlations with Mn, Ni, and Co in Unit III. Unit III shows high smectite but low quartz and illite contents compared to the overlying two units, indicative of reduced supply of terrestrial materials. In a meanwhile, major elements (Fe2O3, CaO, P2O5), minor elements (Cu, Zn) and REEs are highly enriched in Unit III compared to the upper two units. All these elements other than Fe reflect the fraction of biogenic apatite, which indicates higher fraction of biogenic components in Unit III. This is also supported by higher amount of smectite formed by the consumption of siliceous biogenic components. The reduced supply of terrestrial material and/or increased productivity of surface water at the time of Unit III deposition are attributed to Pliocene warming preceding Northern-pole glaciation during Quaternary. Unit III also includes clinoptilolite and unidentified 8Å mineral, likely amphibole, that are absent in Units I and II, suggestive of the possibility of different source region and/or materials during Pliocene. Higher contents of Mn and Fe in Unit III are likely due to the high fraction of Mn-oxide that was formed by diagenetic process after deposition.

Jan 1, 2003

By C. H. Hobbs

A recently completed series of projects funded by the Commonwealth of Virginia and the U.S. Minerals Management Service was designed to assess the distribution of heavy minerals on the inner continental shelf adjacent to Virginia. These projects indicate that a suite of minerals of both strategic and economic interest is present. Analysis of several hundred grab and core samples shows that zircon, monazite, and titanium minerals (ilmenite, rutile, and leucoxene) occur in quantities that probably warrant further study by the mineral industry. Furthermore, side-scan sonography and shallow seismic profiles have provided information on the thickness and areal extent of the mineral-bearing sands. Possible development of the resource is enhanced by a potential use of offshore sand for beach nourishment. The results of the preliminary studies have been presented in open-file publications and oral reports in order that the mineral industry might have an up to date basis upon which to consider more exploratory work. Much of the effort south of the mouth of Chesapeake Bay was made in cooperation with and enhanced by an independent study of sand resources for beach nourishment and other needs. Preliminary review of the quantitative analyses of the heavy-mineral content of several hundred samples demonstrates that the distribution of high concentrations is non-uniform. From core data, the greatest abundances of some economic heavy minerals (ilmenite, rutile, leucoxene, monazite, and

Jan 1, 1988

By Peter A. Rona

Investigations of the Gorda Ridge within the proclaimed U.S. Exclusive Economic Zone off northern California and southern Oregon, and the Mid-Atlantic Ridge extending along the center of the Atlantic Ocean, have received new impetus from the discovery of hot black smokers, sizeable polymetallic massive sulfide deposits, and vent animals at the Mid-Atlantic Ridge by the NOAA VENTS Program in 1985. Prior to that time, the oceanographic community focused investigations of seafloor venting at the faster-spreading oceanic ridges of the Pacific Ocean including the East Pacific Rise, the Galapagos spreading center and the Juan de Fuca Ridge because a consensus held that the faster spreading rates at these ridges were necessary to supply the heat to drive black smoker-type venting. As the only oceanic ridge in the Pacific with slow-spreading characteristics, the Gorda Ridge is an outlier of the slow-spreading ridge system that extends through the Atlantic Ocean and western Indian Ocean comprising more than half the 55,000-kilometer-length of the globe-encircling oceanic ridge system. In response to recent discoveries at the Mid-Atlantic Ridge the oceanographic community is shifting more of its activity to investigation of hydrothermal venting and related processes at slow-spreading oceanic ridges. The discovery cruise by a team of NOAA and university scientists followed by

Jan 1, 1988

By Jonguk Kim

Texture and geochemical composition of hydrogenous ferromanganese crust from relatively adjacent three seamounts (OSM2 at 157°35'E, 13°55'N, Lomilik at 161°37'E, 11°42'N and Lemkein at 165°05'E, 9°18'N) near the Marshall Islands in the western Pacific (Figure 1) were investigated in order to elucidate their growth history. These seamounts, located in different latitudes, are along a line that is parallel with the direction of Pacific plate movement. Thick crusts commonly have three or four distinct layers (Figure 2): (1) layer 1, uppermost layer, is black, dense, and has a botryoidal, columnar, or laminated texture; (2) layer 2, overlain by layer 1, is Fe-stained, porous to vuggy and filled with sediment; (3) layer 3, phosphatized layer, is black, massive, dense, and impregnated by CFA, (4) layer 4 shows parallel to undulatory laminated texture and cut by CFA-filled veins. Layer 1 and 2, unphosphatized young layer, are observed in crust samples collected from all seamounts. However, lower part of the crust shows different textures in different seamounts. Both layer 3 and 4 are found in thick crust from OSM2 but layer 4 is absent in crust samples from Lemkein and Lomilik. All the uppermost layers (layer 1) from three seamounts have similar textural and geochemical characteristics. Layer 2 is overlain by layer 1, is porous, partly Fe-stained, and sediment-infilled. In previous studies, layers 1 and 2 have grown in different oceanic environment. Textural and geochemical properties show that layer 1 has grown under relatively higher bottom water activity and lower productive environment than layer 2. Carbonate and detrital materials in layer 1 are not abundant compared to layer 2. Layer 2 can be assumed to have grown under equatorial high productivity zone (EHPZ) while layer 1 has started to grow when the seamount left from the EHPZ.

Jan 1, 2003

By Natalia Konstantinova, Kira Mizell, James R. Hein, Georgy Cherkashov, Amy Gartman, Mariah Mikesell

"Two types of metallic deposits have been found in the deep Arctic Ocean: Hydrothermal Fe, Cu, and Zn sulfide deposits form along Gakkel Ridge in the Eurasia Basin and associated ridges between Greenland and Europe; and iron and manganese oxide crusts (Fe-Mn crusts) and nodules, precipitated from seawater onto rock surfaces in the Amerasia Basin, contain many rare metals of economic interest. Fe-Mn crusts and nodules collected in the Amerasia Basin during 2008, 2009, and 2012 cruises on the USCGC icebreaker Healy are characterized by unique mineral and chemical compositions, very high Fe/Mn ratios, fast growth rates, and other unique characteristics compared to those formed elsewhere in the global ocean. These characteristics reflect temporal and spatial variations in geological, oceanographic, and climatic conditions in the Arctic Ocean and surrounding continents over the past ~15 Myr.RESULTS AND CONCLUSIONSDiscrimination diagrams show that the crusts and nodules found in the Amerasia Basin north of Alaska are hydrogenetic. However, the mineralogy is not typical for hydrogenetic Fe-Mn crusts and nodules, which usually include only amorphous Fe oxyhydroxide and ?-MnO2 (vernadite). The Arctic samples also include the Mn oxides birnessite and 10Å manganates (todorokite, buserite, asbolane), and the Fe minerals also include goethite, lepidocrocite, feroxyhyte, and ferrihydrite. This mineralogy reflects formation under lower oxygen conditions than typical for samples formed elsewhere.The Amerasia Basin crusts have a unique chemical composition compared with crusts from other areas of the global ocean. The key difference is the high Fe contents relative to Mn contents, which determines the types of trace metals hosted by the Fe-Mn oxide phases, and their concentrations. The high Fe/Mn ratios reflect the expansive continental shelves (>50% of the Arctic Ocean) and upper slopes that support redox cycling and release of Fe and other metals to bottom waters, and to the large fluvial input from North America and Siberia. Brine formation on the shelves and currents promote the distribution of the metals throughout the Amerasia Basin, including the deep basins."

Jan 1, 2017

By Jai-Woon Moon

Lemkein seamount located in the west of the Kuwajleen Atoll of RMI is a relatively samll, simple-shaped, peaked type seamount with its base at 4,500 m and summit at 1,452 m water depths. Ferromanganese crusts were identified in the water depth range between 2,000 m and 2,500 m, and they were mostly observed on the northern slopes of the seamount. Among various substrate rocks, breccia occurred most commonly with crusts and formed the thickest crust layers. Average thickness of the Lemkein crusts was about 5 cm. Their chemical compositions were similar to other crusts found in the RMI area; Mn=25.82%, Fe=15.29%, Co=0.74%, Ni=0.56%. Lemkein crusts were characterized by their four distinctive internal layers; 1) Massive Layer 1; 2)Porous, Fe-stained or sediment infilled Layer 2; 3) Massive to slightly porous Layer 3; and, 4)Massive, Dense, Phosphotized, CFA veined Layer 4. Layers 1 and 2 were generally similar in composition, but highest Co concentrations were measured in Layer 1 while relatively higher concentrations of Al, Rb, Fe, and Ti were observed in Layer 2. Layer 3 showed higher concentrations of Ca and P than Layers 1 and 2. Based on the Co-chronography, the age of Layer 1 is 0¡?6 Ma (growth rate = 1.50 mm/Ma), Layer 2 is 6¡?15 Ma (1.75 mm/Ma), Layer 3 is 15¡?27Ma (1.76 mm/Ma), and Layer 4 is 27¡?45 Ma (2.06 mm/Ma). These preliminary results indicated that high Co contents in Layer 1 resulted from slow growth rates; Layer 2 was formed under relatively strong influence of high terrestrial input; and, Layer 3 was probably affected by a minor phosphatization event occurring in 15 Ma.

Jan 1, 2000

By Delphine Pierre, Jean-Marie Augustin, Anne-Sophie Alix, Charline Guérin, Cecile Cathalot, Yves Fouquet, Arnaud Gaillot, Ewan Pelleter, Carla Scalabrin, Florian Besson

With the world’s growing demand for metals, seafloor massive sulfides (SMS) deposits are now seen as a possible mineral resource that could contributes to secure metal supply for human needs. SMS deposits are characterized by high concentrations of base metals and at some place high contents of precious and rare metals. Since 1977 and the discovery of the first high temperature (HT) hydrothermal vent and its sulfide mineralization and high biodiversity, more than 300 sites are known today. If the exploration strategy for detection of active hydrothermal sites is now robust, their associated mineralization will not (and must not) constitute a potential target for deep-sea mining due to environmental concerns and technical limitations. Recent studies on SMS deposits are rather focused on extinct and buried mineralized sites characterized by a lower biomass. Several geophysical techniques to explore and detect extinct SMS (eSMS) and buried SMS (bSMS) have been developed (e.g. Kawada and Kasaya, 2017; Szitkar et al., 2017, 2014) using different approaches (e.g. regional or local scale; ship-based or using underwater vehicles) with several degrees of success or limitation. Here we present results from acoustic surveys performed on the TAG hydrothermal district during the BICOSE (2014) and LEVE-SMF (2016) cruises and direct observation provided by HOV (Nautile) dives carried out during HERMINE cruise (2017). Acoustic data were acquired using two different multibeam echosounders (MBES): the hull-mounted Kongsberg EM122 (12 kHz, R/V L’Atalante) and the ROV-mounted RESON SeaBat 7125 (400 kHz, ROV Victor) (Figure 1). After processing, acoustic seafloor backscatter data from both MBES provides complementary qualitative results in relation to the seafloor composition. The analysis of the seafloor backscatter data obtained by near-seafloor surveys with the high-resolution 400 kHz MBES shows a clear relationship between low backscatter strength values and areas covered with pelagic and hydrothermal sediments whereas high backscatter strength values are associated to pillow lavas and basaltic scree. Intermediate backscatter strength values are rather related to old and younger eSMS as well as to mineralization on TAG active mound.

Jan 1, 2018

By Carsten Rühlemann

Between 2008 and 2013, the German Federal Institute for Geosciences and Natural Resources (BGR) carried out five exploration cruises to the German license area in the eastern Pacific Nodule Belt. The first two expeditions were mainly dedicated to multibeam mapping to obtain an overview of the seafloor topography and acoustic backscatter strength. These data were used to identify ten to fourteen prospective nodule fields for potential future mining, which together cover about 16% of the total license area of 75,000 km2. During the last three cruises, three of these potential mining areas were explored in detail. For this purpose, the BGR developed a suite of exploration methods to map nodule size distributions and nodule abundances. These methods include acoustic surveys with vessel-based multibeam systems as well as near-bottom video mapping complemented by in situ sampling. The economically most valuable field has a size of ca. 2,000 km2, of which 34% is covered by medium to large nodules (> 4 cm long axis of nodules) with an average abundance of 22.4 kg/m2 and 44% is covered by small nodules (< 4 cm) with a mean abundance of 17.5 kg/m2. The total mass of nodules in this field comprises more than 30 million tons wet weight and could sustain deep-sea mining for at least 10 years.

Sep 14, 2011

By C. L. Mardock

The U. S. Bureau of Mines participated in a two-year joint State of Oregon/Department of Interior Placer Task Force study on the economic and environmental aspects of Oregon&apos;s marine placer deposits. The effort culminated in a research cruise off the southwest coast of Oregon to investigate the geological and biological characteristics of the continental shelf deposits. The Bureau&apos;s role was to collect and study the placer material off the continental shelf and to determine its strategic potential and significance. In-depth characterization of the sediments by optical and electron microscopy verify that the placer material from Cape Blanco contains up to 3 pct ilmenite, 0.5 pct chromite, and small amounts of zircon and gold. However, harsh sea conditions and equipment failures prevented sampling below a four-foot depth at the Cape Blanco site. Results to date indicate that the deposits sampled off the southwest coast of Oregon do not represent a significant source of strategic minerals. However, further study of the deeper sediments off Cape Blanco may uncover significant concentrations of chromite. This presentation encompasses the site geology, the geophysical and biological activities of the expedition, and the results of the Bureau&apos;s mineralogical and chemical investigation. The combined findings of the Bureau and other Task Force agencies have provided information needed to expand the country&apos;s limited knowledge of marine mineral resources and has assisted state and federal agencies in the formulation of offshore mineral policies.

Jan 1, 1991

By M. F. Dibble

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

Jan 1, 1986

By Glen Smith

Nautilus Minerals, the world?s leader in exploration and development of deep ocean seafloor resources, is today focused on the recovery of high-grade copper and gold in seafloor massive-sulphide mineralization. These targeted mineralized belts, analogous to land-based volcanogenic massive sulphide deposits, are located near plate boundaries in the back arc basins of the Western Pacific. The first deposit to be developed by the company is located at a depth of 1,600 meters at Solwara 1, in the benign waters of the Bismarck Sea. This location lies within the territorial waters of Papua New Guinea. From 2006 to 2009 the company completed detailed environmental and geological studies at Solwara 1, culminating in a number of world firsts, including the first Environmental Permit granted for the extraction of seafloor massive sulphide deposits and the first NI 43-101 compliant seafloor massive sulphide deposit resource statement. Nautilus has relied heavily on proven deepwater technologies from the oil and gas industry in the design of its production system. Pipeline trenching units, workclass ROVs, deepwater production risers and drill cuttings removal systems will be adapted to initiate this new and exciting industry. Key contractors used by Nautilus on this innovative project have all been selected for their deepwater experience (gained in the oil and gas industry), creativity and determination to launch this new industry successfully. Innovation is at the forefront of Nautilus? success to date. This paper summarizes the progress to date of this development which will provide a new source of minerals for the world and which will contribute to sustainable growth for the future.

Jan 1, 2010

By Georgy Cherkashov

Shallow-water formation of marine ferromanganese nodules as well as their deep-water analogues is found throughout the global ocean. The Baltic Sea is a key province for the shallow-water type of marine minerals. The following main distribution areas of Fe-Mn nodules have so far been discovered in the Baltic Sea: the Gulf of Bothnia, the Gulf of Riga, Central Baltic area (Gdansk- Klaipeda) and the Gulf of Finland. The last area (Gulf of Finland/Finnish Bay) is the best studied from all aspects including geological prospecting and environmental assessment.

Sep 14, 2011

By Peter E. Halbach, Andreas Jahn

"Co-rich ferromanganese crust deposits exist on slopes, summits and platforms of seamounts and guyots throughout the global oceans, where deep-sea currents have kept the seafloor structures more or less free of sediment for millions of years. They form by direct precipitation from cold seawater under more or less oxic conditions and consist of thin layers (2 up to 25 cm thick) covering hard substrate rocks in water depths of 800 to 5000m (Halbach and Marbler, 2009; Hein et al., 2000). Besides Mn these crusts contain interesting concentrations of minor elements (Co, Ni, Ti and Cu) and trace elements (Mo, W, Te, Ga, Pt and REEs), thus they represent significant metal deposits and promise potentially valuable additions to the world’s metal resources.The prospects for mining of this marine type of metal deposits largely depend on the grades and the scale of the potential ore resources. However, only a few percent of existing seamounts and guyots have been mapped and sampled in detail, most of them in the Pacific Ocean. Therefore, a model to estimate the geological resources based on the global seamount catalogue of Wessel (2001; revised: Wessel et al., 2009) and the empirical parameters which control the metal composition and distribution was developed."

Jan 1, 2017

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

By Natalia Konstantinova, Kira Mizell, James R. Hein, Georgy Cherkashov

"Ferromanganese crusts and nodules from the Amerasian basin of the Arctic Ocean are characterized by a unique composition compared to crusts formed elsewhere in the global ocean (Konstantinova et al., 2017; Hein et al., 2017). One of the most significant differences from global ocean crusts is the high detrital mineral content; mass balance calculations show that it may be as high as 35% in some samples (Hein et al., 2017).These Arctic Ocean Fe-Mn crusts also typically have three distinct megascopic layers, except for thin crusts; less commonly, four layers are noted for thick crusts. The age of initiation of Fe-Mn crust growth in the Amerasia Basin varies from 14.8 Myr to 0.7 Myr ago based on the Manheim and Lane-Bostwick (1988) Co chronometer, Be isotopes, and Th excess methods (Dausmann et al., 2015; Konstantinova et al., 2017; Hein et al., 2017).Samples and MethodsFourteen Fe-Mn crust samples recovered on Russian and U.S. research cruises were chosen for analyses based on their morphology, composition, water depth, genetic type, and location in Amerasia Basin. Seven samples from four distant dredge sites along Mendeleev Ridge and seven samples from four locations on the Chukchi Borderland are included (Fig. 1). Dredge site water depths vary from 3850 to 2100 m with the deepest samples from the Chukchi Borderland. Many of the selected samples were described in previous publications (Konstantinova et al., 2017; Hein et al., 2017)."

Jan 1, 2017

By P. A. Rona

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

Jan 1, 1989

By J. A. Jankowski

The situation in the raw material market has brought into consideration the commercial exploitation of the mineral deposits on the deep sea bed and in particular the manganese nodules. They occur generally in depths of 4000-5000 m, partially covered or buried in bottom sediments. The deposits and their potential recovery have been intensively explored and researched during the past twenty years (Bischoff 1979, Halbach 1988, Padan 1990). Although the present market situation limits the rentability of deep sea mining on an industrial scale, the mining technology is being further developed in many countries. The stagnation phase in the deep mining issue allows sufficient time for conducting research on the precautionary protection of the deep sea environment and for consultation in the development of technologies with the least possible impact on it. The subject has gained in importance since autumn 1994, when the United Nations International Law of the Sea was signed. This also regulates human activities in international waters from the environmental point of view. As fields tests have shown in the past, even with the most modern technologies, mining of the manganese nodules will inevitably be accompanied by a resuspension of some bottom sediments. The generated sediment plumes will be further transported with the ocean currents and in the worst case form stable turbidity layers in different depths (Ozturgut 1981a, Baturin 1991). One of the problems of the environmental impact assessment is the estimation of the plume persistence before it eventually dilutes to approximately the ambient concentration level or settles at the bottom (Lavelle 1981a, Lavelle 1981b, Lavelle 1982, Thiel 1991a, Thiel 1991b). The aim of the research is to develop a numerical sediment transport model in connection with potential manganese nodule mining in a reference area located in the southeastern equatorial Pacific Ocean off Peru (Peru Basin, Discol Experimental Area). In this region, a German mining claim is registered and interdisciplinary field works of the TUSCH (German: TiefseeUmweltSCHutz, deep sea environmental protection) research group are carried out in order to obtain the required scientific background for evaluating of the deep sea mining impacts and to provide the necessary supporting data for the modelling (Thiel 1991a, Thiel 1991h).

Jan 1, 1995

By Alexey Musatov, Georgy Cherkashov

Based on geochronological data it was confirmed that hydrothermal discharge has an episodic character: active and inactive periods of the seafloor massive sulfides (SMS) formation alternate (Cherkashov et al., 2017). There is an assumption of correlation of the periods of magmatic and hydrothermal activity with the stages of glaciation (Lund et al., 2016). During the cold periods, the level of the ocean was reduced from 70 to 150 m depending on the glaciation scale (Spratt, Lisiecki, 2016). As a result, the hydrospheric pressure on the upper mantle decreased and could provide increased magmatic and hydrothermal activity (Lund, Asimow, 2011). This assumption is confirmed by the correlation of warming and cooling stages with increasing of hydrothermal input to the bottom sediment near hydrothermal fields. According to data (Lund et al., 2014, 2016; Middleton et al., 2015) the peaks of hydrothermal activity, expressed in the layers of metalliferous sediments at the East Pacific Rise and the Mid-Atlantic Ridge, roughly correspond to the last two periods of cooling (20 and 60 ka). To test this hypothesis, we tried to compare the sequence of warm and cold periods in the Pleistocene with the dating of SMS reflecting the periods of hydrothermal activity. Results SMS samples were obtained from 12 sites within the Russian Exploration Area at the MAR segment 12-20°N. The results of dating 198 samples by the 230Th/U method demonstrated the absence of correlation between hydrothermal activity periods in different hydrothermal fields (Cherkashov et al., 2017). It was proposed that each field has its own evolutions scenario. Considering this point, only the oldest SMS dating for each field which fixed the beginning of hydrothermal activity was selected for comparison with the cold/warming periods.

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 I. Yu. Melekestseva

The Semenov hydrothermal sulfide cluster (13º31´N), consisted of five fields (Semenov-1, -2, -3, -4, and -5), was discovered in 2007 in the 30th cruise of R/V Professor Logatchev [Beltenev et al., 2007; 2009]. The hydrothermal fields are located on a seamount composed of ultramafic and mafic rocks, gabbro, plagiogranite, and their altered rocks. The Semenov cluster is considered to be the largest sulfide accumulation in the Ocean with massive sulfide (MS) resources of about 40 million tons [Beltenev et al., 2009]. MS of the Semenov-1, -3, -4, and -5 hydrothermal fields are mostly characterized by marcasite-pyrite composition whereas rich copper-zinc MS with high Cu and Zn contents (11.37?19.33 and 5.89?18.32%, respectively) and anomalous Au and Ag grades (22?188 ?127?1787 ppm, respectively) were dredged only at the Semenov-2 hydrothermal field associated with basalts (13°31.13´N, 44°59.03´W; 2360?2580 m of depths) [Ivanov et al., 2008].

Jan 1, 2010