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By Jiahua Pan, Yanxiong Mei, Shuqin Liu, Rongfu Pei

Growth characteristics of Co-rich crusts from the Western Pacific have been approached. The thick crust shows 3 structural layers: compact upper layer, porous middle layer, and compact lower layer. The middle and lower layers have obviously different microscopic structure, color, and luster. Preliminary study of Calcareous nanofossils in one crust shows that the crust began to grow since Paleogene. The porous middle layer was formed from late Miocene to late Pliocene (Ca. 0.5 ~ 11.9Ma) and the compact lower layer was formed from late Paleocene to late Oligocene (Ca. 56.3 ~ 23.2Ma). The sedimentary hiatus of a 14.26Ma was observed between the middle and lower layers. The boundary between them to be Oligocene/Miocene (O/M) shows an important message on growth age.

By Dwight D. Trueblood

The Benthic Impact Experiment (BIE) is designed to address the effects of sediment redeposition prior to the commencement of commercial mining. The experiment is being conducted in collaboration with Russian scientists from the Yuzhmorgeologiya Association aboard the R/V YUZHMORGEOLOGIYA. Sediment resuspension and subsequent redeposition during manganese-nodule mining is predicted to be one of the primary impacts on benthic communities living on the abyssal seafloor. The redeposition thicknesses that will cause significant faunal mortality in the deep sea are unknown. Sediment redeposition could adversely affect abyssal benthic communities through entombment, or through starvation caused by food dilution and obstructed feeding. This spring NOAA conducted the main portion of the BIE experiment, blanketing the experimental area with varying thicknesses of sediment using the Deep Sea Sediment Resuspension System (DSSRS). The DSSRS was conceived by NOAA scientists, designed and built by Williamson and Associates, and is the critical piece of equipment used to generate the controlled sediment redeposition environment on the 4800-m deep abyssal plane. The DSSRS consists of an 1800-kg sled, 4.8 m long, 2.4 m wide, and 2.2 m high. The sled was towed and powered using an 8,000-m, 26-mm single conductor cable having a 3,000 VAC capacity. As the sled was towed across the bottom, mud was ingested through two rear-facing, 45-cm wide intakes using two 7.6-horsepower pumps, and discharged 10 to 20 m above the bottom through two 20-cm diameter riser hoses. Each pump was instrumented with optical backscatter sensors providing real-time information about the discharge concentration.

Jan 1, 1992

By David S. Cronan

The traditional method of deep sea manganese nodule exploration is to conduct grid survey and sampling on successively finer scales until a suitable deposit has been delineated. Clearly this is both time consuming and ultimately self-defeating if large areas of the ocean floor are to be explored on a human timescale. A conceptual deductive approach would be preferable if one could be found, as it would aim to outline areas of potentially economic nodules on the basis of easily measurable oceanographic parameters. An attempt to achieve this aim in the Central Pacific is outlined below. Nodule Distribution in the Central Pacific Ocean Maps of ore grade nodules in the Central Pacific show that they are confined to two zones trending roughly east-west which are well separated in the eastern Pacific but which tend to converge towards 170-180ºW. They follow the isolines of intermediate biological productivity in the surface waters, strongly suggestive of a biological control on their distribution. Within these zones the nodules preferentially occupy basin areas. Thus they are found in the Penrhyn Basin, Tokelau Basin, Central Pacific Basin, Clarion Clipperton Zone and Tiki Basin. Nodules in all these areas have features in common and are thought to have obtained their distinctive composition by similar processes.

Jan 1, 2003

By Leonhard Weixler

The Bauer company was founded in 1790 by coppersmith Sebastian Bauer in Schrobenhausen, a small town north-west of Munich. The original workshop business carried out works including repairs to church roofs and brew kettles. Later the company expanded its operations to encompass water pipe installation, which it continued through to the 1980s. In addition to installing water pipes it then also began drilling wells, which were sometimes constructed using very simple methods, such as tripod frames (Figure 1).

Jan 1, 2011

By P. E. Halbach

On June 26, 1988, the Jade Hydrothermal Field was discovered in the Okinawa Trough by the German RV Sonne. This research cruise has taken place within the scope of a German-Japanese cooperative project. The Okinawa Trough, located between the Ryukyu Island Chain and the east coast of China, is an active backarc-basin formed by extension within the continental lithosphere. The Ryukyu arc consists of a nonvolcanic outer arc, forming the main island chain and representing compressive highs of the Asian continental margin, and an inner arc with present-day volcanism in its northern part (Sibuet et al. 1988). The valleys and ridges of the trough are cut across by transverse faults, giving rise to younger volcanic intrusions. The Jade Hydrothermal Field was detected in a caldera-like structure. It is. located at about 27°15,0'N and 127°04,5'E with a maxi- mum water depth of about 1650 m. Data of heat flow measurements show a high anomaly in the cauldron basin with values ranging from around 100 to 800 mw/m2 (Halbach et al. 1989). The hydrothermal vent area was discovered in the northern part of the inside northeast slope of the cauldron in a water depth between about 1300 and 1500 m. We identified different varieties of hydrothermal

Jan 1, 1989

By Jelena Milinovic, Sofia Martins, Anna Lichtschlag, Sven Petersen, Fernando J. A. S. Barriga, Bramley Murton, Adeline Dutrieux

"The active TAG hydrothermal mound is one of the largest and better studied. Due to its size (one of the largest, known so far, in the Atlantic Ocean) and concentration of specific economic valuable elements, it might be considered for future exploitation due the increasing demand for raw materials. However, the discovery of several large inactive sulfide mounds, some partially buried under sediments may relieve this pressure. Exploration for such occurrences can, together with geophysical exploration tools, be accomplished by mineralogical and geochemical studies of those sediments.INTRODUCTION AND GEOLOGICAL SETTINGThis study reports the results from sediment samples collected during the Meteor M127 cruise on the TAG hydrothermal area in 2016. The Trans-Atlantic Geotraverse (TAG) hydrothermal field (Mid-Atlantic Ridge, 26°08’N) is located 2.4 km east of the main rift valley at depths of about 3650 m. The TAG hydrothermal field stands as an example of a massive sulfide deposit on a low-spreading ridge associated with an active detachment fault (Humphris et al., 2015).Associated with the TAG hydrothermal field are metalliferous sediments/deposits that can reach several meters in thickness (Metz et al., 1988). These sediments/deposits can be formed by hydrothermal plume fall out (buoyant and nonbuoyant), massive wasting of hydrothermal edifices (sulfide mounds and chimneys) and authigenic mineralization (Gurvich, 2006). By studying the grain size, mineralogy and geochemistry of the sediments it is possible to identify each type of sediments and find their proximal or distal distribution. The location of the gravity cores studied here is distributed along sediment ponds near inactive hydrothermal mounds [Three mounds area (B)], actively venting low-temperature mound [Shimmering mound (A) and Mir zone (D)] and an area of sediment accumulation [Central area (C)] (Rona et al., 1993) (see Figure 1)."

Jan 1, 2017

By Raymond A. Binns

The Eastern Manus Basin (EMB) contains three major active hydrothermal zones and a number of smaller occurrences of hydrothermal deposits, and can be considered as a regional-scale modern analogue for volcanic-hosted mineral fields on land. Unlike the central Manus Basin, a back-arc spreading zone with some MORB-like basalt-hosted massive sulfide deposits, the EMB is a pull-apart rift zone between two transform faults, where a basement of Eocene-Oligocene arc crust is being thinned by extension, with rapid sedimentation on the tilted fault blocks. Present-day submarine igneous activity in the EMB, with which hydrothermal activity is associated, has arc geochemical affinities and is related to subduction of the Solomon Sea Plate at the New Britain Trench. Overall, hydrothermal deposits in EMB are found with lavas ranging from picritic basalt to rhyodacite in composition, although the two major occurrences of massive sulfide are hosted by the more siliceous dacite and rhyodacite variants. Some volcanic edifices are central eruptions, mostly of porphyritic lavas or domes, while others are elongate ridges formed by fissure eruption in which the typically aphyric lavas were very fluid. Evidence for shallow-level fractional crystallisation controls of lava chemistry implies presence of subjacent differentiated intrusions or former magma chambers. Seismic tremor at one site during the nearby 1994 Rabaul eruption suggests magma movement in the chamber.

Jan 1, 1998

By Sofia Martins, Anna Lichtschlag, Sven Petersen, Fernando Barriga, Bramley Murton, Adeline Dutrieux

"Sediments in the vicinity of the hydrothermal seafloor massive sulphide (SMS) mounds are characterized by high concentration of metallic particles. They result from a long process of weathering of the primary mineral deposits and have been accumulated in depressions by mass wasting and hydrothermal plume fall-out. We present here the first results obtained on pore waters analyses of such sediments in distinct geological seafloor environments (in low-temperature hydrothermally active zones, on extinct hydrothermal mounds and in a remote depositional channel). Vertical concentration profiles suggest that the pore fluid composition is affected more by seawater circulation compared with hydrothermal fluid flow in all environments. The composition of pore fluids is affected by diagenesis and redox processes in the distal depositional channel where Mn2+ is released at depth with Cu2+.IntroductionMarine hydrothermal fields, hosting seafloor massive sulphides, are potential resources for future deep-sea mining and might become economic reserves for the industries. They are widespread at mid-oceanic ridges, arcs and back-arc spreading centers (Hannington et al., 2011; German et al., 2016). Sediments in the vicinity of these fields can contain unusually high concentration of Fe, Mn, Zn and Cu among other metal elements (Shearme et al., 1983). These hydrothermal, or metalliferous, sediments result from a combination of processes such as collapsing and weathering of chimney material, filling of the channels by turbidite-like mass wasting, in situ authigenic mineralization and hydrothermal plume fall-out (Goulding et al., 1998; German et al., 1990). The sediments contain important indicators reflecting the development of the hydrothermal systems. Because of their widespread distribution and metal content, they themselves can be considered potential mineral resources. Circulation of seawater through these deposits, however, often modifies the sediment composition by oxidizing the sulphides into oxyhydroxides and clays causing mobilization of the metals. To address the importance of alteration and diagenesis of these hydrothermal sediments, including the result of seawater circulation, we investigated the post-depositional processes occurring in the hydrothermal sediments at the TAG Hydrothermal Field (Mid-Atlantic Ridge, 26°N), focusing on the mobility of metallic cations in a number of different seafloor environments."

Jan 1, 2017

By Roger Amato

The 1982 United Nations Convention on the Low of the Sea includes provisions under Article 76 for extending a coastal State's jurisdiction beyond the 200-nautical-mile (nm) Exclusive Economic Zone (EEZ) and for establishing the seaward limits of sovereign rights over natural resources. Article 76 prescribes a set of methodologies for determining these outer limits based on physiography and sediment thickness. The methodologies were applied to each of the five continental* margin areas of the United States - Atlantic, Pacific, Gulf of Mexico, Alaska, and Pacific Islands-using existing digital hydrographic and geologic data. Figures 1 and 2 show the results of applying the methodologies to the Atlantic, Pacific, Alaskan, and Gulf of Mexico continental shelves. Figure 1 depicts the preliminary limits of each of the Article 76 determinations for the Atlantic and Gulf of Mexico continental shelves. The Atlantic limits were described by Carpenter, Thormahlen, and Amato (1995) at the 26th Underwater Mining Institute.1 The limits for the Alaskan continental shelves are shown in Figure 2. Additional areas beyond the 200 nm EEZ are highlighted. These include a small area north of the U.S. - Canada boundary, containing 7,000 km2, a large area north of Point barrow (395,000 km2), and a third area north of the Aleutian Islands (178,000 km2). The shelf between the first two areas appears to have sediments thick enough to qualify for the 1 percent method (Irish Formula); however, year-round ice cover has prevented acquisition of seismic or drill data. The entire northern Alaska shelf is prospective for petroleum The Gulf of Mexico (Figure 1) has two small areas beyond the EEZ known as "doughnut holes." One is south of Louisiana and includes part of the Sigsbee Escarpment, an area believed to have potential for oil and gas. Oil was found on Sigsbee Knoll in cores from Deep Sea Drilling Project's Leg 1 cruise in 1968. The Sigsbee areas contains about 6,000 km2. The second area is south of the Florida panhandle and contains about 12,000 km2.

Jan 1, 1996

By Michael J. Cruickshank

A workshop to examine recovery systems for selected strategic and critical materials in the U.S. National Seabeds for the National Defense Stockpile in the 21st Century was held in Hawaii September 26-28, 1991, sponsored by the National Science Foundation and the Marine Mineral s Technology Center. The National Defense Stockpile of critical and strategic mineral commodities is presently in a deficit position of more than 7.5 billion dollars. Current domestic reserves of some commodities are limited or nonexistent. As defined by the U.S. Bureau of Mines, "Reserves are select resources . . . which at the time of classification, can be mined at a profit." Occurrences of these minerals have been discovered offshore within U.S. jurisdiction. If the technology could be developed to convert these resources into usable ore reserves, our dependence on foreign ores could be greatly reduced. Preliminary estimates indicate that a ten-year program of ore reserves definition, with appropriate technical developments to demonstrate a recovery system, could cost less than half the amount authorized for stockpile acquisition in FY 1989 alone.

Jan 1, 1991

By V. V. Ivanov, A. I. Khanchuk, E. V. Mikhailik, M. G. Blokhin, P. E. Mikhailik

At present, marine ferromanganese crusts of seamounts are of great interest as a source of high-tech metals. The metals most enriched in these deposits are essential for a wide variety of green-tech, emerging-tech, and energy applications (Hein et al., 2013). There is a grate number data on the content of major and minor metals (thousands analyses). However, information on the content of such elements as platinum, gold and silver in the world literature is limited. The concentrations (N – number of analyses) of platinum, gold and silver in the Pacific are 418 ppb (N = 105), 35 ppb (N = 72), 1.02 ppm (N = 26), respectively, and in the North Pacific Prime Zone - 477 ppb (N = 66), 55 ppb (N = 13), 0.1 ppm (N = 4); in the Atlantic Ocean is 567 ppb (N = 2), 6 ppb (N = 2), 0.20 ppm (N = 18), in the Indian Ocean, 211 ppb (N = 6), 21 ppb (N = 2), 0.37 ppm (N = 9) respectively; (Hein et al., 2013). The northern part of the Pacific is poorly studied in this question. The samples of ferromanganese deposits (FMD) was recovered from the Govorov Guyot (Magellan seamounts), MZh-33 Guyot (Marshall Islands), as well as the Detroit Guyot (Imperor Ridge) and Yomei Guyot (Fe-Mn placer Holes 431 and 431A DSDP, Imperor Ridge).

Jan 1, 2018

The Brothers hydrothermal system is host to two very contrasting vent fields and to date, is the only known example of this kind for any submarine arc volcano in the world. Firstly, there is the NW caldera field. It is perched on the caldera walls and is up to 1,200 years old, and represents a more ?mature? system dominated by water/rock interactions, though there is also evidence for magmatic contributions to the hydrothermal fluids. It is host to relatively high temperature (~300°C), focused venting of metal-rich fluids. Large Cu- and Zn-rich sulfide chimneys occur at this site, with high concentrations (up to 90 ppm) Au apparent in some chimneys. Vent fluids of the NW caldera site show sub-seafloor phase separation is occurring at this site. Silica concentrations in these vent fluids are consistent with the vent fluid temperatures. Secondly, there is the cone vent field that is much younger, and which sits atop the summits of a main cone (the Upper cone) and an adjacent satellite cone (the Lower cone) that occur inside the caldera, near the southern caldera walls. This field is dominated by S-rich vents with vent fluids more diffuse, lower in temperature (<120°C), very gassy and acidic (to pH 1.9), and relatively metal-poor. Fluids of the cone site have Mg and SO4 concentrations higher than seawater values, indicating these ions have been added to the hydrothermal fluid and are not being depleted via normal water/rock interactions. Variability occurs between the two cone vent fields, with the diffuse discharge observed at the Upper cone volumetrically small and chemically different from the Lower cone. For example, from the vent fluid Mn, Li, Rb, and Cs concentrations, it is apparent that the Lower cone has experienced a lower degree of water/rock interaction (i.e., more reaction) than the Upper cone. Vent fluid pH is higher for Lower cone, consistent with more reaction and neutralization of acidic gases. Fe/Mn is lower at the Lower cone due to decreased Fe solubility at the higher pH. The lowest pH sample (1.9) is from the Upper cone that has 39.4 mmol/kg of SO4, consistent with input of magmatic SO2 and disproportionation to sulfuric acid and S or H2S. Thus, the Upper cone site could be interpreted to have a shorter reaction path and residence time between the point of magmatic degassing and the seafloor venting than the Lower cone site. Isotopic compositions of the NW caldera and cone vent fluids show evidence for magmatic water with negative dD and d180 values, while 3He/4He values show the Brothers hydrothermal system has shifted towards more magmatic conditions over the past several years with both sites affected by magmatic events. Similarly, vent fluid sulfide d34S values and those for sulfide minerals from NE caldera chimneys also indicate disproportionation reactions involving magmatic SO2. Minerals such as chalcopyrite, bornite, chalcocite, covelllite and euhedral grains of hematite occurring in high temperature chimneys from the NW caldera site are consistent with a more oxidizing, magmatic fluid, while bulk sulfide geochemistry data show evidence for a higher temperature suite of elements (e,g., Mo, Co, Se) associated with Cu-rich chimneys. Gold mineralization occurs in these high temperature chimneys and is associated with the most recent deposition of high concentrations of Cu, where d34S values are most negative. Geophysical evidence suggests that the top of a magma chamber occurs ~2.5 km below the caldera floor, beneath the cone site in the SSE quadrant of the volcano. Very low velocities of <1 km-2 are seen in the seismic data between the magma and the seafloor, and are indicative of gas release. Harmonic tremor data provide evidence for a 500 m pipe-like ?conduit? located above the magma chamber (and below the cone), linking it with the overlying hydrothermal system, providing a mechanism for magma-derived metals to enter the hydrothermal system under the cone site. The NW caldera and cone sites are considered to represent stages along a continuum between magmatic-hydrothermal and water/rock-dominated end-members.

Jan 1, 2010

By James M. Franklin

Research on modern hydrothermal systems provides quantitative measures of the processes of formation of hydrothermal fluids and of precipitation mechanisms from them. Studies of ancient deposits provide new information regarding volcanological processes that are related to the deposits, as well as data on their spatial and temporal compositional variations. Mew exploration guidelines result from both aspects of research. The most fundamental requirement for large metalliferous hydrothermal systems is an abundant heat supply for the upper two kilometers of the crust. This heat may come from a focused heal source (shallow-level subvolcanic intrusion), but ambient heat also may have provided enough energy for the reactions necessary to effect leaching of metals, especially where heat flow is particularly high (i.e. very large or high-temperature magmatic source, such as ultramafic environments). For most VMS systems, the majority of the metals were derived through leaching from footwall strata; in addition interstratal fluids may enter subvolcanic intrusions during episodes of magma a chamber "cracking," engendering some &apos;?magmatic" component in the hydrothermal system. Direct contributions of metalliferous magmatic fluid also may be significant from arc-related or back-arc felsic or alkalis systems. These latter contributions may form exceptionally high - grade portions in some deposits. Subvolcanic intrusions, which are excellent indicators of high heat flow and may have been the direct driving mechanisms for some stems undergo two stages of alteration: On intrusion emplacernent. fluids may rapidly enter and react with their mesostatic portions, evident in the sills in the Middle Valley. High temperature interactions caused albitization and destruction of oxides and sulfides, releasing metals. During terminal hydrothermal stages, the metalliferous fluid collapsed into the intrusions, forming disseminated and vein sulfides.

Jan 1, 1998

By Gregory Abramov

Borehole Mining (BHM), a remotely-operated waterjet mining method (Figure 1), has recently achieved two major milestones. It was, for the first time, applied to the extraction of manganese ore and at temperatures below freezing. The 1St stage is a demonstration test that is now underway just north of Emily, Minnesota, where the manganese ore is located 100-160m below the surface and its reserves are estimated to be in excess of 500,000 tons. The deposit was discovered over 60 years ago but, due to the fragile and sensitive nature of this Land of 10,000 Lakes (nickname for the State of Minnesota) and strong environmental restrictions, the iron/manganese reserves were deemed unrecoverable and remained untouched until late 2010 when permission for a single-hole demo-test was issued by the local Department of Natural Resources.

Jan 1, 2011

By Julian Malnic

Transplanting the steps used in exploring and developing mineral deposits on land into the marine environment will help developers. While familiar to oil and gas explorers and many other sea-based industries, the marine environment is so alien to the 90s terrestrial miner that the phrase ?terrestrial mines in the sea? is useful for reinforcing the fundamental parallels in mining sulphides at sea and on land. As on land, the processes of ?pre-feasibility study? and ?feasibility study? will determine the economics of mining a deposit. For many, the step into the sea can detract from the need to follow these familiar and recognised steps used when any new deposit is found on land. The technology to mine sulphides in the 1500 to 2000 m depth range exists. Currently, it is not found in a single, integrated and commercially available system but every element available to build such as system is. Transplanting the thinking of the leaders of the terrestrial mining industry into the sea will perhaps be the greatest challenge and reinforcing the basic steps of discovery - pre-feasibility through to feasibility is the best way to achieve this. After all on land one doesn?t ask ?Can we profitably mine it?? before one can authoritatively answer ?What have we found??. Research by Nautilus Minerals Corporation suggests that the mining of seafloor massive sulphides (SMS) will not only be profitable but potentially lower in both capital and operating costs than prevail in most terrestrial deposits. Nautilus is also acutely aware that with the first SMS deposits under title, it will be setting the standards for seafloor mining into the new millenium. Indeed, we have trained on us not only the eyes of the mining industry waiting to see if SMS deposits really do offer radically better returns, but other stakeholders of the sea and the capital markets. Mistakes by any SMS developer could land all developers in ?hot water?. The rush to exploit our deposits for economic gain will be tempered by ensuring there is adequate public debate and consultation for our environmental code. Failure in any facet of a marine mining development could set back the move to the ocean floor.

Jan 1, 1998

By Tetsuo Yamazaki

Metal market prices rose drastically in 2006, and most broke historical records as shown in Figs. 1-4. This increase has been basically driven by economic growth in Asian countries, especially China. The growth trend is expected to continue for several years. Then, India will follow the same growth trend. Their metal demands keep the price levels high for 20 years or more. One more additional important factor on the metal market prices is hedge funds come into the market. Japan imports all metals for domestic use from overseas. The amounts imported were 1.27 million tons in copper, 0.32 million tons in lead, 0.59 million tons in zinc, 0.20 million tons in nickel, and 1.18 million tons in manganese, respectively in 2006 (Source: http://www.jogmec.go.jp/j_resourse/index.html#03). Though mainly we import the concentrates and our domestic customer smelters take the part of metallurgical leaching, the payment necessary for purchasing the concentrates is estimated about US$ 10 billions in 2006. The payments in 2005 and in 2003 were about a half and a quarter of the 2006, respectively. Japan must have effective counter measures to reduce the future payments.

Sep 24, 2006

By Irina Dobretsova, Anna Sukhanova, Anatoly Kondratenko, Svetlana Babaeva, Sergey Andreev

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

Jan 1, 2017

By Yves Fouquet

Results of the two main drilling operations on hydrothermal fields demonstrate that the two dimensional submersible operations need to be followed by drilling expeditions to study the third dimension of hydrothermal systems and understand hydrothermal and ore forming processes. Two types of environments were drilled recently in basaltic environment on slow spreading ridge, and on a sedimented ridge. Similar work has still to be done and targets to be discussed in other environments such as back-arc basins for felsic rocks environments and slow spreading ridges for ultramafic rock environments.

Jan 1, 2011

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 Stephan K. Schwank

In mid 1993, Bauer Spezialtiefbau GmbH, based in Germany got the order to develop a sampling tool capable of penetrating all different types of seabed sediments including cobbles and boulders and into bedrock. BHP and their partners Benguela Concessions Ltd., had been convinced by the Bauer Trench Cutter Technology and a large scale test in Germany that this system will be the right one to fulfill their expectations for sampling the diamond area off the coast of Namibia. The technique of the tool is based on Bauer&apos;s standard cutter technology, which is widely used for the installation of cut-off and diaphragm walls all around the world. The two counterrotating cutter wheels with 12.1 tom torque each cut an area of 3 x 1.2 m (up to 3 x 3 m are possible). The material mixed with seawater was then pumped to the separation plant on board the vessel Geomaster with a capacity of approximately 700 m3/h. Cutter wheels and mud pump were mounted on a special cutter frame and connected by wire ropes and hydraulic hoses to the vessel. An outer frame with four telescopic legs supported the cutter vertically on the uneven seabed and allowed a controlled penetration of the tool up to 6 m into the diamond bearing ground. The tool required a total power installed of approximately 800 kW. All hoses, the 6-inch mud hoses as well as the hydraulic hoses, were stored and compensated on drums on board suitable for a water depth of up to 200 m. Launch and recovery of the tool was effected through the moon pool of the vessel and the 25 m high, special designed drill tower. The 65? to sampling tool had been commissioned in early 1994 in Cape Town. After intensive testing the sampling programme of more than 4000 holes could be successfully completed by January 1995.

Jan 1, 1998