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By Isobel Yeo, Florent Szitkar, Sven Petersen, Sebastian Graber, Nico Augustin, Marcel Rothenbeck, John Jamieson

"INTRODUCTIONSeafloor massive sulfides (SMS) along mid-ocean ridges are often seen as a possible future contribution to a secure metal supply for global human needs. A growing interest over the past few years resulted in six national exploration licenses and one application pending, covering 10,000 km2 each, that have been brought before the UN International Seabed Authority (ISA) since 2011. Each contractor has to explore these 10,000 km2 within the 15-year runtime of the contract. However, the need to define areas that are not economically interesting is more pressing, as 50% of the 100 license blocks have to be returned to ISA after only eight years - hopefully areas that do not contain large and economically interesting SMS deposits. Current geochemical prospecting technologies, however, have mainly been developed for the search for active hydrothermal systems (e.g. hydrothermal vents and associated black smokers) that can easily be traced through physical and chemical anomalies in the water column (temperature, chemical variations of elements such as Mn, Fe, redox potential, and/or the particle concentration in the water column). Such plume surveys have been a primary tool for exploration of SMS systems, but they only identify active, and therefore mostly young and small hydrothermal systems. In a recent high-resolution AUV survey performed within the EU-FP7 funded project “Blue Mining”, we covered 47 km2 along the TAG segment of the Mid-Atlantic Ridge to test exploration methodology for fast and reliable exploration of larger areas of the seafloor for inactive seafloor massive sulfide occurrences using the autonomous underwater vehicle (AUV) “Abyss”."

Jan 1, 2017

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 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 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 Jonguk Kim

Submarine hydrothermal activity and mineralization related to island arc volcanism along the Tonga arc were explored during two research cruises in October 2009 (KODOS 09H) and February 2010 (KODOS 10H), respectively. In KODOS 09H cruise, geophysical survey, including multi-beam bathymetry, marine seismic and magnetic investigations, was performed on 10 volcanoes to find out possible structural discontinuity that can act as fluid pathway for formation of hydrothermal deposits at submarine caldera system. The result provided acoustic and seismic image maps and magnetic anomaly maps of targeted volcanoes. Then, detailed seafloor observation and sampling as well as deep tow side scan sonar survey were performed in KODOS 10H cruise on 5 volcanoes which are selected as targeted areas from the previous cruise. Among 5 targeted volcanoes, TA26 shows most extensive hydrothermal activity. Hydrothermal vents and alteration zone were observed on western caldera and summit of eastern cone of the TA26. Although only weak hydrothermal alteration was observed on eastern cone, mineralized fragments of chimney and mound were sampled from western wall of central caldera on TA25 volcano. On TA12 volcano, strong hydrothermal plume and alteration zone was detected during video tows operated between SW scoria cone and small ridge. However, only small amount of hydrothermal altered rocks were collected from TA12. Although hydrothermal activity and mineralization might be formed, supported by plume detection and result of geophysical survey, only weak alteration zones were observed on other two volcanoes (TA19 and TA22). The exploration area generally show shallow depth up to several tens of meters on summit where subsurface boiling of hydrothermal fluid might occur due to low hydraulic pressure, which can affect on styles of hydrothermal venting and mineralization process observed on Tonga submarine arc volcanoes.

Jan 1, 2010

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 Masaomi Kurihara, Seiya Kawano, Norihiro Yamajim, Satoshi Shiokawa, Nobuyuki Okamoto, Hironobu Sakurai

Seafloor polymetallic sulphides are distributed in the EEZ of Japan, including substantial deposits in the Okinawa Trough and Izu-Bonin back-arc basin. In this new frontier, the successful development of these resources in Japan is expected to bring about a new domestic supply of mineral resources. The initial stages of this development are authorized by the Basic Plan on Ocean Policy, approved by the Japanese Cabinet on April 26, 2013, and the Plan for the Development of Marine Energy and Mineral Resources, formulated by the Ministry of Economy, Trade and Industry (METI) on December 24, 2013. In 2008, the Japan Oil, Gas and Metals National Corporation (JOGMEC), commissioned by METI, began a survey and technological development programme for the development of the seafloor polymetallc sulphides (PMS) based on these Plans. The examination of four different fields: the evaluation of the amount of the resource, environmental assessment, mining technology, and processing & smelting technology, are concurrently promoted, aiming for commercialization as soon as possible. Based on the results of research for properties of geomorphology and marine environments of the target test sites in the Okinawa trough, which have been ongoing for several years, the preparation of the pilot lifting test included an in-situ excavation and crushing test conducted using test excavating and crushing systems.

Jan 1, 2018

By Masaomi Kurihara, Seiya Kawano, Norihiro Yamaji, Satoshi Shiokawa, Nobuyuki Okamoto, Hironobu Sakurai

Seafloor polymetallic sulphides are distributed in the EEZ of Japan, including substantial deposits in the Okinawa Trough and Izu-Bonin back-arc basin. In this new frontier, the successful development of these resources in Japan is expected to bring about a new domestic supply of mineral resources. The initial stages of this development are authorized by the Basic Plan on Ocean Policy, approved by the Japanese Cabinet on April 26, 2013, and the Plan for the Development of Marine Energy and Mineral Resources, formulated by the Ministry of Economy, Trade and Industry (METI) on December 24, 2013. In 2008, the Japan Oil, Gas and Metals National Corporation (JOGMEC), commissioned by METI, began a survey and technological development programme for the development of the seafloor polymetallc sulphides (PMS) based on these Plans. The examination of four different fields: the evaluation of the amount of the resource, environmental assessment, mining technology, and processing & smelting technology, are concurrently promoted, aiming for commercialization as soon as possible. Based on the results of research for properties of geomorphology and marine environments of the target test sites in the Okinawa trough, which have been ongoing for several years, the preparation of the pilot lifting test included an in-situ excavation and crushing test conducted using test excavating and crushing systems.

Jan 1, 2018

By Sang Joon Pak

Deep-sea mineral resources explored by Korea are categorized into mainly three types; manganese nodules, manganese crusts and seafloor massive sulfides. Manganese nodules have high Pt enrichment factors (EF=400, ore/crust ratios). Rare earth oxides (REO) contents from manganese nodules show from 0.037 to 0.302 REO% with mean value of 0.12%. Te and Pt are highly enriched in manganese crusts, displaying EFs of 10800 and 150, respectively. REO contents of manganese crusts are slightly richer than manganese nodules (0.013~0.387 REO%, average = 0.18 REO%). Seafloor massive sulfides deposits are featured by outstanding values of Se (EF=1300) well as In (EF=110). Au (0.8~26.3 g/t) and Ag (0.9~348.0 g/t) are another enrichment metals in SMS, although they belong to precious metals. Rare earth elements of SMS are meaningless as resources but REE are increasing in sediments overlying SMS. Heavy rare earth elements (HREE) from both manganese nodules and manganese crusts are typically higher than ones from land-based REE deposits. HREO grade and their portions of manganese nodules as well as manganese crusts are greatly similar to ion-absorbed type REE deposits in China, implying REE of subsea mineral resources are absorbed in nodules and crusts. Rare metals including REE could be exploited as by-production of commodities such like Ni, Co, Cu and so on. Rare metal resources from manganese nodules and manganese crusts are featured by low-grade and large scale deposits. Therefore rare metals in subsea mineral resources will add its economic values.

Jan 1, 2011

By Grigori Abramov

Borehole Mining (BHM) is a remotely operated underground and underwater method of extracting (mining) mineral resources by high-pressure water jets. It can be carried-out from the land surface, open pit floor, underground mine and floating platform or vessel. The method is currently in use in mining and exploration of such natural resources and industrial materials as: uranium, iron ore, quartz sand, gravel, coal, poly-metallic ores, phosphate, gold, diamonds, rare earths, amber and several more. Yet another application of Borehole mining technology is construction of subsurface collectors, ground walls and storage for compressed or liquefied gases, oil and other products.

By G. Rehder

The release of methane as free gas from the seafloor into the water-column well within the hydrate stability field is a natural process observed today in various ocean settings, such as the Cascadia margin, the Black Sea, the Guayamas Basin, and the Gulf of Mexico. The subsequent dissolution of gas bubbles into the water-column determines the vertical distribution of aqueous methane in the water-column and the upwards methane flux. Understanding this process not only is essential to describing the impact of natural deep-sea gas seepage, but also to assessing the hazard potential from blowouts and offshore exploitation activities, which are steadily expanding to greater ocean depths. Furthermore, the fate of methane from seeps contributes to scenarios of global change in the past and future involving the large scale destabilization of gas hydrates on a. We recently reported on the extended lifetime of methane bubbles within the hydrate stability field due to the formation of a hydrate skin (Rehder et al., 2002), based on in situ measurements of methane and argon bubble dissolution in the depth range 400 to 800 m. More recently, these observations were extended to depths from 900 to 1500 m. Single bubbles were injected from the ROV Ventana into an attached, back-illuminated, flow-through imaging box. The ascent of individual bubbles within the imaging box was recorded with Ventana?s HDTV camera system by piloting the 3-ton ROV upward, at the bubble rise velocity, for up to 400 m of vertical transit. Observed rise velocities were approximately 30cm/sec for all depths. Post-dive analysis of the HDTV video allowed detailed measurements of the bubble shrinking rates. The results of the earlier and new experiments lead to the following conclusions: (A) Methane bubbles released below the hydrate stability field showed markedly enhanced lifetimes, attributed to hydrate skin formation. The change in radius with time, dr/dt, varied from -7.5 micrometer/s above the hydrate stability field to about -1 micrometer/s at the deepest release depth. (B) Bubble lifetime within the hydrate stability field increased with distance in P-T space from the hydrate phase boundary. (C) Before hydrate skin nucleation, dr/dt for CH4 bubbles was comparable to dr/dt above the hydrate stability field. Although variable, the onset time for the hydrate skin effect to occur generally decreased with distance from the hydrate phase boundary (super-pressurization and super-cooling with respect to hydrate formation). (D) Even before the onset of the hydrate skin effect, a slight decrease of dr/dt with increasing depth was observed.

Jan 1, 2005

By James R. Hein

Rodriguez Seamount, located 150 km off the central California coast at the base of the continental slope, was studied using the ROV Tiburon aboard MBARI?s R/V Western Flyer, October 13-16, 2003. Fe-Mn crust and rock samples were collected along the SW flank of the seamount at water depths from 700 to 2100 m; bottom-water dissolved oxygen content (O2) and temperature were determined at each sample site. Fifty-three samples of bulk crusts, crust layers, and surface scrapes (~0.5 mm) were analyzed for 59 elements. Data allow for the correlation of crust compositions with precisely known water depths and seawater O2 measured at the actual site of sample collection. This is the first detailed study of Fe-Mn crust compositions in a region of strong continental-margin upwelling. Compared to open-ocean seamount Fe-Mn crusts, Rodriguez crusts have significantly higher (2-6 fold) mean concentrations of Fe (26.9%), Al (1.65%), Si (13.0%), Cr (82 ppm), Th (64 ppm), and Ag (1.7 ppm); and significantly lower (2-8 fold) mean concentrations of Ca, P, Bi, Co, Cu, Ni, Tl, and especially Te (8.2 times lower). All but one Fe/Mn ratio are >1 compared to <1 ratios for open-ocean crusts. O2 contents (0.35-2.03 ml/L) are nearly perfectly corrected with water depth and elements correlated with one are correlated with the other. The Fe-Mn surface scrapes represent 60-450 ka (mean 150 ka) of growth, whereas the dissolved oxygen contents of seawater represent an instant in time. Assuming that the entire sample set was affected uniformly by oceanographic changes, we suggest that correlation of elements with O2 may reflect oceanographic processes. O2 has a negative correlation with P, V, As, Fe, U, Be, Pb, Cr, Mg, Y, Bi, Te, and REEs (except Ce) and a positive correlation with aluminosilicate-hosted elements (Al, K, Rb, Cs). This later relationship is related solely to water depth, indicating that detritus shed down the seamount slopes accumulates in greater abundances in deeper-water crusts. Si/Al ratios indicate that the detritus includes a large component of biosilica produced by upwelling-mediated high productivity. These observations are supported by positive correlations of aluminosilicate-hosted elements with crust growth rates (range 1.2-13.0 mm/Myr). In contrast, other elements (Sr, Co, Mn, Mg, Te, As, Mo, V, W, U, Ti, Ni, REEs, etc.) are negatively correlated with growth rates. Growth rate has a weak positive correlation with O2. These compositional characteristics indicate that even though low-O2 seawater acts as a reservoir for Mn and associated elements and produces slow growth rates, which would allow for the concentration of elements and surface oxidation processes to occur, the high rate of input of detritus and high bioproductivity ameliorate the strong concentration of most metals. This dilution is significantly enhanced by the doubling of FeOOH in the crusts--the main cause of the generally high growth rates compared to open-ocean crusts. The high growth rates limit the oxidation of Co, Tl, and especially Te on the crust surface, which is reflected by their relatively low concentrations. Within the range of oxygen contents measured, O2 has less of an influence on crust chemistry than does the availability and incorporation of FeOOH and detritus.

Jan 1, 2004

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

By Jeremy Spearman, Mark Lee, Jon Taylor, Neil Crossouard, Bramley Murton

"SUMMARYThis paper describes challenges faced when executing a programme of monitoring to measure the dynamics of currents and sediment plumes at a seamount and the solutions identified to deliver the measurements. The study site was the Tropic Seamount, which extends some 3300m above the surrounding seabed and is found at the southern limit of the Canary Island Seamount Province. The purpose of the study, which forms part of the Marine E-tech project, was to provide information on the interaction of flows with the seamount and to assess the behaviour of sediment plumes that could be generated from potential seabed mining operations targeting the recovery of ferromanganese crusts. Since the crest of the seamount is submerged to a depth of 1000m, much of the work was undertaken using remotely operated and autonomous vehicles supported by measurements from the surface vessel. Despite only limited information on currents being available for planning purposes, the combination of short term forecasting using a 3-dimesional hydrodynamic model of the study area coupled with the collection and analysis of reconnaissance data collected during the first phase of measurement activities made it possible to plan and execute a number of detailed hydrodynamic experiments on the seamount crest. The results of these experiments have advanced the understanding of the behaviour of sediment plumes in the deep ocean and will ultimately improve our ability to manage the impacts which may arise from deep sea mining operations."

Jan 1, 2017

By Peter M. Herzig

In 1994 and 1998 the German research vessel R/V Sonne undertook detailed mapping and sampling of the largely uncharted offshore areas of the Tabar-Lihir-Tanga-Feni island chain in the New Ireland Basin of Papua New Guinea. The New Ireland Basin occupies a fore-arc position with respect to the formerly active Manus-Kilinailau arc-trench system and hosts a series of Pliocene to Recent alkaline volcanoes which are built on rifted Miocene sedimentary basement. Several of the volcanoes possess high-level porphyry stocks and active geothermal systems, including gold-depositing hot springs and the giant (40 million ounces) Ladolam gold deposit on the island of Lihir. On the southern flank of Lihir island, a group of three volcanic cones were discovered at water depths from 1.000-1.500 m. The volcanoes are located in a narrow zone of recent seismic activity and elevated heat flow (up to 100 mW/m2). The recovered volcanic rocks consist of fresh alkali-olivine basalts, clinopyroxene-rich basalts (ankaramites), porphyritic phlogopite basalts, and trachybasalts. Unusual gold-rich hydrothermal precipitates were recovered from the summit of the 600 m high Conical Seamount located only about 10 km south of Lihir Island. 1200 kg of sampled material systematically collected with a TV-guided grab from the top plateau (150 x 200 m, 1.050 m water depth) are intensely mineralized with pyrite, marcasite, minor sphalerite, chalcopyrite, galena, tennantite/tetrahedrite, and orpiment/realgar together with traces of anglesite, cerrusite, and amorphous silica in stockwork-like veins. Bulk samples of the vein mineralization consist mainly of clays, silica, and disseminated sulfides, and have an unusual high gold content ranging from 1.2-44.0 ppm Au. In some of these samples, grains of native gold (about 1 micron in diameter) were identified by SEM in pyrite and sphalerite. The gold-rich material also contains high concentrations of silver (up to 1000 ppm) and typical epithermal elements such as As (2.6 wt.%), Sb (0.2 wt.%), and Hg (34 ppm). Similar to epithermal deposits on land, which usually have only low base metal contents, the samples from Conical Seamount contain only minor amounts of Zn (max. 4.5 wt.%), Cu (2.0 wt.%), and Pb (2.0 wt.%). Many of the samples recovered from Conical Seamount are virtually identical to the gold ore at Lihir.

Jan 1, 1998

By Sup Hong

A pilot mining robot, named MineRo-II, has been developed by KIOST during 2011-2012. The pilot scale was defined as 1/5 of the commercial mining capacity, 1.5 million dry-tons of nodules per year. The development purpose of MineRo-II is to use for the pilot mining test planned in 2015. MineRo-II was designed to be self-propelled by electric-hydraulic power and remotely operated in real-time from aboard. The main operational functions are crawling on seafloor, pick-up and crushing of nodules, discharging nodules out to buffer. Prior to MineRo-II, a test miner (MineRo-I) was developed in scale of 1/20th in 2007, and performed two times sea trials in 2009 and 2010. The results of performance tests were evaluated and utilized for the concept of MineRo-II. The design concept aimed at the expandability of the mining capacity based on modularity of configuration, maintenance simplicity and multiplicity of backup solution. The pilot-scale mining capacity is achieved by four pick-up modules of each 1m wide, which are moving forward with robot vehicle and sweep the nodules entering below the pick-up heads. Principally, by adding the pickup modules in lateral dimension the mining capacity may increase linearly. MineRo-II was designed and constructed in unit-module wise. The robot consists of two unit-modules having an identical mechanical and hydraulic configuration. Each unitmodule has two tracks, two pick-up devices with attitude control devices, two crushers, one discharge pump, and one hydraulic system. Two unit-modules are connected by one loading frame and integrated by electric-electronic system. Two thrusters for control of the

Sep 14, 2011

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 Timothy F. McConachy

Between April 2000 and April 2002, the Commonwealth Scientific and Industrial Research Organization (CSIRO) Division of Exploration and Mining has led 6 research expeditions totalling 160 days ship time in waters of Papua New Guinea, Vanuatu, Solomon Islands, Indonesia and Australia. Five expeditions were undertaken aboard the Australian research vessel Franklin following successful competitive research proposals, and the sixth used the Indonesian vessel Baruna Jaya VIII (see Table 1). In addition, two CSIRO participants joined JOIDES Resolution for the Ocean Drilling Program Leg 193 in the Manus Basin of PNG. The major scientific objective underpinning these expeditions was to locate and study present-day seafloor and sub-seafloor hydrothermal ore-forming activity in order to develop improved methods of exploring for ancient mineral deposits on land that originally formed by similar processes. The research has been supported financially by a number of Australian-based mineral companies, by Australian international aid agencies, and by appropriation funds from CSIRO, and was conducted in collaboration with researchers from Australia, Indonesia, Portugal, New Zealand, United States of America, South Korea, and the host nations. Building upon earlier successes in the 1986-1997 PACLARK-PACMANUS programs in the Woodlark and Manus Basins of PNG, we have sought to examine a wider range of geological settings in which ancient orebodies are inferred to have formed, including both volcanic and sediment-hosted environments. We have now visited volcanic arcs, fore-arc and triple-junction related submarine volcanoes, and back arc basins associated with convergent plate margins in the SW Pacific and SE Asia, as well as conceptual Mississippi-Valley-type targets associated with warm seeps at passive margins in the Great Australian Bight (see Figure 1). Surveys ranged from northern Sulawesi via far western Bismarck volcanic arc near PNG-Indonesia border, through the eastern Manus Basin and the Tabar-Lihir-Tanga-Feni chain in PNG, the western Solomon Islands festoon, the San Cristobal arc, parts of the Vitiaz arc, to the northern and southern New Hebrides arc in the Solomons and Vanuatu.

Jan 1, 2002

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&apos;N and 127°04,5&apos;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 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