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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 Mayumi Ito

Seafloor hydrothermal deposits are found worldwide at 700 to 3,600 meters below sea level [1] and contain base and precious metals like Cu, Pb, Zn, Au, and Ag. Some deposits were found in the Japanese exclusive economic zone and the commercial potential will depend on developments in mining and treatment costs of onshore mines. The ores require mineral processing to become concentrate for the various metal smelters and the authors are investigating mineral processing treatments of collected samples. The collected samples were classified into three components (chimney, mounds, and substrate rocks) and they were separated using a RETAC jig. The mound component contains zinc, lead, and copper minerals and further separation using flotation was investigated. This paper introduces results of the mineral processing tests using gravity separation and flotation.

Jan 1, 2011

By Manfred Krutein

Ocean mining has a number of problems which are critical to its development: ? Political hurdles on national and international stages ? The worldwide economic situation, with the possibliity of a recession ? Financial difficulties in funding further work ? Technical problems for the development of ocean mining and transport subsystems ? Demands for technology transfer This paper touches the last two points and provides some thoughts for discussion and creative objectification. The many technical problems of ocean mining will be identified and some proposed solutions will be investigated relative to the state-of-the-art technology of ocean mining and nodule transport. An outlook into the future attempts identification of the steps necessary to eventually develop components for workable systems that are not only technically but also economically feasible.

Jan 1, 1978

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. K. Banakar, R. P. Rajani, A. R. Chodankar

The Afanasiy-Nikitin Seamounts (ANS) in Eastern Equatorial Indian Ocean (Figure 1) are shown to be the exposed part of the presently buried 85°E Ridge system under the Bengal Fan sediment and were emplacement around 75-80 m.y. ago (Krishna, 2003). The first recovery of ferromanganese crusts from the ANS was made during 1994, and the samples (Figure 2) provided important clues on the evolution of this seamount (Banakar et al., 1997).

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 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 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 Natalia Konstantinova, Kira Mizell, James R. Hein, Georgy Cherkashov, Amy Gartman, Pavel Mikhailik

INTRODUCTION Ferromanganese (FeMn) crusts from Mendeleev Ridge, Chukchi Borderland, and Alpha Ridge, in the Amerasia Basin, Arctic Ocean, are similar based on morphology and chemical composition. The crusts are characterized by two- to four-layered stratigraphy. The chemical composition of the Arctic crusts differs significantly from hydrogenetic crusts from the North Pacific Prime Zone (PCZ; Hein et al., 2013), such as a high mean Fe/Mn ratio (2.6 versus 1.3) and low Si/Al ratio (1.8 versus 4.0), with lower Mn, Ca, Ti, P, Ba, Co, Cu, Ni, Pb, Sr, and Zn and higher Si, Al, Mg, As, Li, V, Sc, and Th. Based on Arctic FeMn crust mineralogy, chemical composition, and growth rates, crust formation was dominated by three processes: Precipitation of Fe-Mn (oxyhydr)oxides from ambient ocean water, sorption of metals by the Fe and Mn phases, and fluctuating but large inputs of terrigenous debris (Konstantinova et al., 2017; Hein et al., 2017). The Mn and Fe phases are hydrogenous and reflect bottom ocean-water chemistry and the aluminosilicate phase contains stable detrital minerals such as quartz, feldspars, zircon, monazite, and clay minerals. A precise method of studying the distribution of elements in FeMn crust phases is sequential leaching that dissolves four mineral phases of different stability step-by-step, in the following order: easily leachable phase, mostly bio-calcite; manganese oxides; iron oxyhydroxides; and residual aluminosilicate minerals (Koschinsky and Halbach, 1995). Twelve bulk crusts and crust layer samples obtained from six hydrogenous FeMn crusts were studied. Those crusts were collected during Russian (Arktika 2012) and USA (HLY0805, HLY0905, and HLY1202) research cruises from different parts of the Amerasia Basin (Mendeleev and Alpha Ridges, Chukchi Borderland). Samples were chosen for the sequential leaching experiments based on their morphology, location, and water depth. Hydrogenetic crust (D07-33) from the Tuvalu EEZ, central-west Pacific Ocean, was included in the experiment for comparison. Recovery during the four-step sequential leaching, with respect to the bulk analyses, was between 80% and 120%.

Jan 1, 2018

By Raymond A. Binns

Exploration for high-value massive sulfide deposits on the ocean floor typically commences with a search for chimney fields in appropriate geological settings, followed by collection and assaying of standing chimneys. Individual chimney fields are generally too small in aggregate volume to constitute viable resources in their own right. Unless numerous small fields occur in reasonably close proximity, presence of plentiful sub-seafloor mineralization with acceptable metal tenor is the more likely requirement for potential exploitation. Expensive drilling is required to prove up mounds of collapsed chimneys, or dilatory sheets and veins or replacements of massive/semimassive sulfide (?stockworks? or ?manto?-like bodies) in underlying host rock. Where multiple targets have been defined, as many parameters as possible are desirable to help rank them for drilling.

Jan 1, 2011

By The DY125-33(Leg 2) Science Parties, Chuanshun Li, Xuefa Shi, Bing Li

"The slow-spreading Mid-Atlantic Ridge (MAR), with a length of ~1.26*104km (Bird, 2003), is the longest mid-ocean ridge on this plant. Separated by the large, left-stepping Equatorial fracture zones, it then be divided into two approximately equal-length parts: Northern Mid-Atlantic Ridge (NMAR, ~6292km) with an average spreading rate of 24mm/yr, and Southern Mid-Atlantic Ridge (SMAR, ~6332km) of 33mm/yr (calculated from PB2002 model, Bird, 2003). Previous works (e.g. Fouquet 1997, Hannington et al., 2011) suggest that slow-spreading ridge could support hydrothermal activities and further favorable for the development of extensive seafloor massive sulfide deposits (SMS). Unlike the NMAR for which large part has been explored for SMS (Hannington et al., 2011; Beaulieu et al., 2015), the SMAR is amongst the least hydrothermal explored spreading ridges until now (Haase et al., 2005, Beaulieu et al., 2015), though both of them show significant similarities in terms of spreading rate, ridge morphology, segmentation, etc. (Macdonald et al., 2001, Sandwell et al., 2014, Tucholke et al., 2008).Before this work, several hydrothermal cruises had been to SMAR since British and German programs starting in 2002, some hydrothermal fields, along with systematic geophysical data, were newly investigated, and types of geologic setting that can host hydrothermal activity were firstly identified (e.g. German et al., 2008; Haase et al.,2005; Haase et al.,2009; Devey et al.,2010; Schmidt et al.,2011).."

Jan 1, 2017

By Richard H. T. Garnett

The Chilean part of the archipelago of Tierra del Fuego, situated south of latitude 62o S, is within that country?s Región de Magallanes y Antártica, and separated from the remainder of Chile by the Magellan Strait. In recent geological history several phases of Quaternary age glaciers originating in the Andean and Dawinian Cordilleras eroded assumed primary gold deposits and entrained their related alluvial deposits. Piedmont glaciation extended to the east and south over m0st of the land and beyond the present-day coastline into extensive areas exposed during the resulting lowered relative sea level. During interglacials particulate gold incorporated unevenly in the widespread drift, till and moraines was fluvially released and concentrated into streams and flood gravels. Coastal erosion enriched various beaches with gold. From 1868 onwards Tierra del Fuego hosted a major gold rush whereby early, labour intensive, beach mining eventually developed into inland dredging. But continued mining activity was interrupted and then terminated by several external factors. Most miners, always seeking ?greener pastures?, joined the rush to the new discoveries in the Klondike (1896) and Nome, Alaska (1899). In 1904 the international boundary, established in 1881, became the subject of a major dispute not settled until 1984, The Panama canal?s opening in 1914 turned Tierra del Fuego, previously on the Pacific-Atlantic shipping route, into a remote backwater. World War II brought opposing foreign naval forces to the actual islands where most gold had been taken from the beaches. It also crippled the dredging industry which lost its coal supply and never recovered. Nevertheless, some small scale mining continues to this day.

Sep 14, 2011

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 Tatiana ?. Sedysheva, Vladimir V. Ivanov, Michail E. Melnikov, Irina A. Pulyaeva

"INTRODUCTIONHydrogenetic Fe-Mn crusts are ubiquitous in the ocean basins and play an important role in marine mineral-deposit research because of their widespread occurrence and high concentrations of valuable and rare metals. Directed research, which started in the last quarter of the 20th century, has provided significant results, with substantial amounts of data produced on Fe-Mn crusts structure, composition, and distribution in the global ocean [3, 4 - 8]. Now, commercial interests gain more and more attention. Mining systems are being developed which involve fragmentation of the crusts and their separation from the substrate. The effectiveness of such activities greatly depends on physico-mechanical characteristics of the crusts and rocks on which they form. This determines the importance of the engineering geological study of the objects.This article comprises the results of the engineering geological studies of the crusts samples (72 samples) and their underlying rock substrates (75 samples), which were carried out during the research cruises 6-06, 6-07, 6-08, 6-13 (2006-2013) on the Magellan Seamounts guyots in the Western part of the Pacific Ocean by the specialists of the State Scientific Centre Yuzhmorgeologia [10 - 13, 19, 20]. The authors of the article directly participated in the studies mentioned above.MethodsEngineering geological studies were carried out on board of the research vessel Gelendzhik and in the laboratories of NPA «Sevmorgeologiya». The studies involved the determination of the following parameters:"

Jan 1, 2017

By Alexander Malahoff

The summit of L_ihi submarine volcano changed dramatically after seismic activity beneath L_ihi during the month of August 1996. Bathymetric re-surveys of the L_ihi edifice using SeaBeam, Simrad and deep-towed Reson-Focus multibeam systems showed the presence of new north-south striking fissures, normal faults and a new pit crater located at the site of a former 300-meter high volcanic cone. Comparisons between the pre-1996 SeaBeam data and the new bathymetry show a net loss of about 100 million cubic meters of rock volume on the summit. This loss is localized at a new pit crater -- the 300-meter deep by 1,300-meter wide Pele's Pit. Submersible observations with Pisces V show the northern edge of Pele's Pit to be bounded by a normal fault located north of the site of the former Pele's Vents cone that has disappeared into the new pit crater. A new hydrothermal field, the Ikaika Vents, extending from a water depth of 1,311 meters to 1,287 meters has formed at the northeastern edge of the floor of Pele's Pit. Submersible observations of these new Ikaika Vents during September 1996 showed vigorous venting at the site with extensive white-colored bacterial mats hanging off the rock face above the vents. Follow-up mapping and sampling of the vent sites during August 1997 showed vent temperatures of up to 198°C, dense populations of vent shrimps around the vents and a centimeters-thick veneer of fine-grained polymetallic sulfide mineralization along the rock walls above individual vents. The mineralogy of the sulfides shows a barite, chalcopyrite, sphalerite, and pyrite composition.

Jan 1, 1998

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 S. Rajendran

The area of the Exclusive Economic Zone (EEZ) of India is about 2.014 million km2 and the resource evaluation of placer deposits is one of the objectives of Government of India. Placers are detrital metallic minerals found on beaches and in the near shore areas. Quantitatively more important are placer deposits of light heavy minerals such as zircon, ilmenite and rutile. Rivers and other drainage channels are the main carriers of the placers which contain heavy minerals like magnetite, ilmenite, garnet, zircon, monazite, rutile etc. The present beach as well as part of the shelf was land during Pleistocene as a result of the world wide lowering of the sea levels. The coast line shifted a number of times. Hence, the heavy mineral placers on the beaches are expected to extend to offshore areas chiefly with Pleistocene lowered sea level strands. India has extensive deposits of heavy mineral placers along the beaches. Placer deposits of heavy minerals occur in discontinuous patches on the beaches along many parts of the east and west coasts. Along the central west coast of India (12??N - 19? N lat.) the placer containing 14 - 17% ilmenite form an estimated reserve of 4 million tons. On the Ratnagiri coast of Maharashtra, the proportion of heavy mineral varies between 54 and 70% in the bulk samples, consisting mainly of 14 - 39% magnetite and 16 - 30% ilmenite. The National Institute of Oceanography (NIO) surveys show that the sediments off the central west coast consist largely of silty sand, sand silt and clay. The core samples show that a reddish brown clay overlay olive gray clay which in turn overlay heavy mineral rich sands. The heavy mineral concentration ranges upto 90% and has mainly ilmenite and magnetite with minor quantities of apatite, rutile, zircon, kyanite etc. Siddiquie et al. reported 42 - 75% TiO2 in the ilmenite.

Jan 1, 1998

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 Rolf B. Pedersen, Filipa Marques

The extension of the Mid-Atlantic Ridge north of Iceland has collectively been referred to as the Arctic Mid-Ocean Ridges (AMOR). The AMOR extends from the northern shelf of Iceland, to the Siberian shelf in the Laptev Sea, passing en route through the Norwegian- Greenland Sea, the narrow gateway of the Fram Strait, and across the Eurasia Basin. The AMOR is 4000 km long and is divided into six super segments: 1) the Kolbeinsey Ridge, 2) the Mohns Ridge, 3) the Knipovich Ridge, 4) the Molloy Ridge, 5) the Lena Trough, and 6) the Gakkel Ridge. After continental rifting at 60-50 million years ago, around 2.5 million km2 of oceanic seafloor has formed by seafloor spreading - resulting in the formation of the Norwegian- Greenland Sea and the Eurasian Basin. This northernmost part of the global ridge system is anomalous in several ways: The seafloor spreading takes place at an ultraslow rate (less than 2 cm/y) with spreading rates decreasing northward to around 1 cm/y at the Gakkel Ridge - which is the most slow-spreading ridge on Earth. As a result, the volcanic activity along the northern part of the AMOR is low, the oceanic crust is unusually thin (around 3,5 km at the Knipovich Ridge, Kandilarov et al.2010), and the rift valley is deep (average water depth > 3 km). In the southern part of the AMOR, the ridge system is affected by the Icelandic plume and a hot spot below Jan Mayen. The ridge-plume interaction results in higher volcanic productivity, unusually thick oceanic crust (9-11 km, Kandilarov et al. 2012) and shallow ridge segments (1500-100 m). The AMOR also display contrasting spreading regimes, whereas some super segments are dominated by orthogonal spreading (Kolbeinsey and Gakkel Ridge) others are characterized by highly oblique spreading (Mohns and Knipovich ridges). Some ridge segment displays asymmetric spreading, like the Mohns Ridge where core complexes preferentially form along the northwestern flank. Together these variations in ridge characteristics results in large diversity of hydrothermal systems and associated mineral deposits.

Jan 1, 2018

An extensive ferromanganese nodule field south of New Zealand (Fig. 1) has existed beneath the flow of the Deep Western Boundary Current (DWBC) and Antarctic Circumpolar Current (ACC) for at least the past 15 m.y. West of 174°E, between 59°S and 48°S, the field is 300-500 km wide, but east of 174°E, where current flow impinges on the eastern slope of the Campbell Plateau, the field narrows from ca. 200 km at 55°S to ca. 120 km at 51°S. This narrowing coincides with deflection of current flow eastwards, and consequent reduction in bottom-current velocity and eddy kinetic energy. Based on sea floor photographs, dredge samples and 3.5 kHz profile data, six distinct seafloor substrates are delineated, forming broadly parallel zones eastwards from the lowermost Campbell Slope (Fig. 2).

Jan 1, 2003