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By R. W. Nesbitt

The TAG and Broken Spur hydrothermal mounds are located on the Mid Atlantic Ridge (MAR) at 260N and 290N (respectively). Both were initially discovered by exploratory work from surface vessels and both have since been investigated by submersibles. The discovery of TAG resulted from a NOAA Trans-Atlantic Geotraverse (Rona et al. 1975) which fortuitously sampled low temperature materials on the east wall of the MAR rift valley and follow up operations (Rona et al. 1986) located the high temperature (365°C) mound some 5km to the west. In 1994, ODP deep sea drilling (Leg 158) at over 3,500 metres of water recovered core to a depth of 150 m below surface (Herzig et al. 1998) and for the first time allowed a geological interpretation of an active mound. The Broken Spur mound was accidentally discovered in 1993 when sulphide fragments were observed on a deep-sea towed camera system (Murton 1993). Later that year, exploratory submersible dives by Alvin located the hydrothermal field and the area was again explored by submersible in 1994 and 1997. Despite the amount of work carried out, our geological understanding of the MAR mounds is limited. Much effort has gone into measuring fluid chemistry whilst practical difficulties have inhibited good geological mapping of the sulphide areas. It is clear from both TAG and Broken Spur that the mounds are not necessarily located in the areas of highest heat potential. Indeed, TAG is some 2 km from the rift valley axis and has been operational for several tens of thousands of years. Hence, heat availability is not a major consideration and the most obvious control is a structural one. Mapping on Broken Spur indicates a series of isolated vent-sulphide areas, concentrated around a minor graben. Their distribution, size and nature all indicate that they are residual parts of a much larger sulphide body which was at least the size of the present TAG field. The evidence is for a cyclical pattern of mound growth -mass wasting? rejuvenation and the Broken Spur mound appears to be in the rejuvenation stage of the cycle. Mound cyclicity must be related to the supply of hot water which itself is a function of the connectivity of fracture systems. Hence, we return to the theme that the major controls in mound development are structural ones.

Jan 1, 1998

By Freddy Pøhner

The paper describes recent advances in the technology for mapping of the seabed with acoustic instrumentation. These instruments are typically single beam echo sounders, multibeam echo sounders and high resolution sub bottom profiler. For the single beam echo sounders, new features for deep water mapping are described, as well as the possibility for combining investigation of shallow areas with side scan sonar and vertical echo sounding in the same instrument. Multibeam echo sounding technology for deep and shallow water is reviewed, and some new high resolution instruments using dynamic beam focusing is presented. The sediment profiling technology deals with a novel design for high resolution sub bottom profiling, based upon a Mills Cross transducer with resolution as good as 3 degree in its largest configuration and a frequency range of 2,5 ? 7 kHz. Remarkable features of the system are a very high ping rate even for deep water, and the capability to map buried objects or structures by several simultaneous beams. Some results obtained with the first installation on the French research vessel ?Beatemps Beaupré? are presented.

Jan 1, 2003

By Karstein Vestgard

During the last few years autonomous underwater vehicle (AUV) technology has evolved from concept demonstrators towards commercial products. The driving forces are the move for energy exploitation towards deeper waters, naval applications and the Internet driven need for more intercontinental underwater communication cables. Other applications emerging for the future will be within environmental research and monitoring and deepwater exploration. Deepwater developments beyond the continental shelf will require the same level of survey data quality and intervention access as established for shallow water. The potential for cost savings is two folds. Firstly, there is a reduction in the survey cost it self and secondly there is a considerable cost saving by avoiding over design of subsea installations due to lack of sufficient documentation of the field. In this scenario, there is an increasing understanding that underwater robotics and in particular AUVs will play an important role in future survey and subsea engineering work. The AUV as a free swimming underwater survey sensor carrier has several advantages compared to cable controlled ROV?s and deep towed systems: The paper prepared for the ?Underwater Mining Institute 2003? on Jeju Island, Korea will focus on the HUGIN AUV concept and field results to date.

Jan 1, 2003

By D. S. Cronan

Pitcairn Island, the last remaining British Colony in the Pacific Ocean, falls in the S.E. Pacific. Its location, on top of a hotspot volcano, suggests the presence of submarine hydrothermal deposits in its EEZ. Such environments are known to contain hydrothermal mineral deposits, as in the case of Loihi submarine volcano near Hawaii, and Macdonald and Teahitia-Mehitia seamounts in the South Pacific. The hydrothermal deposits in these areas are formed as a result of the interaction of seawater with hot volcanic rock, producing a hydrothermal fractionation sequence comprising sulphides of Fe, Cu and Zn, oxides and silicates of Fe and oxides of Mn. In 1988, a GLORIA survey from the RRS Charles Darwin confirmed the existence of recent volcanism within the Pitcairn Island EEZ. A later bathymetric and sampling survey by the FS Sonne of the region round Pitcaim Island revealed submarine volcanoes approximately 80 km ESE of the island. Hydrothermal mineral deposits were recovered from them, and comprise finely laminated crusts of Fe oxides containing up to 50% Fe, and laminated hydrothermal Mn crusts up to 5 cm thick. Both morphologically and chemically the latter are similar to those from mid-ocean ridge and island arc settings, containing up to 50% Mn, associated with sulphides, and represent first discovery of such deposits associated with mid-plate "hotspot" volcanoes. Massive sulphide deposits are thought to occur within the volcanic pile.

Jan 1, 1992

By David S. Cronan

Submarine hydrothermal mineralization occurs in at least three locations along the Hellenic Volcanic Arc in the Eastern Mediterranean Sea. Weak hydrothermal discharges occur off Kos and Nisseros at the eastern end of the arc and off Milos at the western end. In both cases the hydrothermal solutions are rich in iron and manganese and are precipitating iron oxides variably enriched in minor elements. This points to the likely presence of sulphide minerals at shallow depth below the sea floor at these locations. By contrast, at Santorini, in the centre of the arc, the hydrothermal discharges are much stronger and rate of deposition of the hydrothermal minerals much greater. Indeed, in one of the two hydrothermally active embayments off Santorini (Nea Kameni) hydrothermal deposits are accumulating up to five times as fast as in the Atlantis II Deep of the Red Sea. Radiocarbon dating indicates that these deposits have been accumulating for about 100 years. In the other embayment off Santorini (Palaea Kameni), hydrothermal deposition has taken place over a longer period (more than 1,000 years) but the deposits are not so hydrothermally enriched due to the simultaneous deposition of biogenic silica and detrital mineral with the hydrothermal deposits. The observed pattern of increasing intensity of submarine hydrother¬mal activity from the extremities of the arc towards its centre argues for additional hydrothermal mineralization on poorly explored areas of the sea floor between Milos and Santorini and between Kos and Santorini.

Jan 1, 1994

By N. Wang

The City of Honolulu mines sand from nearshore deposits for beach maintenance. The suction dredging operation creates a discharge plume which is carried by currents and other motions until it settles out of the water column. The dispersion of such a plume is influenced by distribution of particle size, as well as site dynamics. Interest in dispersion characteristics stem$ from concern about possible deleterious influences of such a plume on the nearshore environment. The behavior of such plumes has been modeled by Brandsma and Divoky (1976), as well as others. This study is an attempt to calibrate a plume model (modified from Brandsma and Divoky's model by Wang), using concentration, turbidity, and fluid velocity measurements of a small plume taken under field conditions. This calibrated model could then be used to predict dispersion characteristics of a much larger plume. Sand suction-dredged at a depth of 12m with a four-inch pipe and discharged at midwater was used to create a test plume closely simulating the conditions found during regular mining operations. Water samples containing suspended material were taken at varying distances from the discharge, from which concentrations were measured in the lab. Transmitted natural light measurements were used to provide estimates of turbidity. Current velocities were measured using current meters, as well as drogue-following methods. These data were then used to help estimate the vertical diffusion coefficient in the model.

Jan 1, 1991

By Porter Hoagland

It is well known that significant quantities of mineral deposits exist in the oceans. Most of these resources cannot yet be classified as economic "reserves" in the strict sense of the term, but they serve as backstops to deposits of identical minerals produced onshore. The prospects for the commercialization of ocean mineral resources will depend upon factors affecting both supply and demand, including, among other things, changes in consumption patterns, technological developments, new discoveries, developments in markets for complements and substitutes, and environmental regulation. In this presentation, we examine broad trends in mineral prices, as one of the most summary measures of the prospects for the commercialization of ocean minerals. Further, we report on any recent developments in the relevant product markets that may affect the potential for commercialization.

Jan 1, 1996

By Ning Yang, Yuxiang Chen, Ming Chen

An ultraviolet laser Raman spectrometer was developed to detect and analyze material components of seawater, seafloor sediment and rock at a depth of 7000m maximally. Wave length of the excitation resource of the spectrometer is set to 355nm, which can enhance eigen scattered intensity and detecting sensitivity, and avoid fluorescence interference. Miniaturization design was adopted for deep-sea application. Design of the optical system and pressure cartridge, material selection and seal design of the observation window, and design of the Lithium batteries are the key technologies in the procedure of research and development. The spectrometer was carried by a Lander sank to sea bottom of the Pacific's Mariana Trench for verification. During the sea trials, data acquisition for Raman spectra was conducted for analyzing seawater in the detection area, and the spectrometer was verified synthetically. According to the data, the spectrometer is stable and practicable with high resolution and precision, and it is appropriate to detect and analyze composition of substance under the tremendous ocean.

Jan 1, 2017

By L. B. Khershberg

According to geochemical specialization, cobalt-manganese crusts (CMC) of the Magellan Seamounts are rich in cobalt and manganese and are complex in composition. Besides cobalt, manganese, and nickel, they contain such components, as platinum, copper, molybdenum, and rare earth elements, which enhance the value of this material. Factors and conditions responsible for Co-Mn ore-genesis and processes of cobalt-manganese crust formation are described in a number of Russian and foreign geological papers. The study of ore-concentrating processes in the Magellan Seamounts helped to solve an important applied problem, namely to reduce the time needed to reveal the factors of CMC formation mechanism. The authors of this research found seawater over the described area of Magellan Seamounts to be stratified and to contain high concentrations of manganese, iron, cobalt, nickel, copper, lead, and zinc. Diagrams of suspended Co, Mn, Ni, and other components in seawater (0-5500 m), as well as medium concentrations of basic elements (Co, Mn, and Ni) in ore deposits of metallogenic levels of Magellan Seamounts, were found to coincide both on guyots and abyssal plains. Detailed geological study of guyots in the Magellan Seamounts (Dalmorgeo, IOAN, Roskomnedra, and others) revealed that medium Co-Mn crusts cover bedrock rocks in narrow ribbon-like bodies along the edges of bathymetric intervals 1300-1600 m, 1400-2000 m, 2000-2500 m, and 2500-3000 m.

Jan 1, 2004

By Derek Ellis

There are two environmental issues which have only recently begun to need planning in detail for marine mining. One is the environmental consequences of mine closure; the other is environmental terrorism. In principle it is not difficult to predict the pattern and rate of biodiversity recovery after mine closure on metalliferous depositional seabeds. 1-5 years to a self-sustaining community of organisms is a generalized guideline, depending on depth and particulate composition. The rate and pattern of biodiversity recovery on some metalliferous hard-rock habitats is far less predictable due to the patchiness and rareness of the habitat. Ecoterrorism at mines, whether on-land or marine, is now to be expected. A good example of resource industry ecoterrorism is the fire-bombing of logging and cement trucks in Oregon in 2001. But there have also been bombs at mine sites, as at Asbestos, Quebec. It is also possible to regard some resource-loss lawsuits as frivolous, hence forms of ecoharassment. Marine mining operations should take note of the development of environmental terrorism (and terrorism in general) and its various manifestations and impacts. Potentially these range from minor work stoppage inconveniences, to serious financial risk jeopardizing the economics of a mine, to jail for company executives, managers and environmental staff, and to harassment and killing of mine personnel.

Jan 1, 2005

By L. B. Khershberg

Marginal seas of the Russian Far East constitute the northwestern segment of the Pacific underwater belt distinguished by distinct metallogenic specialization of shelf-extended ore-bearing magmatic complexes and associated polycyclic mineralization. The coastal part of this vast region is known to contain both multiple placer manifestations and deposits, and non-metalliferous minerals. The latter are sedimentary deposits, the products of weathering, which contain re-deposited placer minerals in industrial concentrations developed on the shelf by certain geological processes. The shelf part of the Far Eastern seas is a seawater-filled continental margin. Complex geophysical mapping and drilling from ships of shelf sedimentary thickness and foundation has revealed the units of contemporary and ancient relief accompanied by formation of industrial concentrations of placer gold, cassiterite, titanium-magnetite, zircon, monzonite, and other components at different stages of placer formation. According to the information collected by prospecting by ?Dalmorgeologia? Co. Ltd. and other companies, placer-host structures within trans-placer-concentrating structures (land-shelf) are: shelf-extended river plains, contemporary and ancient shorelines, beaches, drained areas, spits, bars, detritus deficit zones, and terraces and bodies accumulated underwater in the areas where along-shoreline flows unload their detritus. They all could be used as criteria/signs for mapping and targets for placer prospecting.

Jan 1, 2004

By Sophia Katsouri

Hydrothermal circulation that produces sulfide deposits in the marine environment can also produce sulfide deposits in lakes. The major differences in terms of process are (1) in lakes the hydrothermal fluid is meteoric water of low salinity whereas in the marine setting it is saline and (2) the rocks that are leached of metals to produce the deposits are continental crust in one case and oceanic crust in the other. We have examined sulfides that are presently forming in two lakes ? Lake Tanganyika in east Africa and Lake Oyunuma in Hokkaido, Japan. Tanganyika is the second largest lake in the world and the second deepest rift lake, after Lake Baikal in southeastern Siberia. Two hydrothermal fields are known in its northern basin at Pemba and Cape Banza (Tiercelin et al., 1993). At Pemba, CO2 and CH4-rich, low temperature (53-88°C) hydrothermal fluids are forming decimeter-tall chimneys at 2-46 m water depth. Our microscopic and x-ray diffraction study of samples from the Pemba site reveal marcasite and pyrite to be the most common sulfides. Minor minerals include barite, hematite, bornite and chalcopyrite. Quartz and feldspar are also identified and were probably incorporated from the surrounding lake sediments. At Cape Banza, aragonite chimneys, up to 70 cm high, are venting fluids at 66-103°C.

Jan 1, 2001

By Harald Brekke

On 13 July 2000, the ISA adopted the Regulations on Prospecting and Exploration for Polymetallic Nodules in the Area. The first contracts for such exploration were issued by the ISA the same year. The duration of exploration contracts is 15 years, after which the contractors are expected to go into exploitation. In 2013, ISA with the LTC initiated the process for developing the regulations for exploitation, and are currently working on the first draft to put forward for the Council. In the meantime, the first seven exploration contracts have expired, and been given five years extensions in order for the contractors to get ready to apply for exploitation contracts. According to the current draft of the exploitation regulations, an application for an exploitation contract shall be accompanied by all data acquired during the exploration phase, a mining plan, a financing plan, and a set of environmental plans (i.e. an environmental impact statement, an emergency response and contingency plan, environmental management and monitoring plan, and a closure plan). All of these plans have to be based on substantial scientific and technical data and information. The mining plan requires geoscientific data regarding the mineralogy and grade of the nodules, and the physiography of the mining site as a basis for the consideration of critical aspects, inter alia for making reliable resource estimations, design the mining operations, and forecast revenues. The environmental plans require the input of a substantial set of bioscientific data and information on the exploitation technology in order to establish base-lines, and monitor and evaluate the effects of the mining operations. Under the exploration contracts, such scientific data have been acquired and reported on an annual basis to the ISA. Some testing of mining equipment and experiments on the extraction of metals have also been performed by some contractors. These scientific and technical data from the exploration phase will be the basis for the for the preparation of the studies, plans and documents required for the applications for exploitation. No time frame is specified for the preparations of an application but it must be assumed to take place before the expiration of the exploration contract.

Jan 1, 2018

By Will Roberts, M. E. Williamson

After verification of methodology and testing of prototype systems during 2005/06, Nautilus Minerals expanded their Papua New Guinea (PNG) operations to a full commercial exploration program in 2007. Included was the deployment of sensors and survey systems to locate, characterize and verify massive sulfide deposits with potential as mine sites within the tenements held by Nautilus in PNG. This presentation discusses some of the gear developed and operated during the 2007 PNG investigation.

By Robert G. Ditchburn, Albert Zondervan, Akira Usui, Hiroshi Shibasaki, Hajime Hishida, Ian J. Graham

Earlier reconnaissance geological survey and recent mineral exploration by the Geological Survey of Japan (now part of AIST), Metal Mining Agency of Japan (now part of JOGMEC) have revealed that hydrogenetic ferromanganese crusts are widespread over rock outcrops of the floor of the NW Pacific Ocean, south and east of the Japanese Islands, despite vigorous tectonic activity, such as subduction and backarc spreading. Deposition of ferromanganese oxides has occurred since at least the mid-Paleogene over the Philippine Sea Plate region and nearby.

By Ki-Hyune Kim

The Korea Ocean Research and Development Institute conducted its first exploration for deepsea mineral resources in 1983, and began a systematic deepsea prospecting in 1989 among Micronesian islands and in central and eastern parts of Carion-Clipperton fracture zones of eastern Pacific. With the arrival of R/V Onnuri in 1992, KORDI commenced a full-scale national program for nodule exploration. The total area surveyed by KORDI covers more than 1,500,000 km2. At the end of 1993, based on the collected data, Korea designated 300,000 km2 in the Clarion-Clipperton fracture zone as prospective mining area for manganese nodules, and accordingly, the government of Korea submitted the application in January of 1994 to the United Nations for registration as a pioneer investor and for the allocation of a pioneer area. This application was approved by the General Committee of the Preparatory Commission in August 1994. As a result, Korea became the 7m pioneer investor under the United Nations Convention on the Law of the Sea. KORDI is now carrying out detailed exploration survey and environmental studies in the registered area to fulfill required obligations to UN, and Korea will continue exploring the last frontier on earth. It is KORDI's unshaken calling to be successful in exploiting deepsea resources to provide our nation resources it lacks. It is not only a challenge to explore deepsea, but it is also our national mission to explore and succeed in our endeavor for future generation.

Jan 1, 2011

By P. C. Hollick

Two marine diamond deposits on concession 2b off Namaqualand along the South African Coast, have been systematically mined over the past year by the mv Moonstar. The two deposits, Smith?s Ulcer and Wedge Point Basin, are comparable in morphology, straddled the same water depths and have similar geology yet have given very different recoveries when compared to their respective grade models. These differences are best ascribed to the different style of mineralisation observed within the two deposits which has been directly controlled by the bedrock morphology. The smith?s Ulcer deposit has been formed in a metagreywacke bedrock displaying a strong north-south trending foliation which dips steeply to the west. Consequently the mineralisation is confined to narrow north-south linear trends with limited lateral extent (less than 5m) making extraction extremely difficult and somewhat variable. RE factors (recovered grade versus estimated grade) for this deposit range from 0.5 to 1.1. The Wedge Point Basin deposit is formed in a micaceous metaquartzite with a conjugate southwest northwest joint set, the southwest lineation being the more prominent, and structural foliation dipping gently to the west. The resultant style of mineralisation is confined to basinal features defined by topographical lows and is fairly lateral in extent (in order of 50m). Extraction of the mineralisation from this deposit is less arduous with recoveries more uniform, RE factors are frequently in the range 2 - 3. This style of mineralisation is more in line with what is to be expected from marine alluvial deposits, the nugget effect of diamond concentration being responsible for the high RE factor. The long narrow linear trends observed in Smith?s Ulcer demonstrably require a specialised approach in successfully sampling, modeling and ultimately mining.

Jan 1, 1998

By Marco Figoni

The increased interest on deep water minerals resources is a challenge for both mining and oil industry. The exploration and production of oceans minerals require a synergy between of different technologies. While mining industry is leading the dredging and processing part of the system, oil industry is contributing through development of ore lifting technology based on existing subsea knowledge. The paper presents an overview, based on published projects around the world, of different approaches to marine mining. Several exploration techniques and offshore production systems were already designed and assessed, all of them with apparently positive results. Exploration phase is well advanced and in continuous expansion allowing the discovery of increasing resources around the world of different nature but production can be considered to be in an early stage. Different from onshore mining, subsea operations require a closer cooperation with international and local authorities to preserve as much as possible the environment. There are still many uncertainties at respect and all the exploration process must be carefully evaluated to allow subsea mining to develop in a sustainable manner. Technically, mining at seabed was already demonstrated and the process is based on three main components, namely seafloor mining tools, riser and lifting system and production vessel support. This layout is based on the concept that ore must be disaggregated at seafloor first, transported to surface in form of slurry that must be dewatered before loading to be transported to processing plants onshore. The challenges are rising because the environment and safety must be taken into consideration as a priority when evaluating the efficiency of the system. The most critical challenges regarding the production operations, especially in deep water are the deep-sea excavation process, the transport of large slurry volumes, the slurry abrasivity, the power supply management and the subsea

Sep 14, 2011

By Siân E. Boyd

Studies of benthic recolonization in the aftermath of marine aggregate dredging in the U.K. and elsewhere are limited and are largely confined to experimental circumstances. Investigations of the physical and biological status of licensed extraction sites in the U.K. at various times following cessation of commercial dredging are very limited, and so judgments as to the likely progress towards environmental restoration and the time-scales involved continue to be based on predictions rather than real data. This field-based research programme was commissioned to enhance the understanding of processes leading to physical and biological recovery of the seabed following dredging, thereby aiding the identification of practices to minimize environmental harm at licensed sites, and to promote rehabilitation on cessation. The outcome of survey work will have the notable benefit of allowing questions about the present status of locations hitherto subject to commercial exploitation to be answered directly, rather than by inference.

Jan 1, 2002

By Kira Mizell, James R. Hein

Ferromanganese (FeMn) crusts form by precipitation of iron and manganese oxides from seawater onto a rock substrate and are therefore considered hydrogenetic in origin. Diagenesis does occur however, through the process of phosphatization. During phosphatization, abundant dissolved phosphate in seawater replaces carbonate in the detrital fraction as well as directly precipitates within the FeMn matrix as carbonate fluorapatite (CFA). This process is likely accompanied by the partial dissolution or replacement of the oxide phases [1]. As a result of these diagenetic processes, trace elements adsorbed on the oxides are released and can either be depleted or enriched in the phosphatized FeMn crust layers. Pb, for example, has been shown in sequential leaching experiments to associate with the iron oxyhydroxide (FeOOH) phase in purely hydrogenetic layers, while >95% of Pb in phosphatized crust layers is found in the CFA fraction [2, 3]. However, previous sequential leaching studies analyzed bulk layers of phosphatized crusts and only a few crusts, from the Pacific Ocean. Here we present concentration data for Pb and other trace elements in the CFA fraction leached from thin stratigraphic intervals of the phosphatized portion of FeMn crusts from the Pacific and Atlantic oceans to confirm consistency of trace metal association with CFA both throughout the phosphatized section and in two ocean basins. The Pb and trace element concentration data from this study will also be compared with data from non-phosphatized crusts from the global ocean. We can then determine the effect of phosphatization on the concentration of Pb and other elements of greater economic interest in FeMn crusts, specifically whether there is overall enrichment, depletion, or possibly even phase transfer of each metal in the phosphatized layers.

Jan 1, 2018