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By Øystein Sture, Kurt Aasly, Ben Snook, Sigurd A. Sørum

INTRODUCTION Efficient exploration methodologies for base metal deposits have huge benefits for future deep sea mining endeavours, and underwater hyperspectral imaging (UHI) has been variably demonstrated to have applications in the identification and characterisation of mineralisation on the seafloor for both nodules and seafloor massive sulphides (SMS) (Dumke et al., 2018 and 2017 respectively). Due to growing resource requirements (Singer, 2017), SMS deposits are considered to be increasingly significant sources of copper and zinc, as well as silver and gold. This style of mineralisation is currently occurring at active hydrothermal vents (black and white smokers) but now-inactive sites also have the potential to be large mineral deposits. As such, the development of novel methodologies to detect both on-going and extinct mineralisations are of high importance. Geological setting During the MarMine cruise (Ludvigsen et al., 2016), non-mineralised host rock, low grade ore and high grade ore grab samples (Snook et al., 2018) was collected by ROV from the Loki’s Castle deposit (Pedersen et al., 2010), located on the Mohn’s/Knipovich junction on the ultra-slow spreading Arctic Mid-Ocean Ridge (AMOR), at a depth of approximately 2300 m. This material has been characterised as part of the MarMine project (e.g. Snook et al., 2017), and, by imaging compositionally constrained material, the measured hyperspectral responses can be used to generate a library for identification of deposits on the ocean floor. UHI technology Remote sensing with hyperspectral and multispectral technologies has seen wide use in prospecting for ores and hydrocarbons on land (Van der Meer et al., 2012). Iron oxides and sulphides have low blue reflectance and high red reflectance in the visible spectrum. The ratio between these two pairs has been used in exploration for terrestrial deposits of hydrothermal origin (Sabins, 1999). This discrimination typically also includes wavelengths exceeding the visible spectrum (1.5µm – 2.5µm). These wavelengths are typically not utilised underwater because infrared wavelengths and higher are rapidly attenuated in water. However, discrimination based on the full shape of the spectral response in the visible light (350nm – 800nm) may still be possible (Bolin and Moon, 2003). Resolving the endmembers from the spectral responses requires prior knowledge about the optical properties of the materials, i.e. their reflectance. These reflectances can be obtained in a controlled environment, where the spectra of the lamps, wavelength- dependent attenuation in water and scattering of light can be accounted for (Johnsen, 2013).

Jan 1, 2018

By Robert Goodden

It is well known that diamonds are found in Kimberlite pipes within the earth’s crust and are also discovered where erosion has released them to be concentrated by rivers in trap sites within alluvial gravels. Few people are aware however, that diamonds are now being found in significant quantities at sea. And that the rugged marine environment has ensured that the quality of diamonds in the sea is predominantly gem quality. Shortly after intrusion of Kimberlites into the host rocks of the karoo in the Cretaceous period massive erosion occurred when torrential rivers carried diamonds from their Kimberlitic source rocks down the rivers and into the sea. In the sea they have been subject to a transporting and concentrating dynamic, which has deposited them in trap sites along the West Coast of Africa for hundreds of kilometers. In the last 60 million years the sea level along the West Coast has varied in steps from the current sea level to – 300m. With time at each beach level the sea has reconcentrated the diamonds previously carried down. These old beach levels exist at roughly 10 meter intervals. Each previous sea level now provides a target for marine miners. Marine diamond mining was started 46 years ago by the first pioneer, a Texan, Sammy Collins. Collins brought the potential of marine diamonds to the attention of major mining companies. With now outmoded technology Collins had days when he recovered pockets of high grade gems worth several million dollars; an excitement hard to equal in any walk of life. Amongst marine miners there is still a strong pioneering spirit but the industry has matured and now aims to consistently produce over two million carats of gems a year. The potential resource is huge stretching up to 30 kilometers offshore along the West Coast of Africa from South Africa to Angola.

Sep 24, 2006

By Andrea Koschinsky

Ferromanganese crusts have traditionally been considered a potential ore for Co, whereas ferromanganese nodules have typically been considered a potential ore for Ni and Cu. However, both nodules and crusts sequester high concentrations of many metals (Table 1) from sediment pore waters and seawater, many of which are essential for high-tech applications. The resource potential of these rare and valuable metals is poorly known and they are the subject of considerable current research. The need for adequate and dependable supplies of these metals is essential for the development of new technologies. The rare-earth elements have recently received much attention in the scientific and popular press because of their use in so many high-tech applications and because more than 95% of the production comes from China (e.g., Service 2010); consequently, there is concern about the possibility of a significant decrease or even curtailment in exports from China. The lack of a primary source and the inadequate supply of Te have prohibited the development of a Cd-Te photovoltaic solar-cell industry (Hein et al. 2010). Inadequate supplies of many of the elements listed in Table 1 are limiting the development of key high-tech industries, forcing the use of alternative metals that [ ] may result in less efficiency or less favorable properties for a product. The rare-earth elements, Te, and other elements listed in Table 1 occur in high abundances in marine hydrogenetic and diagenetic ferromanganese deposits. Here, we look at the mechanisms by which these rare and valuable metals are incorporated into different genetic types of marine ferromanganese deposits.

Jan 1, 2010

By Frank Manheim

The purpose of this presentation is to review the history of offshore non- fisheries resource development since World War II, as an introduction to a planned symposium on offshore resources scheduled for the 1996 UMI Conference. After World War II the United States became the leader in offshore oil and gas production, deep ocean drilling technologies, offshore terminals, platforms and production systems, and natural gas recovery and transport. Wartime skills in acoustic profiling and antisubmarine warfare were transferred into commercially important geophysical exploration techniques. The application of ocean drilling and geophysical techniques permitted the recognition and elucidation of plate tectonics patterns, development of seafloor spreading theory, and the transformation of our knowledge of seabed and subseabed strata. After John Mero's studies and recommendations for developing marine manganese nodules in the late 1950's interest in nonfuel minerals grew rapidly. The formation of international deep sea mining consortia in the 1960's was accompanied by a flurry of ocean engineering development, minerals prospecting and associated environmental studies The Santa Barbara Oil Spill of 1969 resulted in a moratorium on both offshore energy and minerals leasing by the Depart- ment Interior, and catalyzed the development of new Federal legislation in 1972. In 1973 the offshore energy moratorium was lifted in response to the Arab oil embargo, and offshore energy activities surged for a time. Minerals were reopened to leasing following President Reagan's 1983 executive order implementing a 200 mile EEZ. Although interest was spurred by

Jan 1, 1995

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 Philomene Verlaan

Analysis of the relationship between environmental parameters and the content of Mn, Ni, Co, Cu, Fe and Zn in ferromanganese crusts permits improved identification of locations to prospect for crusts with commercially valuable concentrations of these metals. In this study we asked whether a statistically significant relationship exists between primary productivity of the overlying surface waters, the concentration of O2 in and depth of the O2 minimum layer on the metal content of non-hydrothermal ferromanganese crusts in the Pacific Ocean between 130o W and 175o E and 0o to 30o S (the study area). To further develop the interpretation of the results of the statistical analysis and to assess in detail the geographical expression of these parameters in terms of metal content in crusts, a geostatistical technique (kriging) was used to generate contoured values for metal content, primary productivity and O2 concentration in and depth of the O2 minimum layer in the study area.

Jan 1, 2001

By Valcana Stoyanova

Data and information for this study were collected in June-July 2009 onboard the RV Yuzhmorgeologiya in the area covers about 7000 km2 in the eastern part of the CCFZ between 10º05? - 10º55?N and 119º25? ? 121º08?W. In accordance with the IOM research program the cruise was intend to acquire both geological and environmental data and information necessary for delineation of nodule deposits and also data for identification of the baseline of benthic ecosystem. Having implementation of its 15-year plan of work for exploration under the contract with ISA, current activities of IOM were focused on nodule fields within prime areas that could be mined in the future. Bottom photographs obtained by towed deep-sea vehicle NEPTUN along 6 profiles with common length about 300 km (Fig. 1). In total, about 11,500 digital photographs (what cover approximately 40,000 m2 of the ocean floor) were analyzed for assessment of nodule coverage and investigation of megafauna (animals, visible in photographs, the dimension more than 2 cm). The giant single-cell organisms Xenophyophorida were the most multiple animals in seabed photographs. Their number on the site area averaged 1187 ind/ha. However, the vertical camera position does not allow counting all xenophyophorids, therefore their valid number is represented 10 times more. According to all available information these protozoans play the relevant role in assemblage of deep-water environment, giving for other animal groups an [ ] additional source of nutrition and a substratum for settlement and attachment. The ophiuroids are found in assemblage with xenophyophorids in many cases, standing on a sediment at their base.

Jan 1, 2010

By Robert M. Owen

The rare earth elements (REE1s; atomic number 57 -71) exhibit a coherent chemistry, are widespread in nature, and tend to occur in characteristic concentrations in different geochemical phases. Because of their predictable chemistry, the REE's-are highly useful as indicators or tracers of geochemical processes, and are often used as such in investigations of the genesis of terrestrial ore deposits. However, analogous applications of the REE's to the study of marine mineral deposits have been constrained by our limited understanding of the marine geochemical cycle of these elements. For example, a continuing area of uncertainty in this regard involves the so-called "REE Mass Balance Problem." This problem refers to the fact that detailed geochemical mass balance calculations typically predict a significant imbalance for the REE's; i.e., the calculations predict that REE removal rates from seawater are 11-18 times greater than their input rates. Yet all other chemical considerations indicate that the REE budget should be roughly in balance. Recent studies at The University of Michigan suggest the solution to this problem lies in understanding the the role of seafloor hydrothermal activity in the marine budget of the REE's. Geochemical analyses of hydrothermal sediments from two Pacific sites (East pacific Rise at 19°s and the Southern Juan de Fuca Ridge at 45°N) clearly show that the REE component of hydrothermal sediments is primarily acquired via scavenging from seawater. Iron oxyhydroxides, which form as precipitates when hydrothermal solutions are debouched onto the seafloor, are the active scavenging agent. Although the REE content of hydrothermal sediments generally increases with increasing distance from the rise crest, this increase is especially pronounced for sediments deposited below the lysocline,

Jan 1, 1989

By Gerald R. Dickens

Massive sulfide ores and Fe-Mn oxyhydroxide precipitates represent two extremes of a spatial continuum of hydrothermal deposition along oceanic ridges. Elemental variations across this continuum are of interest to economic geologists as a prospective geochemical exploration tool. Theoretical considerations suggest that certain physical and chemical parameters can be used to model compositional variations within the far-field (i.e., Fe-Mn oxyhydroxide) component as a function of distance from ridge axis; however, testing and verification of such models generally has been precluded because the few available distal hydrothermal sediment sequences have been sampled at low resolution and/or are highly diluted with biogenic components (e.g., siliceous and calcareous tests). Recent ocean drilling (ODP Leg 145; Sites 885/886) in the North Pacific successfully recovered an extensive record of "biogenic-free" distal hydrothermal precipitates from an area approximately 60 km south of the Chinook Trough at longitude 168.1 °W. Geophysical and geomorphological evidence suggests the Chinook Trough is the southern lithospheric scar marking initiation of late Cretaceous north-south rifting, implying that recovered hydrothermal materials record distal hydrothermal precipitation from the now-subducted Kula-Pacific spreading ridge. The Chinook Trough hydrothermal sequence is a continuous 15 my record of "biogenic-free" hydrothermal Fe-Mn oxyhydroxide precipitation mixed with eolian clays. It was deposited during the late Cretaceous, early Paleocene (80-65 Ma) as the perpendicular distance from ridge axis increased from 75 to 600 km. A high-resolution geochemical analysis of this hydrothermal sequence reveals distinct trends for the up-core (equivalent to increasing distance from ridge) distribution patterns of Fe, Sc, As, and rare earth elements (REE). Iron concentrations exhibit an S-shape distribution pattern with respect to increasing

Jan 1, 1994

By Steven D. Scott

Several polymetallic sulfide deposits (copper, zinc, f lead, silver, f gold) presently exposed at the surface of the ocean floor are of sufficient size and apparent grade that they will someday be seriously considered as mineable resources. Responsible ocean mining may have some real environmental advantages over land mining, although they both share the same downstream problems caused by smelting and refining. The area of disturbance for an ocean mine would be much less than for an equivalent sized deposit on land around which considerable rock has to be excavated in order to get at the ore. Acid mine drainage, a very serious problem in land ming, would not be a concern in the alkaline and oxygen deficient environment of the deep ocean. There would undoubtedly be loss of habitat for some marine organisms but this could be minimized by mining deposits that are no longer hydrothermally active and therefore support little life. The risk of severe corrosion and thermal damage to the mining equipment at hydrothermally active sites would probably preclude their recovery in any event. The scientific community and environmental advocates should take advantage of the long lead time before ocean mining commences to insure that the environmental mistakes of the past, as encountered in some land mining, are not repeated. In order to fully understand and thereby mitigate the consequences of recovering seafloor sulfides, test mining of a small deposit using the German-designed high capacity television grab, preceded and followed by detailed observations of the mining site from a submersible, is proposed.

Jan 1, 1992

By Ning Yang, Sup Hong

INTRODUCTION Metal components contained in deep-seabed mineral resources are being highlighted as “energy metals”, which are widely utilized in the entire fields of energy: harvesting and generation, storage and transportation, and saving. Those are mostly trace and rare metals, and rare earth elements as well: manganese, nickel, cobalt, copper, molybdenum, tellurium, selenium, platinum, etc. Toward low carbon society, for global sustainability, the role of metals and minerals is growing up in industries of energy and transportation [1]. In this context, the production and supply of energy metals from deep seafloor have to be approached also based on sustainable development. In deep-seabed mining activity, the sustainability is focused on potential impacts on ecosystems in benthic area and water column. The environmental impacts in deep-seabed mining are caused basically by intervention in benthic zones and transportation of materials. Those are, in particular, removal of benthic habitats, generation and dispersion of sediment plumes, surface transportation of seawater and sediment, tailing from mining vessel, sound and light noises, and chemical leakage, etc. This paper is aiming at fundamental guidance towards sustainable mining of polymetallic nodules.

Jan 1, 2018

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 Alexander Malahoff

The new ship-submersible system with R/V Ka'imikai-o-Kanaloa as a mothership and the PISCES V as the submersible completed its first season of dives. The dives involved deployment of the PISCES V in the Hawaiian Islands between the months of July and October 1996. Submersible deployments up to depths of 2,000 meters in sea states up to a high three were made. The new hook and clasp deployment and retrieval connection for PISCES V to the telearm was shown to be an effective system for handling the PISCES V with the A-frame. The shipboard multibeam survey and seawater sampling capability proved to be especially effective in re-mapping the summit of the submarine volcano Loihi following a major volcano-tectonic event and for following the source and configuration of the new hydrothermal plume. Following the earthquake swarm of July 17 to August 18,1996, major changes in the geological setting of Loihi submarine volcano took place. Prior to the seismic event, the geology and structure of the summit of Loihi was represented by a platform-like area 8,100 meters long and 5,400 meters wide enclosed by the 1,200-meter depth contour. The summit was characterized by the presence of two prominent pit craters and eastern and western crater located at water depths of 1,100 and 1,370 meters, respectively. A hydrothermally active volcanic cone, named Pele's Vents, was located at a depth of 960 at the southern edge of the summit. The floor of the summit of Loihi was largely covered by prismatic talus, with interstitial hydrothermal clays. Pillow and tube lavas with volcanic cones 5 to 50 meters high were exposed along the axes of the southern and northern rift zones. The inner margin of the summit displayed fissures and normal faults with the downthrown component towards the center of the summit. The pre-earthquake structural data suggest a pre-caldera structural stage for Loihi. Maximum sustained hydrothermal activity observed on Loihi over the past 10 years existed at Pele's Vents with other sporadic venting occurs along the summit platform and along the south rift. Following the earthquake swarm, the hydrothermally saturated Pele's Vents cone gave way and slid into the inner pit crater. Subsequently, the observed above- bottom hydrothermal plume source deepened from 960 to 1,160 meters, possibly emanating from the same intrusive heat source as Pele's Vents. The observed inward collapse of the summit structures and subsequent opening of fissures gave rise to diffuse venting from the newly formed caldera-like depression with the bottom-hugging hydrothermal pool located at depth between 1,250 and 1,220 meters at the sites of the pit craters.

Jan 1, 1996

By Rahul Sharma

Although, mining of minerals such as polymetallic nodules and sulphides from the deep sea floor has been delayed due to the combination of factors such as current availability of Cu, Ni, Co, Mn (and other metals) on land and their fluctuating prices; these deposits are still considered as the alternative source for metals in the 21st century. Exclusive rights for exploration in the ?Area? (beyond the national jurisdictions of any country) given to eight countries and consortia by the International Seabed Authority and the estimated resource of 300 million tonnes in a typical area of 75,000 km2 is expected to yield about $17.5 billion (at December 2008 metal prices) in 20 years life span of a single nodule mine-site. In order to recover 3 million tonnes of nodules, an area of 300 sq km only will be mined annually (i.e. <1 km2/day) for an optimum abundance of 10 kg/m2. However, during mining, large quantity (22 tonnes/day) of sediments associated with nodules would be resuspended that could lead to certain environmental impacts on the benthic ecosystem. Several small-scale benthic impact experiments in the Pacific and Indian Oceans, have given some insight into the possible environmental impacts and the restoration processes, but the possibility of extrapolating these findings to a commercial mining scale remains an issue to be considered. An estimated capital expenditure of $1.05 billion and operating expenditure of $4.2 billion for a single deep-sea mining venture will have to be weighed against the availability of mineral ores on land as well as the metal prices in the world market. None-the-less, development of technologies for mining and metallurgical processing, as well as formulation of regulations and guidelines for potential ?contractors? to mine these minerals have been progressing consistently. These coupled with recent efforts by certain ?entrepreneurs? to initiate mining of seafloor massive sulphides in the EEZ of certain countries, indicate the continuing interest and support the perception that such deposits could well be the future sources of metals. This paper analyzes the current status and discusses the economic, environmental, and technical issues that need to be addressed for sustainable development of deep-sea minerals.

Jan 1, 2010

By Sukumar Bandopadhyay

The Marine Minerals Technology Center (MMTC) was authorized by an act of the United States Congress in 1996. The act established several marine minerals research centers in the U.S., including one at the University of Alaska Fairbanks. The Alaska MMTC is funded through the Minerals Management Service of the Department of the Interior and concentrates its research in the Arctic seas region. Recent research projects at the MMTC include, among others, application of a geographic information system (GIS) to the gold placer deposits offshore Nome, Alaska, development of a marine gold placer reserve definition model using a neural network, and development of an expert system model for submarine tailings disposal (STD) planning and decision-making. Although geostatistics remains the most prevalent method used today for ore grade estimation, researchers have made numerous improvements over the years for accurately predicting grades of ore using other estimation techniques. One such technique, the neural network, has recently emerged as an alternative to geostatistics for grade estimation purposes. A neural network is a non-linear, model-free estimator that is well-suited for noisy and/or sparse data environments. Neural networks perform best with non-linear spatial data, contrary to the stationary assumption of ordinary Kriging techniques. In the marine placer ore reserve definition model, the neural network technique was used to estimate placer gold reserves offshore Nome. This study demonstrated the utility of neural network modeling over other traditional ore reserve estimation methods, especially for high cut-off grades. Some of the relevant issues of neural network modeling were also addressed in the study. In testing, the neural network produced results that were close to those from geostatistical techniques including Kriging, polygonal, and inverse distance methods.

Jan 1, 2005

By Audrey Boissier, Marie-Anne Camon, Cecile Cathalot, Yves Fouquet, Laurent Bignon, Arnaud Agranier, Ewan Pelleter, Sylvain Bermell, Florian Besson

INTRODUCTION In October 2014, on behalf of the French government, Ifremer, along with the International Seabed Authority (ISA), signed a contract to start a detailed exploration program for seafloor massive sulfide (SMS) deposits in the work plan located on the slow spreading Mid-Atlantic ridge (MAR). The contract has a fifteen-year lifetime and the related exploration program must include the outline of SMS deposits and a resource assessment, as well as detailed environmental base line studies in the contract area. The exploration for SMS deposits generally includes detection of hydrothermal plume anomalies, acquisition of surface and near-bottom geophysical data, sampling operations from the research vessel (e.g. dredges, cores), and dive operations. The environmental studies include, among others, short and long-term oceanographic measurements, water column studies, biodiversity evaluation close and far from SMS deposits, characterization of natural hydrothermal plumes and related sedimentation. The HERMINE research cruise held from March 13th to April 28th 2018 (R/V Pourquoi Pas?) was the first cruise dedicated to exploration of active and inactive SMS and to the quantification of natural chemical input to the water column. The HERMINE cruise strategy was built up around three main objectives: (i) regional exploration including the detection of plume anomalies and the research of SMS deposits, (ii) local exploration of a SMS district and (iii) integrated study of a natural hydrothermal plume. This 3-in-1 cruise required us to optimize the switch between dives and surface operations. Day-time was devoted to dive operations whereas night-time was mostly dedicated to CTD/Rosette operations. The Nautile HOV (Human Occupied Vehicle) was well suited to the working time schedule of the cruise because it was time efficient in shorter (i.e. < 10h) dives due to fast descent and ascent speed, fast submerged forward speed, high maneuverability and the ability to carry heavy science payload as well as large volume of samples. Regional Exploration The first seventeen days of the HERMINE cruise were devoted to regional exploration, i.e. the detection of new plume anomalies and the research of new sulfide mineralization in the French work plan (10 000 km2; 6 clusters).

Jan 1, 2018

By Ian B. Clark

In October-November 1993, the Centre for Cold Ocean Resources Engineering, Memorial University of Newfoundland and University of Victoria jointly carried out reconnaissance surveys at Pine Cove, Baie Verte, Newfoundland. Pine Cove is the site of a multi-year study examining the environmental impact of a shallow water small-scale marine placer gold mining operation. The reconnaissance survey data collected will be used to develop a multi-year environmental effects monitoring (EEM) program for Pine Cove, Baie Verte, but more generally an EEM protocol for shallow water small-scale marine placer mining, which meets the requirements of Canadian government regula¬tors such as Environment Canada and the Department of Fisheries and Oceans. The Pine Cove mining operation is currently scheduled for the summer of 1995, and will use two mining methods: a hydraulic suction dredge in shallow water (<10 meters) operated by a scuba diver, and a hydraulically actuated clamshell dredge in deeper water (-30 m). A centrifugal concentrator will be used to extract the heavy minerals from the mined marine sediments, and the tailings will be returned to the sea floor via a suspended discharge pipe. The reconnaissance work at Pine Cove included geophysical, geochemical, oceanographic and biologi¬cal surveys, providing data which will enable prediction of the potential environmental impacts of the proposed mining operation. The geophysical surveys showed the sea floor to be covered by varying

Jan 1, 1994

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

By Sukumar Bandopadhyay

The Marine Mining Technology Center (MMTC) was authorized by an act of the United States Congress in 1996. The act established several marine minerals research centers in the U.S., including one at the University of Alaska Fairbanks. The Alaska MMTC is funded through the Minerals Management Service of the Department of the Interior and concentrates its research in the Artic seas region. Recent research projects at the MMTC include, among others, a geographic information system (GIS) application to the gold placer deposits offshore Nome, Alaska, a marine gold placer reserve definition model using a neural network, and development of an expert system model for submarine tailings disposal (STD) planning and decision-making. Although geostatistics remains the most prevalent method used today for ore grade estimation, researchers have made numerous improvements over the years for accurately predicting grades of ore using various other estimation techniques. As a result, the neural network has recently emerged as an alternative to geostatistics for grade estimation purposes. A neural network is a non-linear, model-free estimator that is well-suited for noisy and/or sparse data environments. Neural networks perform best with non-linear spatial data, contrary to the stationary assumption of ordinary Kriging techniques. In the marine placer ore reserve definition model, the neural network technique was used to estimate placer gold reserves offshore Nome. This study demonstrated the utility of neural network modeling over other traditional ore reserve estimation methods, especially for high cut-off grades. Some of the relevant issues of neural network modeling were also addressed in the study. In testing, the neural network produced results that were close to those from geostatistical techniques including Kriging, polygon, and inverse distance methods.

Jan 1, 2004

By P. A. Rona

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

Jan 1, 1989