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By Raymond A. Binns

Drilling into an active hydrothermal system linked to convergent-margin felsic magmatism is a listed priority of the Ocean Drilling Program that addresses several fundamental geoscience issues. Solid and fluid products of felsic rock-water interaction, and the consequences for global chemical fluxes and for ore deposition, should differ from those in basaltic mid-ocean ridge environments already successfully tested by Legs 106, 139, 158 and 169. So, too, will fracturing controls on fluid pathways, and sources for metals and ligands. Researching the subsurface volcanic, structural/hydrologic, and mineralisation/alteration architecture of a drilled felsic-hosted system also has economic implications, especially for land¬based mineral exploration. A first-order hypothesis to be tested states that fluids derived from volatile-rich magmas are more important than recirculated seawater in convergent-margin hydrothermal systems - economic geologists increasingly appeal to this for creating "world-class" massive sulfide orebodies. Another hypothesis proposes "subhalative" massive sulfide deposition within hydraulically expanded volcanic products as a factor in generating large orebodies. Many second-order hypotheses such as leaching fractionated volcanics to cause gold enrichment in back¬arc systems also need testing. The thoroughly surveyed, active, PACMANUS hydrothermal field in the Eastern Manus back-arc basin of Papua New Guinea will be the site for ODP Leg 193 commencing in November 2000. It lies near the crest (1655-1750 m) of high-standing Pual Ridge, a 40 km-long edifice of dacite/rhyodacite with basal andesite all having geochemical and isotopic affinities with modern arc volcanoes of nearby New Britain. PACMANUS includes at least three focussed, high-temperature "smoker" sites with Cu+Au-rich massive sulfide deposits, and a field of diffuse, lower temperature venting through intensely altered dacite where modelling indicates significant subsurface mineralisation. Isotopic characteristics of deposits and vent fluids suggest magmatic contributions to the mineralising fluids.

Jan 1, 2000

By Arturo Carranza Edwards

Sedimento II oceanographic cruise, on board of the B/O El Puma, shows a new high anomaly or phosphate associated with shelf sediments from the south Mexican Pacific. Recently, were found two anomalies in the Gulf of Tehuantepec, that are located to the east of this new anomaly, that is related to muddy sands and rock fragment debris. The latter shows values of 17% P205. The phosphate occurrence is probably associated with red tides locations that usually are found in sites where sediments are phosphates enriched. These findings suggest that south Mexican Pacific is of potential interest for P205, in waters with high nutrients values. The possibility of a more regional occurrence of phosphate, from California to Chile is suggested.

Jan 1, 2000

By Carl L. Kaiser

This abstract discusses selected recent technology developments at the Deep Submergence Lab at the Woods Hole Oceanographic Institution aimed at fundamentally changing the nature and scope of AUV operations in the deep ocean. The Autonomous Underwater Vehicle (AUV) Sentry is described in its current configuration with discussion of emerging capabilities. Telepresence enhanced AUV operations are discussed including moving both operations and data processing personnel off the vessel. Autonomous Surface Vessel (ASV) aided AUV operations are discussed including recent experiments where an ASV provided both navigational aiding and a satellite based relay for acoustic communication of telemetery and mission redirection. New flexible communications strategies to perform intervention and manipulation tasks from an untethered vehicle are discussed. The abstract concludes with a brief discussion of industrial collaborations, including the newly launched Center for Marine Robotics.

Sep 14, 2011

By Grigori Abramov

As we enter into the 21st Century, miners are looking more attentively at new mining technologies allowing decrease environment damage along with operational cost. This technic would allow developing of poor and difficult mineral deposits, including the World Ocean offshore zone. Borehole Mining is an underground/underwater remote method of mining carried out from floating platforms or vessels. Definition of Borehole Mining (BHM), working schematic, main technical data and its advantages are given. The method is currently in use in mining of different type of raw materials, such as: uranium, iron ore, quartz sand, coal, polymetallic ores, phosphate, gold, diamonds, rare earths, amber and more. It is also in use in oil and gas stimulation, salt domes storages building and environmental problems solution. Recently recorded data of Borehole Mining productivity (80-100 t/hour/hole) and a depth of mining (over 1 km) has been achieved in a last couple years. Remoteness of method not only secures complete safety of operations but also allows wide sector of underwater applications. The World leaders in Borehole Mining are Russia and the United States. Based on previous experience the Universal Tool for Seabed Borehole Mining has been developed for wide sector of usage: from exploration and mining - through oil & gas stimulation to souterrain storages construction and lake's bottom cleaning.

Jan 1, 2000

By Charles L. Morgan

In June 1996, the United Nations International Seabed Authority opened shop in Kingston, Jamaica as an autonomous international organization charged with the administration of seabed mineral developments in all areas beyond national jurisdictions. The Authority is a consequence of the 16 November, 1994 entry into force of the 1982 United Nations Convention on the Law of the Sea (UNCLOS) and the 1994 Agreement relating to the Implementation of Part XI of UNCLOS. The total seabed area included within the Authority?s purview has yet to be assessed accurately, but clearly constitutes the largest single jurisdiction on the planet. The Authority is governed by legislative bodies called the Assembly and the Council and an administration called the Secretariat. The Assembly includes representatives of the 132 member states which are currently parties both to UNCLOS and to the 1994 Agreement. These member states directly fund the operations of the Secretariat. They include most of the world?s developed nations, island nations, and others among the 188 independent countries which are members of the United Nations. Notably absent are the United States and Canada, which are the only developed coastal states not represented. The Council is a 36-member subset of the Assembly representatives selected through a somewhat involved process designed to achieve a balanced representation of the specific interests of the members. Ultimate responsibility for the Authority?s actions resides in the Assembly, but most initiatives originate in the Council. Also included in the Authority are two subsidiary advisory bodies, the Finance Committee, which reviews the Secretariat?s budget, and the Legal and Technical Commission, which evaluates claims and drafts technical regulations. The Secretariat itself includes a staff of about 30, including 15 highly qualified and competent attorneys, accountants, engineers, and scientists. Details describing the composition and activities of these bodies can be found at the Authority?s website (http://www.isa.org.jm).

Jan 1, 2000

By David S. Cronan

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

Jan 1, 2003

By Steinar L. Ellefmo, Maxime Lesage

"There are many reasons invoked when discussing the relevance of deep-sea mining minerals. The shift towards more focus on renewable energy (“the green shift”) will not be possible without more materials coming from the mining industry. The increasing population, and thus increased number of consumers, will lead to an increase of the mineral demand. It has been established that recycling will not satisfy the need for more minerals by itself. Meanwhile, land mineral resources - such as copper – become every day more complex to extract. The question of the deep-sea minerals exploitation’s viability needs to be studied now. Within the framework of feasibility studies, various topics such as environment, technologies and operations management must be addressed. Recognising deep-sea mining as a hybrid activity - taking from the mining, maritime and the offshore oil and gas industries - it is deemed too complex for a global assessment. Each deep-sea mining environment is worth its separate study.Norway is recognised as a seafarer nation. Looking towards the sea and driven by the will to thrive on the Blue Economy, Norway decided to investigate the case for deep-sea minerals on its Extended Continental Shelf. The MarMine project is a materialisation of this endeavour. The Norwegian case will address its own particularities such as a respectable water depth, the arctic environment, the remoteness to shore support and an environmental aware population as well as subsequent policies."

Jan 1, 2017

By Philomene Verlaan

This study examines the possible relationships between compositional variability in non-hydrothermal manganese nodules and large-scale environmental parameters. In the central SW Pacific (145-180° W and 20-O° S) the level of primary productivity, the rates and proportions of carbonate, silica and organic matter supply to the sediments, and the position of the seafloor relative to the Calcium Carbonate Compensation Depth (CCD) appear to directly influence nodule composition. Four zones of nodule composition are apparent. These zones correlate fairly well with the level of primary productivity in surface waters, as estimated by satellite-based measurement of chlorophyll content. The observed correlations between surface productivity and nodule composition are consistent with the contention that the dominant source of several transition metals in these deposits (i.e , Mn, Ni, Cu. and Zn) is provided by removal of fine-grained particulate matter from the water column by biological means. Subsequent decay of organic matter in sediments augments the content of these metals in the nodules through oxic and sub-oxic diagenesis. The opposite behavior of Fe and Co content may in part result from mineralogical and dilution effects.

Jan 1, 2000

By Fernando J. A. S. Barriga

"Recent concerns over the availability of many mineral raw materials, and newly available technological developments, produced renewed interest in deep-sea mining. However, environmental concerns, with variable degrees of justification, are raising opposition to the concept. The forecast for the behavior of consumption versus availability of many raw materials, nearly all critical metals, arguably show that consumption will grow much faster than resource discovery onshore. Finding new sources of raw materials seems inescapable. The deep seafloor stands out as the only likely candidate.Sea Floor Mining and the EcosystemMarine mining has already started, decades ago, for diamonds, currently up to depths near 400m. Although the industry recognizes there is a footprint, it considers the footprint quite minor, because the area mined is small: in Namibia, where offshore diamond mining is now 70% of the country’s total, only 3% of the concession of 3,700 sq miles (9600km2) have been mined. As plans to mine deep-sea massive sulphide deposits and polymetallic nodules progress, the environmental concerns grow. Some of these concerns are as follows:?The deep-sea ecosystems are composed of long-lived species, with low rates of reproduction. The environment may not recover from mining on a human time scale;"

Jan 1, 2017

By Richard C. Newell

The United Kingdom marine aggregate mining industry is the second largest of its kind after Japan. Materials for the construction industry, sea defences and for many other purposes are exploited from shelf waters at depths of 30-50 metres by self-contained suction dredgers which often screen material to obtain a cargo of a particular quality. Assessment of the environmental impact of such mining activities both within the boundaries of the dredged areas, and in the zone of deposition of outwash from the dredger has in the past been mainly based on predictive models based on the settlement rates of the individual particles and assumed Gaussian diffusion principles during the settlement phase. Recent studies which we have made on both the mass balance for materials rejected during the dredging process and direct measurements of the settlement of material in the dispersing plume suggest that the zone of settlement is much less than that predicted from diffusion models. Instead of a downstream settlement plume of 10-20 km in the tidal currents of U.K waters, our measurements show that inorganic components of the dredger plume reach background levels in the water column within 880 metres.

Jan 1, 2000

By Jonguk Kim

Texture and geochemical composition of hydrogenous ferromanganese crust from relatively adjacent three seamounts (OSM2 at 157°35'E, 13°55'N, Lomilik at 161°37'E, 11°42'N and Lemkein at 165°05'E, 9°18'N) near the Marshall Islands in the western Pacific (Figure 1) were investigated in order to elucidate their growth history. These seamounts, located in different latitudes, are along a line that is parallel with the direction of Pacific plate movement. Thick crusts commonly have three or four distinct layers (Figure 2): (1) layer 1, uppermost layer, is black, dense, and has a botryoidal, columnar, or laminated texture; (2) layer 2, overlain by layer 1, is Fe-stained, porous to vuggy and filled with sediment; (3) layer 3, phosphatized layer, is black, massive, dense, and impregnated by CFA, (4) layer 4 shows parallel to undulatory laminated texture and cut by CFA-filled veins. Layer 1 and 2, unphosphatized young layer, are observed in crust samples collected from all seamounts. However, lower part of the crust shows different textures in different seamounts. Both layer 3 and 4 are found in thick crust from OSM2 but layer 4 is absent in crust samples from Lemkein and Lomilik. All the uppermost layers (layer 1) from three seamounts have similar textural and geochemical characteristics. Layer 2 is overlain by layer 1, is porous, partly Fe-stained, and sediment-infilled. In previous studies, layers 1 and 2 have grown in different oceanic environment. Textural and geochemical properties show that layer 1 has grown under relatively higher bottom water activity and lower productive environment than layer 2. Carbonate and detrital materials in layer 1 are not abundant compared to layer 2. Layer 2 can be assumed to have grown under equatorial high productivity zone (EHPZ) while layer 1 has started to grow when the seamount left from the EHPZ.

Jan 1, 2003

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 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 Jai-Woon Moon

Lemkein seamount located in the west of the Kuwajleen Atoll of RMI is a relatively samll, simple-shaped, peaked type seamount with its base at 4,500 m and summit at 1,452 m water depths. Ferromanganese crusts were identified in the water depth range between 2,000 m and 2,500 m, and they were mostly observed on the northern slopes of the seamount. Among various substrate rocks, breccia occurred most commonly with crusts and formed the thickest crust layers. Average thickness of the Lemkein crusts was about 5 cm. Their chemical compositions were similar to other crusts found in the RMI area; Mn=25.82%, Fe=15.29%, Co=0.74%, Ni=0.56%. Lemkein crusts were characterized by their four distinctive internal layers; 1) Massive Layer 1; 2)Porous, Fe-stained or sediment infilled Layer 2; 3) Massive to slightly porous Layer 3; and, 4)Massive, Dense, Phosphotized, CFA veined Layer 4. Layers 1 and 2 were generally similar in composition, but highest Co concentrations were measured in Layer 1 while relatively higher concentrations of Al, Rb, Fe, and Ti were observed in Layer 2. Layer 3 showed higher concentrations of Ca and P than Layers 1 and 2. Based on the Co-chronography, the age of Layer 1 is 0¡?6 Ma (growth rate = 1.50 mm/Ma), Layer 2 is 6¡?15 Ma (1.75 mm/Ma), Layer 3 is 15¡?27Ma (1.76 mm/Ma), and Layer 4 is 27¡?45 Ma (2.06 mm/Ma). These preliminary results indicated that high Co contents in Layer 1 resulted from slow growth rates; Layer 2 was formed under relatively strong influence of high terrestrial input; and, Layer 3 was probably affected by a minor phosphatization event occurring in 15 Ma.

Jan 1, 2000

By R. C. Newell

The primary objective of this study was to establish the fate and distribution of material rejected during marine aggregate dredging, and the extent to which this is associated with spatial changes in biological community composition. Two actively dredged sites in the southern North Sea (Licence Areas 430 and 106) were selected in order to provide a comparison of impacts between sites subjected to different levels of dredging intensity and of contrasting environmental conditions. Dispersal of material rejected during the dredging process was monitored by means of acoustic doppler current profiling techniques (ADCP). Composition of the substratum and benthic invertebrate assemblages were investigated by the analysis of seabed grab samples. It was found that dredging in both areas had an impact on seabed bathymetry in the form of dredge furrows and also led to a reduction of the coarse gravel-sized components of the worked area. Sand sized particles were shown to increase in the surface deposits of both dredged areas. This is likely to reflect both the removal of coarse particles as cargo and the settlement of finer particles rejected during overboard screening. Dispersion and settlement profiles of material rejected by dredging vessels suggested that the majority of the suspended sediment load resulting from overboard screening settles to the seabed within 500 m. Some evidence of suspended sediment loads above background levels were noted at distances of up to 2 km from the working vessel. Analysis of the particle size composition of the deposits, along the axis of transport of material from the dredged sites, suggested that the impact on the sediment composition outside the boundaries of the dredged sites is dependent on the strength and direction of net sediment flux at the seabed. Benthic invertebrate communities within the dredged zones of both areas were found to differ significantly from communities in nearby undredged deposits. A major suppression of species richness and abundance was noted in the dredged sectors of both sites when compared to control locations. A ?footprint? of potential impact on the benthic fauna was noted in samples taken along the axis of sediment transport at distances of up to 1750m outside the boundaries of Area 430. In contrast, impacts on benthic community structure at Area 106 appeared to be confined to the immediate vicinity of the dredged zone itself. This apparent difference in impacts, beyond the boundaries of the dredged sectors between the two study sites, was thought to be a reflection of the smaller quantities of material rejected at Area 106 and the weak seabed sediment flux which is characteristic of this area. These findings, along with those of numerous dredging impacts studies, were then used to make generalised predictions of macrobenthic community recovery following marine aggregate extraction in a variety of seabed habitats.

Jan 1, 2004

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 Andrew E. Grosz

The Atlantic Continental Shelf (ACS) of the United States includes about 391,000 km2 extending from the shoreline to the 200-m isobath. It varies in width from a fraction of a kilometer (offshore of southern Florida) to about 150 km (offshore of Cape Cod, MA). The contained volume, of sand and gravel is estimated to be on the order of 3-7 x 1.011 m3. Concentrations of potentially commercially important heavy minerals (HM) exist locally, particularly in high-energy depositional environments (for example in channels, tidal deltas, ridge and swale areas, and submerged former shoreline complexes). Recently completed and ongoing studies of HM assemblages in vibracore samples from the south shore of Long Island Sound, NY, offshore of Ocean City, NJ, offshore of Cape May, NJ, offshore of the mouth of Chesapeake Bay, VA, offshore of Myrtle Beach, SC (grab samples), and the ACS offshore of Florida provide the information base for this presentation (Table 1). The surficial sediments of the ACS contain local concentrations of HM that compare favorably to those in currently mined onshore deposits as shown

Jan 1, 1988

By Thomas Kuhn

Germany?s industry heavily depends on the continuous import of mineral commodities such as manganese, copper, nickel, and molybdenum. Due to the strong increase in metal prices since 2002 Germany?s federal geological survey, the Bundesanstalt für Geowissenschaften und Rohstoffe (Federal Institute for Geosciences and Natural Resources, hereafter called BGR) applied for a license area for the exploration of deep-sea manganese nodules in the Pacific manganese nodule belt between the Clarion and Clipperton fracture zones. A 75,000 km2 covering license area was eventually granted to the BGR by the International Seabed Authority (ISA) in 2006. It is separated into two parts: ?W1? (17,000 km2) and ?E1? (58,000 km2; Fig. 1). The BGR obtained initial information on the abundance and grade of nodules in the license area from samples collected during three cruises with R/V Valdivia and one cruise with R/V Sonne between 1976 and 1978 (Rühlemann et al., 2009). Since the accuracy of navigational data obtained during these cruises is outdated and sample coverage is unevenly distributed and sparse in many parts of the license area, BGR has started a new exploration program to investigate the German license area according to the rules, regulations and procedures issued by the ISA for the exploration of Mn nodules in the Area.

Jan 1, 2010

By Tetsuo Yamazaki

Manganese nodules on deep ocean floors have continuously received attention as potential sources for strategic metals such as Co, Ni, Cu, and Mn, due to their vast distribution and relatively higher metal concentrations (Mero, 1965; Cronan, 1980). Several registered Pioneer Investors have already identified promising sites in deep-sea regions for manganese nodule mining (ISA, 1998), and appropriate mining technologies have been developed during the last thirty years by the international consortium and several nations (Welling, 1981; Kaufman et al., 1985; Bath, 1989; Charles et al., 1990; Yang and Wang, 1997; Yamada and Yamazaki, 1998; Hong and Kim, 1999; Muthunayagam and Das, 1999). The mining feasibility for manganese nodules, including an economic evaluation, has been examined in detail by some researchers (Andrews et al., 1983; Hillman and Gosling, 1985; Charles et al., 1990; Soreide et al., 2001).

Jan 1, 2011

By Richard H. T. Garnett

Marine mining on the continental shelf was first attempted in 1900 for gold off the beaches of Nome, Alaska. Attempts continued until 1990 with cutter-suction, airlift and bucket-ladder dredges. Offshore Thailand profitable production of tin resulted from clamshell, bucket-ladder and trailing suction hopper dredges. Today in Indonesia numerous bucket-ladder dredges continue to mine tin. Off the coast of Namibia and South Africa nearly a dozen large and medium sized vessels are engaged in diamond production. The obvious risk results from the working environment. Vessels and lives have been lost in the past. At best the availability of mining equipment is reduced. Leaving aside the marketing and financing aspects, otherwise the most important risks are technical. They manifest themselves as diamond production short-falls with obvious financial consequences. Bias and deficiencies in sampling equipment and procedures may result in misleading grade estimates, even serious under-estimation. Inadequate sampling in terms of sample support and density may result in over-optimistic grade determinations, especially if under-sized mining blocks are outlined. Quantitative measurement of the geotechnical characteristics of the sediments to be mined is an essential stage in a feasibility study. Without a full understanding of the bedrock profile and the overlying sediments the ease, completeness and speed of excavation during the mining process cannot be properly estimated. Both historically and at present the greatest negative discrepancies from production estimates result, not from grade shortfalls, but from significantly lower mining rates than thought possible by the operators. The learning curve in marine, production mining is steeper and longer than is generally recognised by newcomers to the industry. Examples are provided from tin, gold and diamond mining experiences.

Jan 1, 1998