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By Carl H. Hobbs

The needs of the on-going basic maintenance operations and proposed enhancement and hurricane protection projects in the City of Virginia Beach exceed the capability land-slide sources of sand. Through the past several years our studies have concentrated on locating and defining suitable quantities of sand appropriate for use on the area's beaches and assessing some of the consequences of dredging in shallow offshore areas. By providing information concerning the geological setting of sand resources, the local wave climate, and benthic infauna, the overall research project has strengthened the knowledge and understanding of several facets of Virginia's inner continental shelf. We have identified three distinct settings for deposits of beach-quality sand, two of which (filled channels and surficial shoals) are distinguishable in relatively unprocessed sub-bottom profiles and cores. The third, a sand facies within a larger stratum, is discernable only with a suite of cores. Sandbridge Shoal, about 5 km offshore of the resort and residential community of Sandbridge appears to contain a substantial quantity of sand that could be exploited with comparatively few problems. It already is designated as the source of material for use in a shoreline protection protect for a federal facility. Fluvial(?) fill of a late Pleistocene channel lust offshore of the main, commercial, resort area may offer a proximal alternative to existing and proposed resources. Ongoing work to describe the local wave climate and the possible impacts of anthropogenic alterations of the bottom topography on wave transformation and studies of the biological community as it might be affected by dredging will help fill-out our series of studies. Prior to utilization of the resource additional work is needed to provide better definition of the limits and magnitude of the sand bodies. Finally decisions concerning the use of specific resources will have to include physical, biological, economic, technical, and social considerations.

Jan 1, 1996

By D. S. Cronan

Studies on polymetallic manganese nodules and Co-rich crusts in the EEZ's of the Cook, Line, Ellice and Phoenix Islands between 0-20°S show that Ni and Cu reach their greatest combined abundances of over 2% between 2-8°S on the southern margin of the equatorial zone of high biological productivity, as a result of biological fluxing of Ni and Cu to the nodules at and just below the CCD. By contrast, Co reaches it greatest abundance of 0.6% south of 8°S in nodules on non-biogenic clays well below the CCD where little biological Co supply is likely. Nodule abundances are greatest (up to 30kg/m2) in the Co-rich area in part due to AABW flow, giving highest overall metal quantities per sq meter in the nodules there, particularly of Co. There are approximately 110 x 106 tonnnes of combined Ni plus Cu plus Co expressed as Ni equivalent in Cook Islands EEZ nodules, approximately 12 x 106t. in Phoenix Islands ones, and approximately 1.4 x 106 t. in Ellice Islands ones, in areas of greater than 5kg/m2 nodule abundance. In the Co-rich crusts, Co averages about 0.7% and crust thickness about 1.6cm, both related to metal fluxes in and adjacent to the 02 minimum zone in association with which both maximum thicknesses and Co grades occur. Within the Cook Islands permissive area there are about 930 x 103 t. of Co and 630 x 103 t. of Ni in crusts, in Phoenix Islands crusts there are about 69 x 103 t. of Co and 55 x 103 t. of Ni, and in Ellice Islands crusts there are about

Jan 1, 1989

By Kokichi Iizasa

Two major Kuroko-type deposits and minor sulfide deposits have been found in the middle Izu-Ogasawara (Bonin) Arc, Japan (Fig. 1). The Hakurei deposit, one of the major Kuroko-type deposits, was recently found in Bayonnaise knoll caldera in the nascent rift zone, which lies 20 km westward of the Sunrise deposit in Myojin knoll caldera on the Izu-Ogasawara volcanic front. The Hakurei deposit is a huge hydrothermal field measuring 500 m by 700 m in plan view. The Bayonnaise knoll caldera is mainly composed of dacite lavas and fragmental material on the caldera wall and rim, and its floor contains sediment composed of pumice, volcanic fragments, and hydrothermal clay. It is associated with a post-caldera dome and has a slightly ellipsoidal caldera rim that measures 3 km by 2.5 km, with about 200 m relief. The water depths of the caldera floor range from about 840 m to 920 m. The Kuroko-type deposit in the Bayonnaise knoll caldera occurs on the southeastern caldera floor where the caldera boundary faults intersect with a N-S-trending normal fault of the rift zone. In the deposit, many sulfide chimneys are generally less than 10 m high, and sulfide mounds are distributed around the caldera floor and on the sloping talus at the foot of the caldera wall. The deposit is buried in part by talus composed of pumice and volcanic fragments. Sulfide chimneys are still active, and inactive ones and their fragments are partly oxidized to reddish material. Chimney sulfides are mainly composed of sphalerite associated with chalcopyrite, galena, pyrite, and barite, and chemically enriched in Au up to 14 ppm and Ag up to 1400 ppm with major Zn, moderate Ba, and minor Pb, Hg, Cu, and Fe.

Jan 1, 2005

By Jan M. Peter

The Early Norian Windy Craggy massive sulfide deposit is within the allochthonous Alexander terrane of the Insular tectonic belt in extreme northwestern British Columbia (Figure 1). Host rocks are the Middle Tats Volcanics, part of an informally-named volcano-sedimentary succession of mixed graphitic argillites and mafic pillowed and massive volcanic flows and sills of Upper Triassic age (Figure 2) that have suffered only lower greeschist-facies metamorphism. The volcanic rocks are light rare earth element (LREE)-enriched and display a variably developed back-arc subduction signature. Major and trace element compositions of the host argillite show that it contains an appreciable hydrothermal component, as evidenced by low high Fe and Mn contents. These sediments therefore record steady, continuous hydrothermal activity punctuated by intermittent turbidity currents sweeping into the basin. The deposit consists of at least two discrete sulfide lenses (the North and South Sulfide Bodies), as shown in Figure 3, a level plan at the elevation of the exploration workings. Published reserves at 0.5% copper cut-off are 297.4 million tonnes grading 1.38% Cu, 0.08% Co, 0.21 g/t Au and 3.9 g/t Ag (as of December 1991). However, the deposit is larger than this and further drilling is required to delineate it completely. Mineralization comprises massive sulfide, stringer/stockwork, and finely bedded to laminated sulfides and exhalites. Stockwork mineralization consists of sulfide-quartz-chlorite veins with attendant chlorite and silica alteration. Mineralization consists predominantly of massive pyrrhotite andlor pyrite with lesser chalcopyrite and magnetite. Figure 4 is an oblique section through the North Sulfide Body, the most northerly sulfide mass shown in Figure 3, which shows the distribution of the pyrite and pynhotite-rich massive mineralization and the stringer zone. The North Sulfide Body contains appreciable sphalerite, whereas the South Sulfide Body contains only trace amounts. Gangue minerals include quartz, chlorite, calcite, siderite, ankerite, stilpnomelane and magnetite. The minor hydrothermal exhalite sediments are comprised of chert, carbonate, and minor

Jan 1, 1993

By Alister C. Skinner

The Marine Operations and Engineering section of the British Geological Survey based in Edinburgh, Scotland have, over the last 30 years, developed and operate a series of remotely operated, and powered, seabed coring systems. These systems were initially developed to provide a cost-effective solution to ground truth seismic reflection data for regional geological mapping, where the only solution that existed was conventional and expensive drill-ships. Since the early 1990?s these tools have been used for many other applications in industry and science. Currently the systems can operate in up to 2000 m water depth for 5m seabed penetration and up to 4500m water depth for a specialised oriented core drill which collects a scribed core to 0.8m below seabed. Scientific applications focus on determining the geology of an area and follows pre-determined geophysical interpretations. It usually also follows other coring attempts with non-powered coring equipment which is invariably unsuccessful if the strata is over-consolidated sediments or hard rock. Commercial applications include cable and pipeline route surveys, diamond, gold and base metal exploration, beach reclamation and aggregate materials evaluation. In many cases there is a blend of science and commercial investigation typified by coring in hydrothermal vent areas or carrying out geological coring in a frontier oilfield province. The versatility of the drills allows cost effective and rapid operations in remote and hostile areas where a rapid investigation may be the only one possible in a short weather window. The deepwater operational capability also allows science and commercial assay to be obtained ahead of potential exploitation and allows formulation of scientific theories or commercial project plans based on sound core data. Being mobile and compact these corers may be used from suitable (Dynamically Positioned or Anchored) vessels of convenience and thus provide a cost effective platform for sampling different types of seabed geology on an international basis.

Jan 1, 2004

By Lorena Blanco, Guillermo Gómez-Ramos, Iker Blasco, Egidio Marino, Luis Somoza, Ricardo León, Teresa Medialdea, Javier González

"This study presents the first catalogue of marine mineral deposits and energy resources along the continental margin of Spain. Aggregates, oil and gas and metalliferous mineral areas have been defined and mapped. The catalogue, implemented in a geographic information system (GIS), is conceived as a first national database within the European network, which is being built as part of the EMODnet-Geology project. It comprises 8 types of mineral and energy resources for the Spanish margins: aggregates, hydrocarbons, evaporites, placer deposits, phosphorites, polymetallic sulfides, polymetallic nodules and cobalt-rich ferromanganese crusts (Figures 1 and 2). The catalogue stores a total of 409 marine mineral deposits and compiles information such as name, deposit type, main morphology, main minerals, setting or area extent for each mineral deposit. By number of deposits compiled, the aggregates are the most abundant (286) followed by hydrocarbons (62), cobalt-rich ferromanganese crusts (32), evaporites (9), placer deposits (8), phosphorites (5), polymetallic nodules (4) and polymetallic sulphide deposits (3). Considering the total extension, hydrocarbons (32,386 km2) and cobalt-rich ferromanganese crusts (24,951 km2) represent the biggest areas.The Geological Survey of Spain (IGME) is developing a new tool in the catalogue, according the International Seabed Authority (ISA) Database parameters, for individual samples on each ferromanganese deposit. The database includes an extensive collection of records that comprise five information groups: general cruise and sample data, physical properties, mineralogy, geochemistry and acronyms used. New attributes have been incorporated, in example: geophysical, sedimentological and petrological data in the deposit area, sample weight, porosity, morphology, textural and structural features, geochemistry of major, minor and trace elements (included REEs and PGEs) and supplementary cruise and laboratory reports. This new database complements the EMODnet-Geology project minerals catalogue, offering a deeper level of information for the areas with major potential for mineral or energy resources as they are the Canary Island Seamount Province, the West Margin of Galicia and the Gulf of Cadiz."

Jan 1, 2017

By Mark D. Hannington

Results of the R/V Sonne Cruise (Edison) to the Tabar-Feni Arc from March 11 to April 5, 1994, a joint German-Canadian research cruise aboard the vessel R/V Sonne, undertook detailed mapping of the Tabar-Feni island chain, Papua New Guinea. The Tabar-Feni chain is host to several large porphyry stocks and epithermal gold deposits, including the giant Ladolam gold deposit on the island of Lihir (minimum 19 million oz. Au). The principal objective of the cruise was to map the seafloor in the vicinity of recently active alkaline volcanic islands in the Tabar-Feni chain and to characterize the tectonic setting of large high-level porphyry and epithermal gold deposits in the region. Additional work was carried out on shallow-water hot springs associated with mineralized geothermal systems on the volcanic islands. Complete sets of 1:50,000 scale (20-m contour) maps of the seafloor were produced for each of the four island groups (Feni, Tanga, Lihir, Tabar). The Lihir group was the most active and the most interesting. At least 4 (and probably 6 or 7), previously unknown volcanic cones were discovered within about 10 miles south of Lihir. The volcanoes are clearly very young and appear to have erupted along extensional faults produced by regional plate rotation. This recent volcanic activity appears to reflect recent forearc extension and represents the southward propagation of volcanic activity towards New Ireland. One volcanic cone at 1,490 m water depth is hydrothermally active, with very large areas of diffuse venting (100-200 m across), densely populated by beds of giant clams (probably calyptogena). Other vent-specific fauna are also present, including crabs, snails, sulfide worms, scale worms, limpettes, etc. The clam beds sit on a crust of hydrothermally baked and indurated, sulfidic, hyaloclastite-rich muds. The mineralization consists mainly of fine-grained disseminated pyrite and amorphous Fe-sulfides. A second, much larger cone at a depth of 1,070 m is capped by massive vesicular lavas which are intensely fractured and mineralized. Abundant sulfides and amorphous silica occur in stockwork-like veins which

Jan 1, 1994

By Tobias Hens, Andrew Frierdich, Barbara Etschmann, Joël Brugger, Barrie Bolton

"Ferromanganese (Fe-Mn) nodules and crusts are prime targets for future deep-sea mining ventures due to their unusual enrichment of critical metals, such as Ni, Co, Cu, Ti, Te, Zr, Hf, Nb, Y, and REE. These metals are used in an ever increasing variety of high- and green-tech applications such as alloys, batteries for hybrid cars, fiber-optic cables, or liquid-crystal displays.1 Recovery and processing of these deposits will most likely be cost-intensive and require new solutions.2 Thus, innovative approaches towards the development of sustainable metallurgical processes represent one component that can positively affect the marine mining value chain. Dynamic mineral recrystallization of Fe- Mn oxide phases is a geochemical process that may have notable potential for future hydrometallurgical applications.Our research focuses on Mn oxides – potent trace metal scavengers with high sorptive capacity3 – and biogeochemical mechanisms that control Fe-Mn nodule and crust formation, alteration, and trace element enrichment. Biogeochemical redox cycling of Mn is characterized by microbial oxidation of aqueous Mn(II) to Mn(III,IV) oxides and (a)biotic reduction of these oxides to Mn(II)aq. During this cycling dissolved Mn(II) is in direct contact with solid-phase Mn(III,IV) oxides and can back-react via abiotic pathways (e.g., 4 and references therein). This results in continuous dynamic recrystallization of the Mn mineral substrate through coupled dissolution (trace metal release) – reprecipitation (trace metal incorporation) processes.4 We recently demonstrated in new experiments, that Ni is cycled during manganite recrystallization. It has been shown that, although Ni readily undergoes mineral-fluid repartitioning in the absence of Mn(II)aq, dissolved Mn(II) significantly catalyzes Ni exchange between solid phase and solution. Over a period of 50 days about 30 percent of the Ni atoms in Ni-substituted manganite (natural abundance composition) were exchanged with a 62Ni(II)aq isotope tracer at pH 7.5. Based on these outcomes we employed similar techniques to investigate the impact of dynamic recrystallization on Mn oxide phases in deep-sea ferromanganese nodules and crusts from three circum-Australian locations (South Tasman Rise, Lord Howe Rise, Coral Sea) and the Central Pacific Basin."

Jan 1, 2017

By Sung-Hyun Park

Core sediment samples collected from the KODOS area of the Clarion-Clipperton Fracture Zone in the NE Equatorial Pacific were analyzed for chemical and mineralogical compositions to investigate the depth- and time-related variation of paleoenvironmental and paleoceanographic conditions during their deposition. These core sediments are divided into three layers from top to bottom by its color; 1) brown layer (Unit I), 2) pale brown layer (Unit II), and 3) black brown layer (Unit III). Geochronology of 10Be indicated the depositional age of Quaternary for Units I and II and of late Pliocene for Unit III with a potential short hiatus between them. Analyses of interelemental correlation identified three major groups of elemental groups that show moderate-to-strong correlations: 1) Al, Ti, K, and Fe representing for terrestrial alumino-silicate fraction of sediments, 2) Ca, P, REEs, Cu, and Zn for biogenic apatite, and 3) Mn, Ni, and Co for hydrogenous Mn-oxide. With an exception, Fe content was very high and showed fair correlations with Mn, Ni, and Co in Unit III. Unit III shows high smectite but low quartz and illite contents compared to the overlying two units, indicative of reduced supply of terrestrial materials. In a meanwhile, major elements (Fe2O3, CaO, P2O5), minor elements (Cu, Zn) and REEs are highly enriched in Unit III compared to the upper two units. All these elements other than Fe reflect the fraction of biogenic apatite, which indicates higher fraction of biogenic components in Unit III. This is also supported by higher amount of smectite formed by the consumption of siliceous biogenic components. The reduced supply of terrestrial material and/or increased productivity of surface water at the time of Unit III deposition are attributed to Pliocene warming preceding Northern-pole glaciation during Quaternary. Unit III also includes clinoptilolite and unidentified 8Å mineral, likely amphibole, that are absent in Units I and II, suggestive of the possibility of different source region and/or materials during Pliocene. Higher contents of Mn and Fe in Unit III are likely due to the high fraction of Mn-oxide that was formed by diagenetic process after deposition.

Jan 1, 2003

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 James R. Hein

A new data set of cobalt-rich ferromanganese (Fe-Mn) crust chemistry has been completed for the first detailed sampling of a latitudinal crossing of the Pacific equatorial zone of high biological productivity. Samples were collected in January-March, 1999, during the AVON 2 cruise aboard the R.V. Melville, Scripps Institute of Oceanography. Samples were collected from 4.6° N to 9.2° S latitudes along two ridges, the Marshall Islands-Gilbert Islands ridge (4.6° N to 3.5° S) and the Howland Island-Tokelau Islands ridge (1° N to 9.2° S). The two ridges are offset east-west in the region of overlapping latitudinal sampling by about 466 km. We determined the concentrations of 48 elements for 147 samples from 39 dredge hauls taken on 33 seamounts and island flanks that occur between the Marshall Islands to the northwest and Samoa to the southeast. Element concentrations can be examined as varying spatially and with water depth in the ocean and we examine those relationships based on statistical analysis of the chemical and spatial data. The mean Fe/Mn ratio of 1 and mean Co content of 4645 ppm are typical of West Pacific hydrogenetic crusts; but the mean Co content is low compared to those of some equatorial North Pacific sites, such as the Marshall Islands and Johnston Island EEZs. In contrast, the mean Cu concentration (1540 ppm) is 35% higher than the mean concentration for Pacific Ocean Fe-Mn crusts (998 ppm). Another striking difference is the 40% higher Ba concentrations (mean 3107 ppm) compared to typical Central and West Pacific crusts (mean 1876 ppm); but Ba concentrations are lower than those in California continental-margin Fe-Mn crusts (mean 4085 ppm). A final significant difference in Fe-Mn crust chemistry is Zr concentrations, mean 921 ppm (maximum 1523 ppm), which is about 30% higher in this data set compared to the previously determined mean value of 613 ppm for Central and West Pacific crusts. Zirconium has a strong positive correlation with Ba and a weak positive correlation with Mn.

Jan 1, 2003

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 Henrik Schiellerup, Irene Zananiri, Johan Nyberg, Thomas Kuhn, Luis Somoza, Teresa Medialdea, Maria Judge, Pedro Ferreira, Gerry Stanley, Javier González

The GeoERA Co-Fund action is a joint contribution of 48 national and regional Geological Survey Organisations from 33 European countries “Establishing the European Geological Surveys Research Area to deliver a Geological Service for Europe (GeoERA)”. This is an ERA-NET action under Horizon 2020. The aim of GeoERA is to fund transnational projects contributing to the best use and management of the subsurface, addressing the following four themes: Geo Energy, Ground Water, Raw Materials and Information Platform. The European Commission recognises the significance of raw materials through its Raw Materials Initiative (RMI), the European Innovation Platform on Raw Materials (EIP-RM) and Horizon 2020 funding, specifically through Societal Challenge 5 – Climate Action, Environment, Resource Efficiency and Raw Materials. The GeoERA Raw Materials Theme will contribute to research and innovative developments for minerals inventory, minerals yearbook, exploration, mapping, modelling, metallogeny and critical raw materials in the pan-European framework including the sea. A major element in Europe’s long term economic strategy is to ensure security of supply for strategic and critical metals as part of the Blue Growth Strategy developing sectors that have a high potential for sustainable jobs and growth as seabed mining. The project MINDeSEA results of the collaboration between eight GeoERA Partners and four Non-funded Organizations at various points of common interest for exploration and investigation on seafloor mineral deposits. The Geological Surveys of Spain, Germany, Greece, Ireland, Norway, Portugal, Sweden and Ukraine are organisations with responsibility for coastal, marine geological investigation and mineral resources studies and mapping in their respective countries. The Non-funded participants: the Instituto Português do Mar e da Atmosfera; the United States Geological Survey; the All-Russia Scientific Research Institute for Geology and Mineral Resources of the Ocean; and the Geosciences Institute, host important databases, they have an international reputation for excellence in both science and technology, and are internationally-known experts on seafloor mineralisation and hydrothermal systems. This project addresses an integrative metallogenetic study of principal types of seabed mineral resources (hydrothermal sulfides, ferromanganese crusts, phosphorites, marine placers and polymetallic nodules) in the European Seas. The work program includes all the regional seas around Europe comprising the Atlantic Ocean, the Mediterranean Sea, the Baltic Sea and the Black Sea (Fig. 1). The MINDeSEA working group has both knowledge of and expertise in such types of mineralisation, providing exploration results, sample repositories and databases to produce innovative contributions. The importance of submarine mineralisation systems is related to the abundance and exploitation-potential of

Jan 1, 2018

By Jonguk Kim

Hydrothermal exploration aboard the R/V Onnuri was performed along the northern Central Indian Ridge (CIR) between 8°S and 12°S in January 2010. The main objectives of this first Korean research cruise on mid ocean ridge system was 1) to understand the nature of spreading segments of the northern CIR area, where no systematic survey have been operated before, by mapping and sampling of volcanic rocks and 2) to discover new hydrothermal venting along the spreading center of northern CIR. During the first leg (IR09 Leg1) bathymetric data, in ~50 km width, were collected by multibeam echo sounding system (EM120), which reveals the exact location and structure of axial rift valley of northern CIR between ~ 8°S and 17°S. Then, rock sampling and CTD casts and tows were performed in northern half of the multibeam survey area in the second leg (IR09 Leg2). The results of bathymetric survey clearly display ocean core complex between 10°S and 11°S. The ocean core complex is featured by topographic-high area with corrugated surface. Lineament of corrugations of the ocean core complex are clearly perpendicular to abyssal hill direction which are triggered by symmetric-normal faults. Symmetrical and asymmetrical segments are characterized by parallel abyssal hills and ocean core complex and/or subparallel abyssal hills, respectively. Geochemical analyses of basaltic glasses from spreading axis show geographic trend of increasing of incompatible elements north to south along the spreading axis, which might be influenced by Reunion hotspot plume. However, local but clear enrichment of incompatible elements is observed in volcanic lava from segment 2, which suggests possible local mantle heterogeneity of uncertain source. Lots of serpentinite and gabbroic rocks with coarse-grained feldspar was recovered in the ocean core complex. Ultramafic and/or mafic rocks indicate the gentle-domed block was traveled from upper mantle. Along the spreading axis of the northern CIR, significant hydrothermal plume signatures were detected by CTD castings and tows. Plume signatures were observed at all 5 surveyed segments, suggesting vigorous hydrothermal activities along the northern CIR. However, the optical signals (light transparency and backscattering) of the nearly every cast along the axial valley of the CIR showed increased background level, which might be due to higher level of suspended particles within the axial valley not only by widespread hydrothermal plumes but also by other processes like resuspension. Onboard dissolved methane analysis indicates that the greater part of the plume signals are originated from hydrothermal venting, not by resuspension. However, more detailed examination, including analyzing additional hydrothermal tracers, need to distinguish actual hydrothermal plume signature.

Jan 1, 2010

By Jonguk Kim

Hydrothermal sulfides were recovered from the16°50?S triple junction area in the North Fiji Basin, at a water depth of ca. 1900 m. The chimney samples can be divided into three groups according to their major metal contents: 1) type 1 (Fe-Cu-rich), 2) type 2 (Fe-Cu-rich with minor Zn), and 3) type 3 (Zn-rich) chimneys. Type 1 chimneys are mainly composed of chalcopyrite and pyrite, and are enriched in elements commonly precipitated under high temperature conditions (> 300°C), such as Cu, Co, Mo, and Se. Type 3 chimneys consist dominantly of sphalerite and marcasite with traces of pyrite and chalcopyrite, and are enriched in elements commonly associated with low temperature (150 to 250°C), such as Zn, Cd, Pb, As, and Ga. Type 2 chimneys show mineralogy similar to that of type 1 chimneys but their metal contents range between type 1 and type 3 samples. Trace element compositions of basaltic rocks indicate that magma generation in the triple junction area was influenced by two different sources: N-MORB and E-MORB. Sulfur and lead isotope patterns of the hydrothermal chimneys show distinct differences between the type 1 and type 3 chimneys. For example, type 1 sulfides are depleted in 34S and have lower Pb isotope ratios compared to type 2 and 3 chimneys. The d34S values (0.4 to 5.6?) of chimney sulfides are typical range of sulfur isotope composition of sediment free mid-ocean ridge hydrothermal system. Type 2 and 3 sulfides show slightly higher d34S values than type 1 sulfides, which can be explained by subsurface boiling of hydrothermal fluids followed by mixing of saline solutions with ambient seawater. Lead isotope compositions of the chimneys indicate that the Pb in type 1 and type 3 chimneys originates from hydrothermal leaching of N-MORB and E-MORB volcanic rocks, respectively. Considering that both these chimneys are located in the same area, our model suggests that type 1 chimneys formed by hydrothermal circulation controlled by an intrusion of N-MORB magma; the fluids were not influenced by boiling during the formation of type 1 chimneys. In contrast, type 3 chimneys are younger and were formed by hydrothermal circulation closely related to E-MORB magma intrusion at shallower depth. The necessary conditions for phase separation of the hydrothermal fluids that formed the type 3 chimneys might result from changed P-T conditions in a shallower high-temperature reaction zone beneath the hydrothermal venting site. Under these conditions the fluid may cross the two-phase boundary for seawater, ensuring subcritical phase separation. The mineralogical and geochemical properties of these chimneys suggest that type 1 and type 3 chimneys were probably black smoker and white smoker, respectively. Type 2 chimneys might be product of low-temperature replacement of type 1 chimneys, which is related to formation of type 3 chimneys.

Jan 1, 2005

The Brothers hydrothermal system is host to two very contrasting vent fields and to date, is the only known example of this kind for any submarine arc volcano in the world. Firstly, there is the NW caldera field. It is perched on the caldera walls and is up to 1,200 years old, and represents a more ?mature? system dominated by water/rock interactions, though there is also evidence for magmatic contributions to the hydrothermal fluids. It is host to relatively high temperature (~300°C), focused venting of metal-rich fluids. Large Cu- and Zn-rich sulfide chimneys occur at this site, with high concentrations (up to 90 ppm) Au apparent in some chimneys. Vent fluids of the NW caldera site show sub-seafloor phase separation is occurring at this site. Silica concentrations in these vent fluids are consistent with the vent fluid temperatures. Secondly, there is the cone vent field that is much younger, and which sits atop the summits of a main cone (the Upper cone) and an adjacent satellite cone (the Lower cone) that occur inside the caldera, near the southern caldera walls. This field is dominated by S-rich vents with vent fluids more diffuse, lower in temperature (<120°C), very gassy and acidic (to pH 1.9), and relatively metal-poor. Fluids of the cone site have Mg and SO4 concentrations higher than seawater values, indicating these ions have been added to the hydrothermal fluid and are not being depleted via normal water/rock interactions. Variability occurs between the two cone vent fields, with the diffuse discharge observed at the Upper cone volumetrically small and chemically different from the Lower cone. For example, from the vent fluid Mn, Li, Rb, and Cs concentrations, it is apparent that the Lower cone has experienced a lower degree of water/rock interaction (i.e., more reaction) than the Upper cone. Vent fluid pH is higher for Lower cone, consistent with more reaction and neutralization of acidic gases. Fe/Mn is lower at the Lower cone due to decreased Fe solubility at the higher pH. The lowest pH sample (1.9) is from the Upper cone that has 39.4 mmol/kg of SO4, consistent with input of magmatic SO2 and disproportionation to sulfuric acid and S or H2S. Thus, the Upper cone site could be interpreted to have a shorter reaction path and residence time between the point of magmatic degassing and the seafloor venting than the Lower cone site. Isotopic compositions of the NW caldera and cone vent fluids show evidence for magmatic water with negative dD and d180 values, while 3He/4He values show the Brothers hydrothermal system has shifted towards more magmatic conditions over the past several years with both sites affected by magmatic events. Similarly, vent fluid sulfide d34S values and those for sulfide minerals from NE caldera chimneys also indicate disproportionation reactions involving magmatic SO2. Minerals such as chalcopyrite, bornite, chalcocite, covelllite and euhedral grains of hematite occurring in high temperature chimneys from the NW caldera site are consistent with a more oxidizing, magmatic fluid, while bulk sulfide geochemistry data show evidence for a higher temperature suite of elements (e,g., Mo, Co, Se) associated with Cu-rich chimneys. Gold mineralization occurs in these high temperature chimneys and is associated with the most recent deposition of high concentrations of Cu, where d34S values are most negative. Geophysical evidence suggests that the top of a magma chamber occurs ~2.5 km below the caldera floor, beneath the cone site in the SSE quadrant of the volcano. Very low velocities of <1 km-2 are seen in the seismic data between the magma and the seafloor, and are indicative of gas release. Harmonic tremor data provide evidence for a 500 m pipe-like ?conduit? located above the magma chamber (and below the cone), linking it with the overlying hydrothermal system, providing a mechanism for magma-derived metals to enter the hydrothermal system under the cone site. The NW caldera and cone sites are considered to represent stages along a continuum between magmatic-hydrothermal and water/rock-dominated end-members.

Jan 1, 2010

By Jae-Hyung Park

Since the Industrial Revolution, the land resources have been decreased rapidly as the industrialization. And this phenomenon brings to our mind an interest in deep-sea resource(manganese nodule). Hence, Korea has been participated in the development project of exploiting manganese nodule since 1983. Hwang and cho(1998) studied the economic efficiency evaluation of manganese nodule carrier. But they used the TAMU(Texas A&M University) model, and assumed deadweight and velocity of bulk-carrier. If we use some optimization technique, more economic manganese nodule carrier can be selected and evaluated without limited assumption. In this study, we evaluated the economic efficiency of manganese nodule carrier using genetic algorithms(GAs).

Jan 1, 2003

By Elizabeth McIsaac, Wylie Spicer

"In July 2016 the International Seabed Authority (the “ISA”) released a first working draft of its mineral exploitation regulations as well as the standard contract terms for mineral resources in the Area, for which stakeholder input was sought in late 2016. In January of 2017 the ISA released a discussion paper on environmental matters related to these draft regulations. The ISA is now in the process of further developing its draft exploitation regulations and standard contract terms to ensure that seabed mining is carried out in an environmentally sound way for the common benefit of mankind.As the regulator of the “Area”, the ISA can draw lessons from onshore mining regulators and offshore petroleum regulators for their experiences in legislative drafting to smoothly and safely oversee project development, implementation, and closure. However, one of the unique challenges that the ISA faces in regulating private industry is its status as an international organization and not a sovereign nation, which results in a significantly different legal relationship between the regulator and the regulated. The result is that the exploitation contract is the sole legal connection between the mining proponent and the regulator for the exploitation phrase of the project.Accordingly, in the regulatory development process, the ISA must carefully consider which rights and obligations are set out in the exploitation contract versus the regulations. This decision will dictate the flexibility the ISA will have to modernize the conduct required of mining proponents in response to changing best practices in the industry, technological progress, and advances in the understanding of the marine ecosystem. As the first working draft of the exploitation regulations sets out an initial contract period of twenty years, it is crucial for the ISA to carefully consider the rights, obligations, and procedures it agrees to in the exploitation contract, as unilateral amendment will not be possible after contract execution."

Jan 1, 2017

By Tony van der Steen

Subsea mining system are designed for the following, principally different, tasks: Dreding - The destruction and removal of seabed sediments overlaying the bedrock. Cleaning - The competence of the system to systematically remove the deposits from an undulating hard bedrock with irregular pulleys, channels and fissures. Factors that influence the choice of dredging equipment for a specific project are project requirements such as environmental conditions, location and water depth. However, the most important selection criteria are soil conditions. As a consequence, possible dredging systems, must be evaluated for the following, principally different, characteristics: Dredging proficiency - The destruction of the strata by the equipment. System stability - The capability of the soil to support the subsea equipment The above parameters are determined by the strength characteristics and the bearing capacitv_ of the soil. The author describes the processes involved in excavating the subsea deposits and (transporting the gathered soil as a water-soil mixture to the surface using different excavation and transport methods.

Jan 1, 1998

By Michael R. Gipp

Marine Mining Inc. is currently exploring for marine alluvial gold and diamonds on a prospecting licence over a concession that covers 10,000 km2 of the continental shelf of Ghana. The boundaries of the concession extend from 0 30&apos;W to 2 40&apos;W, and between the shoreline and approximately the continental shelf edge north of 4 30&apos;N. This concession extends from Kikam Beach in the west, to Senya Beraku in the east, a distance of approximately 240 km, and seaward an average of about 40 km. The concession is entirely underwater, with the exception of the estuaries of the Ankobra and Pra Rivers. Ghana has been a large source of alluvial gold, with historical production exceeding 25 million ounces. Southwestern Ghana is characterized by Precambrian rocks, which have been folded into a number of NE-SW trending synclines and anticlines. The most significant feature of the Birimian rocks is the presence of evenly spaced gold-bearing greenstone belts. They are 10-15 km wide, separated by about 90 km, separate basins filled by folded metasediments and granitoids. The rivers that enter the concession drain most of the exposed gold-bearing belts of Ghana. Given that approximately 2 km of erosion has taken place since the Mesozoic, and that gold mines on these belts boast proven reserves of over 55 million ounces, it is likely that large amounts of gold have been eroded out and carried to the sea. Coastal fractures, related to Precambrian structures reactivated during Mesozoic rifting, are responsible for the physiography of the coastal area, which consists of high-relief horsts separated by grabens that have been occupied and infilled by rivers or by finer sediments during times of elevated sea level. These fractures were loci of gold mineralization during the Precambrian, and are the source of alluvial gold in rivers confined by them.

Jan 1, 1998