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By Akira Usui

Platinum is one of the most rare elements in the earth?s crust, but it is significantly enriched in some hydrogenetic ferromanganese crusts in the ocean. The element is essential to the electric industry and is believed to be of importance as a raw material a future fuel-cell industry. The earlier reliable chemical analysis of platinum-group elements (PGE) of ferromanganese crusts have indicated a variety of concentrations of Pt in the range of 100 ppb to a maximum of about 1 ppm, but little is known about the elemental abundance in ferromanganese crusts on fine-scale, or the geochemical behavior and form of the element. The chemical and mineralogical forms of platinum and its group are important in planning the methods of mineral exploration and extraction of the elements from of ferromanganese crusts. We attempted to characterize the distribution pattern within a cobalt-rich crust on the fine to microscopic scales by using reflecting microscope, scanning electron microscope/energy-dispersive spectroscopy, electron microprobe X-ray analysis (EPMA), ICP-mass spectroscopy, X-ray absorption near edge structure (XANES), small-focus XRF, and X-ray diffraction (XRD). These data indicated a wide range of Pt concentration from 150 to 700 ppb within a crust, though we found no distinct inter-element correlation or mineralogical control. Under the reflecting and electron microscope, no distinct Pt-bearing minerals or particles were identified. Small-focus XRF indicated no uneven distribution in any particulate matter, but all areas are less in abundance than the detection limit of about 10 ppm. Our tentative conclusion is that zero valence Pt0 (as suggested by XANES) is dispersed in the form of submicroscopic material most probably within ferromanganese minerals, and therefore, Pt-rich mineral particles may not be a major carrying phase.

Jan 1, 2005

By Eric J. Foell

The Offshore Technology Conference (OTC) was founded in 1969 when a group of scientific and technical societies organized an annual conference and exhibition dedicated to technologies used in the offshore oil, gas and mining industries. Currently, OTC is sponsored by 12 industry organizations and societies. These include: American Association of Petroleum Geologists (AAPG); American Institute of Chemical Engineers (AIChE); American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME); American Society of Civil Engineers (ASCE); ASME International Petroleum Technology Institute; Institute of Electrical and Electronics Engineers/Oceanic Society (IEEE-OES); Marine Technology Society (MTS); Society of Exploration Geophysicists (SEG); Society for Mining, Metallurgy, and Exploration (SME); Society of Naval Architects and Marine Engineers (SNAME); Society of Petroleum Engineers (SPE); and The Minerals, Metals, and Materials Society (TMS). OTC also has two endorsing organizations, the International Association of Drilling Contractors (IADC) and the Petroleum Equipment Suppliers Association (PESA), as well as 6 supporting organizations that include the American Petroleum Institute (API), the Independent Petroleum Association of America (IPAA), the Institute of Marine Engineering, Science, and Technology (IMEST), the International Association of Geophysical Contractors (IAGC), the National Ocean Industries Association (NOIA), and the United Kingdom Offshore Operators Association (UKOOA). From its earliest years, the OTC has been held during the first week of May in Houston, TX, initially at the Albert Thomas Convention Center where OTC?69 drew 4200 attendees and 200 exhibitors. As the conference grew and became established as the world?s foremost event for the development of offshore resources in the fields of drilling, exploration, production, and environmental protection, the venue was changed to the Astrodomain Complex, with technical paper sessions and most exhibits taking place in the Astro Hall. The numbers of attendees and exhibitors varied somewhat over the years, primarily in accordance with the fortunes of the international oil and gas industry. At its height in the early 1980s, OTC registered attendance exceeded 100,000 with more than 2500 exhibitors forcing expansion into the Astro Arena and even the Astrodome.

Jan 1, 2005

By Robert Ditchburn

Within New Zealand?s extended EEZ there exists a vast submarine hydrothermal mineral resource associated with the Kermadec intra-oceanic arc. Along this arc more than thirty submarine volcanoes have been explored by GNS-lead researchers and, of these, c. 60% are known to be hydrothermally active and a site of active seafloor mineralisation. Assessment of whether this mineralisation is economically viable in terms of grade and tonnage is now underway. A key aspect of these investigations is determining the age of the mineralization which will have a direct bearing on its mode of formation, the time elapsed to amass an economic deposit and, ultimately, its capacity for sustainable extraction. Intact barite-rich ?black-smoker? chimneys similar to that depicted here (86 cm long) have been recovered from Brothers volcano in the southern part of the arc. These and other hydrothermal deposits provide evidence of active volcanic massive sulphide (VMS) mineralisation along the arc, the age of which can be determined from the disequilibrium between isotopes within the thorium or uranium decay chains. A chimney from Mariana arc has also been dated using these radiometric methods. The principle dating technique for chimneys up to 15,000 years old uses the decrease in 226Ra/Ba due to radioactive decay after the VMS was deposited. An initial ratio is obtained from chimneys that are proven to be less than 100 years old and this involves dating with 210Pb, 228Ra and 228Th that have short half-lives compared with 226Ra.

Jan 1, 2005

By M. E. Williamson

In September 2005 Williamson & Associates, Inc. delivered the BMS2 remotely operated seafloor coring system to the Japan Oil, Gas & Minerals National Corporation (JOGMEC). During acceptance trials aboard the JOGMEC research vessel R/V Hakurei Maru No. 2 the BMS2 successfully recovered 7.44 m of rock core in 3377 m water at a site near the crest of a seamount about 500 nm SE of Japan. Hydrogenous ferromanganese oxide crust, basaltic lava, sandstone and volcanic sediments were sampled with near 100% core recovery. The BMS uses rotary rod coring tools to collect samples to a maximum depth of 30 m in water depths up to 6000 m. Depending on bottom type to be sampled, the BMS tool magazine can be loaded with various drilling tools including core barrels with different bit types, drill rod and bore hole casing. The drill has 9 video cameras, a suite of sensors and 60 hydraulic functions powering thrusters, telescoping legs, seawater pumps and all of the standard drilling controls. The BMS provides deep water investigations with the functionality of conventional diamond bit rod drilling currently the mainstay of exploration programs in land mining.

Jan 1, 2005

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 Yves Fouquet

Recent exploration demonstrates that hydrothermal systems related to upper mantle ultramafic outcrops are common in the modern ocean. Most sites are located on slow spreading ridges with a low magmatic budget. Volcanogenic Massive Sulfide (VMS) deposits, associated with basalt, along the Mid Atlantic Ridge (MAR) are volcanically controlled near the topographic highs at the center of the segments. Three preferential settings are identified for ultramafic sulfide mineralization: 1) Off axis, on rift valley walls, near the amagmatic ends of the segments; 2) Non-transform offsets and 3) Ultramafic dome structures at the ridge transform fault intersection. The upper surface of these domes is often interpreted as a detachment fault. Three processes are considered for driving hydrothermal cells in ultramafic rocks: 1) regional heat flow at the ridge axis 2) Cooling of a deep gabbroic intrusion and 3) exothermic heat produced during serpentinisation. Along the Mid Atlantic Ridge, four types of ultramafic hydrothermal mineralization are observed: 1) High temperature (>350°C) sulfide mineralization related to low pH fluids, (ex. The Logachev field at 14°45? N and the Rainbow field at 36°14 N); 2) Medium temperature carbonate chimneys (<100°C) related to high pH fluids (ex. The Lost City site at 30°N); 3) Low temperature diffuse venting associated with extremely high methane discharge and pervasive alteration and silicification of both volcanic and ultramafic rocks (ex : The Saldanha field at 36°34 N); 4) Stockwork mineralization and quartz veins with sulfides related to gabbroic intrusions within ultramafic rocks (15°N). When compared to mineralization in a basaltic environment, sulfide deposits are enriched in copper, zinc and specific elements related to an ultramafic rock source such as Ni and Co. They are also significantly enriched in gold which, unlike in basaltic environments, has a bimodal occurrence both in low temperature Zn-rich assemblages and in high temperature Cu-rich mineral assemblages. The Cu-Zn-Co-Au deposits along the Mid Atlantic Ridge seem to be more common than on land where few similar VMS deposits are known. We consider that ultramafic VMS deposits on slow spreading ridges constitute a specific marine type of mineralization that is less easily than back arc deposits, incorporated into the continent during obduction processes.

Jan 1, 2004

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 Fredrik Søreide

Several potential marine mineral deposits of various types have been identified within the Norwegian EEZ. The Norwegian University of Science and Technology has recently designed and built a new remotely operated vehicle (ROV) system for scientific investigations of the deep-ocean and seafloor. A program to locate and investigate the most interesting of the identified marine mineral deposits using the new ROV system is underway. The ROV has been designed for detailed survey and sampling tasks. Although initially built for a major marine archaeology project, the design is equally suited to locate and investigate marine mineral deposits. The ROV is equipped with a high precision multi-sensory package that consists of various high quality cameras and lighting systems (together with state-of-the-art video and photo mosaic systems), several sonar systems, magnetometer and various other sensors. The ROV is also equipped with a 7-function manipulator arm and an excavation system. Internal collection baskets are used to store material for retrieval to the surface. A closed-loop control dynamic positioning system is used for detailed positioning of the ROV. Position data and other information are stored in a digital data management system. The ROV will also be used together with a specially developed remotely operated tool (ROT). The size and shape of this benthic lander can be adjusted before it is carefully lowered to the seafloor. The ROV can be docked on a moving platform on the ROT, to do detailed scientific investigations. The ROT can also be equipped with a separate sensor and system package, including drilling, excavation and coring units. This paper will present the new remotely operated system and the planned projects in Norway.

Jan 1, 2004

By B. J. Bluck

Diamond mega-placers, in order to rank amongst the primary diamond deposits, are defined as => 70 m carats at =>95% gem quality. There is only one mega-placer known and that is found along the coast of southwestern Africa fringing the Kaapvaal craton. Placers are classified as residual when they are left on the craton, transient when being eroded into the exit drainage and terminal. Terminal placers, in being the final depositories of diamonds off the craton, have the greatest probability of being a mega-placer and such is the case in the placer deposits near the Orange River mouth, southwestern Africa. There are four main groups of conditions leading to the development of a mega-placer: the craton, the drainage, the nature of the environment at the terminus and the timing. The craton, in its role as the producer of diamonds is significant in respect to its size, diamond-fertility, the degree to which diamonds from successive kimberlite intrusions have been retained there and their availability to the final drainage yielding the mega-placer. Cratons in being buoyant have a tendency to leak diamonds into surrounding basins but in being incompressible often have orogens converge onto them resulting in lost sediment being returned as foreland basin fills. In order to concentrate a bulk of diamonds the drainage basin has to be large with a high proportion of it on the craton. The drainage yielding the mega-placer should ideally not have been preceded by older drainage and other systems that may have robbed the craton of earlier diamonds. The exits of diamonds from the craton need to be few in order to focus on their supply and the drainage network needs to be efficient in order to remove the maximum volume of diamonds off the craton. This efficiency and the focused termination is best achieved by the rejuvenation of a pre-existing drainage network. The drainage should be young enough to yield host sediments friable enough to allow brittle diamonds to be recovered from them.

Jan 1, 2004

By G. Cherkashov

A new hydrothermal field with massive sulfide deposits was discovered in 2004 at 16º 38.4?N, 46º 28.5?W on the Mid-Atlantic Ridge. Hydrothermal signals had already been recorded from bottom waters and sediments in this area during cruise 19 of R/V Professor Logatchev in 2000. This site was revisited during the 24th cruise of R/V Professor Logatchev in February 2004 when samples of massive sulfides were recovered and video records of the deposits made. The basalt hosted hydrothermal field is situated at a depth of 3700-3750 m, 600 m above the inner floor on the eastern slope of the rift valley. Structurally, the new field is located at the intersection of a deep along-axis marginal fault and a transverse sub-latitudinal dislocation. Six sulfide mounds as well as associated metalliferous sediments were mapped (sampled and/or recorded by video profiling) within the hydrothermal site. The largest ore body, 500 x 225 m, in the southern part of the field consists of small blocky talus and relics of sulfide chimneys partly covered by iron oxyhydroxides. The chimneys are 1-5 m high. The southern and western boundaries of the massive sulfide deposit have not yet been delineated. More than 1,100 kg of massive sulfides and stockwork mineralization were sampled at 7 sites by dredge and TV-grab. Everywhere, iron sulfides were the principal minerals present. Pyrite in association with lesser amounts of chalcopyrite occurs in both massive sulfides and stockwork mineralization. Of particular interest is the chalcopyrite-siliceous stockwork where silicified and chalcopyritized basalts are intruded by a network of chalcopyrite veinlets. These zones could be fairly thick and enriched in base metals. Sphalerite was very rare.

Jan 1, 2004

By D. S. Limpenny

Marine benthic habitats are vulnerable to the influence of a wide range of anthropogenic activities (e.g. sand and gravel extraction, dredged material disposal and trawling). Traditionally, benthic ecologists have relied on point sampling techniques such as grabs, corers and dredges to provide information on the physical nature of the substrates and their associated benthic fauna. However, information of this nature only relates to the specific point on the seabed from which the sample was collected and the interpolation of such data to predict the wider distribution of substrata and associated fauna may be unreliable. Our approach uses a range of acoustic, photographic and physical sampling methodologies to produce continuous acoustic coverage maps which can be used to assist with the interpretation of faunal distributions. This approach has been used to assess the impacts of marine sand and gravel extraction at the seabed at two sites off the east coast of England in the southern North Sea. The first study site (designated ?Area 222?) is located 20km off the southeast coast of England and was surveyed in 2001 using sidescan sonar, single beam bathymetry, seabed photography and also a 0.1m2 Hamon grab for the collection of benthos and sediment samples. The main objectives of this investigation were to provide an indication of the spatial distribution of the sediments and macrofauna in the wider area encompassing the dredged site, to evaluate the scope for the effects of marine sand and gravel extraction to extend beyond the boundaries of the site and to provide a wider geographical context for time series investigations. At this site, an acoustic basemap was utilised in conjunction with faunal sampling and photographic groundtruthing, to determine the nature and distribution of the seabed sediments and their associated features. Disturbances at the seabed arising from historic sand and gravel extraction activities were mapped, and this information was helpful in establishing biological cause and effect relationships. The acoustic basemap was also used to target biological reference sites against which the effects of adjacent man-made disturbances could be evaluated.

Jan 1, 2004

By Alexander Malahoff

Field observations and sampling of land-based and submarine hydrothermal and geothermal sites show a definite link between the geological setting, fluid geochemistry and specialized assemblages of microorganisms found at these settings. Three initial sites have been chosen as a basis for these studies. The first site is located on hydrothermal vents in pit craters on the submarine volcano Lo?ihi (Hawai?i) at a water depth of 1,300 meters. The second site is within the geothermally active vents, ponds and lakes of the Taupo Volcanic Zone of New Zealand. The third site extends along the chain of volcanically and hydrothermally active volcanoes of the Kermadec-Tonga arc and back-arc system. To focus our work in New Zealand, a geomicrobiology field and experimental center has been established in Wairakei, New Zealand, with the relevant genomics, proteomic and bioinformatics work being conducted at the University of Hawaii. As part of a partnership between the University of Hawai?i, the Institute of Geological & Nuclear Sciences (GNS) and Victoria University of Wellington, a new interdisciplinary graduate course in geomicrobiology will be taught at Victoria University beginning next year. Since mineral-microbial interactions have been occurring for the past few billion years and these interactions have led to where one generates the other, a metal-bacteria research program has been initiated at GNS using arsenic-gold and other metal-bacterial interaction processes as a research objective. In this research program, we have completed the full genome of a new species of marine bacterium Idiomarina loihiensis from the Lo?ihi hydrothermal vents and identified specialized microorganisms living in pH 0.3 geothermal vent waters of White Island, New Zealand. The multidisciplinary approach to study the process of accumulation of metals in the hydrothermal systems clearly shows the path of how bacterial-mineral interaction can precipitate metal deposits. These studies will lead to new avenues for biomining, bioremediation and the understanding of the origins of life.

Jan 1, 2004

By Richard H. T. Garnett

Large scale, profitable, offshore mining of cassiterite started in 1907 around the coast of south Thailand and continues today in Indonesia. The more complex marine mining of diamonds commenced in the early 1960?s and is now an established industry off the coast of Namibia in southern Africa. The activities have involved many diverse organisations, and have required the development of new marine mining equipment. De Beers Marine, more recently as contractor to Namdeb, has been the dominant producer since 1989. Smaller, public, mining companies, registered in South Africa, Canada and the U.K., have achieved mixed performance results, but the total annual revenue from offshore diamonds now exceeds about US$ 180 M. With the benefit of hindsight, there are some useful lessons to be learned from the experiences. Mining of placer deposits at sea is more difficult and more costly than on land. It justifiably commences in response to a market demand for a product that cannot be supplied in sufficient quantity from onshore sources, not because the marine resource exists. The high costs can be offset in places by submarine grades so high that they have not been seen on land for a century. Technical and commercial success requires a combination, and a sufficiency, of ore reserves, capital, experienced people, and technology. Economic viability is not achieved easily and some diamond mining companies have experienced a very short productive life, terminating in their acquisition or liquidation. The reasons for failure in marine mining, regardless of whether the product is diamonds, gold, or tin, invariably are similar and fall into two categories. Those outside a company?s control include the sea conditions, taxation and fiscal climate, security of lease tenure, and the diamond market. The others, assignable to the company, provide important instructions for those who may aspire to advance the cause of marine mining.

Jan 1, 2004

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 A. Ivanova

The continental shelves occupy a vast area of Russia and contain complexes of commercial placer minerals. Of prime importance are Cenozoic placers of valuable minerals including gold, cassiterite, diamonds, chromite, platinoids, and minerals of titanium, zirconium and rare earth elements, biogenic amber and fossil ivory (1). Commercial placer minerals are associated with shelf placer formation zones (SPFZ). These zones are located at junctions of marginal orogens and shelf troughs in morphostructures where upwarping, subsidence, and sign-variable neotectonic movements are not significant. The SPFZs are characterized by ancient buried leveling planes with mantles of waste, series of wave-cut aggradation terraces on land and beneath the sea, and drowned and buried stream valleys. The occurrence of mineral placers in the SPFZs was caused by endogenic mineralization and exogenic placer hosted formation. Concentrations of commercial biogenic minerals are associated with areas of burial of biogenic material (release of resins by plants and theriofauna thanatocoenoses) and with their transition zones. Since the Oligocene, alternations in marine transgression-regression have dominated the shelf areas. This has resulted in the formation of polygenic placers. Climatic conditions are of great importance: warm and humid climate in the Paleogene-Neogene changed to colder climates in the late Pliocene (polar type sedimentation; formation of permafrost strata and sea glaciation). These events are responsible for the regularity in placer formation during the Cenozoic in which the early Cenozoic (Eocene-Oligocene-Miocene) and late Cenozoic (late Pliocene-early Pleistocene and late Pleistocene-Holocene) epochs are prominent.

Jan 1, 2004

By David Heydon

The big money is backing both manganese nodules and manganese crusts as the most likely deep ocean mining development by 2010, but seafloor massive sulphides of copper/gold/zinc offer an alternative bet for a start-up by 2010. A study of the ?form guide? or comparison of these resources provides direction on which resources are economic candidates for commercial deep ocean mining development by 2010. This paper covers the commercial and technical issues of exploration, resource definition, drilling/sampling, sea bed mining options, mine plans, environmental issues, legal tenure and capital and operating costs (i.e., profitability) of these two mineral types. Nautilus Minerals has just completed a pre-feasibility engineering study of mining sea floor massive copper/gold/zinc sulphides at 2,000 m depth. The Nautilus study reviewed a range of mining and lifting options, settling on tracked continuous drum cutter miners to produce 2 million tons per annum of high grade ore. Capital costs are shown to be at least 30% lower than a land based copper mine of the same production capacity. Likewise 75% of world?s copper would be produced at a higher operating cost that the proposed seafloor mine. This paper then draws on the Nautilus study for comparison with earlier feasibility studies by others on manganese nodule mining to predict the likely directions in deep ocean mining to 2010.

Jan 1, 2004

By James R. Hein

Rodriguez Seamount, located 150 km off the central California coast at the base of the continental slope, was studied using the ROV Tiburon aboard MBARI?s R/V Western Flyer, October 13-16, 2003. Fe-Mn crust and rock samples were collected along the SW flank of the seamount at water depths from 700 to 2100 m; bottom-water dissolved oxygen content (O2) and temperature were determined at each sample site. Fifty-three samples of bulk crusts, crust layers, and surface scrapes (~0.5 mm) were analyzed for 59 elements. Data allow for the correlation of crust compositions with precisely known water depths and seawater O2 measured at the actual site of sample collection. This is the first detailed study of Fe-Mn crust compositions in a region of strong continental-margin upwelling. Compared to open-ocean seamount Fe-Mn crusts, Rodriguez crusts have significantly higher (2-6 fold) mean concentrations of Fe (26.9%), Al (1.65%), Si (13.0%), Cr (82 ppm), Th (64 ppm), and Ag (1.7 ppm); and significantly lower (2-8 fold) mean concentrations of Ca, P, Bi, Co, Cu, Ni, Tl, and especially Te (8.2 times lower). All but one Fe/Mn ratio are >1 compared to <1 ratios for open-ocean crusts. O2 contents (0.35-2.03 ml/L) are nearly perfectly corrected with water depth and elements correlated with one are correlated with the other. The Fe-Mn surface scrapes represent 60-450 ka (mean 150 ka) of growth, whereas the dissolved oxygen contents of seawater represent an instant in time. Assuming that the entire sample set was affected uniformly by oceanographic changes, we suggest that correlation of elements with O2 may reflect oceanographic processes. O2 has a negative correlation with P, V, As, Fe, U, Be, Pb, Cr, Mg, Y, Bi, Te, and REEs (except Ce) and a positive correlation with aluminosilicate-hosted elements (Al, K, Rb, Cs). This later relationship is related solely to water depth, indicating that detritus shed down the seamount slopes accumulates in greater abundances in deeper-water crusts. Si/Al ratios indicate that the detritus includes a large component of biosilica produced by upwelling-mediated high productivity. These observations are supported by positive correlations of aluminosilicate-hosted elements with crust growth rates (range 1.2-13.0 mm/Myr). In contrast, other elements (Sr, Co, Mn, Mg, Te, As, Mo, V, W, U, Ti, Ni, REEs, etc.) are negatively correlated with growth rates. Growth rate has a weak positive correlation with O2. These compositional characteristics indicate that even though low-O2 seawater acts as a reservoir for Mn and associated elements and produces slow growth rates, which would allow for the concentration of elements and surface oxidation processes to occur, the high rate of input of detritus and high bioproductivity ameliorate the strong concentration of most metals. This dilution is significantly enhanced by the doubling of FeOOH in the crusts--the main cause of the generally high growth rates compared to open-ocean crusts. The high growth rates limit the oxidation of Co, Tl, and especially Te on the crust surface, which is reflected by their relatively low concentrations. Within the range of oxygen contents measured, O2 has less of an influence on crust chemistry than does the availability and incorporation of FeOOH and detritus.

Jan 1, 2004

By Graham Singleton

Around 235 million tonnes of marine aggregates have been dredged in the last decade from the UK continental shelf alone. The current distribution of marine aggregate production licence areas in North West Europe reflects the relationship between a variety of factors such as the natural distribution of deposits of sand and gravel, the demand for aggregates, the technical capabilities of the dredging fleet and environmental considerations. Whilst the sand and gravel deposits targeted by the marine aggregate industry are generally relict and therefore geographically fixed, the remaining factors have evolved over time and will continue to do so in future. Applications for new licences must not only reflect the current situation, but anticipate future trends. The main markets for marine aggregates are the construction industry, centred around the larger centres of population and coastal protection projects along the coastline of Europe. The aggregate industry as a whole does not create demand but simply meets it. Many factors influence the overall demand for aggregates and guidance exists for those in authority and industry who need to plan for the supply of aggregates. Adequate supplies should be maintained at the best balance of social, environmental and economic cost, whilst ensuring that extraction and development are consistent with the principles of sustainable development.

Jan 1, 2004

By Peter Halbach

Within the frame of the German-Indonesian cooperative Bandamin research project two short cruises (7 station days each) were carried out which led to the Flores-Banda basin located north of the active volcanic arc. This basin is part of a large island-arc subduction-collision system resulting from a complex plate tectonic situation in which three major plates collide with each other. The eastern part of the Sunda-Banda convergent margin also includes the transition from subduction of oceanic lithosphere to collision of the Australian continental crust with the arc. This transitional part is cut and displaced by various large obliquely striking fault systems. Thus, the south eastern and eastern arc segments represent geological conditions which are suitable for the development of hydrothermal convection and potential mineral precipitation. Our study area lies north of the transitional section between Flores and Wetar. We started with a high-resolution bathymetric mapping of 240 km2 in a region some 36 km north of the island of Lomblen. A small submarine neovolcanic ridge was discovered striking approximately NW-SE and consisting of several submarine volcanic structures. In the northwest of the study area, the active subaerial Komba Volcano (Batu Tara) marks the youngest continuation of the ridge system examined. From the ridge we collected fresh and hydrothermally altered volcanics with disseminated sulfides (pyrite, pyrrhotite, markasite, and chalcopyrite), together with ferrugenous gossans.

Jan 1, 2004

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