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By Timm Schoening, Greinert. Jens, Iason –. Zois Gazis

"Ferromanganese nodules are again of interest because of their high concentrations of Ni, Co, Cu as well as REE. With regards to an operational underwater mining industry, one of the main questions and important requests is to finding a method that can predict the abundance of nodules with high accuracy within reasonable time spans, without many requirements for ground truth data; and all these on an operational scale and ideally automated. In this regard, we present results of a study based on the combination of highresolution multibeam and optical data acquired by an AUV using specific machine learning techniques to reveal a detailed distribution of the Mn-nodules in correlation to the seafloor terrain. The accuracy of the method employed and results gained were validated and approved through comprehensive statistical analysis and by comparison to box-core data.Study AreaOur study area (AUV survey block G77) is located in the Clarion-Clipperton Zone (CCZ) (Eastern Central Pacific Ocean), an area that has been receiving international research and industrial attention for many years already (e.g. McKelvey et al., 1979; Bernhard and Blissenbach, 1988, von Stackelberg and Beiersdorf, 1991, Jeong et al. 1996). Block G77 covers an area of 9.5km2 in a depth between -4478m and -4536m. The area is characterised by gentle slopes 0-5° (0-3° in most of the area and only in the outer parts of the Block slopes can exceed 5°). The seafloor is characterised by moderate to low rugosity, the only exception being a small area in the eastern part, where sub-recent smallscale volcanic activity created 15 cone-shaped morphological features of up to 55m height and 150m width that are clustered in an area of 700 x 380m (Figure 1)."

Jan 1, 2017

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 Peter A. Rona

The recent discovery of the first black smoker-type hydrothermal venting and massive sulfide mineral deposits at a site in the rift valley of the slow-spreading Mid-Atlantic Ridge near latitude 26°N, longitude 45°W (Rona et al., 1986, Nature, 321: 33-37), demonstrates that a complete series of hydrothermal mineral deposit types exists at slow-spreading oceanic ridges (half-rate = 2 cm/y), similar to the series previously known at faster-spreading oceanic ridges (half-rate > 2 cm/y). The largest hydrothermal mineral deposit known at a seafloor spreading center is a stratiform massive sulfide body with bulk dry weight of about 100 x 106 metric tons in the Atlantis II Deep at the slow-spreading axis of the Red Sea. This observation invalidates the concept that size of a hydrothermal deposit is directly proportional to rate of seafloor spreading. Instead, the occurrence, grade and size of a hydrothermal deposit formed at a seafloor spreading center is controlled by anomalous chemical and physical conditions which may occur at extremely localized sites at the full range of spreading rates. The basic hydrothermal process involving subseafloor hydrothermal convection driven by magmatic heat sources appears to be similar at slow- and faster-spreading centers. However, differences exist in the periodicity of magmatic cycles that energize hydrothermal circulation (104 y at slow-spreading centers; 103 y at faster-spreading centers); in the distribution of hydrothermal sites along a spreading axis (estimated 100 km along slow-spreading centers; 10 km along faster-spreading centers); and in residence time

Jan 1, 1986

By Sang Joon Pak

Deep-sea mineral resources explored by Korea are categorized into mainly three types; manganese nodules, manganese crusts and seafloor massive sulfides. Manganese nodules have high Pt enrichment factors (EF=400, ore/crust ratios). Rare earth oxides (REO) contents from manganese nodules show from 0.037 to 0.302 REO% with mean value of 0.12%. Te and Pt are highly enriched in manganese crusts, displaying EFs of 10800 and 150, respectively. REO contents of manganese crusts are slightly richer than manganese nodules (0.013~0.387 REO%, average = 0.18 REO%). Seafloor massive sulfides deposits are featured by outstanding values of Se (EF=1300) well as In (EF=110). Au (0.8~26.3 g/t) and Ag (0.9~348.0 g/t) are another enrichment metals in SMS, although they belong to precious metals. Rare earth elements of SMS are meaningless as resources but REE are increasing in sediments overlying SMS. Heavy rare earth elements (HREE) from both manganese nodules and manganese crusts are typically higher than ones from land-based REE deposits. HREO grade and their portions of manganese nodules as well as manganese crusts are greatly similar to ion-absorbed type REE deposits in China, implying REE of subsea mineral resources are absorbed in nodules and crusts. Rare metals including REE could be exploited as by-production of commodities such like Ni, Co, Cu and so on. Rare metal resources from manganese nodules and manganese crusts are featured by low-grade and large scale deposits. Therefore rare metals in subsea mineral resources will add its economic values.

Jan 1, 2011

By Seung-Kyu Son

Environmental properties of the northeast Equatorial Pacific along 131.5 degrees west, between 5 degrees and 13 degrees north latitude, were investigated in association with changes in water column structures during the summer seasons of 1998 and 1999. Climatic disturbances such as El Nino and La Nina, should have affected this area during the study period. In 1998, a thermocline where temperatures rapidly decrease with depth, was formed at 90~110 m water depth. However, in 1999, a very fluctuating thermocline was observed with latitudes. As a result of changes in the water column structures, biological and chemical environment also showed fluctuation parallel to the changes in other physical parameters. Inorganic nutrient depleting areas, especially for nitrate+nitrite and phosphate, or oligotrophic regions were extended down to approximately 100 m depth, which coincided with the surface mixed layer depth. In the euphotic zone, depth integrated nitrogen (N) and phosphorus (P) values were 34 g-N/m2 (grams of Nitrogen per square meter of sea floor), 7 g-P/m2 in 1998 and 130 g-N/m2, 18 g-P/m2 in 1999, respectively. The results indicated that nitrogen (96 g-N/m2) and phosphorus (11 g-P/m2) are supported by up-welling and down-welling phenomena with convergence and divergence in the study area. Biological parameters in the water columns were largely determined by the physico-chemical environmental parameters. Subsurface chlorophyll maximum layers were coincided with the formation of seasonal thermocline. Copepods were the dominant group of zooplankton community at three sampling stations (N5, N6, N10) terms of abundance, which was the same results of previous surveys for the past 3 years. Among copepod populations, Oncaea sp., Oithona sp. Clausocalanus sp., Acarocalanus sp. and juvenile copepodites were dominant Appendicularians, foraminiferans and radiolarians were also dominant. To investigate diel vertical migration pattern of zooplankton, repeated samplings from the water depth of 0~50m and 50~200m were conducted at KODOS (Korea Deep Ocean Study) area before and after sunrise. Zooplankton abundance was slightly higher after sunrise than before sunrise in the surface layer. Chlorophyll-a concentrations were relatively low as the concentration of sediment increased in most experiments possibly due to a decrease of grazing pressure of microzooplantkon such as ciliates, which is the efficient grazer on small-sized phytoplankton. Because copepod predation on microzooplankton may be prevented by the high concentration of sediment, resulting in lower grazing pressure on small-sized phytoplankton. The results obtained during the baseline study as a part of KODOS project since 1998.

Jan 1, 2001

By Mark D. Hannington

Seafloor polymetallic sulfides have been found in diverse volcanic and tectonic settings on the ocean floor at water depths ranging from 3700 meters to <1500 meters. More than 100 occurrences of hydrothermal mineralization have been documented (including Fe-oxide deposits, Mn-crusts, metalliferous sediments, and massive sulfides), but high-temperature hydrothermal activity and large accumulations of polymetallic sulfides are known at fewer than 20 different sites. Chemical analyses of samples from these deposits indicate that they contain important concentrations of Cu, Zn, Ag, and Au, comparable to those of massive sulfide deposits on land. However, the lack of sufficient data concerning the distribution, size, and bulk composition of seafloor deposits precludes a meaningful assessment of their resource potential.

Jan 1, 1994

By Mark Vardy, Kate Dobson, Isobel Yeo, Paul Lusty, Bramley Murton

In response to anthropogenic climate change, the way in which we use and generate energy is changing. To facilitate these developments, it is essential that we increase and diversify the supply of ‘E-Tech’ elements essential for cleaner energy generation and more efficient usage. The vast majority of these materials (e.g. cobalt, lithium, niobium, platinum group metals, rare earth elements and indium) come almost exclusively from mining and new resources must be found and developed in order to secure supply and meet the demands of the future. Ferromanganese (FeMn) crusts are rich in cobalt, tellurium and rare earth metals, and are common on seafloor hard grounds at water depths over 1000 m. The mining of both FeMn crusts and nodules is potentially viable dependent of the balance of cobalt and nickle prices (Martino & Parson, 2012), however, crusts need to be at least 4 cm thick with cobalt contents of at least 0.8% (International Seabed Authority, 2008). The difficulty for those wishing to exploit these resources is firstly finding them, and secondly assessing their potential remotely. Such capability would not only save time and money, but also allow mining operations to be more focused, reducing needless destruction of seafloor habitats from exploratory mining or mining of noneconomically worthwhile deposits. In this contribution, we examine the distribution of crusts on a single Atlantic Gyot (Tropic Seamount), the morphology of FeMn crusts, their variable growth patterns and the characteristic geophysical response from crusts in various datasets, including ship based 60 m resolution multibeam and high resolution bathymetry, backscatter and sub-bottom profiler data acquired using an Autonomous Underwater Vehicle (AUV).

Jan 1, 2017

By Hans Smit

The face of mining as we know is changing as mining companies all over the globe realize the reality of accessing the vast mineral wealth contained on, and under, our ocean floors. With some land based mineral deposits being fully exploited across the world, deep sea mining is set to revolutionize global approaches to the search for precious metals and other sought after minerals. Previously, the financial and technological implications of deep sea mining outweighed the benefits of access to the mineral rich deposits identified all around the world. The process of marine diamond mining off the west coast of southern Africa started in the late 1950s, and subsequently continued by De Beers to the present day, has proven to be an excellent proving ground for the development of technology and mining systems that ensure a sustainable and financially viable business.

Jan 1, 2011

By Irina Melekestseva

The Cu-Zn massive sulfides from the basalt-hosted Semenov-2 hydrothermal field (13°31.13´ N, 44°59.03´ W, MAR) are enriched in Au (22?188 ppm) and Ag (127?1787 ppm) [Ivanov et al., 2008] and elevated contents (ppm) of Se (269?289), Sn (123?125), and Sb (72?75). These may indicate heterogeneous substrate rocks and possible ultramafic rocks. Based on phase analysis, 70% of the gold in the massive sulfides is free. LA-ICPMS analysis has shown that the main carrier of the invisible gold is covellite (22.51? 226.64 ppm). Covellite is also characterized by elevated contents of Se, Mo, Sn, Te, Au, Bi, As, Ag, Sb, Tl, and Pb relative to the primary sulfides.

Sep 14, 2011

By Karsten Hagenah, Tor Jensen, Jens Laugesen, Øyvind Fjukmoen, Lucy Brooks

This paper discusses operational environmental threshold levels for exploitation of mineral resources in the deep sea. Such criteria are needed to be able to monitor and control deep sea mining with respect to the stringent environmental requirements that are needed. It is recommended to use existing environmental threshold levels for comparable underwater activities. Fields of application are mainly but not exclusively seabed mining operation activities under the governance of the International Seabed Authority (ISA). The threshold levels and limits mentioned in this paper are proposed recommendations based on other activities than seabed mining but are a proven and accepted approach in other maritime industry activities. An example of such other activities with proven and accepted environmental threshold levels are Oil & Gas exploitation activities in the sea. Background The first exploitation of mineral resources in international waters is coming closer. Presently regulations for exploitation for mineral resources in the Area are being developed by the International Seabed Authority (ISA). The ISA regulations will contain the framework related to environmental monitoring of exploitation. However, the regulations will not contain operational environmental threshold levels for the Contractor.

Jan 1, 2018

By Daniel E. Walsh

The recovery of most minerals, which are amenable to gravity concentration, is standardly determined by accurate sampling and assaying. .With respect to particulate - gold ores, sampling and assaying are still the convention, but the accuracy and reproducibility of these operations are much discussed and debated points. Evaluation of gravity concentrators by conventional sampling and assaying techniques is very time consuming, costly and may introduce a large amount of uncertainty into the results due to the particulate nature of placer gold. These problems are not unique to placer gold ores and apply to any low grade ore with particulate values. A gravity concentrator evaluation process developed by MIRL employs the use of neutron activated gold (198Au) and radiation detection circuits which monitor the concentrator&apos;s product pulp streams. Concentrator recovery is determined from the ratio of the number of gold particles detected as passing into the concentrate to the total number of gold particles detected over all monitored pulp streams. This system eliminates the experimental errors introduced by sampling, sample reduction, and assaying and allows recovery to be evaluated for gold particles of specific sizes, shapes, and flatness. This system enjoys its greatest utility where a large number of tests are to be run in order to evaluate a concentrator over a variety of operational settings, i.e. factorial designs, and allows accurate testing of concentrators operated in closed circuit systems. Beginning in 1984, MIRL conducted radiotracer studies of unit processes, which included jigging, static wedge wire screening, elutriation, and concentration with compound water cyclones.

Jan 1, 1989

By Karsten Hagenah, Tor Jensen, Jens Laugesen, Øyvind Fjukmoen, Lucy Brooks

This paper describes operational environmental threshold levels for exploitation of mineral resources in the deep sea. Such criteria are needed to be able to monitor and control deep sea mining with respect to the stringent environmental requirements that are needed. It is recommended to use existing environmental threshold levels for comparable activities where such are existing. Fields of application are mainly but not exclusively seabed mining operation activities under the governance of the International Seabed Authority (ISA). The threshold levels and limits mentioned in this paper are proposed recommendations based on other activities than seabed mining but are a proven and accepted approach in other maritime industry activities. An example of such other activities with proven and accepted environmental threshold levels are Oil & Gas exploitation activities in the sea. Background The first exploitation of mineral resources is coming closer. At the moment regulations for exploitation for mineral resources in the Area are being developed by the International Seabed Authority (ISA). The ISA regulations will contain the framework related to environmental monitoring of exploitation. However, the regulations will not contain operational environmental threshold levels for the Contractor.

Jan 1, 2018

By Jun Lu

Compared with land mineral resources investigation, as well known, it is more important for marine geologists to get image data (e.g. photographs, video tapes and various charts) because they are often hard to reach deep seabed directly. In the past years a plenty of image data which are in various forms have been accumulated. In contrast with both digital and character data managing the image data by using database is just unfolding and it will be a trend for marine mineral resources investigation. GIS (Geography Information System) offers another useful means of processing image data, especially geological data. GIS is characterized by processing vector data (e.g. point, line and polygon), but newer versions of GIS software package are also able to process raster data (e.g. photographs etc.). The present author made a presentation on marine mineral image database during 25th UMI, but that system runs under DOS environment and dealt with only mineralogy. Recently a new system which integrates Oracle image database with GIS (ArcView version 3.1) has been developed. This system runs under Windows NT environment. In the network environment Server/Client mode is adopted, and over 200 basic subdatabases (tables)are located on Server; operating interfaces are located on several clients so that several persons can operate the system simultaneously. The whole system involves five types of marine mineral resources: manganese nodules, cobalt-rich crusts, polymetallic sulfides, phosphorites and gas hydrates. The data of every type of marine mineral resources described above are distributed among five units and several blocks. The units and blocks are described below:

Jan 1, 2000

By Alexander Malahoff

The study of why and how life survives in the Extreme environment is a major frontier of science today. Extremophiles are organisms that require extreme environment including high temperature, pH, pressure and salt concentration, or low temperature, pH, nutrient concentration, or water availability. Their common habitats are geothermal vents, pools, lakes and craters of active volcanic regions, such as those of New Zealand, Japan, Kamchatka, Yellowstone USA or the hydrothermal vents of the ocean ridges and submarine volcanoes. These settings are accessible by foot, boat, helicopter, or submersibles. This presentation examines the geology, chemistry of geothermal sites of New Zealand, including the active volcano, White Island, Yellowstone, the submarine volcano Loihi in Hawaii, and sections of the mid-ocean ridges. Designing process and construction of Extremophilic sampling and bioreactor systems used in the study of Extremophiles will be discussed. The driving force behind the research of extremophiles is not only the fundamental science, but also biotechnological potential associated with these microorganisms and their cellular products. The University of Hawaii?s Marine Bioproducts and Engineering Center (MarBEC) is laying the foundations for such new industries.

Jan 1, 2001

By Mikhail D. Ageev

The paper concerns with some questions of Autonomous Underwater Vehicle (AUV) control system design, which allows a motion at rough undersea terrain. The AUV advantages reveal itself completely during exploration of such objects as seamounts and reefs area. These objects are characterized by steep slopes (30 degrees and above) and chaotic situated obstacles (rock debris, pinnacles, escarpments). Uses of other technical facilities for operating in such formations are difficult, dangerous or impossible. These regions take an interest due to the presence of iron-manganese crusts. Modern AUV can estimate density of mineral by means of still camera or video recorder. For this reason the vehicle has to move with the distance of 3-5 meters from seabed. Under such conditions micro- and mesorelief presents a considerable danger for AUV. The AUV can bypass underwater obstacles in the various ways. However, in any case AUV motion will be characterized by intensive maneuvering on various speed (from 0 up to 1.5 m/s), circular change of tractive force vector and, hence, a circular flow about the hull. So, AUV is equipped with the propulsion system, which provides free modes of motion. AUV control system (CS) has tri-level structure to allow a motion in a rugged seabed terrain. According to the generally accepted categorizations, CS includes execution, coordination and strategic levels. The strategic level contains the goals of AUV mission. Obstacles avoiding and route choice are realized by means of simultaneous maneuver in vertical and horizontal planes. Sonar system is used for data acquisition about obstacles. It consists of a few echo-sounders with fixed directivity pattern. The route choice algorithm operates at two lower levels of CS. Basic (?reflex?) functions of spatial motion are realized within the execution level and considered in the paper. The choice of motion modes is carried out at the coordination level of system. All accessible navigating information (the data from flight sensors and from multichannel echo-sounder systems) is used for this purpose. In addition the bypass of characteristic types of obstacles is carried out with the help of basic motion modes combination. The modeling results of bypass of various typical obstacles, and also their combinations are described in the paper.

Jan 1, 2011

By Nii Allotey Odunton

One of the primary responsibilities of the International Seabed Authority?s Secretariat (the Secretariat) is to assess the quantities of metals present in seabed polymetallic nodules in the International Seabed Area under the Authority?s jurisdiction. To carry out this responsibility, the Secretariat periodically undertakes an assessment of the reserved areas in the Clarion-Clipperton region of the northeastern Pacific (CCZ) using the data submitted by the registered Contractors and maintained in the Authority?s POLYDAT database. The results of its most recent assessment demonstrated that the information submitted by the Contractors, though satisfactory for some purposes, does not permit the in situ quantities of metals in these areas to be estimated with a degree of confidence that is comparable to many land-based mineral resource estimates. Our strategy is to divide the work into two distinct but closely related efforts; one to draft a Prospector?s Guide that provides a narrative description of the key geological and oceanographic data that may be related to deposit abundance and metal content, and another that we call the Geological Model, that summarizes and documents the quantitative resource assessments accomplished in the project.

Jan 1, 2005

By Timothy F. McConachy

Magmatic-hydrothermal activity in the South-West Pacific and SE Asian island arcs during the Tertiary has created a premier copper-gold province with numerous, commercially attractive base and precious metal deposits. This activity continues to the present day, especially in submarine sectors of those arcs where modern technologies enable direct observation of ore-forming processes in action. Until recently, however, the volcanic island arcs of Indonesia escaped such attention. The Indonesia-Australia Survey for Submarine Hydrothermal Activity (IASSHA), involved three cruises with KR Baruna Jaya VIII, focused particularly on the Sangihe arc; Tomini Bay, Sulawesi, including the vicinity of isolated Colo volcano; and the Sunda Strait including the neighborhood of Krakatau volcano. IASSHA 2001 and 2003 cruises studied the arc and behind-arc sectors of the Sangihe volcanic island chain extending northwards from Quaternary volcanoes on the northeastern tip of Sulawesi, near Manado, to the Kawio Islands near the border with the Philippines (Fig. 1). This chain lies above a west-dipping Wadati-Benioff seismic zone whose subduction trench is obscured by accreted sediments and mélange, forming the Talaud-Mayu ridge. West of the main active chain and extending northwards from Manado there is a subparallel ridge (The Manado Line) surmounted by a number of high (>2000 m) seamounts of uncertain age.

Jan 1, 2005

By J. Bruce Gemmell

ODP Leg 158 drilled seventeen holes into the active TAG hydrothermal mound and underlying stockwork, 26°N, Mid-Atlantic Ridge. Drilling in five different areas, including a high-temperature black smoker complex and a lower-temperature white smoker vent field, revealed the multi-stage depositional history and character of sub-seafloor mineralization and alteration. The upper portion of the mound consist of massive pyrite and pyrite breccias which are underlain by pyrite-anhydrite breccias and then by quartz-pyrite breccias. Quartz-pyrite breccias grade down into silicified wallrock breccias. Chloritised basalt breccias occur at depths greater than 100 m. Several stages of quartz-pyrite±chalcopyrite veins occur in the stockwork zone and lower portions of the mound, whereas anhydrite±pyrite±chalcopyrite veins occur within the upper parts of the mound. Recovery of unaltered basalt near the edges of the mound has constrained the extent of the stockwork zone to a pipe-like feature 80 meters in diameter. A detailed sulfur isotope investigation of sulfides and sulfates within mound and the underlying stockwork zone has revealed the overall range of sulfide d34S analyses to be 0.35% to 10.27%. Anhydrite has a tight range of d34S values 20.55% to 21.56%. There are distinct differences in d34S values between the different textural types of pyrite (massive sulfide, breccia clasts, disseminations associated with alteration, and veins). The massive sulfide and breccia clasts have a similar distribution of d34S values (6%-8%), however the d34S values of the disseminated pyrite associated with the alteration are distinctly heavier (8%-10%). Vein sulfides have the lightest d34S values (5%-7%). Sulphur-isotope values at TAG are, in general, the heaviest reported for unsedimented mid-ocean ridge deposits.

Jan 1, 1998

By Jung-Hoon Kang

Present study was stemmed from the survey associated with deep-sea mining in the KODOS area between Clarion Fracture Zone and Clipperton Fracture Zone located in the North Pacific Ocean. The study area, which is located in the southeastern part of North Pacific gyre, is oligotrophic waters with low nutrients and chl-a concentrations below 1µg/l (MOMAF, 1996). This area is also characterized by divergence at 8°N and convergence at 6°N, which moved northward or southward in the range of a few kilometers with seasonal and climate changes. If the waste materials related to deep-sea mining are intruded into the surface waters continuously, unexpected effects to water column ecosystem are anticipated negatively. In order to assess the impact on the planktonic ecosystem, natural variation need to be distinguished from anthropogenically induced variation in terms of the abundance and species composition of plankton. In this study, mesoscale variation of zooplankton community was reported in relation to the physical conditions in the northeastern Pacific during 1998 and 1999. Temperature and salinity were determined using a CTD from surface to 200m depth in July 3-20, 1998 and in June 22-July 1, 1999. Zooplankton samples were collected from two different depths (0-50m, 50-200m) by vertical towing using an opening-closing net (100cm diameter and 300 µm mesh size). The samplings were carried out at every one degree between 5° and 12°N (1998), between 5° and 11°N (1999) along the meridional lines of 131°30´ W. The net was lowered to the depth of interest from a stationary research vessel and towed upward to collect zooplankton at a speed of 25~30 m per minute. Zooplankton samples were transferred to 1-l sampling bottles and immediately fixed with neutralized formalin into the final concentration of 5%. Considering the characteristics of zooplankton such as diurnal vertical migration, all samplings were done during the nighttime. The volume filtered by the net was calculated from the readings of flow meter (Hydro-Bios Model 438-115). Zooplankton were identified to the genus level and enumerated under a microscope. The abundance of zooplankton at each station was expressed as the numbers/100 m3.

Jan 1, 2003

By Ian J. Graham

Brothers volcano, in the southern Kermadec Arc, is host to two hydrothermal vent fields with very different geology, permeability, vent fluid compositions and mineralogy (see de Ronde et al. and Ditchburn et al. this volume). The NW caldera site contains mineral deposits (sulfide chimneys and crusts), which are either Cu-rich (?magmatic?) or, more commonly, Zn-rich (?epithermal?). The lower cone site, in contrast, is characterized by native sulfur mounds and spires. It has been proposed (see de Ronde et al. this volume) that the metals, especially Cu and possibly also Au, enter the hydrothermal system via injection and degassing of magma and/or the dissolution of metal-rich glasses. They are then transported rapidly upwards via magmatic volatiles along long (c. 2.5 km), narrow (c. 300 m diameter) pipes, consistent with evidence of vent fluids forming at higher than hydrostatic pressures, at relatively shallow depths. The NW caldera and cone sites may represent stages along a continuum between magmatic-hydrothermal and water/rock-dominated end-members. In this context, investigation of melt inclusions in conjunction with other geochemical and petrological research was carried out to ascertain the metal transporting conditions that may have led to mineral deposition and ore formation. Sixteen melt inclusions in plagioclase were analyzed for their chemical compositions from a typical cone dacite sample using LA-ICPMS at the University of Tasmania. The inclusions are typically glassy and commonly occur with other inclusions such as apatite, clinopyroxene, zircon, magnetite, sulfides and/or low-density fluids (Fig. 1). Major (XRF) and trace element (ICPMS) analyses were performed on whole rock samples collected during the 2005 Shinkai 6500 expedition. Haase et al., (2006) has also reported EPMA glass analyses from cone dacites, which may be used for comparison (Table 1). [ ]

Jan 1, 2010