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By Daisuke Monoe, Kisaburo Nakata, Rika Takeuchi, Tetsuo Yamazaki, Tomoaki Oomi, Tomohiko Fukushima

There are generally two methane passes in conjunction with the seafloor natural cold seepages, as is schematically shown in Fig. 1. The first pass consists of the coupled anaerobic oxidation of methane and anaerobic sulfate reduction, as well as sulfur oxidation in the bacterial mats and immobilization thereafter in the sediment layer and on the seafloor. Through the first pass, calcium and organic carbonates are formed in biological and chemical processes from the methane (Luff and Wallmann, 2003; Luff et al., 2004). The detailed structure of the seafloor methane consumption process unit and its biological and chemical processes were introduced in Yamazaki et al. (2005). The other pass consists of direct bubbling into the water column. Through this pass, organic carbonate is formed with biological oxidation, and a small amount of the methane escapes into the atmosphere. Methane flux is supplied to these two passes through the sediment layer from the deeper structures. The structure of the methane supply process unit was introduced in Yamazaki et al. (2006).

Sep 24, 2006

By Irina A. Pulyaeva

Hydrogenetic 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. Detailed study of several seamounts has given confidence about the scale of Fe-Mn crust development and their characteristics. Now, commercial interests gain more and more attention. However, at the same time some theoretical questions related to Fe-Mn crust history including controls on metal sources and concentrations have not yet been answered. Here, we present the overview of age, composition, distribution, and geological setting of hydrogenetic Fe-Mn crusts from Pacific and Atlantic seamounts and discuss the geological evolution and conditions that led to the formation of potentially economic concentrations of metals. The age, composition, and distribution of Fe-Mn crusts in the Atlantic and Pacific oceans were determined by using a Fe-Mn deposits database compiled from our original data, published papers, published databases, and other international sources. Comparative analysis of Fe-Mn deposits from the Atlantic and Pacific oceans shows that there are similarities in basic characteristics of crust formation in both oceans. Simultaneously, there are significant differences in the scale of Fe-Mn crust distribution and composition that can be explained by differences in geological settings and characteristics of the deposition environment.

Jan 1, 2011

By Ian Selby

Resource management is a key factor in the operation of a successful marine aggregates business; it is integral to the development of sustainability, satisfying increasing commercial, quality, and environmental performance standards. Resource management is based on the combination of; (i) a thorough evaluation and understanding of the resources on the sea bed and (ii) a dredging plan targeted to permit the effective and efficient extraction of the resources whilst mitigating impacts and leaving the sea bed ready for recolonisation.

Jan 1, 2004

By Chris Roper

The Gavia Autonomous Underwater Vehicle is a two-man portable AUV that is capable of performing seafloor surveys in water depths to 2000 meters. The standard survey sensor suite includes a dual frequency side scan sonar and high resolution digital camera. Additional survey sensors are currently being incorporated into the Gavia AUV, include Sub Bottom sonar, Swath Bathymetry sonar and Multi Beam sonar. The modular design of the Gavia AUV allows the end user to quickly incorporate new sensors including client developed propriety sensors.

Jan 1, 2005

By V. Soloviev

The world?s data available on near sea-bottom gas-hydrate accumulation and deep-water fluid-discharge areas are presented in this paper. Gas-hydrate accumulation associated with fluid discharge (mud volcanoes, gas seeps, gas-saturated water seeps) is characterized by the following. First, the largest hydrate accumulations in sediments are located at shallow subbottom depths and have well-defined limits, especially in the upper subbottom part. Second, gas-hydrate formation in fluid-discharge areas is a present-day process, with the global occurrence of deep-water fluid-discharge areas numbering up to about ten thousand, and with all the seep areas being favorable for the formation of near-sea-bottom gas-hydrate accumulation. Third and principal, gas resources in the hydrates can be considered as renewable. Estimates of possible gas volume in single accumulations of hydrates and the global budget, as well as possible methods of gas utilization from such gas-hydrate accumulations are discussed in the paper.

Jan 1, 2005

By P. E. Mikhailk

From July 29 to September 15, 2004, the 178th cruise of the R/V Sonne took place under the KOMEX program in the Sea of Okhotsk. One of the cruise objectives was to dredge two different kinds of seamounts: 1 ? underwater volcanoes from the north slope of the Kurile Basin; 2 ? a seamount formed by tectonic (non volcanic) processes from the Kashevarov Trough. The underwater volcanoes are young edifices (0.84 ± 06 Ma, Baranov et al., 2002) with heights ranging from 150 to 300 m. Tops of the volcanoes are located at depth of 1260 to 2340 meters. The volcanic edifices are formed by olivine-clinopyroxene-plagioclase basalts. Dredge samples are covered by Fe-Mn crusts up to 40 mm thick. The seamount from the Kashevarov Trough is a tilted block. The height of the seamount is about 400 m and its top is located at a depth of 960 meters. Biotite hornfels, conglomerates, granodiorites, dropstones, and Fe-Mn crusts were recovered there. The thicknesses of crusts are up to 150 mm. Fe-Mn crusts from the underwater volcanoes differ from Fe-Mn crusts from the Kasevarov Trough seamount in morphology as well as in mineralogical and chemical compositions. The research was supported by the Program of the Presidium of the Far East Branch of the Russian Academy of Sciences (project ? 05-III-G-08-086).

Jan 1, 2005

By Andrew Bellamy

A thorough appreciation of the origin, formation, preservation and geometry of marine sand and gravel deposits is central in demonstrating that their extraction by dredging does not affect coastal processes or marine life. Geological evaluation underpins wave, tidal and sediment transport modeling and assists in predicting the nature and extent of seabed change during and after dredging. Marine sand and gravel deposits in the English Channel, southern North Sea and parts of the Irish Sea are of predominantly periglacial fluvial origin and record long histories of valley and floodplain cut and fill associated with Quaternary climatic and sea level oscillations. In the Bristol Channel, the influence of marine transgression and tidal dominance in sorting proglacial outwash deposits is evident in the distribution of sandbanks, scoured channels and gravel lags of this region. These deposits are relict and are unrelated to coastal sediment dynamics. Their extraction leaves seabed depressions which monitoring shows remain unfilled. The resultant offshore bathymetric changes and sediment removal in over 10 m water depth are not transmitted to the coastal zone as beach drawdown, wave height increases or sediment starvation. Applications for new aggregate dredging permissions in UK waters must be accompanied by an EIA and need to make a convincing case that the dredging will not affect rare or declining species and communities of marine life. Seabed recovery rates post dredging are now investigated and understood with reference to geological setting and the uniqueness of the sediment/biological character (biotope). Investigation of the continental shelf by the Industry and others reveals the large extent of gravel-dominated biotopes relative to commercially viable deposits.

Jan 1, 2004

By Akira Usui

Iron and manganese are very mobile metallic elements in the surface aqueous environment, particularly in the oceans. The elements are easily precipitated as oxides or dissolved back into water, controlled mainly by redox conditions, and the oxide precipitates often selectively accumulate other metallic elements. We have found clear evidence of fine-scale variations in chemistry, mineralogy, isotope composition and microstructures within various iron-manganese nodules and crusts, such as in the deep-sea basins and seamounts of the Pacific Ocean, and in shallow waters in the Baltic Sea. The patterns of variation with depth (that is time-lapse profiles of the deposits) are often correlated among samples and sometimes between remote localities. These fine-scale variations most probably reflect past depositional conditions and possibly image the environmental change, although they remain to be correlated to any physicochemical, geological, or oceanographic parameters. The hydrogenetic ferromanganese crusts have grown widely in the northwestern Pacific, accelerated by intensive circulation of oxygenated bottom waters during the last several millions of years, or earlier. The fine-scale (in millimeter) in-depth compositional and textural patterns with Be-10 growth-rate curves suggest significant changes in growth rate and also occasionally show a common microstratigraphic pattern among samples. Some of the samples indicate a correlation in growth pattern between remote locations, while others suggest short-range difference of oceanographic conditions with water depths.

Jan 1, 2004

By Cheong-Kee Park

Paleomagnetic properties of sediment cores were examined to reconstruct paleodepositional conditions in the Korea Deep Ocean Study (KODOS) manganese nodule area, located in the northeastern equatorial Pacific. The KODOS sediments studied have a stable remanent magnetization with both normal and reversed polarities, which are well correlated with the geomagnetic polarity timescale for the late Pliocene and Pleistocene. Average sedimentation rates were 1.56 and 0.88 mm/kiloyear for the Pleistocene and late Pliocene, respectively. Clay mineralogy and scanning electron microscope analyses of the sediments indicate that terrestrial material was transported to the deep-sea floor during these times. The variations of sedimentation rates with age may be explained by the onset of the northern hemisphere glaciation and subsequent climatic deterioration during the Pliocene and Pleistocene. For the Pleistocene, an increasing sedimentation rate implies that input of terrestrial materials was high, and also a high input of biogenic materials was detected as a result of increased primary production in the surface water. The down-core variations in paleomagnetic and rock-magnetic properties of the KODOS sediments were affected by dissolution processes in an oxic depositional regime. As shown by magnetic intensity and hysteresis parameters, the high natural remanent magnetization (NRM) stability in the upper, yellowish brown layers indicates that the magnetic carrier was in pseudo-single domain states. In the lower, dark brown sediments, only coarse magnetic grains survived dissolution and the NRM was carried by more abundant, multi-domain grains of low magnetic stability. The down-core variation of magnetic properties suggests that the KODOS sediments were subjected to dissolution processes resulting in a loss of the more stable components of the magnetic fraction with increasing core depth.

Jan 1, 2004

By Kiseong Hyeong

The Intertropical Convergence Zone (ITCZ), where the southeast and northeast trade winds converge, is the effective climatological barrier that separates the southern and northern hemispheres in terms of dust budget. Asian and N. American dusts dominate in the Pacific north of the ITCZ, while Central and S. American dust prevails south of the ITCZ. In order to understand the nature of latitudinal and depth-related variations of mineral composition in terms of position relative to the ITCZ, deep-sea core sediments were collected from 9°N to 17°N at a 2° intervals along the 131.5°W meridian and analyzed for mineral composition. The amount of illite in surface sediments decreases gradually from 65% at 17°N to 31% at 9°N. In contrast, smectite increases from 11% to 56% southward. The observed mineralogical variation toward the ITCZ is attributed to the increased supply of volcaniclastic material transported via the southeast trade winds from the Central and South America source regions. Smectite-illite transition, a phenomenon that the amount of smectite increases over illite, occurs at around 10°N, the northern margin of the ITCZ. This result indicates that the change in latitudinal position of the ITCZ in the geological past could be recorded by the smectite-illite transition in deep-sea cores. The cores studied show down-core variation of mineral composition from illite-rich at the surface to a smectite-rich clay suit at depths, similar to the latitudinal variation. The smectite-illite transitions observed in these cores are likely the records of changes in latitudinal position of the ITCZ. The depth and age of the smectite-illite transition is getting shallower and younger towards the equator, implying that the ITCZ was located farther north during late Tertiary and has shifted southward to the present position of 5°N~10°N.

Jan 1, 2004

By P. Mikhailik

Recently, characterized by fast development high- and nano-technology, demand for rare and trace metals has increased. One of such metals is gallium. Gallium compounds, mainly GaAs, are used in medicine, to manufacture optoelectronic devices, microwave techniques, devices of solar power and infrared optics, etc. The basic gallium industrial deposits are known only on land. There are bauxites (50 ppm), nepheline rocks and ores (36-38 ppm, minerals concentrators are nepheline and sodalite), Zn-Pb-Cu ores (5000-12000 ppm, minerals concentrators are gallite, germanite, sphalerite, bornite), sulphide-polymetallic and Pb-Zn ores (10-32 ppm, minerals concentrators sphalerite, chalcopyrite) (Vershkovskya et al., 1998). High concentration of gallium are observed in hydrothermal massive sulphides of a Mid-Okinawa Trough (The South Chinese Sea) and Sujo seamount (The Philippine Sea) (Noguchi et al., 2007). As it is known, deep-sea massive sulphides and associated Fe-Mn crusts are products of hydrothermal fluid discharge. High-temperature massive sulphides precipitation are the first, and low-temperature Fe-Mn crusts deposition is the last process of hydrothermal mineralization (Cronan, 1982). Hydrogenic crusts and nodules of the World ocean are characterized by low concentration of Ga, close to clarke (19 ppm) (Kobaltbogatye.., 2002). Hydrogenic crusts from the Sea of Okhotsk are exception, because Ga concentrations are exceeded clarke in 3,5 times (Mikhailik, et al., 2009). Complex studying of Fe-Mn crusts from deep-sea basins volcanic seamounts of the Sea of Japan has shown their hydrothermal-sedimentary genesis (Mikhailik, 2009). High gallium concentration (up to 850 ppm) was established in these crusts by ICP-MS (Agilent 7500C). Microprobe research (JXA-8100) of samples Fe-Mn crusts has not revealed the gallium minerals concentrators. It suggests that, gallium in Fe-Mn crusts of the Sea of Japan is sorb substance.

Jan 1, 2010

By Mikhail P. Torokhov

Typical coastal placers leave no doubt that placer accumulation can result in significant concentration of heavy minerals in marine shallow water environment. However, the same situation is quite predictable for guyot?s slopes at stages of submarine volcano formation and later submersion of guyots to a depth of up to 3-4 km. Where these placers could be found is also clear ? in coastal facies (as typical coastal placers), and in morphological traps down guyot slopes in zones of active submarine currents. The latter could be cracks in rocks, shallow depressions, spurs, and structures, such as coral reefs, stromatholiths, and even ferromanganese crusts. The last of these have been studied carefully by the author in the Magellan Seamounts and on the Mid-Pacific Rise: tens of minerals, including mineral forms of PGE, REE, Mo, W, Te, Cr, Co, Ni, Cu, &Zn were identified as a xenogenic (trash) minerals. The detailed study of polished epoxydized sections, showed that interstitial spaces of Fe-Mn botryoids are enriched in heavy minerals (predominantly titanomagnetite). Taking into account the irregular character of crust surfaces and their position in active water environment, we can definitely state that they are the ideal traps for placer minerals. Study of guyot basaltic matter showed the presence of similar REE, PGE minerals that are in the crusts, and the same (mostly) micron sizes of minerals. High content of PGE in some basaltic varieties (up to 1 ppm) suggests that this is a reasonable source of these elements in the crusts, rather than the water column (which is normally considered to be the case by most marine scientists). Predominance of Pt in hydrogenous (?) crusts is interpreted as due to the better stability of Pt mineral forms during weathering and transportation (these are isoferroplatinum, and silicides). Comparison of 143Nd/144Nd values in bulk crusts, heavy fraction of crusts, basalts, and water column supports the author?s idea, that a significant part of REE also comes from basaltic matter (in form of monazite, CeO2 etc.).

Jan 1, 2004

By Nobuyuki Okamoto

The present three-year long phase of the SOPAC/Japan Deep Sea Co-operative Mineral Resources Programme [Programme], commenced in 2000. The Programme has been funded by the Government of Japan through the Japan International Co-operation Agency (JICA) and the Metal Mining Agency of Japan (MMAJ), since 1985. Field survey activities and associated data analysis and interpretation, for the Programme, has largely been carried out by the Deep Ocean Resources Development Co., Ltd. (DORD). The Government of Japan has, since 1982, recognised DORD as one of its ? Pioneer Investigators? for manganese nodules in the Clarion Clipperton Fracture Zone . Although the objective of this paper is to present the results of the drilling cruise that was conducted from December 2001 to January 2002, within the North Fiji Basin, in Fiji?s EEZ, it will also seek to provide a broad overview of the results of the cruise conducted within the Cook Islands in May to June 2000, as well as present preliminary results of the cruise conducted in the Marshall Islands in June to July 2002.

Jan 1, 2002

By Seung-Kyu Son

This study was investigated about physico-chemical parameter such as water temperature, salinity, inorganic nutrients and total organic carbon (TOC). CTD (Model: Sea-Bird 911 Plus) castings were carried out on two transects in the northeast equatorial Pacific Ocean. As a part of the Korea Deep-sea Environment Study (KODES), inorganic nutrients and TOC were determined at 41 stations located from 131° to 136°W along 10.5°N and from 17° to 5°N along 131.5°W (Fig. 1). We particularly chose KODES Long-term Monitoring Station (St. KOMO) to observe for the annually environmental baseline study in the contract area. [ ]

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 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 Jan M. Peter

Many of the Pb-Zn massive sulfide deposits of the Bathurst area in northern New Brunswick, Canada, are intimately associated with laterally continuous iron formation (IF) (Figure 1). This IF is a fossil laminated, exhalative, chemical sediment. Together, the IF and the Brunswick #12, Brunswick #6, and Austin Brook deposits (rightmost discontinuous horizon on Figure 1) are collectively referred to as the "Brunswick Belt". To date we have only studied the Brunswick Belt and have not examined the horizon along which the QSR, CNE and Flat Landing Brook deposits lie. The Bathurst area is underlain by the Tetagouche Group (Figure 2), a Cambro(?)-Ordovician sequence of metasedimentary and bimodal metavolcanic rocks that was intruded by mafic to felsic plutons and subsequently deformed during the Taconic Orogeny. The stratigraphic sequence consists of shales and greywackes that are overlain by carbonaceous shales and felsic volcanic and volcaniclastic rocks; these are in turn overlain by mafic volcanic and sedimentary rocks. The massive sulfide deposits and IF occur within the upper portions of the felsic volcanic rocks in close association with carbnaceous metasedimentary footwall rocks (Figure 2).

Jan 1, 1993

By Thomas Kuhn

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

Jan 1, 2010

By Satya Nandan

• A review of the structure and mandate of the Authority – its main functions. • The different types of mineral resources found in the deep seabed – their global distribution. • The Development of Regulations for Prospecting and Exploration of Polymetallic Nodules, Cobalt-Rich Crusts and Polymetallic Sulphides including environmental regulations and guidelines. • Early constraints for deep seabed mining – Improving conditions for mining – Future prospects for mining.

By Takashi Ito

Numerous studies have examined the distribution of deep-sea manganese deposits throughout geologic history. Here I summarize the recent results, focusing on the frequency of occurrence, burial age and mechanism, and the paleoceanographic implications.