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The chemical composition of the nodules varies with the type of manganese minerals and the size and characteristics of their nucleus but those who have an economic interest have nucleus, generally : Mn> Fe> 6> Si> Al> Ba> Ni> Cu > Co. The Pacific Rim is an area of abundant occurrence of polymetallic nodules and the Pacific sea floor of the Clarion-Clipperton Zone (CCZ) is one of the most interesting areas in regard to the genesis of polymetallic nodules. Their abundance in the ocean floor is very variable, as there are places where they cover more than 70% of the ocean floor. The nodules can be found at any depth, but the highest concentrations are between 4000 and 6000. Hydrothermal processes that occurs near the East Pacific Rise at 21° N, may inputs metallic elements to nodules and to pelagic sediments, especially in regions close to the dorsal, as a greater influence hydrogenetic processes are present westward Metals such as Cu, Co, Ni, Sn, Fe, Mg, Pb, Zn and Ba show a relationship with the East Pacific hydrothermal activity and sea currents carry these metals in solution to the Clarion-Clipperton fracture area, where there are hydrogenic metals sources (Al, Fe and Mn).

Sep 14, 2011

By James R. Hein

Low- to intermediate-temperature, diffuse-flow hydrothermal fields and associated mineral precipitates have been found at many locations along oceanic spreading centers, back-arc basin spreading axes, and midplate hot-spots. However, this type of hydrothermal field has not been found in oceanic fracture zones until recently. We mapped and collected samples from an active hydrothermal field in the Blanco Fracture Zone (BFZ) located in the northeast Pacific. The BFZ connects the Gorda and Juan de Fuca spreading centers and is divided into east and west segments by Cascadia Depression, a small spreading center. Small pull-apart basins occur along both the east and west segments. A complex set of basins near the western end of the BFZ includes from east to west, Surveyor Depression, East Blanco Depression (EBD), and West Blanco Depression. The hydrothermal field described here is located in the EBD.

Jan 1, 2001

By Jonguk Kim

Submarine hydrothermal activity and mineralization related to island arc volcanism along the Tonga arc were explored during two research cruises in October 2009 (KODOS 09H) and February 2010 (KODOS 10H), respectively. In KODOS 09H cruise, geophysical survey, including multi-beam bathymetry, marine seismic and magnetic investigations, was performed on 10 volcanoes to find out possible structural discontinuity that can act as fluid pathway for formation of hydrothermal deposits at submarine caldera system. The result provided acoustic and seismic image maps and magnetic anomaly maps of targeted volcanoes. Then, detailed seafloor observation and sampling as well as deep tow side scan sonar survey were performed in KODOS 10H cruise on 5 volcanoes which are selected as targeted areas from the previous cruise. Among 5 targeted volcanoes, TA26 shows most extensive hydrothermal activity. Hydrothermal vents and alteration zone were observed on western caldera and summit of eastern cone of the TA26. Although only weak hydrothermal alteration was observed on eastern cone, mineralized fragments of chimney and mound were sampled from western wall of central caldera on TA25 volcano. On TA12 volcano, strong hydrothermal plume and alteration zone was detected during video tows operated between SW scoria cone and small ridge. However, only small amount of hydrothermal altered rocks were collected from TA12. Although hydrothermal activity and mineralization might be formed, supported by plume detection and result of geophysical survey, only weak alteration zones were observed on other two volcanoes (TA19 and TA22). The exploration area generally show shallow depth up to several tens of meters on summit where subsurface boiling of hydrothermal fluid might occur due to low hydraulic pressure, which can affect on styles of hydrothermal venting and mineralization process observed on Tonga submarine arc volcanoes.

Jan 1, 2010

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 Peter E. Halbach

The Central Indian Ridge (CIR), the boundary between the African and Indian plates, forms a SSE trending mid-oceanic accretionary system in the equatorial Indian Ocean (Fig. 1), extending to the northerly Carlsberg Ridge spreading center, and terminating at the Rodrigues Triple Junction (RTJ; 25°30'S, 70°06'E) by intersection with the Southwest Indian Ridge (SWIR) and the Southeast Indian Ridge (SEIR). Crustal divergence of the CIR proceeds at intermediate rates; a progressive increase of ocean floor accretion towards the south is documented: the present half spreading rate and ridge trend change from 1.80 cm/a and N142° at the equator to 2.73 cm/a and N152° north of the triple point. The topography of the central rift zone is rather smooth compared to slow spreading analogues such as the SWIR, but slightly more rugged than the SEIR. The rift valley is 500-800 m deep, 10-15 km wide and usually well defined. The inner floor, 2-4 km in width, is relatively flat along the axis and more variable in cross section, and lies at 2700-3200 m depth. Off set fracture zones striking generally N60° . in southern portions of the CIR and laterally displacing median valleys by as much as 8 km are often bent, uplifting crustal sequences up to several hundred meters. The length of individual spreading segments varies between a few and several tens of kilometers. The vertical displacement on normal faults are larger while lineaments are shorter than those of the faster spreading SEIR. The direction of lineaments measured on the southwestern and northeastern flanks of the southern CIR are N154° and

Jan 1, 1994

By Marco Figoni

The increased interest on deep water minerals resources is a challenge for both mining and oil industry. The exploration and production of oceans minerals require a synergy between of different technologies. While mining industry is leading the dredging and processing part of the system, oil industry is contributing through development of ore lifting technology based on existing subsea knowledge. The paper presents an overview, based on published projects around the world, of different approaches to marine mining. Several exploration techniques and offshore production systems were already designed and assessed, all of them with apparently positive results. Exploration phase is well advanced and in continuous expansion allowing the discovery of increasing resources around the world of different nature but production can be considered to be in an early stage. Different from onshore mining, subsea operations require a closer cooperation with international and local authorities to preserve as much as possible the environment. There are still many uncertainties at respect and all the exploration process must be carefully evaluated to allow subsea mining to develop in a sustainable manner. Technically, mining at seabed was already demonstrated and the process is based on three main components, namely seafloor mining tools, riser and lifting system and production vessel support. This layout is based on the concept that ore must be disaggregated at seafloor first, transported to surface in form of slurry that must be dewatered before loading to be transported to processing plants onshore. The challenges are rising because the environment and safety must be taken into consideration as a priority when evaluating the efficiency of the system. The most critical challenges regarding the production operations, especially in deep water are the deep-sea excavation process, the transport of large slurry volumes, the slurry abrasivity, the power supply management and the subsea

Sep 14, 2011

By Eleanor Martin

An examination of the draft Exploitation Regulations from an investor’s perspective. We will look at the commercial requirements of the investment community (debt and equity) in order to provide funding to a deepsea mining project, and contrast this with the position put forward in the draft Exploitation Regulations. We will then recommend suggested amendments to the Exploitation Regulations to assist future investment on this growing industry.

Jan 1, 2018

By Hal Palmer

A number of Articles contained in the United Nations Convention on the Law of the Sea III (UNCLOS) bear directly on legal issues related to the recovery of mineral deposits on the ocean floor. Mineral resources of the continental margin other than oil, gas and hydrates include, sand, gravel, shell, coral, gemstones and phosphorite. Jurisdiction over the exploration and exploitation of these deposits is determined either by the Territorial Sea claims of a coastal state or their recognized sovereign rights in the Exclusive Economic Zone (EEZ). At least 33 coastal states have the right under Article 76 (Continental Shelf regime) to claim seabed jurisdiction beyond 200 nautical miles (EEZ limit). In addition, several states have "Pioneer Investor" status with regard to seabed resources in international waters (The Area). A global maritime boundary database (GMBD) has been developed as a basic resource identifying the current claims of coastal states. It provides detailed information on existing boundaries and limits determined by the UNCLOS accords or by multi-lateral agreements which affect mineral exploration and exploitation. This paper will describe the GMBD and its construction and maintenance.

Jan 1, 2000

By Akira Usui

Fine-scale geochemical, mineralogical, and structural variations in ferromanganese crusts are believed to be the long-range records of paleoceanographic conditions and geological events on the small to global scales in the world oceans, which is useful in reconstructing marine environment. The chemical profiles of thick hydrogenetic ferromanganese crusts and nodules were determined by ICP/ES at 2-3 mm intervals at several locations over the Japanese Islands, Magellan Seamounts, Marshall Islands, and South Pacific Basins, together with Be-10 dating. We found general trend of Co enrichment (or high ratio of Co/Mn) in the upper layers of crusts, or outer layers of nodules, which formed in younger period probably after the late Miocene. This general trend of higher Co concentration in the surface may be true over the western to the Pacific, but local variations in growth patterns and shorter-range fluctuations in chemistry and structure were found as well. The growth rate is sometimes three times faster at the shallower depth even in a single seamount. The in-depth fluctuation of Co is well correlated with the ratios Mn/Fe ratio and Ce/La, suggesting changes in redox conditions during the growth of hydrogenetic ferromanganese crusts.

Jan 1, 2002

By D. S. Cronan

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

Jan 1, 1989

By Kokichi Iizasa

Kuroko-type deposits exist in Japanese EEZ. Some of them are present in the Izu-Ogasawara oceanic island arc south of Tokyo. Major two Kuroko-type deposits occur in the area. One is the Sunrise hydrothermal field occurring on the caldera floor of Myojin knoll, which is likely to be the developed stage in sulfide mineralization. Another is present in the crater of Suiyo seamount that is the early stage of sulfide mineralization. The two deposits are here presented on the growth history based on samples recovered by Benthic Multicoring System (BMS).

Jan 1, 2002

By Stewart B. Nelson

With the pending U.S. ratification of the United Nations Convention on the Law of the Sea (UNCLOS), the subject was raised as to the Convention's potential impact on U.S. ocean science. The Ocean Studies Board (National Academy of Sciences) elected to convene a two-day workshop in October 1995 to consider the potential impacts and to determine whether or not they warranted a more formal and intensive study. A review of the workshop discussions and deliberations concerning the matter of UNCLOS and U.S. ocean science will be presented.

Jan 1, 1996

By Brian D?Olier

Much of the aggregate that is being exploited at present from these areas is a ?relic? deposit. It was originally eroded from primary source rocks and transported to a depositional centre by processes that are now either greatly reduced in effectiveness or are largely absent at the present time. Following the retreat of the Devensian ice sheet, the subsequent rise of sealevel and the drowning of large areas of the continental shelf along with the lower reaches of many rivers, a fresh sequence of sediment sources, pathways and sinks now exist. Sediment is being eroded from several, pre-existing source areas and transported along different, well - defined pathways to a number of new depositional sinks. Some of the present, licenced, aggregate dredging areas lie close to these sources, pathways and sinks with the consequent dredging activity being perceived by some as interfering with the ?natural process? that links the offshore and the coastal / littoral zones. With this perception in mind, the principal, sources, pathways and sinks between Flamborough Head and Beachy Head will be highlighted and the relationship of dredging activity upon them, evaluated. It will be demonstrated that offshore dredging activity has no effect upon supplies of sediment to coastal beaches.

Jan 1, 2004

By Carolita U. Kallaur

In contrast with the United Kingdom, the Netherlands, and Japan, the marine mining industry in the United States exists at a very rudimentary level. Depletion of onshore resources has undoubtedly been an important factor in the development of marine mining industries abroad. However, the institutional framework presented by government can advance or present obstacles to the development of a marine minerals industry. The role of government involves questions of the degree of risk sharing between government and industry, as well as questions of the strategic and economic importance of developing the technology and the infrastructure to recover minerals. In 1984, the Minerals Management Service (MMS) created a program office to handle these questions and to respond to a potential increase in commercial opportunities that might result from the Presidential Proclamation establishing a U.S. Exclusive Economic Zone. A critical component to the success of the program has been the formation of partnerships with coastal States to pursue projects in areas of mutual interest. Such projects involve commodities showing commercial promise and strong public need. Such a cooperative approach lessens the risk of Federal, State, or private interests working at cross purposes.

Jan 1, 1992

By Fred C. Dobbs

To effectively manage the potential environmental impacts of deep-sea mining of manganese nodules, we need to know substantially more about the effects of sediment redeposition on abyssal communities and the time scales of recovery from such effects. As an initial step towards a predictive understanding of mining impacts on abyssal benthos, we are conducting a series of biological studies within the framework of the Benthic Impact Experiment (BIE). Mining operations will cause resuspension of sediments across extensive areas of the abyssal Pacific Ocean. The resultant plumes likely will produce redeposition layers, ranging from a few sediment grains in thickness to > 1 cm, over thousands of square kilometers of the seafloor. The impact of such redeposition on abyssal benthic communities is exceedingly difficult to predict. While there has been speculation that redeposition of 1 mm or less will exert deleterious effects, there has been very little testing, and the BIE will provide the first in situ test of redeposition impacts. In a series of cruises before and after controlled resedimentation, we are collecting biological samples to determine the undisturbed state of the ecosystem, the immediate effects of disturbance, and the time-course of recovery resulting from quantified levels of resedimentation.

Jan 1, 1992

By Jai-Woon Moon

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

Jan 1, 2000

By Kokichi Iizasa

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

Jan 1, 2005

The seafloor occurrences of KODOS ferromanganese nodules can be classified into four facies based on the morphological types of nodules recovered and seafloor photographs. Facies A, B, and C are relatively unimodal whereas Facies D is bimodal in the size distribution of nodules. Both Facies A and B are highly covered by sediments, but Facies B is higher than facies A in nodule density. Facies C has a high density of small nodules and many traces of bioactivity. Facies D is irregular in nodule density, but occurs close to basement near scarps (Fig. 1). The transparent layer (TL) on subbottom profile records (von Stackelberg et al., 1987) is composed of three sedimentary units, which in cores are distinguished by color. The uppermost Unit I is postulated to be deposited during the past 0.21 Ma and the middle Unit II between 0.42 Ma and 0.21 Ma (MOMAF, 1997). There exists a hiatus between Unit II and Unit III. Unit III was deposited from 3.5 Ma to 1.5 Ma as determined by 10Be/9Be and/or 87Sr/86Sr dating (MOMAF, 2004). Internal textures observed on cut sections of nodules suggest four stages of nodule formation (Choi et al., 2000). The nuclei are either unbroken old nodules probably of hydrogenetic growth (1h and 2h) in Facies A and C, or nodule fragments probably of early diagenetic growth (2d) in Facies D, whereas there are both types in Facies B. The layers surrounding the hydrogenetic nodule nuclei are of hydrogenetic growth (3h and/or 4h) in Facies C, and are of early diagenetic growth (3d and/or 4d) in Facies A, B, and D. The layers surrounding the early diagenetic nodule fragments are mostly of early diagenetic growth (3d and 4d) in Facies A, B, and D. But hydrogenetic encrustations are also found as surface layers on the top in Facies B (Fig. 2).

Jan 1, 2005