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By Olav Rune Godø

We present a science-based infrastructure for continuous online monitoring of the ocean interior including benthic, pelagic and the demersal habitats. It will reduce expensive ship based monitoring costs associated to offshore and coastal industries. We combine established Norwegian cabled observatory technology and German mobile seafloor robotic technology and thus supports the transition from local to spatial ecological monitoring. Both technologies are developed through science - industry partnerships. In Norway, the Institute of Marine Research has worked with Statoil ASA and Metas AS to install and operate the LoVe cabled observatory. The German technology is developed by iSeaMC and Kraken Robotik, two spinoff enterprises of the Helmholtz Alliance “ROBEX”. GEOMAR has recently developed a lander-based deep-sea crawler that operates autonomously based on the original iSeaMC crawler system using the Kraken Autonomy. Combined with the Spanish image processing and modelling expertise in the SME Deusto Sistemas SA the consortium hosts the capacity to establishing a complete semi-autonomous real-time monitoring system. Merging of existing technologies into one operational autonomous product through the unique competence of partners’ support international ambitions (e.g. Blue Growth, GES, Horizon 2020), and renew monitoring that assess impact of human use of the marine environment. The consortium has been invited to contribute to technology/science programs for the Yellow Sea and for European mining and offshore decommissioning industries, which demonstrates the leading role of our consortium. The project is funded through the EU Martera program and started in June this year.

Jan 1, 2018

By Kristian Drivenes, Steinar L. Ellefmo, Kurt Aasly, Ben Snook, Przemyslaw B. Kowalczuk, Rolf Arne Kleiv

"Since Ellefmo et al. (2014) published resource estimates of undiscovered seafloor massive sulfides (SMS) on the Arctic Mid-Ocean Ridge (AMOR), there has been an increased focus on establishing new knowledge about exploitation technologies for such deposits. This also includes understanding the process mineralogical properties of typical SMS deposits.The part of the AMOR that lies between Jan Mayen and the Svalbard Islands and is located within Norwegian jurisdiction and, as such, investigating the potential for mineral production from hydrothermal vent fields has been seen as strategic. The AMOR has been explored for active hydrothermal vent fields since early 2000s (Pedersen et al., 2010b). One of the active vent fields discovered, Loki´s Castle, is located in the northern part of Mohn´s Ridge. This vent field was first described by Pedersen et al., (2010a) and consists of two mounds, each approximately 100-150 m diameter and 20-30 meters high, hosting several active chimneys, up to 11 m high.Loki´s Castle has been selected as a case site in order to study the properties of typical SMS occurrences with respect to possible future deep-sea mining activities. As part of the MarMine cruise in 2016, the Loki Castle was visited and sampled for e.g. mineral characterization and mineral processing analyses. In total, more than 500 kg rock samples were collected using ROVs, and intended for further research (Ludvigsen et al., 2016). In addition to sampling mineralized rock fragments, survey data like bathymetry, magnetics and Underwater Hyperspectral Imaging (UHI) was collected using Automated Underwater Vehicle (AUV)."

Jan 1, 2017

By Steve Potter

"REVIEW OF ISA's DRAFT EXPLOITATION REGULATIONS – HAVE KEY STAKEHOLDERS' CONCERNS BEEN ADDRESSED ADEQUATELY?In early August 2017, the ISA published a revised draft of the exploitation regulations. My presentation will focus on the extent to which key State and Contractor issues raised in formal submissions in November 2016 have been addressed in the revised draft and any additional key issues in the revised draft which are likely to cause significant concern for Contractors.ABSTRACTFollowing the ISA's call for submissions in response to draft zero of the exploitation regulations in July 2016, 43 responses from stakeholders were received by the ISA in November 2016. My presentation will start by briefly looking at how the ISA has continued to engage with stakeholders following the publication of draft zero of the exploitation regulations, including at payment regime workshops in London (November 2016) and Singapore (April 2017) and at the environmental workshop held in Berlin in March 2017. It will also touch on the publication in February 2017 of what was in effect a very preliminary draft of the environmental regulations before moving on to consider in detail the extent to which key State and Contractor issues have been addressed in the ISA revised draft exploitation regulations which were published in August 2017. My review of the formal submissions will include, amongst other things, commentary on:(i) the level of Stakeholder response (State Parties to UNCLOS, Sponsoring States, Privately owned Contractors, State Owned Contractors and NGOs);(ii) the quality of the submissions (particularly by States and Contractors); (iii) the key concerns raised by State and Contractor stakeholders and how those issues have been addressed in the revised draft exploitation regulations; and(iv) how all stakeholders need to further engage with the ISA to ensure that the exploitation code adequately addresses the legitimate and reasonable concerns of each Stakeholder group (e.g. Contractors, Sponsoring States, Developing States and NGOs)."

Jan 1, 2017

By Francois P. Leroy

In the quest of studying the assigned blocks of seafloor for deep water mining, each member country of the ISA is thirsty for accurate information as to the level of resources available. Manganese nodules represent a large portion of the resources and are as precious as they are hard to locate and harvest. Resolving such challenges is what drives the technology development and yields instruments and products capable of serving this field of research. This presentation will study how manufactures of oceanographic instruments have pushed the technology envelop to in order to transform a collection of sensors and instruments into a seamless and adapted assembly working to serve the researcher and prospector in the challenging field they operate. Deep water data collection is characterized by the following challenges: ? Deployment, recovery and handling of the vehicle ? Producing high resolution at great distances ? Positioning that data with accuracy to relocate Teledyne Marine will present the work performed in its engineering laboratories to produce sub systems and systems now capable of delivering key information necessary to the proper cataloguing and exploitation of deep water mineral mining. Understanding and controlling the alternative resources available to each country will allow better management of current traditional land based minerals.

Jan 1, 2010

By Hunsoo Choi

Internal textures of manganese nodules from Clarion-Clipperton zone of northeastern Pacific Ocean are classified into five textural zones: columnar-textured layered zone, cuspate-textured layered zone, cuspate-textured massive zone, cuspate-textured porous zone and massive- textured massive zone. Vernadite is the main constituent mineral in the columnar- and cuspate-textured layered zone. Buserite sometimes occurs in the cuspate-textured layered zone. The cuspate-textured massive zone is mainly composed of buserite. Todorokite is also associated with buserite in the massive-textured porous zone, where cuspates and globes are partially replaced by massive texture. In the massive-textured massive zone, todorokite, buserite and birnessite occur together. The analyzed elements of all zones are also classified into four elemental groups by the cluster analysis of correlation coefficients: Mn group, Cu-Ni-Mg group, Fe group and Si group. Mn group consists of Mn and K. Cu-Ni-Mg group consists of Cu, Ni, Zn, Mg and/or Ca, Na. Fe group consists of Fe, Co, Ti and/or Ca, P. Si group consists of Si and Al. Each textural zone is composed of three or four elemental groups. These four elemental groups are correlated with mineral composition, such as, Mn group with todorokite, Cu-Ni-Mg group with buserite, Fe group with Co-bearing iron-oxyhydroxide minerals, and Si group with silicates.

Jan 1, 2002

By Kris van Nijen

IHC Merwede, a Dutch supplier of ships and equipment for dredging and mining activities, and DEME, a Belgian dredging and environmental services group, will enter into a joint venture for deep-sea mining activities. Under their cooperative agreement, IHC Merwede will be responsible for the development and construction of technical solutions, while DEME will be responsible for operations. Together the companies will offer a unique pioneering total solution. The joint venture will be known as OceanflORE.

Jan 1, 2011

By Paul M. Vercruijsse

Deep sea mining operations by nature are performed (or planned) in challenging environments. Another typifying characteristic of deep sea mining operations is the relatively high investment cost. This combination challenges engineers to design configurations able to mine the desired production rate in an efficient way. As design choices made for individual systems impact other parts of the system, it is vital to follow an integral approach to establish the one optimal overall system. Dredging and especially dredge mining learns that the excavation system, the slurry transportation system and the processing plant cannot be considered as individual sub-systems. These systems in any ?traditional dredge mining? operation interrelate to such extend that they must be developed towards an integral solution. The nominal production, peak production and variability of these figures must match for all subsystems in the overall mining system to optimize the mining efficiency. We call this the ?game of capacities?.

Jan 1, 2011

By Henk van Muijen

From an interesting and intriguing scientific research topic, deep sea mining has altered into an interesting mining prospect over the last years. Ten years ago most of the focus was on geological investigations, searching for typical deep sea deposits and getting answers on where we can find them and how these deposits were formed. At this moment we know much more about the interesting deposit possibilities and with our quest for minerals, metals and other materials to feed global economic growth, answers as to the technical and economic feasibility to mine these deposits are sought. This is not a new phenomenon as we already witnessed such question late 1970?s and early 1980?s. Most of the focus was on mining manganese nodules and brines in the Red Sea driven by the report of the Club of Rome that predicted shortages in near future at that time. Development went different, but later in the 1990?s a rival of interest could be noticed for mining deep sea deposits.

Jan 1, 2010

By B. Prause

Ferromanganese crust samples collected from Central Pacific sea-mount areas became of special interest after surprisingly high nobel metal contents have been analyzed. Hydrogenetic crust growth is controlled by the conditions of the oceanic water column. Thicker encrustations show two crust generations of different age ranges. The mean values of the chemical composition state that the older generation is richer in P, Ca, Ni, Cu, Zn, and Pt and depleted in Fe, Ti, Co, Al, and Si. The differences apparently indicate a distinct change of the geochemical environment. The Pt concentrations vary up to 1800 ppb and do not clearly correlate to one of the other metals. This might indicate a bond of multiple nature. Several mechanisms have been proposed to explain the Pt concentrations in ferromanganese samples. Our models consider seawater and cosmic spherules as responsible Pt sources. In seawater the main species of dissolved Pt probably exist as the doubly negatively charged tetrachloro-complex. A precipitation of Pt in seawater may take place if the chloro-complex is decomposed by reduction of pt2+ to pt0. On the other hand, the Mn02 precipitation is caused by an oxidation of Mn2+ which is supplied from the oxygen-minimum zone. The large activation energy needed for the oxidation of divalent ~n" in solution has been recognised, and the resulting slowness in the formation of Mn(V1)-oxihydrate sug

Jan 1, 1989

By Pedro Madureira, Georgy Cherkashov, Harald Brekke, Marzia Rovere

"The most promising deep-sea mineral resources for exploration in the Area (beyond the limits of national jurisdiction) are polymetallic nodules, cobalt-rich ferromanganese crusts and polymetallic sulphides. These marine minerals have different characteristics in their distribution, geological setting, grades of metals and genesis. Considering future exploitation of nodules, crusts and sulphides such parameters as estimated resources, specific mining operations and ore processing are different as well.Comparative analyses of deep-sea mineral minerals as well as onshore and offshore resources will be discussed in the paper."

Jan 1, 2017

By Natalia Konstantinova, Kira Mizell, James R. Hein, Georgy Cherkashov, Amy Gartman, Mariah Mikesell

"Two types of metallic deposits have been found in the deep Arctic Ocean: Hydrothermal Fe, Cu, and Zn sulfide deposits form along Gakkel Ridge in the Eurasia Basin and associated ridges between Greenland and Europe; and iron and manganese oxide crusts (Fe-Mn crusts) and nodules, precipitated from seawater onto rock surfaces in the Amerasia Basin, contain many rare metals of economic interest. Fe-Mn crusts and nodules collected in the Amerasia Basin during 2008, 2009, and 2012 cruises on the USCGC icebreaker Healy are characterized by unique mineral and chemical compositions, very high Fe/Mn ratios, fast growth rates, and other unique characteristics compared to those formed elsewhere in the global ocean. These characteristics reflect temporal and spatial variations in geological, oceanographic, and climatic conditions in the Arctic Ocean and surrounding continents over the past ~15 Myr.RESULTS AND CONCLUSIONSDiscrimination diagrams show that the crusts and nodules found in the Amerasia Basin north of Alaska are hydrogenetic. However, the mineralogy is not typical for hydrogenetic Fe-Mn crusts and nodules, which usually include only amorphous Fe oxyhydroxide and ?-MnO2 (vernadite). The Arctic samples also include the Mn oxides birnessite and 10Å manganates (todorokite, buserite, asbolane), and the Fe minerals also include goethite, lepidocrocite, feroxyhyte, and ferrihydrite. This mineralogy reflects formation under lower oxygen conditions than typical for samples formed elsewhere.The Amerasia Basin crusts have a unique chemical composition compared with crusts from other areas of the global ocean. The key difference is the high Fe contents relative to Mn contents, which determines the types of trace metals hosted by the Fe-Mn oxide phases, and their concentrations. The high Fe/Mn ratios reflect the expansive continental shelves (>50% of the Arctic Ocean) and upper slopes that support redox cycling and release of Fe and other metals to bottom waters, and to the large fluvial input from North America and Siberia. Brine formation on the shelves and currents promote the distribution of the metals throughout the Amerasia Basin, including the deep basins."

Jan 1, 2017

By Dilip Sarangdhar

"SeaTech Solutions International (S) Pte Ltd, Singapore are the designers of world’s first seabed mining ship. The ship is now under construction and expected to be delivered next year. The Deep Sea Mining industry is eagerly awaiting commencement of her seabed mining operations and the success of this story will go a far way in accelerating investment in Deep Sea Mining and hopefully we should see many such projects take off and many such ships launched in the near future.Based on own experiences SeaTech discusses in this paper, various important issues that need to be considered for design of such Deep Sea Mining ships, the challenges faced and possible solutions to address them.From a ship designers’ perspective, there are not many direct previous references available, the seabed mining methods and associated equipment are also a new technology & products are still developing, there is no standard method and equipment for processing of mineral ore onboard, and above all there is the huge challenge of loading, storage and discharge of ore cargo efficiently in the confines spaces. Associated with the uncertainties of such issues is the uncertainty of weight, space, power, services and maintenance requirements, which can vary through the design and construction period and put the initial ship design at huge risk. Sufficient design margins need to be provided and a constant & strict control is absolutely necessary to ensure that the budget on each technical aspect is not exceeded. The local strength of the vessel particularly needs to be robust to take ultra-large loads due to huge equipment and their lifting /handling equipment/winches and tall mining process modules."

Jan 1, 2017

By Robert G. Ditchburn

Dating seafloor mineralization at hydrothermal centres of submarine arc volcanoes is important for understanding deep-seated volcanic events that can produce deposits rich in base and precious metals. The activity ratios, 228Th/228Ra, 228Ra/226Ra (Bq.Bq-1) and 226Ra/Ba values (Bq.g-1) are used for dating barite- rich seafloor massive sulphide (SMS) in the age ranges 0.3 ? 12 years, 3 ? 35 years and 500 ? 15,000 years, respectively. Thus, the time elapsed to amass an economic deposit and, ultimately, its capacity for sustainable extraction, can be estimated. 226Ra/Ba and 228Ra/226Ra values have been measured in relatively young chimneys that were collected, 1998 to 2006, from hydrothermal sites at Brothers and Clark volcanoes (Kermadec arc) and East Diamante volcano (Mariana arc) to check these initial ratios, essential for calculating ages for older mineralization at the same sites, were not varying significantly. We found that the 226Ra/Ba value for fresh SMS mineralization at the Brothers NW caldera and East Diamante hydrothermal sites have been reasonably stable for 6 years and 2 years, respectively. At both sites, the 228Ra/226Ra value for fresh SMS has been stable for 5 years. This was established from young chimneys where the measured 228Ra/226Ra value could be corrected for radioactive decay using the age derived via the 228Th/228Ra method. However, long-term stability of the initial 226Ra/Ba and 228Ra/226Ra values has yet to be proven. These isotopes of Ra are used as a proxy for better understanding of the transfer of Ba from deep magmas to the seafloor, via the circulating fluids of the hydrothermal system.

Jan 1, 2011

By Lu Jun

Up to now, much data on marine minerals, as well as on marine geochemistry, have been accumulated. Modem computer databases provide optimum flexibility and power for manipulating these data. The best worldwide marine mineral database is currently the Marine Minerals Bibliography and Geochemical Data Base created by Carla Moore et al. at the National Geophysical Data Center in the United States. In fact, in the course of studying marine minerals and geochemistry we may collect not only digital-character type data but also graph and image (black-white, grey and color image) data types. For instance, correlation diagram between chemical compositions of minerals, spectroscopic graphs, (e.g. infrared spectra, Mossbauer spectra, etc.), grey or color images from both optical and electron micro- scopes (scanning or transmission electron microscopes) as well as seabed photographs. Charles L. Morgan et al. (1993) reported that 10,000 photographs and some video images of the seabed in the Clarion-Clipperton region of the northeastern tropical Pacific have been collected by the Ocean Minerals Company. If both graphic and analytical information were stored in a database, it would be very useful and convenient to marine geologists. This system would not only be able to search for all the data based on one parameter, but also for both size and composition distributions. If possible, geostatistical methods could be combined with fractal dimensional methods. Of course, this would require enormous efforts. Before multimedia technology emerged, it was very difficult to create image databases. The emergence of large-capacity compact discs, high-speed central processing units, and high-speed digital signal processing techniques makes it possible to establish multimedia database management systems (DBMS), image-text DBMS, that involves graphs, text, images, and sound. In order to store image fields in a DBMS, we have to take into account two problems: (1) image access format and (2) image compression code standard.

Jan 1, 1994

By Gerald R. Dickens

Massive sulfide ores and Fe-Mn oxyhydroxide precipitates represent two extremes of a spatial continuum of hydrothermal deposition along oceanic ridges. Elemental variations across this continuum are of interest to economic geologists as a prospective geochemical exploration tool. Theoretical considerations suggest that certain physical and chemical parameters can be used to model compositional variations within the far-field (i.e., Fe-Mn oxyhydroxide) component as a function of distance from ridge axis; however, testing and verification of such models generally has been precluded because the few available distal hydrothermal sediment sequences have been sampled at low resolution and/or are highly diluted with biogenic components (e.g., siliceous and calcareous tests). Recent ocean drilling (ODP Leg 145; Sites 885/886) in the North Pacific successfully recovered an extensive record of "biogenic-free" distal hydrothermal precipitates from an area approximately 60 km south of the Chinook Trough at longitude 168.1 °W. Geophysical and geomorphological evidence suggests the Chinook Trough is the southern lithospheric scar marking initiation of late Cretaceous north-south rifting, implying that recovered hydrothermal materials record distal hydrothermal precipitation from the now-subducted Kula-Pacific spreading ridge. The Chinook Trough hydrothermal sequence is a continuous 15 my record of "biogenic-free" hydrothermal Fe-Mn oxyhydroxide precipitation mixed with eolian clays. It was deposited during the late Cretaceous, early Paleocene (80-65 Ma) as the perpendicular distance from ridge axis increased from 75 to 600 km. A high-resolution geochemical analysis of this hydrothermal sequence reveals distinct trends for the up-core (equivalent to increasing distance from ridge) distribution patterns of Fe, Sc, As, and rare earth elements (REE). Iron concentrations exhibit an S-shape distribution pattern with respect to increasing

Jan 1, 1994

By Richard Mills

Autonomous Underwater Vehicles (AUVs) are proven technologies used across market segments for survey, exploration and environmental monitoring tasks. When coupled with other autonomous platforms or sensor packages AUVs become part of an holistic system approach to exploration and environmental assessment and monitoring. Recent developments have seen AUVs deployed remotely with instantaneous access to data via the cloud. Our goal is to deliver the capabilities of each of these elements and present a cohesive data set with automated processing tools over a cloud based interface. nmanned Technology AUVs The HUGIN AUV System is the most commercially successful AUV ever built. Operated as a single vehicle, or as part of a swarm, HUGIN’s area coverage rate is unrivalled. Equipped with a comprehensive sensor package including Kongsberg’s synthetic aperture sonar, it collects a data set. Some of these data are processed in-mission to enable operators to readily access it when the vehicle is recovered. HUGIN is well suited to mining survey and exploration. Capable of reaching 6000 metre depths and conducting missions greater than 60 hours, HUGIN collects seabed sonar imagery, sub-bottom profiles, laser and camera images plus environmental data, with sensors running concurrently.

Jan 1, 2018

By Peter E. Halbach, Andreas Jahn

Co-rich hydrogenetic ferromanganese crusts are typical marine interface products of growth processes taking place on sediment-free substrate rocks on the seafloor. They grow very slowly and preferentially in water depths below the oxygen-minimum zone (OMZ) and have so far been found even in water depths of up to more than 5000 m, i.e. also below the calcite compensation depth (CCD); these deep ferromanganese crusts are particularly rich in Fe. It is assumed that the O2-minimum zone is the most important source layer of dissolved manganese, the decomposition of fecal pellets here also contributes to this Mn-budget. The process of hydrogenetic precipitation is basically an inorganic colloidal-chemical as well as a surface-chemical mechanism. Microbial mediations can be assumed, in particular since steps of redox-reactions are involved. The two main components of the hydrogenetic substance are hydrated d-MnO2 (vernadite) and x-ray amorphous Fe-oxyhydroxide, both of which are intimately intergrown with each other forming the extremely fine-grained hydrous oxidic material. In seawater, elements occur as dissolved hydrated ions or as inorganic as well as organic complexes which, in general, have either a positive or a negative surface charge depending on the pH of the respective marine environment. These complexes form hydrated colloids that interact with each other or with other dissolved hydrous metal ions. The main agent to oxidize the dissolved Mn2+ ions is oxygen, transported upwards from deeper water by turbulent eddy diffusion and turbulent rise processes at seamount slopes.

Jan 1, 2017

By C. R. Pearce, B. Murton, S. Howarth, P. Lusty

"With the expansion of “green” energy technologies, the demand for the critical raw materials required to sustain this growth is increasing. Many E-tech elements, including tellurium (Te) and rare earth elements (REEs), suffer from high supply shortage risk and the need for more diversified metal supply routes is driving research into alternative resources. Hydrogenetic ferromanganese crusts, seafloor deposits of Fe- and Mnoxyhydroxides that form from the direct precipitation from seawater, present a potentially important future source of E-tech elements. With growing interest in the potential wealth of these deposits and the issuing of permits for deep-sea mining and exploration, more work is underway to understand the nature of ferromanganese crust deposits, their elemental concentrations and distributions, and the potential impacts of mining activities.This research focusses on the formation of ferromanganese crust deposits and processes that control the extreme enrichment of elements such as Te, Co and REEs. The crusts were systematically sampled and mapped between ~ 1000 – 4000 m depths using ROV ISIS, from a range of environments, substrates and morphologies from Tropic Seamount (NE Atlantic) in order to determine the seamount-scale factors that control major and trace elemental concentration variations. These factors include depth, surface roughness and micro-bathymetry, location relative to long-term mean current direction and energy, influence of tidal energy dispersion across the seamount, sediment supply, substrate lithology, biological productivity and phosphatisation. The study analyses trace-element characteristics of 100 ferromanganese crust samples alongside standard reference materials NOD-A-1 and NOD-P-1 (US Geological Survey manganese nodules). At this initial stage, we report results from whole rock acid digestion and ICP-MS analyses."

Jan 1, 2017

By Jon Machin

?ORE? is defined as ?mineral/s that can be mined at a profit?. So, what is ORE at 2,000 m water depth? Is it 5% Copper or 1.8% Nickel/Cobalt? One of the key factors that determine what is ORE, profitable or not, is the cost of mining and extraction. Therefore a determination of ORE requires a commercial and technical appreciation of both sea bed mining equipment and mining options. Perry Slingsby Systems (PSS) have built more remotely operated submarine work vehicles, including 900HP trenching machines, than any other company. With Nautilus Minerals, PSS have been studying a range of deep ocean mining solutions. This paper discusses the commercial and technical issues of various extraction techniques applicable to deep ocean mining from 1,500 m to 5,000 m water depth. Issues such as the rate of extraction, (i.e. tons per hour) is a key economic component and is often constrained by the design and horsepower of the miner. Likewise the design itself of the mining machine and cutting heads can determine the size of material produced which impacts on methods of lifting the ore to surface. Issues such as overburden, sea floor conditions, style of mineralization and physical properties of the ore, obviously affect the selection of appropriate mining machine configuration.

Jan 1, 2004

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