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By Tetsuo Yamazaki

The Kuroko-type seafloor massive sulfides (SMS) in the western Pacific have received much attention as sources for economic recovery of gold (Au), silver (Ag), copper (Cu), zinc (Zn), and lead (Pb). Since the end of the 1980s, the Kuroko-type SMS have been found in the back-arc basins and on oceanic island-arc areas. In Okinawa Trough (Halbach et al., 1989) and on the Izu-Ogasawara Arc (Iizasa et al., 1999) are the typical representatives in the Japan’s EEZ. They yield a higher concentration in Au and Ag than the SMS found in ocean ridge areas (Rona, 1985). Similar formation processes with the Kuroko ore deposits on-land in Japan have been expected and outlined by many researchers (Sillitoe, 1982; Scott, 1985). The higher Au and Ag contents have increased the chances for profitable mining operation, which is under consideration by a private company (Malnic, 2001). Information about the resource potential of the targeted Kuroko-type SMS deposit, such as the amount of SMS ore body, the inside structure, the mean metal yields, and the geographical details are necessary for a technical and economic validation analysis for the development. The Sunrise Deposit of Myojin Knoll on Izu-Ogasawara Arc in the Japan’s EEZ is selected as a target for the technical and economic validation analysis. The relatively higher amount of information on its resource potential is the reason why the deposit is selected.

Sep 24, 2006

By Usui Akira

Mode of occurrence and compositional variations of iron-manganese deposits from seamounts around the NW Pacific submarine island-arc area are described on the basis of on-site description during the Moana Wave Cruise MW9507 and other Japanese cruises, as well as geochemical and mineralogical analyses and dating on collected samples. Hydrogenetic and hydrothermal iron-manganese crusts occur at more than 80 sites out of 150 dredge hauls within a small area of 200x 200 km in the back arc region. The hydrogenetic crusts may have grown continuously at slow rates, but 2-3 times faster than those from the Central Pacific, associated with depletion of Co, Cu, and Ni contents. The site-maximum thickness of the hydrogenetic deposits trends to increase with the increase of distance from the active volcanic chain or the age of substrate volcanic rocks. Also the observed great local variations in thickness within single sites and on small scales may be resulted from post-depositional geological activity at the seamounts such as calcareous sedimentation, collapse of volcanic body and mass wasting,. On the other hand, the rapid hydrothermal manganese mineralization has occurred in place and time during arc volcanism and rifting and is still in progress at modern active areas. The ninety ICP/ES chemical plus XRD analysis show that these deposits are of distinct composition by origin or topographic provinces, but small-scale variation of the deposits of each origin and micro-scale depth variation are not clear.

Jan 1, 2000

By Fredrik Søreide

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

Jan 1, 2004

By Mark D. Hannington

Drilling of the active Trans-Atlantic Geotraverse (TAG) deposit during ODP Leg 158 indicated that the size of the mound-stockwork complex is approximately 3.9 million tonnes, including 2.7 million tonnes of massive and semi-massive sulfide (ca. 2% Cu) at the seafloor and 1.2 million tonnes of mineralized breccias (ca. 1% Cu) in a subseafloor stockwork. Quartz-pyrite veining in the stockwork zone extends from about 40 meters below seafloor (mbsf) to a depth of 95 mbsf. Siliceous wallrock breccias in the lower part of the stockwork grade abruptly into chloritized basalt breccias at the margins of the mineralized zone, and massive sulfides at the flanks of the deposit onlap relatively unaltered, partially hematized basalts. The pipe-like dimensions of the stockwork zone do not exceed the diameter of the sulfide mound. Comparisons with samples collected during earlier dive series confirm that the vent complexes at the surface of the mound are not representative of the bulk composition of the deposit. Dramatic vertical zonation of metals within the mound suggests that a long history of hydrothermal reworking has effectively stripped the constituents that are soluble at lower temperatures from the massive sulfides and concentrated them at the top of the deposit through a process of zone refining.

Jan 1, 1998

By B. J. Bluck

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

Jan 1, 2004

By Isobel Yeo, Florent Szitkar, Sven Petersen, Sebastian Graber, Meike Klischies

Technological advances and the shift towards green energies in the last decades have led to a substantial increase in the demand for metal resources. With rising political tension, and quasi-monopolistic production of some key metals, a secured supply chain cannot be guaranteed [1]. Therefore, the focus of the international research community and mining companies has expanded to the seafloor, looking for additional resources. The seafloor may have the potential to contribute significantly to a secure metal supply in the future. However, we have only investigated a fraction of our oceans in sufficient detail to assess the global resource potential. A detailed exploration of the vast seafloor is currently economically not feasible, due to its extremely time-consuming and costly nature. Seafloor massive sulfides generally form along the active plate boundaries and at active volcanoes in arc settings. However, the resources are not evenly distributed on the seafloor. Large deposits tend to be more common along slow-spreading and ultra-slow- spreading ridges that make up the majority of the global mid-ocean ridge system [2]. Therefore, it is important to establish geological models and exploration criteria in order to narrow down the permissive areas, which are likely to accommodate economically interesting deposits. Based on a detailed study of the TAG hydrothermal field in the central Atlantic Ocean, hosting a large active mound as well as several inactive mounds, we develop exploration methods and criteria to define areas of potential massive sulfide occurrences along slow-spreading sections.

Jan 1, 2018

By Hunsoo Choi, Sung Rock Lee, Ian J. Graham, Ian C. Wright

This is a part of the joint KIGAM-GNS-NIWA 3-year study of ferromanganese modules in the Campbell Nodule Field, east of Campbell Plateau to determine age distribution, growth rates and geochemical evolution in relation to geographic setting. The petrography, chemistry, inferred genesis, and 10Be/9Be dating of the nodules were described in the science report of GNS (Chang et al., 2003a, 2003b; Graham et al., 2003a) and presented at UMI (Chang et al., 2003c; Graham et al., 2003b). The morphology and distribution of ferromanganese nodules were also published in detail (Wright et al., 2005). This presentation is only concentrated on the mineralogy and chemistry of the nodules.

Aug 24, 2006

By Steven D. Scott

A geologist can be likened to a medical pathologist trying to figure out from faint clues how something had lived and how it died, often long after the event. Present-day seafloor hydrothermalism has empowered geologists/pathologists to dissect a living system, in this case volcanogenic massive sulfides (vms) deposits of copper, zinc, lead, silver and gold. On the other hand, a considerable amount of our understanding of seafloor hydrothermal processes and its products stem from our knowledge, much of it from industry, of these same processes and products that formed ancient ores in oceans as much as 2700 million years ago and are now mined on land.

Aug 24, 2006

By Elisabetta Tedeschi, Razieh Nejati Fard

Deep-sea mining is in the future perspective of mining industry and it is currently in the technological development phase. The focus of this study is on the electrical power system that provides sufficient energy for the mining equipment at the seafloor, excavating Seafloor Massive Sulfide (SMS) deposits. SMS deposits usually exist at water depths between 1500 m and 4000 m. Despite the similarities of SMS deposits excavation to the open-pit terrestrial mines, more energy is required to drill and crush the ores in the hyperbaric conditions [1], which can be done whether by static trench cutters [1] or by mobile mining crawlers [2]. In addition, the ores vertical transportation by subsea pumps requires several MW electrical power that can be supplied by all-electric subsea motors or hydraulically from water injection motors located on the surface. The power requirements can be fulfilled by an offshore or subsea power network. As the SMS mines are usually in remote locations, the straightforward solution will be an isolated offshore grid mounted on a vessel or platform similar to the most of offshore Oil & Gas projects. These power systems resemble the onshore microgrids for industrial purposes operating in island mode. However, in contrast with the onshore power networks, there are space and weight limitations in offshore infrastructures, which impose the design compactness to be a priority. In addition, having a very high reliability is necessary in the design approach of the offshore projects due to the extraordinary high expenses corresponding to repair and maintenance. The other design criterion is to improve the power system efficiency in order to reduce the size of the power equipment cooling apparatus, operational costs and CO2 emissions produced by diesel/LNG onboard generators. There are a few studies considering power system distribution for seafloor mining industry. Among them, [3] has investigated the AC and DC alternatives for SMS mining in 2400 m water depth by considering Solwara 1 project scenario introduced by Nautilus Minerals Inc. [2]. In this study, a power system design tool will be presented taking into account various water depth, power consumption levels, different distribution configurations (AC and DC) and the aforementioned design criteria.

Jan 1, 2018

By Andrew G. Hudson

The long-term economics of each of the four principal metals in marine manganese nodules (copper, nickel, cobalt and manganese) was evaluated to determine the anticipated viability of a nodule mining venture based on existing studies of the potential profitability of a nodule project. This included assessments of the lifetimes of land-based reserves, and examination and econometric modelling of the economic variables thought to affect nodule metal prices and demand. These analyses demonstrated that a) land-based reserves of the nodule metals were likely to last well into the future (100 400 years); b) average nodule metal paces were likely to stay a low levels for the foreseeable future; and c) the expected revenue stream from a twenty- ear nodule mining venture was substantially (42%) below that required to attract the necessary investment capital for such a high risk venture.

Jan 1, 1996

By Kyung-Ho Park

The smelting leaching process is known as one of the most favorite methods for the processing of deep-sea manganese nodules because of its smaller environmental impact and easiness of manganese recovery. The sulphuric acid pressure leaching of the matte prepared from deep-sea manganese nodules was studied to dissolve the valuable metals. Almost complete dissolution of Cu, Ni, and Co from matte was achieved under the following conditions: leaching temperature 180°C, time 4 hours, PO2 10 kgs/cm2, acid concentration 2.5% (vol/vol), pulp density 5%, ammonium sulphate 40 g/l. Under these conditions the iron concentration of leach liquor was 0.95 g/l. Optimization of leaching parameters was carried out by statistical design of experiments using 23 full factorial matrix. The linear and interaction co-efficients were evaluated for dissolution of metal values and also for iron concentration in leach liquors.

Jan 1, 2003

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 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 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 P. A. Rona

The first hydrothermal mineral deposits found at a seafloor spreading center were discovered in the Red Sea by multi-national research vessels between 1963 and 1965. At that time, the deposits were considered a special case related to continental rifting and an early stage of opening of an ocean basin. Since that time, examples of almost all major varieties of volcanic- and sediment-hosted hydrothermal deposits associated with basaltic rocks in the geologic record have been found at present spreading centers. Review of over 100 hydrothermal mineral occurrences presently known at oceanic ridges and rifts indicates that a range of deposit sizes from small to large (> 1 x 106 tonnes) occurs at all seafloor spreading rates. However, larger deposits but fewer per unit length of spreading axis appear to form at slow- than at intermediate- to fast-spreading centers based on available data. Larger deposits are more common in sediment-hosted than in volcanic-hosted settings regardless of spreading rate. A spectrum of hydrothermal deposit varieties (stratiform, stockwork and disseminated sulfides; various forms of sulfate, carbonate, silicate, oxide and hydroxide deposits) occurs in almost all of the tectonic settings. High-intensity, ore-forming, subseafloor, hydrothermal convection systems that conserve heat and mass and concentrate hydrothermal precipitates are extremely localized by anomalous physical and chemical conditions relative to nearly ubiquitous low-intensity hydrothermal activity at and flanking seafloor spreading axes at all spreading rates. Two distinct shapes of volcanic-hosted

Jan 1, 1989

By Jan Willem van Bloois

IHC Merwede is world market leader in the construction of specialist dredging equipment; it is a company with a rich history. The Netherlands is a coastal western country for which water management is a very important issue. Without the enclosure of the coastal areas with dikes and dunes almost two third of the Netherlands would be flooded. These activities are mostly performed by the dredging industry and are the foundation of the dredging industry as it is today. Besides land protection this industry also carries out infrastructure maintenance and performs land reclamation projects. In essence the dredging industry is specialized in horizontal excavation activities and operations in shallow waters with the purpose of gathering bottom sediments and disposing it at a different location. The development is that the activities are moving to deeper waters to a depth of up to 150m. A few years ago IHC Merwede received a request to perform the shallow water excavation techniques at a depth of approximately 2000 meters for the deep sea mining market. In response to the increasing number of requests for deep sea dredging and mining application solutions, IHC Merwede combined all of its activities in this sector to create a new, specially equipped operational unit, IHC Deep Sea Dredging & Mining (IHC DSDM).

Jan 1, 2010

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 Jonguk Kim

Hydrothermal sulfides were recovered from the16°50?S triple junction area in the North Fiji Basin, at a water depth of ca. 1900 m. The chimney samples can be divided into three groups according to their major metal contents: 1) type 1 (Fe-Cu-rich), 2) type 2 (Fe-Cu-rich with minor Zn), and 3) type 3 (Zn-rich) chimneys. Type 1 chimneys are mainly composed of chalcopyrite and pyrite, and are enriched in elements commonly precipitated under high temperature conditions (> 300°C), such as Cu, Co, Mo, and Se. Type 3 chimneys consist dominantly of sphalerite and marcasite with traces of pyrite and chalcopyrite, and are enriched in elements commonly associated with low temperature (150 to 250°C), such as Zn, Cd, Pb, As, and Ga. Type 2 chimneys show mineralogy similar to that of type 1 chimneys but their metal contents range between type 1 and type 3 samples. Trace element compositions of basaltic rocks indicate that magma generation in the triple junction area was influenced by two different sources: N-MORB and E-MORB. Sulfur and lead isotope patterns of the hydrothermal chimneys show distinct differences between the type 1 and type 3 chimneys. For example, type 1 sulfides are depleted in 34S and have lower Pb isotope ratios compared to type 2 and 3 chimneys. The d34S values (0.4 to 5.6?) of chimney sulfides are typical range of sulfur isotope composition of sediment free mid-ocean ridge hydrothermal system. Type 2 and 3 sulfides show slightly higher d34S values than type 1 sulfides, which can be explained by subsurface boiling of hydrothermal fluids followed by mixing of saline solutions with ambient seawater. Lead isotope compositions of the chimneys indicate that the Pb in type 1 and type 3 chimneys originates from hydrothermal leaching of N-MORB and E-MORB volcanic rocks, respectively. Considering that both these chimneys are located in the same area, our model suggests that type 1 chimneys formed by hydrothermal circulation controlled by an intrusion of N-MORB magma; the fluids were not influenced by boiling during the formation of type 1 chimneys. In contrast, type 3 chimneys are younger and were formed by hydrothermal circulation closely related to E-MORB magma intrusion at shallower depth. The necessary conditions for phase separation of the hydrothermal fluids that formed the type 3 chimneys might result from changed P-T conditions in a shallower high-temperature reaction zone beneath the hydrothermal venting site. Under these conditions the fluid may cross the two-phase boundary for seawater, ensuring subcritical phase separation. The mineralogical and geochemical properties of these chimneys suggest that type 1 and type 3 chimneys were probably black smoker and white smoker, respectively. Type 2 chimneys might be product of low-temperature replacement of type 1 chimneys, which is related to formation of type 3 chimneys.

Jan 1, 2005

By Robert G. Ditchburn, Cornel E. J. de Ronde, Bernard J. Barry

The age of mineralization, its mode of formation, the time elapsed to amass an economic deposit, its capacity for sustainable extraction and, ultimately, its grade and tonnage, are key aspects in the economic viability of volcanic massive sulphide (VMS) deposits (Ditchburn et al, 2004). Radiometric dating methods applied at GNS Science have been recently refined with the purpose of efficiently determining the ages of seafloor VMS mineralization along active intraoceanic arcs. These developments include: determining the longevity of seafloor hydrothermal systems, details of individual chimney and massive sulfide mound growth, and insights into deep-seated processes, such as the transfer of elements from magmas to their overlying hydrothermal systems. In our pursuit to better understand seafloor hydrothermal systems along intraoceanic arcs, we have thus far compiled age information for three volcanic centres of the Kermadec arc (South Pacific) and one of the Mariana arc (NW Pacific).

By James C. Barker

Concern over the availability of domestic critical and strategic mineral supplies has led the Bureau of Mines to evaluate the reserve development potential of alternative sources in Alaska. Near the village of Platinum, on the southwest Alaska coast, the Red Mountain concentrically zoned ultramafic complex is a source of onshore alluvial placers containing platinum-group-metals (PGM). It has long been suggested that valuable placers may also underlie the shallow coastal waters of the Bering Sea. A direct correlation of placer PGM and chromium to ultramafic rocks in the area was studied by the Bureau and the extent of the complex was mapped. Magnetometer and gravity data and geological studies suggest the complex is a large lensoidal body trending several kilometers offshore to the southwest with a probable steep southeasterly dip. Multiple Pleistocene glaciations and marine transgressions have eroded the western and southwestern portion of the complex. Sediments containing PGM, chromium, and associated gold (largely derived from glacial till) have been transported northward along the advancing coastline by littoral currents. Beyond the breaker zone, these sediments are generally buried by recently winnowed sand and gravel transported by strong longshore tidal currents. There is also evidence that paleoplacer channels underlie the marine sediments.

Jan 1, 1986