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By H. Shimoda, K. Tamaki, K. Iizasa, M. Watanabe, K. Okamura

Modern Kuroko-type deposits occur in submarine calderas of island-arc fronts and back-arc rifts in Japan. They occur primarily on or adjacent to caldera boundary faults. Hydrothermal sulfides in the Myojinsho submarine caldera are one of Kuroko-type deposits, but their occurrence is different from other deposits found within the area 200 km2 around the Quaternary volcanic front of Izu-Ogasawara arc.

Aug 24, 2006

By Nobuyuki Okamoto

The 21-year long-term Japan-SOPAC Cooperative Deep-sea Mineral Resources Study Programme was completed in March 2006. The Programme, which commenced in 1985, has seen numerous marine research surveys being conducted within the Exclusive Economic Zones (EEZs) of 12 SOPAC member countries (Figure 1). The various research and government institutions that have been closely involved in this longstanding Programme include: the Japan International Cooperation Agency (JICA); Japan Oil, Gas and Metals National Corporation (JOGMEC) (formerly, the Metal Mining Agency of Japan, MMAJ) and relevant ministries of the participating Pacific Island governments.

Sep 24, 2006

By S. C. W. de Jong, E. de Hoog, J. M. van Wijk, S. J. Dasselaar

Introduction Technology development for sustainable, safe, reliable and efficient mining of polymetallic nodules in the deep seas requires careful design, thorough understanding and integrated testing of all equipment, physical processes and (sub) systems involved (Dasselaar et al [1]). Proceeding from Vertical Transport System (VTS) experiments at IHC laboratory scale by Van Wijk [2], with typical system dimensions of several meters, to prototype or pilot scale testing with typical dimensions of several kilometers, is a giant leap. Naturally, intermediate steps are required in order to mitigate the possible risks in the full-scale system’s (physical) processes. Within the EU program Blue Mining (2014-2018), possibilities emerged for performing experiments at intermediate scale: the so-called medium-scale vertical slurry experiments. Near Freiberg, Germany, the village Halsbrücke possesses a 140 meter deep empty vertical mine shaft, perfectly suited for housing the test setup. For this purpose, a 318 meter long 145 mm pipeline circuit was constructed, including both a 130 meter high vertical riser and fall pipe section. A purpose-built sediment injection and separation system was deployed, including a 55 kW centrifugal pump. The riser section has been equipped with sensors capturing pressure, temperature, flow velocity, volumetric concentration and flow visualization. The planning, modification and construction of the test facility site itself is described by Müller et al [3]. The present paper describes the objectives, experimental program, equipment, and the preliminary results. Publications on in-depth results are foreseen in the (near) future.

Jan 1, 2018

By Tracy Shimmield

Deep sea tailings placement (DSTP) techniques have been pioneered in Papua New Guinea (PNG): a mining reliant economy in a seismically active region, facing major environmental challenges in the safe handling and storage of mine tailings on land. Scientists at SAMS have researched impacts of DSTP on the marine environment specifically to inform and develop guidelines for the use of DSTP to reduce environmental impact, thereby lowering risk and increasing private sector investment. Guidelines have been established as regulation by the PNG Government providing reassurance to private investors, facilitating an increase in mining exports to 60% of total export. Researchers investigated the effects of DSTP at 2 PNG mines: Lihir Gold Mine which has been actively discharging tailings since 1996 and Misima Mine, closed in 2004 after discharging tailings for 15 years, allowing an assessment of the recovery of the marine environment after tailings placement. Research involved investigating ocean currents and mixing, the behaviour of metals and the effect of tailings on benthic communities including the risk of elevated metal contents entering the food chain. The research established a metal ?fingerprint? of tailings compared to natural sediments, which enabled the transport of fine tailings within the deep ocean to be ascertained.

Sep 14, 2011

By Richard H. T. Garnett

On the western continental shelf of southern Africa diamonds derived from onshore sources are concentrated in gravels within drowned terrestrial and marine geomorphological features. First discovered offshore in the late 1950's, they are known to exist for about 1400 km along the Namibian and South African coast in water depths of up to 200 m. Shallow water operations yielded 1.5 Mct during the decade ending 1970 when De Beers acquired a majority of the offshore leases and commenced a 15 year exploration program. Deeper water and the prevailing sea conditions required the development of new, unique, marine mining equipment. The first large scale mining production of 22 kct was achieved by De Beers in 1989 with an output of 22 kct. Annual marine output from all sources now exceeds 0.6 Mct worth some US.$ 170 M, and rising to 0.7-0.8 Mct for 1998. Exploration has also been taking place in the waters of West Africa, Australia, and Indonesia. Exploration is by means of high resolution geophysics followed by sampling using a variety of drills, airlifts and seabed-mounted machines which imitate the eventual mining process. Surveying is now probing depths of 500 m. Smaller scale mining by several junior companies has traditionally involved diving and airlift systems. Increasingly, however, they are adopting different and improved techniques which to date have been employed only by De Beers Marine as contractor to Namdeb. Marine exploration and unit mining costs are high compared to those applicable to alluvial deposits onshore. By 1996 the total development costs incurred by De Beers alone reportedly had exceeded US.$ 500 M. However, the financial rewards are commen-surate because of the higher recovered grades. The operations are not without risk for the total of nearly 10 large and medium scale production vessels deployed by various organisations. The greatest shortfalls are experienced in the estimated throughput, not the grade.

Jan 1, 1998

By U. Schwarz-Schampera, C. Rühlemann, H. -R. Kudrass

Within 2006 BGR will conclude a contract with the UN International Seabed Authority (ISA) for the exploration of polymetallic nodules. The contract covers an area in the Pacific nodule belt between the Clarion and Clipperton fracture zones, that which is about 75.000 km2 in size at water depths between 4200 and 5000 m (see Fig. 1). Up to now, 7 consortia or state parties have acquired similar exploration “licenses” for polymetallic nodules in the central Pacific Ocean and the Indian Ocean. These licenses of the UN authority are required according to the UN convention on the law of the sea (UNCLOS) as the areas of interest are located outside of national EEZs. The “licenses” then reserve exclusive rights to the applicant for a time span of about 15 years.

Aug 24, 2006

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 Richard Petters

Williamson and Associates, Inc of Seattle, Washington has recently built a remotely operated seafloor coring system for Nichiyu Giken Kogyo Ltd and the Metal Mining Agency of Japan (MMAJ). The system is designed to core to depths of 20 meters in 6,000 meters of water and will be operated from MMAJ's research vessel Hakurei-Maru No. 2 The corer uses rotary rod coring methods and will recover a core diameter of 44 mm. To facilitate coring through soft or unstable formations, the corer has the ability to set casing. The corer is fitted with thrusters for positioning during landing and telescoping legs for leveling. The system is operated through a 12 km electro-optical cable. Data displayed to the operator provides the operator with real-time feed back and control over the coring process. The operator has independent proportional control over bit weight, advance rate, rotary speed, and flushing water flow. The process of making up, breaking down and storing the drill string is automated and is controlled by a logic driven software routine. The system is currently undergoing trials in Japan. This presentation will discuss the drill's capabilities and should be of interest to those in need of a tool for assessing the thickness of marine mineral deposits.

Jan 1, 1996

By G. Cherkashov

The geodiversity of seafloor massive sulfides (SMS) deposits at the slow- and ultra-slow spreading ridges is of great variety (Fouquet et al., 2010). Tectonics and magmatism are the two principal factors which control SMS formation and localization. The geological setting of SMS deposits is determined by their position relative to the rift valley and by the types of rocks hosted (Table 1). Depending on the first parameter, SMS deposits could be localized at [ ] the axial volcanic ridge or at the flank of the rift valley. Basalts, deep-seated gabbro, and serpentinized peridotites are distinguished among the hosted rocks. The outcrops of deep-seated rocks are exposed at the flanks of the rift valley. The tectonic mechanism of the lower crust and mantle rocks exhumation process is connected with very large offsets along the detachment faults, resulting in a forming oceanic core complex (OCC) (Smith et al., 2006; MacLeod et al., 2009). The SMS related to OCCs are represented by such ore clusters as Ashadze, Logatchev, Semyenov, and some others (Table 1) and are increasing steadily in number. This fact in combination with widespread OCC formation at the slow-spreading ridges (Escartin et al., 2008) and high grades of metals in SMS related to OCCs has provoked considerable scientific and economic interest in these types of deposits. It could be mentioned in this regard that the first two applications to the International Seabed Authority for prospecting and exploration of sulfides have been submitted for the areas in the spreading centres with wide distribution of the core complexes.

Jan 1, 2011

By Thomas Pichler

In the past marine mining technology has focused on bulk mining of base metals from polymetallic massive sulfides. This has not been very successful because of the relatively low unit value of these metals and other reasons such as water depth, etc.. The process of gold enrichment in hydrothermal deposits is controlled through five different factors: (1) nature and source of the solution, (2) source of the gold, (3) a mechanism for mobilizing and transporting, (4) a mechanism for deposition, and (5) a mechanism to preserve the deposit. Gold has been identified in marine polymetallic massive sulfides from various locations on the ocean floor (e.g., spreading centers, seamounts) with contents ranging up to 5 ppm Au. This is within the current range of 1.0 to 7.0 ppm gold content which classifies gold ores. The gold appears to have been derived during hydrothermal alteration of the oceanic crust. Until the present there has been little attention to the possibility of mining gold or other precious metals in the marine environment. However, the magnitude of hydrothermal alteration (seawater can penetrates to a depth of 5 km into the oceanic crust) and primary gold contents of the rocks in the pathway of the fluid indicates that major gold deposits must have formed on or in the ocean floor, but they have not been found. To find a big deposit might only take an exploration model exclusively designed for gold exploration on the ocean floor.

Jan 1, 1993

By G. McMurray

The release by the U.S. Department of the Interior (DOI) of a Draft Environmental Impact Statement (DEIS) for the leasing of polymetallic sulfide minerals on the Gorda Ridge in December 1983 resulted in strong negative public reactions. The fundamental issues affecting federal-state relations included the amount of state involvement in the planning process and the continuing question of consistency (sensu Coastal Zone Management Act). The specific issues raised included the authority of DOI to lease nonenergy minerals offshore, the economic and strategic rationale for the proposed lease, and the adequacy of the DEIS. The questions of DEIS adequacy arose in three major areas: the lack of evidence for the existence of polymetallic sulfides on the Gorda Ridge, the lack of sufficient baseline data, and the lack of a mining scenario from which to assess potential impacts. The joint Federal-State Technical Task Force was formed in February, 1984 as part of an initial agreement between the State of Oregon and the Department of the Interior to work cooperatively. Other points in the agreement were (1) a reduction of any future proposed lease area from 40 million acres to no more than 4 million acres; (2) indefinite postponement of the lease sale; (3) deletion of the nearshore portion of the possible lease area covering the physical continental shelf and slope; (4) a commitment of a "tiered" EIS process; and (5) sharing of non-proprietary data with the public.

Jan 1, 1985

By Alexander Malahoff

Six active Kermadec arc submarine volcanoes located between 34°S and 36°30’S were mapped and sampled by an interdisciplinary inter-institutional research team between April and July 2005 using submersibles Pisces V and Pisces IV aboard the mother ship the R/V Ka’imikai-o-Kanaloa. The purpose of the expedition was to study the relationship between hydrothermal activity, formation of hydrothermal mineral deposits, and the biodiversity of life associated with the hydrothermal vents. Of the volcanoes examined, all showed evidence of hydrothermal activity, including metal-rich plumes and helium anomalies. Only two of the volcanoes, namely Brothers and Clark, showed chimneys and surficial polymetallic sulfide deposition. Hydrothermal venting at a water depth of approximately 1,650 meters near the base of the northwest caldera wall of Brothers volcano has produced a field of chimneys, some of them seven metres high and discharging black smoker venting. Temperatures up to 300°C were measured from the active vents. Clark volcano has a double cone summit at a water depth of 875 meters. The shallowest cone has a near-summit hydrothermal vent field with five-meter tall venting chimneys with smaller structures around the periphery.

Aug 24, 2006

By G. Rehder, C. Hensen, P. Linke, J. Bialas, M. Haeckel, W. Weinrebe, K. Wallmann

Research on marine gas hydrate and the methane cycle has a tradition at IFM-GEOMAR. In summer 1996 during a cruise with RV SONNE offshore Oregon (USA) scientists of the former GEOMAR recovered the largest amount of gas hydrate from the seafloor. This discovery stimulated research on marine gas hydrates in Germany and induced funding of scientific programs such as LOTUS and OMEGA with numerous innovative technologies within the special program GEOTECHNOLOGIEN of BMBF and DFG. The primary objectives of ongoing and future research are to achieve a comprehensive knowledge of: • gas hydrate distribution and quantity; • variation and regulation of gas hydrate formation and dissociation as well as of the related fluid flow; • functioning of chemosynthetic communities in methane oxidation, carbonate precipitation and methanotrophy as biological barrier against methane emission and • delineating the escape routes of methane to the hydrosphere and atmosphere.

Aug 24, 2006

By Fernando J. A. S. Barriga

Exploration for active seafloor hydrothermal vent fields has been highly successful, and more than 300 such fields have been discovered to date. Some will most probably be mined, given their high metal grades (Cu, Zn, Au and others). However, the current practice detects active systems, and activity rates, not the size of the deposits. This strategy may leave undetected some of the best targets, for several reasons as follows: 1. Large hydrothermal plumes are a measure of dispersion of ore components, not of efficiency in the generation of orebodies; 2. Deposits formed a few hundred years (or more) before present will generally have ceased their activity and will not be detected by plume studies; 3. Deposits formed under a cover rock (up to a few meters of sediments, volcaniclastics, or the like) may exhibit only minor seafloor hydrothermal activity, possibly diffuse flow. Cover rocks will often host hanging wall rock alteration, expressed in geochemical and mineralogical haloes. It has been demonstrated in many instances, especially for deposits formed in the geological past, now exposed on land, that ore genesis under a cover rock is one of the most suitable processes for generating large massive sulfide deposits. One of the great challenges for submarine resource knowledge will be to develop adequate exploration strategies for sizeable orebodies, not necessarily hydrothermal vent fields, sometimes hidden under a cover rock.

Jan 1, 2011

By Timothy F. McConachy

Hydrothermal fluids emanating from the seafloor rise as buoyant plumes, entraining ambient bottom sea water on the way up, until they reach density equilibrium and spread laterally in a direction that is governed by near-bottom currents. Plumes provide targets for focussing exploration for seafloor polymetallic sulfide deposits associated with active hydrothermal vents because their lateral and vertical extent is commonly orders of magnitude larger than the vent field from which they originate. Black smokers can inject on the order of 10,000 µg of particles per liter into a sea water column that normally contains only about 10 µg of particles per liter. The resulting plume should be characterized by increased particulate concentration with respect to background sea water and, therefore, provide a measurable gradient towards the source of venting. By utilizing the ability of particles to scatter light, we employed a real¬time, acoustically telemetered, nephelometer to measure this gradient, and mapped the size, shape and particle concentration of plumes at an active spreading center on the Southern Explorer Ridge at lat 49°45.6'N and long 130°16.2'W. Isopach and particle concentration data indicate the presence of two separate but overlapping plumes. The first is associated with a known vent field called Magic Mountain; the second with a new field called AGOR 171, 1.2

Jan 1, 1986

By U. Schwarz-Schampera, P. Stoffers

The main characteristics of the 2545 km Tonga-Kermadec subduction system are the subduction of the Pacific Plate and its sedimentary cover in the Tonga-Kermadec trench and the extension and rifting of the lithosphere behind the active island arc in the Lau basin - Havre Trough back-arc systems. The subduction of the Louisville Seamount chain at 25.6°S affects the tectonic and volcanic system and separates the island arc into the Tonga arc and the Kermadec arc, respectively. To the west, a Miocene island arc is represented by the Lau-Colville ridge. The crustal extension between the Lau-Colville and the Tonga-Kermadec ridge started at about 6 Ma, and induced their separation and the onset of the southward rifting since about 5 Ma. Characteristics of the Tonga-Kermadec arc system include (i) the fourthfold decrease of the subduction rate from 24 cm/a in northern Tonga to 6 cm/a in the southern Kermadec trench, mainly north of 23.5°S; (ii) the development from fast spreading in the Lau basin (16 cm/a) to slow rifting (2 cm/a) in the southern Havre Trough with the transition from spreading to rifting at 23.5°S; (iii) variations in the composition and the volume of the subducting sediments and rocks (detritus from the Samoan hotspot at the northern Tonga arc; the aseismic Louisville ridge at the southern Tonga arc; increasing terrigenous sediments from New Zealand at the southern Kermadec arc); (iv) a number of active volcanic centers younger than 1 Ma and characterized by significant shallow submarine hydrothermal systems.

Aug 24, 2006

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 Patrick J. C. Ryall

Remotely control led drills capable of being lowered to the sea-floor from ordinary research vessels have been developed over the past two decades. These drills are currently being used in geological survey programmes on the continental shelves (Canada, Japan, Norway, United Kingdom) and for studies of mid-ocean ridges. Generally the drills fall into two categories: 1) those which are powered from the surface and controlled by an operator, and 2) those which are battery powered and follow an automatic programme. Some drills have a television camera mounted on them sending a picture to the surface as an aid to site selection and geological interpretation. Typically the drills are capable of drilling a core 2.5 - 5 cm diameter up to 10 m long. While most of these drills are designed for <1000 m depth, some can drill in water depths of as much as 3500 m.

Jan 1, 1985

By John Halkyard

Deep ocean mining is experiencing a rebirth following many years of low levels of activity. Large scale mining is being projected as just over the horizon. A lot has been made of the advances in deep water oil and gas developments over the last thirty years, and how this technology is directly applicable to ocean mining. The authors present their views on this from a perspective of a legacy of participating in the development of manganese nodule mining systems in the 1970s, followed by thirty years in the deepwater oil & gas arena. While it is true that great advances have been made in subsea technology, the differences between mining and oil and gas recovery should not be diminished. Fundamentally, oil and gas are stored in compact reservoirs under pressure. Any intervention leads to flow of the material up a pipe to the surface. The seabed hard minerals are stuck in place, either adhering to sticky pelagic sediment (nodules) or bonded together as hard rock (massive sulfides). The minerals require complex machinery in order to be extracted, sized, concentrated and lifted to the surface. Once at the surface the ore must be dewatered, de-fined and transferred to shore for processing. The overflow from this dewatered product must return to the sea in an environmentally satisfactory manner. These steps involve technology unique to mining that has to be addressed in a methodical fashion before commercial mining systems can be designed. The presentation will discuss the critical technical challenges of deepsea mining and thoughts on different routes to commercialization. The program will address the critical technical challenges, as perceived by the authors, and steps required to address them. Alternate development programs will be discussed focusing on nodules and sulfide. Keywords: manganese nodules, polymetallic sulfides, ocean mining

Jan 1, 2011

By H. Oda, L. E. Fong, K. K. McBride, B. P. Weiss, F. J. Baudenbacher, A. Usui

Fine-scale dating is a key parameter in characterizing the growth history of hydrogenetic ferromanganese crusts. We once compared several dating methods, micropaleontological (calcareous nanofossil), radiometric (10/9Be), and paleomagnetic (step-wise measured inclination) methods on single samples, but these independent methods were not consistent with each other (Joshima & Usui, 1999). For example, a 4-cm thick crust was dated as 3Ma by the fossil-paleomagnetic combined method, while it dated older than 5.5 Ma by Be-10 dating. This discrepancy suggests a question if the Be-10 radiometric method can give us false ages or growth rates (Usui et al., 2002) because of post-depositional change, diffusion or other reasons. In order to answer the question, we conducted ultra-fine magnetostratigraphy with a SQUID microscope on the same hydrogenetic Mn crust sample. Rock magnetic measurements revealed that the main magnetic mineral is well dispersed single domain grains, which is typical to magnetite but not yet specified (Oda, 2005).

Aug 24, 2006