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By Isobel Yeo, Florent Szitkar, Sven Petersen, Sebastian Graber, Nico Augustin, Marcel Rothenbeck, John Jamieson

"INTRODUCTIONSeafloor massive sulfides (SMS) along mid-ocean ridges are often seen as a possible future contribution to a secure metal supply for global human needs. A growing interest over the past few years resulted in six national exploration licenses and one application pending, covering 10,000 km2 each, that have been brought before the UN International Seabed Authority (ISA) since 2011. Each contractor has to explore these 10,000 km2 within the 15-year runtime of the contract. However, the need to define areas that are not economically interesting is more pressing, as 50% of the 100 license blocks have to be returned to ISA after only eight years - hopefully areas that do not contain large and economically interesting SMS deposits. Current geochemical prospecting technologies, however, have mainly been developed for the search for active hydrothermal systems (e.g. hydrothermal vents and associated black smokers) that can easily be traced through physical and chemical anomalies in the water column (temperature, chemical variations of elements such as Mn, Fe, redox potential, and/or the particle concentration in the water column). Such plume surveys have been a primary tool for exploration of SMS systems, but they only identify active, and therefore mostly young and small hydrothermal systems. In a recent high-resolution AUV survey performed within the EU-FP7 funded project “Blue Mining”, we covered 47 km2 along the TAG segment of the Mid-Atlantic Ridge to test exploration methodology for fast and reliable exploration of larger areas of the seafloor for inactive seafloor massive sulfide occurrences using the autonomous underwater vehicle (AUV) “Abyss”."

Jan 1, 2017

By Dwight D. Trueblood

The Benthic Impact Experiment (BIE) is designed to address the effects of sediment redeposition prior to the commencement of commercial mining. The experiment is being conducted in collaboration with Russian scientists from the Yuzhmorgeologiya Association aboard the R/V YUZHMORGEOLOGIYA. Sediment resuspension and subsequent redeposition during manganese-nodule mining is predicted to be one of the primary impacts on benthic communities living on the abyssal seafloor. The redeposition thicknesses that will cause significant faunal mortality in the deep sea are unknown. Sediment redeposition could adversely affect abyssal benthic communities through entombment, or through starvation caused by food dilution and obstructed feeding. This spring NOAA conducted the main portion of the BIE experiment, blanketing the experimental area with varying thicknesses of sediment using the Deep Sea Sediment Resuspension System (DSSRS). The DSSRS was conceived by NOAA scientists, designed and built by Williamson and Associates, and is the critical piece of equipment used to generate the controlled sediment redeposition environment on the 4800-m deep abyssal plane. The DSSRS consists of an 1800-kg sled, 4.8 m long, 2.4 m wide, and 2.2 m high. The sled was towed and powered using an 8,000-m, 26-mm single conductor cable having a 3,000 VAC capacity. As the sled was towed across the bottom, mud was ingested through two rear-facing, 45-cm wide intakes using two 7.6-horsepower pumps, and discharged 10 to 20 m above the bottom through two 20-cm diameter riser hoses. Each pump was instrumented with optical backscatter sensors providing real-time information about the discharge concentration.

Jan 1, 1992

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 Burrows D. R.

Metal-rich sediments precipitating from hot saline brine pools were first discovered in 1965 in the Red Sea.1-2 The subsequent discovery of high temperature black smokers and associated massive sulphides in 1977 at latitude 21oN on the East Pacific Rise3 came more as a confirmation than a revelation. Formation of massive sulphides through precipitation from circulating sea-water had been predicted by Oftedahl in 19584, and the mechanisms well evaluated in basaltic-hosted Cyprus-type 5 and in Kuroko-type deposits.6,7 Sea-floor exploration from 1977 through the 1980?s in sediment-starved mid-oceanic ridge (MOR) settings had little impact on land-based exploration. This is primarily because: a) MOR spreading centres were recognized as poor analogies to even Cyprus-type basalt-hosted deposits; b) their preservation potential was limited due to rapid oxidation and c) the metallic deposits studied were small and therefore not directly comparable to the far larger ore bodies on land. More recently underwater mineral deposit research has focused in a variety of back-arc environments associated with felsic submarine volcanism, environments more similar to those predicted for the formation of Kuroko-type deposits (e.g. Okinawa Trough, 8 Lau Basin, 9 Manus Basin, 10 Aeolian arc, 11). Most studies, while scientifically interesting, were hampered, in general, by a lack of good descriptive data, a reliance on isolated grab samples, and a lack of sub-surface observations. This research has therefore had only limited direct impact on exploration strategies with the possible exception of research conducted in areas where faulting provided enhanced vertical exposures. 12

Jan 1, 2011

By Stanley R. Riggs

Onslow Bay is a broad, shallow, high-energy shelf system bounded by the Cape Lookout and Frying Pan shoals. It is generally a sediment-starved shelf system dominated by hardbottoms with a scattered and discontinuous veneer of mobile Holocene sediments. Phosphate-rich beds of the Miocene Pungo River Formation crop out in a belt 150 km long and up to 50 km wide across the continental shelf in Onslow Bay, North Carolina. Previous research has demonstrated that a few of these beds contain vast quantities of potentially economic phosphate resources that occur in the surface and shallow subsurface sediments. Onslow Bay contains five phosphate-bearing beds predicted to include up to 20.7 billion tons of in-place phosphate concentrate with total sediment grades ranging up to 22.9% P2O5 and adjusted average concentrate grades of 29.8% P2O5. These phosphates are lithologically and chemically similar to phosphates currently being mined in the nearby Aurora phosphate district in North Carolina. Various lithologies of the Pungo River Formation and associated rock units of Oligocene and Quaternary age crop out on the sea floor to form extensive hardbottom habitats that dominate almost 100% of Onslow Bay. A large proportion of these hardbottoms appear to be sea floor deserts, whereas others are virtual oases with rich associations of benthic organisms. These important differences in benthic community structure appear to be greatly influenced by one or more of the following variables: 1) geologic framework (geologic formation, hardbottom composition, morphology, and spatial orientation relative to dominant currents and waves), 2) texture, movement, and accumulation of surface sediments, and 3) flow rates and chemical composition of discharged submarine groundwater.

Jan 1, 1992

By V. K. Banakar

The occurrence of hydrogenous ferromanganese encrustations (Fe-Mn crusts) on the Cretaceous age Afanasiy-Nikitin Seamounts (ANS) in the eastern Equatorial Indian Ocean (EEIO) was first reported by Banakar et al. (1997, Marine Geology). The major element composition of the samples from the upper flank of the ANS (~1650 m water depth) indicated enrichment of Co up to 0.9 % (Parthiban and Banakar, 1999, Indian Mineralogist). Subsequently a project supported by the Department of Ocean Development to explore the ANS for Co-enriched Fe-Mn crusts was launched in 2002 by the National Institute of Oceanography. Sampling at regular depth intervals along two transects on the slopes of the northern elevated region of the ANS was carried out. The Fe-Mn oxide deposition is evident on almost all types of substrates viz., basalts, conglomerate limestone, fossil corals etc., and the thickness of the oxide layer varies from a patina to 7 cm. The Fe-Mn crust growth is evident only above a water depth of 3200 m, below which semi-lithified carbonate ooze is dominant. The ANS Fe-Mn crusts from all the water depths exhibit Mn/Fe < 1.5 suggesting pure hydrogenetic accumulation of metal-hydroxides. Bulk sample Ce-contents for a few selected depth-representative samples are remarkably high, up to 3700 ppm with an average of ~2500 ppm. The positive Ce-anomaly decreases from ~8 at 1600 m depth to ~1.6 at 3200 m depth, which is in contrast to the modern dissolved oxygen depth-profile in the region. This observation suggests that major time-period of the Fe-Mn crust accretion history is dominated by ambient waters with lower-oxygen at deeper depths than at the intermediate depths. This in turn probably suggests a major reorganization in the deep-intermediate hydrography of the region in the past.

Jan 1, 2005

By Sebastian Ernst Volkmann, Felix Lehnen

"INTRODUCTIONWhile today’s mine planning of land-based ore deposits follows methods, which are well established, mining standards for the deep-sea have not established. Having gained a basic understanding of geological settings, there is still a lack of tools and methods to assess and plan future mining projects in the deep-sea. In the framework of the “Blue Mining” research project (2014-2018) technologies and methods for the exploration and exploitation of deep-sea minerals are developed that will bring deep-sea mining a step closer. The “Blue Mining” project receives funding from the European Commission (EC; Framework Programme 7; GA No. 604500) and addresses all aspects of the value chain in the field of deep-sea mining. The project philosophy is that deep-sea mining is planned and executed in the most responsible manner: Ensuring societal benefits and profitability at acceptable resource utilization and lowest possible environmental footprint (Volkmann 2014).Inspired by the high-tech farming industry, a concept to mine seafloor manganese nodules (SMnN) was developed. Mining is considered to be similar to the potato harvest on land (Figure 1), which involves mining a field partitioned into long, narrow strips (Volkmann and Lehnen 2017). The proposed mining system composes of one mining support vessel (MSV), one or two self-propelled, crawler-type seafloor mining tools SMT(s) and different types of underwater vehicles. The MSV follows the mining route of the SMT(s), picking up the about potato-sized nodules from the seafloor. The ore is pre-processed in situ and is lifted on board of the MSV, where the ore is dewatered and loaded onto bulk carriers for transport to the purchaser. Processing and refining of ore is not subject of “Blue Mining” research."

Jan 1, 2017

By G. Cherkashov

A new hydrothermal field with massive sulfide deposits was discovered in 2004 at 16º 38.4?N, 46º 28.5?W on the Mid-Atlantic Ridge. Hydrothermal signals had already been recorded from bottom waters and sediments in this area during cruise 19 of R/V Professor Logatchev in 2000. This site was revisited during the 24th cruise of R/V Professor Logatchev in February 2004 when samples of massive sulfides were recovered and video records of the deposits made. The basalt hosted hydrothermal field is situated at a depth of 3700-3750 m, 600 m above the inner floor on the eastern slope of the rift valley. Structurally, the new field is located at the intersection of a deep along-axis marginal fault and a transverse sub-latitudinal dislocation. Six sulfide mounds as well as associated metalliferous sediments were mapped (sampled and/or recorded by video profiling) within the hydrothermal site. The largest ore body, 500 x 225 m, in the southern part of the field consists of small blocky talus and relics of sulfide chimneys partly covered by iron oxyhydroxides. The chimneys are 1-5 m high. The southern and western boundaries of the massive sulfide deposit have not yet been delineated. More than 1,100 kg of massive sulfides and stockwork mineralization were sampled at 7 sites by dredge and TV-grab. Everywhere, iron sulfides were the principal minerals present. Pyrite in association with lesser amounts of chalcopyrite occurs in both massive sulfides and stockwork mineralization. Of particular interest is the chalcopyrite-siliceous stockwork where silicified and chalcopyritized basalts are intruded by a network of chalcopyrite veinlets. These zones could be fairly thick and enriched in base metals. Sphalerite was very rare.

Jan 1, 2004

By Felix Lehnen, Peter Kukla, Mirjam Rahn

"Significant uncertainty is associated with predicting future trends in deep-sea mining projects, especially when attempting to assess markets for associated products such as ships and collectors. In order to help European Original Equipment Manufacturers (OEMs) to appraise the future market share of deep-sea mining equipment, a methodology was developed that allows to assess and predict equipment turnover. This study presents a market analysis, which evaluates the scale of the potential market for deep-sea mining equipment for seafloor manganese nodules (SMnN) and seafloor massive sulfides (SMS) based on six key drivers: (i) the worldwide deposit potential of SMnN and SMS deposits, (ii) the profitability of deep-sea mining projects, (iii) the metal market of seven associated metals (Cu, Zn, Au, Ag, Co, Ni, Mn), (iv) the current legal and environmental situation in the Area, (v) investment and maintenance costs, and (vi) a competitor analysis.Figures for the different key drivers are based on public reports and expert interviews. Large uncertainties as well as contrasting views and expectations resulted in different options (scenarios) for the future development of the deep-sea mining market. Several scenarios were developed and based on the future number of “mining projects” in the short-term (2022-2041) and the long-term (2042-2061). The number of such mining projects has been calculated based on the combined analysis of the different key drivers.In the scope of this study, the definition of a “mining project” is a deep-sea mining operation for SMnN or SMS lasting for 20 years. This operation includes the purchase of a set of deep-sea mining equipment consisting of a mining support vessel, a vertical transport system and the seafloor mining equipment, in line with other work within the EU FP7 project “Blue Mining” (GA No. 604500)."

Jan 1, 2017

By D. S. Cronan

Studies on polymetallic manganese nodules and Co-rich crusts in the EEZ&apos;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 Fernando JAS Barriga

The world-class Neves-Corvo deposits were intersected by drilling in 1977. They occur in the (Carboniferous) Iberian Pyrite Belt (IPB), Western Europe&apos;s largest stock of base metals (see Bamga, 1990, in Dallmeyer RD, & Martinez E, eds, Pre-Mesozoic Geology of Iberia, Springer-Verlag). Massive and stringer sulfides in the area sum up to about 200 Mt (109 kg), in five main orebodies (Neves, Corvo, Graca, Zambujal and Lombador). They include unique, extremely high grade copper and tin ores ( - 33 Mt Cu ores, -7.5% Cu, and -4 Mt Sn ores, -2.6% Sn, - 12.5% Cu). Also present are -50 Mt polimetallic ores (-6% Zn, 1.2% Pb, 64 ppm Ag). The remaining are relatively low grade pyritic massive and stringer sulfides (Cu < 2%. Sn < 1%, Zn equivalent < 4%). The geological setting is one of bymodal submarine volcanism, with predominant felsic, explosive volcanism and associated sedimentation (detrital and chemical), which took place on a shelf-facies, quartzite-phyllite basement (of Upper Devonian age). The plate tectonic setting has been the object of much debate. Current interpretations favour that the IPB volcanism took place in a tensional fore-arc region, associated with oblique subduction and collision (Silva et al., 1990, same volume as above). At Neves-Corvo there are many different ores, that may be grouped in four main types: fissural (at the base), breccia, massive (intermediate) and "ruban6 " (at the top). Fissural ores seem to correspond to stockworks in contrasting types of host rocks (gray to black shale, sericitic, chloritic and graphitic, and light gray volcanic rock). Massive ore may contain significant shaly gangue, at the base of individual orebodies, and silica-rich (cherty) varieties towards the top. The more sulfide-rich varieties predominate, and are usually well banded.

Jan 1, 1993

By J. Bruce Gemmell

ODP Leg 158 drilled seventeen holes into the active TAG hydrothermal mound and underlying stockwork, 26°N, Mid-Atlantic Ridge. Drilling in five different areas, including a high-temperature black smoker complex and a lower-temperature white smoker vent field, revealed the multi-stage depositional history and character of sub-seafloor mineralization and alteration. The upper portion of the mound consist of massive pyrite and pyrite breccias which are underlain by pyrite-anhydrite breccias and then by quartz-pyrite breccias. Quartz-pyrite breccias grade down into silicified wallrock breccias. Chloritised basalt breccias occur at depths greater than 100 m. Several stages of quartz-pyrite±chalcopyrite veins occur in the stockwork zone and lower portions of the mound, whereas anhydrite±pyrite±chalcopyrite veins occur within the upper parts of the mound. Recovery of unaltered basalt near the edges of the mound has constrained the extent of the stockwork zone to a pipe-like feature 80 meters in diameter. A detailed sulfur isotope investigation of sulfides and sulfates within mound and the underlying stockwork zone has revealed the overall range of sulfide d34S analyses to be 0.35% to 10.27%. Anhydrite has a tight range of d34S values 20.55% to 21.56%. There are distinct differences in d34S values between the different textural types of pyrite (massive sulfide, breccia clasts, disseminations associated with alteration, and veins). The massive sulfide and breccia clasts have a similar distribution of d34S values (6%-8%), however the d34S values of the disseminated pyrite associated with the alteration are distinctly heavier (8%-10%). Vein sulfides have the lightest d34S values (5%-7%). Sulphur-isotope values at TAG are, in general, the heaviest reported for unsedimented mid-ocean ridge deposits.

Jan 1, 1998

By John C. Wiltshire

Hawai&apos;i is surrounded by a series of potentially valuable marine mineral deposits. These include manganese nodules between Hawai&apos;i and Mexico, cobalt-rich manganese crusts and phosphorites in the Exclusive Economic Zone around the Hawaiian Island Archipelago, Johnston Island and the neigh- boring island states and sand and gravel deposits off the main Hawaiian Islands largely in State waters. Hawai&apos;i has an economy that is very narrowly based on the tourist industry. In an effort to avoid the difficulties coming from such a vulnerable economy, significant efforts have been made toward economic diversification. The State has set up a range of programs looking to find new industries. New ocean industries figure prominently among these efforts as Hawai&apos;i is surrounded by ocean. Naturally, among new ocean industries the potential for new marine mineral industries is significant given that Honolulu is the only full service port in the Central Pacific and Hawai&apos;i is in the middle of the mineral belt. The port of Honolulu is now being actively used by mineral exploration vessels of several countries and with the current number of ship visits varying from 10-15 per year, this puts several million dollars a year into the State economy. It helps to fulfill the State&apos;s goal of dynamic growth in the ocean sector of the economy. Nonetheless, a major marine minerals industry, particularly one which would involve processing of minerals in Hawai&apos;i, is controversial in a State whose main source of revenue is tourist expenditures based on the image of a pristine environment. In addition to the perceived threat to the hotel and fishing industry, is the whole highly emotional debate concerning preservation and development. To complicate the issue further, the major interest in developing a marine minerals is currently largely from Korea and China rather than from domestic U.S. industry. On the other side of the debate is the fact that the State&apos;s economy is hampered by many low paying jobs and a lack of technical jobs. This is further exacerbated by the fact that lower paying jobs are held disproportionately by people of Hawaiian and Pacific Island ancestry. Naturally, this leads over time to a certain amount of resentment. The higher paying technical lobs associated with a minerals processing industry could help to alleviate this problem.

Jan 1, 1996

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&apos;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 Mark Lee, Isobel Yeo, Sarah Howarth, Christian Millo, Javier González Sanz, Paul Lusty, Bramley Murton, Pierre Josso

"Seafloor cobalt-rich ferromanganese crusts represent the most important yet least explored resource of ‘E-tech’ elements on the planet (Hein et al. 2003; ISA, 2008; Hein et al. 2010; Hein et al. 2013). These polymetallic deposits form a continuum from nodules rich in manganese and cobalt to crusts rich in tellurium and the heavy rare earth elements (HREE). It is this combination of traditional (base) metals and the extreme enrichment of ‘E-tech’ elements that makes seafloor ferromanganese oxide deposits particularly interesting to both science and society. Recent estimates of the global resource, based on the sparse data available, infers a dry mass of ferromanganese crusts on the seafloor of 35 x 109 tonnes (35GT). Of this, 3.7 GT is predicted in the Indian Ocean, 8 GT in the Atlantic, and 23 GT in the Pacific (Hein et al. 2013).At a global scale, the processes controlling the formation and distribution of ferromanganese (Fe-Mn) crusts are reasonably well understood (e.g. Hein et al. 2000; Verlaan et al. 2004; Cronan 2006; Halbach et al. 1989; Usui and Someya, 1997; Hein et al. 2000; Hein et al. 2003; Hein et al. 2009; Hein et al. 2010; Hein et al. 2013; Muiños et al. 2013; Marino et al., 2016). However, much of this knowledge is drawn from sparse sampling at a regional to ocean basin scale. As a result, there remains a fundamental gap in understanding of the role of local-scale factors, such as micro-topography, ocean currents and upwelling, sedimentation rates, micro-organisms, water mass composition and biological productivity, that are considered potentially crucial to controlling the growth and composition of Fe-Mn crusts. Indeed, quantitative, particularly temporal, information relating to these processes and their relative importance in deposit formation is almost completely absent. Hence, to make any significant advance in understanding these deposits require significant new research."

Jan 1, 2017

By Ulrich Von Stackelber

Deep sea mining of manganese nodules actually will have an environmental impact to the seafloor and to the water column. However, we are far from being able to predict the possible consequences. Therefore, in 1992 environmental studies were conducted with the R/V Sonne in a manganese nodule field of the Peru Basin. The bathymetry of the seafloor was mapped using the hydrosweep system and the distribution and type of sediments were investigated by the parasound system and by collecting surface samples and sediment cores. Deep towing of a side-scan sonar system revealed a Mn encrustation of sediments and a nodule coverage of variable density. Along the tracks of a photo sledge a great variability of bottom fauna and of bioturbation was observed. Bottom-mechanical investigations of surface-near sediments were completed on board. Additionally water samples were collected near the sea floor to determine character and amount of dissolved and suspended particles. Manganese nodules and crusts were collected at 80 locations. In many aspects the nodules differ from those of the Clarion-Clipperton Zone: Big cauliflower-shaped nodules with growth rates up to 160 mm/ Ma may reach a maximum size of 24 cm in diameter, maximum abundance may be 44 kg/m2, the mean size of buried nodules is greater than that of surface nodules. The reason for that difference is due to the relatively high bioproductivity in surface waters and to a Mn redox boundary in the sediment column 10 cm below the seafloor. Histograms of nodules showing the distribution of size and growth type clearly indicate that the growth history is different for basins, slopes and tops of seamounts and ridges. Nodules with diameters >7 cm show mainly diagenetic and to a minor degree hydrogenetic growth. Smaller nodules of the same assemblage are composed mainly of hydrogenetically grown Mn oxide. The optimum diagenetic growth occurs within the sediment immediately above the Mn redox boundary, a level which is not reached by the small nodules.

Jan 1, 1994

By Akira Usui

The details in small-scale variability of the geological occurrence and chemical composition of ferromanganese crusts are not yet well understood, although the northwestern Pacific seamounts are believed to be among the most promising areas for rare metal resources. Our belief is that geological observations and geochemical analyses are still insufficient for economic evaluation or for discussion of depositional processes and environments. Our team, composed of geologists, mineralogists, geochemists, physical engineers, and microbiologists has attempted to utilize an ROV for in-situ measurement and for sampling of undisturbed and uncontaminated ferromanganese crusts at three typical seamounts in the NW Pacific near the Japanese Exclusive Economic Zone. The first ROV geological survey of ferromanganese crusts was successfully completed, and the ROV proved to be the most powerful, efficient and elegant method to date. The collected samples (more than total 1 ton of crusts, at more than 100 sites along a total of approximately 10 km of survey lines) were most suitable to analyze water-depth dependency and secular variation of their composition. The intact surfaces of crusts, collected without the usual abrasion caused by dredging, were also valuable for microbial study of Mn oxidizing bacteria. The ROV sampling devices, however, can be improved with further sophisticated drills or rock saw blades in the future.

Jan 1, 2011

By Mark D. Hannington

Results of the R/V Sonne Cruise (Edison) to the Tabar-Feni Arc from March 11 to April 5, 1994, a joint German-Canadian research cruise aboard the vessel R/V Sonne, undertook detailed mapping of the Tabar-Feni island chain, Papua New Guinea. The Tabar-Feni chain is host to several large porphyry stocks and epithermal gold deposits, including the giant Ladolam gold deposit on the island of Lihir (minimum 19 million oz. Au). The principal objective of the cruise was to map the seafloor in the vicinity of recently active alkaline volcanic islands in the Tabar-Feni chain and to characterize the tectonic setting of large high-level porphyry and epithermal gold deposits in the region. Additional work was carried out on shallow-water hot springs associated with mineralized geothermal systems on the volcanic islands. Complete sets of 1:50,000 scale (20-m contour) maps of the seafloor were produced for each of the four island groups (Feni, Tanga, Lihir, Tabar). The Lihir group was the most active and the most interesting. At least 4 (and probably 6 or 7), previously unknown volcanic cones were discovered within about 10 miles south of Lihir. The volcanoes are clearly very young and appear to have erupted along extensional faults produced by regional plate rotation. This recent volcanic activity appears to reflect recent forearc extension and represents the southward propagation of volcanic activity towards New Ireland. One volcanic cone at 1,490 m water depth is hydrothermally active, with very large areas of diffuse venting (100-200 m across), densely populated by beds of giant clams (probably calyptogena). Other vent-specific fauna are also present, including crabs, snails, sulfide worms, scale worms, limpettes, etc. The clam beds sit on a crust of hydrothermally baked and indurated, sulfidic, hyaloclastite-rich muds. The mineralization consists mainly of fine-grained disseminated pyrite and amorphous Fe-sulfides. A second, much larger cone at a depth of 1,070 m is capped by massive vesicular lavas which are intensely fractured and mineralized. Abundant sulfides and amorphous silica occur in stockwork-like veins which

Jan 1, 1994

By Tobias Hens, Andrew Frierdich, Barbara Etschmann, Joël Brugger, Barrie Bolton

"Ferromanganese (Fe-Mn) nodules and crusts are prime targets for future deep-sea mining ventures due to their unusual enrichment of critical metals, such as Ni, Co, Cu, Ti, Te, Zr, Hf, Nb, Y, and REE. These metals are used in an ever increasing variety of high- and green-tech applications such as alloys, batteries for hybrid cars, fiber-optic cables, or liquid-crystal displays.1 Recovery and processing of these deposits will most likely be cost-intensive and require new solutions.2 Thus, innovative approaches towards the development of sustainable metallurgical processes represent one component that can positively affect the marine mining value chain. Dynamic mineral recrystallization of Fe- Mn oxide phases is a geochemical process that may have notable potential for future hydrometallurgical applications.Our research focuses on Mn oxides – potent trace metal scavengers with high sorptive capacity3 – and biogeochemical mechanisms that control Fe-Mn nodule and crust formation, alteration, and trace element enrichment. Biogeochemical redox cycling of Mn is characterized by microbial oxidation of aqueous Mn(II) to Mn(III,IV) oxides and (a)biotic reduction of these oxides to Mn(II)aq. During this cycling dissolved Mn(II) is in direct contact with solid-phase Mn(III,IV) oxides and can back-react via abiotic pathways (e.g., 4 and references therein). This results in continuous dynamic recrystallization of the Mn mineral substrate through coupled dissolution (trace metal release) – reprecipitation (trace metal incorporation) processes.4 We recently demonstrated in new experiments, that Ni is cycled during manganite recrystallization. It has been shown that, although Ni readily undergoes mineral-fluid repartitioning in the absence of Mn(II)aq, dissolved Mn(II) significantly catalyzes Ni exchange between solid phase and solution. Over a period of 50 days about 30 percent of the Ni atoms in Ni-substituted manganite (natural abundance composition) were exchanged with a 62Ni(II)aq isotope tracer at pH 7.5. Based on these outcomes we employed similar techniques to investigate the impact of dynamic recrystallization on Mn oxide phases in deep-sea ferromanganese nodules and crusts from three circum-Australian locations (South Tasman Rise, Lord Howe Rise, Coral Sea) and the Central Pacific Basin."

Jan 1, 2017

By Cornel E. J. de Ronde

Volcanic arcs, including both island arc and intra-oceanic arc systems, combined extend for ~22,000 km around the Earth, with the majority (~20,000 km) occurring in the Pacific basin. These arcs are host to over 700 volcanoes of which ~200 are submarine and as such represent great potential for hosting massive sulfide deposits formed at seafloor hydrothermal vent sites. The Kermadec arc extends for ~1,200 km northeastwards from the North Island of New Zealand and forms the southern part of the ~2,500-km-long Tonga-Kermadec intra-oceanic arc system. At least 94 volcanoes are known to exist along this system with 74, or about 80%, being submarine. At least 33 volcanoes occur along the Kermadec part of the arc with all but one (Raoul Island) being submarine. The first sulphides recovered from the entire Tonga-Kermadec arc were in 1996 from the Brothers and Rumble II West volcanoes of the southern Kermadec arc. The 1998 R/V Sonne research cruise recovered a more comprehensive suite of mineralised samples from Brothers, and also found evidence for hydrothermal venting at Monowai, Vulkanolog, Rumble III and Clark volcanoes. The March 1999 NZAPLUME cruise systematically surveyed 260 km of the southern Kermadec arc and found that 7 of 13 volcanoes were hydrothermally active, with the vent fields either located within calderas (e.g., Brothers, Healy, Rumble II West) or atop volcanic cones (e.g., Clark, Tangaroa, Rumble V, Rumble III). The May 2002 NZAPLUME II cruise surveyed a further ~580 km of the mid-segment of the Kermadec arc, from Brothers to volcano &apos;L&apos;, a submarine volcanic edifice 35 km NW of Macauley Island. This cruise surveyed 13 major volcanoes and 8 smaller volcanic edifices and confirmed hydrothermal venting at the Vulkanolog site, and discovered new vent fields atop a volcanic cone within Macauley caldera, immediately offshore Macauley Island, and another at the summit of volcano &apos;L&apos;. A further new site was found atop a volcanic knoll immediately S of Healy caldera during time-series sampling of the vent sites found during the 1999 cruise. All the vent sites discovered along the Kermadec arc occur in water depths between 1650 and 150 m.

Jan 1, 2002