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By Jelena Milinovic, Sofia Martins, Anna Lichtschlag, Sven Petersen, Fernando J. A. S. Barriga, Bramley Murton, Adeline Dutrieux

"The active TAG hydrothermal mound is one of the largest and better studied. Due to its size (one of the largest, known so far, in the Atlantic Ocean) and concentration of specific economic valuable elements, it might be considered for future exploitation due the increasing demand for raw materials. However, the discovery of several large inactive sulfide mounds, some partially buried under sediments may relieve this pressure. Exploration for such occurrences can, together with geophysical exploration tools, be accomplished by mineralogical and geochemical studies of those sediments.INTRODUCTION AND GEOLOGICAL SETTINGThis study reports the results from sediment samples collected during the Meteor M127 cruise on the TAG hydrothermal area in 2016. The Trans-Atlantic Geotraverse (TAG) hydrothermal field (Mid-Atlantic Ridge, 26°08’N) is located 2.4 km east of the main rift valley at depths of about 3650 m. The TAG hydrothermal field stands as an example of a massive sulfide deposit on a low-spreading ridge associated with an active detachment fault (Humphris et al., 2015).Associated with the TAG hydrothermal field are metalliferous sediments/deposits that can reach several meters in thickness (Metz et al., 1988). These sediments/deposits can be formed by hydrothermal plume fall out (buoyant and nonbuoyant), massive wasting of hydrothermal edifices (sulfide mounds and chimneys) and authigenic mineralization (Gurvich, 2006). By studying the grain size, mineralogy and geochemistry of the sediments it is possible to identify each type of sediments and find their proximal or distal distribution. The location of the gravity cores studied here is distributed along sediment ponds near inactive hydrothermal mounds [Three mounds area (B)], actively venting low-temperature mound [Shimmering mound (A) and Mir zone (D)] and an area of sediment accumulation [Central area (C)] (Rona et al., 1993) (see Figure 1)."

Jan 1, 2017

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 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 Jorge MRS Relvas

Recent research both on active and fossil systems has demonstrated that shallow subseafloor replacement processes are not only viable depositional mechanisms for massive sulfide mineralization, but likely contributed as a major component of the mineralization occurring in large VHMS deposits and in many present-day seafloor hydrothermal systems. In the giant Neves Corvo deposit, as in many others VHMS deposits of the Iberian Pyrite Belt, there is overwhelming evidence for silicate-sulfide replacement processes being largely responsible for the efficiency of the ore-forming systems and huge size of the deposits. Textural evidences at all scales, coupled with a well-constrained mass-balance geochemical analysis, indicate that extensive replacement in the lavadominated volcanic rocks of the footwall sequence, and disseminated replacement mineralization in the volcaniclastic and/or sedimentary units were major mechanisms of ore formation in the Neves Corvo deposit. Shallow metal deposition prior to fluid discharge on the seafloor is likely to play a major role in seafloor massive sulfide mineralization. This premise should be envisaged as critical in evaluating the economic potential of seafloor resources, and should certainly be part of the equation when plans for seafloor mineral exploration missions are drawn.

Sep 14, 2011

By Carsten Rühlemann

Between 2008 and 2013, the German Federal Institute for Geosciences and Natural Resources (BGR) carried out five exploration cruises to the German license area in the eastern Pacific Nodule Belt. The first two expeditions were mainly dedicated to multibeam mapping to obtain an overview of the seafloor topography and acoustic backscatter strength. These data were used to identify ten to fourteen prospective nodule fields for potential future mining, which together cover about 16% of the total license area of 75,000 km2. During the last three cruises, three of these potential mining areas were explored in detail. For this purpose, the BGR developed a suite of exploration methods to map nodule size distributions and nodule abundances. These methods include acoustic surveys with vessel-based multibeam systems as well as near-bottom video mapping complemented by in situ sampling. The economically most valuable field has a size of ca. 2,000 km2, of which 34% is covered by medium to large nodules (> 4 cm long axis of nodules) with an average abundance of 22.4 kg/m2 and 44% is covered by small nodules (< 4 cm) with a mean abundance of 17.5 kg/m2. The total mass of nodules in this field comprises more than 30 million tons wet weight and could sustain deep-sea mining for at least 10 years.

Sep 14, 2011

By Timothy F. McConachy

Between April 2000 and April 2002, the Commonwealth Scientific and Industrial Research Organization (CSIRO) Division of Exploration and Mining has led 6 research expeditions totalling 160 days ship time in waters of Papua New Guinea, Vanuatu, Solomon Islands, Indonesia and Australia. Five expeditions were undertaken aboard the Australian research vessel Franklin following successful competitive research proposals, and the sixth used the Indonesian vessel Baruna Jaya VIII (see Table 1). In addition, two CSIRO participants joined JOIDES Resolution for the Ocean Drilling Program Leg 193 in the Manus Basin of PNG. The major scientific objective underpinning these expeditions was to locate and study present-day seafloor and sub-seafloor hydrothermal ore-forming activity in order to develop improved methods of exploring for ancient mineral deposits on land that originally formed by similar processes. The research has been supported financially by a number of Australian-based mineral companies, by Australian international aid agencies, and by appropriation funds from CSIRO, and was conducted in collaboration with researchers from Australia, Indonesia, Portugal, New Zealand, United States of America, South Korea, and the host nations. Building upon earlier successes in the 1986-1997 PACLARK-PACMANUS programs in the Woodlark and Manus Basins of PNG, we have sought to examine a wider range of geological settings in which ancient orebodies are inferred to have formed, including both volcanic and sediment-hosted environments. We have now visited volcanic arcs, fore-arc and triple-junction related submarine volcanoes, and back arc basins associated with convergent plate margins in the SW Pacific and SE Asia, as well as conceptual Mississippi-Valley-type targets associated with warm seeps at passive margins in the Great Australian Bight (see Figure 1). Surveys ranged from northern Sulawesi via far western Bismarck volcanic arc near PNG-Indonesia border, through the eastern Manus Basin and the Tabar-Lihir-Tanga-Feni chain in PNG, the western Solomon Islands festoon, the San Cristobal arc, parts of the Vitiaz arc, to the northern and southern New Hebrides arc in the Solomons and Vanuatu.

Jan 1, 2002

By Sven Petersen, Berit Lehrmann, Bramley J. Murton, Paul A. J. Lusty

"INTRODUCTIONToday’s metal mining focusses on land based ore deposits which only consider one third of the Earth’s surface. Through an increasing global demand of strategic metals used in the electronic and green industry (Zepf et al. 2014), ‘uneconomic’ sites of lower grade in more technical challenging grounds such as greater depth and/or more remote areas are developed by the mining industry often resulting in higher environmental impact. However, considering the steady growth of the Earth population a shortage of certain metals may occur (Krausmann et al. 2009). In 2010, the United Nations allowed commercial exploration for seafloor massive sulphides (SMS) in international waters with currently six contractor licenses being granted.Although the number of discovered vent sites has steadily increased since the first discovery of hydrothermal venting at the Galapagos Rift in 1977 (Corliss et al. 1979) with more than 600 sites being known today, their economic potential is poorly constrained. So far Nautilus Minerals Inc., a Canadian mining company, is the only company having conducted a NI 43-101 resource estimate for the Solwara site, located in the territorial waters of Papua New Guinea. Other studies using bulk geochemical data from 95 sites published in literature do exist (Hannington et al. 2011, Monecke et al. 2016) suggesting a global resource potential for today’s known SMS deposits of 600 million tons with a median grade of 3 wt.-% copper, 9 wt.-% zinc, 2 g/t gold and 100 g/t silver. However, the geochemical data being used originated mainly from easily recoverable, mainly non insitu surface grab-samples and are under current mineral resource classification schemes such as JORC code or NI 43-101 not even accepted for resource estimations. Furthermore surface samples such as high-temperature sulphide chimney and talus material are not representative for the entire deposits with information regards thickness and continuity of individual sulphide layers obtained through drilling being scarce. In addition, it remains unknown what geological processes occur once hydrothermal activity ceases and whether metal tenor becomes enriched, depleted or disappears."

Jan 1, 2017

By Jan M. Peter

The Early Norian Windy Craggy massive sulfide deposit is within the allochthonous Alexander terrane of the Insular tectonic belt in extreme northwestern British Columbia (Figure 1). Host rocks are the Middle Tats Volcanics, part of an informally-named volcano-sedimentary succession of mixed graphitic argillites and mafic pillowed and massive volcanic flows and sills of Upper Triassic age (Figure 2) that have suffered only lower greeschist-facies metamorphism. The volcanic rocks are light rare earth element (LREE)-enriched and display a variably developed back-arc subduction signature. Major and trace element compositions of the host argillite show that it contains an appreciable hydrothermal component, as evidenced by low high Fe and Mn contents. These sediments therefore record steady, continuous hydrothermal activity punctuated by intermittent turbidity currents sweeping into the basin. The deposit consists of at least two discrete sulfide lenses (the North and South Sulfide Bodies), as shown in Figure 3, a level plan at the elevation of the exploration workings. Published reserves at 0.5% copper cut-off are 297.4 million tonnes grading 1.38% Cu, 0.08% Co, 0.21 g/t Au and 3.9 g/t Ag (as of December 1991). However, the deposit is larger than this and further drilling is required to delineate it completely. Mineralization comprises massive sulfide, stringer/stockwork, and finely bedded to laminated sulfides and exhalites. Stockwork mineralization consists of sulfide-quartz-chlorite veins with attendant chlorite and silica alteration. Mineralization consists predominantly of massive pyrrhotite andlor pyrite with lesser chalcopyrite and magnetite. Figure 4 is an oblique section through the North Sulfide Body, the most northerly sulfide mass shown in Figure 3, which shows the distribution of the pyrite and pynhotite-rich massive mineralization and the stringer zone. The North Sulfide Body contains appreciable sphalerite, whereas the South Sulfide Body contains only trace amounts. Gangue minerals include quartz, chlorite, calcite, siderite, ankerite, stilpnomelane and magnetite. The minor hydrothermal exhalite sediments are comprised of chert, carbonate, and minor

Jan 1, 1993

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 Charles L. Morgan

"In 2012 the International Seabed Authority (ISA) established nine “Areas of Particular Environmental Interest” (APEIs) for consideration as future Marine Protected Areas to help preserve the biodiversity of life on the seabed within the Clarion-Clipperton Zone (CCZ) between Baja California, Mexico, and the Hawaiian Islands. The CCZ is believed to have a high potential for future seabed mining operations. Areas under active exploration contracts in the CCZ, plus the areas currently reserved by the ISA for exploration by developing nations, comprise about 1.9 million km2 of seabed area. The currently designated APEIs consist of more than 1.4 million km2 of seabed. Each APEI includes a central primary conservation area of 200 X 200 km, surrounded by 100-km buffer areas on all sides. The 100-km buffers are intended as a very conservative spacing between the primary conservation area and potential mining activities in adjacent seabed. The selection of these nine 400 X 400 km APEIs, has been criticized as possibly not including sufficient representative habitat similar enough to the potential mining areas (identified currently as the exploration contract and reserved areas administered by the ISA within the region) to ensure protection of the biodiversity that might be impacted by mining.An area to the east of the existing exploration contracts and reserved areas is known to have substantial mineral deposits; it is very similar to the adjacent exploration contract areas in its geology, environmental setting, polymetallic nodule abundance and nodule metal content. Because it is located in the northeastern extreme of the CCZ, this area is also likely to have relatively high densities of benthic life, compared with benthic communities further westward within the CCZ. Many options for the designation of this APEI are possible, but the area designation must accommodate the boundaries of the Exclusive Economic Zones of Mexico and France.This paper discusses why the selected region in the eastern extreme of the CCZ is a good candidate for designation as a new APEI.Keywords: polymetallic nodules, Marine Protected Areas, Clarion-Clipperton Zone, Areas of Particular Environmental Interest"

Jan 1, 2017

By Gérald Riverin

Over the past century, exploration methods for volcanogenic massive sulphide deposits have evolved in response to a decreasing number of discoveries made by traditional surface prospecting and by ground and airborne geophysics. Statistical trends support the concept that fewer and fewer outcropping and sub-cropping VMS discoveries will be made in the future. In turn, this creates new opportunities to develop more sophisticated exploration models and techniques to explore at greater depth and to make blind discoveries. Current exploration models include various combinations of geological, geochemical and geophysical criteria which have been based on the results of land-based VMS research. The role of seafloor research in the development of these models has so far been only of a subordinate nature, perhaps due to a lack of direct involvment of the exploration industry in the seafloor research, and vice-versa for the seafloor researchers in VMS exploration. Another contributing factor is that exploration relies on exploration criteria that result from detailed geological, geochemical and geophysical studies of both footwall and hanging wall rocks, studies that are not possible in modern sea floor environments. Nevertheless, seafoor research has contributed to our understanding of the growth of sulphide mounds, the mechanism of sulphide deposition and of the chemistry of fluids involved in VMS systems. In particular, the role of structure and of tectonic setting has been clarified through observation of active seafloor hydrothermal systems. In turn, observations made in land-based VMS research has helped seafloor researchers to focus on key issues which, will eventually contribute to improved exploration models.

Jan 1, 1998

By H. I. Chesalova, M. Ye. Melnikov, A. M. Asavin

The discovery of iron-manganese ores on the surface of underwater mountains was made more than a half century ago. During this time the basic ideas about the thermodynamics of the processes of hydrochemical reactions in the sea water have been developed by scientists and are revealed in geochemical and mineralogical differences between the deposits from the seamounts and the nodules of the sea bottom. The distribution of the dissolved metals, oxygen, carbonic acid and organic matter in the overlying ocean waters of seamounts in the deep ocean to depths more than 5,000 m has been studied in some detail (e.g. J.R. Hein, P. Halbach. G.B. Baturin, Ye.M., S.I. Andreev, L.I. Anikeyeva, [1-6]). In recent years scientists from YUZMORGEOLOGY have completed detailed geological survey work on the Magellan Seamounts in the Pacific Ocean. The results of drilling the ore body and geophysical and photo surveys have also been described [4]. Previous ideas about the general covering of seamount surfaces with iron-manganese crusts have been changed based on ground-truth surveys. This study examines the complex concentric-zone or spotty arrangement of the most densely covered sections, the strong dependence of the thickness of crust on the geomorphologic features, and the potential influence of the underlying substratum. One established geochemical heterogeneity in the composition of ores, also frequently inversely proportional power dependence on directions was observed. The development of a numerical model of the formation of the ore crust on the seamounts is currently a high priority.

Sep 24, 2006

By Natalia Konstantinova, Kira Mizell, James R. Hein, Georgy Cherkashov, Amy Gartman, Pavel Mikhailik

INTRODUCTION Ferromanganese (FeMn) crusts from Mendeleev Ridge, Chukchi Borderland, and Alpha Ridge, in the Amerasia Basin, Arctic Ocean, are similar based on morphology and chemical composition. The crusts are characterized by two- to four-layered stratigraphy. The chemical composition of the Arctic crusts differs significantly from hydrogenetic crusts from the North Pacific Prime Zone (PCZ; Hein et al., 2013), such as a high mean Fe/Mn ratio (2.6 versus 1.3) and low Si/Al ratio (1.8 versus 4.0), with lower Mn, Ca, Ti, P, Ba, Co, Cu, Ni, Pb, Sr, and Zn and higher Si, Al, Mg, As, Li, V, Sc, and Th. Based on Arctic FeMn crust mineralogy, chemical composition, and growth rates, crust formation was dominated by three processes: Precipitation of Fe-Mn (oxyhydr)oxides from ambient ocean water, sorption of metals by the Fe and Mn phases, and fluctuating but large inputs of terrigenous debris (Konstantinova et al., 2017; Hein et al., 2017). The Mn and Fe phases are hydrogenous and reflect bottom ocean-water chemistry and the aluminosilicate phase contains stable detrital minerals such as quartz, feldspars, zircon, monazite, and clay minerals. A precise method of studying the distribution of elements in FeMn crust phases is sequential leaching that dissolves four mineral phases of different stability step-by-step, in the following order: easily leachable phase, mostly bio-calcite; manganese oxides; iron oxyhydroxides; and residual aluminosilicate minerals (Koschinsky and Halbach, 1995). Twelve bulk crusts and crust layer samples obtained from six hydrogenous FeMn crusts were studied. Those crusts were collected during Russian (Arktika 2012) and USA (HLY0805, HLY0905, and HLY1202) research cruises from different parts of the Amerasia Basin (Mendeleev and Alpha Ridges, Chukchi Borderland). Samples were chosen for the sequential leaching experiments based on their morphology, location, and water depth. Hydrogenetic crust (D07-33) from the Tuvalu EEZ, central-west Pacific Ocean, was included in the experiment for comparison. Recovery during the four-step sequential leaching, with respect to the bulk analyses, was between 80% and 120%.

Jan 1, 2018

By Roger Amato

The 1982 United Nations Convention on the Low of the Sea includes provisions under Article 76 for extending a coastal State&apos;s jurisdiction beyond the 200-nautical-mile (nm) Exclusive Economic Zone (EEZ) and for establishing the seaward limits of sovereign rights over natural resources. Article 76 prescribes a set of methodologies for determining these outer limits based on physiography and sediment thickness. The methodologies were applied to each of the five continental* margin areas of the United States - Atlantic, Pacific, Gulf of Mexico, Alaska, and Pacific Islands-using existing digital hydrographic and geologic data. Figures 1 and 2 show the results of applying the methodologies to the Atlantic, Pacific, Alaskan, and Gulf of Mexico continental shelves. Figure 1 depicts the preliminary limits of each of the Article 76 determinations for the Atlantic and Gulf of Mexico continental shelves. The Atlantic limits were described by Carpenter, Thormahlen, and Amato (1995) at the 26th Underwater Mining Institute.1 The limits for the Alaskan continental shelves are shown in Figure 2. Additional areas beyond the 200 nm EEZ are highlighted. These include a small area north of the U.S. - Canada boundary, containing 7,000 km2, a large area north of Point barrow (395,000 km2), and a third area north of the Aleutian Islands (178,000 km2). The shelf between the first two areas appears to have sediments thick enough to qualify for the 1 percent method (Irish Formula); however, year-round ice cover has prevented acquisition of seismic or drill data. The entire northern Alaska shelf is prospective for petroleum The Gulf of Mexico (Figure 1) has two small areas beyond the EEZ known as "doughnut holes." One is south of Louisiana and includes part of the Sigsbee Escarpment, an area believed to have potential for oil and gas. Oil was found on Sigsbee Knoll in cores from Deep Sea Drilling Project&apos;s Leg 1 cruise in 1968. The Sigsbee areas contains about 6,000 km2. The second area is south of the Florida panhandle and contains about 12,000 km2.

Jan 1, 1996

By Sofia Martins, Anna Lichtschlag, Sven Petersen, Fernando Barriga, Bramley Murton, Adeline Dutrieux

"Sediments in the vicinity of the hydrothermal seafloor massive sulphide (SMS) mounds are characterized by high concentration of metallic particles. They result from a long process of weathering of the primary mineral deposits and have been accumulated in depressions by mass wasting and hydrothermal plume fall-out. We present here the first results obtained on pore waters analyses of such sediments in distinct geological seafloor environments (in low-temperature hydrothermally active zones, on extinct hydrothermal mounds and in a remote depositional channel). Vertical concentration profiles suggest that the pore fluid composition is affected more by seawater circulation compared with hydrothermal fluid flow in all environments. The composition of pore fluids is affected by diagenesis and redox processes in the distal depositional channel where Mn2+ is released at depth with Cu2+.IntroductionMarine hydrothermal fields, hosting seafloor massive sulphides, are potential resources for future deep-sea mining and might become economic reserves for the industries. They are widespread at mid-oceanic ridges, arcs and back-arc spreading centers (Hannington et al., 2011; German et al., 2016). Sediments in the vicinity of these fields can contain unusually high concentration of Fe, Mn, Zn and Cu among other metal elements (Shearme et al., 1983). These hydrothermal, or metalliferous, sediments result from a combination of processes such as collapsing and weathering of chimney material, filling of the channels by turbidite-like mass wasting, in situ authigenic mineralization and hydrothermal plume fall-out (Goulding et al., 1998; German et al., 1990). The sediments contain important indicators reflecting the development of the hydrothermal systems. Because of their widespread distribution and metal content, they themselves can be considered potential mineral resources. Circulation of seawater through these deposits, however, often modifies the sediment composition by oxidizing the sulphides into oxyhydroxides and clays causing mobilization of the metals. To address the importance of alteration and diagenesis of these hydrothermal sediments, including the result of seawater circulation, we investigated the post-depositional processes occurring in the hydrothermal sediments at the TAG Hydrothermal Field (Mid-Atlantic Ridge, 26°N), focusing on the mobility of metallic cations in a number of different seafloor environments."

Jan 1, 2017

By John Parianos, Simon Richards

SUMMARY The Clarion Clipperton Zone (CCZ) hosts the most valuable deposit of polymetallic nodules yet discovered. Understanding the geology of this deposit is key to its effective exploration and mining. Nautilus Minerals (via its subsidiary Tonga Offshore Mining Limited; TOML) has been progressing its understanding of the relationship between seafloor morphology/structure and nodule abundance/morphology, both locally (within its contract areas), and globally (across the CCZ and the span of its contract areas of almost 70% of the CCZ). We present the first results of a project with the aim of developing a method to quickly and accurately map seafloor morphology/structure (Tectonic Subcomponent scale) without the necessity for high resolution seafloor multibeam data. Furthermore, the results presented here will allow a first attempt in understanding the relationship between seafloor geomorphologically-defined zones and plate-scale tectonics of the CCZ and adjacent plate segments. INTRODUCTION A relationship between the type of geochemical active layer and nodule abundance/morphology has long been understood (ISA, 2010). Consideration of the range of differing nodule types found within, but especially between, the TOML contract areas allowed Parianos and Pomee (2017) to refine this relationship further via interpreted thickness and dynamism of the geochemically active layer. The scale of the deposit, both in terms of space and time is staggering (a 10-20 cm thick deposit, spanning almost 4500 km, varying within a circa 10 Ma period), but a segment wide geological map may one day prove to reflect controls on nodule formation and distribution.

Jan 1, 2018

By Ian J. Graham

Brothers volcano, in the southern Kermadec Arc, is host to two hydrothermal vent fields with very different geology, permeability, vent fluid compositions and mineralogy (see de Ronde et al. and Ditchburn et al. this volume). The NW caldera site contains mineral deposits (sulfide chimneys and crusts), which are either Cu-rich (?magmatic?) or, more commonly, Zn-rich (?epithermal?). The lower cone site, in contrast, is characterized by native sulfur mounds and spires. It has been proposed (see de Ronde et al. this volume) that the metals, especially Cu and possibly also Au, enter the hydrothermal system via injection and degassing of magma and/or the dissolution of metal-rich glasses. They are then transported rapidly upwards via magmatic volatiles along long (c. 2.5 km), narrow (c. 300 m diameter) pipes, consistent with evidence of vent fluids forming at higher than hydrostatic pressures, at relatively shallow depths. The NW caldera and cone sites may represent stages along a continuum between magmatic-hydrothermal and water/rock-dominated end-members. In this context, investigation of melt inclusions in conjunction with other geochemical and petrological research was carried out to ascertain the metal transporting conditions that may have led to mineral deposition and ore formation. Sixteen melt inclusions in plagioclase were analyzed for their chemical compositions from a typical cone dacite sample using LA-ICPMS at the University of Tasmania. The inclusions are typically glassy and commonly occur with other inclusions such as apatite, clinopyroxene, zircon, magnetite, sulfides and/or low-density fluids (Fig. 1). Major (XRF) and trace element (ICPMS) analyses were performed on whole rock samples collected during the 2005 Shinkai 6500 expedition. Haase et al., (2006) has also reported EPMA glass analyses from cone dacites, which may be used for comparison (Table 1). [ ]

Jan 1, 2010

By Mayumi Ito

Seafloor hydrothermal deposits are found worldwide at 700 to 3,600 meters below sea level [1] and contain base and precious metals like Cu, Pb, Zn, Au, and Ag. Some deposits were found in the Japanese exclusive economic zone and the commercial potential will depend on developments in mining and treatment costs of onshore mines. The ores require mineral processing to become concentrate for the various metal smelters and the authors are investigating mineral processing treatments of collected samples. The collected samples were classified into three components (chimney, mounds, and substrate rocks) and they were separated using a RETAC jig. The mound component contains zinc, lead, and copper minerals and further separation using flotation was investigated. This paper introduces results of the mineral processing tests using gravity separation and flotation.

Jan 1, 2011

By Dilip Sarangdhar

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

Jan 1, 2017

By Gary J. Massoth

Wherever hydrothermal fluids vent from the seafloor they will buoyantly rise (up to 100?s of meters) while mixing with seawater before attaining density equilibrium and dispersing laterally as neutrally buoyant plumes commonly 50 to several 100?s of meters in thickness and with order-of-magnitude or greater breadth. Although these plumes are typically >10,000-fold dilutions of vent fluids they can be reliably detected using sophisticated physical sensing and chemical techniques. Hence, hydrothermal plumes are spatially large targets compared to the actual sites of seafloor fluid discharge and resulting mineralization. For this reason plume prospecting techniques evolved over the past 20+ years have been widely used to systematically explore over 10% of the 60,000-km-long system of mid-ocean ridge (MOR) spreading centers for hydrothermal activity. While plume detection and gradient mapping can be used to home in on venting sites, plume chemical signatures provide additional insight regarding the nature of the fluids being discharged on the seafloor. We have applied the systematic plume prospecting techniques developed on MORs to the volcanic frontal arc setting as part of the NZAPLUME (New Zealand American PLUme Mapping Expedition) surveys. NZAPLUME I in March 1999 marked the first systematic reconnaissance of any intra-oceanic arc for submarine hydrothermal activity. Seven of thirteen previously mapped volcanoes that comprise a 260-km-long section of the southern Kermadec arc northeast of New Zealand were confirmed to be hydrothermally active. On average, one hydrothermally active volcano was found along each 35 km of arc front, a rate comparable to slow- and intermediate-rate spreading MORs. During NZAPLUME II in May 2002, thirteen previously unknown volcanoes and 8 satellite cones were first swath mapped for bathymetric detail and then surveyed using plume prospecting techniques. Three active venting sites were discovered along this 580 km-long arc section, bringing the total to 10, or 39% of 26 volcanoes surveyed overall, still an appreciable frequency rate for venting sites compared to MORs. While only chemical results for NZAPLUME I are available, the arc plumes characterized so far are chemically diverse and rich compared to MOR plumes. This diversity and enrichment was most evident as ultra-high concentrations of CO2, sulfur gases (St = SO2 + H2S), and Fe within plumes over several volcanoes. We suggest the fluids discharging from the seafloor at these sites are volcanic fluids, i.e., hybrid fluids comprised of MOR-like hydrothermal fluids evolved from seawater-rock reaction and fluids exsolved from magma as acid volatiles and liquid brines.

Jan 1, 2002