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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 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

By Raymond A. Binns

Exploration for undersea polymetallic sulfide mineral resources with high economic potential would be more effective given an ability to predict sites with particularly high gold contents (averaging say > 10 ppm Au). Herzig et al (1993) addressed this issue shortly after recognition that deposits in the back-arc Lau Basin (average 3.8 ppm Au) were enriched in gold relative to mid-ocean ridge sites (average 1.2 ppm Au). Small but significant numbers of hydrothermal sites with massive sulfide deposits averaging >10 ppm Au have since been discovered. The principal genetic factors underlying gold enrichment include depositional processes at and below the seabed, and the source of gold. It is timely to consider whether resolution of their relative importance can be translated into practical criteria for exploration strategies focused on especially gold-rich deposits. Comparing the ?grade? of seafloor deposits using analyses cited in research papers is fraught with difficulty, but there is no alternative at present to assuming that such averages provide an initial tenor guide. On this basis, four known polymetallic hydrothermal sites from convergent plate margins fit the exceptional-gold category with >10 ppm ?average? Au, while one from a divergent margin comes close: Sunrise (Myojin Knolls; 20 ppm ?average? Au) and Suiyo Seamount (28 ppm Au) in the Izu-Bonin Arc are frontal arc volcanoes dominated by rhyolite and dacite respectively, contrasting with more common mafic neighbor edifices (Iizasa et al., 1999). In both cases gold-rich massive sulfides occur in summit calderas with significant development of pumiceous volcaniclastic rocks, at depths around 1300 and 1370 m respectively. In the Eastern Manus Basin, PACMANUS (~1700 m; 14 ppm Au) and Suzette (~1550 m; 22 ppm Au) occur along the crests of volcanic ridges dominated by dacite/rhyodacite and andesite/mafic dacite respectively (Binns, 2004). Caldera structures are lacking. Although the Eastern Manus Basin is tectonically a rifted back-arc, its submarine volcanic edifices (picritic basalt to rhyodacite) have distinctly arc-style geochemical and isotopic affinities, differing from more typical back-arc basin basalts at the spreading axis further west (central Manus Basin). Probably as a consequence of transpression and a marked rupture in the New Britain subduction zone, submarine arc volcanism has here extended into the rifted back-arc region.

Jan 1, 2005

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 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 James R. Hein

Manganese nodules from the Cook Islands (CI) Exclusive Economic Zone (EEZ) are compositionally different from other nodule fields. CI nodules have relatively high cobalt concentrations and low nickel, copper, and manganese concentrations (e.g. Hein and Petersen, 2013). This reflects the predominantly hydrogenetic (seawater source) origin for metals in the CI nodules versus dual seawater-pore water sources for most other nodules. The concentrations of many critical and strategic metals have not been previously analyzed for CI nodules, so comparisons with other nodule fields have been limited. To address this, we analyzed a set of nodules distributed throughout the CI EEZ for a complete set of 67 elements, including all of the metals that may be of economic interest, such as the rare earth elements (REEs), yttrium, tellurium, niobium, zirconium, tungsten, titanium, and others (see selected elements in Table 1). In addition, we recalculated the tonnages of nodules and contained metals from nodule abundance areas (in square kilometers) determined by GIS ArcMap calculations based on JICA/MMAJ (2001) nodule distributions. The nodule tonnage calculated and summed from each abundance sector yields a total inferred resource estimate of 9.66 billion tonnes of nodules covering an area of 1.21 million square kilometers; using a cut-off of 6 kilograms of nodules per square meter, yields a median tonnage of 8.59 billion tonnes of nodules covering 687,647 square kilometers (Table 2).

Sep 14, 2011

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 Jan Stenlokk

The Norwegian Petroleum Directorate, which is the Government agency for the management of offshore geo-resources including seabed minerals, is about to finish this year’s marine data acquisition cruise in the Norwegian Sea. We would very much like to present the preliminary results of that cruise, including the discovery of a new black smoker and surrounding sulphide deposits.

Jan 1, 2018

By T. E. Sedysheva

The study of Co-rich manganese crusts has reached the level which allows to start prospecting works in the observable future, and furthermore, probably, exploitation of ore deposits. In this connection, among other goals, the necessity to analyze a distribution of ore bed parameters in details is quite urgent. Foremost, these are crust thicknesses in connection with landforms and elements of submarine mountains relief. This report is based on representative sampling made in course of research cruises run by SSC Yuzhmorgeologiya over guyots of the Magellan Seamounts. Crustal covers could overlie seafloor surfaces which are confined to a various landforms and elements of relief under the condition, that they are free of sediments. These are planed parts of a summit surfaces, edges, spurs, rectilinear parts of slopes, intermountain saddles and volcanic edifices. It is known, that crustal thicknesses are different at a various forms of relief [1]. We processed statistically the data around crustal thicknesses, which were sampled by dredging and submersible drilling (Tables 1, 2).

Jan 1, 2010

By Carsten Rühlemann, David Friedmann, Bernd Friedrich, Thomas Kuhn

"This paper explores the option of direct reduction smelting of the nodules from the German license area in the equatorial NE Pacific in a submerged arc furnace (SAF). An optimized slag design is proposed to separate the larger Mn-bearing stream from the valuable metals (i.e. Ni, Cu, Co, Mo). The slag optimization allows a maximum of Mn to be retained in the manganese-silicate slag on the one hand and a maximized metal recovery in a FeNiCuCo alloy on the other. This way, the goal is to make use of the complete nodules (“zero-waste”) instead of extracting only the metals Ni, Cu, and Co, which make up about 3 wt%. The process closely relates to the “Inco Process” by the Ocean Management Inc. (OMI) of the late 1970s, which was a consortium of INCO (International Nickel Company, CAN; today Vale Canada), Preussag AG & Metallgesellschaft AG (GER), DOMCO (JPN), and Sedco (USA). However, the manganese containing slag is investigated in more detail to recover FeMn, FeMnSi and/or SiMn. To optimize the process modern tools such as thermo-chemical modeling in FactSage™ have been used. [1,2]Polymetallic deep-sea manganese nodules may offer a decreased dependency of raw material imports for Germany and the EU. Currently, four European countries (United Kingdom, Belgium, Germany, and France and an Eastern European consortium (InterOcean Metal)) hold exploration licences for these nodules in international waters in the equatorial NE-Pacific. The license areas each cover 75 000 km2 of the seafloor and are located in the Clarion Clipperton Fracture Zone (CCZ) south east off Hawaii at water-depths between 4000 and 6000 m. The nodules may be used as a resource for industrially important metals such as Cu, Ni, Mn as well as for technology metals like Co, Mo, V and Zn. The average chemical composition of nodules from the German license area is presented in Table 1. [3,4]"

Jan 1, 2017

By Matthew Kowalczyk, Steve Bloomer, Peter Kowalczyk

"Mineral deposits found near seafloor hydrothermal venting are of great economic interest. Valuable metals such as gold, copper, zinc, and other polymetallic sulfides are found in appreciable grades in seafloor massive sulfide (SMS) deposits associated with these vents. For mapping these deposits, electromagnetic prospecting is one geophysical method that is very useful because copper/gold rich deposits are highly conductive.Ocean Floor Geophysics (OFG) in 2008 developed the first EM system to successfully map the limits of conductive mineralization in a survey at the Solwara 1 deposit (Kowalczyk, 2008). Since then, towed coincident loop time domain systems have been developed by Waseda University (Nakayama and Saito, 2016) and have successfully detected known mineralization buried at 30m depth. Using a deep tow controlled source electromagnetic (CSEM) array, very clear anomalies have been measured (Murton, 2017) over known mineralization at the TAG field on the mid-Atlantic ridge.In 2014 and 2015, OFG partnered with Fukada Salvage and Marine Co. Ltd. and the Scripps Institution of Oceanography to map methane hydrate deposits off the coast of Japan using a towed controlled source electromagnetic (CSEM) system developed by Scripps. These hydrate deposits are resistive targets, and the Scripps system successfully mapped subsurface electrical resistivity distributions to depths of several 100 metres below the seafloor. OFG is attempting to extend the Scripps CSEM technology to map subsurface conductive SMS deposits to a similar range of depths below the seafloor."

Jan 1, 2017

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 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 K. Vanstaen, K. M. Cooper, S. Ware, S. L. Boyd

Remediation and restoration of offshore marine habitats is a relatively new concept with attempts in European regions largely being instigated by requirements of various strategic directives including Article 2 of the Habitats Directive (1992), the EC Water Framework Directive (2000, Article 2 of the OSPAR Convention (1992) and the developing European Marine Strategy Directive. A field experiment to establish the practicality of various options for rehabilitating the seabed on the cessation of dredging has been successfully set-up. The purpose of this experiment is to investigate the practicality and effectiveness of gravel seeding as a potential restorative method which could be applied at marine aggregate extraction sites following cessation of dredging. Zone 2, within Area 408 (offshore Humber) was chosen as the experimental site as there is some evidence for persistence of sand which may have resulted from screening operations at this site.

Aug 24, 2006

By J. W. Jamieson

INTRODUCTION Hydrothermal vents that form seafloor massive sulfide (SMS) deposits represent unique biodiversity hotspots that host many species that are found only at these sites. The destruction of these habitats remains one of the greatest environmental risks associated with proposed mining of SMS deposits. For this reason, there is a growing movement to protect active vent sites from direct and indirect effects of seafloor mining (Van Dover et al., 2018). Mitigating the adverse effects of mining on these ecosystems may prove to be one of the greatest challenges facing the marine minerals industry. At the same time, there is increasing evidence that inactive or extinct hydrothermal systems, which do not host the density or diversity of animals typical of active vents, may constitute a significant proportion of the SMS resource potential on the seafloor. Mining inactive SMS deposits may therefore present an extractive opportunity that does not necessitate the disturbance or destruction of active vent habitats. However, if mining of SMS deposits is to take place only at inactive vent sites in order to protect active vent ecosystems, a clear definition of what defines a site as active or inactive is necessary. ACTIVE AND INACTIVE SEAFLOOR MASSIVE SULFIDE DEPOSITS Our understanding of the number of inactive deposits, their size and grades, and how they are preserved on the seafloor remains limited, largely due to the challenges associated with finding these deposits. Over 90% of all hydrothermal vent fields discovered so far are hydrothermally-active. Almost all of these sites were discovered through the detection of chemical anomalies associated with active hydrothermal venting via water column surveys. Inactive sites have no associated hydrothermal plume, and thus the well- established plume survey exploration method is not effective. As a result, very few truly inactive sites inactive sites have been discovered. Alternative exploration methods, such as spontaneous potential (SP) surveys, magnetic surveys, and high-resolution mapping are required (Cherkashev et al., 2013; Jamieson et al., 2014; Tivey and Johnson, 2002). As methods for locating inactive deposits continue to develop, our understanding of the distribution and resource potential of these deposits will increase, and the focus of resource exploration will shift from active to inactive vent sites. However, for now, most exploration and deposit development activities remain focused on active vent fields.

Jan 1, 2018

By S. Rajendran

Gas Hydrates (Methane Hydrates) are solid, ice ? like substances composed of water and natural gas. They occur naturally in areas of the world where methane and water can combine at appropriate conditions of temperature and pressure and are found in the ocean bottom sediments and in some permafrost areas. Besides temperature and pressure, factors like bathymetry, sediment thickness, sedimentation rates, and total organic carbon content (TOC) also control gas hydrate formation in the sea. The stability of gas hydrates depends on the critical high pressure ? low temperature combination (0-17 bars, 0-25ºC), which in turn dependent on the mix of gases from which the mineral is formed. As the critical parameters can be altered by deposition, erosion or slumping of sediments, formation or melting of ice cover, rise and fall of sea level and sudden temperature changes induced by tectonic activities, current flows or volcanisms, the gas hydrates tend to be very unstable. It is becoming increasingly evident that naturally occurring gas hydrates are significant component of the shallow geosphere and are of societal concern in at least three major ways: as an energy resource, a geologic hazard and a major contributor for climatic changes.

Jan 1, 2010

By Richard Harrison, Frank Lim

Deepsea Mining will soon become a reality with Nautilus Minerals getting their equipment ready to mine SMS at Solwara 1 off the coast of Papua New Guinea. The vertical transport system (VTS) adopted by Nautilus consists of a riser hanging ‘freely’ from the mining production vessel with a lifting pump unit suspended at its lower end. A compliant jumper connects the pump to the seabed crawler without restraining its movements. In this free-hanging VTS arrangement, the vessel can be re-positioned to follow the crawler should it want to extend the mining area and start stretching the jumper. A recently proposed alternative to this is a free-standing VTS whereby the riser is grounded on the seabed with a base and maintained in an upright position by distributed buoyancy modules or a buoyancy tank at the top. A compliant jumper connects the seabed crawler to the riser base, and another connects the riser top to the vessel. In this free-standing arrangement, the entire VTS can be lifted clear of the seabed for relocation to a new mining area. This paper will describe the important features of the two options and discuss the advantages and disadvantages in respect of riser dynamic behavior, water depth, weather and mining windows, pump maintenance, installation and retrieval, continency measures, etc. The two systems will also be appraised separately for mining SMS and SMnN deposits.

Jan 1, 2018

By Thomas Kuhn

The detailed investigation of both active and inactive submarine hydrothermal systems has gained tremendous progress during the last decades because of the increasing usage of remotely operated vehicles (ROV) as well as manned submersibles. Special aspects like the targeted sampling of chimney structures and vent fluids as well as the analysis of zonations of near-surface structures like sulfides mounds was only possible with the usage of such vehicles. However, the availability of such vehicles has been very limited because of the few number of deep-water ROVs and manned submersibles which need both a trained crew and a special research vessel. This was especially true for the German science community which did not have such devices at its disposal until recently. With the ROV QUEST 5 which is based at the University of Bremen (c/o. Prof. Dr. G. Wefer, Dr. V. Ratmeyer) this major drawback has now been eliminated.

Jan 1, 2003

By Carl L. Kaiser

This abstract discusses selected recent technology developments at the Deep Submergence Lab at the Woods Hole Oceanographic Institution aimed at fundamentally changing the nature and scope of AUV operations in the deep ocean. The Autonomous Underwater Vehicle (AUV) Sentry is described in its current configuration with discussion of emerging capabilities. Telepresence enhanced AUV operations are discussed including moving both operations and data processing personnel off the vessel. Autonomous Surface Vessel (ASV) aided AUV operations are discussed including recent experiments where an ASV provided both navigational aiding and a satellite based relay for acoustic communication of telemetery and mission redirection. New flexible communications strategies to perform intervention and manipulation tasks from an untethered vehicle are discussed. The abstract concludes with a brief discussion of industrial collaborations, including the newly launched Center for Marine Robotics.

Sep 14, 2011

By Mark Vardy, Kasia-Leigh Chidlow, Tim Minshull, Jeorg Bialas, Sven Peterson, Bramley Murton, Alba Gil

Since the discovery of the first black smoker on the East Pacific Rise in 1977 (Francheteau, et al., 1979), the hydrothermal vents, now called seafloor massive sulphides (SMS) deposits, have generated great interest in the geological community, especially regarding their formation and composition. SMS deposits are areas of hard substratum, with high base metal and sulphides content, that form through hydrothermal circulation and are commonly found at hydrothermal vent sites. The high base metal (Fe, Cu, Zn, Pb), sulphur-rich mineral content has interested mining companies, due to their potentially high economic value. Currently, the known SMS deposits do not have the same dimensions as the massive sulphides (MS) found on land (covering just 10s to 100s m2) and pose significant mining challenges (being located in water depths between 800 m and 6000 m), meaning that they do not appear to be economically exploitable at present. However, these deep-sea mineral resources could be important targets in the near future, particularly with our ever-increasing demand for base metals. A key aim of the European Union-funded Blue Mining project is to develop techniques to robustly quantify SMS deposits dimensions (both surface expression and subsurface extent) and therefore assessing the suitability of SMS deposits for future economically viable and environmentally clean deep-sea mining operations.

Jan 1, 2017