Search Documents

By Rolf B. Pedersen, Ingunn H. Thorseth, Håkon Dahle, Ingeborg E. Øklandm, Linn M. B. Olsen

Weathering of sulfides and the generation of acid mine drainage (AMD) is a well- known environmental issue in on-land mining. The process can release potentially toxic compounds and heavy metals to the environment and is highly influenced by microbial activity. However, the weathering of sulfides in deep-sea environments is not well studied. In 2014 we therefore deployed two titanium incubators filled with freshly ground pyrite grains into an inactive part of the hydrothermal sulfide mound of Loki´s Castle vent field, aiming to study the in-situ seafloor weathering of the freshly exposed sulfides. Each incubator had five chambers placed in a depth profile, where the upper chamber was exposed to the bottom seawater. After one year of exposure, one incubator was collected and analyzed for weathering features and microbial colonization and community composition. In addition, one sediment core (25 cm deep) was collected from the sulfide mound in close vicinity to the incubators, and another core (45 cm deep) was collected from the (hemi)pelagic sediment just outside the sulfide mound. The cores were analyzed for geochemical composition of the solid material and porewater, and the microbial community composition aiming to define the redox zoning and dominating geomicrobiological processes in the natural deposits, and to unravel how these processes influence the mobility of heavy metals during sulfide weathering. Scanning electron microscopy (SEM) revealed development of Fe-oxyhydroxide weathering rims on the pyrite grains in the incubator chambers. Spalling of the rims on the most weathered grains, exposing fresh pyrite surfaces to oxidation, was commonly observed. The SEM investigation also revealed a positive correlation between weathering degree and microbial community density. Preliminary results from the microbial community analysis show a high relative abundance of putative sulfide oxidizers, suggesting that the community is governing the degradation of pyrite.

Jan 1, 2018

By Mark Vardy, Kate Dobson, Isobel Yeo, Paul Lusty, Bramley Murton

In response to anthropogenic climate change, the way in which we use and generate energy is changing. To facilitate these developments, it is essential that we increase and diversify the supply of ‘E-Tech’ elements essential for cleaner energy generation and more efficient usage. The vast majority of these materials (e.g. cobalt, lithium, niobium, platinum group metals, rare earth elements and indium) come almost exclusively from mining and new resources must be found and developed in order to secure supply and meet the demands of the future. Ferromanganese (FeMn) crusts are rich in cobalt, tellurium and rare earth metals, and are common on seafloor hard grounds at water depths over 1000 m. The mining of both FeMn crusts and nodules is potentially viable dependent of the balance of cobalt and nickle prices (Martino & Parson, 2012), however, crusts need to be at least 4 cm thick with cobalt contents of at least 0.8% (International Seabed Authority, 2008). The difficulty for those wishing to exploit these resources is firstly finding them, and secondly assessing their potential remotely. Such capability would not only save time and money, but also allow mining operations to be more focused, reducing needless destruction of seafloor habitats from exploratory mining or mining of noneconomically worthwhile deposits. In this contribution, we examine the distribution of crusts on a single Atlantic Gyot (Tropic Seamount), the morphology of FeMn crusts, their variable growth patterns and the characteristic geophysical response from crusts in various datasets, including ship based 60 m resolution multibeam and high resolution bathymetry, backscatter and sub-bottom profiler data acquired using an Autonomous Underwater Vehicle (AUV).

Jan 1, 2017

By Robert Corcoran, Piotr Jasiobedzki, Roy Jakola, Michael Jenkin

Vast mineral resources of copper, zinc, cobalt and gold have been identified off the coast of Papua New Guinea at depths exceeding 2,000 meters. Accessing them in a cost effective manner and without destroying the marine habitat requires overcoming numerous technical and operational challenges. Although there are a number of deep-sea mining operations underway worldwide, the depths encountered are significantly less than will be required to mine these ore deposits. To date, only the oil industry has developed technologies for successfully accessing reserves at depths of 3,000m.

By Brenda J. Burd

A very extensive spatial and temporal database on benthic infauna and associated sediment metals has been collected for Island Copper Mine on Vancouver Island, B.C. Canada from 1969 (pre-discharge) to 1998 (3 years post-discharge). The tailings deposited as organically impoverished, copper-rich, clays, silts and sands distributed according to particle size, bottom turbidity currents and strong, vertically mixed tidal currents. In addition, a large deposition of coarser waste rock along the north shore of Rupert Inlet contributed substantial material in the shallower, near-field area.

Jan 1, 2001

By Simon McDonald

The Neptune Group was established in 1999 to apply for exploration permits within New Zealand’s 200nm EEZ. These applications were to investigate and commercialise hydrothermal Seafloor Massive Sulphide (SMS) deposits identified by international researchers and to locate others. SMS are volcanically related seafloor accumulations of copper, lead and zinc with high levels of gold and silver. Neptune has three granted exploration licenses within the New Zealand EEZ and has application in other jurisdictions. Neptune undertook the world’s first commercial drilling exploration work of SMS in December of 2005.

Aug 24, 2006

By Luana Karvel, Lars Kullerud, Morten Sørensen, Øystein Halvorsen, Øivind Lønne, Elaine Baker, Tina Schoolmeester, Joan Fabres, Yannick Beaudoin

The UNEP Shelf Programme (USP) is the access point for a collaboration of international organizations with expertise in marine geoscience and maritime law. It was established in response to a United Nations resolution, stating that the United Nations Environment Programme (UNEP), working through the Global Resource Information Database (GRID) system, should work in conjunction with Intergovernmental Oceanographic Commission of UNESCO (IOC) and the International Hydrographic Organization, to assist coastal States, and in particular developing States and small island developing States (SIDS) with submissions to establish the outer limits of their continental shelf under Article 76 of the United Nations Convention on the Law of the Sea (UNCLOS).

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 Mikhail P. Torokhov

Typical coastal placers leave no doubt that placer accumulation can result in significant concentration of heavy minerals in marine shallow water environment. However, the same situation is quite predictable for guyot?s slopes at stages of submarine volcano formation and later submersion of guyots to a depth of up to 3-4 km. Where these placers could be found is also clear ? in coastal facies (as typical coastal placers), and in morphological traps down guyot slopes in zones of active submarine currents. The latter could be cracks in rocks, shallow depressions, spurs, and structures, such as coral reefs, stromatholiths, and even ferromanganese crusts. The last of these have been studied carefully by the author in the Magellan Seamounts and on the Mid-Pacific Rise: tens of minerals, including mineral forms of PGE, REE, Mo, W, Te, Cr, Co, Ni, Cu, &Zn were identified as a xenogenic (trash) minerals. The detailed study of polished epoxydized sections, showed that interstitial spaces of Fe-Mn botryoids are enriched in heavy minerals (predominantly titanomagnetite). Taking into account the irregular character of crust surfaces and their position in active water environment, we can definitely state that they are the ideal traps for placer minerals. Study of guyot basaltic matter showed the presence of similar REE, PGE minerals that are in the crusts, and the same (mostly) micron sizes of minerals. High content of PGE in some basaltic varieties (up to 1 ppm) suggests that this is a reasonable source of these elements in the crusts, rather than the water column (which is normally considered to be the case by most marine scientists). Predominance of Pt in hydrogenous (?) crusts is interpreted as due to the better stability of Pt mineral forms during weathering and transportation (these are isoferroplatinum, and silicides). Comparison of 143Nd/144Nd values in bulk crusts, heavy fraction of crusts, basalts, and water column supports the author?s idea, that a significant part of REE also comes from basaltic matter (in form of monazite, CeO2 etc.).

Jan 1, 2004

By Grigori Abramov

Borehole Mining (BHM) is a remotely operated underground and underwater method of extracting (mining) mineral resources by high-pressure water jets. It can be carried-out from the land surface, open pit floor, underground mine and floating platform or vessel. The method is currently in use in mining and exploration of such natural resources and industrial materials as: uranium, iron ore, quartz sand, gravel, coal, poly-metallic ores, phosphate, gold, diamonds, rare earths, amber and several more. Yet another application of Borehole mining technology is construction of subsurface collectors, ground walls and storage for compressed or liquefied gases, oil and other products.

By K. T. Damodaran

The Chavara and Manavalakurichi placer deposits have been known since a long time for their rich reserves of heavy minerals like ilmenite, rutile, monazite etc. While detailed work has been conducted on the mineralogy and texture of the bulk placer sediments, reports on the detailed investigations on individual minerals are relatively scanty. Though, limited work pertaining to the chemistry of ilmenite has been carried out by Nair et al (1995) and Ramakrishnan et al (1997), a comprehensive study of the weathering patterns of ilmenite along the longitudinal and vertical profiles has not been, so far, undertaken. Data on the microscopic analysis of ilmenite from the southwest placers, too, is sketchy. The present work deals with the variation of the weathering undergone by ilmenite in the southwest placer deposits based on chemical and mineralogical analyses.

Jan 1, 2002

By Lauro Calliari

Detailed geological studies using side scan sonar, bottom sampling and piston cores along the Rio Grande do Sul inner continental shelf and coastline indicate the occurrence of elongate deposits of calcareous shells fragments containing high calcium carbonate content. On the inner shelf these deposits lie at a depth between 15 and 50 meters and have been interpreted as ancient shorelines. They occupy an area of 965 km2 with a economic potential of 1 billion tons. Chemical analyses indicate a mean composition of 34.8% of calcium; 0.16 ppm of fluoride. According to the regional economy such composition make it highly recommended for a variety of uses including poultry feed and cement.

Jan 1, 1995

By James E. Dailey

Marine mining is driven by profitability, and profitability is driven in turn by people and equipment that can work productively and safely at sea. Design challenges faced by the marine mining community have much in common with those faced by the offshore construction community. Technical solutions continue to move freely between both communities. A brief pictorial history summarizes the evolution of offshore construction technology as it grew in the Gulf of Mexico and expanded worldwide. Attention is focused on those areas of platform and pipeline construcion where there is potential technology application to underwater mining. An especially difficult challenge faced by both communities is work in the surf zone. Some innovative concepts for surf zone construction operations are presented and possible applications to marine mining are suggested.

Jan 1, 1989

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 M. E. Williamson

From December 2004 through March of 2005 an extensive geophysical program was conducted to delineate polymetallic sulfide deposits in the Bismark Sea for a major mining concern. Deeply towed sidescan sonar, interferometric swath bathymetry, subbottom profiling, magnetic gradiometry, electrical resistivity, induced polarization. self-potential, gravimetry, water temperature/conductivity and towed video were among the methodologies tested against known occurrences of polymetallic sulfides in 1500 m -- 2200 m water depths. Known active and currently inactive sulfide areas were characterized using the various remote sensing techniques followed by survey with these same tools in other areas where they successfully discovered new prospects. Dredge sampling was used to ground truth both previously known sulfide areas and newly found deposits.

Jan 1, 2005

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 Georgy Cherkashov, Vladislav Kuznetsov

The presentation describes new data concerning the age of the Mid-Atlantic Ridge (MAR) hydrothermal fields. The collection of massive sulfides recovered from six hydrothermal fields has been dated using the 230Th/U method. The range of the data obtained is rather wide: from 2.2 up to 65.1 thousand years BP. Three stages of hydrothermal activity were detected for this 65 Kyr period of geological evolution: modern (0 -5), 20-25 and 58–65 thousand BP (Figure 1). This conclusion was confirmed by dating the associated metalliferous sediment layers which also indicate the hydrothermal events led to the formation of sulfide mineralization. There is a correlation between the age and size of massive sulfide deposits: older deposits are larger (Table 1). This and other applications of obtained data will be discussed in presentation.

Aug 24, 2006

By Sally Philpot, Siân E. Boyd, Hubert L. Rees, Emma Bee, Carla Houghton, Ceri James, Silvana N. R. Birchenough, S. Limpenny David, A. Coggan1 Roger, Koen Vanstaen

Every year approximately 22 million tonnes of marine sand and gravel are dredged form British waters. The eastern English Channel (EEC) contains substantial reserves, a proportion of which have been identified by the aggregates industry for potential future exploitation. The main aim of this study is to produce broadscale marine habitat maps of the EEC area. The UK aggregates industry has formed a consortium of representatives (the eastern English Channel Association), and have sponsored an initial baseline survey and follow-up sampling programmes as part of a Regional Environmental Assessment (REA) covering a patchwork of aggregate prospecting areas. To complement this effort, a large-scale geophysical survey was conducted in 2005 to place the REA in a wider spatial context and, thereby, to help assess the environmental significance of any future impacts arising from commercial aggregate extraction over the broader region of the EEC.

Sep 24, 2006

By V. Soloviev

The world?s data available on near sea-bottom gas-hydrate accumulation and deep-water fluid-discharge areas are presented in this paper. Gas-hydrate accumulation associated with fluid discharge (mud volcanoes, gas seeps, gas-saturated water seeps) is characterized by the following. First, the largest hydrate accumulations in sediments are located at shallow subbottom depths and have well-defined limits, especially in the upper subbottom part. Second, gas-hydrate formation in fluid-discharge areas is a present-day process, with the global occurrence of deep-water fluid-discharge areas numbering up to about ten thousand, and with all the seep areas being favorable for the formation of near-sea-bottom gas-hydrate accumulation. Third and principal, gas resources in the hydrates can be considered as renewable. Estimates of possible gas volume in single accumulations of hydrates and the global budget, as well as possible methods of gas utilization from such gas-hydrate accumulations are discussed in the paper.

Jan 1, 2005

By S. W. Chang, James R. Hein, S-R. Lee, A. Zondervan, H. Choi

"Nine Fe-Mn nodules from the extensive nodule field in the east of Campbell Plateau of southwest Pacific Ocean beneath the Deep Western Boundary Current (DWBC) and Antarctic Circumpolar Current (ACC) were analyzed for the 10Be/9Be dating by AMS (Accelerator Mass Spectroscopy) at IGNS, New Zealand.Several types of nodule morphology were identified including distinctive discoidal forms with overgrowths resulting possibly from overcrowding and partial sediment burial. Five principal nodule facies were also recognized by location and occurrence (Fig. 1) (Wright et al., 2005). Fe-Mn nodules show various concentric internal growth textures, such as, cuspates, large parabolic cuspates, pseudo-columnar, columnar, globular, and laminated, which vary even in a nodule with hydrogenetic, early diagenetic, or mixed origin. Each texture shows micro-textural varieties and different mineralogy and/or chemistry. The genesis of each internal texture was indicated by the REE patterns, the mineralogy of Mnoxides, and the Mn/Fe ratios."

Jan 1, 2017

By Andrea Koschinsky

Recent technological breakthroughs in the fields of ceramics, medicine, aerospace engineering and electronics (semi- and superconductors) are constantly creating new uses and an ongoing increasing demand for a variety of rare valuable trace metals. These so-called high-tech elements such as hafnium (Hf), titanium (Ti,) niobium (Nb), tantalum (Ta), zirconium (Zr), molybdenum (Mo), vanadium (V) and the rare earth elements (REE), many of them of strategic importance, occur inter alia at elevated and potentially economic concentrations in marine ferromanganese nodules and ferromanganese crusts, making those deep sea deposits potential future resources of these metals. As these metals are mostly present in the lattice of the manganese and iron phases, which are strongly intergrown, rather than in separate mineral phases within the nodules and crusts (Koschinsky and Hein, 2003), reductive dissolution of the host phases is a prerequisite to release and dissolve the valuable metals. To evaluate the association of these rare valuable metals with their mineral carrier phases, sequential leaching experiments were carried out on selected samples in a first step in our project.

Jan 1, 2011