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By Robert M. Owen

The rare earth elements (REE1s; atomic number 57 -71) exhibit a coherent chemistry, are widespread in nature, and tend to occur in characteristic concentrations in different geochemical phases. Because of their predictable chemistry, the REE's-are highly useful as indicators or tracers of geochemical processes, and are often used as such in investigations of the genesis of terrestrial ore deposits. However, analogous applications of the REE's to the study of marine mineral deposits have been constrained by our limited understanding of the marine geochemical cycle of these elements. For example, a continuing area of uncertainty in this regard involves the so-called "REE Mass Balance Problem." This problem refers to the fact that detailed geochemical mass balance calculations typically predict a significant imbalance for the REE's; i.e., the calculations predict that REE removal rates from seawater are 11-18 times greater than their input rates. Yet all other chemical considerations indicate that the REE budget should be roughly in balance. Recent studies at The University of Michigan suggest the solution to this problem lies in understanding the the role of seafloor hydrothermal activity in the marine budget of the REE's. Geochemical analyses of hydrothermal sediments from two Pacific sites (East pacific Rise at 19°s and the Southern Juan de Fuca Ridge at 45°N) clearly show that the REE component of hydrothermal sediments is primarily acquired via scavenging from seawater. Iron oxyhydroxides, which form as precipitates when hydrothermal solutions are debouched onto the seafloor, are the active scavenging agent. Although the REE content of hydrothermal sediments generally increases with increasing distance from the rise crest, this increase is especially pronounced for sediments deposited below the lysocline,

Jan 1, 1989

By Akira Usui

Platinum is one of the most rare elements in the earth?s crust, but it is significantly enriched in some hydrogenetic ferromanganese crusts in the ocean. The element is essential to the electric industry and is believed to be of importance as a raw material a future fuel-cell industry. The earlier reliable chemical analysis of platinum-group elements (PGE) of ferromanganese crusts have indicated a variety of concentrations of Pt in the range of 100 ppb to a maximum of about 1 ppm, but little is known about the elemental abundance in ferromanganese crusts on fine-scale, or the geochemical behavior and form of the element. The chemical and mineralogical forms of platinum and its group are important in planning the methods of mineral exploration and extraction of the elements from of ferromanganese crusts. We attempted to characterize the distribution pattern within a cobalt-rich crust on the fine to microscopic scales by using reflecting microscope, scanning electron microscope/energy-dispersive spectroscopy, electron microprobe X-ray analysis (EPMA), ICP-mass spectroscopy, X-ray absorption near edge structure (XANES), small-focus XRF, and X-ray diffraction (XRD). These data indicated a wide range of Pt concentration from 150 to 700 ppb within a crust, though we found no distinct inter-element correlation or mineralogical control. Under the reflecting and electron microscope, no distinct Pt-bearing minerals or particles were identified. Small-focus XRF indicated no uneven distribution in any particulate matter, but all areas are less in abundance than the detection limit of about 10 ppm. Our tentative conclusion is that zero valence Pt0 (as suggested by XANES) is dispersed in the form of submicroscopic material most probably within ferromanganese minerals, and therefore, Pt-rich mineral particles may not be a major carrying phase.

Jan 1, 2005

By Siobhan Quayle

Managing sediment plumes under multiple jurisdictions Management of activities in the New Zealand EEZ can be characterized as a distributed basis of decision-making with each independent and separate decision-maker focused on specific elements of a proposal (environmental, work place safety, wildlife management, fisheries, navigation, oil spill). The New Zealand EEZ Act 2012 was intended as gap-filling legislation to address the lack of an environmental assessment lens for permissions to undertake certain activities in the New Zealand EEZ. These activities relate mostly to marine scientific research, dumping and discharges, oil and gas exploration and development, and seabed mining. The regulatory decision-maker for most EEZ Act marine consents is the New Zealand EPA. Since 2013 when this gap-filling legislation took effect, the EPA and its decision- making committees have processed three seabed mining applications. Two consents were refused, one consent was granted in 2017. A common feature of all consents has been the assessment and consideration of the scale, significance and effects of sediment plumes arising from the activity. One consent is for irons and mining in about 40m of water where the plumes reach the nearby coastal waters and shoreline, the second consent is far offshore but plumes extend far beyond the mining area (850 km2) in to rare coral habitats and in to a significant offshore fishery. A significant consideration for decision-makers is how the assessment and management of plumes under the EEZ Act interact with, and potentially overlap, management of such plumes under other legislation (Resource Management Act, Marine Mammals Protection Act, and Wildlife Act). This is in a statutory context where the EEZ Act requires explicit consideration of the nature and effect of other marine management regimes over the matter under consideration.

Jan 1, 2018

The chemical composition of the nodules varies with the type of manganese minerals and the size and characteristics of their nucleus, but those who have an economic interest have the following composition: Mn 29%, Fe 6% Si 5%, Al 3%, Ni 1.4%, Cu 1.3%, Co 0.25%, Na 1.5%, Ca 1.5%, Mg 0.5%, K 0.5%, Ti 0.2 0.2% and Ba 0.2% (Morgan, 2000; ISA, 2002). The Pacific Rim is an area of abundant occurrence of polymetallic nodules (Glasby et al., 1980; Morgan, 2000). According to these authors, the Pacific sea floor of the Clarion-Clipperton Zone (CCZ) is one of the most interesting areas in regard to the genesis of polymetallic nodules. Their abundance in the ocean floor is very variable, as there are places where they cover more than 70% of the ocean floor. The nodules can be found at any depth, but the highest concentrations are between 4000 and 6000m (Morgan et al., 1993). In studies conducted in the EEZ of the Mexican Pacific are those made within the project "Research on the origin, process and distribution of minerals in the Pacific ocean floor in the Exclusive Economic Zone of Mexico". Within this project Rosales (1989) conducted studies on the origin, process and distribution of polymetallic nodules, finding that a number of processes give origin to nodules, being diagenesis one of the main mechanisms of elements that contribute to the nodules. Besides hydrothermal processes that are carried near the East Pacific Rise at 21° N, inputs are contributing to the nodules metallic elements and sediments, especially in regions close to the dorsal, as a greater influence hydrogenetic processes occurs westward (Rosales and Carranza, 1990). In 1993, after cruise MIMAR II, Carranza and Rosales refer that metals such as Cu, Co, Ni, Sn, Fe, Mg, Pb, Zn and Ba may have a relationship with the East Pacific hydrothermal activity and sea currents carry these metals in solution to the Clarion-Clipperton fracture area, where there are hydrogenic metals sources (Al, Fe and Mn). As result of chemical analysis of Mn, Cu, Ni and Co, polymetallic nodules observed in part of the EEZ of Mexico are possible of potential economic interest (Rosales and Carranza, 1990, 2001; Carranza and Rosales, 2003).

Sep 14, 2011

By R. Moss

Gold and silver are important byproducts of mining volcanogenic massive sulfide (VMS) deposits. Both metals occur in VMS deposits ranging in age from the Archean to the currently forming massive sulfides found on the ocean floor. The gold- and silver-rich deposits on the modern seafloor are geographically diverse and occur in several different tectonic settings (Figure 1a,b) including seamounts (e.g. Franklin Seamount, Papua New Guinea), unsedimented mid ocean ridges (e.g. TAG and Snakepit, Mid Atlantic Ridge), sedimented mid ocean ridges (e.g. Escanaba Trough) and back-arc basins (e.g. Manus Basin, Papua New Guinea). Interestingly, the most gold- and silver-rich deposits are found in the back-arc basins of the western Pacific, commonly associated with differentiated volcanic rocks such as the dacite-rhyodacite suite at PACMANUS in the eastern Manus Basin. This suggests that different, or more efficient, mechanisms are concentrating precious metals in such back-arc settings. Such mechanisms may include leaching of volcanics enriched in gold (e.g. rifted arc crust) or silver (e.g. continental crust) and/or the introduction of gold into a hydrothermal system by a magmatic fluid. The gold content of modern seafloor precipitates varies from a few ppb up to a high of 54 ppm reported from eastern Manus Basin (1). The Jade Deposit in the Okinawa Trough has the highest silver contents with values up to 1.1% (2). Both gold and silver are preferentially concentrated in late-stage, low temperature precipitates with zinc-rich assemblages being favoured in most cases. Gold is found as relatively pure native gold and sub-microscopic inclusions in gold-rich deposits, but occurs predominantly as sub-microscopic inclusions and possibly as solid solution in the gold-poor deposits (3). Silver occurs as rare silver minerals such as acanthite and native silver in the silver rich Jade deposit (2), but more commonly in the silver-containing minerals tetrahedrite and tennantite, as is the case in the PACMANUS deposit. Tetrahedrite is also known to be an important host of silver in ancient VMS deposits (4). More abundant sulfides can contribute significantly to the silver balance. In the silver-poor deposits at 21 N East Pacific Rise, silver is contained entirely within chalcopyrite, isocubanite, pyrite, marcasite, sphalerite/wurtzite and galena. In this case silver may be present as sub-microscopic inclusions of silver minerals or in solid solution.

Jan 1, 2011

By Mikhail D. Ageev

The paper concerns with some questions of Autonomous Underwater Vehicle (AUV) control system design, which allows a motion at rough undersea terrain. The AUV advantages reveal itself completely during exploration of such objects as seamounts and reefs area. These objects are characterized by steep slopes (30 degrees and above) and chaotic situated obstacles (rock debris, pinnacles, escarpments). Uses of other technical facilities for operating in such formations are difficult, dangerous or impossible. These regions take an interest due to the presence of iron-manganese crusts. Modern AUV can estimate density of mineral by means of still camera or video recorder. For this reason the vehicle has to move with the distance of 3-5 meters from seabed. Under such conditions micro- and mesorelief presents a considerable danger for AUV. The AUV can bypass underwater obstacles in the various ways. However, in any case AUV motion will be characterized by intensive maneuvering on various speeds (from 0 up to 1.5 m/s), circular change of tractive force vector and, hence, a circular flow about the hull. So, AUV is equipped with the propulsion system, which provides free modes of motion.

Jan 1, 2003

By William D. Siapno

The International Marine Minerals Society has now come of age! Previously known as the International Marine Mining Society, it was an informal group without officers, by-laws or official status. Despite the lack of formal structure, the Society has cosponsored symposia both in Europe and in North America including the 16th Annual Underwater Mining Institute in Halifax, Nova Scotia, last year. The roster of members is now sufficient to emerge as a fledgling professional society. To this end an ad hoc committee was appointed to prepare by-laws stating the objectives of the Society, provide the procedures for the election of officers and other guidelines essential for the operation of the organization. This paper briefly summarizes the history of the group, the by-laws, together with membership requirements.

Jan 1, 1986

By Johnson R. Cann

Ocean floor sulfide deposits are now known from many parts of the world mid-ocean ridge system and from some seamounts. Clearly they can be expected to occur commonly on the ocean floor. However, only two or three of the known deposits appear to approach the million-ton size, and in none of the deposits has the grade been well-defined. Can knowledge of the processes that happen within the hydrothermal plumbing below deposits help define the conditions under which large, high-grade deposits form? Here I review present knowledge of ocean-floor hydrothermal processes to attempt a first answer to this question. There are three sources of information about these processes. The solutions emerging from active systems must be compatible with patterns of alteration that underlie the volcanogenic sulfide deposits of ophiolite complexes, which are slices of ocean crust thrust onto land. Both of these types of evidence can be linked by computer modelling of the exchange of heat and metals between rocks and flowing water.

Jan 1, 1988

By Campbell McKenzie

Substantial consideration has been given to the implications that the morphology of the Chatham Rise deposit will have on mining operations. The glacio-tectonic processes involved in the distribution of nodules on the rise has in several areas been quite significant. The recent cruises by Chatham Rock Phosphate Limited (CRPL) have collected data which has affirmed the assumptions previously made and catered for in historic resource estimations. The deformation and displacement of the phosphorite during glacial periods and the redistribution of the mobile sand during interglacial periods is interpreted to have produced a highly variable pattern of phosphorite concentration (kg phosphorite/m2) and coverage (% phosphorite/sample weight). The phosphorite resource probably has a significant spatial variability at a scale of tens of metres. Results of recent surveys show phosphorite-rich patches alternating with phosphorite-poor areas at distances of less than 20 m. The high spatial variability of the deposit has had a bearing on how historical information for the project has been regarded and integrated with the recent exploration approach and data collection process. This coupled with the proposed extraction tool has influenced the size, nature, extent and siting of the proposed mining blocks

Sep 14, 2011

By J. V. R. Prasada Rao

India is dependent for 60% of its annual requirement of copper and the entire quantity of nickel and cobalt on imports from outside the country. Land-based resources are either too meager or of too low a concentration for economic exploitation. This has prompted the country to look to deep seabed re- sources for meeting its rising demand for these metals. The Ocean Policy of the Government of India announced in 1982 talks about the need to map and assess the availability of minerals in the deep sea and to develop necessary technologies for exploration and exploitation of seabed minerals. To be self-reliant such technologies would have to be largely developed, tested and operated indigenously. The adoption of the Law of the Sea Convention in 1982 gave a fillip to India's desire to get into the field of deep seabed mining. India applied for recognition as a Pioneer Investor in Ocean Mining in 1983 and received allotment of a mine site of 150,000 km2 in the Central Indian Ocean in August 1987. Simultaneously, the Government has taken up a programme of development of technologies for exploration of the mine site for resource assessment, environmental monitoring also to meet the commitments like relinquishment of 50% of the area to the Preparatory Commission. Technologies for exploitation of these seabed resource like the mining system, transportation and extractive metallurgy have also been taken up for development in various research institutes largely in the government sector. While India's objective in the long term is to meet the shortage of copper, nickel, cobalt and manganese by the turn of the century, in the short term, the programme aims at application of the seabed mining technologies to meet the immediate needs of the country such as: a. Exploration for oil and natural gas. b. Exploration and exploitation of placer minerals and other deposits at shallow depth in India's EEZ.

Jan 1, 1994

By Richard H. T. Garnett

Large scale, profitable, offshore mining of cassiterite started in 1907 around the coast of south Thailand and continues today in Indonesia. The more complex marine mining of diamonds commenced in the early 1960?s and is now an established industry off the coast of Namibia in southern Africa. The activities have involved many diverse organisations, and have required the development of new marine mining equipment. De Beers Marine, more recently as contractor to Namdeb, has been the dominant producer since 1989. Smaller, public, mining companies, registered in South Africa, Canada and the U.K., have achieved mixed performance results, but the total annual revenue from offshore diamonds now exceeds about US$ 180 M. With the benefit of hindsight, there are some useful lessons to be learned from the experiences. Mining of placer deposits at sea is more difficult and more costly than on land. It justifiably commences in response to a market demand for a product that cannot be supplied in sufficient quantity from onshore sources, not because the marine resource exists. The high costs can be offset in places by submarine grades so high that they have not been seen on land for a century. Technical and commercial success requires a combination, and a sufficiency, of ore reserves, capital, experienced people, and technology. Economic viability is not achieved easily and some diamond mining companies have experienced a very short productive life, terminating in their acquisition or liquidation. The reasons for failure in marine mining, regardless of whether the product is diamonds, gold, or tin, invariably are similar and fall into two categories. Those outside a company?s control include the sea conditions, taxation and fiscal climate, security of lease tenure, and the diamond market. The others, assignable to the company, provide important instructions for those who may aspire to advance the cause of marine mining.

Jan 1, 2004

By Delphine Pierre, Jean-Marie Augustin, Anne-Sophie Alix, Charline Guérin, Cecile Cathalot, Yves Fouquet, Arnaud Gaillot, Ewan Pelleter, Carla Scalabrin, Florian Besson

With the world’s growing demand for metals, seafloor massive sulfides (SMS) deposits are now seen as a possible mineral resource that could contributes to secure metal supply for human needs. SMS deposits are characterized by high concentrations of base metals and at some place high contents of precious and rare metals. Since 1977 and the discovery of the first high temperature (HT) hydrothermal vent and its sulfide mineralization and high biodiversity, more than 300 sites are known today. If the exploration strategy for detection of active hydrothermal sites is now robust, their associated mineralization will not (and must not) constitute a potential target for deep-sea mining due to environmental concerns and technical limitations. Recent studies on SMS deposits are rather focused on extinct and buried mineralized sites characterized by a lower biomass. Several geophysical techniques to explore and detect extinct SMS (eSMS) and buried SMS (bSMS) have been developed (e.g. Kawada and Kasaya, 2017; Szitkar et al., 2017, 2014) using different approaches (e.g. regional or local scale; ship-based or using underwater vehicles) with several degrees of success or limitation. Here we present results from acoustic surveys performed on the TAG hydrothermal district during the BICOSE (2014) and LEVE-SMF (2016) cruises and direct observation provided by HOV (Nautile) dives carried out during HERMINE cruise (2017). Acoustic data were acquired using two different multibeam echosounders (MBES): the hull-mounted Kongsberg EM122 (12 kHz, R/V L’Atalante) and the ROV-mounted RESON SeaBat 7125 (400 kHz, ROV Victor) (Figure 1). After processing, acoustic seafloor backscatter data from both MBES provides complementary qualitative results in relation to the seafloor composition. The analysis of the seafloor backscatter data obtained by near-seafloor surveys with the high-resolution 400 kHz MBES shows a clear relationship between low backscatter strength values and areas covered with pelagic and hydrothermal sediments whereas high backscatter strength values are associated to pillow lavas and basaltic scree. Intermediate backscatter strength values are rather related to old and younger eSMS as well as to mineralization on TAG active mound.

Jan 1, 2018

By Akuila K. Tawake

The occurrences of polymetallic minerals within the Exclusive Economic Zones (EEZs) of many Pacific Island Countries (PICs) have been confirmed through marine scientific researches and seabed minerals exploration in the last forty years, and are increasingly being recognized by nations as a future potential source of revenue and economic development. For many of the smaller PICs, this may represent the only exploitable natural resource sector apart from fish. SOPAC (then under the CCOP/SOPAC) was actively involved with deep sea mineral exploration in many countries in the South Pacific between the 1970s and early 1980s that led to the discovery of a number of seabed mineral occurrences within the EEZs of these countries. In collaboration with SOPAC, a number of multinational consortia and national agencies were involved in this early stage of seabed mineral prospecting in the region. This was followed by a twenty-year (1985-2005) marine mineral prospecting in the Pacific through the collaborative effort of the Government of Japan and SOPAC as well as the Ridge 2000 program. Other mineral prospecting and marine scientific research initiatives have been conducted in recent years and the most notable one is the Nautilus Minerals advanced exploration in the Manus Basin in PNG. Based on the results of previous exploration, a number of countries in the region with moderate to high deep sea mineral resources potential are identified. Seafloor Massive Sulphide deposits have been confirmed in PNG, Tonga and Fiji while the Cook Islands and Kiribati have high manganese nodule resources potential in addition to significant occurrences of Cobalt-rich Crust within the EEZs of the Marshall Islands and the Federated States of Micronesia. Despite the recent surge in deep sea minerals interest and activity around the Pacific, specific policy, legislation and regulations necessary for the governance of deep sea mineral resources are lacking. Also lacking is the specific technical and human resources capacity essential to ensure that PICs are able to effectively manage these seabed resources. Consequently, SOPAC under the EU funded Deep-Sea Minerals (DSM) Project will work with Pacific ACP States to develop a regional regulatory framework from which they can develop their national frameworks for the sustainable management of their marine mineral resources. The work is of critical importance if PICs are to have effective environmental, fiscal and social management instruments in place for the exploration and exploitation of deep sea minerals that could support economic growth within the region as a whole.

Jan 1, 2010

By Sung-Hyun Park

Core sediment samples collected from the KODOS area of the Clarion-Clipperton Fracture Zone in the NE Equatorial Pacific were analyzed for chemical and mineralogical compositions to investigate the depth- and time-related variation of paleoenvironmental and paleoceanographic conditions during their deposition. These core sediments are divided into three layers from top to bottom by its color; 1) brown layer (Unit I), 2) pale brown layer (Unit II), and 3) black brown layer (Unit III). Geochronology of 10Be indicated the depositional age of Quaternary for Units I and II and of late Pliocene for Unit III with a potential short hiatus between them. Analyses of interelemental correlation identified three major groups of elemental groups that show moderate-to-strong correlations: 1) Al, Ti, K, and Fe representing for terrestrial alumino-silicate fraction of sediments, 2) Ca, P, REEs, Cu, and Zn for biogenic apatite, and 3) Mn, Ni, and Co for hydrogenous Mn-oxide. With an exception, Fe content was very high and showed fair correlations with Mn, Ni, and Co in Unit III. Unit III shows high smectite but low quartz and illite contents compared to the overlying two units, indicative of reduced supply of terrestrial materials. In a meanwhile, major elements (Fe2O3, CaO, P2O5), minor elements (Cu, Zn) and REEs are highly enriched in Unit III compared to the upper two units. All these elements other than Fe reflect the fraction of biogenic apatite, which indicates higher fraction of biogenic components in Unit III. This is also supported by higher amount of smectite formed by the consumption of siliceous biogenic components. The reduced supply of terrestrial material and/or increased productivity of surface water at the time of Unit III deposition are attributed to Pliocene warming preceding Northern-pole glaciation during Quaternary. Unit III also includes clinoptilolite and unidentified 8Å mineral, likely amphibole, that are absent in Units I and II, suggestive of the possibility of different source region and/or materials during Pliocene. Higher contents of Mn and Fe in Unit III are likely due to the high fraction of Mn-oxide that was formed by diagenetic process after deposition.

Jan 1, 2003

By LeRon E. Bielak

Public Law 103-426 was signed into law in October 1994. Its provisions amended sections 8(k) and 20(a) of the Outer Continental Shelf Lands Act (OCSLA). The 8(k) amendment provides the Secretary of the U.S. Department of the Interior 001) with new discretionary authority to negotiate agreements for using Outer Continental Shelf (OCS) sand, gravel, and shell resources for certain projects of public benefit (e.g, beach, shoreline and coastal wetlands restoration that are under- taken by a Federal, State or local government agency). The new law also covers construction projects that are funded wholly or in part or authorized by the Federal Government. Under the law, the Secretary may assess a fee for use of the resource by taking into consideration the value of the resource and the public interest served. The law also requires that any Federal agency proposing to make use of OCS sand, gravel, or shell resources enter into a Memorandum of Agreement (MOA) with the DOI. An MOA would promote efficient coordination and resolution of inter- agency scheduling and issues. The law requires that Congress be notified before use is made of these OCS resources. The amendment to section 20(a) of the OCSLA clarifies that obligations concerning environmental studies extend to non- competitive lease situations and includes minerals other than oil and gas. The Minerals Management Service (MMS) is the DO1 agency responsible for interpreting and implementing the provisions of Public Law 103-426. The negotiated agreement approach is distinctly different from the competitive bidding requirements that have applied to all OCS minerals since the inception of the OCSLA. The MMS has opted to implement the new law in a nontraditional manner. Rather than issuinga body of new regulations to cover the negotiated agreement situation, or attempting to amend three sets of existing regulations, MMS is pursuing a less formal approach of providing guidelines. More weight is placed on the negotiation process itself and the legal agreement that consummates the process as the means for establishing ground rules, terms, and conditions under which qualifying projects may be conducted. This process must recognize and adhere to requirements of other laws, including the National Environmental Policy Act.

Jan 1, 1995

By Sukumar Bandopadhyay

The Marine Minerals Technology Center (MMTC) was authorized by an act of the United States Congress in 1996. The act established several marine minerals research centers in the U.S., including one at the University of Alaska Fairbanks. The Alaska MMTC is funded through the Minerals Management Service of the Department of the Interior and concentrates its research in the Arctic seas region. Recent research projects at the MMTC include, among others, application of a geographic information system (GIS) to the gold placer deposits offshore Nome, Alaska, development of a marine gold placer reserve definition model using a neural network, and development of an expert system model for submarine tailings disposal (STD) planning and decision-making. Although geostatistics remains the most prevalent method used today for ore grade estimation, researchers have made numerous improvements over the years for accurately predicting grades of ore using other estimation techniques. One such technique, the neural network, has recently emerged as an alternative to geostatistics for grade estimation purposes. A neural network is a non-linear, model-free estimator that is well-suited for noisy and/or sparse data environments. Neural networks perform best with non-linear spatial data, contrary to the stationary assumption of ordinary Kriging techniques. In the marine placer ore reserve definition model, the neural network technique was used to estimate placer gold reserves offshore Nome. This study demonstrated the utility of neural network modeling over other traditional ore reserve estimation methods, especially for high cut-off grades. Some of the relevant issues of neural network modeling were also addressed in the study. In testing, the neural network produced results that were close to those from geostatistical techniques including Kriging, polygonal, and inverse distance methods.

Jan 1, 2005

By R. W. Nesbitt

The TAG and Broken Spur hydrothermal mounds are located on the Mid Atlantic Ridge (MAR) at 260N and 290N (respectively). Both were initially discovered by exploratory work from surface vessels and both have since been investigated by submersibles. The discovery of TAG resulted from a NOAA Trans-Atlantic Geotraverse (Rona et al. 1975) which fortuitously sampled low temperature materials on the east wall of the MAR rift valley and follow up operations (Rona et al. 1986) located the high temperature (365°C) mound some 5km to the west. In 1994, ODP deep sea drilling (Leg 158) at over 3,500 metres of water recovered core to a depth of 150 m below surface (Herzig et al. 1998) and for the first time allowed a geological interpretation of an active mound. The Broken Spur mound was accidentally discovered in 1993 when sulphide fragments were observed on a deep-sea towed camera system (Murton 1993). Later that year, exploratory submersible dives by Alvin located the hydrothermal field and the area was again explored by submersible in 1994 and 1997. Despite the amount of work carried out, our geological understanding of the MAR mounds is limited. Much effort has gone into measuring fluid chemistry whilst practical difficulties have inhibited good geological mapping of the sulphide areas. It is clear from both TAG and Broken Spur that the mounds are not necessarily located in the areas of highest heat potential. Indeed, TAG is some 2 km from the rift valley axis and has been operational for several tens of thousands of years. Hence, heat availability is not a major consideration and the most obvious control is a structural one. Mapping on Broken Spur indicates a series of isolated vent-sulphide areas, concentrated around a minor graben. Their distribution, size and nature all indicate that they are residual parts of a much larger sulphide body which was at least the size of the present TAG field. The evidence is for a cyclical pattern of mound growth -mass wasting? rejuvenation and the Broken Spur mound appears to be in the rejuvenation stage of the cycle. Mound cyclicity must be related to the supply of hot water which itself is a function of the connectivity of fracture systems. Hence, we return to the theme that the major controls in mound development are structural ones.

Jan 1, 1998

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 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 Sukumar Bandopadhyay

The Marine Mining Technology Center (MMTC) was authorized by an act of the United States Congress in 1996. The act established several marine minerals research centers in the U.S., including one at the University of Alaska Fairbanks. The Alaska MMTC is funded through the Minerals Management Service of the Department of the Interior and concentrates its research in the Artic seas region. Recent research projects at the MMTC include, among others, a geographic information system (GIS) application to the gold placer deposits offshore Nome, Alaska, a marine gold placer reserve definition model using a neural network, and development of an expert system model for submarine tailings disposal (STD) planning and decision-making. Although geostatistics remains the most prevalent method used today for ore grade estimation, researchers have made numerous improvements over the years for accurately predicting grades of ore using various other estimation techniques. As a result, the neural network has recently emerged as an alternative to geostatistics for grade estimation purposes. A neural network is a non-linear, model-free estimator that is well-suited for noisy and/or sparse data environments. Neural networks perform best with non-linear spatial data, contrary to the stationary assumption of ordinary Kriging techniques. In the marine placer ore reserve definition model, the neural network technique was used to estimate placer gold reserves offshore Nome. This study demonstrated the utility of neural network modeling over other traditional ore reserve estimation methods, especially for high cut-off grades. Some of the relevant issues of neural network modeling were also addressed in the study. In testing, the neural network produced results that were close to those from geostatistical techniques including Kriging, polygon, and inverse distance methods.

Jan 1, 2004