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By Dallas L. Peck

The U.S. Geological Survey (USGS) recently completed phase 1 of a mapping effort that makes the United States the first nation to systematically acquire image maps of its underwater lands. In 1984, the USGS, as part of its mission to map and characterize the resources of the Federal lands, began a mapping effort in the newly proclaimed Exclusive Economic Zone (EEZ). The goal was to provide sonar image maps of this frontier area within 10 years. The mapping program is on schedule, with two-thirds of the EEZ sea floor, approximately 2 million square nautical miles, happed in 7 years. The deep water EEZ (depth greater than 200 m) around the 50 states is now complete except for the North Slope of Alaska, where ice precludes our surveying with a surface ship. Phase 2 of the EEZ mapping effort will begin in 1994, focusing on the American Flag islands of the western Pacific. Approximately 1 million square nautical miles of sea floor remain to be mapped around the islands.

Jan 1, 1992

By Rahul Sharma

Although, mining of minerals such as polymetallic nodules and sulphides from the deep sea floor has been delayed due to the combination of factors such as current availability of Cu, Ni, Co, Mn (and other metals) on land and their fluctuating prices; these deposits are still considered as the alternative source for metals in the 21st century. Exclusive rights for exploration in the ?Area? (beyond the national jurisdictions of any country) given to eight countries and consortia by the International Seabed Authority and the estimated resource of 300 million tonnes in a typical area of 75,000 km2 is expected to yield about $17.5 billion (at December 2008 metal prices) in 20 years life span of a single nodule mine-site. In order to recover 3 million tonnes of nodules, an area of 300 sq km only will be mined annually (i.e. <1 km2/day) for an optimum abundance of 10 kg/m2. However, during mining, large quantity (22 tonnes/day) of sediments associated with nodules would be resuspended that could lead to certain environmental impacts on the benthic ecosystem. Several small-scale benthic impact experiments in the Pacific and Indian Oceans, have given some insight into the possible environmental impacts and the restoration processes, but the possibility of extrapolating these findings to a commercial mining scale remains an issue to be considered. An estimated capital expenditure of $1.05 billion and operating expenditure of $4.2 billion for a single deep-sea mining venture will have to be weighed against the availability of mineral ores on land as well as the metal prices in the world market. None-the-less, development of technologies for mining and metallurgical processing, as well as formulation of regulations and guidelines for potential ?contractors? to mine these minerals have been progressing consistently. These coupled with recent efforts by certain ?entrepreneurs? to initiate mining of seafloor massive sulphides in the EEZ of certain countries, indicate the continuing interest and support the perception that such deposits could well be the future sources of metals. This paper analyzes the current status and discusses the economic, environmental, and technical issues that need to be addressed for sustainable development of deep-sea minerals.

Jan 1, 2010

By John Halkyard

Deep ocean mining is experiencing a rebirth following many years of low levels of activity. Large scale mining is being projected as just over the horizon. A lot has been made of the advances in deep water oil and gas developments over the last thirty years, and how this technology is directly applicable to ocean mining. The authors present their views on this from a perspective of a legacy of participating in the development of manganese nodule mining systems in the 1970s, followed by thirty years in the deepwater oil & gas arena. While it is true that great advances have been made in subsea technology, the differences between mining and oil and gas recovery should not be diminished. Fundamentally, oil and gas are stored in compact reservoirs under pressure. Any intervention leads to flow of the material up a pipe to the surface. The seabed hard minerals are stuck in place, either adhering to sticky pelagic sediment (nodules) or bonded together as hard rock (massive sulfides). The minerals require complex machinery in order to be extracted, sized, concentrated and lifted to the surface. Once at the surface the ore must be dewatered, de-fined and transferred to shore for processing. The overflow from this dewatered product must return to the sea in an environmentally satisfactory manner. These steps involve technology unique to mining that has to be addressed in a methodical fashion before commercial mining systems can be designed. The presentation will discuss the critical technical challenges of deepsea mining and thoughts on different routes to commercialization. The program will address the critical technical challenges, as perceived by the authors, and steps required to address them. Alternate development programs will be discussed focusing on nodules and sulfide. Keywords: manganese nodules, polymetallic sulfides, ocean mining

Jan 1, 2011

By H. L. Gibson, U. Schwarz-Schampera, Mark Hannington

Ancient ore deposits provide important clues for the understanding of the origin and distribution of modern submarine hydrothermal systems. An analysis of the formation conditions, tectonic settings, and preservation of ancient seafloor mineral deposits from the recent geological past to the late Archean sheds light on the time-space relationships and diversity of mineral deposit types likely to be found in the modern oceans. Microplate tectonics that characterized ancient ore-hosting greenstone belts were strikingly similar to those active in volcanic arc environments of the western Pacific today. In such complex settings, oblique collisions, opposing subduction zones, and rapid changes in stress regimes (e.g., from compressional to tensional and back to compressional) were common, causing juxtaposition of diverse styles of mineralization. The world-class base metal deposits of the late Archean Abitibi greenstone belt of Canada, for example, were formed within a relatively short time span of ~20 m.y., in response to successive arc rifting, back-arc basin development, and exhumation of accretionary complexes along major arc-parallel crustal-scale faults. Similar processes and environments are important settings for metallogenesis in modern submarine volcanic arcs. Active marginal basins of similar size and representing similar stages of evolution are well represented in the western Pacific today and contain a similar suite of mineral deposit types. Examples from the eastern Manus Basin and adjoining New Ireland Basin (PNG) and in the Lau-Tonga-Kermadec arc-backarc system illustrate these similarities. Certain gold-rich volcanogenic massive sulfide deposits at the southern margin of the Abitibi greenstone belt (e.g., Bousquet and LaRonde deposits in the eastern Blake River Gp.) may be important ancient analogs of newly discovered gold-rich black smoker deposits found along the active fronts of today&apos;s submarine volcanic arcs.

Sep 24, 2006

The seafloor occurrences of KODOS ferromanganese nodules can be classified into four facies based on the morphological types of nodules recovered and seafloor photographs. Facies A, B, and C are relatively unimodal whereas Facies D is bimodal in the size distribution of nodules. Both Facies A and B are highly covered by sediments, but Facies B is higher than facies A in nodule density. Facies C has a high density of small nodules and many traces of bioactivity. Facies D is irregular in nodule density, but occurs close to basement near scarps (Fig. 1). The transparent layer (TL) on subbottom profile records (von Stackelberg et al., 1987) is composed of three sedimentary units, which in cores are distinguished by color. The uppermost Unit I is postulated to be deposited during the past 0.21 Ma and the middle Unit II between 0.42 Ma and 0.21 Ma (MOMAF, 1997). There exists a hiatus between Unit II and Unit III. Unit III was deposited from 3.5 Ma to 1.5 Ma as determined by 10Be/9Be and/or 87Sr/86Sr dating (MOMAF, 2004). Internal textures observed on cut sections of nodules suggest four stages of nodule formation (Choi et al., 2000). The nuclei are either unbroken old nodules probably of hydrogenetic growth (1h and 2h) in Facies A and C, or nodule fragments probably of early diagenetic growth (2d) in Facies D, whereas there are both types in Facies B. The layers surrounding the hydrogenetic nodule nuclei are of hydrogenetic growth (3h and/or 4h) in Facies C, and are of early diagenetic growth (3d and/or 4d) in Facies A, B, and D. The layers surrounding the early diagenetic nodule fragments are mostly of early diagenetic growth (3d and 4d) in Facies A, B, and D. But hydrogenetic encrustations are also found as surface layers on the top in Facies B (Fig. 2).

Jan 1, 2005

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

In early 1990s, the Korean government has launched a deep-sea research program to secure the stable long-term supply of strategic metallic minerals including Cr, Cu and Ni. Through the pioneering surveys, Korea registered 150,000 km2 of Mn-nodule field in the Clarion-Clipperton area, the NE equatorial Pacific to the international sea-bed authority (ISA) in 1994. Following the ISA exploration code, the final exclusive exploration area of 75,000 Km2 was assigned in 2002, based on results of eight-year researches of chemicophysical properties of nodules, bottom profiles and sediment properties. Since that time, environmental studies, mining technical developments including robot miner and lifting system and establishment of smelting systems were accompanied with the detailed geophysical studies to decipher the priori mining area until 2009. Major points of the recent Korea Mn-nodule program are deployed on a commercial scale until 2015. In order to meet the goals, detailed 25,000 scaled mining maps in the priori area will be prepared, which can provide operation roots of the miner. In addition, an environmental-friendly mining strategy will be pursued based on the environmental impact test and environmental monitoring.

Sep 14, 2011

By D. S. Limpenny

Marine benthic habitats are vulnerable to the influence of a wide range of anthropogenic activities (e.g. sand and gravel extraction, dredged material disposal and trawling). Traditionally, benthic ecologists have relied on point sampling techniques such as grabs, corers and dredges to provide information on the physical nature of the substrates and their associated benthic fauna. However, information of this nature only relates to the specific point on the seabed from which the sample was collected and the interpolation of such data to predict the wider distribution of substrata and associated fauna may be unreliable. Our approach uses a range of acoustic, photographic and physical sampling methodologies to produce continuous acoustic coverage maps which can be used to assist with the interpretation of faunal distributions. This approach has been used to assess the impacts of marine sand and gravel extraction at the seabed at two sites off the east coast of England in the southern North Sea. The first study site (designated ?Area 222?) is located 20km off the southeast coast of England and was surveyed in 2001 using sidescan sonar, single beam bathymetry, seabed photography and also a 0.1m2 Hamon grab for the collection of benthos and sediment samples. The main objectives of this investigation were to provide an indication of the spatial distribution of the sediments and macrofauna in the wider area encompassing the dredged site, to evaluate the scope for the effects of marine sand and gravel extraction to extend beyond the boundaries of the site and to provide a wider geographical context for time series investigations. At this site, an acoustic basemap was utilised in conjunction with faunal sampling and photographic groundtruthing, to determine the nature and distribution of the seabed sediments and their associated features. Disturbances at the seabed arising from historic sand and gravel extraction activities were mapped, and this information was helpful in establishing biological cause and effect relationships. The acoustic basemap was also used to target biological reference sites against which the effects of adjacent man-made disturbances could be evaluated.

Jan 1, 2004

By John Parianos, Simon Richards

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

Jan 1, 2018

By Karsten Hagenah, Tor Jensen, Jens Laugesen, Øyvind Fjukmoen, Lucy Brooks

This paper discusses operational environmental threshold levels for exploitation of mineral resources in the deep sea. Such criteria are needed to be able to monitor and control deep sea mining with respect to the stringent environmental requirements that are needed. It is recommended to use existing environmental threshold levels for comparable underwater activities. Fields of application are mainly but not exclusively seabed mining operation activities under the governance of the International Seabed Authority (ISA). The threshold levels and limits mentioned in this paper are proposed recommendations based on other activities than seabed mining but are a proven and accepted approach in other maritime industry activities. An example of such other activities with proven and accepted environmental threshold levels are Oil & Gas exploitation activities in the sea. Background The first exploitation of mineral resources in international waters is coming closer. Presently regulations for exploitation for mineral resources in the Area are being developed by the International Seabed Authority (ISA). The ISA regulations will contain the framework related to environmental monitoring of exploitation. However, the regulations will not contain operational environmental threshold levels for the Contractor.

Jan 1, 2018

By R. D. Hamer

"The Atlantis II Deposit comprises metalliferous sediments (Zn+Cu+Ag+Au) accumulating in a composite, axial basin, 2,000m beneath the surface of the Red Sea. The basin contains warm, highly saline water. It is located approximately half way between Jeddah and Port Sudan within the Exclusive Economic zones of Saudi Arabia and Sudan. The Deposit was discovered in 1963 and evaluated by drilling in the 1970s and 1980s. This phase defined an initial resource of approximately 90Mt. More recent estimations have refined this figure to an Inferred Resource of approximately 80Mt (CIM compliant).The Mining Licence to develop and extract the Atlantis II Deep Deposit was granted to Manafai International Trade in 2010 by the joint Saudi-Sudanese Red Sea Commission. Manafai is poised to embark on a renewed phase of exploration and evaluation, including the completion of a Definitive Feasibility Study (DFS) and leading to the successful exploitation of the Deposit in a safe, environmentally sound, economically viable and socially responsible manner.The Deposit is forming in a complex basin adjacent the median rift, where sea floor spreading has operated during the last 5Ma. It is a Hydrothermal-sedimentary Deposit. The mineralised sedimentary rocks rest directly on sea floor basaltic rocks. They are produced by the exhalation of metal-rich, hydrothermal brines from fissures associated with the central rift and cross-cutting fracture zones. Up to 25m of metal-rich sediments have accumulated over an area exceeding 57km²."

Jan 1, 2017

By Jan M. Peter

Many massive sulfide deposits and districts around the World contain rocks that are variously referred to as ?exhalites?, banded iron formation (IF), ?Algoma-type? IF, ferruginous chert, jasper, jasperoid, cherty tuff, tuffite, tuffaceous exhalite, chloritic IF or sulfide IF. With few exceptions, such rocks are thought to be (in part) fossil hydrothermal sediments deposited from hydrothermal fluids vented into a submarine rift environment. Such hydrothermal sediments are associated with a wide variety of ancient base-metal sulfide deposits (e.g., Cyprus-, Besshi-, Kuroko-, and Broken-Hill-type deposits), and hydrothermal sediments are commonly associated with some of the largest base metal sulfide deposits in the world. Analogs of ancient hydrothermal sediments can be found around many modern seafloor hydrothermal deposits which themselves precipitate from high-temperature (350°-400°C) hydrothermal fluids. Hydrothermal fluids are quenched on contact with ambient seawater, and most of the metals are immediately precipitated to form the mound and chimney deposits. However, for kinetic and solubility reasons, not all metals and other species are immediately precipitated at the vent site. Fine particles (up to several hundred microns in diameter) of sulfides, sulfates, carbonates, oxides, silica, Fe-oxyhydroxides, clays, and other phases are precipitated from the hydrothermal fluids in the water column above the deposits. These particles or "particulates" are carried upward for several hundred meters in a buoyant hydrothermal plume (which is typically several hundred meters thick) until it reaches a neutral density, and disperses laterally from the vent site. Modelling of plume dynamics has shown that the majority of particulates are deposited by gravitational settling a few hundred meters from the vent site, and Å99% of particulates are deposited within 3 kilometers. However, signals from modern plumes have been detected even hundreds of kilometers from their source. Factors which can affect the morphology of the plume (and the resultant fallout pattern) include: particulate size, shape and density, bottom topography, and the direction and velocity of bottom currents.

Jan 1, 1998

By Gregory Abramov

Borehole Mining (BHM), a remotely-operated waterjet mining method (Figure 1), has recently achieved two major milestones. It was, for the first time, applied to the extraction of manganese ore and at temperatures below freezing. The 1St stage is a demonstration test that is now underway just north of Emily, Minnesota, where the manganese ore is located 100-160m below the surface and its reserves are estimated to be in excess of 500,000 tons. The deposit was discovered over 60 years ago but, due to the fragile and sensitive nature of this Land of 10,000 Lakes (nickname for the State of Minnesota) and strong environmental restrictions, the iron/manganese reserves were deemed unrecoverable and remained untouched until late 2010 when permission for a single-hole demo-test was issued by the local Department of Natural Resources.

Jan 1, 2011

By S. C. W. de Jong, E. de Hoog, J. M. van Wijk, S. J. Dasselaar

Introduction Technology development for sustainable, safe, reliable and efficient mining of polymetallic nodules in the deep seas requires careful design, thorough understanding and integrated testing of all equipment, physical processes and (sub) systems involved (Dasselaar et al [1]). Proceeding from Vertical Transport System (VTS) experiments at IHC laboratory scale by Van Wijk [2], with typical system dimensions of several meters, to prototype or pilot scale testing with typical dimensions of several kilometers, is a giant leap. Naturally, intermediate steps are required in order to mitigate the possible risks in the full-scale system’s (physical) processes. Within the EU program Blue Mining (2014-2018), possibilities emerged for performing experiments at intermediate scale: the so-called medium-scale vertical slurry experiments. Near Freiberg, Germany, the village Halsbrücke possesses a 140 meter deep empty vertical mine shaft, perfectly suited for housing the test setup. For this purpose, a 318 meter long 145 mm pipeline circuit was constructed, including both a 130 meter high vertical riser and fall pipe section. A purpose-built sediment injection and separation system was deployed, including a 55 kW centrifugal pump. The riser section has been equipped with sensors capturing pressure, temperature, flow velocity, volumetric concentration and flow visualization. The planning, modification and construction of the test facility site itself is described by Müller et al [3]. The present paper describes the objectives, experimental program, equipment, and the preliminary results. Publications on in-depth results are foreseen in the (near) future.

Jan 1, 2018

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

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

Jan 1, 2017

By Andrew E. Grosz

The United States is dependent on foreign imports for about 80 percent of its ilmenite, about 60 percent of its rutile, and virtually all of its monazite. Nearshore marine sand deposits and beach-complex sediments in the southeastern United States are important domestic sources of ilmenite, leucoxene, rutile, zircon, monazite, and a number of other less well known economic heavy-mineral (HM) species. Because global onshore reserves of placer titanium minerals may fall short of demand in as few as 20 years, offshore research in HM placers will become more important. The Atlantic Continental Shelf (ACS) defined by the shoreline and the 200-m isobath varies in width for the modern U.S. coastline from a fraction of a kilometer to about 150 km offshore of Cape Cod, Mass., and includes an area of about 3.91 x 105 km2. It probably contains 3-7 x 1011 m3 of sand and gravel which may locally contain commercially exploitable placer HM deposits.

Jan 1, 1986

By Julian Malnic

Transplanting the steps used in exploring and developing mineral deposits on land into the marine environment will help developers. While familiar to oil and gas explorers and many other sea-based industries, the marine environment is so alien to the 90s terrestrial miner that the phrase ?terrestrial mines in the sea? is useful for reinforcing the fundamental parallels in mining sulphides at sea and on land. As on land, the processes of ?pre-feasibility study? and ?feasibility study? will determine the economics of mining a deposit. For many, the step into the sea can detract from the need to follow these familiar and recognised steps used when any new deposit is found on land. The technology to mine sulphides in the 1500 to 2000 m depth range exists. Currently, it is not found in a single, integrated and commercially available system but every element available to build such as system is. Transplanting the thinking of the leaders of the terrestrial mining industry into the sea will perhaps be the greatest challenge and reinforcing the basic steps of discovery - pre-feasibility through to feasibility is the best way to achieve this. After all on land one doesn?t ask ?Can we profitably mine it?? before one can authoritatively answer ?What have we found??. Research by Nautilus Minerals Corporation suggests that the mining of seafloor massive sulphides (SMS) will not only be profitable but potentially lower in both capital and operating costs than prevail in most terrestrial deposits. Nautilus is also acutely aware that with the first SMS deposits under title, it will be setting the standards for seafloor mining into the new millenium. Indeed, we have trained on us not only the eyes of the mining industry waiting to see if SMS deposits really do offer radically better returns, but other stakeholders of the sea and the capital markets. Mistakes by any SMS developer could land all developers in ?hot water?. The rush to exploit our deposits for economic gain will be tempered by ensuring there is adequate public debate and consultation for our environmental code. Failure in any facet of a marine mining development could set back the move to the ocean floor.

Jan 1, 1998

By Mark D. Hannington

Seafloor polymetallic sulfides have been found in diverse volcanic and tectonic settings on the ocean floor at water depths ranging from 3700 meters to <1500 meters. More than 100 occurrences of hydrothermal mineralization have been documented (including Fe-oxide deposits, Mn-crusts, metalliferous sediments, and massive sulfides), but high-temperature hydrothermal activity and large accumulations of polymetallic sulfides are known at fewer than 20 different sites. Chemical analyses of samples from these deposits indicate that they contain important concentrations of Cu, Zn, Ag, and Au, comparable to those of massive sulfide deposits on land. However, the lack of sufficient data concerning the distribution, size, and bulk composition of seafloor deposits precludes a meaningful assessment of their resource potential.

Jan 1, 1994

By Tatiana ?. Sedysheva, Vladimir V. Ivanov, Michail E. Melnikov, Irina A. Pulyaeva

"INTRODUCTIONHydrogenetic Fe-Mn crusts are ubiquitous in the ocean basins and play an important role in marine mineral-deposit research because of their widespread occurrence and high concentrations of valuable and rare metals. Directed research, which started in the last quarter of the 20th century, has provided significant results, with substantial amounts of data produced on Fe-Mn crusts structure, composition, and distribution in the global ocean [3, 4 - 8]. Now, commercial interests gain more and more attention. Mining systems are being developed which involve fragmentation of the crusts and their separation from the substrate. The effectiveness of such activities greatly depends on physico-mechanical characteristics of the crusts and rocks on which they form. This determines the importance of the engineering geological study of the objects.This article comprises the results of the engineering geological studies of the crusts samples (72 samples) and their underlying rock substrates (75 samples), which were carried out during the research cruises 6-06, 6-07, 6-08, 6-13 (2006-2013) on the Magellan Seamounts guyots in the Western part of the Pacific Ocean by the specialists of the State Scientific Centre Yuzhmorgeologia [10 - 13, 19, 20]. The authors of the article directly participated in the studies mentioned above.MethodsEngineering geological studies were carried out on board of the research vessel Gelendzhik and in the laboratories of NPA «Sevmorgeologiya». The studies involved the determination of the following parameters:"

Jan 1, 2017

By Steven D. Scott

The source of ore metals for base and precious metal volcanogenic massive sulfide (vms) deposits has been debated for decades. Metals can be obtained from high-temperature sea water-rock reactions in subseafloor circulatory hydrothermal systems, or provided by the magmatic fluids that are degassed from magma. The magmatic signatures are largely erased in the hydrothermal system by the overwhelming, long-term circulation of seawater. Melt inclusions in phenocrysts (plagioclase, olivine, pyroxene) of volcanic rocks provide an effective means of understanding the potential for a magmatic contribution to the ore-forming fluids. We present results of a melt inclusion study on the volcanic rocks that host active seafloor hydrothermal fields in the eastern Manus immature back-arc pull-apart basin of Papua New Guinea and an Ordovician-age back arc in New Brunswick, Canada that hosts the ?giant? (330 mmt) Brunswick #12 vms ore deposit. A fluid phase is typically observed in cavities within melt inclusions, indicating that the magma was saturated with volatiles prior to its eruption. The fluid is CO2-dominated with lesser H2O and CH4 in melt inclusions of mafic volcanics and is H2O-rich in felsic volcanics. Tiny crystals and amorphous precipitates (recrystallized at Brunswick #12) of Fe, Ni, Zn, Cu and Mn chlorides, sulfides and oxides coat the walls of the vapor cavities. The crystals include magnetite, magnesite, calcite, anhydrite, gypsum, barite, pyrite, chalcopyrite, halite, silicates and apatite. At Manus, the compositions of the precipitates on the bubble walls of melt inclusions are similar to those found in the vesicles in the matrix glass of the same sample. The ore metals in the volatile phases changed from Ni+Zn+Cu+Fe ? Cu+Zn+Fe ?Fe+Zn (+Pb?) as the magma evolved from basalt, basaltic andesite ? andesite, dacite ? rhyodacite, rhyolite. Glass of the melt inclusions compared to that of the matrix of the rocks from Manus have significantly higher concentrations of H2O (av. 1.64 vs 0.7wt%), Cl (av. 2500 vs1300 ppm) and S (av. 900 vs 100 ppm) suggesting that these volatiles were extensively exsolved from the magma. A minimum of 1.0 to 1.7wt% of magmatic volatiles is estimated to have been degassed before and during the eruptions. The focused discharge of a magmatic fluid as a result of pre-eruptive degassing could be responsible for the metals in the sulfide deposits on the seafloor. If 1 km3 of magma were emplaced in a shallow chamber, then the associated magmatic fluid would be 35.1 million tonnes. If this fluid contained 2.3 wt% Zn and 7.2 wt% Cu (Yang and Scott, 1996, Nature), a total of 0.8 million tonnes of Zn and 2.5 million tonnes of Cu would be to the hydrothermal system.

Jan 1, 2005