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By Mayumy Amparo Cabrera-Ramírez

Polymetallic nodules are a widespread resource in the Pacific Ocean, particularly in the areas of Clarion-Clipperton (Cronan, 2000). The most abundant mineral phases are forme d by iron and manganese oxides, with minor elements such as nickel, copper, cobalt, molybdenum and rare earths elements (Cronan, 1977; Cronan and Moorby, 1981; Iyer and Sharma, 1990; Mangini et al. 1990; Banerjee et al. 1991). In the Clarion-Clipperton Zone (CCZ), several authors mention that there are three main mineral species of manganese oxides, which have been recognized and which are associated with different processes of formation: todorokita (Mn2+, Ca, Mg) Mn3 4+ O7. H2), vernadite dMnO and birnessite enriched in Fe and (Na, Ca) 0.5 (Mn4+, Mn3+) 2O4. 1.5 H2O. In nodules of hydrothermal origin have been found todorokite, birnessite, vernadite, goethite and pyrolusite. Although there are many oxides and hydroxides of manganese and iron in amorphous and microcrystalline phases that make up the bulk of the nodule (Frondel et al. 1960; Cronan 1977; Dymond 1981; Calvert and Piper, 1984; Aplin and Cronan, 1985; Martin and Lallier, 1993; Achurra et al. 2009), identifying specific mineral phases is difficult due to the intergrowth of different phases and associated detrital material.

Sep 14, 2011

By Anthony Wakefield

Dredging tends to be either horizontal or vertical. In each case solids have to be disengaged from the deposit, mobilized, acquired and elevated or translated. One means of elevation is the airlift. Elevation and translation of essentially granular material nay be by jet pump or centrifugal pump. Any of the three types may be used on its own. The airlift and jet pump may he combined for vertical transport and the centrifugal and jet pumps for predominantly horizontal. Both suction point and pipework must have a means of deployment from the surface or from a submerged vehicle or merely a diver. An airlift is an energetic system, having a source of energy and a means of storing it. It therefore will be difficult to prevent oscillation -surging. A centrifugal pump has a characteristic that bends over at low flow rate and is therefore intrinsically unsuitable for pumping solids. The result is blockage, operation at high velocity and correspondingly high wear rates or operation at low concentration of solids and correspondingly low efficiency. The jet pump is intrinsically exceptionally stable but has a low hydraulic efficiency. The jet pump-airlift hybrid prevents or reduces surging and increases system efficiency away from the optimum depth for airlift operation. Delivered solids concentration is increased. The jet pump-centrifugal pump hybrid totally prevents pipeline blockages and increases the productivity from a given pipeline size. For a given energy input the average production is typically doubled. For example, the Indian River Delaware bypassing pipeline transmits an overall day-in-day-out average of 500t/h (tonnes) of sand down a 10.86" diameter line.

Jan 1, 1998

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 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 Alexey Musatov, Georgy Cherkashov

Based on geochronological data it was confirmed that hydrothermal discharge has an episodic character: active and inactive periods of the seafloor massive sulfides (SMS) formation alternate (Cherkashov et al., 2017). There is an assumption of correlation of the periods of magmatic and hydrothermal activity with the stages of glaciation (Lund et al., 2016). During the cold periods, the level of the ocean was reduced from 70 to 150 m depending on the glaciation scale (Spratt, Lisiecki, 2016). As a result, the hydrospheric pressure on the upper mantle decreased and could provide increased magmatic and hydrothermal activity (Lund, Asimow, 2011). This assumption is confirmed by the correlation of warming and cooling stages with increasing of hydrothermal input to the bottom sediment near hydrothermal fields. According to data (Lund et al., 2014, 2016; Middleton et al., 2015) the peaks of hydrothermal activity, expressed in the layers of metalliferous sediments at the East Pacific Rise and the Mid-Atlantic Ridge, roughly correspond to the last two periods of cooling (20 and 60 ka). To test this hypothesis, we tried to compare the sequence of warm and cold periods in the Pleistocene with the dating of SMS reflecting the periods of hydrothermal activity. Results SMS samples were obtained from 12 sites within the Russian Exploration Area at the MAR segment 12-20°N. The results of dating 198 samples by the 230Th/U method demonstrated the absence of correlation between hydrothermal activity periods in different hydrothermal fields (Cherkashov et al., 2017). It was proposed that each field has its own evolutions scenario. Considering this point, only the oldest SMS dating for each field which fixed the beginning of hydrothermal activity was selected for comparison with the cold/warming periods.

Jan 1, 2018

By Kira Mizell, James Hein

"INTRODUCTIONThe majority of studies on the genesis of ferromanganese crusts focus on the adsorption and accumulation of metals, and therefore cations, especially those of economic interest. From these studies, a first-order electrochemical model has been proposed based on the zero point of charge of the manganese and iron oxides at typical seawater pH, which assumes that positively charged ions will bind to the negatively charged manganese oxide phase and neutral and negatively charged ions will bind to the slightly positively charged iron oxide phase (e.g. Koschinsky and Halbach,1995; Hein et al., 2013). While the theory behind this model is sound, and it has been consistent for many elements, other elements may not follow the model (Koschinsky and Hein, 2003), and thus requires additional investigation and validation. As a new approach to understanding element accumulation in ferromanganese crusts and to test the proposed electrochemical model, this study investigates the surface chemistry of the halogens, which occur as negatively charged ions in seawater and have high and consistent concentrations in seawater.ResultsBulk Halogen ConcentrationsTo determine the distribution of halogens in ferromanganese crusts, an initial dataset of 24 FeMn crusts (24 bulk and 19 layer samples) from throughout the global ocean, including the Arctic and the Southern Oceans, has been analyzed for chlorine and fluorine content using ion-selective electrode. Although both Cl and F are conservative in seawater, their content in crusts shows striking variability (Cl: 326 - 13310 ppm; F: 146 – 1048 ppm for non-phosphatized crusts) and has no obvious geographic relationship to ocean basin and no correlation with water depth, latitude, or longitude. We plan to have bromine concentration data to present at the time of this conference."

Jan 1, 2017

By Paul C. Rusanowski

Mining is a waste intensive industry, oftentimes producing hundreds of kilograms of waste rock and tailings for every gram of metal recovered. Disposal of mine tailings is a major concern in most mining operations. In Southeast Alaska the steep terrain and high seismic hazard province limits cost effective opportunities for land disposal of tailings. The lack of infrastructure and long travel distances generally limits secondary utilization of tailings, as well. Since the mines are located close to tidewater, submarine tailings disposal is an attractive option for tailings management. At the present time the EPA will not issue a permit that authorized marine tailings disposal from any mining process that includes flotation technology. Upland disposal is the "Best available technology" and must be used. Consideration of submarine disposal is generally precluded because the tailings are contaminated with fluids from the flotation process. However, when developing technological solutions to minimize environmental disturbance, destruction, pollution, and risk, submarine tailings disposal deserves another evaluation. In Southeast Alaska it may be the "Best available technology" based on an assessment of all issues and concerns in these mining projects.

Jan 1, 1991

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

This paper describes 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 activities where such are existing. 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 is coming closer. At the moment 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 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 Raymond Kaufman

While there is no immediate worldwide shortage of hard minerals, the consumption of natural resources is constantly increasing, and there are ominous predictions of shortages to come. Means of meeting rapidly increasing demands are being implemented. These include such methods as exploration and discovery of new ore bodies, development of new mines, increasing production at existing mines, working or reopening known deposits of lower grade ore and tailings, recycling old materials, and developing more efficient and less wasteful processes to convert ores and metals into useful products. The United States, although itself mineral-rich, depends in large measure on imports for many key minerals and basic materials derived therefrom. According to the Department of the Interior, the U. S. depends upon imports for more than half of its supply of six of the basic thirteen raw materials required by any industrialized society - aluminum, chromium, manganese, nickel, tin, and zinc. By 1985 the country will also depend upon imports for more than half of its iron and tungsten, and by the year 2000 imports will have to supply more than half of the copper, potassium, and sulfur that it requires.

Jan 1, 1975

By Alexander Malahoff

The most exciting frontier in Ocean Technology is represented by a new class of Marine Bioproducts, the source of which lies in marine microorganisms. The microorganisms include microalgae, bacteria and archaea. These organisms represent very diverse, adaptive life forms and in their metabolic processes use carotenoids, polyunsaturated fatty acids, ultraviolet blockers, as well as a wide range of enzymes that are pivotal in the production of new pharmaceuticals and nutraceutical products. These organisms cover a wide spectrum of ocean environments, from the shallow to the deep, from the normal to the extreme. The technological challenge is in the identification of candidate organisms, in the screening for valuable enzymes, and in the industrial production. A whole new range of collecting strategies involving submersibles, ROVs and in situ ocean floor instrumentation is emerging. New non-polluting industrial chemical processes involving the use of photobioreactors and extremophile bioreactors for breeding and monitoring these organisms in neo-farming technology is emerging. The commercial value of these candidate products is immense, as is the range of potential organisms. The dimension of this new industry is global. The Marine Bioproducts Engineering Center (MarBEC), funded by the National Science Foundation (NSF), has been established at the University of Hawaii. The vision of MarBEC is to develop a seamless research system stretching from undergraduate education to industry for the purposes of producing valuable marine bioproducts outside of the normal chemical factory production. MarBEC is uniquely and strategically placed in the Pacific to explore, find, and adapt highly bioactive marine micro-organisms found in the tropical ocean. We have watched the increasing need by the ever-

Jan 1, 2000

By Richard Mills

Autonomous Underwater Vehicles (AUVs) are proven technologies used across market segments for survey, exploration and environmental monitoring tasks. When coupled with other autonomous platforms or sensor packages AUVs become part of an holistic system approach to exploration and environmental assessment and monitoring. Recent developments have seen AUVs deployed remotely with instantaneous access to data via the cloud. Our goal is to deliver the capabilities of each of these elements and present a cohesive data set with automated processing tools over a cloud based interface. nmanned Technology AUVs The HUGIN AUV System is the most commercially successful AUV ever built. Operated as a single vehicle, or as part of a swarm, HUGIN’s area coverage rate is unrivalled. Equipped with a comprehensive sensor package including Kongsberg’s synthetic aperture sonar, it collects a data set. Some of these data are processed in-mission to enable operators to readily access it when the vehicle is recovered. HUGIN is well suited to mining survey and exploration. Capable of reaching 6000 metre depths and conducting missions greater than 60 hours, HUGIN collects seabed sonar imagery, sub-bottom profiles, laser and camera images plus environmental data, with sensors running concurrently.

Jan 1, 2018

By Irina A. Pulyaeva

Hydrogenetic 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. Detailed study of several seamounts has given confidence about the scale of Fe-Mn crust development and their characteristics. Now, commercial interests gain more and more attention. However, at the same time some theoretical questions related to Fe-Mn crust history including controls on metal sources and concentrations have not yet been answered. Here, we present the overview of age, composition, distribution, and geological setting of hydrogenetic Fe-Mn crusts from Pacific and Atlantic seamounts and discuss the geological evolution and conditions that led to the formation of potentially economic concentrations of metals. The age, composition, and distribution of Fe-Mn crusts in the Atlantic and Pacific oceans were determined by using a Fe-Mn deposits database compiled from our original data, published papers, published databases, and other international sources. Comparative analysis of Fe-Mn deposits from the Atlantic and Pacific oceans shows that there are similarities in basic characteristics of crust formation in both oceans. Simultaneously, there are significant differences in the scale of Fe-Mn crust distribution and composition that can be explained by differences in geological settings and characteristics of the deposition environment.

Jan 1, 2011

By James R. Hein

Ferromanganese oxyhydroxide crusts (Fe-Mn crusts) precipitate out of cold ambient seawater onto hard-rock surfaces at water depths of about 600-4000 m throughout the ocean basins. Fe-Mn crusts concentrate most elements in the Periodic Table above their mean concentration in the earth&apos;s crust (continental plus oceanic crust), except for the major rock-forming oxides and also notably gold and palladium. Tellurium is concentrated greater than any other element relative to its earth&apos;s crust mean (about 1 ppb). For example, mean contents of the elements heretofore known to be most enriched in crusts, Mo, Tl, Sb, Co, Mn, Bi, As, Se, and Pb are enriched 100 to 1000 times over their earth&apos;s crust mean, whereas the mean Te content in Fe-Mn crusts is enriched about 50,000 times. However, the distribution of Te in the earth is poorly known. Estimates of the mean Te content of the earth&apos;s crust range from 0.36 to 10 ppb, with 1 ppb being the most commonly cited mean content (compilations in Levinson, 1974 and Govett, 1983). If we took the highest estimate of 10 ppb, then Te would be enriched in Fe-Mn crusts five times more than the next most enriched element, or 5000 times the estimated maximum mean earth&apos;s crust.

Jan 1, 2000

By Philomene Verlaan

This study examines the possible relationships between compositional variability in non-hydrothermal manganese nodules and large-scale environmental parameters. In the central SW Pacific (145-180° W and 20-O° S) the level of primary productivity, the rates and proportions of carbonate, silica and organic matter supply to the sediments, and the position of the seafloor relative to the Calcium Carbonate Compensation Depth (CCD) appear to directly influence nodule composition. Four zones of nodule composition are apparent. These zones correlate fairly well with the level of primary productivity in surface waters, as estimated by satellite-based measurement of chlorophyll content. The observed correlations between surface productivity and nodule composition are consistent with the contention that the dominant source of several transition metals in these deposits (i.e , Mn, Ni, Cu. and Zn) is provided by removal of fine-grained particulate matter from the water column by biological means. Subsequent decay of organic matter in sediments augments the content of these metals in the nodules through oxic and sub-oxic diagenesis. The opposite behavior of Fe and Co content may in part result from mineralogical and dilution effects.

Jan 1, 2000

By Robert G. Ditchburn

The NW caldera hydrothermal vent field at Brothers volcano, of the Kermadec-Tonga arc, has associated massive sulfide mineralization. This includes an abundance of black smoker chimneys that contain significant concentrations of copper, lead, zinc and gold (de Ronde et al., 2005; de Ronde et al, 2010, under review). [ ] The oldest volcanic massive sulphide (VMS) samples recovered so far from Brothers have been dated using radiometric methods at GNS Science and found to be c. 1000 years old. By contrast, a volcanic cone that has formed in the southern part of the caldera has no associated VMS. Only elemental sulphur and Fe-oxide crusts are present here, samples of which have been analysed for their trace elements. From d34S values of sulfates and native sulfur, and the volume of gas (dominated by CO2 and H2S) discharging at the cone site, elements being deposited here are considered more directly magmatic in origin (de Ronde et al., 2005; 2010 under review). It has been discovered that deep-seated changes in volcanic activity at Brothers affect the NW caldera and cone site simultaneously, though the mineralogy at each site is so very different. Thus, the cone site is being studied to determine if elements being deposited there can be used as predictors of potential future VMS mineralisation as similar sites have been found at other volcanoes along the Kermadec arc and elsewhere. The frequency of these deep-seated magmatic events is considered important in the formation of Cu-Au-rich mineralization along arcs. The analysis of Fe within resulting hydrothermal plumes (surveyed by surface vessels), and trace elements in rock and mineral samples, are used to help determine the influence of magmatic contributions to the hydrothermal system. To verify that plumes are a reliable proxy for hydrothermal events depositing iron on the seafloor, Fe-oxide crusts from Brothers volcano cone have been dated to see if their emplacement coincides with highly Fe-enriched plumes in the water column. The radiometric dating techniques developed for barite-rich VMS, i.e. using 228Ra and 226Ra, were unsuitable for the Fe-oxide crusts because 210Pb was the only isotope detected by gamma spectrometry. Therefore, new techniques using 210Pb, 10Be and arsenic have been established.

Jan 1, 2010

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

By Sebastian Ernst Volkmann, Felix Lehnen

"INTRODUCTIONWhile today’s mine planning of land-based ore deposits follows methods, which are well established, mining standards for the deep-sea have not established. Having gained a basic understanding of geological settings, there is still a lack of tools and methods to assess and plan future mining projects in the deep-sea. In the framework of the “Blue Mining” research project (2014-2018) technologies and methods for the exploration and exploitation of deep-sea minerals are developed that will bring deep-sea mining a step closer. The “Blue Mining” project receives funding from the European Commission (EC; Framework Programme 7; GA No. 604500) and addresses all aspects of the value chain in the field of deep-sea mining. The project philosophy is that deep-sea mining is planned and executed in the most responsible manner: Ensuring societal benefits and profitability at acceptable resource utilization and lowest possible environmental footprint (Volkmann 2014).Inspired by the high-tech farming industry, a concept to mine seafloor manganese nodules (SMnN) was developed. Mining is considered to be similar to the potato harvest on land (Figure 1), which involves mining a field partitioned into long, narrow strips (Volkmann and Lehnen 2017). The proposed mining system composes of one mining support vessel (MSV), one or two self-propelled, crawler-type seafloor mining tools SMT(s) and different types of underwater vehicles. The MSV follows the mining route of the SMT(s), picking up the about potato-sized nodules from the seafloor. The ore is pre-processed in situ and is lifted on board of the MSV, where the ore is dewatered and loaded onto bulk carriers for transport to the purchaser. Processing and refining of ore is not subject of “Blue Mining” research."

Jan 1, 2017

By T. E. Sedysheva

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

Jan 1, 2010

By Burrows D. R.

Metal-rich sediments precipitating from hot saline brine pools were first discovered in 1965 in the Red Sea.1-2 The subsequent discovery of high temperature black smokers and associated massive sulphides in 1977 at latitude 21oN on the East Pacific Rise3 came more as a confirmation than a revelation. Formation of massive sulphides through precipitation from circulating sea-water had been predicted by Oftedahl in 19584, and the mechanisms well evaluated in basaltic-hosted Cyprus-type 5 and in Kuroko-type deposits.6,7 Sea-floor exploration from 1977 through the 1980?s in sediment-starved mid-oceanic ridge (MOR) settings had little impact on land-based exploration. This is primarily because: a) MOR spreading centres were recognized as poor analogies to even Cyprus-type basalt-hosted deposits; b) their preservation potential was limited due to rapid oxidation and c) the metallic deposits studied were small and therefore not directly comparable to the far larger ore bodies on land. More recently underwater mineral deposit research has focused in a variety of back-arc environments associated with felsic submarine volcanism, environments more similar to those predicted for the formation of Kuroko-type deposits (e.g. Okinawa Trough, 8 Lau Basin, 9 Manus Basin, 10 Aeolian arc, 11). Most studies, while scientifically interesting, were hampered, in general, by a lack of good descriptive data, a reliance on isolated grab samples, and a lack of sub-surface observations. This research has therefore had only limited direct impact on exploration strategies with the possible exception of research conducted in areas where faulting provided enhanced vertical exposures. 12

Jan 1, 2011