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By Cornel E. J. de Ronde

Brothers volcano (34°51.7?S, 179°03.6?E) is a large caldera volcano that forms part of the active Kermadec arc south of 32° S, NE of New Zealand. It is an elongate edifice striking NW-SE that is ~11-13 km long by 7-8 km across. The caldera has a basal diameter of 3-3.5 km and is surrounded by 350-450 m high walls with the floor 1,850 m deep. A volcanic cone of dacite composition rises 350 m from the caldera floor and partially coalesces with the southern caldera wall. Much of the caldera construction and the location of the hydrothermal vent sites are controlled by intersecting basement structures. Three hydrothermal sites have been recognized at Brothers; NW caldera, SE caldera and cone. Multiple hydrothermal plumes were mapped from the bottom of the caldera upwards to a depth of 900 m and originate from two of the sites; one on the NW caldera wall the other atop the cone. Analyses of these plumes show that the two vent sites are chemically distinct. The cone site itself hosts three distinct vent fields (summit, upper flank, NE flank) that in 1999 had plumes (mainly from the summit) containing relatively high concentrations of gas with a shift of -0.27 pH units (proxy for CO2) and H2S concentrations up to 4,250 nM, particulate Cu (PCu) of 3.4 nM, total dissolvable Fe (TDFe) of 4,720 nM, TDMn up to 260 nM and Fe/Mn values between 4.4 and 18.2. However, in 2002 plumes from the summit vent field had noticeably lower concentrations of PCu (0.3 nM), TDFe (175 nM), and Fe/Mn values of 0.8, although similar TDMn (220 nM) and shift in pH (-0.22) suggesting a state of flux for this site. By contrast, plumes originating from the NW caldera site have much less gas with a pH shift of -0.09 units and no detectable H2S, TDFe up to 955 nM, TDMn up to 150 nM, and Fe/Mn values of 6.4, and have not changed their composition over the same three year interval indicating a more chronic hydrothermal system. Plume d3He results show helium is decoupled from more near-surface vent fluid sources although a shift in R/Ra values from 6.1 ± 0.5 in 1999 for the combined vent sites to 7.2 ± 0.1 in 2002 indicates a less radiogenic input of helium over three years, suggestive of a greater magmatic input to the system.

Jan 1, 2004

By Michael R. Gipp

Marine Mining Inc. is currently exploring for marine alluvial gold and diamonds on a prospecting licence over a concession that covers 10,000 km2 of the continental shelf of Ghana. The boundaries of the concession extend from 0 30'W to 2 40'W, and between the shoreline and approximately the continental shelf edge north of 4 30'N. This concession extends from Kikam Beach in the west, to Senya Beraku in the east, a distance of approximately 240 km, and seaward an average of about 40 km. The concession is entirely underwater, with the exception of the estuaries of the Ankobra and Pra Rivers. Ghana has been a large source of alluvial gold, with historical production exceeding 25 million ounces. Southwestern Ghana is characterized by Precambrian rocks, which have been folded into a number of NE-SW trending synclines and anticlines. The most significant feature of the Birimian rocks is the presence of evenly spaced gold-bearing greenstone belts. They are 10-15 km wide, separated by about 90 km, separate basins filled by folded metasediments and granitoids. The rivers that enter the concession drain most of the exposed gold-bearing belts of Ghana. Given that approximately 2 km of erosion has taken place since the Mesozoic, and that gold mines on these belts boast proven reserves of over 55 million ounces, it is likely that large amounts of gold have been eroded out and carried to the sea. Coastal fractures, related to Precambrian structures reactivated during Mesozoic rifting, are responsible for the physiography of the coastal area, which consists of high-relief horsts separated by grabens that have been occupied and infilled by rivers or by finer sediments during times of elevated sea level. These fractures were loci of gold mineralization during the Precambrian, and are the source of alluvial gold in rivers confined by them.

Jan 1, 1998

By Yves Fouquet

Recent exploration demonstrates that hydrothermal systems related to upper mantle ultramafic outcrops are common in the modern ocean. Most sites are located on slow spreading ridges with a low magmatic budget. Volcanogenic Massive Sulfide (VMS) deposits, associated with basalt, along the Mid Atlantic Ridge (MAR) are volcanically controlled near the topographic highs at the center of the segments. Three preferential settings are identified for ultramafic sulfide mineralization: 1) Off axis, on rift valley walls, near the amagmatic ends of the segments; 2) Non-transform offsets and 3) Ultramafic dome structures at the ridge transform fault intersection. The upper surface of these domes is often interpreted as a detachment fault. Three processes are considered for driving hydrothermal cells in ultramafic rocks: 1) regional heat flow at the ridge axis 2) Cooling of a deep gabbroic intrusion and 3) exothermic heat produced during serpentinisation. Along the Mid Atlantic Ridge, four types of ultramafic hydrothermal mineralization are observed: 1) High temperature (>350°C) sulfide mineralization related to low pH fluids, (ex. The Logachev field at 14°45? N and the Rainbow field at 36°14 N); 2) Medium temperature carbonate chimneys (<100°C) related to high pH fluids (ex. The Lost City site at 30°N); 3) Low temperature diffuse venting associated with extremely high methane discharge and pervasive alteration and silicification of both volcanic and ultramafic rocks (ex : The Saldanha field at 36°34 N); 4) Stockwork mineralization and quartz veins with sulfides related to gabbroic intrusions within ultramafic rocks (15°N). When compared to mineralization in a basaltic environment, sulfide deposits are enriched in copper, zinc and specific elements related to an ultramafic rock source such as Ni and Co. They are also significantly enriched in gold which, unlike in basaltic environments, has a bimodal occurrence both in low temperature Zn-rich assemblages and in high temperature Cu-rich mineral assemblages. The Cu-Zn-Co-Au deposits along the Mid Atlantic Ridge seem to be more common than on land where few similar VMS deposits are known. We consider that ultramafic VMS deposits on slow spreading ridges constitute a specific marine type of mineralization that is less easily than back arc deposits, incorporated into the continent during obduction processes.

Jan 1, 2004

By B. J. Bluck

Diamond mega-placers, in order to rank amongst the primary diamond deposits, are defined as => 70 m carats at =>95% gem quality. There is only one mega-placer known and that is found along the coast of southwestern Africa fringing the Kaapvaal craton. Placers are classified as residual when they are left on the craton, transient when being eroded into the exit drainage and terminal. Terminal placers, in being the final depositories of diamonds off the craton, have the greatest probability of being a mega-placer and such is the case in the placer deposits near the Orange River mouth, southwestern Africa. There are four main groups of conditions leading to the development of a mega-placer: the craton, the drainage, the nature of the environment at the terminus and the timing. The craton, in its role as the producer of diamonds is significant in respect to its size, diamond-fertility, the degree to which diamonds from successive kimberlite intrusions have been retained there and their availability to the final drainage yielding the mega-placer. Cratons in being buoyant have a tendency to leak diamonds into surrounding basins but in being incompressible often have orogens converge onto them resulting in lost sediment being returned as foreland basin fills. In order to concentrate a bulk of diamonds the drainage basin has to be large with a high proportion of it on the craton. The drainage yielding the mega-placer should ideally not have been preceded by older drainage and other systems that may have robbed the craton of earlier diamonds. The exits of diamonds from the craton need to be few in order to focus on their supply and the drainage network needs to be efficient in order to remove the maximum volume of diamonds off the craton. This efficiency and the focused termination is best achieved by the rejuvenation of a pre-existing drainage network. The drainage should be young enough to yield host sediments friable enough to allow brittle diamonds to be recovered from them.

Jan 1, 2004

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 Alexander Malahoff

The new ship-submersible system with R/V Ka&apos;imikai-o-Kanaloa as a mothership and the PISCES V as the submersible completed its first season of dives. The dives involved deployment of the PISCES V in the Hawaiian Islands between the months of July and October 1996. Submersible deployments up to depths of 2,000 meters in sea states up to a high three were made. The new hook and clasp deployment and retrieval connection for PISCES V to the telearm was shown to be an effective system for handling the PISCES V with the A-frame. The shipboard multibeam survey and seawater sampling capability proved to be especially effective in re-mapping the summit of the submarine volcano Loihi following a major volcano-tectonic event and for following the source and configuration of the new hydrothermal plume. Following the earthquake swarm of July 17 to August 18,1996, major changes in the geological setting of Loihi submarine volcano took place. Prior to the seismic event, the geology and structure of the summit of Loihi was represented by a platform-like area 8,100 meters long and 5,400 meters wide enclosed by the 1,200-meter depth contour. The summit was characterized by the presence of two prominent pit craters and eastern and western crater located at water depths of 1,100 and 1,370 meters, respectively. A hydrothermally active volcanic cone, named Pele&apos;s Vents, was located at a depth of 960 at the southern edge of the summit. The floor of the summit of Loihi was largely covered by prismatic talus, with interstitial hydrothermal clays. Pillow and tube lavas with volcanic cones 5 to 50 meters high were exposed along the axes of the southern and northern rift zones. The inner margin of the summit displayed fissures and normal faults with the downthrown component towards the center of the summit. The pre-earthquake structural data suggest a pre-caldera structural stage for Loihi. Maximum sustained hydrothermal activity observed on Loihi over the past 10 years existed at Pele&apos;s Vents with other sporadic venting occurs along the summit platform and along the south rift. Following the earthquake swarm, the hydrothermally saturated Pele&apos;s Vents cone gave way and slid into the inner pit crater. Subsequently, the observed above- bottom hydrothermal plume source deepened from 960 to 1,160 meters, possibly emanating from the same intrusive heat source as Pele&apos;s Vents. The observed inward collapse of the summit structures and subsequent opening of fissures gave rise to diffuse venting from the newly formed caldera-like depression with the bottom-hugging hydrothermal pool located at depth between 1,250 and 1,220 meters at the sites of the pit craters.

Jan 1, 1996

By Bjørn Eske Sørensen, Kristian Drivenes, Przemyslaw Kowalczuk, Kurt Aasly, Gavyn Rollinson, Ben Snook

Efficient and successful mineral processing is dependent on detailed knowledge of the materials and minerals that are to be separated and concentrated. Common bulk methodologies such as XRD and XRF are fast and easy, and can provide an overview of the mineralogy and bulk chemistry of the material. However, they will not provide any textural information. Knowledge of the often intricate interaction between minerals in seafloor massive sulfide deposits is crucial in plant design for mineral processing. Samples from the Loki’s Castle hydrothermal vent have been characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), optical microscopy, Scanning Electron Microscopy (SEM), QEMSCAN, Electron probe microanalyzer (EPMA), and Electron Backscatter Diffraction (EBSD). Processing experiments used froth flotation and leaching techniques. The typical line of operation in ore characterization is shown in Figure 1. Mineral processing may be commenced after any stage of ore characterization. However, it is ideal to have completed as many steps in the ore characterization as possible in order to have the most information of the initial feed material. The main economic minerals in the samples are isocubanite (CuFe2S3), chalcopyrite (CuFeS2), and sphalerite (ZnS), with minor galena (PbS) and trace amounts of Au and Ag. The minerals show complex intergrowth textures down to the nanometer scale. These samples exemplify the need for advanced microtextural analyses to adequately characterize ore material prior to processing. The complex textures hamper the use of flotation as an efficient technique, due to the inability to sufficiently liberate the different minerals and problems with selectively floating isocubanite. Thus, leaching was the preferred method for extracting metals.

Jan 1, 2018

By James R. Herring

An unusual combination of ten new, deep (-100 m) coreholes and an extensive high-resolution seismic reflection network enables us to produce a detailed study of the phosphorite resources in the Tertiary strata of the Georgia continental shelf. These strata are mixtures of a terrigenous facies, notably quartz and clay along with minor amounts of other aluminosilicate minerals, and of a marine facies, notably phosphorite and carbonate. Phosphatic sediments occur throughout the cores, however the richest phosphorite beds are in the middle Miocene (Serravallian) sediment, where they constitute up to 70 percent of the sediment mass. Major zones of phosphate enrichment occur chiefly at major unconformity boundaries (tops of Oligocene, lower and middle Miocene, upper Miocene, and lower and upper Pliocene) and at prominent intrastratal reflectors representing minor unconformities within units. Phosphorite co-occurs with the clay minerals, especially palygorskite, but correlates inversely with carbonate and detrital quartz, indicating a low-energy depositional environment. The clay minerals present in these strata, which have an environmental consequence on recovery of the phosphorite, are varying concentrations of smectite, kaolinite, mica, palygorskite, and sepiolite. Phosphatic resources have been determined within only the Miocene strata. Sediment volume for this unit to the 100 m isobath on the continental shelf has been established using the high-resolution seismic reflection network that has been calibrated using the deep coreholes. Phosphorite grains larger than 0.1 mm average about 40% of the sediment. In turn, most of the remainder of the sediment in this size range is quartz, which is separable from phosphate grains using conventional flotation techniques. Our estimate is that 300 Gt of phosphorite lie within the Miocene strata of the Georgia continental shelf.

Jan 1, 1994

By Robert M. Owen

Recent advances in coring technology and in the development of shipboard and/or in situ geochemical geochemical analysis systems have greatly improved our ability to collect and analyze exploration samples, particularly for marine placer exploration programs. The potential benefit of these improvements cannot be fully realized, however, until we also develop more efficient methods of data reduction and interpretation. Specifically, there is a need to provide prospectors with rapid and useful interpretations of the raw geochemical data so that they can exploit promising results and otherwise optimize the exploration program while the exploration vessel is still at sea. The goal of this project has been to identify and/or develop computer software which is capable of making the necessary data reduction calculations and which can be run on conventional desk-top computers. All work on this project has been supported through a research grant from MMTC-CSD to The University of Michigan. The first stage of this effort involved an evaluation of commercially available (i.e., "off the shelf") software to determine its suitability for use in marine placer exploration applications. Various commercial software packages, each purportedly capable of making different types of statistical and/or mathematical calculations, were tested by evaluating their performance in handling geochemical data sets representative of actual marine placer locations. These data sets include the positions and results of chemical analyses of suites of sediment samples collected from areas of known or suspected marine placers along the Bering Sea coast of Alaska. The evaluation of each commercial program involved a comparison between the results obtained from using the test program

Jan 1, 1991

By Akira Usui

Occurrence of hydrogenetic ferromanganese crusts has been well documented over inactive seamounts in the central and southern Pacific Ocean. It has been thus believed that the hydrogenetic crusts develop preferentially at water depths between about 800 to 2500 meters. In fact, according to the Manganese Crust Database (F. Manheim, 1988), only two occurrences are known at water depths below 5000 m out of 819 occurrences cited in the database. Unexpectedly, we found typical hydrogenetic ferromanganese crusts from deep-sea floors; 1) outcropping old volcanic basement over the Philippine Sea Plate (abandoned spreading centers and subducting old oceanic crusts) and 2) one from the slope of an abyssal hill in the Central Pacific Basin (Cretaceous deep-sea basin) at water depths ranging between 5200 to 6100 meters. We report their occurrences with submersible observations from Shinkai 6K, physical parameters (such as thickness of crusts about 2-4 cm in maximum), chemical composition, petrology of substrate, and results of Be-10 dating for some samples in comparison with typical Co-rich manganese crusts from the Central Pacific seamounts. The preliminary chemical and mineralogical analyses reveal that they are of typical hydrogenetic origin, and typical of iron-manganese oxide mineral, vernadite, slow and probably continuous growth, and lower content of Co than the Central Pacific seamount crusts. The occurrences and nature of the crusts indicate that deep-sea floors are also optimal for the growth of hydrogenetic crust even at 5000 m water depth or deeper, only if oxygenated deep waters are supplied and the sea-floor morphology keeps stable enough for significant geological time period. Additional details of chemical analyses will be prepared by November and to be shown in the conference.

Jan 1, 2001

By Michael J. Cruickshank

Marine minerals are more than an academic curiosity as they represent the most significant global source of mineral materials for economically and ecologically sustainable development for the future. Minerals research is traditionally carried out by industry and thus, in the United States at least, applied research in marine minerals may not get the share of government funding or attention that more exotic programs for space exploration or future global disasters engender. Two recent events have significantly changed the status of marine minerals. Discoveries made in the last thirty five years indicate that the potential for mineral occurrences in the oceans and seabeds, area for area, is as high as for terrestrial lands. On this basis the global mineral resource base has been recently increased by a factor of four of which three quarters is underwater. The recently enacted Law of the Sea has mandated what is probably the most far reaching re-distribution of natural resources in human history, and has resulted in a peaceful subdivision of seabed jurisdictions between the coastal nations of the world which should significantly affect future mineral markets and the balance of economic powers. Significant applied research efforts are ongoing for marine minerals as an adjunct to commercial production in southern Africa for diamonds; and in many other parts of the world for sands for beach and coastal protection. Forward planing, including research and development activities focussed on future commercial production of metalliferous oxides, continues in Korea, China, Japan, India, and with lesser activity, in the United States, United Kingdom, Germany and the CIS. Annual expenditures for this work amount to millions of dollars. In all cases the environmental aspects of commercial produc¬tion are a significant part of the research. Geologic studies on the occurence and distribution of metal sulfides at plate boundaries continue on a regional basis in the Pacific.

Jan 1, 1996

By Mikhail P. Torokhov

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

Jan 1, 2004

By 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 J. W. Jamieson

"The future of the marine mining industry is tied to the resource potential of the seafloor. Everything from economic feasibility, policy decisions and environmental impact assessments to extraction techniques and mining tool design rely on an understanding of the size, composition, and distribution of the deposits. Development and regulatory decisions must ultimately be tied to not only the grade and tonnage estimates of individual deposits or groups of deposits, but also an understanding of the uncertainty of these estimates. Here, we will discuss how seafloor massive sulfide (SMS) deposit grades and tonnages are evaluated, and the sources of the uncertainties associated with these values.TONNAGE UNCERTAINTYFirst-order tonnage (size) estimates for SMS deposits are primarily determined from calculating the volumes of material that occurs as positive bathymetric features on the seafloor. The extent of sulfide mineralization on the seafloor can be determined either from visual surveys (camera-tow, remotely-operated vehicle (ROV), or human-occupied submersible surveys) or from volume calculations of bathymetric features identified from digital elevation models of the seafloor, or a combination of both methods. For bathymetric models to be used to identify deposits in the absence of visual groundtruthing, data resolution of 1 m or less is generally required to confidently identify a feature as being hydrothermal in origin (as opposed to a volcanic or tectonic feature), and therefore near-bottom multibeam data acquisition (e.g., using autonomous underwater vehicle (AUVs) or remotely operated vehicles (ROVs) is required (Fig. 1). Specific characteristics of bathymetric features, such as shape, slope angles and surface roughness can be used to identify features of hydrothermal origin (Fig. 1). However, so far, bathymetric features mapped at a resolution of ~1 m cannot be relied upon to unambiguously distinguish a sulfide mound, and the additional use of multiple AUVmounted sensors, such as magnetometers, which can be used to detect hydrothermal upflow zones, or self-potential sensors, which detect electrical fields related to the oxidation of sulfide minerals, can increase the confidence that a bathymetric feature is indeed a sulfide body, without the need for expensive and time-consuming visual surveys (c.f. Petersen et al., this volume)."

Jan 1, 2017

By Jan M. Peter

Many of the Pb-Zn massive sulfide deposits of the Bathurst area in northern New Brunswick, Canada, are intimately associated with laterally continuous iron formation (IF) (Figure 1). This IF is a fossil laminated, exhalative, chemical sediment. Together, the IF and the Brunswick #12, Brunswick #6, and Austin Brook deposits (rightmost discontinuous horizon on Figure 1) are collectively referred to as the "Brunswick Belt". To date we have only studied the Brunswick Belt and have not examined the horizon along which the QSR, CNE and Flat Landing Brook deposits lie. The Bathurst area is underlain by the Tetagouche Group (Figure 2), a Cambro(?)-Ordovician sequence of metasedimentary and bimodal metavolcanic rocks that was intruded by mafic to felsic plutons and subsequently deformed during the Taconic Orogeny. The stratigraphic sequence consists of shales and greywackes that are overlain by carbonaceous shales and felsic volcanic and volcaniclastic rocks; these are in turn overlain by mafic volcanic and sedimentary rocks. The massive sulfide deposits and IF occur within the upper portions of the felsic volcanic rocks in close association with carbnaceous metasedimentary footwall rocks (Figure 2).

Jan 1, 1993

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

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

Jan 1, 2017

By 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 B. S. Ingole, S. Jai Sankar, A. B. Valsangkar, R. Sharma, B. Nagender Nath, N. H. Khadge, P. A. Loka Bharathi

After the simulated ‘mining’ experiment (INDEX) in the Central Indian Ocean (in 1997); the restoration of benthic environment was monitored for 4 years (2001-2005) at 5 locations in and around the test site and at 3 reference stations (20-80 km) from the test site. A comparison of long-term monitoring data with the pre-mining and post mining observations has shown that: • The concentration of silt fraction which was the highest (50-60%) at most locations during ‘pre-mining’ and ‘post-mining’ phases, had reduced (40-50%) during monitoring phases. • There was a corresponding increase in clay concentration (50-60%) during the monitoring phase, implying change in the size of sediment particles settling on the seabed, a trend that was also observed at the reference locations. • The initial increase in water content and decrease in shear strength after the experiment, which appeared to be returning to normal in monitoring-1 (2001), was reversed during subsequent monitoring phases (2002-2005), indicating changes in benthic environmental conditions. • Sediment organic matter and pore-water chemical data have not only indicated partial restoration of geochemical properties after the experiment, but also cyclic changes during the monitoring period.

Oct 15, 2007

By M. Ye. Melnikov

The report is about oceanic ferromanganese crusts ? covers of iron and manganese hydroxides developed over an opened rock of seamounts and rises. Ore bed parameters of crusts are understandable as their thickness and content of main economic components ? manganese, cobalt and nickel. All known results of research activity on ferromanganese manganese crusts point to that crust are characterized by notable variability of thicknesses and composition. It is possible to separate few levels of variability. The most evident is the first level of parameters variability, which is manifested in various regions of the Ocean, and connected first of all, with an age of submarine mountains, a host objects for a crusts. It was proved by many authors, that most powerful crusts are connected with submarine mountains of Cretaceous age. [1]. Crust thickness at the Magellan Seamounts reaches, for example 12-15 cm, sometimes exceeds 20-22 cm. Thicknesses of Hawaii Archipelago or Tuamotu crusts in 3-4 times less. Biostratigraphy studies of crustal sections at the Magellan Seamounts already show, that its main part started to form in the Late Paleocene. Four layers with well expressed features in structure and composition of a layer are separated in the section. From foot to top: Late Paleocene ? Early Eocene layer I-1, Middle-Late-Eocene layer I-2, Miocene layer II and Pliocene ? Quaternary layer III. Relics of more ancient Campanian ? Maastrichtian ore layer [2, 4] were discovered. It is evident for example, that Oligocene mountains could not be a host for two lower layers in the crust section.

Jan 1, 2010

By M. Ye. Melnikov

The report is about oceanic ferromanganese crusts ? covers of iron and manganese hydroxides developed over an opened rock of seamounts and rises. Ore bed parameters of crusts are understandable as their thickness and content of main economic components ? manganese, cobalt and nickel. All known results of research activity on ferromanganese manganese crusts point to that crust are characterized by notable variability of thicknesses and composition. It is possible to separate few levels of variability. The most evident is the first level of parameters variability, which is manifested in various regions of the Ocean, and connected first of all, with an age of submarine mountains, a host objects for a crusts. It was proved by many authors, that most powerful crusts are connected with submarine mountains of Cretaceous age. [1]. Crust thickness at the Magellan Seamounts reaches, for example 12-15 cm, sometimes exceeds 20-22 cm. Thicknesses of Hawaii Archipelago or Tuamotu crusts in 3-4 times less. Biostratigraphy studies of crustal sections at the Magellan Seamounts already show, that its main part started to form in the Late Paleocene. Four layers with well expressed features in structure and composition of a layer are separated in the section. From foot to top: Late Paleocene ? Early Eocene layer I-1, Middle-Late-Eocene layer I-2, Miocene layer II and Pliocene ? Quaternary layer III. Relics of more ancient Campanian ? Maastrichtian ore layer [2, 4] were discovered. It is evident for example, that Oligocene mountains could not be a host for two lower layers in the crust section.

Jan 1, 2010