Search Documents

By Eric J. Foell

Recognizing that the planned commercial exploitation of polymetallic nodules in the deep sea should be accompanied by environmental studies in order to protect this largest and least understood ecosystem of our planet, the German Ministry for Research and Technology has since 1989 funded a longterm and large-scale disturbance-recolonization (DISCOL) experiment in the abyssal Peru Basin of the equatorial South Pacific Ocean. The circular study site is located at 4150m depths and encompasses about 10km2 of relatively flat, heavily sedimented sea floor with low (< 15%) nodule coverage near an existing German nodule mining exploration license area. The RV SONNE, a large and well-equipped multi-purpose research vessel, served as platform for all environmental cruises conducted to date. The initial DISCOL expedition (SO-61, Feb.-March 1989) was carried out in two legs. During DISCOL 1/1, a study site was selected, a pre-disturbance baseline assessment was undertaken, and sea floor disruption was begun using the "plow-harrow", a uniquely designed disturber device towed repeatedly across the circular study area. During DISCOL 1/2, disturber deployments continued until the device had created 78 criss-crossing and partially overlapping tracks along which nodules were essentially plowed under while sediment from up to 15cm below the seabed had been turned over and exposed at the surface. In addition to the obvious within disturber track impacts, sediment mobilized by plowing drifted off with the prevailing near-bottom current and redeposited downstream, blanketing nearby areas not directly disturbed. Immediately after the disturbance phase, an initial post-impact sampling series was performed. The DISCOL Experimental Area (DEA) was revisited about six months (DISCOL 2, SO-64, Sept. 1989), three years (DISCOL 3, SO-77, Feb. 1992), and seven years (ATESEPP SO-106, Jan.-March 1996) after disturbance to collect further post-impact samples, monitor changes in the benthic community and follow the recolonization process. In addition to benthic community studies, plankton investigations were initiated during the third DISCOL cruise (SO-77) and continued during three further cruises (SO-78, SO-79 and SO-80/2) in 1992.

Jan 1, 1996

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 Mikhail D. Ageev

The paper concerns with some questions of Autonomous Underwater Vehicle (AUV) control system design, which allows a motion at rough undersea terrain. The AUV advantages reveal itself completely during exploration of such objects as seamounts and reefs area. These objects are characterized by steep slopes (30 degrees and above) and chaotic situated obstacles (rock debris, pinnacles, escarpments). Uses of other technical facilities for operating in such formations are difficult, dangerous or impossible. These regions take an interest due to the presence of iron-manganese crusts. Modern AUV can estimate density of mineral by means of still camera or video recorder. For this reason the vehicle has to move with the distance of 3-5 meters from seabed. Under such conditions micro- and mesorelief presents a considerable danger for AUV. The AUV can bypass underwater obstacles in the various ways. However, in any case AUV motion will be characterized by intensive maneuvering on various speed (from 0 up to 1.5 m/s), circular change of tractive force vector and, hence, a circular flow about the hull. So, AUV is equipped with the propulsion system, which provides free modes of motion. AUV control system (CS) has tri-level structure to allow a motion in a rugged seabed terrain. According to the generally accepted categorizations, CS includes execution, coordination and strategic levels. The strategic level contains the goals of AUV mission. Obstacles avoiding and route choice are realized by means of simultaneous maneuver in vertical and horizontal planes. Sonar system is used for data acquisition about obstacles. It consists of a few echo-sounders with fixed directivity pattern. The route choice algorithm operates at two lower levels of CS. Basic (?reflex?) functions of spatial motion are realized within the execution level and considered in the paper. The choice of motion modes is carried out at the coordination level of system. All accessible navigating information (the data from flight sensors and from multichannel echo-sounder systems) is used for this purpose. In addition the bypass of characteristic types of obstacles is carried out with the help of basic motion modes combination. The modeling results of bypass of various typical obstacles, and also their combinations are described in the paper.

Jan 1, 2011

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 Chan Min Yoo, Jung-Keuk Kang, Wonnyon Kim

Recently high-resolution paleomagnetic age determination of ferromanganese crust in less than millimeter scale has been successfully carried out using a superconducting quantum interference device microscopy magnetometer (SMM). However, it has not been clearly identified how the crust is keeping ancient geomagnetic field records. Here we try to identify magnetic mineralogy of the crust obtained in the Magellan Seamounts, the West Pacific (~20 °N). As a record, age of the crust used in this study is extended to ~10 Ma at ~40 mm depth and ~28 Ma at ~100 mm depth, respectively, based on the combination approach of SMM measurements, Be-isotope and Co-chronology. Thermal demagnetization revealed a Curie temperature of ~560oC, corresponding to (titano)magnetite. Component analysis of isothermal remanent magnetization identified a presence of two types of magnetite. Measurements of first order reverse curve showed a dominance of non-interacting single-domain magnetite, which is one of the intrinsic feature of biogenic magnetite. Although most of the magnetic particles on transmitted electron microscopy are covered by amorphous Fe-Mn minerals, some are observed as a prototype of biogenic magnetite showing a chain of ~10 nm sized magnetite cubes. However, a magnetite signal (i.e., Verway transition at ~ –120 oC) was not detected in low-temperature treatment probably due to surface oxidation of magnetite. Contribution of interacting magnetite of detrital origin is <30% throughout a crust. Interestingly, contribution of detrital magnetite is almost three times higher since ~10 Ma. At this boundary, a growth rate of the crust is double up and flux of other detrital signals, including Al, Mg, Ti and Zr, are also increased.

Jan 1, 2017

By J. R. Woolsey

The cost of an offshore exploration project is mainly dependent on the size of the vessel engaged for the work and increases dramatically with increasing size. Of the various factors influencing vessel size, the type and size of the sampling equipment is typically the principal consideration. This scenario is particularly true of shallow sampling programs employing a vibracore system. The problem develops when certain bottom materials such as densely packed fine sand require sampling. This type of material being one of the most difficult for the standard vibracore systems, with integral core liner, to penetrate to a reasonable depth of some five to seven meters. The problem is mainly related to the excessive cross sectional area of the cutting bit required to accommodate the core liner. The typical solution has been to apply more power to the vibracore drive head which results in a considerable scale-up for the entire system with attendant increase in vessel size. In order to reduce operating cost, M.M.R.I. has developed several systems for deployment from vessels in the 20 meter range. Two systems are modifications to the basic vibracore and a third is a vibralift system. Basically, one of the vibracore units is employed where core liners are required, utilizing a special jet bit designed to reduce the cutting pressure on the bit while not affecting the integrity of the core. The other designed for core extrusion on

Jan 1, 1986

By Randolph A. Koski

Recent investigations located at least six major massive sulfide deposits (dimensions measured in tens to hundreds of meters) within a 50-km-long segment of Escanaba Trough, the sediment-covered axial valley of southern Gorda Ridge. The sediment fill is intercalated silt and sand turbidites and hemipelagic mud with a maximum thickness of 500 m. Several volcanic edifices, spaced at approximately 15-km intervals along the ridge axis, penetrate and locally breach the sediment. The largest sulfide deposits form mounds and ridges on the steep flanks of structurally unstable sediment-capped blocks that have been uplifted above the volcanic edifices; both sediment and sulfide deposits are undergoing rapid erosion and redeposition. Although hydrothermal activity appears to be absent at most sulfide fields, 220°C fluids are discharging from the tops of sulfide mounds near 41°00&apos;N lat, 127°31&apos;W long. Recent pillow lavas and sheetflows erupted onto the sediment-covered sea floor less than 500 m away from the active vent field. The massive sulfide deposits have compositional characteristics that differ from deposits formed on sediment-free spreading axes. The Escanaba Trough deposits include Fe- and Cu-rich, Zn- and Pb-poor massive sulfide mounds, polymetal (Zn-Fe-Pb-Cu-As-Ag-Sb-Sn) sulfide vent structures, abundant barite-rich chimneys, crusts, and sinter cones, and thermogenic petroleum in the sulfide and sediment. Sulfate-rich crusts have high Au values ranging between 2 and 10 ppm. The unusual mineral assemblage at Escanaba Trough

Jan 1, 1989

By G. A. Tret’yakov, V. A. Simonov, I. Yu. Melekestseva, V. V. Zaykov, N. N. Ankusheva

The Kyzyl-Tashtyg massive sulfide polymetallic deposit is situated 120 km north-east of Kyzyl (the capital of Tuva Republic, Russia). It is located in the Ulug-O volcanic zone which is interpreted as the northern segment of the Kaa-Khem rift in Sayano-Tuva marginal sea, one of the Paleoasian Ocean margin (Fig. 1) [Zaykov, 2006]. Since its discovery in 1946 the deposit has been studied by many researchers. Significant information was published by Kuzebny et al. [2001] and Zaykov [2006] who proposed volcanogenic-sedimentary genesis. A single reference in English about Kyzyl-Tashtyg is available [Herrington et al., 1999].

By Charles L. Morgan

In a commercial effort to characterize deep seabed manganese deposits in the Clarion-Clipperton region of the northeastern tropical Pacific, Ocean Mineral s Company carried out 16 expeditions to the region between -1978 and 1981. During these cruises OMCO collected substantial data. Activities included acoustic profiling, video and photographic imaging of the seabed, and sampling of the deposits with dredges, box cores and free-fall grab samplers. In 1990 the samples, photographs, technical reports and computer data bases which resulted from this work were archived at the Marine Minerals Technology Center at the University of Hawaii. This preliminary examination of the collection focuses on the biological observations made from almost 10,000 photographs of the seabed and the manganese nodule size distributions and compositional data from the free-fall grab recoveries. Regional trends are evident in all three data types. The biological examinations of the seabed photographs show significant geographical trends, with greater abundances of organisms being noted in the northeastern extreme of the region, decreasing toward the southwest (11.4 to 2.7 observations per 100 m2; 460 to 190 g per 100 m2). The nodule size distributions suggest that the ratio of the nodule burial rates to growth rates systematically decreases over the same range (0.65 to 0.36 nodules buried per 1 cm of growth). Preliminary geostatistical analysis of the ore grade data show that, in addition to high local variability, some deposit

Jan 1, 1991

By Peter M. Herzig

In September-October 2002, shallow seafloor drilling using the 5 m-Rockdrill of the British Geological Survey and the German R/V Sonne has revealed critical information on the sub-surface nature of two distinct hydrothermal systems in the New Ireland fore-arc and the Manus Basin of Papua New Guinea. Drilling at the summit plateau of Conical Seamount (39 holes, 31 % recovery) south of Lihir Island in the central New Ireland fore-arc has confirmed the sub-seafloor extend of previously discovered surface gold mineralization (up to 230 g/t Au) and associated alteration to a depth of at least 4.5 m below the seafloor and further proven analogies to the giant Ladolam epithermal gold deposit on Lihir Island. Drill core samples of clay-silica alteration contain average gold grades up to 14.2 g/t Au over a length of about 30 cm (fire assay Lihir Gold Ltd. laboratory) and appear to be part of a more extensive gold zone located below a carapace of relatively fresh ancaramitic and trachybasalt. These samples contain a complex mineralogy including realgar, orpiment, galena, sphalerite, some chalcopyrite and pyrite, together with amorphous silica, and possibly cinnabar. In addition to high concentrations of gold, shipboard analyses indicate that the gold-rich samples contain high values of Pb, As, and Sb, which is a characteristic feature of a magmatic-hydrothermal style of mineralization and alteration.

Jan 1, 2002

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

"Advancing our knowledge about trace metal distribution and abundance provides insight into formation, alteration, and trace element enrichment processes of ferromanganese nodules and crusts. A fundamental understanding of these mechanisms, in turn, has implications for the selective recovery of critical metals and the development of sustainable hydrometallurgical techniques. Synchrotron-based X-ray Fluorescence (SXRF) is a powerful, state-of-the-art analytical tool that can examine geochemical features of Fe-Mn nodules and crusts, such as abundance and distribution of trace elements, in an integrated and efficient manner. By correlating trace element composition and Mn oxidation states in these highly complex samples, it can be determined whether these parameters are related to the Mn oxide mineralogy (vacancy content of crystal lattice) and chemistry.In this study, eleven Fe-Mn nodule and crust samples from three circum-Australian locations – the South Tasman Rise, Lord Howe Rise, and Coral Sea – were analyzed at the Australian Synchrotron, Victoria, Australia. Micrometer-scale spatial resolution of geochemical features, such as concentric growth structures and element distribution, was achieved with high sensitivity (Fig. 1). For instance, Ni could be detected at 10's of ppm to 1 wt% levels. Information on other redox-sensitive trace elements, which are present at 10-1000 ppm levels (e.g., Cu, Co, Ti), were gained by means of fully quantitative elemental composition maps."

Jan 1, 2017

By Kristian Drivenes, Steinar L. Ellefmo, Kurt Aasly, Ben Snook, Przemyslaw B. Kowalczuk, Rolf Arne Kleiv

"Since Ellefmo et al. (2014) published resource estimates of undiscovered seafloor massive sulfides (SMS) on the Arctic Mid-Ocean Ridge (AMOR), there has been an increased focus on establishing new knowledge about exploitation technologies for such deposits. This also includes understanding the process mineralogical properties of typical SMS deposits.The part of the AMOR that lies between Jan Mayen and the Svalbard Islands and is located within Norwegian jurisdiction and, as such, investigating the potential for mineral production from hydrothermal vent fields has been seen as strategic. The AMOR has been explored for active hydrothermal vent fields since early 2000s (Pedersen et al., 2010b). One of the active vent fields discovered, Loki´s Castle, is located in the northern part of Mohn´s Ridge. This vent field was first described by Pedersen et al., (2010a) and consists of two mounds, each approximately 100-150 m diameter and 20-30 meters high, hosting several active chimneys, up to 11 m high.Loki´s Castle has been selected as a case site in order to study the properties of typical SMS occurrences with respect to possible future deep-sea mining activities. As part of the MarMine cruise in 2016, the Loki Castle was visited and sampled for e.g. mineral characterization and mineral processing analyses. In total, more than 500 kg rock samples were collected using ROVs, and intended for further research (Ludvigsen et al., 2016). In addition to sampling mineralized rock fragments, survey data like bathymetry, magnetics and Underwater Hyperspectral Imaging (UHI) was collected using Automated Underwater Vehicle (AUV)."

Jan 1, 2017

By Randolph A. Koski

Since 1985, numerous constructional sulfide-sulfate deposits in the form of mounds, pinnacles, chimneys, and sheets have been located between 40°45&apos; and 41°05&apos;N latitude in Escanaba Trough, the sediment-covered axial valley of the Southern Gorda Ridge. Single-channel seismic data indicate that three volcanic edifices up to 6 km in width penetrate as much as 500 m of turbidites that fill the valley; pillow and sheet flow lavas are exposed on the sea floor where these volcanoes breach the sediment surface. Observations from deeply towed camera systems and submersibles show that the largest hydrothermal deposits occur along the step-faulted northern flank of the central volcanic edifice and on the peripheries of steep-sided, sediment-capped hills, approximately 1 km wide and 100 m high, that rise above the valley floor. The sulfide deposits are highly oxidized, eroded, and partly buried by unconsolidated sediment; aprons of sulfide talus extend downslope from the mounds. Two types of sulfide have been sampled by dredging and submersible. The predominant mound and chimney material is pyrrhotite-rich massive sulfide with low amounts of Zn, Pb, Cd, and Ag. Coarse-grained zones with high porosity mark the location of myriad fluid channelways. Thin crusts of barite associated with pyrrhotite-rich sulfide have Au contents up to 2 ppm. Zoned fragments of polymetallic (Fe-Zn-Pb-Cu-As-Ag-Sb) sulfide dredged from a single site near 41°01&apos;N latitude are part of a chimneylike vent structure with a

Jan 1, 1988

By P. Halbach

Hydrothermal activity is well known from many locations on most mid-ocean ridges, but no hydrothermally mineralized area had yet been found at the ultraslow spreading southwest Indian Ridge up to October 98 when the Japanese RV Yokosuka with the submersible Shinkai 6500 investigated this area. A massive sulfide field was discovered near 27°51S / 63°56E in the 11th segment west of the Rodriguez Triple Junction. The Free University of Berlin had joined this cruise and taken over the responsibility for the study of the respective sulfide mineralizations. Hydrothermal minerals were sampled during two dives at a water depth of 2940 m close to the summit of an axial volcanic ridge called Mount Jourdanne. Massive sulfides occur on the seafloor as small smooth mounds with an average area of about 5 m2. Their surfaces are weathered and have a reddish to brownish colour. In addition to these mound-like structures, small tube-like chimneys were observed; these chimneys rise approximately 30 to 40 cm above the floor and are less than 10 cm in diameter. No indications of hydrothermal fauna could be detected. All the hydrothermal features are spatially related to faults and smaller fissures controlled by an E-W trending graben system crossing the summit region of the submarine volcano. Such tectonized areas are generally considered to be ideal for hydrothermal activity because they may have both a magmatic heat source in the deeper underground as well as pathways for the fluid circulation.

Jan 1, 2002

By Peter Halbach

Hydrothermal activity is well known from many locations on most mid-ocean ridges, however no hydrothermally mineralized area had yet been found at the ultraslow spreading southwest Indian Ridge up to October 98 when the Japanese RV Yokosuka with the submersible Shinkai 6500 investigated this area. A massive sulfide field was discovered near 27º51S / 63º56 E in the 11th segment west of the Rodriguez Triple Junction. The Free University of Berlin had joined this cruise and taken over the responsibility for the study of the respective sulfide mineralizations. Hydrothermal minerals were sampled during two dives at water depth of about 2940 m close to the summit of an axial volcanic ridge called Mount Jourdanne. There massive sulfides occur on the seafloor as small smooth mounds with an average area of about 5 m2. Their surfaces are weathered and have a reddish to brownish colour. In addition to these mound-like structures, small tube-like chimneys were observed. These chimneys rise approximately 30 to 40 cm above the floor and are less than 10 cm in diameter. No indications of hydrothermal fauna could be detected. All the hydrothermal features are spatially related to faults and smaller fissures controlled by an E-W trending graben system crossing the summit region of the submarine volcano. Such tectonized areas are generally considered to be ideal for hydrothermal activity because they may have both a magmatic heat source in the deeper underground and pathways for fluid circulation, respectively.

Jan 1, 2001

The chemical composition of the nodules varies with the type of manganese minerals and the size and characteristics of their nucleus but those who have an economic interest have nucleus, generally : Mn> Fe> 6> Si> Al> Ba> Ni> Cu > Co. The Pacific Rim is an area of abundant occurrence of polymetallic nodules and the Pacific sea floor of the Clarion-Clipperton Zone (CCZ) is one of the most interesting areas in regard to the genesis of polymetallic nodules. Their abundance in the ocean floor is very variable, as there are places where they cover more than 70% of the ocean floor. The nodules can be found at any depth, but the highest concentrations are between 4000 and 6000. Hydrothermal processes that occurs near the East Pacific Rise at 21° N, may inputs metallic elements to nodules and to pelagic sediments, especially in regions close to the dorsal, as a greater influence hydrogenetic processes are present westward Metals such as Cu, Co, Ni, Sn, Fe, Mg, Pb, Zn and Ba show a relationship with the East Pacific hydrothermal activity and sea currents carry these metals in solution to the Clarion-Clipperton fracture area, where there are hydrogenic metals sources (Al, Fe and Mn).

Sep 14, 2011

By Peter E. Halbach

The Central Indian Ridge (CIR), the boundary between the African and Indian plates, forms a SSE trending mid-oceanic accretionary system in the equatorial Indian Ocean (Fig. 1), extending to the northerly Carlsberg Ridge spreading center, and terminating at the Rodrigues Triple Junction (RTJ; 25°30&apos;S, 70°06&apos;E) by intersection with the Southwest Indian Ridge (SWIR) and the Southeast Indian Ridge (SEIR). Crustal divergence of the CIR proceeds at intermediate rates; a progressive increase of ocean floor accretion towards the south is documented: the present half spreading rate and ridge trend change from 1.80 cm/a and N142° at the equator to 2.73 cm/a and N152° north of the triple point. The topography of the central rift zone is rather smooth compared to slow spreading analogues such as the SWIR, but slightly more rugged than the SEIR. The rift valley is 500-800 m deep, 10-15 km wide and usually well defined. The inner floor, 2-4 km in width, is relatively flat along the axis and more variable in cross section, and lies at 2700-3200 m depth. Off set fracture zones striking generally N60° . in southern portions of the CIR and laterally displacing median valleys by as much as 8 km are often bent, uplifting crustal sequences up to several hundred meters. The length of individual spreading segments varies between a few and several tens of kilometers. The vertical displacement on normal faults are larger while lineaments are shorter than those of the faster spreading SEIR. The direction of lineaments measured on the southwestern and northeastern flanks of the southern CIR are N154° and

Jan 1, 1994

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 Timothy F. McConachy

Magmatic-hydrothermal activity in the South-West Pacific and SE Asian island arcs during the Tertiary has created a premier copper-gold province with numerous, commercially attractive base and precious metal deposits. This activity continues to the present day, especially in submarine sectors of those arcs where modern technologies enable direct observation of ore-forming processes in action. Until recently, however, the volcanic island arcs of Indonesia escaped such attention. The Indonesia-Australia Survey for Submarine Hydrothermal Activity (IASSHA), involved three cruises with KR Baruna Jaya VIII, focused particularly on the Sangihe arc; Tomini Bay, Sulawesi, including the vicinity of isolated Colo volcano; and the Sunda Strait including the neighborhood of Krakatau volcano. IASSHA 2001 and 2003 cruises studied the arc and behind-arc sectors of the Sangihe volcanic island chain extending northwards from Quaternary volcanoes on the northeastern tip of Sulawesi, near Manado, to the Kawio Islands near the border with the Philippines (Fig. 1). This chain lies above a west-dipping Wadati-Benioff seismic zone whose subduction trench is obscured by accreted sediments and mélange, forming the Talaud-Mayu ridge. West of the main active chain and extending northwards from Manado there is a subparallel ridge (The Manado Line) surmounted by a number of high (>2000 m) seamounts of uncertain age.

Jan 1, 2005