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By T. Kuhn

The Logatchev hydrothermal field is situated on the east inner flank of the rift valley of the MAR at 14°45?N and is hosted by serpentinized peridotites and minor gabbronorites while basalts are subordinate. Hydrothermal precipitates recovered from the Logatchev field during a recent R/V Meteor cruise include massive chalcopyrite chimneys, massive pyrite crusts, silicified breccias, abundant secondary Cu-sulfides, red jaspers, abundant Fe-Mn-oxyhydroxides as well as atacamite and Mn-oxides (Kuhn et al., 2004). Previous results of hydrothermal fluid studies in the Logatchev field are somewhat at odds with theoretical models of ultramafic-seawater reaction. Butterfield et al. (2003) suggested that the Fe component of orthopyroxene plays the more important role compared to olivine in ultramafic-hosted hydrothermal systems. This consideration is supported by the recovery of large amounts of Opx-rich gabbronorites and orthopyroxenites in the Logatchev field (Kuhn et al., 2004). A possible tool to constrain the contribution of the different rock types (ultramafics, mafics, MORB) to a seafloor hydrothermal system is the systematic analysis of 187/188Os ratios of the host rocks as educts and the sulfides as products. For instance, abyssal peridotites mainly display low 187/188Os ratios (<0.127); in contrast MORB and gabbronorites have radiogenic ratios of >0.13 (Snow and Reisberg, 1995), orthopyroxenite has ratios of about 0.174 (Büchl et al., 2002) and seawater has an ever higher 187/188Os of about 1 (Sharma et al., 1997). Therefore, massive sulfides predominantly leached from ultramafic rocks should have Os isotopic ratios plotting on a mixing line between the ultramafic rocks and seawater (in a 187/188Os vs. 1/Os diagram), whereas those derived from MORB, gabbronorites and/or orthopyroxenites will be plotting on different mixing lines.

Jan 1, 2004

By Ivo Dreiseitl

Bottom sediment sampling by means of a box corer, as a direct method of deep seabed exploration for polymetallic nodules, is the most comprehensive way to obtain various types of geological information on points forming a network of stations. However, direct information is lacking from areas separating those stations and has to be approximated by interpolation or extrapolation, which leads to uncertainties. Sediment sampling with a gravity or piston corer can provide information on the superficial, up to 4 m thick, part of the sedimentary cover. As opposed to box coring, gravity or piston coring provides no information on nodule abundance. Information for unsampled areas can be gained by application of remote techniques of exploration. The techniques of choice in visualising nodule-rich fields, nodule-free areas, hard rock outcrops and other obstacles for seafloor mining involve using sonar and continuous deep sea (CDS) camera. Seafloor mapping can be rendered with two major sonar types: the side scan sonar used to obtain seafloor imagery and multibeam sonar for bathymetric data; the two types are usually combined and work with an intermediate frequency profiler. Photo-profiling by means of a deep sea towed camera provides a series of seafloor photographs, each supplemented with information on the area covered by each frame, including the nodule abundance. Remote techniques have been quite frequently applied by the Interoceanmetal Joint Organization (IOM) in nodule field exploration. Recently, geoacoustic techniques (side scan sonar + profiler) and CDS were applied for exploration of IOM?s first prime area H11 (5372 km2) on 6 transects. During the IOM-2009 cruise, a total of 295 km of geoacoustic transects and 344 km of photo-transects were surveyed. The data obtained were processed with the aid of earlier information produced by multibeam sonar surveys. The aim of this paper is to demonstrate the advantages of remote techniques, particularly with regard to application of the towfish device, for geological and geotechnical applications in exploration for polymetallic nodules.

Sep 14, 2011

By Akira Usui, Sayuri Kubo, Satoshi Tokeshi, Shingo Kato, Katsuhiko Suzuki, Teruhiko Kashiwabara

"INTRODUCTIONFerromanganese (Fe-Mn) crusts are a kind of marine chemical sediment composed of Fe and Mn oxy-hydroxides as well as small amounts of clastic sediments, which are ubiquitously found on the surface of slopes of seamounts and oceanic plateaus at depths from 900 to 5500 meters below sea level (mbsl). Fe-Mn crusts contain extremely high concentrations of useful minor metals such as Co, Ni, Te, REEs, and thus are expected as submarine mineral resources. Also, Fe-Mn crusts record the change of chemical compositions of seawater during last several tens million years, which allow us to obtain clues to clarify the paleoenvironmental conditions at the time of its deposition. However, occurrence, chemical compositions, microbial community and growth patterns of ferromanganese crusts are yet fully understood. Hence, a comprehensive study on the genesis of ferromanganese crusts, such as growth rates and enrichment processes of elements, is required to better understand their resource potential as well as their applications to paleoceanographic study.Based on the resource potential of ferro-manganese crust, the project entitled “Next- Generation Technology for Ocean Resources Exploration” was launched as one of the governmental projects to develop the exploration technology based on the scientific research on the submarine resources such as hydrothermal deposits (e.g., a poster by Kawada et al.), ferro-manganese crusts. We have made several research cruise to seamounts in the north-western Pacific such as Takuyo-Daigo and Takuyo-Daisan seamounts (Fig. 1) ."

Jan 1, 2017

By Sabrina Warwas, Thomas Kuhn

"Due to rising prices and increasing demand of raw materials over the last years, marine mineral resources including manganese nodules have become a focus of study for industry and science. Marine ferromanganese nodules consist of micro-layers of different chemical and mineralogical composition which incorporate metals of high economic interest (Ni, Cu, Co, Zn, Mo, Li, rare earth elements; Hein & Koschinsky, 2015).The varying composition of the layers depends on different growth processes, such as hydrogenetic (metal precipitation from the water column under oxic conditions; Mn/Fe = 3), diagenetic (metal precipitation from the sediment pore water) under oxic (Mn/Fe 3-10) or suboxic (Mn/Fe = 10) conditions; (Wegorzewski & Kuhn, 2014) or hydrothermal (metal precipitation from low-temperature hydrothermal fluids; Kuhn et al., 2003).METHODSIn this study, manganese nodules from three different locations of the Atlantic Ocean (Galicia Bank; Vema-Fracture-Zone and Brazilian Basin) were analyzed for their geochemical and mineralogical composition. Detailed information about the samples are given in table 1. The geochemical and mineralogical composition of bulk nodules were determined by XRF, ICP-MS/OES as well as XRD and the single micro-layers by high resolution analyses with electron microprobe and LA-ICP-MS."

Jan 1, 2017

By Andrea Koschinsky, Sophie Paul

"INTRODUCTIONOnce again deep-sea mining has been receiving a lot of attention in recent years. Industrial and political advancements also call for environmental baseline studies and analyses to aid the development of standards and monitoring protocols. As part of the EU research project “JPI Oceans: Ecological Aspects of Deep-Sea Mining”, the RV Sonne cruise SO242 to the Peru Basin revisited the DISCOL area that had been artificially disturbed in 1989. This offered the unique opportunity to study a deep-sea site 26 years after a disturbance similar to manganese nodule mining had been carried out (Figure 1). A comparison of a variety of undisturbed and disturbed sites shed light on the re-establishment of a geochemical equilibrium and a range of baseline values. This information can help to inform standard development for monitoring and mining purposes.Heavy metal data and its applicationResearch findingsDuring the cruise, disturbed and undisturbed surface sediment was sampled. The pore water analyses show that the 26 years old disturbance is not visible in the metal profiles and that the pore water reaches equilibrium through diffusive fluxes relatively quickly. The sediment, however, shows some differences between disturbed and undisturbed sites in the upper 20 cm, even after 26 years. Lower concentrations in the usually manganese-oxide rich top layer, variations and “unnatural” peaks in the manganese profiles, for example, suggest removal or mixing of the top layer (Figure 2)."

Jan 1, 2017

By Sung-Hyun Park

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

Jan 1, 2003

By Nicholas Dyriw, Georgy Cherkashov, Tamara Stepanova, John Parianos, Anna Firstova

"Seafloor massive sulfide (SMS) deposits are a new frontier in global metal resources. Hydrothermal chimney’s (black smokers) precipitate Cu, Zn, Ag and Au rich from hot fluids (>250°C) during interaction with cold seawater ~2-4°C. Here we compare the sulfide mineralogy and geochemistry of Cu-sulfide chimney samples from two different tectonic locations: Solwara 1, a Cu-rich, transitional arc-back arc (Arc-BA) type SMS ore deposit and; Ashadze-1, a Cu-rich, ocean ridge type SMS deposit (Hannington et al., 2011).This work represents the first stage of a project aimed at investigating and understanding the significance of high Cu concentrations in SMS systems. Comparing these particular systems is significant because they share critical similarities despite being located at different seafloor depths, hosted in different rocks and are located in two different endmember tectonic environments. Critical similarities include: 1) age of mineralization, ~6000 years to current (Firstova et al., 2016; Johns et al., 2014); and 2) high copper contents, with chalcopyrite dominating sulfide mineralization (Firstova et al., 2016; Lipton, 2012). The reason for high Cu concentrations in both of these locations is still not entirely understood. The youthfulness (<6000y to current) of both locations is important because it reduces the possibility of increased zone refining, allowing us to understand the source characteristics better. This research will advance our understanding of the copper systematics of SMS systems by investigating and comparing the mineralogical and geochemical signatures from two, Cu-rich, end-member type SMS sites."

Jan 1, 2017

By Gary J. Massoth

Are hydrothermal emissions from subduction-related volcanic arcs important to the total hydrothermal burden of the oceans? While historical observations of hydrothermal venting of fluids at mid-ocean ridgecrests, intra-plate hotspots, and backarc spreading centers are numerous, we remain poorly informed regarding the contributions from hydrothermal systems associated with oceanic submarine arcs. Here we report the chemical results from the first systematic assessment for hydrothermal activity at an intra-oceanic arc front. We discovered that 7 of the 13 submarine volcanoes that define a 260-km-long segment of the southern Kermadec arc north of New Zealand are hydrothermally active. Most significant here is that the chemical compositions of the various hydrothermal systems, inferred from back-extrapolation of observations of hydrothermal plumes, are diverse, and in many instances enriched in the concentrations of gases (e.g., CO2 and H2S) and metals (e.g., Fe and Mn) compared to effluents commonly discharged from mid-ocean ridges. If our results are generally representative of submarine arcs, whose global extent may equal one-third that of ridgecrests, the answer to our leading question could be a resounding yes in terms of both volume and chemical composition.

Jan 1, 2001

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 Robert M. Owen

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

Jan 1, 1989

By Andrew Bellamy

A thorough appreciation of the origin, formation, preservation and geometry of marine sand and gravel deposits is central in demonstrating that their extraction by dredging does not affect coastal processes or marine life. Geological evaluation underpins wave, tidal and sediment transport modeling and assists in predicting the nature and extent of seabed change during and after dredging. Marine sand and gravel deposits in the English Channel, southern North Sea and parts of the Irish Sea are of predominantly periglacial fluvial origin and record long histories of valley and floodplain cut and fill associated with Quaternary climatic and sea level oscillations. In the Bristol Channel, the influence of marine transgression and tidal dominance in sorting proglacial outwash deposits is evident in the distribution of sandbanks, scoured channels and gravel lags of this region. These deposits are relict and are unrelated to coastal sediment dynamics. Their extraction leaves seabed depressions which monitoring shows remain unfilled. The resultant offshore bathymetric changes and sediment removal in over 10 m water depth are not transmitted to the coastal zone as beach drawdown, wave height increases or sediment starvation. Applications for new aggregate dredging permissions in UK waters must be accompanied by an EIA and need to make a convincing case that the dredging will not affect rare or declining species and communities of marine life. Seabed recovery rates post dredging are now investigated and understood with reference to geological setting and the uniqueness of the sediment/biological character (biotope). Investigation of the continental shelf by the Industry and others reveals the large extent of gravel-dominated biotopes relative to commercially viable deposits.

Jan 1, 2004

By Huaiyang Zhou

It has been long known that manganese nodules occur more or less in some part of marginal seas in West Pacific Ocean. On the other hand, it is difficult to understand their distribution and the genesis as those nodule samples were collected mostly by dredge from the deep basins generally has much higher sedimentation rate than the open ocean. For example, the sedimentation rate in the South China Sea is about three orders of magnitudes than that in region of the Clarion-Clipperton Fracture Zone. In June of 2013, a small seamount (named as Jiaolong Seamount), consisting of southern part and northern part with a distance of about 3 km each other, was visited by DSV Jiaolong/RV XiangYangHong 9. It is discovered that abundant manganese nodules exist only on the surface sediment in the southern part with a water depth of about 3800 m to 3300m, on the platforms nearby an obvious crater where volcanic rocks exposed on the wall. There are no any nodules be observed on the sediment in the northern part of the seamount (about 100 m deeper than the southern part) and surrounding deep basin (approximately 4000 m in water depth). It is speculated that a source of core for manganese nodule and a dynamic sedimentation environment, are two major governors for the growth and distribution of manganese nodule in the marginal seas.

Sep 14, 2011

By Fernando JAS Barriga

The world-class Neves-Corvo deposits were intersected by drilling in 1977. They occur in the (Carboniferous) Iberian Pyrite Belt (IPB), Western Europe&apos;s largest stock of base metals (see Bamga, 1990, in Dallmeyer RD, & Martinez E, eds, Pre-Mesozoic Geology of Iberia, Springer-Verlag). Massive and stringer sulfides in the area sum up to about 200 Mt (109 kg), in five main orebodies (Neves, Corvo, Graca, Zambujal and Lombador). They include unique, extremely high grade copper and tin ores ( - 33 Mt Cu ores, -7.5% Cu, and -4 Mt Sn ores, -2.6% Sn, - 12.5% Cu). Also present are -50 Mt polimetallic ores (-6% Zn, 1.2% Pb, 64 ppm Ag). The remaining are relatively low grade pyritic massive and stringer sulfides (Cu < 2%. Sn < 1%, Zn equivalent < 4%). The geological setting is one of bymodal submarine volcanism, with predominant felsic, explosive volcanism and associated sedimentation (detrital and chemical), which took place on a shelf-facies, quartzite-phyllite basement (of Upper Devonian age). The plate tectonic setting has been the object of much debate. Current interpretations favour that the IPB volcanism took place in a tensional fore-arc region, associated with oblique subduction and collision (Silva et al., 1990, same volume as above). At Neves-Corvo there are many different ores, that may be grouped in four main types: fissural (at the base), breccia, massive (intermediate) and "ruban6 " (at the top). Fissural ores seem to correspond to stockworks in contrasting types of host rocks (gray to black shale, sericitic, chloritic and graphitic, and light gray volcanic rock). Massive ore may contain significant shaly gangue, at the base of individual orebodies, and silica-rich (cherty) varieties towards the top. The more sulfide-rich varieties predominate, and are usually well banded.

Jan 1, 1993

By Alexander Malahoff

Field observations and sampling of land-based and submarine hydrothermal and geothermal sites show a definite link between the geological setting, fluid geochemistry and specialized assemblages of microorganisms found at these settings. Three initial sites have been chosen as a basis for these studies. The first site is located on hydrothermal vents in pit craters on the submarine volcano Lo?ihi (Hawai?i) at a water depth of 1,300 meters. The second site is within the geothermally active vents, ponds and lakes of the Taupo Volcanic Zone of New Zealand. The third site extends along the chain of volcanically and hydrothermally active volcanoes of the Kermadec-Tonga arc and back-arc system. To focus our work in New Zealand, a geomicrobiology field and experimental center has been established in Wairakei, New Zealand, with the relevant genomics, proteomic and bioinformatics work being conducted at the University of Hawaii. As part of a partnership between the University of Hawai?i, the Institute of Geological & Nuclear Sciences (GNS) and Victoria University of Wellington, a new interdisciplinary graduate course in geomicrobiology will be taught at Victoria University beginning next year. Since mineral-microbial interactions have been occurring for the past few billion years and these interactions have led to where one generates the other, a metal-bacteria research program has been initiated at GNS using arsenic-gold and other metal-bacterial interaction processes as a research objective. In this research program, we have completed the full genome of a new species of marine bacterium Idiomarina loihiensis from the Lo?ihi hydrothermal vents and identified specialized microorganisms living in pH 0.3 geothermal vent waters of White Island, New Zealand. The multidisciplinary approach to study the process of accumulation of metals in the hydrothermal systems clearly shows the path of how bacterial-mineral interaction can precipitate metal deposits. These studies will lead to new avenues for biomining, bioremediation and the understanding of the origins of life.

Jan 1, 2004

By M. E. Williamson

From December 2004 through March of 2005 an extensive geophysical program was conducted to delineate polymetallic sulfide deposits in the Bismark Sea for a major mining concern. Deeply towed sidescan sonar, interferometric swath bathymetry, subbottom profiling, magnetic gradiometry, electrical resistivity, induced polarization. self-potential, gravimetry, water temperature/conductivity and towed video were among the methodologies tested against known occurrences of polymetallic sulfides in 1500 m -- 2200 m water depths. Known active and currently inactive sulfide areas were characterized using the various remote sensing techniques followed by survey with these same tools in other areas where they successfully discovered new prospects. Dredge sampling was used to ground truth both previously known sulfide areas and newly found deposits.

Jan 1, 2005

By Hyun Sub Kim

Subsea mineral deposit exploration aboard the R/V Onnuri was performed along the northern Central Indian Ridge (CIR) between 8°S and 17°S in December 2009 ~ January 2010 (09IR Leg01 and 09IR Leg02) and December 2010~ January 2011 (10IR Leg01, 10IR Leg02, and 10IR Leg03). Final goal of the expedition for the first Korean research cruise on mid ocean ridge system is to define seafloor massive sulfide ore bodies through searching the active hydrothermal vents nearby spreading centers as well as to elucidate the nature of spreading segments of the northern CIR area where no systematic survey have been operated before by mapping and sampling of volcanic rocks. The preliminary result of topographical interpretations of bathymetry clearly display ocean core complex between 10°S and 11°S. The ocean core complex is featured by topographic-high area with corrugated surface. Lineaments of corrugations of the ocean core complex are clearly perpendicular to abyssal hill direction which is triggered by symmetric-normal faults. Ocean core complex are favor for hydrothermal fluid path because of the long-lived faults. In further exploration, more detailed examination, including systematic CTD casting and tows, need to narrow down actual venting site around ocean core complex. Magnetic field survey is able to estimate the location of hydrothermal vents with the properties that high temperature of hydrothermal fluids over Curie-point can cause thermal demagnetization. In magnetization intensity map, most of low magnetization zones are located at the nodal point over the ridge axis and the ocean core complex.

Jan 1, 2011

By Robert M. Owen

Geochemical exploration for marine placers involves the acquisition, processing, and interpretation of geochemical data. Recent technological advances such as in-situ analysis systems and microcomputers have greatly improved our ability to acquire and process data, but their full benefits cannot be realized until we also develop improved methods for reducing and interpreting large amounts of raw geochemical data. Toward this end, our research has sought to identify existing and/or develop new geostatistical techniques for use in marine placer exploration. Each technique has been tested by evaluating its performance in the analysis of existing data sets. The data sets typically include the results of chemical analyses of suites of sediment samples collected from areas of known or suspected platinum and gold placers along the Bering Sea coast of Alaska. Results to date indicate that three geostatistical methods (subpopulation partitioning analysis, comparative factor analysis, and end-member compositional factor analysis) are useful in identifying elemental groups which can serve as "pathfinders" in the search for marine placers, and are also helpful in discerning the generic geochemical basis under lying observed statistical correlations between pathfinder elements and placer minerals. Existing methods of modelling sediment dispersal patterns have been examined with a view toward adapting them to the specific problem of understanding placer formation in

Jan 1, 1986

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 Harold Gibson, Ulrich Schwarz-Schampera, Ralf Freitag, Hendrik Mueller

INTRODUCTION Germany has a long history in marine research in the Indian Ocean. The first German scientific cruise started in 1964, followed by a series of state-sponsored research cruises between 1983 and 1995 leading to the first finding of polymetallic sulfides in the Indian Ocean. The research included regional bathymetric, geological, structural, volcanological, petrological and hydrothermal investigations along the Carlsberg Ridge and the Central Indian Ridge (CIR). Early environmental base line studies covered oceanographic and sedimentology aspects. In 2010, BGR took the initiative for the preparation of a license application for the exploration of polymetallic sulfides with the International Seabed Authority (ISA), and prospecting started in 2011 along the southern Central (CIR) and the northern Southeast Indian Ridge (SEIR) in the southwestern Indian Ocean (cruises INDEX 2011 on board R/V Sonne), INDEX 2012 (R/V Fugro Gauss), INDEX 2013/1-2 (R/V Sonne) and INDEX 2014 (R/V Pelagia). After three years of resource-oriented and environmental base line studies, BGR, in order for the Federal Ministry for Economic Affairs and Energy (BMWi), applied for an exploration license which was approved by and subsequently signed with the ISA in 2015. The license gave permission to start a detailed exclusive resource-oriented exploration program in the license area. The program includes the outline of potential ore deposits and a resource assessment but also extensive and detailed base line studies for the sustainable protection of the marine environment in the license area. The license contract has a fifteen years lifetime and may allow the application for a subsequent mining license. The exploration aims at the identification of inactive polymetallic sulfide deposits, formed below former discharge zones of hot hydrothermal fluids on the ocean floor (“black smoker” systems), by advanced and modern exploration techniques.

Jan 1, 2018

By Bonnie A. McGregor

The U. S. Geological Survey in cooperation with the Institute of Oceanographic Sciences (IOS), U.K., conducted a sidescan sonar survey of the U. S. Exclusive Economic Zone in the Gulf of Mexico from August 7 to October 22, 1985. A reconnaissance-scale view of 120,000 square nautical miles of sea floor seaward of the shelf-edge was obtained by using the GLORIA (Geologic Long-Range Inclined Asdic) sidescan sonar system. After these data were merged with GLORIA data from an earlier survey (1982) of the northwestern Gulf, a preliminary mosaic was constructed at a scale of 1:375,000. From this mosaic, we can identify morphologic features and interpret sea-floor processes. The extensive deformation of the continental slope seaward of Texas and Louisiana by salt tectonics has resulted in a complex pattern of basins and salt dome highs. One continuous meandering channel was identified in this portion of the Gulf, extending from the shelf edge to the Sigsbee Abyssal Plain. Bottom currents have reworked the sediments in this channel&apos;s levees seaward of the Sigsbee Escarpment, the seaward edge of the salt front, suggesting that this channel may no longer be actively transporting sediment. Talus appears to lie along the base of the Sigsbee Escarpment, suggesting that erosion and deposition is occur- ring along this front. Three other discontinuous channel systems can be identified on the mosaic and appear to have contributed sediments to the deep Gulf.

Jan 1, 1986