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By M. Geoghegan

Under the provisions of the U.N. Law of the Sea Convention Ireland is likely to have mineral rights to an area of continental shelf some six times its present land area. Apart from the major potential hydrocarbon basins which are currently the focus of active commercial exploration, little is known about the mineral resources of this vast area. In recent years a variety of mineral resources however have been identified from the coastal region. These include Sand and Gravel aggregates, Calcaraeous Algae (Lithothamnion), Heavy Mineral Sands and Coal deposits. The potential also exists in the coastal zone for buried placer deposits and base metal deposits. Several million cubic metres of gravel and hundreds of millions of cubic metres of sand have been identified by the Geological Survey of Irelands (G.S.I) Marine Unit off the east coast. The greater part of these deposits lies within the 10 metre depth contour and are easily recoverable. Irish aggregate needs at present are well supplied by onshore Pleistocene glacial deposits. Commercial interest in offshore deposits is in supplying coastal areas which are locally poor in aggregate and major coastal construction works. The possibility of supplying the large British and Continental European Market nearby also exists.

Jan 1, 1988

By B. Prause

Ferromanganese crust samples collected from Central Pacific sea-mount areas became of special interest after surprisingly high nobel metal contents have been analyzed. Hydrogenetic crust growth is controlled by the conditions of the oceanic water column. Thicker encrustations show two crust generations of different age ranges. The mean values of the chemical composition state that the older generation is richer in P, Ca, Ni, Cu, Zn, and Pt and depleted in Fe, Ti, Co, Al, and Si. The differences apparently indicate a distinct change of the geochemical environment. The Pt concentrations vary up to 1800 ppb and do not clearly correlate to one of the other metals. This might indicate a bond of multiple nature. Several mechanisms have been proposed to explain the Pt concentrations in ferromanganese samples. Our models consider seawater and cosmic spherules as responsible Pt sources. In seawater the main species of dissolved Pt probably exist as the doubly negatively charged tetrachloro-complex. A precipitation of Pt in seawater may take place if the chloro-complex is decomposed by reduction of pt2+ to pt0. On the other hand, the Mn02 precipitation is caused by an oxidation of Mn2+ which is supplied from the oxygen-minimum zone. The large activation energy needed for the oxidation of divalent ~n" in solution has been recognised, and the resulting slowness in the formation of Mn(V1)-oxihydrate sug

Jan 1, 1989

By Mark D. Hannington

Results of the R/V Sonne Cruise (Edison) to the Tabar-Feni Arc from March 11 to April 5, 1994, a joint German-Canadian research cruise aboard the vessel R/V Sonne, undertook detailed mapping of the Tabar-Feni island chain, Papua New Guinea. The Tabar-Feni chain is host to several large porphyry stocks and epithermal gold deposits, including the giant Ladolam gold deposit on the island of Lihir (minimum 19 million oz. Au). The principal objective of the cruise was to map the seafloor in the vicinity of recently active alkaline volcanic islands in the Tabar-Feni chain and to characterize the tectonic setting of large high-level porphyry and epithermal gold deposits in the region. Additional work was carried out on shallow-water hot springs associated with mineralized geothermal systems on the volcanic islands. Complete sets of 1:50,000 scale (20-m contour) maps of the seafloor were produced for each of the four island groups (Feni, Tanga, Lihir, Tabar). The Lihir group was the most active and the most interesting. At least 4 (and probably 6 or 7), previously unknown volcanic cones were discovered within about 10 miles south of Lihir. The volcanoes are clearly very young and appear to have erupted along extensional faults produced by regional plate rotation. This recent volcanic activity appears to reflect recent forearc extension and represents the southward propagation of volcanic activity towards New Ireland. One volcanic cone at 1,490 m water depth is hydrothermally active, with very large areas of diffuse venting (100-200 m across), densely populated by beds of giant clams (probably calyptogena). Other vent-specific fauna are also present, including crabs, snails, sulfide worms, scale worms, limpettes, etc. The clam beds sit on a crust of hydrothermally baked and indurated, sulfidic, hyaloclastite-rich muds. The mineralization consists mainly of fine-grained disseminated pyrite and amorphous Fe-sulfides. A second, much larger cone at a depth of 1,070 m is capped by massive vesicular lavas which are intensely fractured and mineralized. Abundant sulfides and amorphous silica occur in stockwork-like veins which

Jan 1, 1994

By G. B. Carpenter

The United Nations Law of the Sea (LOS) Convention includes provisions (Article 76) for establishing the outer limits of a coastal State's continental shelf and for denoting the seaward extent of sovereign rights over natural resources. Determination of a coastal State's continental margin, according to Article 76, must consider eight factors: 1. The territorial sea baseline 2. The 2,500-meter isobath 3. The foot of the continental slope 4. A line 200 nautical miles seaward of the territorial sea baseline 5. A line seaward of the foot of the continental slope connecting the points where sediment thickness divided by distance to the foot of the slope equals .01 6. A line 60 nautical miles seaward of the foot of the continental slope 7. A line 100 nautical miles seaward of the 2,500-meter isobath 8. A line 350 nautical miles seaward of the territorial sea baseline Figure 1 shows the preliminary limits for each of the Article 76-based definitions for a portion of the U.S. Atlantic continental shelf. The additional areas gained beyond the 200- nautical mile Exclusive Economic Zone (EEZ) are highlighted. The first three factors are baselines from which the distance provisions of Article 76 are measured. Factors 4-8 are distance- from-baseline provisions for establishing the continental shelf limits. Factor 5, also known as the Depth of Sediment Limit or "Irish Formula", was calculated using sediment thickness data from seismic linesand isopach maps. All other factors were determined from digital hydrographic data. The Depth of Sediment Limit is the most advantageous method for the area shown in Figure 1. It is especially useful for introverted coastlines such as the Georgia Embayment and New York Bight areas. The 200-mile line is advantageous for protruding coasts such as those off major capes, e.g., Cape Hatteras. The 2,500-meter isobath plus 100-mile line gains

Jan 1, 1995

By Valery M. Yubko

During the last ten years seven applications for nodule-bearing areas of the World Ocean Floor International Region (IR) have been made by national companies of Russia (Yuzhmorgeologiya), France (IFREMER/AFERNOD), Japan (DORD), India (The State Department of Sea Resources Development), China (COMRA), Korea (KORDI) and the Interokeanmetal Joint Organization (IOM) of some East European countries and have been registered by the Preparatory Commission of the United Nations International Seabed Authority (ISA). Besides these groups registered within Resolution 11 of the Final Act of the III United Nations Conference on the Law of the Sea there are four international consortia registered in the USA [Kennecott (KCON), Ocean Mining Associates (DMA), Ocean Management Incorporated (OMI), and Ocean Minerals Company (OMCO)], which have interest in areas in the IR and can be considered as potential applicants. All registered areas (with the exception of the Indian Ocean) including the areas of potential applicants and also 6 areas, reserved for the ISA are located in the Clarion-Clipperton Zone of the Pacific Ocean. If within each area not less than one deposit of polymetallic nodule-bearing ores can be discovered, then, the total number of such deposits, for the present moment, is 20.

Jan 1, 1994

By Kaihui Yang

Volcanogenic massive sulfide deposits are generally considered to have been formed by hydrothermal fluids that leach ore metals out of footwall rocks. However, the necessity for a metal-rich magmatic component in the ore-forming fluid of "giant" ore deposits has been debated over the decades. The solution to this issue is important not only for metallogenic models but also for the mineral exploration. In the hydrothermal leaching model, massive sulfides at mid-ocean ridges are deposited from hydrothermal fluids containing 80 ppm Fe, 6 ppm Zn, 2 ppm Cu, 350oC, and 0.7 g/cm3 density (average data for 21oN East Pacific Rise). A simple calculation demonstrates that such a dilute fluid is unlikely to have been responsible for the formation of the largest ancient massive sulfide ores of greater than 100x106 tonnes, such as Kidd Creek, Brunswick No. 12, Neves Corvo, and Rio Tinto. For such a deposit consisting primarily of pyrite, sphalerite, galena and chalcopyrite (other minerals, including gangue, might account for an additional 10-20%) and even assuming 100% precipitation and retention of the sulfides, more than 790 km3 of vent fluid would be required. For typical water-rock reaction ratios of about 2, this fluid would have to have reacted with about 395 km3 of rock to acquire its metals by conventional leaching processes. This estimate, however, conflicts with the observation that even a giant massive sulfide ore body is usually underlain only by a few cube kilometers of obviously altered rocks. Moreover, this model is not consistent with the observation of hanging wall alteration in many large massive sulfide deposits. The close spatial association between massive sulfides and volcanic rocks, in both ancient and modern sea floors, suggests that direct magmatic contribution should be taken into account in the genetic model. Magmatic fluids, capable of carrying abundant ore metals and volatiles and escaping from magma by depressurization, are well known from modern active volcanoes on land. High concentrations of metals occur in CO2-rich magmatic fluid trapped in felsic volcanic rocks nearby large presently-forming VMS deposits in the eastern Manus Basin (Pacmanus, Suzette) and also in the footwall rocks of Ordovician giant Brunswick #12 deposit in the Bathurst district, New Brunswick. Only 1% of such metal-rich magmatic fluid mixed with heated sea water, that has leached its metals from rocks, would contribute 85% of the total metals to form an orebody. Such magmatic fluids are most likely to be formed from volatile-rich felsic magmas that are prevalent in back arcs, and, if added to the normal circulation system, the fluids could be responsible for the formation of "giant" ore deposits. If this is true, then the study of magmatic fluids in the seafloor volcanic rocks may provide criteria for the exploration of large ore deposits.

Jan 1, 2011

By Guillaume Blanc

The development of marine mining in the offshore areas adjacent to most of the insular and continental European States is limited by the complex and evolving nature of its legal regime on the basis of the relevant applicable international, European and domestic rules. As the development of marine mining requires investments in capital-intensive technologies, the bankable feasibility of marine mining projects is very much dependent on the legal security of mining rights, assets and operations in offshore areas. This is quite difficult to assess due to the constant accumulation of applicable and potentially conflicting international and domestic laws in these areas, in particular the coastal zone, the territorial sea, and the Exclusive Economic Zone (EEZ). The often conflicting interaction of international treaties, laws and regulations in offshore areas raises specific and major issues in terms of permitting processes, access rights, ownership rights over the mineral resources explored and mined, flag vs. coastal State jurisdiction over mining vessels and marine mining equipment, international environmental liabilities, and unitisation and multi-forum disputes. In addition, the determination of jurisdiction and the legal regime under which marine mining could take place is becoming even more complex with the development of EU Law and the recent revision of the International Law of the Sea, particularly the new extension regime of the EEZ and jurisdiction over the continental shelf.

Jan 1, 2004

By Philomene Verlaan

Analysis of the relationship between environmental parameters and the content of Mn, Ni, Co, Cu, Fe and Zn in ferromanganese crusts permits improved identification of locations to prospect for crusts with commercially valuable concentrations of these metals. In this study we asked whether a statistically significant relationship exists between primary productivity of the overlying surface waters, the concentration of O2 in and depth of the O2 minimum layer on the metal content of non-hydrothermal ferromanganese crusts in the Pacific Ocean between 130o W and 175o E and 0o to 30o S (the study area). To further develop the interpretation of the results of the statistical analysis and to assess in detail the geographical expression of these parameters in terms of metal content in crusts, a geostatistical technique (kriging) was used to generate contoured values for metal content, primary productivity and O2 concentration in and depth of the O2 minimum layer in the study area.

Jan 1, 2001

By Ivo Dreiseitl

The interaction between nodule harvester and eupelagic sediment on the seabed is definitely one of the key aspects of mining technology for polymetallic nodules which is to be studied in details. Physical properties of sediments play major role for evaluation of protection and preservation of marine environment while strength properties of sediments will come in useful for future mining operations. Cone penetration test (CPT) used for testing in situ is one of methods for investigation strength properties of sediments. The testing apparatus for CPT consists of an instrumented cone having a tip facing down and it is mounted on special underwater equipment (rus. UGI-1). UGI-1 can determine subsurface strength down to the depth interval 0 ? 1.10 m. Special IOM geotechnical cruise was accomplished in 1989 on board R/V Academic A. Karpinski within the extra test area of about 1000 km2. Thanks to UGI-1 the IOM database recorded unique strength sediment data (cone penetration resistance) from 279 seabed points of sounding at profiles 125.6 km long. Up to 35 strength data from depth interval 0-1.1m (every 3cm) were obtained from any particular testing point. As a result 279 strength charts could be plotted (two examples in Figure 1). The cone penetration resistance values can be correlated to shear strength parameters.

Jan 1, 2011

By Yuta Yamamoto

Seafloor massive sulfides (SMS) which contain Au, Ag, Cu, Zn, and Pb have been interested in as a target of commercial mining these 15 years. Japan has large potential of SMS and a national R&D project for the mining has been active these 5 years. However, the economy of SMS mining is very bad, because the waste tailing disposal cost is very expensive in Japan. A slurry flushing method is experimentally examined in this study for the improvement of the economy. During the flushing, because of density difference between the metal-rich ore and the waste rock, a kind of gravity separation is possible. The results suggest a possibility of the actual application.

Sep 14, 2011

By Tony van der Steen

Subsea mining system are designed for the following, principally different, tasks: Dreding - The destruction and removal of seabed sediments overlaying the bedrock. Cleaning - The competence of the system to systematically remove the deposits from an undulating hard bedrock with irregular pulleys, channels and fissures. Factors that influence the choice of dredging equipment for a specific project are project requirements such as environmental conditions, location and water depth. However, the most important selection criteria are soil conditions. As a consequence, possible dredging systems, must be evaluated for the following, principally different, characteristics: Dredging proficiency - The destruction of the strata by the equipment. System stability - The capability of the soil to support the subsea equipment The above parameters are determined by the strength characteristics and the bearing capacitv_ of the soil. The author describes the processes involved in excavating the subsea deposits and (transporting the gathered soil as a water-soil mixture to the surface using different excavation and transport methods.

Jan 1, 1998

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'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

By Frank Manheim

The purpose of this presentation is to review the history of offshore non- fisheries resource development since World War II, as an introduction to a planned symposium on offshore resources scheduled for the 1996 UMI Conference. After World War II the United States became the leader in offshore oil and gas production, deep ocean drilling technologies, offshore terminals, platforms and production systems, and natural gas recovery and transport. Wartime skills in acoustic profiling and antisubmarine warfare were transferred into commercially important geophysical exploration techniques. The application of ocean drilling and geophysical techniques permitted the recognition and elucidation of plate tectonics patterns, development of seafloor spreading theory, and the transformation of our knowledge of seabed and subseabed strata. After John Mero's studies and recommendations for developing marine manganese nodules in the late 1950's interest in nonfuel minerals grew rapidly. The formation of international deep sea mining consortia in the 1960's was accompanied by a flurry of ocean engineering development, minerals prospecting and associated environmental studies The Santa Barbara Oil Spill of 1969 resulted in a moratorium on both offshore energy and minerals leasing by the Depart- ment Interior, and catalyzed the development of new Federal legislation in 1972. In 1973 the offshore energy moratorium was lifted in response to the Arab oil embargo, and offshore energy activities surged for a time. Minerals were reopened to leasing following President Reagan's 1983 executive order implementing a 200 mile EEZ. Although interest was spurred by

Jan 1, 1995

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'N lat, 127°31'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 D. S. Cronan

Based on analogy with the Clarion-Clipperton zone, three main factors appear to influence the occurrence of potentially economic nodules in the study area, (i) elevated biological productivity, mainly above 50gCm-2y-l, (ii.) sea floor depth near or below the CCD, (iii) an absence of turbidite sedimentation. These conditions are fulfilled in parts of the following basins, where available data indicate that high grade and sometimes abundant nodules occur. i) The East Central Pacific Basin west of the Line Islands extending to the East Central Pacific Basin north and east of the Phoenix Islands ii) The West Central Pacific Basin west and northwest of the Phoenix Islands iii) The North Penrhyn Basin north of Penrhyn Island Notwithstanding the similarities between the environmental conditions under which potentially economic nodules occur in the Clarion-Clipperton zone and in the areas listed above, such similarities may relate only to present day conditions. During the possibly long periods of nodule formation, environmental conditions may have varied, and the deposits formed under conditions different from those prevailing at the present day. However, the fact that both present day conditions and the deposits in the two areas do show similarities suggests that applying the same genetic model to them has some validity. Possibly, any changes in environmental conditions during the period of formation of the deposits has been similar in both areas. Such uncertainties can only be resolved by a much fuller evaluation of the evolution of nodule deposits in both areas throughout recent geological time.

Jan 1, 1986

By Michael J. Cruickshank

The State of Hawaii has expressed concern over deterioration of the tourist beaches at Waikiki, which are becoming seriously depleted of sand. In this report the options for acquisition, transportation and placement .of sand on the beach are examined with respect to feasibility and cost. Ten sources of sand were compared, including commercial, from Australia, Maui, and Barbers Point (3), deposits offshore of the Reef Runway (3), offshore of Waikiki (3), and offshore of Molokai from the Penguin Bank (1).

Jan 1, 1991

By Paul C. Rusanowski

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

Jan 1, 1991

By C. H. Hobbs

A recently completed series of projects funded by the Commonwealth of Virginia and the U.S. Minerals Management Service was designed to assess the distribution of heavy minerals on the inner continental shelf adjacent to Virginia. These projects indicate that a suite of minerals of both strategic and economic interest is present. Analysis of several hundred grab and core samples shows that zircon, monazite, and titanium minerals (ilmenite, rutile, and leucoxene) occur in quantities that probably warrant further study by the mineral industry. Furthermore, side-scan sonography and shallow seismic profiles have provided information on the thickness and areal extent of the mineral-bearing sands. Possible development of the resource is enhanced by a potential use of offshore sand for beach nourishment. The results of the preliminary studies have been presented in open-file publications and oral reports in order that the mineral industry might have an up to date basis upon which to consider more exploratory work. Much of the effort south of the mouth of Chesapeake Bay was made in cooperation with and enhanced by an independent study of sand resources for beach nourishment and other needs. Preliminary review of the quantitative analyses of the heavy-mineral content of several hundred samples demonstrates that the distribution of high concentrations is non-uniform. From core data, the greatest abundances of some economic heavy minerals (ilmenite, rutile, leucoxene, monazite, and

Jan 1, 1988

By Andrew E. Grosz

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

Jan 1, 1986

By G. McMurray

The release by the U.S. Department of the Interior (DOI) of a Draft Environmental Impact Statement (DEIS) for the leasing of polymetallic sulfide minerals on the Gorda Ridge in December 1983 resulted in strong negative public reactions. The fundamental issues affecting federal-state relations included the amount of state involvement in the planning process and the continuing question of consistency (sensu Coastal Zone Management Act). The specific issues raised included the authority of DOI to lease nonenergy minerals offshore, the economic and strategic rationale for the proposed lease, and the adequacy of the DEIS. The questions of DEIS adequacy arose in three major areas: the lack of evidence for the existence of polymetallic sulfides on the Gorda Ridge, the lack of sufficient baseline data, and the lack of a mining scenario from which to assess potential impacts. The joint Federal-State Technical Task Force was formed in February, 1984 as part of an initial agreement between the State of Oregon and the Department of the Interior to work cooperatively. Other points in the agreement were (1) a reduction of any future proposed lease area from 40 million acres to no more than 4 million acres; (2) indefinite postponement of the lease sale; (3) deletion of the nearshore portion of the possible lease area covering the physical continental shelf and slope; (4) a commitment of a "tiered" EIS process; and (5) sharing of non-proprietary data with the public.

Jan 1, 1985