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By Richard H. T. Garnett

On the western continental shelf of southern Africa diamonds derived from onshore sources are concentrated in gravels within drowned terrestrial and marine geomorphological features. First discovered offshore in the late 1950's, they are known to exist for about 1400 km along the Namibian and South African coast in water depths of up to 200 m. Shallow water operations yielded 1.5 Mct during the decade ending 1970 when De Beers acquired a majority of the offshore leases and commenced a 15 year exploration program. Deeper water and the prevailing sea conditions required the development of new, unique, marine mining equipment. The first large scale mining production of 22 kct was achieved by De Beers in 1989 with an output of 22 kct. Annual marine output from all sources now exceeds 0.6 Mct worth some US.$ 170 M, and rising to 0.7-0.8 Mct for 1998. Exploration has also been taking place in the waters of West Africa, Australia, and Indonesia. Exploration is by means of high resolution geophysics followed by sampling using a variety of drills, airlifts and seabed-mounted machines which imitate the eventual mining process. Surveying is now probing depths of 500 m. Smaller scale mining by several junior companies has traditionally involved diving and airlift systems. Increasingly, however, they are adopting different and improved techniques which to date have been employed only by De Beers Marine as contractor to Namdeb. Marine exploration and unit mining costs are high compared to those applicable to alluvial deposits onshore. By 1996 the total development costs incurred by De Beers alone reportedly had exceeded US.$ 500 M. However, the financial rewards are commen-surate because of the higher recovered grades. The operations are not without risk for the total of nearly 10 large and medium scale production vessels deployed by various organisations. The greatest shortfalls are experienced in the estimated throughput, not the grade.

Jan 1, 1998

By Tetsuo Yamazaki

Seafloor massive sulfides (SMS) in the western Pacific have received much attention as resources for gold, silver, copper, zinc, and lead (Lenoble, 2000). Since the end of the 1980s, SMS have been found in the back-arc basin and on oceanic island-arc areas. The typical representatives found are in the Okinawa Trough and on the Izu-Ogasawara Arc near Japan (Halbach et al., 1989; Iizasa et al., 1999), in the Lau Basin and the North Fiji Basin near Fiji (Fouquet et al., 1991; Bendel et al., 1993), and in the East Manus Basin near Papua New Guinea (PNG) (Kia and Lasark, 1999). The higher gold, silver, and copper contents in one of the areas increased the chance for profitable mining operation, which was considered by a private company (Malnic, 2001). The company gathered investment money and announced to start the commercial mining from 2010 (www.nautilusminerals.com). On the basis of geological information of the Sunrise Deposit of the Myojin Knoll on the Izu-Ogasawara Arc (Iizasa et al., 1999) and geotechnical characteristics of SMS (Yamazaki and Park, 2003), some preliminary economic validation analyses of the SMS mining in small production scale were reported by one of the authors (Yamazaki et al., 2003; Yamazaki and Park, 2005; Yamazaki, 2007). The results showed high profitability of the SMS mining.

Jan 1, 2011

By Alexander Malahoff

The study of why and how life survives in the Extreme environment is a major frontier of science today. Extremophiles are organisms that require extreme environment including high temperature, pH, pressure and salt concentration, or low temperature, pH, nutrient concentration, or water availability. Their common habitats are geothermal vents, pools, lakes and craters of active volcanic regions, such as those of New Zealand, Japan, Kamchatka, Yellowstone USA or the hydrothermal vents of the ocean ridges and submarine volcanoes. These settings are accessible by foot, boat, helicopter, or submersibles. This presentation examines the geology, chemistry of geothermal sites of New Zealand, including the active volcano, White Island, Yellowstone, the submarine volcano Loihi in Hawaii, and sections of the mid-ocean ridges. Designing process and construction of Extremophilic sampling and bioreactor systems used in the study of Extremophiles will be discussed. The driving force behind the research of extremophiles is not only the fundamental science, but also biotechnological potential associated with these microorganisms and their cellular products. The University of Hawaii?s Marine Bioproducts and Engineering Center (MarBEC) is laying the foundations for such new industries.

Jan 1, 2001

By J. Robert Woolsey

This paper provides certain Southeastern coal-burning utilities with an economic strategy for complying with the sulfur dioxide emission standards set firth by the Clean Air Act Amendments of 1990. The strategy takes advantage of the occurrence of vast quantities of manganese nodules on the Blake Plateau offshore Georgia and the Carolinas, a commodity which as been proven to be a highly effective dry sorbent of sulfur dioxide. Using existing technology, manganese nodules could be mined and transported via barge directly to power plant sites, where they would be used as filter material for cleaning sulfur dioxide from the effluents of coal-fired power plants. Completely sulfated filter material could be treated for the extraction of by-product metals such as cobalt, copper, nickel, and manganese. The strategy may well be enhanced by the occurrence of ore grade phosphate rock in the same area of the Blake Plateau. This phosphate rock could be simultaneously mined to effect a reduction in production costs if it is found to be suitable for use as either a direct application fertilizer or as an acidulated superphosphate fertilizer. The manganese nodule-based strategy offers a retrofitting solution for existing power plants that would minimize the capital costs for compliance with the Clean Air Act Amendments and has the added advantage of providing a number of other metal or fertilizer by-products.

Jan 1, 1992

Massive sulfides discovered in 1991 and further explored in 1993 in the eastern Manus back-arc basin, north of Papua New Guinea, represent one of the few modem seafloor occurrences known to he associated solely with highly siliceous volcanic rocks. As such they are very close analogs of ancient volcanogenic massive sulfide (VMS) ore deposits, and hence an excellent natural laboratory for developing new approaches for land-based VMS exploration. The Manus Basin lies between the active New Britain subduction zone and volcanic arc to its south and the opposed inactive Manus subduction trench to its north. It is being extended in a complex pattern of short neovolcanic zones and oblique transform faults. In its western sector, relatively mature back-arc spreading has created predominantly basaltic segments with characteristics and mineralization generally similar to those of mid- ocean ridges. At its far east, however, the basin is distinctly immature. The East Manus Volcanic Zone lies between two members of the Manus transform set, and is an en-echelon series of neovolcanic edifices constructed on extensionally thinned island arc crust formed during the earlier manus subduction episode. Individual edifices range from predominantly basaltic to predominantly dacitic in composition. Two of the edifices are known to be hydrothermally active, and a particulate plume with unknown source occurs in the seawater column above a third.

Jan 1, 1993

By Elizabeth McIsaac, Wylie Spicer

"In July 2016 the International Seabed Authority (the “ISA”) released a first working draft of its mineral exploitation regulations as well as the standard contract terms for mineral resources in the Area, for which stakeholder input was sought in late 2016. In January of 2017 the ISA released a discussion paper on environmental matters related to these draft regulations. The ISA is now in the process of further developing its draft exploitation regulations and standard contract terms to ensure that seabed mining is carried out in an environmentally sound way for the common benefit of mankind.As the regulator of the “Area”, the ISA can draw lessons from onshore mining regulators and offshore petroleum regulators for their experiences in legislative drafting to smoothly and safely oversee project development, implementation, and closure. However, one of the unique challenges that the ISA faces in regulating private industry is its status as an international organization and not a sovereign nation, which results in a significantly different legal relationship between the regulator and the regulated. The result is that the exploitation contract is the sole legal connection between the mining proponent and the regulator for the exploitation phrase of the project.Accordingly, in the regulatory development process, the ISA must carefully consider which rights and obligations are set out in the exploitation contract versus the regulations. This decision will dictate the flexibility the ISA will have to modernize the conduct required of mining proponents in response to changing best practices in the industry, technological progress, and advances in the understanding of the marine ecosystem. As the first working draft of the exploitation regulations sets out an initial contract period of twenty years, it is crucial for the ISA to carefully consider the rights, obligations, and procedures it agrees to in the exploitation contract, as unilateral amendment will not be possible after contract execution."

Jan 1, 2017

By Anthony Wakefield

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

Jan 1, 1998

By Ian J. Graham, Cornel E. J. de Ronde

New Zealand lies astride a convergent plate boundary that extends north-eastwards from the Taupo Volcanic Zone (TVZ) to Tonga. This boundary is marked by the Kermadec arc, c. 1200 km of which falls within New Zealand’s EEZ, and which is host to numerous volcanic edifices both on the arc and in a zone immediately behind the arc to the west. In 1999, thirteen volcanic centres in the southern 260 km of the arc were surveyed for their hydrothermal plumes with seven of them discharging vent fluids into the surrounding ocean. Three of the seven volcanic centres have had mineralised rocks recovered from them during dredging and submersible operations, namely Brothers, Rumble II West and Clark. Presentday plume data combined with mineralogical evidence indicate that the vent sites at Rumble II West and Clark are waning, although the presence of Cu-rich sulphides in samples recovered from Rumble II West suggest there may be a massive sulphide (Cu-Zn-Pb-Ba ± Au) deposit located within the caldera. Brothers volcanic centre is host to the largest polymetallic mineral deposit discovered along the Kermadec arc and has numerous, up to 7 m tall chimneys within a c. 600 x 200 m area located on its NW caldera wall. Geochemical data indicate that concentrations of base metals are variable and depend critically on sample type. When combined with mineralogical and plume data, this indicates addition of a magmatic fluid component to the vent fluids.

Aug 24, 2006

By S. Hölz, M. Jegen, K. Reeck, A. Haroon

Past investigations of seafloor massive sulfides (SMS) focused on actively forming sites. New technologies are needed to explore for SMS deposits which have finished their active phase and are possibly covered by sediments or lava. For this purpose the new marine transient electromagnetic (TEM) induction system MARTEMIS was developed by GEOMAR. The system was used for investigations in the Tyrrhenian Sea (Palinuro Seamount) and at the Mid-Atlantic Ridge (TAG area) and proved to be suitable for operations at shallow (~600m) and great water depths (~3600m) in steep and difficult terrain. Calibration measurements in the water column demonstrate that it is possible to acquire high quality data, which is fit to be evaluated in terms of inversions. However, these calibration measurements also demonstrated that great care has to be taken in the design of such an inductive coil system, because relatively small metal structures attached to the system may lead to significant static distortions in the measured transients. The interpretation of TEM data acquired at the Palinuro Seamount show a conductive layer in the vicinity of a previously drilled, buried SMS occurrence and serve as proof of principle of the system. Results also indicate that the conductive SMS unit is indeed a confined layer with limited thickness between 3 – 5m, which was not known from previous drilling. In a similar manner, results also hint at an unknown mineralization at depth in a second area of the Palinuro Seamount. Investigations by TEM measurements were accompanied by measurements of the ambient electric field (→ self-potential) and seafloor temperatures with a heatflow probe as well as direct sampling with a gravity corer. The areal coverage of measurements and sampling allow for a greatly enhanced view of the structure.

Jan 1, 2018

By LeRon E. Bielak

Public Law 103-426 was signed into law in October 1994. Its provisions amended sections 8(k) and 20(a) of the Outer Continental Shelf Lands Act (OCSLA). The 8(k) amendment provides the Secretary of the U.S. Department of the Interior 001) with new discretionary authority to negotiate agreements for using Outer Continental Shelf (OCS) sand, gravel, and shell resources for certain projects of public benefit (e.g, beach, shoreline and coastal wetlands restoration that are under- taken by a Federal, State or local government agency). The new law also covers construction projects that are funded wholly or in part or authorized by the Federal Government. Under the law, the Secretary may assess a fee for use of the resource by taking into consideration the value of the resource and the public interest served. The law also requires that any Federal agency proposing to make use of OCS sand, gravel, or shell resources enter into a Memorandum of Agreement (MOA) with the DOI. An MOA would promote efficient coordination and resolution of inter- agency scheduling and issues. The law requires that Congress be notified before use is made of these OCS resources. The amendment to section 20(a) of the OCSLA clarifies that obligations concerning environmental studies extend to non- competitive lease situations and includes minerals other than oil and gas. The Minerals Management Service (MMS) is the DO1 agency responsible for interpreting and implementing the provisions of Public Law 103-426. The negotiated agreement approach is distinctly different from the competitive bidding requirements that have applied to all OCS minerals since the inception of the OCSLA. The MMS has opted to implement the new law in a nontraditional manner. Rather than issuinga body of new regulations to cover the negotiated agreement situation, or attempting to amend three sets of existing regulations, MMS is pursuing a less formal approach of providing guidelines. More weight is placed on the negotiation process itself and the legal agreement that consummates the process as the means for establishing ground rules, terms, and conditions under which qualifying projects may be conducted. This process must recognize and adhere to requirements of other laws, including the National Environmental Policy Act.

Jan 1, 1995

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'S, 70°06'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 Alexander Malahoff

With its new continental shelf beyond the exclusive economic zone, New Zealand is a country with just 4% of its territory above water. The other 96% is submerged. New Zealand's marine territory covers an area about three-quarters the size of Australia. This territory includes large portions of the Gondwana continent from which NZ separated more than 80 million years ago. This underwater land mass extends from the shores of New Zealand to a water depth of more than 5,000 m, is largely unexplored and is almost certainly the site of many large, untapped oil, gas and mineral deposits. Underwater oil and gas drilling is now a universal activity. Underwater mining is in its infancy and will become a major activity in the future, contributing greatly to the New Zealand economy. New hydrocarbon deposits will undoubtedly be discovered under the ocean floor in regions such as the Great South Basin located off Canterbury and Otago. Mineral deposits are also undoubtedly located within the oceanic crust of this underwater NZ continent. These are as yet unknown and unexplored. The oceanic crust north of the North Island is currently being extended through the subduction of the Pacific plate into the Tonga Kermadec trench and through the growth of a line of submarine volcanoes extending north to Tonga. Active submarine volcanism has led to the growth of ocean floor mineral deposits consisting of polymetallic sulphides with iron, copper, zinc and lesser gold, silver and other metals.

Jan 1, 2011

By James C. Barker

Alaska's expansive continental shelf represents future opportunities for marine mineral development. Although today's metal prices and subsidized foreign mineral production continue to discourage industry investment in marine exploration worldwide, the longer term outlook is one of increasing costs on-shore with a dwindling land-base available on which to search for and extract minerals. Likely, the generations of the 21st century will increasingly recover their minerals from the sea-floor. Though largely unexplored, Alaska potentially represents a major port ion of the U.S. marine resources. Several factors demonstrate this. First, the Alaskan OCS is huge; 74% of the entire United States' continental shelf lies off of Alaska, and 54% of the U.S. coastline is Alaskan. Combined with the jurisdiction waters of the Soviet Far East, the Bering-Chukchi shelf is one of the world's largest tracts of shallow water. Second, Alaska is situated at the northwestern terminus of the mineral-rich American cordillera. From Chile to Alaska, major on-shore deposits of precious and base metals, ferroalloys, and industrial minerals are found in the tectonically disturbed belts of the cordillera. In 1988, the western U.S. cordilleran states produced 70% of this country's mineral output (excluding construction materials). Throughout the cordillera's entire 10,000 mile length, the rock units strike largely parallel to the coastline, but in Alaska they extend directly offshore and onto the continental shelf. Consequently, the mineral-rich terranes off of Alaska have a much more complex interaction with coastal and lit-

Jan 1, 1991

By Richard Petters

Williamson and Associates, Inc of Seattle, Washington has recently built a remotely operated seafloor coring system for Nichiyu Giken Kogyo Ltd and the Metal Mining Agency of Japan (MMAJ). The system is designed to core to depths of 20 meters in 6,000 meters of water and will be operated from MMAJ's research vessel Hakurei-Maru No. 2 The corer uses rotary rod coring methods and will recover a core diameter of 44 mm. To facilitate coring through soft or unstable formations, the corer has the ability to set casing. The corer is fitted with thrusters for positioning during landing and telescoping legs for leveling. The system is operated through a 12 km electro-optical cable. Data displayed to the operator provides the operator with real-time feed back and control over the coring process. The operator has independent proportional control over bit weight, advance rate, rotary speed, and flushing water flow. The process of making up, breaking down and storing the drill string is automated and is controlled by a logic driven software routine. The system is currently undergoing trials in Japan. This presentation will discuss the drill's capabilities and should be of interest to those in need of a tool for assessing the thickness of marine mineral deposits.

Jan 1, 1996

By M. Ye. Melnikov

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

Jan 1, 2010

By M. Ye. Melnikov

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

Jan 1, 2010

By Lorena Blanco, Guillermo Gómez-Ramos, Iker Blasco, Egidio Marino, Luis Somoza, Ricardo León, Teresa Medialdea, Javier González

"This study presents the first catalogue of marine mineral deposits and energy resources along the continental margin of Spain. Aggregates, oil and gas and metalliferous mineral areas have been defined and mapped. The catalogue, implemented in a geographic information system (GIS), is conceived as a first national database within the European network, which is being built as part of the EMODnet-Geology project. It comprises 8 types of mineral and energy resources for the Spanish margins: aggregates, hydrocarbons, evaporites, placer deposits, phosphorites, polymetallic sulfides, polymetallic nodules and cobalt-rich ferromanganese crusts (Figures 1 and 2). The catalogue stores a total of 409 marine mineral deposits and compiles information such as name, deposit type, main morphology, main minerals, setting or area extent for each mineral deposit. By number of deposits compiled, the aggregates are the most abundant (286) followed by hydrocarbons (62), cobalt-rich ferromanganese crusts (32), evaporites (9), placer deposits (8), phosphorites (5), polymetallic nodules (4) and polymetallic sulphide deposits (3). Considering the total extension, hydrocarbons (32,386 km2) and cobalt-rich ferromanganese crusts (24,951 km2) represent the biggest areas.The Geological Survey of Spain (IGME) is developing a new tool in the catalogue, according the International Seabed Authority (ISA) Database parameters, for individual samples on each ferromanganese deposit. The database includes an extensive collection of records that comprise five information groups: general cruise and sample data, physical properties, mineralogy, geochemistry and acronyms used. New attributes have been incorporated, in example: geophysical, sedimentological and petrological data in the deposit area, sample weight, porosity, morphology, textural and structural features, geochemistry of major, minor and trace elements (included REEs and PGEs) and supplementary cruise and laboratory reports. This new database complements the EMODnet-Geology project minerals catalogue, offering a deeper level of information for the areas with major potential for mineral or energy resources as they are the Canary Island Seamount Province, the West Margin of Galicia and the Gulf of Cadiz."

Jan 1, 2017

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 the following composition: Mn 29%, Fe 6% Si 5%, Al 3%, Ni 1.4%, Cu 1.3%, Co 0.25%, Na 1.5%, Ca 1.5%, Mg 0.5%, K 0.5%, Ti 0.2 0.2% and Ba 0.2% (Morgan, 2000; ISA, 2002). The Pacific Rim is an area of abundant occurrence of polymetallic nodules (Glasby et al., 1980; Morgan, 2000). According to these authors, 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 6000m (Morgan et al., 1993). In studies conducted in the EEZ of the Mexican Pacific are those made within the project "Research on the origin, process and distribution of minerals in the Pacific ocean floor in the Exclusive Economic Zone of Mexico". Within this project Rosales (1989) conducted studies on the origin, process and distribution of polymetallic nodules, finding that a number of processes give origin to nodules, being diagenesis one of the main mechanisms of elements that contribute to the nodules. Besides hydrothermal processes that are carried near the East Pacific Rise at 21° N, inputs are contributing to the nodules metallic elements and sediments, especially in regions close to the dorsal, as a greater influence hydrogenetic processes occurs westward (Rosales and Carranza, 1990). In 1993, after cruise MIMAR II, Carranza and Rosales refer that metals such as Cu, Co, Ni, Sn, Fe, Mg, Pb, Zn and Ba may have 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). As result of chemical analysis of Mn, Cu, Ni and Co, polymetallic nodules observed in part of the EEZ of Mexico are possible of potential economic interest (Rosales and Carranza, 1990, 2001; Carranza and Rosales, 2003).

Sep 14, 2011

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 Peter Halbach

Within the frame of the German-Indonesian cooperative Bandamin research project two short cruises (7 station days each) were carried out which led to the Flores-Banda basin located north of the active volcanic arc. This basin is part of a large island-arc subduction-collision system resulting from a complex plate tectonic situation in which three major plates collide with each other. The eastern part of the Sunda-Banda convergent margin also includes the transition from subduction of oceanic lithosphere to collision of the Australian continental crust with the arc. This transitional part is cut and displaced by various large obliquely striking fault systems. Thus, the south eastern and eastern arc segments represent geological conditions which are suitable for the development of hydrothermal convection and potential mineral precipitation. Our study area lies north of the transitional section between Flores and Wetar. We started with a high-resolution bathymetric mapping of 240 km2 in a region some 36 km north of the island of Lomblen. A small submarine neovolcanic ridge was discovered striking approximately NW-SE and consisting of several submarine volcanic structures. In the northwest of the study area, the active subaerial Komba Volcano (Batu Tara) marks the youngest continuation of the ridge system examined. From the ridge we collected fresh and hydrothermally altered volcanics with disseminated sulfides (pyrite, pyrrhotite, markasite, and chalcopyrite), together with ferrugenous gossans.

Jan 1, 2004