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By Alexander Malahoff

A shipboard research system capable of operating in waters of up to 2,000 meters has been designed and implemented by the Hawai'i Undersea Research Laboratory (HURL) of the University of Hawai'i. It uses a remotely-operated ocean bottom survey camera system, an ROV, the Pisces V submersible, and a submersible emergency recovery system, all aboard the 222- foot R/V Ka'imikai-o-Kanaloa. All systems are operated from the stern of Ka'imikai with a mounted Caley telearm and articulated A-frame system. The system was designed for multipurpose use of the ship for launch and recovery of the Pisces V submersible on a lift recovery line (with or without diver assistance), or night-time operations with an electro-optical cable using either the HURL ocean floor sidescan or photo and video system operated at 10 meters above the ocean floor. The 1.14-inch diameter cable is also used to operate an ROV system. The garage/ROV system can also act as a submersible rescue system with a submersible lift capability. The ship is equipped with a SeaBeam and shallow penetration sediment profiling systems. This integrated system approach to deep ocean floor research will make it possible for HURL to carry out research pro- grams on seamount ocean resources and ocean chemistry and climate in Hawai'i and the equatorial Pacific.

Jan 1, 1995

By Walter L. O?Niell

The Continental Shelf Division of the Marine Minerals Technology Center has recently completed field tests of the percussion- waterlift drill and the vibracore/vibralift convertible drill. The two systems have been modified from existing drills to increase their effectiveness and flexibility for nearshore minerals exploration. Originally the percussion-waterlift drill was designed for iand based operations, but it has been modified for use in protected shallow water areas. This drill is easily maintained, inexpensive to construct and operate, and is able to accurately recover representative samples from a variety of sedimentary deposits. Sampling is accomplished using either a reverse circulation method for the recovery of a slurry of sediment cuttings and water or employing a thin walled "Shelby tube" to core zones of interest. The vibracore/vibralift convertible drill is a modification of the remote placer drill (RPD). By combining these drills into one convertible system, it is possible to recover continuous cores of unconsolidated fine-grained sediments (vibracore), a slurry of clay to gravel size sediments over 1.0 meter intervals (vibralift), and to sample sedimentary material in environments where indurated

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 Jonguk Kim

The North Fiji Basin (NFB) is a mature intraoceanic back arc basin with an age of ~12 Ma. Recent volcanism and spreading activity are focused along the Central Spreading Ridge (CSR), A ridge segment more than 800 km long, composed of four main segments, the N160°, N15°, north-south (N-S), and southernmost segments from north to south. The dominant volcanic rock in the entire central spreading ridge is normal mid-ocean ridge basalt (N-MORB), very similar to those emplaced along mid-oceanic ridges. Conversely, influence of an oceanic island basalt (OIB) source increases northward from 18°20'S. Several basalts which show a significant subduction-related component are also observed in the southern part of the NFB. Hydrothermal activity along the spreading centers of the North Fiji Basin was investigated by several previous works, especially by the STARMER project in 1989 and 1991. Both extinct and active hydrothermal vents are found on the N15° and N-S segments. In contrast, only traces of hydrothermal activity have been found on the N160° segment. Although high temperature activity and related massive sulfide deposit on the N15° segment was further investigated by several follow-up studies, no systematic survey for other hydrothermal sites was conducted after their discovery. In 2012 and 2013, KIOST performed two hydrothermal expeditions aboard the R/V Onnuri in the three targeted areas of hydrothermal activity along the CSR of North Fiji Basin. All targeted areas include sites for hydrothermal activity reported in previous works. Occurrence and distribution of hydrothermal plume were investigated by combined

Sep 14, 2011

By Pia-Maria Haselberger, Marc Schiemann, Christian Frühling, Nicolas Richter, Hendrik Wehner, Andreas Kaschube

"The paper provides the principle considerations for a novel vehicle class within the scope of the project Large Modifiable Underwater Mothership (MUM). The main idea for these ships is to create a highly modular building block system for the global layout. This building block system allows for a mission-dependent module assembly. For the purpose of deep sea mining for example, the range of tasks reaches from multipurpose transportation and exploration missions to supporting tasks in up to 5000 m depth, e.g. energy supply. Topics covered in this paper are related to potential missions for these vehicles, the modular layout and the structural layout of a separate block module. The paper closes with a conceptual design example for this class.Index Terms—MUM, UUV, underwater mother ship, autonomous underwater vehicle, modular, deep sea, conceptual designI. INTRODUCTIONAs one of the leading economic nations, Germany is in need of energy and raw materials. In the 21st century, marine resources are a prominent and promising alternative to land based resources. However, there are challenges that need to be considered. Rough and often poorly plannable weather conditions prevail distant to the marginal seas. Ice coverage makes offshore services inefficient and costly in Polar Regions. The average ocean depth of 3500m and the associated environment conditions cause difficulties in fulfilling tasks in the deep sea. The project Large Modifiable Underwater Mothership (MUM) [1] will enable more efficient solutions in order to accomplish undersea duties and services in harsh conditions.This joint project comprises workshares from Atlas Elektronik, EvoLogics, thyssenkrupp Marine Systems, the University of Rostock and the Technische Universität Berlin. The principle idea of the project is the conception of a novel vehicle class. With highly modular autonomous underwater vehicles, this class will be capable of undertaking a variety of different tasks. Classically engineered vehicle structures will be split into single basis modules which can be flexibly assembled with specialized mission modules to form potent systems for individual assignments. The group of basis modules consists of units for navigation, vehicle control, propulsion and energy generation via fuel cell technology. The potential reusability of system relevant modules leads to a significant cost reduction and to shortened development periods compared with conventional vehicle concepts. The integration of newly designed additional mission modules is possible with little effort and a separate commercialization of single modules is feasible."

Jan 1, 2017

By Youngtak Ko

The northeastern Pacific shows the highest nodule abundance among the oceans in the world, and thus has been drawing international attention for deep-sea manganese nodule development. The objectives of this study are to construct database using geostatistics and geographic information system (GIS), to quantify rating value using probability and statistical methods, to suggest suitable sites for manganese nodule development, and to verify results using three statistical approaches. The copper and nickel contents of the nodules were determined by chemical analysis. Factors related to slope, aspect, water depth, and topography were obtained from multi-beam echo sounding data. The transparent layer thickness was determined using a sub-bottom profiler. The probability method was used to calculate each factor's rating, and the layers for different factors were summed to produce the development potential index (DPI). Result maps were constructed for manganese nodules development. The distribution pattern of DPI showed to be controlled of nodule abundance and metal contents. Verification was performed by comparing the results with sampling data in three ways: success and prediction rate, linear regression, and test of independence.

Sep 14, 2011

By T. Yamazaki, R. Arai, N. Nakatani, K. Kuroda

"These 40 years, deep-sea mining for manganese nodules, cobalt-rich manganese crusts, and seafloor massive sulfides has been continuously business and R&D targets. The economy is the most important factor for realizing the venture. Some technological options to increase the economy of deep-sea mining are introduced. They are a mechanical lift, waste rejections on seafloor, a substrate recovery as byproduct, and a pulp lift. An example application of one of the options is economically examined. Not only the same type examinations but also some technological clarifications of the options in detail are necessary.BACKGROUNDManganese nodules (nodule), seafloor massive sulfides (SMS), and cobalt-rich manganese crusts (crust) have been well recognized as future metal sources these 40 years. Among them, the nodule was the first recognized ones. The mining technologies for the deep-sea mineral resources, therefore, have been mainly developed in the major R&D projects for the nodule.The mining systems considered were shuttle miner, continuous line bucket (CLB), and hydraulic dredge ones. The shuttle miner system studied by France was a kind of basic study for autonomous underwater vehicle. The CLB system was an effective approach for a small scale and less investment cost mining (Masuda and Cruickshank, 1995). However, both were considered not effective for a bulk scale production rate mining such as 1.5 million tons per year in dry weight. In the hydraulic dredge system, a steel-pipe and flexible-hose conduit for nodule transportation named “pipestring” and a hydraulic pumpup instrument for creation of upward water flow in the pipestring named “pump-lift” or “air-lift” were adapted and developed. Hence, the hydraulic dredge system became the main stream in the mining system."

Jan 1, 2017

Recent focus by terrestrial mineral explorers (and investors) on cobalt has increasingly highlighted the future critical need for this metal, with new-age batteries being the primary utilisation. We present an overview of the world’s current terrestrial cobalt resources and put this in perspective of currently known seabed resources, particularly polymetallic nodule and crust deposits. We focus on comparison of the key exploration, development and exploitation risks for such deposits, and provide a framework for financial evaluation and appraisal.

Jan 1, 2018

By Wiebe Boomsma

This is a framework study financed by the Maritime Innovation Programme of The Netherlands and several institutions actively involved in the research of the environmental impact of deep sea mining; IHC Mining, MTI Holland, Delft University of Technology, NIOZ, IMARES, Boskalis Westminster, AllSeas and TNO. For this framework study the following mining activities have been identified to be relevant to assess the ecological impact of a deep sea mining operation: a) excavation, b) tailings return, c) vertical transport, d) vessel operations, e) ore transport and f) general operations. For this paper, only one mining activity has been selected as an example for the assessment of ecological effects. This is one of the main activities introduced by the new technology envisaged for developing deep sea mining: tailings return.

Sep 14, 2011

By P. E. Mikhailk

From July 29 to September 15, 2004, the 178th cruise of the R/V Sonne took place under the KOMEX program in the Sea of Okhotsk. One of the cruise objectives was to dredge two different kinds of seamounts: 1 ? underwater volcanoes from the north slope of the Kurile Basin; 2 ? a seamount formed by tectonic (non volcanic) processes from the Kashevarov Trough. The underwater volcanoes are young edifices (0.84 ± 06 Ma, Baranov et al., 2002) with heights ranging from 150 to 300 m. Tops of the volcanoes are located at depth of 1260 to 2340 meters. The volcanic edifices are formed by olivine-clinopyroxene-plagioclase basalts. Dredge samples are covered by Fe-Mn crusts up to 40 mm thick. The seamount from the Kashevarov Trough is a tilted block. The height of the seamount is about 400 m and its top is located at a depth of 960 meters. Biotite hornfels, conglomerates, granodiorites, dropstones, and Fe-Mn crusts were recovered there. The thicknesses of crusts are up to 150 mm. Fe-Mn crusts from the underwater volcanoes differ from Fe-Mn crusts from the Kasevarov Trough seamount in morphology as well as in mineralogical and chemical compositions. The research was supported by the Program of the Presidium of the Far East Branch of the Russian Academy of Sciences (project ? 05-III-G-08-086).

Jan 1, 2005

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 Ye Jun

Until now, more than 200 sites of sea-floor hydrothermal activities are known on the midocean ridge but few of them are documented on South Mid-Atlantic Ridge (SMAR). This on some extent restricts our directly understanding of the hydrothermal mechanism on SMAR. In 2011, During the Cruise 22 of R/V Dayangyihao, a masive sulfide field was discovered in the center part of the first-order ridge segment that bounded between Cardno Fracture Zone and Saint Helena Fracture Zone, near 15.16°S/13.35°W, which give us an opportunity to recognize the mechanism of hydrothermal systems on SMAR directly. This newly discovered hydrothermal field, which informally called SMAR 15°S, is situated in a SE-NW offset depression of an axial neovolcanic ridge, with water depth of about 2793m. In the water column around this field, strong turbidity and temperature anomalies were detected. Ten meters high venting chimneys, hydrothermal mounds as well as a large amount of hydrothermal vent shrimps were also observed and recorded by ROV and Deep tow camera on the ocean floor. The samples we collected from this field include sulfide chimney fragments, massive sulfides and basaltic rocks. In this study, we are focusing on the mineralogy and sulfur isotope geochemistry of sulfide samples for preliminarily uncovering the geological characteristics and hydrothermal processes of this hydrothermal field.

Sep 14, 2011

By Mike Woodborne

The marine diamond industry off south-western Africa is maturing rapidly. Some of the larger explorers have reached an advanced stage in their resource development and new mining operations have been started in the last year. Most of the major exploration, mining and marine engineering companies have offices in Cape Town. As a result of the increased activity and experiences to date, new approaches to marine diamond exploration and mining are now evolving. Primary factors contributing the new approaches are namely 1) the concentration of expertise in a localised area 2) the significant increase in the base of available exploration and production results and 3) parallel advances in the marine engineering design and geophysical survey equipment. The sea floor geology and setting of the marine diamond exploration areas is now better understood. Consequently the strategy for exploration and the selection of appropriate survey equipment is improved. Due to new equipment developments, different exploration alternatives now exist, depending on the programme objectives. Significant advances have also been made in the data processing and modelling undertaken to assist in the identification and targeting of potentially diamondiferous prospecting features. Similarly, the design of appropriate prospecting tools and programmes has also been improved. Following exposure to the requirements of the marine diamond industry, the design engineering and operating companies have responded with innovative designs for new prospecting tools. In recent years the availability of relevant information on marine diamond prospecting and production has increased. As a result, there is now sufficient basis for the construction of meaningful financial valuation models that can be effectively used to control and guide the exploration projects, to the benefit of both the explorer and the investor.

Jan 1, 1998

By Jan M. Peter

The Early Norian Windy Craggy massive sulfide deposit is within the allochthonous Alexander terrane of the Insular tectonic belt in extreme northwestern British Columbia (Figure 1). Host rocks are the Middle Tats Volcanics, part of an informally-named volcano-sedimentary succession of mixed graphitic argillites and mafic pillowed and massive volcanic flows and sills of Upper Triassic age (Figure 2) that have suffered only lower greeschist-facies metamorphism. The volcanic rocks are light rare earth element (LREE)-enriched and display a variably developed back-arc subduction signature. Major and trace element compositions of the host argillite show that it contains an appreciable hydrothermal component, as evidenced by low high Fe and Mn contents. These sediments therefore record steady, continuous hydrothermal activity punctuated by intermittent turbidity currents sweeping into the basin. The deposit consists of at least two discrete sulfide lenses (the North and South Sulfide Bodies), as shown in Figure 3, a level plan at the elevation of the exploration workings. Published reserves at 0.5% copper cut-off are 297.4 million tonnes grading 1.38% Cu, 0.08% Co, 0.21 g/t Au and 3.9 g/t Ag (as of December 1991). However, the deposit is larger than this and further drilling is required to delineate it completely. Mineralization comprises massive sulfide, stringer/stockwork, and finely bedded to laminated sulfides and exhalites. Stockwork mineralization consists of sulfide-quartz-chlorite veins with attendant chlorite and silica alteration. Mineralization consists predominantly of massive pyrrhotite andlor pyrite with lesser chalcopyrite and magnetite. Figure 4 is an oblique section through the North Sulfide Body, the most northerly sulfide mass shown in Figure 3, which shows the distribution of the pyrite and pynhotite-rich massive mineralization and the stringer zone. The North Sulfide Body contains appreciable sphalerite, whereas the South Sulfide Body contains only trace amounts. Gangue minerals include quartz, chlorite, calcite, siderite, ankerite, stilpnomelane and magnetite. The minor hydrothermal exhalite sediments are comprised of chert, carbonate, and minor

Jan 1, 1993

By Demoor Damien

"The exploitation of marine resources has enjoyed renewed interest with a completely new sector, that of the Deep Sea Mining of mineral resources in the seabed, that is now gaining momentum. Nevertheless, the significant environmental constraints represent a challenge for initiating these new activities, whether this is in terms of the knowledge of the concerned ecosystems or in terms of monitoring and minimizing the impact of these new activities. This paper presents 2 technologies that aim to respond to the expectations of the stakeholders in this area. The first consists of the real-time monitoring of installations/operations and their impact on the environment using the most modern underwater technologies and especially long-term deployment AUV based on AUV docking station solution and autonomous long term observatories. The second consists of a membrane allowing the confinement of an area, the reduction of the emission of particles in suspension and noise reduction.IntroductionDeep ocean environments have been explored since the mid-1800s. As the land-based reserves of hydrocarbons and minerals become depleted, increasing numbers of resourcebased projects are being proposed for shallow then deepwater environments. Two distinct resource sectors have recognized the potential commercial value of working in shallow and deepwater environments – Oil and Gas and now Mining."

Jan 1, 2017

By Paulo Chaves, Márcia Gonçalves, João R. S. Carvalho, Fernando J. A. S. Barriga, Edgar Carrolo, Tiago Luna, Ricardo Rato, Anabela Bento

INTRODUCTION For the last decades, deep-sea marine resources such as seabed massive sulfides (SMS), polymetallic nodules and ferromanganese crusts (Fe-Mn crusts) have received an ever- increasing amount of attention worldwide for their abundance in critical metals and potential commercial value. This interest has mostly been driven by the growing world demand for raw materials, in particular for high- and green-technology applications (e.g., hybrid and electric cars, batteries, photovoltaic solar cells, cell phones, super magnets), as well as by industrialized countries governments other than BRICS states need to secure a more diversified supply of metals, resulting in a new deep ocean exploration boom. Since the oceans and its resources are increasingly seen as indispensable for humans needs and their challenges in the decades to come, this boom increments pressure on marine areas, either in international or within countries economic exclusive zone (EEZ). Since 2002, the International Seabed Authority (ISA) has signed up 29 contracts with several entities and national governments from multiple countries (e.g., Japan, China, Germany, France, Russia, India, Rep. of Korea, UK, Canada, Brazil) for exploration for deep-sea mineral resources in international waters, either for scientific or commercial proposes, which together cover over 1.3 million km2 [1]. In turn, over 300 exploration licenses, covering more than 650,000 km2, have been granted within the EEZ of Pacific countries such as Papua New Guinea, Tonga, Fiji, Solomon Islands and Vanuatu [2, 3]. This number is expected to increase very rapidly, as 77 countries have proposed to the United Nations the extension of their continental shelf in order to extend their EEZ and jurisdiction over potential deep-sea mineral resources [4]. Its estimated that 42% of the potential areas for SMS occurrences, 54% for cobalt-rich Fe-Mn crusts, and 19% for polymetallic nodules lie within the EEZ of coastal countries [5]. In addition, a huge amount of seafloor is yet to be explored and evaluated. Combined, the size of the granted exploration areas represents less than 10% of the overall area thought as most favorable for the occurrence of the 3 types of deep-sea mineral resources above mentioned. This means that today’s assessments on deep-sea mineral resources are only a rough approximation.

Jan 1, 2018

By John Parianos, Simon Richards

SUMMARY The Clarion Clipperton Zone (CCZ) hosts the most valuable deposit of polymetallic nodules yet discovered. Understanding the geology of this deposit is key to its effective exploration and mining. Nautilus Minerals (via its subsidiary Tonga Offshore Mining Limited; TOML) has been progressing its understanding of the relationship between seafloor morphology/structure and nodule abundance/morphology, both locally (within its contract areas), and globally (across the CCZ and the span of its contract areas of almost 70% of the CCZ). We present the first results of a project with the aim of developing a method to quickly and accurately map seafloor morphology/structure (Tectonic Subcomponent scale) without the necessity for high resolution seafloor multibeam data. Furthermore, the results presented here will allow a first attempt in understanding the relationship between seafloor geomorphologically-defined zones and plate-scale tectonics of the CCZ and adjacent plate segments. INTRODUCTION A relationship between the type of geochemical active layer and nodule abundance/morphology has long been understood (ISA, 2010). Consideration of the range of differing nodule types found within, but especially between, the TOML contract areas allowed Parianos and Pomee (2017) to refine this relationship further via interpreted thickness and dynamism of the geochemically active layer. The scale of the deposit, both in terms of space and time is staggering (a 10-20 cm thick deposit, spanning almost 4500 km, varying within a circa 10 Ma period), but a segment wide geological map may one day prove to reflect controls on nodule formation and distribution.

Jan 1, 2018

In early 1990s, the Korean government has launched a deep-sea research program to secure the stable long-term supply of strategic metallic minerals including Cr, Cu and Ni. Through the pioneering surveys, Korea registered 150,000 km2 of Mn-nodule field in the Clarion-Clipperton area, the NE equatorial Pacific to the international sea-bed authority (ISA) in 1994. Following the ISA exploration code, the final exclusive exploration area of 75,000 Km2 was assigned in 2002, based on results of eight-year researches of chemicophysical properties of nodules, bottom profiles and sediment properties. Since that time, environmental studies, mining technical developments including robot miner and lifting system and establishment of smelting systems were accompanied with the detailed geophysical studies to decipher the priori mining area until 2009. Major points of the recent Korea Mn-nodule program are deployed on a commercial scale until 2015. In order to meet the goals, detailed 25,000 scaled mining maps in the priori area will be prepared, which can provide operation roots of the miner. In addition, an environmental-friendly mining strategy will be pursued based on the environmental impact test and environmental monitoring.

Sep 14, 2011

By Freddy Pøhner

The paper describes recent advances in the technology for mapping of the seabed with acoustic instrumentation. These instruments are typically single beam echo sounders, multibeam echo sounders and high resolution sub bottom profiler. For the single beam echo sounders, new features for deep water mapping are described, as well as the possibility for combining investigation of shallow areas with side scan sonar and vertical echo sounding in the same instrument. Multibeam echo sounding technology for deep and shallow water is reviewed, and some new high resolution instruments using dynamic beam focusing is presented. The sediment profiling technology deals with a novel design for high resolution sub bottom profiling, based upon a Mills Cross transducer with resolution as good as 3 degree in its largest configuration and a frequency range of 2,5 ? 7 kHz. Remarkable features of the system are a very high ping rate even for deep water, and the capability to map buried objects or structures by several simultaneous beams. Some results obtained with the first installation on the French research vessel ?Beatemps Beaupré? are presented.

Jan 1, 2003

By C. Wildman

Prospectivity modeling of seafloor massive sulphide (SMS) deposits has been completed over the Kermadec Arc-Colville Ridge area using the GIS based weights of evidence and fuzzy logic modeling techniques. SMS deposits are the current equivalent of ancient onshore volcanogenic massive sulphide (VMS) ore deposits. These high-grade deposits are formed on the seafloor and commonly consist of a black smoker and metal rich sediment mound complex resulting from the discharge of hydrothermal fluids (up to 400°C) from fractures on the seafloor. Metal sulphides are continuously precipitated in response to mixing of high-temperature hydrothermal fluids with ambient seawater. Accumulation of metal sulphides has led to SMS deposits being potentially major sources of copper, zinc, lead and other metals such as gold, silver, which to date remain untapped. Modeling of SMS deposits was undertaken to illustrate the power of GIS modeling for seafloor resource evaluation and how it can be used to quickly identify and rank in terms of the most likely prospective areas of the seafloor where new SMS deposits might exist. The mineral deposit modeling was constrained by the mineral systems concept which defines those parts of a mineralisation system that are critical to the ore-forming process. The deposits are typically formed in extensional tectonic settings, including both submerged tectonic margins and sea-floor spreading. Volcanic vent systems and underlying dykes, stocks and sills are the sources of heat that are responsible for converting sea water drawn down through fractures in the oceanic crust into an ore-forming hydrothermal fluid. This fluid is then capable of leaching metals and elements from surrounding footwall rocks, which are then transported upwards via the convection of hydrothermal fluids. The ore materials are then precipitated within the black smoker field as massive sulphides due to the mixing of high-temperature (250-400°C), metal-rich hydrothermal fluids with cold (about 2°C) oxygen bearing seawater.

Jan 1, 2011