No Exploration without Hydrography

01/01/1970

Harvesting minerals in the deep sea

According to a UN group of experts in 1978, "there can be no exploitation of marine resources without exploration and there can be no exploration without hydrography". For hydrographic surveyors this is quite obvious, but exactly how important is surveying in the seabed exploration business? And does hydrographic surveying play a crucial role in the decision making of the ‘seabed explorers’? Let’s take a small tour….

Rob Berlijn, Hydro Consult bv, The Netherlands

With general mapping for safe navigation purposes, harbour construction and maintenance, offshore and support activities for coastal protection, hydrocarbon exploration in coastal zones, survey and seismic activities for the oil and gas industry, and surveys for the mining of sand and rocks, our profession is becoming more diversified and challenging every day. At present, most commercial
hydrographic surveying is for the business of exploration (for hydrocarbons: seismic surveys, site surveys, rig moves, pipeline installation and monitoring, installation of platforms, etc.).

Hydrography in Infrastructure Development
Additionally, hydrographic surveying is a core activity of infrastructure development. This is evidenced historically by the mapping and development of new lands. Of course, new lands are not only newly discovered lands but also newly created lands, such as artificial islands, port areas, offshore airports, etc. These projects require substantial amounts of sand and rock. High-quality surveys of potential borrow areas are needed, not only over larger areas but also to greater depths than before. Hydrographic aspects of geological sub-seabed research have been and will remain very important. High-accuracy positioning, sea floor imaging and sub-seabed profiling systems integrated with sophisticated correlation sampling methods are essential for up-to-date aggregate-related research. This research and studies of seabed dynamics are only possible because of the presently available high-accuracy positioning systems and (sub-)bottom classification systems.

Offshore Mining
Another exploration activity – offshore mining for coal, gold and diamonds – is already taking place in Indonesia, Canada, Namibia, Australia and South Africa. Advanced hydrographic and geophysical methodologies have been developed to assist modern gold-diggers in their quest for mineral wealth. Nowadays, AUVs and even Zeppelin-type craft are used as platforms for offshore surveys for the exploration of gold and diamonds in African waters. This is all in relatively shallow waters, where exploitation of sand, gravel, coal, precious stones and ore is technically and commercially feasible (120-metre water depth).
With the upcoming of deep-water activities for the mining of precious metals and diamonds, this exploration and associated scientific activities require more data in much shorter time spans. Extreme water depths also have an impact on the design, fabrication and use of extremely sophisticated deep-water equipment, underwater communication equipment, etc.

Mining for Minerals
Despite the rather dismal mineral market conditions, the world will become more dependent on the oceans as a mineral resource reservoir in the future.
Although offshore mining in deeper waters for mineral wealth is not required at present, it will be the only alternative in the future due to the continuously growing demand for certain metals that have limited land deposits. Mining engineers and environmental scientists are conducting studies that enable the development of innovative mining systems and subsystems for the collection, screening, lifting and transportation of deep-sea minerals. More than 20 years ago, the National Institute of Oceanography of Goa, India, started surveys and exploration for polymetallic nodules in the Indian Ocean and was the first to receive ‘Pioneer Status’ recognition from the UN.

As Questions Rise…
Experiments have been conducted to study the potential impacts of deep seabed mining on seabed environments. In addition, various methodologies have been developed for the actual retrieval of deep-water minerals, such as the well known manganese nodules. At depths between 4,000 and 6,000 metres, developing these retrieval and processing technologies to extract the desired minerals – nickel, copper, cobalt and manganese – from the nodules requires large investments. One enterprise is now at an advanced stage of preparatory work for extracting hydro-thermal metalliferrous muds from the deep trenches of the Red Sea.
Not only is the extreme water depth a limiting factor in the harvesting business of deep-water minerals in the form of nodules or crusts, but also there are some other technical and commercial questions to be ans-wered. For this, advanced hydrographic solutions will have to be developed. These questions are, for example:

where exactly are the mineral fields, at what depth, and how densely or thickly are they positioned on the ocean bottom?
are manganese nodules only on top of the seabed or does the top layer of the seabed also contain nodules?
what is the actual composition of the nodules or crust and how commercially viable is a mining operation?

Cobalt-enriched crusts on the flanks of sea mounts, volcanic islands and ridges contain as much as 2.5% cobalt and these occur at depths of 1,000 to 2,500 metres. Because the crusts are only about 2cm thick, mining technology currently presents a problem. Cobalt is the most important of the elements in nodules and crusts in terms of price and as a strategic metal. It is indispensable for ‘super alloys’ used in jet aircraft engines. Cobalt supplies are limited, and the largest producer is Congo (formerly Zaire) and, as such, the uninterrupted, continuous supply of this mineral is fragile. Ocean mining of cobalt would provide an alternative, reliable new source. The good news is that cobalt-rich manganese crusts occur on the ‘shallower’ flanks of volcanic islands and seamounts. Thus, these deposits may be easily recovered compared with the deposits found in the deeper areas.

Where to Find These Nodules?
Manganese nodules occur in all oceans. Their accretion rate is very slow, only a few millimetres in 1 million years. The average nodule has 24% manganese, compared with 35–55% manganese in land ore bodies, so they do not offer solid economics as a manganese source, but they also contain iron (14%), copper (1%), nickel (1%) and cobalt (0.25%). Nodules can be found lying on the ocean floor and probably also in the top layers of the sea bottom. The fact that the nodules are indeed found on top of the ocean floor appears to be some sort of mystery. With an average radius of some 1.5 cm and an estimated age of 4.5 million years, their accretion rate is about 3.2mm per million years. From C14 measurements of sea bottom material in nodule areas, it can be calculated that the sedimentation rate is approximately 12 metres per million years. If the nodules originated over 4 million years ago, how can they lie on top? It may be the result of organisms under the seabed (in the top layers, little worms and other creatures appear to be quite active), underwater currents or other, unknown reasons. In any case, it is quite possible that nodules not only ‘float’ on the ocean floor, but that the top layers of the sea bottom may also contain large quantities of these precious little balls.
In the last 25 years, several nodule deposits and crusts have been located, mapped and evaluated. Commercial interest has centred on the region of the eastern Pacific and detailed studies have been undertaken in the Atlantic Ocean, South of Madeira (Netherlands Institute of Applied Geoscience, NITG). Large areas still remain uncharted. Furthermore, not only do the exact location of these fields need to be surveyed, but also the quantity and quality of the crusts and nodules have to be determined. Some mysteries and other unanswered questions remain that seem to justify extensive scientific expeditions.

What Will the Future Bring?
It is certain that both manganese nodules and crusts will be exploited in the future. Potential mining sites are a 500-mile wide nodule belt running for 2,500 miles from the west of Mexico to south of Hawaii, belts of North Pacific nodules that are close to Japanese and American markets, and a large concentration in the North Atlantic that is near American and European markets.
A deep-water system is presently being developed in Germany for polymetallic nodule mining in the South Pacific Ocean. Based on 300 operating days per year and assuming the sub-sea mining vehicle moves with a velocity of 1 metre per second and has a nodule collector width of 6 metres, a mining throughput of 300,000 tons per year will be feasible. Nodules would be transferred to bulk carriers, which would shuttle between mining ships and shore processing plants. The magnitude of costs and rewards are enormous – the amount of metals produced from a single major operation could alter the world prices of the minerals. Production might equal 50% of the current consumption of manganese and 100% of the required cobalt.

No Exploration without Hydrography
The involvement of the hydrographic survey industry in this new field of offshore activities will benefit all parties involved during every phase of the project. Harvesting fields have to be located, mapped and evaluated, and the use of advanced survey tools such as AUVs, ROVs, geophysical tools, geo-technical equipment, environmental instrumentation and ancillary equipment will be indispensable, both during the exploitation and exploration phases.
In other words, as stated at the beginning of this article: "there can be no exploitation of marine resources without exploration and there can be no exploration without hydrography".

Biography of the author
Rob Berlijn began his career in 1970 as a land surveyor working for KLM Aerocarto. After this, Rob joined Decca Surveys and spent three years in Nigeria and other West African countries. In 1976 he was transferred to The Netherlands to help set up Decca Holland, later NeSA (later Thales Geosolutions). Rob joined Intersite Surveys to set up a company in Indonesia and later moved to Osiris. Since 1996, Rob has owned his own company, Hydroconsult BV, and this carries out consultative projects, surveys and also has a sales department where products from manufacturers world-wide are sold and serviced. He has been active in the Hydrographic Society and involved with Hydro international from the very beginning.

No Exploration without Hydrography

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