Supplementary material to “Deep-Sea Mining: Integrating Geology, Oceanography, and Engineering”
F. Michael Meyer, Department of Mineralogy and Economic Geology, Rheinisch-Westfälische Technische Hochschule Aachen, Germany; Peter E. Halbach, Institute of Geologic Sciences, Freie Universität Berlin, Germany; Peer N. Martens, Institute of Mining Engineering I, Rheinisch-Westfälische Technische Hochschule Aachen, Germany; James R. Hein, U.S. Geological Survey, Menlo Park, California; Steve Scott, Scotiabank Marine Geology Research Laboratory, Department of Geology, University of Toronto, Ontario, Canada
Citation:
Meyer, F. M., P. E. Halbach, P. N. Martens, J. R. Hein, and S. Scott (2008), Deep-Sea Mining: Integrating Geology, Oceanography, and Engineering, Eos Trans. AGU, 89(39), 365.
[Full Article (pdf)]Deep-Sea Minerals and Mining (DSMM 2008)
Aachen, Germany, 9–13 March 2008
The International Symposium and Workshop on Deep-Sea Minerals and Mining was convened at the RWTH Aachen University, Germany. More than 100 scientists from 16 countries assembled to discuss the opportunities and challenges of interdisciplinary research concerning deep-ocean mineral resources. Two days of plenary talks presented by invited experts representing a wide-range of disciplines was followed by a one day workshop to discuss the present state-of-knowledge and to develop research strategies that address newly emerging exploration and recovery techniques, as well as the economic, legal, and ecological issues inherent in deep-sea mining.
A strong increase in the global demand for metallic raw materials and the associated rising market prices has placed marine seabed mineral deposits and the feasibility of their utilization at the center of interest of many marine science and technology and raw-materials experts, as well as mining companies. This interest does not focus only on the base and precious metals but also on strategically important elements needed for high technology applications (e.g., Co, Ni, Mo, Ti, Ga, Se, Te, In, REE). Scientific sessions focused on four target areas:
1. Polymetallic Ferromanganese Nodules and Co-Rich Crusts.
These two metallic mineral deposits of the deep seabed form from soluble metal complexes derived ultimately from both continental and oceanic sources (rivers, hydrothermal input, etc.). Both deposit types consist of hydrated oxic precipitates that constitute enormous resources for metals like Mn, Cu, Ni for nodules and Mn, Co, Ni, Mo, Ti, and Ce for crusts. The papers and posters considered the geologic and oceanographic conditions at the depositional sites, variations of the chemical and mineralogical compositions of the deposits, as well as the processes of formation. The nodules generally occur as a single layer of small potato-like balls resting on unconsolidated soft sediments (often siliceous ooze) at water depths of 4000 to 5500 m. Population densities of 10 to 25 kg/ m2 are potentially economically recoverable.
The Co-rich crusts precipitate from seawater under oxidizing conditions as thin layers (up to 25 cm thick) on hard substrate rocks (e.g., hyaloclastite, fresh and altered basalt, phosphorite, limestone) on the submerged flanks and summits of seamounts, ridges, and platforms at water depths generally between 400 and 3000 m. The local geological conditions place tight constraints on the development of ore extraction tools. The nodules can be recovered rather easily from the sediment surface by available collector technologies, whereas the crusts have to be mechanically loosened before recovery can take place. Data were presented that dealt with the mechanical characteristics of this complex crust-substrate system because the physical properties of the Co-rich crusts, compared to those of the substrate rocks, have a strong influence on the methods required for separation of the crust from the substrate. New data of metallurgical tests were also presented. Extractive metallurgy of these complex oxide mineral systems presents a great challenge and is critical to the eventual economic recovery of oxide mineral deposits.
2. Seafloor Massive Sulfides.
Modern Seafloor Massive Sulfide (SMS) deposits are attractive targets for mining compared to land-based SM deposits because of the absence of significant rock overburden, order-of-magnitude higher metal grades, and the lack of a need for fixed infrastructure; therefore, the mining footprint would be significantly smaller for SMS. The main metals of interest are Cu, Zn, Ag, and Au. Several papers and posters dealt with the distribution, types, and origins of SMS deposits, and presented new results from recent exploration cruises. The discovery of seabed epithermal gold deposits was announced and the anatomy and inventory of those and SMS deposits were compared with those of land-based deposits. Questions were raised as to what lesson can be learned from land-based occurrences for the evaluation and recovery of SMS. New data presented on the concentrations of rare elements such as Mo, Se, In, and Ga in SMS indicate that these elements may occur in high enough concentrations to make their recovery as by-products economically viable. Economic concentrations of base metals (Cu, Zn) and precious metals (Au, Ag) in some arc and back-arc-basin deposits have recently attracted the interest of the international mining industry. The important link between academia and the mining industry was emphasized by presentations from representatives of various mining and mining support companies who introduced business profiles as well as reported on their economic goals for developing deep-seabed mining ventures.
3. Mineral Economics of Deep-Seabed Mining: Challenges and Opportunities.
Deep-Seabed Mining (DSM) is at the dawn of economic viability. At present, the continuously rising metal prices present a significant economic driver. In addition, considerable advances in the understanding of deposit geology and of deep-ocean recovery technologies contribute to a more reliable estimate of costs for deep-sea mining. As companies involved in DSM gather experience, system costs are bound to decrease. An added incentive is the fact that some deep-sea minerals contain strategic elements that will be essential for future high-technology applications. Environmental concerns play a central role in the development of deep-sea mining operations, consequently, these aspects were covered in several of the technical session. One paper focused on the role of the International Seabed Authority (ISA) in promoting development of the three primary seabed resources, and the set of regulations that will cover all aspects of mining activities in international waters, including environmentally sound practices. Another presentation reviewed recent research in environmental studies and concluded with recommendations for minimizing possible harmful impacts on seafloor biota.
4. Deep-Sea Mining Concepts and processing Technology.
Technological aspects of mineral recovery, transport, mineral processing, and extraction of metals from deep-sea deposits were looked at in a holistic way. This session covered single technological solutions as well as flow-oriented processing concepts, environmental challenges, and questions of sustainable development. It was made clear that possible environmental impacts may be largely determined by, and therefore mitigated by, the design and engineering of DSM tools and methods. Mining methods need to be appropriate for local site conditions so that equipment designs must have built-in flexibility. Several papers dealt with these issues related to remote crawler technologies and the principles of airlift techniques. Extractive metallurgy was also considered in this session. The main challenge is the complexity and diversity of the deposit minerals, which require a combination of various processing steps. One proposed process is based on a two-step operation involving slightly oxidising pyro-treatment in order to separate highly volatile alkalis and oxides. It was found that there is still a great amount of research needed in this field and that metallurgical processing is the most cost-intensive step in the entire mining process and could become the key step in the economic success of an operation.
The structure of the workshop followed the target areas addressed in the technical sessions. It was emphasized that for all three primary deposit types it is absolutely essential to get more and better bathymetric, geotechnical (in-situ data), and geochemical (high technology relevant trace metals) data. With these data and a better understanding of the geologic controls on deposit formation, exploration techniques can be optimized to not only discover metal accumulations but also to distinguish between economic and noneconomic occurrences. In contrast to ferromanganese nodules, the crusts are generally tightly bound to the hard substrate rocks so that the crusts have to be mechanically loosened before seafloor recovery can take place. So far, there is apparently no suitable mechanical process or technical design available that can recover a thin layer of oxide from a rough seabed without also recovering the substrate rock and thereby diluting the grade of the potential ore. To solve this difficult problem will require new and innovative engineering concepts. Crawler and lifting technologies with low environmental impact are also critical needs for technological development. Separation and extraction of the strategic minor and trace metals requires a combined multistep metallurgical process that still needs innovative advancements. The workshop participants agreed that there is substantial need for future technological developments, interdisciplinary research, and data acquisition based on close cooperation between industry and academia. At present, we are in a transition from exploration to recovery, but with the growing demand for metallic resources, the need for marine minerals will grow and presents both great challenges and great opportunities for geoscientists, engineers, and entrepreneurs.
F. Michael Meyer, Department of Mineralogy and Economic Geology, RWTH Aachen, Germany; E-mail: m.meyer@rwth-aachen.de; Peter E. Halbach, Institute of Geologic Sciences, Freie Universität Berlin, Germany; Peer N. Martens, Institute of Mining Engineering I, RWTH Aachen, Germany; James R. Hein, U.S. Geological.
