Hannington and two co-authors reported in mid-2023 that deep-sea mining is taking another step closer to reality. Early leases for exploration in the central Pacific manganese nodule fields and elsewhere in the oceans are coming to an end, and contractors are faced with a choice—extend the licenses to continue exploration or apply to mine the deposits they have found.
Global map of the oceans showing areas with the highest potential for manganese nodules (light blue areas),
ferromanganese crusts (orange areas), and sea-floor massive sulfide (SMS) deposits (yellow and red are
active vents; blue are inactive). Prospective areas for nodules and crust areas are based on sea-floor morphology,
age of the crust, and metal input as defined by Hein et al. (2013). Of the 433 known sites of SMS deposits, only
63 are in licensed areas. Of the remaining 370 sites, 64% are in exclusive economic zones (EEZs) and 36% are in
unlicensed areas of the high seas. Abbreviations: CCZ = Clarion-Clipperton zone, Peru B. = Peru basin, Penrhyn B.
= Penrhyn basin, PCZ = Prime Crust zone. Modified from Hein et al. (2013) and Petersen et al. (2016).
The first 15-year licenses were originally signed into effect by the International Seabed Authority (ISA) in 2001 and began to expire in 2016. With no operations in a position to commence mining and, more importantly, no regulations in place to allow it, most exploration licenses were simply renewed. Eight of the original licenses were extended for five more years, some twice, and new licenses have been granted.
Today, there are 31 contracts for exploration: 19 for manganese nodules, 7 for sea-floor massive sulfides, and 5 for Co-rich crusts. The first contract for massive sulfide exploration expires in 2026; the first for Co-rich crusts expires in 2029. Meanwhile, there is strong interest from a number of countries in the mineral resource potential of their exclusive economic zones (EEZs), particularly Japan and Norway. Against this backdrop of rapidly shifting exploration activity, it may be time to take another look at marine minerals as a resource for the future.
In a report entitled “The Future of the Ocean Economy by 2030,” the Organization for Economic Cooperation and Development (OECD) asked, “What new developments could result in a complete revision of offshore mineral potential?” For most parts of the oceans, the answer to this question is plagued by inadequate mapping and a lack of geologic knowledge as a basis for assessing the resources. However, new approaches to exploration are emerging, and recent discoveries, such as on the continental shelf and beneath the cover of sediment, are changing our view of the resource potential.
What new developments could result in a revision of offshore mineral potential?
A rigorous global assessment of marine minerals is continually frustrated by our limited knowledge of the geology of the oceans. The OECD pointed out that governments charged with management of marine mineral resources “… lack even basic tools such as a geological map of the sea floor, which is at the center of every land based minerals regulatory system.”
Unfortunately, existing geological maps of the oceans are rudimentary at best and often limited to the sedimentary cover. Most are only available at a very coarse scale (e.g., 1:25 million maps of the Commission for the Geological Map of the World, CGMW). Creating recognizable bedrock geology maps at the formation and assemblage level is only just becoming feasible through comprehensive integration of high-resolution multibeam bathymetry and multiparameter geophysics, including magnetics, gravity, and multichannel seismic surveys. An example of the workflow for bedrock mapping in the oceans has been demonstrated in a new 1:1 million geological map of the Lau basin (Fig. 3), which illustrates what can be achieved. A common refrain is: “we can’t map the entire ocean floor…it’s too big.” But initiatives are already underway to do just that, such as the Nippon Foundation-GEBCO project to create a new bathymetric map of the oceans by 2030 (see https://seabed2030.org).
The task of geologic mapping of the oceans can be parsed into achievable transects that focus on specific geodynamic settings. This transect approach is well established and highly successful in large geosurveys on land (Lithoprobe, AuScope, EarthScope, Metal Earth), but it is rarely done in the oceans. More than 50 years ago, before the discovery of black smokers at the East Pacific Rise, Peter Rona led one of the first major geoscientific transects of the global mid-ocean ridge system in the Atlantic, which resulted in the discovery of the TAG site (Rona et al., 1975, 1976; Rona, 1980).
He defied conventional wisdom about the low mineral potential of slow-spreading ridges and eventually made the first submersible observations of high-temperature hydrothermal activity in the Atlantic. That project, and Rona’s perseverance, showed the effort required to make new discoveries at a transect scale in a vast ocean. However, there is no mandate for a “Geological Survey of the Oceans” that could provide the necessary knowledge about the geology of the sea floor beyond national jurisdictions. Such an effort would require unprecedented interagency cooperation at a huge scale but could be an important complement to existing initiatives such as Seabed2030. One consideration is that there are significant benefits to this activity for coastal nations in terms of habitat characterization and monitoring environmental concerns, such as release of frozen methane. However, for resource assessments, detailed sea-floor mapping (bathymetry, side scan sonar, remote vehicle mapping, heat flow studies, and sampling, etc.) is needed.
The reviewers of this article pointed out that the bottom line for industry to be involved in the development of marine minerals has to be the economic viability and return on investment in a short time frame. On land, even the best geologic resource may not be developed for logistic or political reasons; sea-floor resources will face even more challenges outlined here. Although a number of major mining companies have engaged in offshore diamond mining and SMS exploration, none are pursuing nodules.
Are nodules too risky? What is the impact-benefit? In the case of certain commodities, like Mn, could production from vast sea-floor resources outstrip Mn mining on land, with metal production exceeding global demand? As deep-sea mining in the Area takes another step closer to reality, many of these questions are still unanswered.
Example of a new 1:1 million geologic map of the Lau basin showing
interpreted formation and assemblage level units derived from regional
magnetic, gravity, and seismic surveys together with high-resolution
multibeam bathymetry. The complete map is described in Stewart et al.
(2022) and is available for download from:
https://doi.org/10.1130/GEOS.S.16869167.
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