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Les ressources minérales profondes en Polynésie française / Deep-sea mineral resources in French Polynesia

 | 
Pierre-Yves Le Meur
, 
Pierre Cochonat
, 
Carine David
, 
et al.

III. Summary report

2. Understanding the resource and the environment: a multifaced approach

Texte intégral

1Understanding French Polynesia’s deep-sea mineral assets is naturally a prerequisite to any decision about exploitation. This understanding constitutes part of the first phase of the mining project, involving regional exploration campaigns that often form part of scientific studies with no direct link to mineral resources. In all, five more phases must be completed before the operating phase can begin, bearing in mind that the project may be abandoned at the end of any of these if future profitability indicators fail to satisfy the investor developing the project.

2In this section we will present the state of knowledge on the topic, with the aim of informing decisions on knowledge creation and exploration efforts, the challenges of which are laid out in the fourth section of this report. The information about the state of the resource and existing knowledge will not be limited to geological and economic aspects. It will also cover the Polynesian cultural representations of the resource and the environment in which it is found, as well as information about the habitats and ecosystems associated with it.

3The recognition of deep-sea mining in all its dimensions, including cultural aspects, makes it possible to design a relevant, well-dimensioned policy tailored to the country’s needs. The choices of administrative set-ups (for example, creation of a dedicated mining authority) and institutional arrangements (e.g. creation of a marine agency that includes mining, as opposed to keeping separate sectoral policies such as mining, fisheries, and the environment) would benefit from the recognition of the interrelated nature of these dimensions. Therefore, an assessment of all existing knowledge is needed, knowledge that is very diversified both from a disciplinary perspective and in terms of knowledgeable stakeholders.

Comparing different knowledge and representations of the resource and habitats

  • 13 A mineral resource is the concentration or occurrence of a solid substance with economic value on/ (...)
  • 14 Mineral reserves refer to the part of the measured or indicated mineral resources that can be prof (...)

4The different actors’ representations (norms, expertise, values, etc.) play a vital role in formulating a public policy for deep-sea mineral resources. Indeed, the value of the resource is subject to multiple, sometimes contradictory, readings: minerals form the basis for the Polynesian view of the world and also hold potential value in terms of the economy and the environment. Exploration makes it possible to describe the type of mineral formation and acquire the precise information needed to accurately estimate the content, composition and geometry (thickness, distribution of content, etc.) of the mineralisations, in order to calculate the resources in accordance with standard NI 43-10113. The economic aspect is already at play when describing the resources and plays an essential role in defining what are known as “reserves”14 within these resources.

5The differences between the priorities perceived by the different stakeholders are especially important, given that information on the resources remains incomplete, that economic and environmental factors are uncertain, and that the rules governing the allocation of mining revenues among the various stakeholders have not been defined. The value attributed to a mineral resource by the various stakeholders involved in a mining project is the outcome of different levels of analysis.

6The conditions for a successful mining project thus go beyond the criterion of profit, involving not only the existence of a deposit, the availability of expertise and technology, and access to funding, but also acceptance by all relevant stakeholders and thus the recognition of their knowledge, values, interests and representations.

State of geological knowledge on the deep-sea mineral asset

7Our knowledge about French Polynesia’s deep-sea mineral resource is very limited, both in terms of the overall coverage of the EEZ and of the quality of available information. The EEZ was explored to a very limited extent during the Zepolyf programme in the 1990s, using the means available at the time (Bonneville and Sichoix, 1998). Information collected during the Nodules and Nodco campaigns in the 1970s and 1980s yielded encouraging signs pointing to the existence of a valuable mineral potential in French Polynesia. Of these discoveries, the most notable is that of the polymetallic crusts which are exceptionally rich in cobalt and observed on seamounts on the Tuamotu Plateau, mainly at depths of 800 to 2,500 m (Bonneville, 2002; Bougault and Saget, 2011; Fouquet and Lacroix, 2012). These crusts have some of the highest concentrations of cobalt ever found on the ocean floor. Other observations suggest the presence of polymetallic nodules on the abyssal plains north-west of the EEZ (Hein et al., 2015). However, at present, it is impossible to say with certainty whether valuable metals can be extracted in an economically and environmentally acceptable manner, and therefore whether these deposits constitute a potential resource. A great deal of marine research and exploration must take place before their status as resources can be established.

8Four main types of resources are found on the ocean floor. These include:

  • muds rich in rare earths or other metals;
  • seafloor massive sulphides;
  • polymetallic nodules;
  • polymetallic crusts.

9In the French Polynesian EEZ, polymetallic crusts and, to a lesser extent, polymetallic nodules are currently considered the most promising.

10Other types of deposit – phosphates, diamonds and accumulations of heavy metals – are currently being mined in shallow coastal waters. These fall outside the scope of this expert review, except for the phosphates, which have been found in the form of phosphorite in the substratum of polymetallic crusts (Pichocki and Hoffert, 1987).

Rare earth elements

  • 15 Drill hole 597 A, located east of the Gambier Islands, outside the boundaries of the French Polyne (...)

11The buzz generated by the article from Kato et al. (2011) is, in all likelihood, largely unfounded. The authors found concentrations of rare earth elements in mud samples from many regions of the Pacific Ocean and concluded that this material potentially represents a major source of these metals. However, a review of the data published by Kato et al. reveals wide variations in the content of rare earth elements in 78 cores recovered in the drilling operations. In fact, the average amount of rare earth elements varies between less than 250 g/t and 2,228 g/t15 . These contents are low compared to those found in many deposits on land.

12Under these conditions and given the current state of knowledge, it is unlikely that an investor would develop a project for exploiting the rare earth elements in deep-sea muds.

13However, the governments of China, Japan or Korea might be willing to mine the rare earth elements at a loss; for China, the goal would be to protect its monopoly, while for the other two the aim would be to circumvent that monopoly.

Seafloor massive sulphide deposits

  • 16 A hydrothermal system forms when hot water circulates through rocks in the crust. In ocean basins, (...)

14Seafloor massive sulphide deposits are located in back-arc basins or oceanic crust, and are associated with mid-ocean ridges or subduction zones in island arcs (Dyment et al., 2014). The main metals in seafloor massive sulphide deposits are copper (Cu) and gold (Au), along with smaller quantities of zinc (Zn) and silver (Ag). Projects for exploiting these minerals are much more advanced than for other deep-sea resources. The Canadian company Nautilus Minerals has explored the Bismarck Sea west of Papua New Guinea for more than 10 years and, despite many difficulties, is now planning to begin exploitation of the Solwara 1 deposit in 2018. To produce a large quantity of sulphides requires a long-lived hydrothermal16 system (several million to several hundred million years), as found in mid-ocean ridges or convergent margins; on volcanic islands and seamounts such systems are short-lived and only trace amounts of sulphide precipitates are found there.

15The entire French Polynesian EEZ is located in an intra-plate setting and thus lacks the conditions required for forming significant deposits of this type.

Polymetallic nodules

16Polymetallic nodules are rock concretions composed primarily of concentric layers of iron and manganese oxides/hydroxides. They are found in high concentrations on sediment-covered abyssal plains at water depths between 3,500 and 6,500 m. Polymetallic nodules are enriched with the following metals, listed here in descending order of abundance: manganese, nickel, copper, cobalt, molybdenum and rare earth elements. Manganese (Mn) adds a considerable amount to the total value of the mineralisation. To date, the most favourable region is bracketed by the Clarion and Clipperton fractures in the eastern central Pacific. The International Seabed Authority has granted 14 exploration permits in this region to 18 countries, including France. The existence of this type of resource in French Polynesia is indicated by the exploration conducted on the periphery of the EEZ (SPC-EU EDF10 Deep-Sea Minerals (DSM) Project, Brochure 6) and described by Hein et al. (2015).

17Abundant nodules have been reported in the Cook Islands EEZ, in the western part of the French Polynesian EEZ and, most commonly, outside both EEZ in international waters.

Polymetallic crusts

18Polymetallic crusts are layers of iron and manganese oxides enriched with metals like cobalt (Co), titanium (Ti), nickel (Ni), platinum (Pt) and rare earth elements that form on a volcanic or sedimentary substrate on the ocean floor. With thicknesses ranging from a few centimetres to up to 25 cm (2 to 10 cm on average), these formations are associated with intra-plate volcanoes, isolated seamounts, volcanic chains, and volcanic or carbonate platforms. They are found at water depths of 400 to 4,000 m and may cover areas of the ocean floor ranging from several square kilometres to several hundred square kilometres. Their distribution is related to how they form; they are mainly found on ancient parts of the seabed in areas where the rate of sedimentation is low or almost zero, most often on seamounts that rise at least 1,000 m above the ocean floor.

19Some parts of the French Polynesian EEZ have great potential for this type of resource, but not enough data is available to perform accurate estimates, as indicated by Dyment et al. (2014).

20Our assessment of the potential value of polymetallic crusts in French Polynesia is based on three criteria: age, depth, and slope. According to Hein et al. (2013), crusts form at rate of 1 to 6 mm every million years at depths between 400 m and 4,000 m, in areas with little sedimentation. Thus, they are potentially thicker – and therefore more valuable – on older formations. A priori, such deposits would be easier to exploit at shallow depths and on gentle slopes. Above 800 m, biological productivity increases the rate of sedimentation. Below 2,500 m, crusts are less abundant and more difficult to exploit. When identifying promising areas, we have limited our range of depths to 800 to 2,500 m. At these depths, the most promising targets are the Tuamotu Plateau, the Australs and, to a lesser extent, the Tarava seamount chain to the south-west of the Society Islands, the latter having less extensive surfaces within the appropriate depth range. If we eliminate surfaces that are too steep (and therefore difficult to exploit), the Tuamotu and Austral archipelagos appear to be the most promising. The age of the volcanic units and duration of erosion after the end of volcanic activity provide additional constraints. From our current state of knowledge, which is mainly limited to the Kaukura and Niau areas in the Tuamotu Archipelago (Martel-Jeantin et al., 2001; Bonneville, 2002; Bougault and Saget, 2011) and the Tarava Seamounts, the oldest seamounts in the French Polynesian EEZ – those most likely to be covered by large areas of thick polymetallic crusts – are located on the south-western and north-eastern parts of the Tuamotu Plateau. The Marquesas seamounts are too young to have developed thick crusts and their morphologies are too steep to allow for easy exploitation.

  • 17 See accurate position: http://expeditions.mnhn.fr/campaign/tarasoc/event/DW3352?area=1

Photo 1. Content of a dredge showing polymetallic crusts, during the oceanographic campain TARASOC, 600-850m. deep, in the south-western area of Kaukura17.
© IRD-MNHN/S. Samadi

21A combination of criteria – age, depth, slope and potentially large areas between 800 and 2,500 m – leads us to propose that polymetallic crusts have the greatest potential as deep-sea mineral resources and that the most promising sites are located in the north-eastern and south-western parts of the Tuamotu Plateau. These criteria should be supplemented with other parameters relating to ecosystems (vulnerability, resilience and scarcity) and the current and future uses of these areas (see below).

Issues relating to expanding the EEZ

22The Extraplac programme (French programme for extending the continental shelf) is legally responsible for investigating applications to extend the continental shelf; it also affords an opportunity to generate new data and thereby contribute to the formulation of a strategy for surveying the potential resources of the EEZ and its extension (see I-4). This strategy will necessarily be developed within the context of future research programmes, since the mineral resource aspect is an integral part of the scientific and multidisciplinary exploration of the deep seafloor, as has been stated on multiple occasions (Dyment et al., 2014).

23The Polynesian request is the last to be prepared. After theoretical study of French Polynesia, it was deemed necessary to acquire additional, more recent bathymetric data on key locations. An initial geophysical survey known as Polyplac was con-ducted in 2012 in an area to the south-east of the Marquesas Islands. A second survey, Polyplac 2, was conducted in April/May 2015 in the area to the east of the Tuamotus. In addition to these two areas, one located east of the Australs was added because it was also deemed relevant to an application for demarcation of the continental shelf. After the second geophysical survey and leveraging existing data, it is possible that the application for demarcation of the continental shelf for French Polynesia in the three areas considered the most relevant, all located in the eastern part of the EEZ, may be submitted by 2016. However, it is unlikely that the application will be reviewed before several years, due to the current backlog of applications received by the Commission on the Limits of the Continental Shelf (CLCS). The goal will be to provide the elements required for assessment of resources and to protect the environment.

24This project could be positioned as a post-Extraplac public service initiative.

Ecosystems and habitats surrounding the resource

25Geological knowledge on the resource has to be contextualised in two ways: firstly by putting it in the context of the marine habitats and ecosystems that have formed in its vicinity (see IV-1 and IV-2); and secondly by approaching it from the standpoint of cultural representations of the marine environment (I-1).

  • 18 See the full definition in the “Glossary” contribution.

26There is a vast maritime area that would be affected by the exploration of deep-sea mineral resources in French Polynesia. The potential resources identified are the polymetallic crusts (and polymetallic nodules to a lesser extent) that form on seamounts such as plateaus or the tops of guyots (seamounts of volcanic origin with flat tops)18. The thickness of the crusts remains unknown but exploitation may involve considerable surface areas. An important feature of marine environments is the interdependence between compartments that are far removed from one another, either vertically (along the water column) or horizontally (between distant sites). On the one hand, these links result from the life cycles of organisms, which can include phases in different compartments of the water column and, on the other hand, trophic connections between these different compartments (Shank, 2010; see IV-1).

27Almost nothing is known about the organisms and habitats that would be directly impacted by exploiting these resources in French Polynesia and little more is known at global level. The limited data available come from the French naturalist explorations that have been ongoing for the past forty years in the south-western Pacific (Bouchet et al., 2008). These data shed some light on the diversity of organisms, but provide little information about ecology and how the ecosystem functions. The limited amount of available results suggests that the deep-sea benthic fauna, like the flora and fauna of the reefs of French Polynesia, is relatively less diverse than in the golden triangle of marine diversity encompassing Indonesia and Papua New Guinea. However, the fauna of French Polynesia has a larger proportion of endemic species.

  • 19 Pelagic organisms live in the open sea in the upper part of the water column.
  • 20 Benthic invertebrates live on the bottom of the water column on the seafloor.

28The seamounts are, however, well-known to fishermen as they have higher con-centrations of pelagic organisms19 and predators. The ecology of large marine vertebrates – birds, mammals and fish – is better documented than that of benthic invertebrates20. Based on the seasons or the stages of their life cycles, many of these pelagic organisms travel across vast maritime areas that for some extend from the cold waters south of New Zealand all the way to the Marquesas archipelago.

29Though the ecological data for benthic fauna are not as extensive, the biology of these organisms usually involves a mobile pelagic phase enabling them to disperse between far-flung favourable habitats (Shank, 2010). In its adult stage, a portion of the benthic fauna associated with the seamounts on which crusts are likely to form is stationary or largely immobile (sponges, corals, sea fans, etc.). Most of these organisms have long lives and act as ecosystem architects (Samadi et al., 2007). This long lifespan is made possible by structural stability, which is also one of the factors that allows crusts to form. The little data available (Schlacher et al., 2014) do not allow us to rule out the possibility that the fauna associated with crusts are different from those associated with non-encrusted seamounts. The answer to this question is crucial when it comes to formulating a plan for managing and protecting deep-sea fauna impacted by potential exploitation.

Polynesian representations of the resource and the habitat

30The cultural approach to the resource enhances the reference base and therefore the “public policy narrative” within which a deep-sea mining project could take place (see I-1).

31The value is twofold. First, since it is conducted prior to any mining operations, it is possible to develop an original deep-sea mining strategy tailored to the realities of the country. Second, taking into account cultural practices and representations of the environment where the resource is found will forge better understanding and help anticipate the reactions of the affected populations. The aim is to ensure mineral exploitation serves territorial development.

32The nature-culture relationship in Polynesia is seen as a genealogical relationship, following a principle of continuity where the gods and humans are genealogically related to nature, which includes the mineral world (see I-1). Plants and minerals can be considered an extension of kin or as a manifestation of the divine in the visible world. In this respect, mining for mineral resources is not only an industrial process but also an act of cultural decontextualisation.

33Recognising the culturally sensitive nature of marine habitats is an essential pre-requisite to the development of any activity likely to affect that environment.

34It is also vital in this context to consider the very active policies on identity and cultural recognition in French Polynesia, in place for the last couple of decades (Saura, 2009), if we are to better understand and perhaps predict how the possible development of new activity affecting the environment may be received and possibly adopted in local political arenas. This level, i.e. the active mobilisation of identity and culture, differs from the everyday individual and collective cultural representations and practices concerning the environment and reproducing the Polynesian continuum of nature/culture.

35With regard to the deep-sea mining issue, understanding how the marine environment and its different components (human and non-human) are part of a culturally constructed continuum will help further understanding and even anticipate the reactions of stakeholders when faced with potential deep-sea mineral development. It is not solely a question of potential conflicts of use in the affected areas but also one of possible conflicts of representations. In this regard, we need to take into account the wide variety of positions held by individuals and groups: knowledge and cultural representations are not evenly distributed and they can be politically exploited.

Notes

13 A mineral resource is the concentration or occurrence of a solid substance with economic value on/in the Earth’s crust with a form, content or quality that presents reasonable prospects for profitable extraction (see glossary for further details). This simple definition, employed by the mining sector and international bodies, has been challenged and modified in the field of social sciences by economists, geographers and anthropologists, who highlight the relational and socially constructed nature of the resource, through various abstract, practical, commercial and technological approaches to the idea of the resource, as opposed to the natural “material” (for example Strang, 1997; Bridge, 2014).

14 Mineral reserves refer to the part of the measured or indicated mineral resources that can be profitably exploited (see glossary for further details).

15 Drill hole 597 A, located east of the Gambier Islands, outside the boundaries of the French Polynesian EEZ, drill hole coordinates: 18°48.43’S, 129°46.22’W.

16 A hydrothermal system forms when hot water circulates through rocks in the crust. In ocean basins, seawater penetrates the crust and then emerges through the ocean floor, forming hydrothermal vents known as black smokers. Sulphide precipitation may produce ore deposits (massive sulphide deposits).

17 See accurate position: http://expeditions.mnhn.fr/campaign/tarasoc/event/DW3352?area=1

18 See the full definition in the “Glossary” contribution.

19 Pelagic organisms live in the open sea in the upper part of the water column.

20 Benthic invertebrates live on the bottom of the water column on the seafloor.

Table des illustrations

Légende Photo 1. Content of a dredge showing polymetallic crusts, during the oceanographic campain TARASOC, 600-850m. deep, in the south-western area of Kaukura17.© IRD-MNHN/S. Samadi
URL http://books.openedition.org/irdeditions/docannexe/image/9590/img-1.jpg
Fichier image/jpeg, 254k

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