Geomorphology of the Clarion Clipperton Zone, tropical North Pacific Ocean

The Clarion Clipperton Zone (CCZ) hosts a valuable deposit of polymetallic nodules. Understanding the geology of this deposit is key to its effective exploration and future mining. Interpretation of satellite derived bathymetry elucidates large scale geomorphological units and structural units that characterize the area.The Main Map is includes distinct plains, rises, and lows of abyssal hills, steps and a trough along parts of the bounding fracture zone, seamount chains, fault zones and rifts

Geology of parts of the central and eastern Clarion Clipperton Zone

The Clarion Clipperton Zone(CCZ) hosts th emost valuable deposit of polymetallic nodules yet discovered. International Seabed Authority exploration contractors, such as Tonga Offshore Mining Limited, Nauru Ocean Resources Incorporated and Marawa Research and Exploration Limited, routinely conducship-based 12kHz multibeam echosounder surveys overall or parts of their exploration contract areas. This is often supported by physical seabed samples, side-scan sonar, sub-bottom profile sonar and seabed photographs. Geological maps for seven discrete mapped areas are presented. Basaltic abyssal plains of mid-Eocene to early Miocene age are overlain by 75–100 m of mid-Eocene and younger deep-sea chalks of the Marquesas Oceanic Formation. In turn,the chalk is overlain by up to 27m of early Miocene to present, often mobile, siliceous clay-ooze sediment of the Clipperton Oceanic Formation. This stratigraphy is crosscut by a very wide variety of mostly volcanic magmatic rock units

Multi-scale variations in invertebrate and fish megafauna in the mid-eastern Clarion Clipperton Zone

The abyssal seafloor of the Clarion Clipperton Zone (CCZ) in the central Pacific has the largest known deposits of polymetallic nodules and associated benthic faunal communities with high biodiversity. The environmental factors that structure these communities, both at regional and local scales, are not well understood. In this study, seabed image surveys were used to assess distribution patterns in invertebrate and fish megafauna (>1 cm) at multiple scales in relation to key environmental factors: food supply to the seabed varying at the regional scale (hundreds of km), seabed geomorphological variations varying at the broad local scale (tens of km), and seabed nodule cover varying at the fine local scale (tens of meters). We found significant differences in megafaunal density and community composition between all study areas. Variations in faunal density did not appear to match with regional productivity gradients, although faunal density generally decreased with increasing water depth (from E to W). In contrast, geomorphology and particularly nodule cover appeared to exert strong control on local faunal abundance and community composition, but not in species richness. Local variations in faunal density and beta-diversity, particularly those driven by nodule presence (within study areas), were of comparable magnitude to those observed at a regional level (between study areas). However, regional comparisons of megabenthic assemblages showed clear shifts in dominance between taxonomic groups (perceivable even at Phylum levels) across the mid-eastern CCZ seabed, suggesting a higher regional heterogeneity than was previously thought

Preliminary observations of the Abyssal Megafauna of Kiribati

We report on preliminary observations of the abyssal megafauna communities in the exclusive economic zone of Kiribati, a huge abyssal area with few previous studies. These observations also provide useful context for marine minerals exploration within the exclusive economic zone (EEZ) and for the neighboring Clarion Clipperton Zone (CCZ), where deep-sea mining operations are planned. Seafloor images collected during seabed mining exploration were used to characterize megafaunal communities (fauna > 1 cm) in three abyssal plain areas in the eastern Kiribati EEZ (study area extending from 1 to 5°N and 173 to 156°W). Additionally, hydrographic features in each of the survey locations were inferred by reference to near-seabed current flows modeled using open-sourced oceanographic data. The images showed a dominance of foraminiferal organisms. Metazoan communities were high in morphospecies richness but had low density. These general patterns were comparable to abyssal megabenthic communities in the CCZ. There was evidence of spatial variation between the assemblages in Kiribati, but there was a relatively large pool of shared morphospecies across the entire study area. Low metazoan density limited detailed assessment of spatial variation and diversity at local scales. This finding is instructive of the levels of sampling effort required to determine spatial patterns in low density abyssal communities. The results of this study are preliminary observations that will be useful to guide future biological survey design and marine spatial planning strategies

Geology of the Clarion-Clipperton Zone: fundamental attributes in polymetallic nodule resource development

The Pacific oceanic plate segment known as the Clarion Clipperton Zone (CCZ), contains polymetallic nodules of superior consistency, tonnage and quality, to those known from other deep seabed areas. Regional scale mapping reveals structural and geomorphological features that result from variance in plate segment motion rates, and other trans-plate factors, which help to contextualise and better define the environment and exploration potential of this deposit. Exploration survey datasets from the central and eastern parts of the CCZ area allow for local geological mapping that contribute to regional models on nodule formation and distribution. Stratigraphically, basement abyssal hills include flatter areas with chain(s) of volcanic knolls. Mid Eocene and younger deep-sea chalks of the Marquesas Formation, include fault escarpment exposure, potholes and “carbonate strata breccias”. Early Miocene to present silicious clayooze of the Clipperton Formation show surficial development of ripples, slumping and sediment drifts. The clay-ooze hosts the deposit of polymetallic nodules. Unconformable volcanic rock units include single and composite knolls, seamounts, dykes and sills. Nodule forms and abundance relate to the facies scale conditions of their formation. The thickness and stability of the geochemically active layer is shown to play a crucial role on their growth. Multielement chemistry indicates differing metal contributions from silicic versus calcic primary productivity. This study confirms nodule densities, host clay-ooze bulk densities and packing densities, as well as moisture content. Moreover, it is shown that nodule handling forms attrition fines that may affect safe transport at sea. Mineral resource estimation is important to resource owner and developers. Further conversion of mineral resources to reserves requires multidisciplinary modifying factors, which include: logging of fauna; concepts behind a nodule collection system; and pyrometallurgical experiments. This study aims to improve the resource classification of the CCZ deposit in specific contract areas of the International Seabed Authority; Resumo: Geologia da Zona de Fratura de Clarion-Clipperton: Atributos Fundamentais no Desenvolvimento dos Nódulos Polimetálicos como Recurso Geológico - A área do fundo marinho conhecida por zona de fratura de Clarion-Clipperton (CCZ), no Pacífico, alberga um depósito de nódulos polimetálicos de tonelagem e qualidade superiores quando comparado com outros depósitos minerais do oceano profundo. A cartografia à escala regional permite reconhecer estruturas e características morfológicas que resultam da variação da taxa de alastramento do fundo marinho, bem como de outros fatores que afetam a evolução da CCZ e que contribuem para definir com mais detalhe o potencial envolvido na prospeção daquele depósito mineral. Os dados recolhidos no decurso de campanhas conduzidas nas zonas central e oriental da CCZ permitem realizar cartografia geológica que contribui para a formulação de modelos regionais para a formação e distribuição dos nódulos polimetálicos. Estes ocorrem associados à formação de Clipperton, com idade entre o Miocénico inferior e a atualidade. Neste trabalho é particularmente evidenciado o papel da espessura e estabilidade da camada geoquimicamente ativa no crescimento e forma dos nódulos, bem como da sua distribuição. A geoquímica multi-elementar indica diferentes contributos da produtividade primária (siliciosa versus carbonatada) para a distribuição dos diferentes metais que constituem os nódulos. Neste estudo são, igualmente, estabelecidos valores para diferentes parâmetros físicos relevantes para as atividades de prospeção, como sejam a densidade dos nódulos e dos sedimentos argilosos onde ocorrem. A classificação e estimativa de recursos minerais é relevante quer para as entidades que detêm a jurisdição sobre esses recursos quer para as entidades interessadas no seu desenvolvimento. A conversão de recursos para reservas minerais requer a aplicação dos designados por modifying factors, os quais incluem, entre outros: a descrição da fauna, o conceito associado ao desenvolvimento de colectores, testes pirometalúrgicos. Este trabalho pretende melhorar, de forma significativa, a classificação de recursos da CCZ em áreas associadas a contratos administrados pela Autoridade Internacional dos Fundos Marinhos

Empirical Application of Generalized Rayleigh Distribution for Mineral Resource Estimation of Seabed Polymetallic Nodules

An efficient empirical statistical method is developed to improve the process of mineral resource estimation of seabed polymetallic nodules and is applied to analyze the abundance of seabed polymetallic nodules in the Clarion Clipperton Zone (CCZ). The newly proposed method is based on three hypotheses as the foundation for a model of “idealized nodules”, which was validated by analyzing nodule samples collected from the seabed within the Tonga Offshore Mining Limited (TOML) exploration contract. Once validated, the “idealized nodule” model was used to deduce a set of empirical formulae for predicting the nodule resources, in terms of percentage coverage and abundance. The formulae were then applied to analyzing a total of 188 sets of nodule samples collected across the TOML areas, comprising box-core samples and towed camera images as well as other detailed box-core sample measurements from the literature. Numerical results for nodule abundance and coverage predictions were compared with field measurements, and unbiased agreement has been reached. The new method has the potential to achieve more accurate mineral resource estimation with reduced sample numbers and sizes. They may also have application in improving the efficiency of design and configuration of mining equipment

Aspects of Estimation and Reporting of Mineral Resources of Seabed Polymetallic Nodules: A Contemporaneous Case Study

Exploration of seabed polymetallic nodules identifies the Clarion Clipperton Zone and the Indian Ocean Nodule Field to be of economic interest. Mineral resource estimation is important to the owner of the resource (all of mankind; and managed by the International Seabed Authority; ISA) and to developers (commercial and government groups holding contracts with the ISA). The Committee for Mineral Reserves International Reporting Standards was developed for the land-based minerals industry and adapted in 2015 for ISA-managed nodules. Nodules can be sampled in a meaningful manner using mechanical devices, albeit with minor issues of bias. Grade and moisture content are measured using the established methodology for land-based minerals. Tonnage of resource is determined via the abundance of nodules in kilograms per square metre of seabed. This can be estimated from physical samples and, in some cases, from photographs. Contemporary resource reporting for nodules classify the level of confidence in the estimate, by considering deposit geology, sample geostatistics, etc. The reporting of estimates also addresses reasonable prospects for eventual economic extraction, including factors such as mining technology, the marine environment, metallurgical processing, and metals markets. Other requirements are qualified persons responsible for estimation and reporting, site inspection, and sample chain of custody

Thermodynamic and experimental study on efficient extraction of valuable metals from polymetallic nodules

Polymetallic nodules are promising resources for the extraction of valuable metals such as copper, nickel, and cobalt, as well as manganese alloys. To achieve efficient extraction of useful metals from the emerging resource, high-temperature carbothermic reduction of nodules was investigated by optimizing the reductant addition, slag and alloy systems. Thermochemical software FactSage was used to predict the liquidus temperature of the slag system, which is not sensitive to FeO, CaO and AlO, but decreases significantly with decreasing MnO/SiO mass ratio. The experiments were designed to reduce the oxides of Cu, Co and Ni completely, and reduce FeO partially depending on the amount of graphite addition while leaving the residual slag for further processing into ferromanganese and/or silicomanganese alloys. Co, Cu and Ni concentrations in the alloy decreased with increasing graphite addition. The optimal reduction condition was reached by adding 4 wt% graphite at the MnO/SiO mass ratio of 1.6 in slag. The most effective metal-slag separation was achieved at 1350 °C, which enables the smelting reduction to be carried out in various furnaces

Morphotectonic analysis of the East Manus Basin, Papua New Guinea

Backarc basin systems are important sites of extension leading to crustal rupture where basin development typically occurs in rifting phases (or stages) with the final successful stages identified by the formation of spreading ridges and new oceanic crust. The East Manus Basin is a young (<1 Ma), active, rapidly rifting backarc basin in a complex tectonic setting at the confluence of the oblique convergence of the Australian and Pacific plates. Here we undertake the first comprehensive spatial-temporal morphotectonic description and interpretation of the East Manus Basin including a link to the timing of, and tectonic controls on, the formation of seafloor massive sulfide mineralization. Key seafloor datasets used in the morphotectonic analysis include multi-resolution multibeam echosounder seafloor data and derivatives. Morphotectonic analysis of these data defines three evolutionary phases for the East Manus Basin. Each phase is distinguished by a variation in seafloor characteristics, volcano morphology and structural features: Phase 1 is a period of incipient extension of existing arc crust with intermediate to silicic volcanism; Phase 2 evolves to crustal rifting with effusive, flat top volcanoes with fissures; and Phase 3 is a nascent organized half-graben system with axial volcanism and seafloor spreading. The morphotectonic analysis, combined with available age constraints, shows that crustal rupture can occur rapidly (within ∼1 Myr) in backarc basins but that the different rift phases can become abandoned and preserved on the seafloor as the locus of extension and magmatism migrates to focus on the ultimate zone(s) of crustal rupture. Consequently, the spatial-temporal occurrence of significant Cu-rich seafloor massive sulfide mineralization can be constrained to the transition from Phase 1 to Phase 2 within the East Manus Basin. Mineralizing hydrothermal systems have utilized interconnected structural zones developed during these phases. This research improves our understanding of the early evolution of modern backarc systems, including the association between basin evolution and spatial-temporal formation of seafloor massive sulfide deposits, and provides key morphotectonic relationships that can be used to help interpret the evolution of paleo/fossilized backarc basins found in fold belts and accreted terrains around the world.</p

DEEPSEA MINERALS

As the need for critical minerals is now expected to be greater than the supply from the mining industry and recycling, Norway is in an excellent position to become a leader in the exploration for deep-sea minerals. The race has started, and at this conference, we will address challenges and opportunities that lie ahead