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Trench systems are some of the most important geodynamic settings on Earth and have a substantial influence on the global metal cycle. Trench environments are affected not only by episodic deposition of volcanic ash, but also exhibit a continuous water–rock chemical exchange. Ferromanganese nodules, which are archives for the marine Mn cycle, were first discovered in the southern Mariana Trench during China’s major 10,000-meter hadal trench scientific expedition in 2016. Nevertheless, their geochemical characteristics and formation mechanism in sedimentary environments of the trench zone remain enigmatic. In this study, these ferromanganese nodules and surrounding sediments were examined by geochemical and microbial methods. Bulk geochemistry indicated that trench nodules are characterized by high Mn/Fe ratios and nodule textures indicate a rapid growth rate, with Mn mainly from two sources: volcanic ash alteration and fluids discharge from the trench seabed. High-resolution in situ geochemical analysis categorized microlayers of an individual nodule into three types. Type I is the interior part that has a high Mn/Fe ratio (>20) and high growth rate (52.19–3571.73 mm/Myr), and formed by the influence of fluid discharge activities around this region. Type II is laminae from the exterior part that have a hydrogenetic origin with lower Mn/Fe ratio (0.01–2.50) and lower growth rate (4.54–9.86 mm/Myr). Type III is laminae from the exterior part that have a diagenetic origin with moderately high Mn/Fe ratio (2.5–15.0) and moderately high growth rate (12.40–18.93 mm/Myr). 16S rRNA gene sequence analysis revealed that the bacterial community structures in the nodule-bearing sediment samples, dominated by Shewanella and Colwellia, were substantially different from those of reference sediment samples. For the first time, we propose a conceptual model for a geochemical Mn cycle and nodule formation in trench sedimentary environments using both geochemical and microbial data.

The Ma51-4 submembers of Jingbian gas field in Ordos basin of China belongs to epeiric sea evaporative carbonate tidal flat facies. Supratidal zone of gypsum nodule dolostone and upper part of intertidal zone of gypsum crystal dolostone are most favorable reservoir. The carbonate rocks of Ma51-4 had undergone complex diagenesis. Penecontem-poraneous dolomitization and gypsification provided the material foundation of the reservoir. Epidiagenesis selective dissolution of gypseous dolostone constructs the origin shape of pore structure. The dissolution and filling of various minerals in the burial period determine whether the early dissolution pores can be preserved, and the final state of the reservoir. Burial dissolution and filling of various minerals determined the preservation of early dissolved pores and the final condition of the reservoir. The concept of “minus cement porosity” directly reflects that sedimentary facies have great influence on the growth of reservoir in Ma51-4. Combined with sedimentary microfacies and diagenetic facies, a concise numerical symbol is used to express semiquantitatively sed-imentary microfacies and diagenesis facies. This descriptive method has great benefit in reservoir evaluation and prediction.

The Permian is an important period for the deposition of siliceous rocks on a global scale, but the genesis of chert is still controversial. To better understand the mechanism of chert nodules deposition from Qixia Formation (P1q) (Lower Yangtze Plate, China), we analyzed the major, trace and rare earth elements of these chert nodule samples (CN) and surrounding rock samples (SR) using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and X-ray fluorescence (XRF) technique. The redox state, siliceous sources and depositional environment analysis show that CN have higher contents of SiO2, Fe2O3 and MnO comparing with SR, and their geochemical properties are different. Trace and rare earth elements characteristics reveal that nodules were deposited under the action of biochemistry in the basin, no terrigenous materials contamination was observed and the contribution of upwelling was emphasized. The Al/(Al+Fe+Mn), Fe/Ti and Al-Fe-Mn discrimination diagram indicated the chert nodules are influenced by hydrothermal action. Evidence from redox-sensitive elements such as Th, U, V and Sc suggests that nodules were deposited in a reducing environment. In the convective mixing of hydrothermal action and normal seawater, excessive dissolved silicon and nutrients are absorbed and precipitated by biological action, and then transported by upwelling to shallow water for deposition. All the evidence comes from the trace elements enrichment characters, Rare earth elements and Y (REY) distribution patterns and La/La*, Ce/Ce*, Eu/Eu*, LREE/HREE, Y/Ho and ΣREE characteristics.

Rare earth elements (REE) in marine minerals have been widely used as proxies for the redox status of depositional and/or diagenetic environments. Phosphate nodules, which are thought to grow within decimetres below the sediment–water interface and to be able to scavenge REE from the ambient pore water, are potential archives of subtle changes in REE compositions. Whether their REE signals represent specific redox conditions or they can be used to track the overlying water chemistry is worth exploring. Through in situ laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS), we investigate the REE compositions of a drill-core-preserved phosphate nodule from the lower Cambrian Niutitang Formation in the Daotuo area, northeastern Guizhou Province, South China. REE distributions of the nodule show concentric layers with systematic decreases in Ce anomalies (Ce/Ce*) from the core to the rim. The lowest Ce/Ce* appears in the outer rim where REE concentrations are relatively high. These results are interpreted to reflect REE exchange with pore water at a very early stage or bathymetric variation during apatite precipitation. The origin of the shale-normalized middle REE (MREE) enrichment in our sample is less constrained. Possible driving factors include preferential MREE substitution for Ca in the apatite lattice, degradation of organic matter and deposition beneath a ferruginous zone. Although speculative, the last possibility is consistent with the chemically stratified model for early Cambrian oceans, in which dynamic fluctuations of the chemocline provided an ideal depositional context for phosphogenesis.

A small sample of selachian teeth is described from a glauconitic nodule from the Ladder Chine Member, Ferruginous Sands Formation, Lower Greensand Group, late Aptian, Early Cretaceous found near Walpen Chine on the Isle of Wight, UK. The selachian fauna contains the root of an unidentified lamniform shark, and some associated teeth of a synechodontiform shark, here identified as Synechodus tenuis. The difficulties associated with the definition of the three common Cretaceous species of Synechodus - S. dubrisiensis, S. nitidus and S. tenuis - are briefly reviewed. The described material represents the first records of fossil sharks from the late Aptian of the Isle of Wight.

Polymetallic nodules found on the abyssal plains of the oceans represent one of the slowest known geological processes, and are a source of critical and rare metals for frontier technologies. A quantitative assessment of their occurrence worldwide has been hampered by a research focus on the northeastern Pacific Ocean and the lack of a global open-access data set of nodules. We have compiled a global data set of >10,000 seabed nodule and control samples, and combine it with digital grids of key environmental parameters to generate a predictive machine-learning model of nodule occurrence. In order of decreasing parameter ranking, we find that nodules are associated with very low sedimentation rates (< 0.5 cm/k.y.), moderately high oxygen values (150 and 210 mmol/m3), lithologies of clay followed by calcareous ooze, low summer surface productivity (4500 m, and low total organic carbon content (0.3–0.5 wt%). Competing hypotheses for nodule sustention and thus continued growth on the seafloor are the removal of sediment by bottom-water currents and biological activity. Using a high-resolution eddy-resolving ocean circulation model, we find that the bottom-current speeds over nodule fields are too low (

Xenophyophores, giant deep-sea agglutinated foraminifera, dominate the benthic megafauna in the eastern equatorial Pacific Clarion-Clipperton Zone. This abyssal (>4000 m depth) region hosts major deposits of polymetallic nodules targeted for future seabed mining, an activity that would destroy these highly diverse and delicate protists, particularly those living on the nodules themselves. Since the cell occupies only a small proportion of their test volume, xenophyophores may make a fairly modest contribution to benthic biomass and carbon cycling. Nevertheless, xenophyophore tests can passively enhance particle deposition, concentrate food, and provide habitat structure utilized by diverse organisms. Their destruction could therefore influence the recovery of benthic communities. Species requiring nodule substrates will likely not recover, since nodules take millions of years to form. However, xenophyophores can grow quickly and colonize extensive volcanic ash deposits within years, suggesting that sediment-dwelling species could be among the first large immobile organisms to reappear in mining-impacted areas.

The occurrence and genesis of silicified coals in Tanjung Redeb, Embalut, and Loa Kulu have been described and reconstructed by means of petrography and geochemistry. The silicified coals are black, hard, and contain dispersed fine-grained silica minerals. Silica (SiO 2 ) contents vary from 58 to 76%, and LOI (mostly represents organic matter) ranges from 23 to 40% of the bulk silicified coal samples based on the ICP-INAA analysis. Microscopic examination shows the presence of quartz, chalcedony, and amorphous opal. Silicification occurs both as layers and nodules within the coal seams. The layer type is usually thin layers (

Manganese nodules are a potential source of critical metals such as Cu, Ni, and Co and are widely distributed on the abyssal plains of the global oceans. A polymetallic nodule metallogenic belt with a heterogeneous and spatially clustered nodule distribution was recently discovered in NW Pacific inter-seamount basin (NPIB) areas. However, the geological processes that regulate the nodule occurrence in that region are unresolved. Here, we report on the characteristics of a high-density field of manganese nodules in the abyssal plain north of Suda Seamount. Ship-borne multibeam bathymetric data reveal a typical seamount sector-collapse topography characterized by radial lineaments of debris channels and ridges formed by rapid debris-avalanche flow. Backscatter data linked with underwater observation indicate that manganese nodules are more concentrated (50%–80% areal coverage) along the main body of the debris apron compared to adjacent neighboring areas (

Deep-sea polymetallic nodules are a mineral resource with potential for commercial development. Due to the unique deep-sea environment in which they are found, specialized technology and equipment are required for their extraction. In this paper, firstly, the development of deep-sea polymetallic nodule mining technology is classified into three stages, and its characteristics are summarized. Moreover, the results from research into deep-sea polymetallic nodule mining technology are analyzed, including proposals for mining systems, research into key technologies, basic scientific problems, and proof of technical feasibility from sea tests. Secondly, the testing of the collector prototype and the environmental impact assessment study of Global Sea Mineral Resources NV, as well as the progress of the deep-sea polymetallic nodule mining test project in China, are introduced. On this basis, the opportunities and challenges brought by the fast-growing demand for electric vehicles to the development of deep-sea polymetallic mining technology is analyzed, and a possible technical scheme for a mining system and the trends in its development towards high reliability and high standards of environmental protection according to the requirements of commercial exploitation are explored. This provides a reference for the research and development of high-efficiency technology and equipment for the mining of deep-sea polymetallic nodules.

Siliceous concretions (nodules), from two different geological settings—the Apulian platform margins in Kefalonia island, and the Ionian Basin in Ithaca, Atokos, and Kastos islands—have been studied both in the field and in the laboratory. Nodule cuttings are mainly characterized by the development of a core, around which a ring (rim) has been formed. Mineralogical study, using X-ray powder diffraction (XRPD) analysis, showed that the rim is usually richer in moganite than the core. Homogeneous concretions, without discernible inner core and outer ring, were observed generally in both settings. Mineralogical analysis of the selected siliceous concretions from Kefalonia island showed the presence mostly of quartz and moganite, while calcite either was absent or participated in a few samples in minor/trace abundances. Moganite was generally abundant in all the samples from Kefalonia island. Concretions from the Ionian Basin showed a variation in the quartz, moganite, and calcite contents. Mineralogical differences were recognized both between the different studied geodynamic settings and internally in the same setting, but with different stages of development. The above-mentioned differential diagenesis on nodules evolution could be related to the presence and/or abundance of stylolites, later fluid flows, restrictions from one area to another due to synchronous fault activity, and the composition of substances dissolved in fluids. Moreover, the development of concretions produced secondary fractures in the surrounding area of the nodule-bearing rocks.

The detailed mineralogical and microgeochemical characteristics of polymetallic nodules collected from the Interoceanmetal Joint Organization (IOM, Szczecin, Poland) claim area, Eastern Clarion-Clipperton Fracture Zone (CCFZ, Eastern Pacific) were described in this study. The obtained data were applied for the delimitation of nodule growth generations and estimation of the growth ratios (back-stripping using the Co-chronometer method). The applied methods included bulk X-ray powder diffraction (XRD) and electron probe microanalysis (EPMA), providing information about Mn-Fe minerals and clays composing nodules, as well as the geochemical zonation of the growth generations. The analyzed nodules were mostly diagenetic (Mn/Fe &gt, 5), with less influence on the hydrogenous processes, dominated by the presence of 10-Å phyllomanganates represented by todorokite/buserite, additionally mixed with birnessite and vernadite. The specific lithotype (intranodulith), being an integral part of polymetallic nodules, developed as a result of the secondary diagenetic processes of lithification and the cementation of Fe-rich clays (potentially nontronite and Fe-rich smectite), barite, zeolites (Na-phillipsite), bioapatite, biogenic remnants, and detrital material, occurs in holes, microcaverns, and open fractures in between ore colloforms. The contents of ∑(Ni, Cu, and Co) varied from 1.54 to 3.06 wt %. Several remnants of siliceous microorganisms (radiolarians and diatoms) were found to form pseudomorphs. The applied Co-chronometer method indicated that the nodules’ age is mainly Middle Pliocene to Middle Pleistocene, and the growth rates are typical of diagenetic and mixed hydrogenetic–diagenetic (HD) processes. Additionally, few nodules showed suboxic conditions of nucleation. Growth processes in the eastern part of the CCFZ deposit might have been induced with the Plio-Pleistocene changes in the paleooceanographic conditions related to the deglaciation of the Northern Hemisphere.

Deep-sea polymetallic nodule mining research activity has substantially increased in recent years, but the expected level of environmental impact is still being established. One environmental concern is the discharge of a sediment plume into the midwater column. We performed a dedicated field study using sediment from the Clarion Clipperton Fracture Zone. The plume was monitored and tracked using both established and novel instrumentation, including acoustic and turbulence measurements. Our field studies reveal that modeling can reliably predict the properties of a midwater plume in the vicinity of the discharge and that sediment aggregation effects are not significant. The plume model is used to drive a numerical simulation of a commercial-scale operation in the Clarion Clipperton Fracture Zone. Key takeaways are that the scale of impact of the plume is notably influenced by the values of environmentally acceptable threshold levels, the quantity of discharged sediment, and the turbulent diffusivity in the Clarion Clipperton Fracture Zone. The extent of impact by midwater discharge plumes from deep-sea nodule mining will be influenced by the quantity of plume sediment, ocean turbulence and acceptable environmental thresholds, according to numerical modelling and direct experiments

Rhodoliths are free-living and morphologically diverse marine calcareous algae commonly distributed over the continental shelf seafloor. They increase the seabed structural complexity and are of potential value as feeding and reproductive grounds for a myriad of marine fauna. The higher structural seabed complexity within rhodolith beds may also increase benthic diversity by creating microhabitats, but this relationship has been rarely explored within rhodolith beds worldwide. Here we compared benthic macrofaunal (>500 µm) structure on rhodolith beds (nodule epifauna) and within unconsolidated sediments (sediment infauna) under high and low-density beds to test whether rhodolith bed density and nodule morphology influenced macrofaunal assemblages. We observed that macrofaunal density on nodules (2538 ± 288.7 ind·m−2) was 15-fold higher when compared to sediments under those beds (166 ± 38.8 ind·m−2). Rhodolith bed density was positively related to macrofaunal density, composition, and functional diversity on the rhodoliths. Low-density beds (61 ± 27.1 nodules·m−2) with discoid-shape nodules were dominated by peracarid crustaceans whereas high-density beds (204 ± 18.7 nodules·m−2) with spheroidal nodules were dominated by Annelid polychaetes. The sediment macrofauna was also positively influenced by the density of rhodolith nodules, which increased sediment carbonate and organic quality (protein and lipids) under high-density beds. Macrofaunal functional diversity was generally higher on rhodoliths, with low similarity (low nestedness) and high taxa turnover between macrofaunal assemblages of rhodoliths and sediments. These findings indicate that rhodolith beds provide an unique habitat for benthic macrofaunal communities, with exclusive functional and taxonomic richness that are likely not typical in the unconsolidated sediment below these beds in SE Brazil. This study highlights the importance of protecting rhodolith beds from multiple sources of anthropogenic disturbance and exploration on continental shelves.

In 2006, the BGR signed a contract with the International Seabed Authority (ISA) for the exploration of polymetallic nodules in the Clarion-Clipperton Zone of the northeast Pacific. During nine expeditions, in particular, “Area E1”, the eastern part of the contract area, with a size of ~60,000 km2, was explored in detail. Here, we outline BGR’s exploration methods and provide resource estimates for Area E1 and three sub-areas. The resource assessment is predominantly based on statistical analyses of data obtained by 12-kHz multibeam bathymetry and backscatter mapping, box core sampling and geochemical analysis of nodules. The main parameter for the assessment is the nodule abundance (kg/m2), as its coefficient of variation (CoV) over the entire eastern contract area is relatively high at 36%. In contrast, the metal contents of nodules show only minor variation, with a CoV of 8% for manganese and 8% for the sum of copper, nickel and cobalt. To estimate mineral resources for the entire Area E1, we used an artificial neural network approach with a multivariate statistical correlation between nodule abundance derived from box cores and hydro-acoustic data. The total estimated resources are 540 ± 189 million tonnes (Mt) of dry nodules, and the total estimated metal contents are 168 Mt of manganese, 7.5 Mt of nickel, 6.3 Mt of copper, 0.9 Mt of cobalt, 0.4 Mt of rare-earth elements and 0.3 Mt of molybdenum. A geostatistical resource estimate of three economically prospective areas with a total size of 4498 km2, intensively sampled by box cores, was carried out using ordinary kriging of nodule abundance and metal grades. Within these three nodule fields, 7.14 Mt of dry nodules are classified as measured mineral resources covering an area of 489 km2. Indicated mineral resources amount to 11.2 Mt, covering an area of 825 km2, and inferred mineral resources of 35.5 Mt of dry nodules were estimated for an area of 3184 km2. In total, the metal contents of the three prospective areas amount to 16.8 Mt of manganese, 0.74 Mt of nickel, 0.63 Mt of copper and 0.09 Mt of cobalt.

Marine ferromanganese crusts and nodules, which contain a variety of metals, are potential seabed mineral resources. Given their low growth rates, they are regarded as condensed stratigraphic sections that archive millions of years of paleoceanographic information. Ferromanganese crusts and nodules incorporate trace elements like Cu, Zn, Mo, Tl and Ni during growth. The non-traditional isotopic systems of these metals are increasingly being developed as powerful tracers in the modern ocean and as proxies for the paleo-ocean, due to their tendency to be fractionated by redox-related and/or biological processes. In recent years, both the global variations of metal stable isotopes in ferromanganese crust/nodule surface scrapings and some depth profiles through the ferromanganese crusts were systematically analysed. These studies established the isotopic variability present in ferromanganese crusts, nodules and seawater, explored the isotopic fractionation mechanisms associated with the formation of ferromanganese deposits, and determined whether these ferromanganese crusts can be used as documents of deep water metal isotope compositions and long-term seawater isotope variations. In addition, some isotopes of ferromanganese deposits have been successfully applied to constrain the metal sources and geochemical cycles in the ocean, reconstruct paleo-oceanic redox conditions and seawater isotope record, and reveal continental weathering and climate changes. Nevertheless, it is worth noting that a few limitations of current applications of some non-traditional isotopes as paleoceanographic proxies still remain. Therefore, there is still a great need for a community effort to develop and enhance non-traditional isotope geochemistry of marine ferromanganese crusts and nodules.

Fish-bearing nodules are found in Early Triassic marine strata in many regions, including East Greenland, East Spitsbergen, Northwest Madagascar, Canada, Angola, and South China. A new Olenekian (Early Triassic) conodont biostratigraphic study for stratum that contains fish-bearing nodule levels is conducted based on the Longtan (LT) Section of Nanjing City and the Qingshan (QS) Section of Jurong County, Jiangsu Province, South China. A total of 101 samples were collected at the two sections and three conodont zones were recognized: in ascending order, they are Scythogondolella (Sc.) milleri Zone, Novispathodus (Nv.) pingdingshanensis Zone, and Triassospathodus (Tr.) aff. homeri Zone. The Scythogondolella milleri Zone is globally recognized as the uppermost conodont zone of the Smithian and the base of the Novispathodus pingdingshanensis Zone was previously suggested as the marker of the Smithian-Spathian boundary in the Yangtze region. The fish-bearing-nodule levels of Nanjing and Jurong are within the conodont Scythogondolella milleri Zone, laterally correlated well with the upper part of the Novispathodus waageni Zone in Chaohu of Anhui Province that also contains fish-bearing-nodule levels. The conodont biostratigraphic correlation confirms the Early Triassic fish-bearing-nodule levels in the Lower Yangtze region are coeval, with an end-Smithian in age.

Redox sensitive trace elements in pyrite, including nodules, are increasingly used to infer the chemical conditions of ancient oceans - but considerable uncertainty remains regarding the mechanism and timing of nodule formation. Resolving these uncertainties is important because pyrite nodules must form in connection with the overlying water column, rather than during late diagenesis, to reflect the composition of the global ocean. Existing models for pyrite nodule formation have been specific to pyrite textures from individual sites, and we lack a unified model that can explain the compositional and textural diversity observed in nodules from different localities. In this study we examine ten pyrite nodules from several geological periods (Neoarchean to Carboniferous) using in situ LA-ICP-MS and SHRIMP-SI analyses. We present transects of spot analyses of trace elements (As, Ag, Cu, Co, Ni, Sb and Se) and S isotope ratios for each nodule. The pyrite nodules can be classified according to three main categories: those with (1) little to no trace element or isotopic zonation of the nodule from core to margin, (2) strong zonation from core to margin, and (3) minor zonation near the core but more significant zonation near the margin of the nodule. We further illustrate this zonation with a NanoSIMS element map from an additional pyrite nodule. These results are interpreted to indicate nodule formation along a spectrum between two end-member mechanisms. We suggest that the absence of trace element or isotopic zonation reflects nodule growth by a pathway that is analogous to the pervasive growth mechanism for carbonate nodules. This model involves the production of many nucleation sites that are evenly distributed within the volume that the nodule eventually occupies. Consequently, this mechanism results in a chemically homogenous nodule. Pyrites formed this way are suitable for paleoceanographic reconstruction. The other end-member mechanism is analogous to the concentric growth model for carbonate concretions. In this scenario, the core of the nodule forms first and is followed by the addition of concentric layers - each with a progressively different trace element content and δ34S signature as diagenesis progresses. Despite having limited utility for reconstructing ancient seawater, these late forming nodules may track the evolving availability of bioessential trace elements for the subsurface biosphere with important implications for global biogeochemical cycles. Spatial trends in trace elements and S isotopes thus speak to the mechanisms of pyrite nodule formation and provide a framework for evaluating nodule suitability for a range of paleoenvironmental studies.

The geochemical characteristics and Pb isotope variations in Fe-Mn deposits collected from the South China Sea (SCS) were studied in this paper. The mineralogical and chemical composition data indicate that the deposits are almost all hydrogenetic in origin. Compared with the Fe-Mn deposits in other oceans, the SCS Fe-Mn deposits have a significantly higher Pb content because of higher material supply in addition to a lower growth rate of the deposits. Pb isotope ratios in the surface of the SCS Fe-Mn deposits are relatively uniform, with a characteristic of relatively lower 206Pb/204Pb ratio. The Pb isotopic compositions of the SCS Fe-Mn deposits are controlled by the Pacific Deep Water and local inputs, which include eolian dust from the Asian continent and weathering products from Taiwan, Luzon and SCS submarine volcanic rocks. The continuously increasing 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios along the transect of nodule D581 over the past 3.5 Ma are affected by the stepwise closure of the Luzon Strait that reduced volcanic material supply and the deep current strengthen at the same time.

The success of the future exploitation of the Pacific polymetallic nodule deposits depends on an accurate estimation of their resources, especially in small batches, scheduled for extraction in the short term. The estimation based only on the results of direct seafloor sampling using box corers is burdened with a large error due to the long sampling interval and high variability of the nodule abundance. Therefore, estimations should take into account the results of bottom photograph analyses performed systematically and in large numbers along the course of a research vessel. For photographs taken at the direct sampling sites, the relationship linking the nodule abundance with the independent variables (the percentage of seafloor nodule coverage, the genetic types of nodules in the context of their fraction distribution, and the degree of sediment coverage of nodules) was determined using the general linear model (GLM). Compared to the estimates obtained with a simple linear model linking this parameter only with the seafloor nodule coverage, a significant decrease in the standard prediction error, from 4.2 to 2.5 kg/m2, was found. The use of the GLM for the assessment of nodule abundance in individual sites covered by bottom photographs, outside of direct sampling sites, should contribute to a significant increase in the accuracy of the estimation of nodule resources.

An effective empirical statistical method is developed to improve the process of mineral resource estimation of seabed polymetallic nodules and is applied to analyse 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 analysing 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 analysing a total of 188 sets of nodule samples collected across the TOML areas, comprising box-core samples and towed camera images collected by one of the authors and detailed in [4]. The analysis also relies upon detailed box-core sample measurements from other areas reported by [7]. Numerical results for resource prediction were compared with field measurements, and reasonable agreement has been achieved. 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.

Polymetallic nodule fields provide hard substrate for sessile organisms on the abyssal seafloor between 3,000 and 6,000 m water depth. Deep-seabed mining targets these mineral-rich nodules and will likely modify the consumer-resource (trophic) and substrate-providing (non-trophic) interactions within the abyssal food web. However, the importance of nodules and their associated sessile fauna in supporting food-web integrity remains unclear. Here, we use seafloor imagery and published literature to develop highly-resolved trophic and non-trophic interaction webs for the Clarion-Clipperton Fracture Zone (CCZ, central Pacific Ocean) and the Peru Basin (PB, south-east Pacific Ocean) and to assess how nodule removal will modify these networks. The CCZ interaction web included 1,028 compartments connected with 59,793 links and the PB interaction web consisted of 342 compartments and 8,044 links. We show that knock-down effects of nodule removal resulted in a 17.9% (CCZ) to 20.8% (PB) loss of all compartments and 22.8% (PB) to 30.6% (CCZ) loss of network links. Subsequent analysis identified stalked glass sponges living attached to the nodules as key structural species that supported a high diversity of associated fauna. We conclude that polymetallic nodules are critical for food-web integrity and that their absence will likely result in reduced local benthic biodiversity.

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.

Manganese (polymetallic) nodules on the deep seafloor in the open ocean have attracted great interest because of their economic potential. Visual data on nodules found on the deep seafloor such as photographs and videos have increased exponentially with the recent progress of related technologies. These data are expected to reflect useful information for estimating these mineral resources, as well as understanding their geological origin. Although the size, number, and coverage of manganese nodules have been measured in seafloor images, the burial of such nodules has not been sufficiently examined. This paper focuses on mathematical expression of the burial of the manganese nodules and attempts to quantitatively elucidate relations among burial degree and nodule geological parameters. The results, that is, a dataset obtained by calculations of relations among parameters, are also utilized for considerations of quantitative expression of burial. These considerations are expected to contribute to a better understanding of the geological origin of manganese nodules.

The discharge of fluid–particle mixture tailings can cause serious disturbance to the marine environment in deep-sea mining of polymetallic nodules. Unrecovered nodule fines are one of the key components of the tailings, but little information has been gained on their properties. Here, we report major, trace, and rare earth element compositions of &lt, 63 μm particles produced by the experimental degradation of two types of polymetallic nodules from the Clarion–Clipperton Zone. Compared to the bulk nodules, the fines produced are enriched in Al, K, and Fe and depleted in Mn, Co, Ni, As, Mo, and Cd. The deviation from the bulk composition of original nodules is particularly pronounced in the finer fraction of particles. With X-ray diffraction patterns showing a general increase in silicate and aluminosilicates in the fines, the observed trends indicate a significant contribution of sediment particles released from the pores and cracks of nodules. Not only the amount but also the composition of nodule fines is expected to significantly differ depending on the minimum recovery size of particles at the mining vessel.

Two early Permian radiolarians, Pseudoalbaillella postscalprata Ishiga, 1983 and Pseudoalbaillella sakmarensis ( Kozur, 1981 ), are described from a calcareous nodule of the Permian siliciclastic succession distributed in north-central East Timor. The association probably indicates a Sakmarian (early Cisuralian) age. This is the first report of age-diagnostic Permian radiolarians from East Timor and demonstrates a potential source of well-preserved radiolarians of the Permian siliciclastic succession.

Rhodolith growth and CaCO3 production remain poorly quantified along the SW Atlantic Ocean, and it is difficult to relate the available measurements with biomass estimates. Suboptimal conditions may clarify how harsh environments influence nodule growth and abundance, elucidating their relationship. Off the energetic South American equatorial coast a rhodolith bed (~65 km2), formed mainly by Mesophyllum sp. and Lithophyllum sp., alters the regional sedimentary pattern and sustains a diverse biota. Its nodules present fast growth rates (2.8 mm year−1), but small biomasses (18 nodules∙m−2 covering 26 ± 3% of the substrate), resulting in a CaCO3 production of 163.33 g m−2∙year−1. Despite the small biomass, the bed seems stable, with living and dead nodules both on and inside the substrate. And the suboptimal environment apparently affects growth and abundance independently. Therefore, fast growth rates and relevant structural roles are not necessarily associated with dense rhodolith assemblages, and ecological assessments of rhodolith beds should consider the dynamics of both individual nodules and the whole population.

Minerals in coal provide useful information for not only paleo-environments of peat accumulation, but also for geological evolution during later diagenesis and/or epigenesis. This paper reports new data on coal quality and the mineralogical and geochemical compositions of 17 unaltered (by intrusion) coal samples collected from the Huainan coalfield, providing new insight into the origins and modes of occurrence of the minerals in coal and their geological evolution. The results showed that the studied coal samples were low rank bituminous coal, with low ash yield (11.92&ndash, 38.31%, average 24.80%) and high volatile content (25.13&ndash, 43.43%, average 37.29%). Minerals in the coal mainly included kaolinite and quartz, varying proportions of calcite, siderite, ankerite, and pyrite, and traces of chlorite, zircon, strontianite, apatite, and gorceixite. Typical modes of mineral occurrence could be used to determine the formation stage of minerals. The detrital mineral, occurring as sub-angular to rounded discrete fragments or thin layers intimately admixed with organic matter at particular horizons, was of terrigenous origin, deposited during peat accumulation. Cell infillings, as well as nodule siderites and polycrystalline aggregates of pyrite, precipitated during the syngenetic to early diagenetic stages. Cleat infillings, compressed cell infillings, and fracture infillings precipitated in the epigenetic stage. However, the stage of mineral formation of the pore infilling was difficult to determine. Combined with coal quality, mineralogy, and geochemical analysis, the sedimentary environment of Shanxi Formation was affected by seawater, and Fe-rich hydrothermal fluids filled into the No. 3 coal seam in the epigenetic stage. The sedimentary environment of the No. 8 coal seam had widespread reduction and acid conditions due to basin subsidence, and sulfate-rich hydrothermal fluids may have been formed during the peat deposition stage. In contrast, the peat accumulation environment of the Upper Shihezi Formation was oxidized with a low pH condition. Alkaline fluid then flowed into the No. 13-1 coal seam in the epigenetic stage.

Industrial-scale harvesting of deep-sea mineral resources, such as polymetallic nodules, is likely to have severe consequences for the natural environment. However, the effects of mining activities on deep‑sea ecosystems, sediment geochemistry and element fluxes are still poorly understood. Predicting the environmental impact is challenging due to the scarcity of environmental baseline studies and the lack of mining trials with industrial mining equipment in the deep sea. Thus, currently we have to rely on small-scale disturbances simulating deep-sea mining activities as a first-order approximation to study the expected impacts on the abyssal environment and ecosystem.We have investigated surface sediments in disturbance tracks of seven small-scale benthic impact experiments, which have been performed in four European contract areas for the exploration of polymetallic nodules in the Clarion-Clipperton Zone (CCZ) in the NE Pacific Ocean. These small-scale disturbance experiments were performed 1 day to 37 years prior to our sampling program in the German, Polish, Belgian and French contract areas using different disturbance devices, such as dredges and epibenthic sledges. We show that the depth distribution of solid-phase Mn in the upper 20 cm of the sediments in the CCZ provides a reliable tool for the determination of the disturbance depth. We found that the upper 5–15 cm of the sediments were removed during various small‑scale disturbance experiments in the different contract areas. Transient transport‑reaction modelling for the Polish and German contract areas reveals that the removal of the surface sediments is associated with the loss of reactive labile organic carbon. As a result, oxygen consumption rates decrease significantly after the removal of the surface sediments, and consequently, oxygen penetrates up to tenfold deeper into the sediments inhibiting denitrification and Mn(IV) reduction. Our model results show that the return to steady state geochemical conditions after the disturbance is controlled by diffusion until the reactive labile TOC fraction in the surface sediments is partly re‑established and the biogeochemical processes commence. While the re-establishment of bioturbation is essential, steady state geochemical conditions are ultimately controlled by the burial rate of organic matter. Hence, under current depositional conditions, new steady state geochemical conditions in the sediments of the CCZ are reached only on a millennium-scale even for these small-scale disturbances simulating deep-sea mining activities.

At Kabazi V, level III/4-2, the entire debris from the manufacture of a bifacial preform was found deposited in a small anthropogenic pit. The bifacial preform itself was missing. The fact that it was possible to refit all larger blanks, as well as several chips, from the pit, whereas refits with artifacts discarded on the surface of the corresponding archeological level were not found, underlines the character of the pit’s contents as a closed find sensu stricto. The only explanation for the presence of chips of very small size from the same nodule, alongside the larger ones, in the pit fill is the use of an apron to collect all detached items during the process of flaking. Among the numerous anthropogenic pits from the Crimean Middle Paleolithic, the one found at Kabazi V, level III/4-2, and two other examples from Zaskalanya V and Zaskalnaya VI stand out for the intentional deposition of carefully selected artifacts in them. The sizes of the pits match the volumes of the artifacts deposited, which emphasizes the close relationship between the construction of the pits and the artifacts’ deposition. This article explores the significance of the three cases of artifact deposition referred to above to our understanding of segmented production processes and of why these depositions occurred. The most evident interpretation is that they were caches of equipment stored as insurance for unforeseen circumstances, which is indicative of substantial planning depth and a recurrent use of logistical territories.

The amount and accuracy of nodule resources estimation in the Pacific Ocean are among the main factors conditioning the future exploitation. The estimates are based on the results of classical, direct seafloor sampling. Due to the large distance between sampling sites, the accuracy of assessing nodule resources in small parts of the deposit is low. The accuracy can be increased by using a large number of seafloor photographs taken along the route of the research vessel performing classic sampling. The study conducted for a part of the area administered by Interoceanmetal Joint Organization (IOM) included: (i) determining a model of the relationship between nodule abundance and seafloor nodule coverage using statistical methods, (ii) assessing the accuracy of nodule resources estimation using a geostatistical kriging procedure, (iii) proposing a preliminary classification of resources referring to International Seabed Authority (ISA) classification standards as material for further discussion. It was found that achievement of high accuracy in the estimation of nodule resources (with relative standard error &lt, 5%) in blocks planned for annual exploitation based on direct sampling is difficult. While the use of seafloor photographs increases the accuracy of estimating nodule resources, this improvement is not radical due to the unfavorable, preferential arrangement of photographic data.

Accurate and precise Δʹ17O data are important for quantifying and understanding processes responsible for variations of oxygen triple-isotope ratios in nature. Without universally agreed numerical values of λRL and γRL in the definition Δʹ17O = ln(1 + δ17O) – λRLln(1 + δ18O) – γRL however, as is currently the situation for measurements on rocks and minerals, reported Δʹ17O data may not be directly comparable. Furthermore, the accuracy of Δʹ17O measurements is linked to calibration (at the ppm level) of individual laboratory’s ‘working standard’ O2 relative to the VSMOW water reference or to the VSMOW-SLAP scale, whereas few laboratories have the facility to make high precision δ17O and δ18O measurements on silicates and waters. Both points may be addressed by defining a reference line from measurements of a pair of silicates which differ substantially in oxygen isotopic composition (comparable to the difference between VSMOW and SLAP), rather than by assigning λRL and γRL values arbitrarily. The resulting reference line has no physical significance. However, because Δʹ17O values reported relative to it are independent of the calibration of the working standard O2, this greatly facilitates Δʹ17O reproducibility and comparability. We propose silicate standards for this purpose and report comparative measurements – from two institutions – of the respective δ117O and δ18O values relative to VSMOW, together with Δʹ17O data relative to various assigned reference lines. We also report Δʹ17O measurements of UWG-2 garnet, San Carlos olivine and NBS 28 quartz relative to our reference line. The proposed standards are: (1) KRS (Khitostrov Rock Standard, δ18O = –25.20 ‰), which consists of sintered, fine-grained constituents (primarily garnet) of a very low-δ18O amphibolite-grade Palaeoproterozoic rock from Khitostrov, Karelia, Russia; (2) SKFS (Stevns Klint Flint Standard, δ18O = 33.93 ‰), consisting of thermally dehydrated grains of a high-δ18O nodule of flint sampled from just below the exposed Cretaceous–Palaeogene boundary at Stevns Klint, southeast Zealand Island, Denmark. Both silicates fluorinate readily, using standard laser-assisted procedures, and the associated low blanks allow for overnight pre-treatment. Small quantities of these materials may be supplied, on request, for standardizing Δʹ17O measurements of silicate rocks and minerals according to the proposed procedure.

The seabed included in the Chilean Exclusive Economic Zone (EEZ) has proper conditions to originate and host different ore deposits, but its geological knowledge is scarce and scattered. The existent studies are very limited in terms of geochemical and mineralogical analyses. The most significant non-energetic mineral resources off Chile correspond to Fe-Mn nodules and crusts, phosphorite deposits, gold and titanium placer deposits and massive sulfide deposits. Fe-Mn nodule sites occur in abyssal plains and seamounts, and around volcanic islands, at depths from 2,890 to 4,332 m, and can contain important concentrations of Cu and Ni (up to 1.38% Cu+Ni) and Co (up to 0.53%). Co-rich Fe-Mn crust occurrences have been reported around the Rapanui and Salas y Gómez islands, with Cu+Ni contents up to 0.3%. Phosphorite sites occur in Holocene sedimentary beds of the continental shelf off Peru and northern Chile, with P2O5 average content of 22.6%. Gold placer deposits are found in beaches and channels of southern Chile and may extend offshore probably in submarine canyons. Titanium placer deposits have been evaluated in different beaches of Chile and could also be continued offshore. Platinum anomalies have been found in channels and bays of southernmost Chile. No samples of Volcanogenic Massive Sulfide (VMS) mineralization are known in the Chilean EEZ to date. However, samples of hydrothermal vents, with potential for polymetallic VMS type mineralization, have been recovered around the Rapanui Island, and several seamount and volcanic island chains indicate favorable conditions for formation and preservation of these ore-deposits. The available geological information on the seabed of the Chilean EEZ is insufficient to estimate the real potential of its non-energetic mineral resources.

Highlights • AUV geophysical mapping reveals complex patterns of Mn nodule distribution. • Geophysical and image-based data suggest that Mn nodule occurence relates to sediment thickness. • The role of sediment thickness in nodule development requires detailed geochemical investigation. Abstract The relationship between polymetallic nodules (Mn nodules) and deep-sea stratigraphy is relatively poorly studied and the role of sediment thickness in determining nodule occurrence is an active field of research. This study utilizes geophysical observations from three types of autonomous underwater vehicle (AUV) data (multi-beam bathymetry, sub-bottom profiles and underwater photography) in order to assess this relationship. Multi-beam bathymetry was processed with a pattern recognition approach for producing objective geomorphometric classes of the seafloor for examining their relation to sediment thickness and nodule occurence. Sub-bottom profiles were used for extracting sediment thickness along a dense network of tracklines. Close-range AUV-photography data was used for automated counting of polymetallic nodules and their geometric features and it served as ground truth data. It was observed that higher nodule occurence were related to layers with increased sediment thickness. This evidence reveals the role of local seafloor heterogeneity in nodule formation and suggests that unique patterns of local stratigraphy may affect geochemical processes that promote polymetallic nodule development at local scales.

Quantifying the distribution of caliche nodules in a catchment is a basis toward understanding soil erosion and soil degradation as well as soil-water processes in the soil containing caliche nodules. In this study, field surveys and soil sampling were coupled with spatial and statistical analyses along with image processing to investigate the spatial distribution of caliche nodules and their influencing factors in the Liudaogou catchment, the northern Loess Plateau of China. Results showed that more caliche nodules were present at the top of the mountain, mountain ridges, roadsides, edges of ravines, and other high elevation regions, as represented by comparatively higher caliche nodule coverage (CNC, 11.26–18.28%). Caliche nodules were rarely present in low elevation areas such as the terraced cropland and check dam, as represented by lower CNC (

Deposition of black shale of the Lower Cambrian Niutitang Formation (NTT) of the Yangtze Block, South China, in association with the Ediacaran-Cambrian (E-C) transition was accompanied by widespread formation of phosphate nodules. Petrological and geochemical studies of the nodules and host sedimentary rocks were carried out to elucidate hydrographic conditions of the Early Cambrian ocean. Our results reveal that NTT phosphate nodules are composed principally of concentrically banded carbonate fluorapatite (CFA) that likely reflects changing Eh and pH conditions contemporaneous with diagenetic nodule growth. Accumulation of organic-rich sediment and nodule growth may have been induced and sustained by contemporaneous volcanic and hydrothermal activities on the Yangtze Block. The introduction of voluminous nutrients with volcanic ash, including phosphate and aqueous Fe and Si, promoted the bloom of plankton, including sponges and lower algae leading to organic matter enrichment. Productivity may have been further enhanced by upwelling of phosphate-rich bottom water that resulted in widespread phosphogenesis and formation of phosphate nodules. The hyalophane-quartz association documented from phosphate nodules suggests the possible interaction of K-feldspar-rich volcanic ash and Ba-rich hydrothermal fluids at lower pH levels in association with nodule growth. The formation of phosphate nodules of the Niutitang Formation, then, reflects the complex interaction among primary productivity, volcanic and hydrothermal activity, and the accumulation of organic matter at a critical period of Earth history.

Resumen: En el sector sur de un amplio cañadón denominado Mack Aike (conocido localmente como Chorrillo Grande) -margen norte de la cuenca media del río Gallegos-, se registró un voluminoso núcleo (231 mm x 210 mm x 147 mm) con extracciones multidireccionales producto de la talla de un rodado tamaño bloque de ópalo y calcedonia. En el marco de la tecnología regional del Campo Volcánico Pali Aike (CVPA) el hallazgo de este núcleo es inusual. Se describe la génesis geológica y las características petrográficas macroscópicas del bloque y aquellas tecnológicas del núcleo. El bloque es de origen glaciario y habría estado disponible localmente. Pese a lo atractivo de las materias primas que conforman el núcleo, sus fracturas y discontinuidades lo tornaron de regular y mala calidad para la talla. Esto explica que el 50% de las terminaciones sean quebradas y en charnela y que el 38,23% de las lascas obtenidas hayan sido corticales. Además, la amplia distribución y disponibilidad local de materias primas aptas para la talla habría hecho que no se produjera una explotación más intensa del núcleo. Su aprovechamiento fue oportunista y se lo abandonó.

Evidence for ochre use has been identified at archaeological sites in the eastern Great Lakes Region (North America) dating from the Paleoindian through to the Late Woodland periods. Yet, little is known regarding its procurement practices or if it was a component of established exchange networks. Addressing archaeological evidence for ochre provenance requires an assessment of the geochemical variability of Fe-oxide bearing deposits to determine if they can be differentiated on the basis of their chemical compositions, and if their chemical signatures satisfy the provenance postulate. We present the results of a geochemical characterization and multivariate statistical analysis of Fe-oxide deposits and ochre artifacts. Using Neutron Activation Analysis (NAA) and X-ray Diffraction (XRD), we determined the elemental and mineralogical characteristics of ten Fe-oxide sources in the Great Lakes Region. In addition, we analyzed and compared twenty-three ochre nodule artifacts from the Haney-Cook villages (BcHb-27) and the Ball village (BdGv-3) to determine if they could be geochemically linked to any of the source deposits. The results presented here demonstrate that the Fe-oxide bearing sources each possess unique geochemical signatures, and, that ochre artifacts recovered from the archaeological sites can be linked to source deposits or source zones . Inhabitants of Haney-Cook were most likely engaged in direct procurement of local Fe-oxides, while those at the Ball site used ochres that were acquired either by mid-distance (

A high level of confidence in resource data is a key prerequisite for conducting a reliable economic feasibility study in deep water seafloor mining. However, the acquisition of accurate resource data is difficult when employing traditional point-sampling methods to assess the resource potential of polymetallic nodules, given the vast size of the survey area and high spatial variability in nodule distribution. In this study, we analyzed high-resolution acoustic backscatter intensity images to estimate nodule abundance and increase confidence levels in nodule abundance data. We operated a 120 kHz deep-towed sidescan sonar (DSL-120) system (1×1 m resolution) across a 75 km2 representative area in the Korean Exploration Area for polymetallic nodules in the Northeastern Equatorial Pacific. A deep-towed camera system was also run along two tracks in the same area to estimate the abundance of polymetallic nodules on the seafloor. Backscatter data were classified into four facies based on intensity. The facies with the weakest and strongest backscatter intensities occurred in areas of high slope gradient and basement outcrops, respectively. The backscatter intensities of the two other facies correlated well with the nodule abundances estimated from still-camera images. A linear fit between backscatter intensity and mean nodule abundance for 10 zones in the study area yielded an excellent correlation (r2 = 0.97). This allowed us to compile a map of polymetallic nodule abundance that shows greater resolution than a map derived from the extrapolation of point-sampling data. Our preliminary analyses indicate that it is possible to greatly increase the confidence level of nodule resource data if the relationship between backscatter intensity and nodule abundance is reliably established. This approach has another key advantage over point sampling and image analyses in that detailed maps of mining obstacles along the seafloor are produced when acquiring data on the abundance of polymetallic nodules. The key limitation of this work is a poor correlation between nodule coverage, as observed from photographs, and nodule abundance. Significant additional ground truth sampling using well located box cores should be completed to determine whether or not there is a real correlation between the backscatter and abundance.

The Clarion-Clipperton Fracture Zone (CCFZ) in the northeastern Pacific is a potential area for deep-sea mining, comprises the worldwide largest polymetallic nodule fields and is one of the most difficult to sample and thus unknown ecosystems. Glass sponges (Hexactnellida) represent a main group of benthic deep-sea megafauna, especially hexasterophorid sponges, but only few studies have been published so far. This is the first study focusing on the taxonomy of hexasterophorid sponges from polymetallic nodule fields in the CCFZ and includes descriptions of eight known and six new species: Hyalostylus microfloricomus sp. nov.; Hyalostylus schulzei sp. nov.; Docosaccus nidulus sp. nov.; Holascus spinosus sp. nov.; Caulophacus (Caulophacus) wilsoni sp. nov.; and Chonelasma bispinula sp. nov.

In order to test for paleoenvironmental and paleoecological parameters important in dinosaur evolution, thirty-four fragments of dinosaur eggshell, paleosol carbonates from six localities, and calcite crystals from inside a dinosaur femur were collected from the Campanian to Maastrichtian Baruungoyot and Nemegt formations, Gobi Desert, Mongolia. The samples were examined for diagenesis using light microscopy, SEM, and cathodoluminescence, and each was analyzed for δ13C and δ18O values. Eggshell isotope values plot along two trends of enrichment, with paleosol carbonate nodule values plotting along locality specific trends. Convergence of the trends suggests similar initial conditions among localities. Permian-age detrital zircons in the fossiliferous sediment suggest that enriched eggshell and paleosol carbonate nodule δ13C values may have been caused by phreatic zone diagenetic alteration by waters with an aqueous bicarbonate component derived from interaction and dissolution of Permian calcareous marine host rocks. Our hypothetical model for eggshell diagenesis assumes a stable carbon- and oxygen-isotope domain space delimited by three end members: (1) apparently unaltered eggshell with primary microstructure, (2) non-luminescent eggshell with no preserved microstructure, and (3) luminescent eggshell with no preserved microstructure. The two end members showing no preservation of microstructure indicate different phases of diagenetic alteration in the presence of vadose and phreatic waters. None of the samples analyzed can be shown to be sufficiently unaltered for analysis using standard techniques. Biologically, eggshell is porous to facilitate the movement of gases while an embryo is developing within the egg. Geologically, that same property allows the flow of diagenetic ground waters, which modifies the primary isotopic signature of eggshell.

Ferromanganese oxides on the eastern flank of the Gagua Ridge were collected from a water depth of 4071 m by TV-grab in 2016 and analyzed for their mineralogical and chemical compositions. These oxide fragments were broken from a large poly-core crust and can be divided into three parts: a dense inner nodule, a radial middle crust and a loose outer crust. The close proximity of the nodule and crust is similar to that observed in the amalgamated deposits from the Shatsky Rise, NW Pacific. All samples are mainly composed of Fe-rich vernadite, amorphous FeOOH and associated quartz, plagioclase, pyroxene and Mg-titanomagnetite. The mineralogy, Mn/Fe ratios, rare earth element patterns, and slow growth rates (with a mean value of 6.2 mm/Myr) of the samples reflect their predominantly hydrogenetic origin. Co, Ni, Cu, REY and other critical metals are most enriched in the Mn-rich inner nodule samples, which also have the highest Fe contents. In contrast, the Si and Al contents in the samples of the middle and outer crusts are very high, up to 19 wt% and 6.29 wt%, respectively. Correlation analysis indicates that Li, Sc, Cr, Rb, and Cs tend to concentrate in detrital silica-aluminosilicate phases. The Gagua Ridge samples generally have lower metal contents than the hydrogenetic crusts and nodules from other open ocean regions, which can be attributed to their dilution by detritus and the poor development of a mid-water oxygen minimum zone. However, the incorporation of detritus has little effect on the generation of Fe-Mn oxides in the Gagua Ridge. Based on their mineralogy, textures and chemical variations, the accretion of the hydrogenetic Fe-Mn oxides was initiated in the late Miocene, and the formation of the amalgamated Fe-Mn deposits comprised three stages.