The occurrence phases and enrichment mechanism of rare earth elements in cobalt-rich crusts from Marcus-Wake Seamounts

To explore the occurrence phases and enrichment mechanism of rare earth elements(REEs)in cobalt-rich crusts,this study analyzes the mineral composition and REE contents of the samples from Marcus-Wake Seamounts by XRD,ICP-OES and ICP-MS.The results show that,(1)the cobalt-rich crusts contain the major crystalline mineral(vernadite),the secondary minerals(quartz,plagioclase and carbonate fluorapatite),and a large amount of amorphous ferric oxyhydroxides(FeOOH).(2)The cobalt-rich crusts contains higher Mn(10.83%to 28.76%)and Fe(6.14%to 18.86%)relative to other elements,and are enriched in REEs,with total REE contents of 1563−3238μg/g and Ce contents of 790−1722μg/g.Rare earth element contents of the old crusts are higher than those of the new crusts.Moreover,the non-phosphatized crusts have positive Ce and negative Y anomalies,and yet the phosphatized crusts have positive Ce and positive Y anomalies,indicating that cobalt-rich crusts is hydrogenetic and REEs mainly come from seawater.(3)Analytical data also show that the occurrence phases of elements in cobalt-rich crusts are closely related to their mineral phases.In the non-phosphatized crusts,REEs are adsorbed by colloidal particles into the crusts(about 67%of REEs in the Fe oxide phase,and about 17%of REEs in the Mn oxide phase).In contrast,in the phosphatized crusts(affected by the phosphatization),REEs may combine with phosphate to form rare earth phosphate minerals,and about 64%of REEs are enriched in the residual phase containing carbonate fluorapatite,but correspondingly the influence of Fe and Mn oxide phases on REEs enrichment is greatly reduced.In addition,the oxidizing environment of seawater,high marine productivity,phosphatization,and slow growth rate can promote the REE enrichment.This study provides a reference for the metallogenesis of cobalt-rich crusts in the Pacific.

Distribution characteristics of seamount cobalt-rich ferromanganese crusts and the determination of the size of areas for exploration and exploitation

In 2001, the International Seabed Authority （ISBA） initiated the consideration relating to the Regulations for Prospecting and Exploration for Hydrothermal Polymetallic Sulphides and Cobalt-rich Ferromanganese Crusts in the Area at its 7th session. Since then, the consideration of the Regulations has been mainly focused on the size of areas to be allocated for exploration and exploitation of the crusts. This paper, based on the investigation data and the analysis of the distribution characteristics of the crusts, suggests a model for determining the size of areas for exploration and exploitation of the crusts, taking into account various factors such as production scale, crust thickness and grade, mineable area proportion, recovery efficiency, exploration venture, and so on. Through the modeling, the paper suggests that the exploration area （the area covered by each application for approval of a plan of work for exploration of cobalt-rich crusts） shall be 4 856 km2 and the exploitation area （the mine site area） shall be 1 214 km2, for 20 years of 1 million wet tonnes annual production.

Calcareous Nannofossils and Molecular Fossils in Cobalt-rich Crusts and their Response to the P/E Global Event

A biostratigraphic study on calcareous nannofossils from the CM3D06 Co-rich ferromanganese crust from the Magellan seamounts in the northwestern Pacific enabled estimation of depositional age. The bio-imprinting of calcareous nannofossils and other fossil species suggests six age ranges for the nannofossils： late Cretaceous, late Paleocene, （early, middle, late） Eocene, middle Miocene, late Pliocene, and Pleistocene. Gas chromatography （GC） and gas chromatography-mass spectrometry （GC-MS） were used to test the Co-rich crusts, and a variety of molecular fossils were detected, such as chloroform bituminous ＂A＂ , n-alkane, isoprenoid and sterol. Peak carbon and molecular indices （such as C23-/C24＋, CPI, Pr/Ph, Pr/nC17, Ph/nCxs and j13C） indicate that the parent organic matter is dominated by marine phytoplankton and thallogen whereas there is little input of terrestrial organic matter. Researches on calcareous nannofossils, molecular fossils and molecular organic geochemistry data reveal that the Paleocene/Eocene （P/E） global event is recorded in the cobalt- rich crusts from the northwestern Pacific Ocean. A succession of biomes can be observed near the 85 mm boundary （about 55 Ma）, i.e., the disappearance of the late Cretaceous Watznaueria barnesae and Zigodicus spiralis, and Broisonia parka microbiotas above the P/E boundary, and the bloom of Coccolithus formosus, Discoaster multiradiatus, Discoaster mohleri and Discoaster sp. below the boundary. Typical parameters of molecular fossils, such as saturated hydrocarbon components and carbon-number maxima, Pr/Ph, Pr/C17, Ph/C18, distribution types of sterols, Ts/Tm ratios and bacterial hopane, also exhibit dramatic changes near the P/E boundary. These integrated results illustrate that the biome succession of calcareous nannofossils, relative content of molecular fossils and molecular indices in the cobalt-rich crusts near the 85 mm boundary faithfully record the P/E global event.

Biomineralization of organic matter in cobalt-rich crusts from the Marcus–Wake Seamounts of the western Pacific Ocean

Organic matter in cobalt-rich crust （CRC） from the Marcus-Wake Seamounts of the western Pacific Ocean, Sample CM1D03, has been analyzed to understand the source, geochemistry and mineralization of organic matter, and the mineralization environment. Biomarkers, includingn-alkanes, isoprenoids, terpanes and sterols, have been detected in various layers of the CRC sample, using gas chromatography （GC） and gas chromatography-mass spectrometry （GC-MS）. The content of organic carbon （OC） and its stable isotope （δ13C）, and the combined features of the biomarkers show that the mineralized organic matter in CM1D03 CRC was mainly derived from microorganisms and lower plankton （e.g., bacteria and algae, respectively） from marine surface water, with some terrestrial higher plant components. The ratio of chloroform bitu-men ＂A＂： OC was high in the CRC, between 10.51 and 20.66, showing significant migration characteristics of n-alkanes. Four mineralization categories of organic matter were recognized based on GC chromatograms ofn-alkane molecules： （1） primitive type （bacteria and algae）, which is characterized by moderately mature ofn-alkanes preserving the original characteristics of the organic matter from microorganisms and lower plankton; （2） microbial degradation type, which is characterized by low contents ofn-alkanes and rising baseline in the chromatogram, with the ＂bulge＂ being the products of organic matter by biodegradation; （3） organic matter migration type, which is characterized by low carbon number ofn-alkanes withnC18 as the main peak carbon, without odd even predominance, and low concentrations of isoprenoids and hydro-carbons with high carbon number; and （4） organic matter hydrothermal type, which is characterized by relatively low concentration of small molecular weightn-alkanes, pristane, and phytane, accompanied by higher concentration ofn-alkanes with carbon number greater thannC18. This study shows that biomarkers can record controlling factors of mineralization and their variation.

Morphological description and population structure of an ophiuroid species from cobalt-rich crust seamounts in the Northwest Pacific:Implications for marine protection under deep-sea mining

Many seamounts are covered with cobalt-rich ferromanganese crusts,and are increasingly attracting interest for the potential extraction of valuable mineral resources from deep seabed environments.However,the impacts of potential mining activities on the vulnerable seamount ecosystem remain unclear.To enhance the understanding of connectivity in benthic invertebrate populations in the Northwest Pacific,several seamounts were surveyed and biological samples collected.In the present study,the ophiuroid species Ophioplinthaca defensor is reported for the first time from four deep seamounts in the Northwest Pacific,and described,providing more detailed morphological diagnosis characters.To assess the population structure of the species between and within seamounts,two mitochondrial markers(COI and 16 S)were sequenced.In total,20 haplotypes from 32 COI sequences and 8 haplotypes from 3716 S sequences were recovered.The star-shaped TCS networks and nonsignificant pairwise population differences reveal the absence of distinct population structures between and within seamounts.In addition,the O.defensor population seemed to have undergone a demographic expansion in history.This is the first study on the genetic population structure of a benthic invertebrate from seamounts in the Northwest Pacific,and this results suggest a potentially high,long distance dispersal capacity in O.defensor between seamounts,which could inform the development of the Regional Environmental Management Plans for the cobalt-rich crust seamounts in the area.

Geochemistry of rare earth elements in cobalt-rich crusts from the Mid-Pacific M seamount

Rare earth elements（REEs） and major elements of 25 cobalt-rich crusts obtained from different depths of Mid-Pacific M seamount were analyzed using inductively coupled plasma-atomic emission spectrometer and gravimetric method.The results showed that they were hydrogenous crusts with average ∑REE content of 2084.69 μg/g and the light REE（LREE）/heavy REE（HREE） ratio of 4.84.The shale-normalized REE patterns showed positive Ce anomalies.The total content of strictly trivalent REEs increased with water depth.The Ce content and LREE/HREE ratios in Fe-Mn crusts above 2000 m were lower than those below 2000 m.The change in REE with water depth could be explained by two processes：adsorptive scavenging by setting matters and behaviors of REE in seawater.However, the Ce abundance took no obvious correlation with water depth reflects the constant Ce flux.The Ce in crusts existed mainly as Ce（IV）, implying that the oxidative-enriching process was controlled by kinetic factors.

Noble Gas Isotopic Compositions of Cobalt-rich Ferromanganese Crusts from the Western Pacific Ocean and Their Geological Implications

Noble gas isotopic compositions of various layers in three-layered （outer, porous and compact layers） cobalt-rich ferromanganese crusts and their basaltic and phosphorite substrates from the western Pacific Ocean were analyzed by using a high vacuum gas mass spectrum. The analytical results show that the noble gases in the Co-rich crusts have derived mainly from the ambient seawater, extraterrestrial grains such as interplanetary dust particles （IDPs） and wind-borne continental dust grains, and locally formation water in the submarine sediments, but different noble gases have different sources. He in the crusts derives predominantly from the extraterrestrial grains, with a negligible amount of radiogenic He from the eolian dust grains. Ar is sourced mainly from the dissolved air in the seawater and insignificantly from radiogenic Ar in the eolian continental dust grains or the formation water. Xe and Ne derive mainly from the seawater, with minor amounts of extraterrestrial Xe and Ne in the IDPs. Compared with the porous and outer layers, the compact layer has a relatively high 4He content and lower 3He/4He ratios, suggesting that marine phosphatization might have greatly modified the noble gas isotopic compositions of the crusts. Besides, the 3He/4He values of the basaltic substrates of the cobalt-rich crusts are very low and their R/R. ratios are mostly 〈0.1 R., which are similar to that of phosphorite substrates （0.087 R.）, but much lower than that of fresh submarine MORB （8.75±14 Ra） or seamount basalts （3-43 Ra）, implying that the basaltic substrates have suffered strong water/rock interaction and reacted with radiogenic ^4He and P-rich upwelling marine currents during phosphatization. The trace elements released in the basalt/seawater interaction might favor the growth of cobalt-rich crusts. The relatively low ^3He/^4He values in the seamount basalts may be used as an important exploration criterion for the cobalt-rich ferromanganese crusts.

An Effective Method to Determine the Distribution Boundary of Cobalt-Rich Fe-Mn Crusts on a Guyot: Synchronous Application of Sub-bottom Profiling and Deep-Sea Video Recording

Determining the upper boundary of the cobalt-rich crust distribution of a guyot is important for estimating the mineral resources available, however, it has also long been an unsolved question. Correlations between the sub-bottom structures, revealed by sub-bottom profiling, and crust distribution can be revealed for the first time by the synchronous application of sub-bottom profiling and deep-sea video recording. The lower boundary of the sediment corresponds with the upper boundary of the crust. By analysis of these two kinds of data, the lower boundary of the sediment can be determined; therefore, the upper boundary of the crust distribution can be deduced. According to this method of analysis, the upper boundary of water depth of crust distribution of a seamount in the western Pacific is about 1 560 m.

Resources calculation of cobalt-rich crusts with the grid subdivision and integral method

On the basis of three geological models and several orebody boundaries, a method of grid subdivision and integral has been proposed to calculate and evaluate the resources of cobalt-rich crusts on the seamounts in the central Pacific Ocean. The formulas of this method are deduced and the interface of program module is designed. The method is carried out in the software ＂Auto mapping system of submarine topography and geomorphology MBChart＂. This method and program will possibly become a potential tool to calculate the resources of seamounts and determine the target diggings for China＇ s next Five-year Plan.

Simulation of Cobalt-Rich Crust’s Crushing Process Based on ANSYS

It is a great concern in international oceanology to mine cobalt-rich crust. At present, spiral mining head is regarded as the best crushing scheme. Based on the dynamic model of spiral mining head, the of cobalt crust’s crushing process was simulated with the ANSYS software. The material model of Johnson and Cook Plasticity, maximal princi- pal stress failure criterion, and eroding contact arithmetic were selected. At the same time, the influence of cutting depth, feed speed, rotational speed of mining head on torque and force subjected by mining head was taken into account. At last a computer simulation model of crushing process of cobalt crust was established. By analyzing simulation results, the relationships among these controllable process parameters, torque and force can be obtained, which will provide a technical reference for practical mining system.

Ecological functions of uncultured microorganisms in the cobaltrich ferromanganese crust of a seamount in the central Pacific are elucidated by fosmid sequencing

Cobalt-rich ferromanganese is an important seafloor mineral and is abundantly present in the seamount crusts. Such crusts form potential hotspots for biogeochemical activity and microbial diversity, yet our understanding of their microbial communities is lacking. In this study, a cultivation-independent approach was used to recover genomic information and derive ecological functions of the microbes in a sediment sample collected from the cobalt-rich ferromanganese crust of a seamount region in the central Pacific. A total of 78 distinct clones were obtained by fosmid library screening with a 16S rRNA based PCR method. Proteobacteria and MGI Thaumarch-aeota dominated the bacterial and archaeal 16S rRNA gene sequence results in the microbial community. Nine fosmid clones were sequenced and annotated. Numerous genes encoding proteins involved in metabolic functions and heavy metal resistance were identified, suggesting alternative metabolic pathways and stress responses that are essential for microbial survival in the cobalt-rich ferromanganese crust. In addition, genes that participate in the synthesis of organic acids and exoploymers were discovered. Reconstruction of the metabolic pathways revealed that the nitrogen cycle is an important biogeochemical process in the cobalt-rich ferromanganese crust. In addition, horizontal gene transfer （HGT） events have been observed, and most of them came from bacteria, with some occurring in archaea and plants. Clone W4-93a, belonging to MGI Thaumarch-aeota, contained a region of gene synteny. Comparative analyses suggested that a high frequency of HGT events as well as genomic divergence play important roles in the microbial adaption to the deep-sea environment.

板状富钴结壳浮选优化试验研究

在"十五"期间所开发板状富钴结壳浮选流程的基础上,进行了药剂制度的优化,优化后的工艺可以获得较高的浮选指标,该工艺流程为下一步富钴结壳的工业化生产提供了技术保障。优化后的选矿指标为:富钴结壳精矿含钴、锰分别为0.51%、17.82%,钴、锰的回收率分别为96.07%、96.65%。

X射线荧光光谱在海洋地质及矿产资源调查分析中的应用评介

大洋地质与矿产资源调查是我国20世纪80年代以来开展并迅速发展的一项重要科学事业,地质分析技术、特别是X射线荧光光谱(XRF)技术为此做出了重要贡献。文章收集了1982—2019年间X射线荧光光谱在我国大洋地质及矿产资源调查研究中的应用文献共计56篇,文章从船载现场分析、海洋地质标准物质研制及海洋沉积物、大洋多金属结核、海山富钴结壳、海底磷矿岩和深海稀土资源等海底矿产样品分析等几方面评介了X射线荧光光谱技术的应用,特别是X射线荧光光谱在我国船载现场分析和海洋地质标准物质研制中发挥的重要作用。这些成果充分展现了分析技术在地质工作、特别是地质调查和资源评价中的作用和意义。文章强调:高质量、具有国际影响力的海洋地质标准物质是我国海洋地球化学数据及其研究成果的质量保证;船载现场分析是加快海洋地质与矿产资源调查评价进程、提高航次效率的强有力手段。已有成果为今后更高质量、更快速有效地完成海洋地质与矿产资源调查分析任务提供了宝贵经验。全篇引文98篇。

Nanometer properties of oceanic polymetallic nodules and cobalt-rich crusts

An ammonia leaching process was utilized to extract Co, Ni and Cu from oceanic polymetallic nodules, whereas an acid leaching process was utilized to extract Co, Ni, Cu, Zn and Mn from cobalt-rich crusts. Both processes produced nanometer materials-ammonia leaching residue and acid leaching residue. A systematic study was conducted on the phase, composition and physicochemistry properties of these residues. The result shows that both residues contain a large amount of nanometer minerals. Ammonia leaching residue mainly consists of rhodochrosite, with the average grain diameter of 17.9 nm; whereas the acid leaching residue mainly consists of well-developed bassanite, with the average grain deameter of 9.5 nm. The bassanite also has a microporous structure, the volume of the pore space is 1.23×10-2 mL/g. Both the ammonia and acid leaching residues have a large specific surface area, and they display a strong adsorption capacity to saturate sodium chloride vapour, N2 and SO2. Both residues have high

Automated multi-scale classification of the terrain units of the Jiaxie Guyots and their mineral resource characteristics

Given the advances in satellite altimetry and multibeam bathymetry,benthic terrain classification based on digital bathymetric models(DBMs)has been widely used for the mapping of benthic topographies.For instance,cobaltrich crusts(CRCs)are important mineral resources found on seamounts and guyots in the western Pacific Ocean.Thick,plate-like CRCs are known to form on the summit and slopes of seamounts at the 1000–3000 m depth,while the relationship between seamount topography and spatial distribution of CRCs remains unclear.The benthic terrain classification of seamounts can solve this problem,thereby,facilitating the rapid exploration of seamount CRCs.Our study used an EM122 multibeam echosounder to retrieve high-resolution bathymetry data in the CRCs contract license area of China,i.e.,the Jiaxie Guyots in 2015 and 2016.Based on the DBM construted by bathymetirc data,broad-and fine-scale bathymetric position indices were utilized for quantitative classification of the terrain units of the Jiaxie Guyots on multiple scales.The classification revealed four first-order terrain units(e.g.,flat,crest,slope,and depression)and eleven second-order terrain units(e.g.,local crests,depressions on crests,gentle slopes,crests on slopes,and local depressions,etc.).Furthermore,the classification of the terrain and geological analysis indicated that the Weijia Guyot has a large flat summit,with local crests at the southern summit,whereas most of the guyot flanks were covered by gentle slopes.“Radial”mountain ridges have developed on the eastern side,while large-scale gravitational landslides have developed on the western and southern flanks.Additionally,landslide masses can be observed at the bottom of these slopes.The coverage of local crests on the seamount is∼1000 km^(2),and the local crests on the peak and flanks of the guyots may be the areas where thick and continuous plate-like CRCs are likely to occur.

Variations of calcareous nannofossils of cobalt-rich crusts and geological records at the Eocene-OIigocene transition in western Pacific seamounts

Two records of the crust laminae from the Marcus-Wake Seamounts and the Magellan Seamount were biostratigraphically studied. Based on biological imprints of the calcareous nannofossils, the geological ages of the two records were determined, with CM1D03 from the Marcus-Wake Seamounts being of late Paleocene to Pleistocene and CM3D06 from the Magellan Seamount of Late Cretaceous （more than 70.0 Ma）. There are the obvious temporal-spatial differences in the initial formation period and enrichment characteristics of the cobalt-rich crusts of the two seamount chains and differences in the combination and distribution of microfossils in the inner crust layers between the seamounts. These differences are due to the adaptabilities of oceanic species in different environments. Ecological research was carried out in terms of population size of the calcareous nannofossi｜s preserved in the crustal layers to discern the relation of the geological events at the Eocene-Oligocene （E/O） tran- sition. The results show the transitions and recombination of species in the biotic community during the E/O transition obvi- ously corresponded to 25 mm depth in the CM1D03 crust and 58 mm depth in the CM3D06 crust. The changes in biological species and the formation of particular ecological structures indicate the adaptive response of the paleo-biological community in the western Pacific Ocean to the global cold-climate events and the close correlation between the formation of the crust and the global climate change.

高等级公路软基设计中的一些问题

阐述了一些高等级公路设计中,对公路软基处理的方法.

Geochemical characteristics and metal element enrichment in crusts from seamounts of the Western Pacific

Elemental geochemistry is an essential part of understanding mineralization mechanisms. In this paper, a data set of 544 cobalt crust samples from seamounts of the Western Pacific are used to study the enrichment characteristics of metal elements. REE normalization is utilized to reveal the origin of the crusts; effects of water depth on Co enrichment and impacts ofphosphatization on mineral quality are discussed to obtain the evolution of these marine mineral deposits, which gives support to further resource assessment. Conclusions are reached as follows： 1） Elemental abundances, inter-element relation- ships, and shale-normalized REE patterns for phosphate- poor crusts from different locations reflect hydrogenetic origin of the crusts. EFs （enrichment coefficients） of REE exhibit exponential increase from surface sediments to phosphorite to polymetallic nodules to crusts, suggesting that the improved degree of hydrogeneous origin induces the enrichment of REE. 2） The crusts in the Western Pacific, formed through hotspot produced guyots trails, have relatively lower REE than those in the Mid-Pacific. The latter could be attributed to the peculiar submarine topography of seamounts formed by intraplate volcanism. 3） The non-phosphatized younger crust layers have 40% higher Co than the phosphatized older layers. This indicates the modification of the elemental composition in these crusts by phosphatization. A general depletion of hydroxide-dominated elements such as Co, Ni, and Mn and enrichment of P, Ca, Ba, and Sr is evident in phosphatized crusts, whereas non-phosphatized younger generation crusts are rich in terrigenous aluminosilicate detrital matter. 4） Co increases above the carbonate compensation depth （CCD） from less than 0.53% to over 0.65% in seamount regions with water depth of less than 2,500 m, suggesting the significance of the dissolution of carbonate in the sea water column to the growth and composition of crusts.