I. INTRODUCTIONA lot of work on marine Fe-Mn nodules has been done. However, few reports about the study of Fe-Mn nodules in the Mariana Ridge and the West Philippine Basin are known. The purpose of this note is to re...I. INTRODUCTIONA lot of work on marine Fe-Mn nodules has been done. However, few reports about the study of Fe-Mn nodules in the Mariana Ridge and the West Philippine Basin are known. The purpose of this note is to report in detail the geochemical characteristics展开更多
Ferromanganese crusts and nodules are important submarine mineral resources that contain various metal elements with significant economic value. In this study, polymetallic crusts and nodules obtained from the South C...Ferromanganese crusts and nodules are important submarine mineral resources that contain various metal elements with significant economic value. In this study, polymetallic crusts and nodules obtained from the South China Sea (SCS) were determined by using X-ray power diffraction (XRD), Raman spectroscopy (RS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) to systematically investigate and analyze the mineralogical and spectral characteristics of the Fe-Mn minerals. XRD measurements revealed that the SCS polymetallic crusts and nodules were composed of vernadite, quartz, and plagioclase. The nodules also contained todorokite. The Fe-phase minerals of the SCS crusts and nodules were composed of amorphous Fe oxide/hydroxide, and the Mn- and Fe-phases minerals exhibited relatively poor degrees of crystallization. FTIR results showed that the Fe-Mn minerals in the crusts and nodules included a large number of surface hydroxyl groups. These surface hydroxyl groups contained protons that could provide reactive sites for complexation of ore-forming elements in seawater. XPS results indicated that the surfaces of the Fe-Mn minerals mainly contained Fe, Mn, and O. Fe was present in the trivalent oxidation state, while Mn, which may contain several bivalent oxidation state, was present in the tetravalent and trivalent oxidation states. The SCS polymetallic crusts and nodules were compared with Pacific seamount crusts, and results showed that the surface hydroxyl (-OH) groups of the SCS crusts and nodules numbered more than the lattice oxygen (O^2-). But the lattice oxygen of Pacific seamount crusts numbered more than the surface hydroxyl groups. This characteristic indicated that the degree of crystallization of Fe-Mn minerals from the Pacific Ocean was higher than that of minerals from the South China Sea. Comprehensive studies showed that ore-forming elements in the interface between seawater and the Fe-Mn minerals in the submarine ferromanganese crusts and nodules employed the following enrichment mechanisms: (1) the metal ion complexed with the surface hydroxyl of Fe-Mn minerals to form hydroxyl complexes, which were connected by coordination bonds or stable inner-sphere complexes that exchanged protons on the mineral surfaces; (2) the charged surfaces of the minerals and metal cations formed outer-sphere complexes, which made up the electrostatic double layer, through electrostatic adsorption; and (3) the metal cations isomorphously exchanged the Mn and Fe ions of the mineral lattice structure.展开更多
The rare earth elements(REE) composition of the polymetallic crusts and nodules obtained from the South China Sea(SCS) were analyzed through inductively coupled plasma mass spectrometry.Results revealed great diff...The rare earth elements(REE) composition of the polymetallic crusts and nodules obtained from the South China Sea(SCS) were analyzed through inductively coupled plasma mass spectrometry.Results revealed great differences in the REE abundances(∑REE) of the SCS polymetallic crusts and nodules; the crusts show the highest ∑REE, whereas the nodules exhibit the lowest ∑REE. The similarity in their NASC-normalized patterns, the enriched light REE(LREE), the markedly positive Ce anomaly(δCe), and the non-or weakly positive Eu anomaly(δEu), suggest that the polymetallic crusts and nodules are of hydrogenetic origin. Moreover, the REE contents and their relevant parameters are quite different among the various layers of the crusts and nodules, which probably results from the different marginal sea environments and mineral assemblages of the samples. The growth profiles of the SCS polymetallic crusts and nodules reveal the tendency ∑REE and δCe to slightly increase from the outer to the inner layers, suggesting that the growth environments of these samples changed smoothly from an oxidizing to a relatively reducing environment; in addition, the crust ST1 may have experienced a regressive event(sea-level change) during its growth, although the REE composition of the seawater remained relatively stable. On the basis of the regional ∑REE distribution in the SCS crusts and nodules,the samples collected near the northern margin were influenced by terrigenous material more strongly compared with the other samples, and the REE contents are relatively low. Therefore, the special geotectonic environment is a significant factor influencing the abundance of elements, including REE and other trace elements. Compared with the oceanic seamount crusts and deep-sea nodules from other oceans,the SCS polymetallic crusts and nodules exhibit special REE compositions and shale-normalized patterns, implying that the samples are of marginal sea-type Fe-Mn sedimentary deposits, which are strongly affected by the epicontinental environment, and that they grew in a more oxidative seawater environment. This analysis indicates that the oxidized seawater environment and the special nano property of their Fe-Mn minerals enrich the REE adsorption.展开更多
Kr and Xe nuclide abundance and isotopic ratios of the uppermost layer of Fe-Mn Crusts from the western and central Pacific Ocean have been determined. The results indicate that the Kr and Xe isotopic composi-tions, l...Kr and Xe nuclide abundance and isotopic ratios of the uppermost layer of Fe-Mn Crusts from the western and central Pacific Ocean have been determined. The results indicate that the Kr and Xe isotopic composi-tions, like that of He, Ne and Ar, can be classified into two types: low3He/4He type and high3He/4He type. The low3He/4He type crusts have low84Kr and132Xe abundance, while the high3He/4He type crusts have high84Kr and132Xe abundance. The82Kr/84Kr ratios of the low3He/4He type crusts are lower than that of the air, while the83Kr/84Kr and86Kr/84Kr ratios are higher than those of the air. The Kr isotopic ratios of the high-er3He/4He type crusts are quite similar to those of the air. The128Xe/132Xe,130Xe/132Xe and131Xe/132Xe ratios of the low3He/4He type sample are distinctly lower than those of the air, whereas the129Xe/132Xe,134Xe/132Xe and136Xe/132Xe ratios are higher than those of the air. The low3He/4He type samples have the diagnostic characteristics of the MORB, with excess129, 131, 132, 134, 136Xe relative to130Xe compared with the solar wind. The128Xe/132Xe,130Xe/132Xe and131Xe/132Xe ratios of the high3He/4He type samples are slightly higher than those of the air, and the129Xe/132Xe,134Xe/132Xe and136Xe/132Xe ratios are qiute similar to those of the air. The noble gases in the Fe-Mn crusts are derived from the lower mantle, and they are a mixture of lower mantle primitive component, radiogenic component and subduction recycled component. The helium isotopic ra-tios of the low mantle reservoir are predominantly controlled by primitive He (3He) and U and Th radiogenic decayed He (4He), but the isotopic ratios of the heavier noble gases, such as Ar, Kr and Xe, are controlled to different extent by recycling of subduction components. The difference of the noble isotopic compositions of the two type crusts is the result of the difference of the noble isotopic composition of the mantle source reservoir underneath the seamounts the crusts occurred, the noble gases of the high3He/4He type crusts are derived mainly from EM-type lower mantle reservoir, and the noble gases in the low3He/4He type crusts are derived mainly from HIMU-type lower mantle reservoir.展开更多
X-ray diffraction and selective chemical dissolution methods were used to investigate the composition of Mn oxide minerals in Fe-Mn nodules of several main types of soils in China. The changes of relative intensity of...X-ray diffraction and selective chemical dissolution methods were used to investigate the composition of Mn oxide minerals in Fe-Mn nodules of several main types of soils in China. The changes of relative intensity of X-ray diffraction patterns were studied both before and after chemically selective dissolution. It was found that lithiophorite was a common Mn oxide in all examined Fe-Mn nodules. Todorokite, however, was a predominant Mn oxide in Fe-Mn nodules in caf-aquic Vertisols of Linyi, Shandong Province. The Fe-Mn nodules of arp-udic Luvisols in Wuhan and Zaoyang, Hubei Province, contained birnessite and vernadite. Hollandite was found in Fe-Mn nodules of alt-udic Ferrisols of Yizhang, Hunan Province; arp-udic Luvisols of Zaoyang, Hubei Province; and cal-aquic Vertisols of Linyi, Shandong Province. The Fe-Mn nodules in alt-udic Ferrisols of Guiyang, Hunan Province, had a few coronadites. Mineralogy of Mn oxide minerals in soil Fe-Mn nodules was related to soil environment, soil types and quantities of relevant cations.展开更多
Polymetallic nodules and cobalt (Co)-rich crusts are enriched in platinum-group elements (PGEs),especially platinum (Pt) and may be important sinks of PGEs.At present,little information is available on PGEs in polymet...Polymetallic nodules and cobalt (Co)-rich crusts are enriched in platinum-group elements (PGEs),especially platinum (Pt) and may be important sinks of PGEs.At present,little information is available on PGEs in polymetallic nodules,and their geochemical characteristics and the causes of PGEs enrichment are unclear.Here PGEs of polymetallic nodules from abyssal basin in the Marcus-Wake Seamount area of the Northwest Pacific Ocean are reported and compared with the published PGEs data of polymetallic nodules and Co-rich crusts in the Pacific.The total PGEs (ΣPGE) content of polymetallic nodules in study area is 258×10^–9) in average,markedly higher than that of Clarion-Clipperton Zone (CCZ) nodules (ΣPGE=127×10^–9) and lower than that of Co-rich crusts in the Marcus-Wake Seamount (ΣPGE=653×10^–9),similar to that of Co-rich crusts in the South China Sea(ΣPGE=252×10^~–9).The CI chondrite-normalized PGEs patterns in different regions of polymetallic nodules and cobalt-rich crusts are highly consistent,with all being characterized by positive Pt and negative Pd anomalies These results,together with those of previous studies,indicate that PGEs in polymetallic nodules and Co-rich crusts are mainly derived directly from seawater.Pt contents of polymetallic nodules from the study area are negatively correlated with water depth,and Pt/ΣPGE ratios in nodules there are also lower than those of the Corich crusts in the adjacent area,indicating that sedimentary water depth and oxygen fugacity of ambient seawater are the possible important controlling factors for Pt accumulation in crusts and nodules.展开更多
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 process...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展开更多
Polymetallic nodules and crusts are two of the most important mineral deposits in the ocean. They are rich in rare earth elements (REEs), iron, manganese, copper, cobalt, nickel, and other useful metals. This paper ...Polymetallic nodules and crusts are two of the most important mineral deposits in the ocean. They are rich in rare earth elements (REEs), iron, manganese, copper, cobalt, nickel, and other useful metals. This paper discussed the analysis of 25 nodule and crust samples collected from the South China Sea, the Pacific, Atlantic, and Indian Oceans. The samples were analyzed for REE content by ICP-MS/AES. The average REE concentration was found to be 1096.96×10^-6 in the nodules and 1623.88×10^-6 in the crusts. Both of these values are much higher than those recorded in Earth's dry-land crust and sedimentary rocks. This REE enrichment is mainly controlled by the absorption of ferromanganese oxides and clay minerals in the nodules and crusts and the high levels of REEs in seawater and sediments. High cerium enrichment in the nodules and crusts may lead to more effective exploitation of REEs in the future.展开更多
The noble gas nuclide abundances and isotopic ratios of the upmost layer of Fe-Mn crusts from the western and central Pacific Ocean have been determined. The results indicate that the He and Ar nuclide abundances and ...The noble gas nuclide abundances and isotopic ratios of the upmost layer of Fe-Mn crusts from the western and central Pacific Ocean have been determined. The results indicate that the He and Ar nuclide abundances and isotopic ratios can be classified into two types: low 3He/4He type and high 3He/4He type. The low 3He/4He type is characterized by high 4He abundances of 191×10?9 cm3·STP·g?1 on average, with variable 4He, 20Ne and 40Ar abundances in the range (42.8?421)×10?9 cm3·STP·g?1, (5.40?141)×10?9 cm3·STP·g?1, and (773?10976)×10?9 cm3·STP·g?1, respectively. The high 3He/4He samples are characterized by low 4He abundances of 11.7×10?9 cm3·STP·g?1 on average, with 4He, 20Ne and 40Ar abundances in the range of (7.57?17.4)×10?9 cm3·STP·g?1, (10.4?25.5)×10?1 cm3·STP·g?1 and (5354?9050)×10?9 cm3·STP·g?1, respectively. The low 3He/4He samples have 3He/4He ratios (with R/RA ratios of 2.04?2.92) which are lower than those of MORB (R/R A=8±1) and 40Ar/36Ar ratios (447?543) which are higher than those of air (295.5). The high 3He/4He samples have 3He/4He ratios (with R/R A ratios of 10.4?12.0) slightly higher than those of MORB (R/R A=8±1) and 40Ar/36Ar ratios (293?299) very similar to those of air (295.5). The Ne isotopic ratios (20Ne/22Ne and 21Ne/22Ne ratios of 10.3?10.9 and 0.02774?0.03039, respectively) and the 38Ar/36Ar ratios (0.1886?0.1963) have narrow ranges which are very similar to those of air (the 20Ne/22Ne, 21Ne/22Ne, 38Ar/36Ar ratios of 9.80, 0.029 and 0.187, respectively), and cannot be differentiated into different groups. The noble gas nuclide abundances and isotopic ratios, together with their regional variability, suggest that the noble gases in the Fe-Mn crusts originate primarily from the lower mantle. The low 3He/4He type and high 3He/4He type samples have noble gas characteristics similar to those of HIMU (High U/Pb Mantle)-and EM (Enriched Mantle)-type mantle material, respectively. The low 3He/4He type samples with HIMU-type noble gas isotopic ratios occur in the Magellan Seamounts, Marcus-Wake Seamounts, Marshall Island Chain and the Mid-Pacific Seamounts whereas the high 3He/4He type samples with EM-type noble gas isotopic ratios occur in the Line Island Chain. This difference in noble gas characteristics of these crust types implies that the Magellan Seamounts, Marcus-Wake Seamounts, Marshall Island Chain, and the Mid-Pacific Seamounts originated from HIMU-type lower mantle material whereas the Line Island Chain originated from EM-type lower mantle material. This finding is consistent with variations in the Pb-isotope and trace element signatures in the seamount lavas. Differences in the mantle source may therefore be responsible for variations in the noble gas abundances and isotopic ratios in the Fe-Mn crusts. Mantle degassing appears to be the principal factor controlling noble gas isotopic abundances in Fe-Mn crusts. Decay of radioactive isotopes has a negligible influence on the nuclide abundances and isotopic ratios of noble gases in these crusts on the timescale of their formation.展开更多
Cadmium (Cd) pollution in agricultural soils has become a severe threat to food security and human health in recent years. Stable Cd isotopes are a potentially powerful tool for identifying the sources of Cd in soils....Cadmium (Cd) pollution in agricultural soils has become a severe threat to food security and human health in recent years. Stable Cd isotopes are a potentially powerful tool for identifying the sources of Cd in soils. However, many Earth surface processes, including adsorption, leaching, and biogeochemical cycles in plants, may generate Cd isotope fractionation, which can complicate the potential application of Cd isotopes in tracing the sources of Cd pollution in soils. In this work, the Cd isotope compositions of typical Fe-Mn nodules (FMNs) and surrounding soils in two different soil profiles are investigated. Our results show that the FMNs in lower layers (i.e., C and W horizons) are isotopically lighter than the surrounding soils by –0.114‰ to –0.156‰ (Δ114/110CdFMN-soil). We interpret this fractionation as the result of preferential adsorption of isotopically light Cd onto the surface of goethite. In the upper layers (i.e., P and A horizons), the Δ114/110CdFMN-soil values are more negative in the P horizon (–0.213‰ to –0.388‰) but more positive in the A horizon (0.061‰ to 0.204‰). We interpret these fractionations as the result of natural biogeochemical processes (i.e., leaching and biological cycling) during soil development. Soil leaching preferentially releases isotopically heavy Cd into the underlying soil (i.e., P horizon), shifting the topsoil towards lower δ114/110Cd values but the underlying soils towards higher δ114/110Cd values. Moreover, biological cycling contributes isotopically heavy Cd to the topsoil, probably shifting the topsoil towards higher δ114/110Cd values. Our study demonstrates that the formation of Fe oxyhydroxides, leaching, and biological cycling can considerably modify the soil Cd isotope signature, highlighting the need to consider natural biogeochemical processes when using Cd isotopes to trace heavy metal pollution in soils.展开更多
文摘I. INTRODUCTIONA lot of work on marine Fe-Mn nodules has been done. However, few reports about the study of Fe-Mn nodules in the Mariana Ridge and the West Philippine Basin are known. The purpose of this note is to report in detail the geochemical characteristics
基金The National Natural Science Foundation of China under contract Nos 40473024 and 40343019the research fund from State Key Laboratory for Mineral Deposits Research in Nanjing University under contract No.20-15-07+3 种基金the Investigation and Development of Marine Resources during the 12th Five Year Plan Project under contract No.DY125-13-R-05the Doctoral Program of Higher Education Research Fund under contract Nos 20040558049 and 20120171130005the Project of High Level Talents in Colleges of Guangdong Province(2011)the Fundamental Research Funds for Central Universities under contract Nos 16lgjc11,12lgjc05 and 09lgpy09
文摘Ferromanganese crusts and nodules are important submarine mineral resources that contain various metal elements with significant economic value. In this study, polymetallic crusts and nodules obtained from the South China Sea (SCS) were determined by using X-ray power diffraction (XRD), Raman spectroscopy (RS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) to systematically investigate and analyze the mineralogical and spectral characteristics of the Fe-Mn minerals. XRD measurements revealed that the SCS polymetallic crusts and nodules were composed of vernadite, quartz, and plagioclase. The nodules also contained todorokite. The Fe-phase minerals of the SCS crusts and nodules were composed of amorphous Fe oxide/hydroxide, and the Mn- and Fe-phases minerals exhibited relatively poor degrees of crystallization. FTIR results showed that the Fe-Mn minerals in the crusts and nodules included a large number of surface hydroxyl groups. These surface hydroxyl groups contained protons that could provide reactive sites for complexation of ore-forming elements in seawater. XPS results indicated that the surfaces of the Fe-Mn minerals mainly contained Fe, Mn, and O. Fe was present in the trivalent oxidation state, while Mn, which may contain several bivalent oxidation state, was present in the tetravalent and trivalent oxidation states. The SCS polymetallic crusts and nodules were compared with Pacific seamount crusts, and results showed that the surface hydroxyl (-OH) groups of the SCS crusts and nodules numbered more than the lattice oxygen (O^2-). But the lattice oxygen of Pacific seamount crusts numbered more than the surface hydroxyl groups. This characteristic indicated that the degree of crystallization of Fe-Mn minerals from the Pacific Ocean was higher than that of minerals from the South China Sea. Comprehensive studies showed that ore-forming elements in the interface between seawater and the Fe-Mn minerals in the submarine ferromanganese crusts and nodules employed the following enrichment mechanisms: (1) the metal ion complexed with the surface hydroxyl of Fe-Mn minerals to form hydroxyl complexes, which were connected by coordination bonds or stable inner-sphere complexes that exchanged protons on the mineral surfaces; (2) the charged surfaces of the minerals and metal cations formed outer-sphere complexes, which made up the electrostatic double layer, through electrostatic adsorption; and (3) the metal cations isomorphously exchanged the Mn and Fe ions of the mineral lattice structure.
基金financially supported by the National12th Five Year Plan Project(No.DY-125-13-R-05)Natural Sciences Foundation of China(No.40343019.40473024)+2 种基金project from the State Key Laboratory for Mineral Deposits Research in Nanjing University(No.20-15-07)the Project Supported by Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme(2011)the Fundamental Research Funds for Central Universities(No.121gjc05,091gpy09)
文摘The rare earth elements(REE) composition of the polymetallic crusts and nodules obtained from the South China Sea(SCS) were analyzed through inductively coupled plasma mass spectrometry.Results revealed great differences in the REE abundances(∑REE) of the SCS polymetallic crusts and nodules; the crusts show the highest ∑REE, whereas the nodules exhibit the lowest ∑REE. The similarity in their NASC-normalized patterns, the enriched light REE(LREE), the markedly positive Ce anomaly(δCe), and the non-or weakly positive Eu anomaly(δEu), suggest that the polymetallic crusts and nodules are of hydrogenetic origin. Moreover, the REE contents and their relevant parameters are quite different among the various layers of the crusts and nodules, which probably results from the different marginal sea environments and mineral assemblages of the samples. The growth profiles of the SCS polymetallic crusts and nodules reveal the tendency ∑REE and δCe to slightly increase from the outer to the inner layers, suggesting that the growth environments of these samples changed smoothly from an oxidizing to a relatively reducing environment; in addition, the crust ST1 may have experienced a regressive event(sea-level change) during its growth, although the REE composition of the seawater remained relatively stable. On the basis of the regional ∑REE distribution in the SCS crusts and nodules,the samples collected near the northern margin were influenced by terrigenous material more strongly compared with the other samples, and the REE contents are relatively low. Therefore, the special geotectonic environment is a significant factor influencing the abundance of elements, including REE and other trace elements. Compared with the oceanic seamount crusts and deep-sea nodules from other oceans,the SCS polymetallic crusts and nodules exhibit special REE compositions and shale-normalized patterns, implying that the samples are of marginal sea-type Fe-Mn sedimentary deposits, which are strongly affected by the epicontinental environment, and that they grew in a more oxidative seawater environment. This analysis indicates that the oxidized seawater environment and the special nano property of their Fe-Mn minerals enrich the REE adsorption.
基金The National Natural Science Foundation of China under contract No.40706028
文摘Kr and Xe nuclide abundance and isotopic ratios of the uppermost layer of Fe-Mn Crusts from the western and central Pacific Ocean have been determined. The results indicate that the Kr and Xe isotopic composi-tions, like that of He, Ne and Ar, can be classified into two types: low3He/4He type and high3He/4He type. The low3He/4He type crusts have low84Kr and132Xe abundance, while the high3He/4He type crusts have high84Kr and132Xe abundance. The82Kr/84Kr ratios of the low3He/4He type crusts are lower than that of the air, while the83Kr/84Kr and86Kr/84Kr ratios are higher than those of the air. The Kr isotopic ratios of the high-er3He/4He type crusts are quite similar to those of the air. The128Xe/132Xe,130Xe/132Xe and131Xe/132Xe ratios of the low3He/4He type sample are distinctly lower than those of the air, whereas the129Xe/132Xe,134Xe/132Xe and136Xe/132Xe ratios are higher than those of the air. The low3He/4He type samples have the diagnostic characteristics of the MORB, with excess129, 131, 132, 134, 136Xe relative to130Xe compared with the solar wind. The128Xe/132Xe,130Xe/132Xe and131Xe/132Xe ratios of the high3He/4He type samples are slightly higher than those of the air, and the129Xe/132Xe,134Xe/132Xe and136Xe/132Xe ratios are qiute similar to those of the air. The noble gases in the Fe-Mn crusts are derived from the lower mantle, and they are a mixture of lower mantle primitive component, radiogenic component and subduction recycled component. The helium isotopic ra-tios of the low mantle reservoir are predominantly controlled by primitive He (3He) and U and Th radiogenic decayed He (4He), but the isotopic ratios of the heavier noble gases, such as Ar, Kr and Xe, are controlled to different extent by recycling of subduction components. The difference of the noble isotopic compositions of the two type crusts is the result of the difference of the noble isotopic composition of the mantle source reservoir underneath the seamounts the crusts occurred, the noble gases of the high3He/4He type crusts are derived mainly from EM-type lower mantle reservoir, and the noble gases in the low3He/4He type crusts are derived mainly from HIMU-type lower mantle reservoir.
基金Project(No.49771049)supported by the National Natural Science Foundation of China
文摘X-ray diffraction and selective chemical dissolution methods were used to investigate the composition of Mn oxide minerals in Fe-Mn nodules of several main types of soils in China. The changes of relative intensity of X-ray diffraction patterns were studied both before and after chemically selective dissolution. It was found that lithiophorite was a common Mn oxide in all examined Fe-Mn nodules. Todorokite, however, was a predominant Mn oxide in Fe-Mn nodules in caf-aquic Vertisols of Linyi, Shandong Province. The Fe-Mn nodules of arp-udic Luvisols in Wuhan and Zaoyang, Hubei Province, contained birnessite and vernadite. Hollandite was found in Fe-Mn nodules of alt-udic Ferrisols of Yizhang, Hunan Province; arp-udic Luvisols of Zaoyang, Hubei Province; and cal-aquic Vertisols of Linyi, Shandong Province. The Fe-Mn nodules in alt-udic Ferrisols of Guiyang, Hunan Province, had a few coronadites. Mineralogy of Mn oxide minerals in soil Fe-Mn nodules was related to soil environment, soil types and quantities of relevant cations.
基金China Ocean Mineral Resources R&D Association(COMRA)Project under contract Nos DY135-C1-1-05,DY135-N1-1-06 and DY135-C1-1-02the Scientific Research Fund of the Second Institute of Oceanography,MNR under contract No.JT1304。
文摘Polymetallic nodules and cobalt (Co)-rich crusts are enriched in platinum-group elements (PGEs),especially platinum (Pt) and may be important sinks of PGEs.At present,little information is available on PGEs in polymetallic nodules,and their geochemical characteristics and the causes of PGEs enrichment are unclear.Here PGEs of polymetallic nodules from abyssal basin in the Marcus-Wake Seamount area of the Northwest Pacific Ocean are reported and compared with the published PGEs data of polymetallic nodules and Co-rich crusts in the Pacific.The total PGEs (ΣPGE) content of polymetallic nodules in study area is 258×10^–9) in average,markedly higher than that of Clarion-Clipperton Zone (CCZ) nodules (ΣPGE=127×10^–9) and lower than that of Co-rich crusts in the Marcus-Wake Seamount (ΣPGE=653×10^–9),similar to that of Co-rich crusts in the South China Sea(ΣPGE=252×10^~–9).The CI chondrite-normalized PGEs patterns in different regions of polymetallic nodules and cobalt-rich crusts are highly consistent,with all being characterized by positive Pt and negative Pd anomalies These results,together with those of previous studies,indicate that PGEs in polymetallic nodules and Co-rich crusts are mainly derived directly from seawater.Pt contents of polymetallic nodules from the study area are negatively correlated with water depth,and Pt/ΣPGE ratios in nodules there are also lower than those of the Corich crusts in the adjacent area,indicating that sedimentary water depth and oxygen fugacity of ambient seawater are the possible important controlling factors for Pt accumulation in crusts and nodules.
基金This work was sponsored by the International Ocean Area Research & Development Tenth Five-Year Plan Programme (Grant No. DY105-04-01-9).
文摘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
基金National Natural Science Foundation of China(40972079,41172015 and 41030853)the State Key Research Develop-ment Program of China(2007CB411703)+1 种基金the Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology,Ministry of Landand Resources(MRE200912)the Fund of Education Department of Hebei Province(2009443,2010148)
文摘Polymetallic nodules and crusts are two of the most important mineral deposits in the ocean. They are rich in rare earth elements (REEs), iron, manganese, copper, cobalt, nickel, and other useful metals. This paper discussed the analysis of 25 nodule and crust samples collected from the South China Sea, the Pacific, Atlantic, and Indian Oceans. The samples were analyzed for REE content by ICP-MS/AES. The average REE concentration was found to be 1096.96×10^-6 in the nodules and 1623.88×10^-6 in the crusts. Both of these values are much higher than those recorded in Earth's dry-land crust and sedimentary rocks. This REE enrichment is mainly controlled by the absorption of ferromanganese oxides and clay minerals in the nodules and crusts and the high levels of REEs in seawater and sediments. High cerium enrichment in the nodules and crusts may lead to more effective exploitation of REEs in the future.
基金the China Oceanic Mineral Resources R & D Association (COMRA) (Grant No. DY105-01-04-02)the National Natural Science Foundation of China (Grant No. 40376016)
文摘The noble gas nuclide abundances and isotopic ratios of the upmost layer of Fe-Mn crusts from the western and central Pacific Ocean have been determined. The results indicate that the He and Ar nuclide abundances and isotopic ratios can be classified into two types: low 3He/4He type and high 3He/4He type. The low 3He/4He type is characterized by high 4He abundances of 191×10?9 cm3·STP·g?1 on average, with variable 4He, 20Ne and 40Ar abundances in the range (42.8?421)×10?9 cm3·STP·g?1, (5.40?141)×10?9 cm3·STP·g?1, and (773?10976)×10?9 cm3·STP·g?1, respectively. The high 3He/4He samples are characterized by low 4He abundances of 11.7×10?9 cm3·STP·g?1 on average, with 4He, 20Ne and 40Ar abundances in the range of (7.57?17.4)×10?9 cm3·STP·g?1, (10.4?25.5)×10?1 cm3·STP·g?1 and (5354?9050)×10?9 cm3·STP·g?1, respectively. The low 3He/4He samples have 3He/4He ratios (with R/RA ratios of 2.04?2.92) which are lower than those of MORB (R/R A=8±1) and 40Ar/36Ar ratios (447?543) which are higher than those of air (295.5). The high 3He/4He samples have 3He/4He ratios (with R/R A ratios of 10.4?12.0) slightly higher than those of MORB (R/R A=8±1) and 40Ar/36Ar ratios (293?299) very similar to those of air (295.5). The Ne isotopic ratios (20Ne/22Ne and 21Ne/22Ne ratios of 10.3?10.9 and 0.02774?0.03039, respectively) and the 38Ar/36Ar ratios (0.1886?0.1963) have narrow ranges which are very similar to those of air (the 20Ne/22Ne, 21Ne/22Ne, 38Ar/36Ar ratios of 9.80, 0.029 and 0.187, respectively), and cannot be differentiated into different groups. The noble gas nuclide abundances and isotopic ratios, together with their regional variability, suggest that the noble gases in the Fe-Mn crusts originate primarily from the lower mantle. The low 3He/4He type and high 3He/4He type samples have noble gas characteristics similar to those of HIMU (High U/Pb Mantle)-and EM (Enriched Mantle)-type mantle material, respectively. The low 3He/4He type samples with HIMU-type noble gas isotopic ratios occur in the Magellan Seamounts, Marcus-Wake Seamounts, Marshall Island Chain and the Mid-Pacific Seamounts whereas the high 3He/4He type samples with EM-type noble gas isotopic ratios occur in the Line Island Chain. This difference in noble gas characteristics of these crust types implies that the Magellan Seamounts, Marcus-Wake Seamounts, Marshall Island Chain, and the Mid-Pacific Seamounts originated from HIMU-type lower mantle material whereas the Line Island Chain originated from EM-type lower mantle material. This finding is consistent with variations in the Pb-isotope and trace element signatures in the seamount lavas. Differences in the mantle source may therefore be responsible for variations in the noble gas abundances and isotopic ratios in the Fe-Mn crusts. Mantle degassing appears to be the principal factor controlling noble gas isotopic abundances in Fe-Mn crusts. Decay of radioactive isotopes has a negligible influence on the nuclide abundances and isotopic ratios of noble gases in these crusts on the timescale of their formation.
基金This work was funded by the National Natural Foundation of China(41701266,41977288 and U1612442)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB40020400)+1 种基金the Frontier Science Research Programme(QYZDB-SSW-DQC046)the West Light Foundation of the Chinese Academy of Sciences,and the Science and Technology Foundation of Guizhou Province([2018]1177).
文摘Cadmium (Cd) pollution in agricultural soils has become a severe threat to food security and human health in recent years. Stable Cd isotopes are a potentially powerful tool for identifying the sources of Cd in soils. However, many Earth surface processes, including adsorption, leaching, and biogeochemical cycles in plants, may generate Cd isotope fractionation, which can complicate the potential application of Cd isotopes in tracing the sources of Cd pollution in soils. In this work, the Cd isotope compositions of typical Fe-Mn nodules (FMNs) and surrounding soils in two different soil profiles are investigated. Our results show that the FMNs in lower layers (i.e., C and W horizons) are isotopically lighter than the surrounding soils by –0.114‰ to –0.156‰ (Δ114/110CdFMN-soil). We interpret this fractionation as the result of preferential adsorption of isotopically light Cd onto the surface of goethite. In the upper layers (i.e., P and A horizons), the Δ114/110CdFMN-soil values are more negative in the P horizon (–0.213‰ to –0.388‰) but more positive in the A horizon (0.061‰ to 0.204‰). We interpret these fractionations as the result of natural biogeochemical processes (i.e., leaching and biological cycling) during soil development. Soil leaching preferentially releases isotopically heavy Cd into the underlying soil (i.e., P horizon), shifting the topsoil towards lower δ114/110Cd values but the underlying soils towards higher δ114/110Cd values. Moreover, biological cycling contributes isotopically heavy Cd to the topsoil, probably shifting the topsoil towards higher δ114/110Cd values. Our study demonstrates that the formation of Fe oxyhydroxides, leaching, and biological cycling can considerably modify the soil Cd isotope signature, highlighting the need to consider natural biogeochemical processes when using Cd isotopes to trace heavy metal pollution in soils.