GEOCHEMICAL CHARACTERISTICS OF Fe-Mn NODULES AND CRUSTS FROM THE MARIANA RIDGE AND THE WEST PHILIPPINE BASIN

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

The effect of Fe-Mn minerals and seawater interface and enrich-ment mechanism of ore-forming elements of polymetallic crusts and nodules from the South China Sea

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.

Rare Earth Elements Composition and Constraint on the Genesis of the Polymetallic Crusts and Nodules in the South China Sea

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.

Kr and Xe isotopic compositions of Fe-Mn crusts from the western and central Pacific Ocean and implications for their genesis

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.

Mineralogy of Manganese Oxide Minerals in Iron Manganese Nodules of Several Main Soils in China

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.

Geochemical characteristics of platinum-group elements in polymetallic nodules from the Northwest Pacific Ocean

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.

机器学习:海底矿产资源智能勘探的新途径

海底蕴藏着丰富的关键矿产资源,是当前研究的热点,也是未来产业新领域。随着海洋探测技术的不断进步,海底矿产勘探的数据量和数据维数急剧增加,给数据处理与解释带来了巨大困难和挑战。面对海量数据,传统的数据解释与分析方法暴露出许多问题。机器学习以其强大的自学能力,为无法解决或难以解决的问题提供了一系列智能分析决策方案,提高了数据分析的效率,是海底矿产资源智能勘探的新途径。近年来,机器学习在地球科学领域获得了广泛的关注和研究。为此,围绕机器学习技术应用于海底资源勘探技术,本文首先简要介绍了机器学习中经典的模型算法,然后详细阐述了机器学习在海底能源矿产和金属矿产两个方面的应用现状,最后总结了机器学习在海底矿产智能勘探领域的应用前景,指出了现有研究中存在的问题,提出了解决方案和未来的发展方向。

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

Enrichment of REEs in polymetallic nodules and crusts and its potential for exploitation

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.

海洋有色金属矿产地球物理勘探进展

随着对海洋矿物资源的勘探研究,人们意识到多金属结核、富钴结壳和多金属硫化物等是具有战略意义的海洋有色金属矿产。近年来,随着地球物理勘探技术的发展,勘探深度逐渐从浅海过渡到深海,加深了人们对深部有色金属资源的认识,深海有色金属资源逐步成为世界各国关注的热点。近十年来,我国在深海矿产资源领域的研究取得了一系列的重要进展。首先,本文主要介绍国内外海洋有色金属矿产的勘探现状,并且在原理基础、正反演技术方法等方面回顾了适用于深海环境的地球物理勘探方法的发展。然后,结合我国在太平洋的多金属结核勘探区、富钴结壳勘探区和在西南印度洋中脊的多金属硫化物矿勘探区的研究进展,归纳了海洋有色金属矿产的地球物理勘探方法及实例分析。

碲的地球化学与碲资源研究现状

碲是战略性关键矿产。碲独特的地球化学性质,使碲元素及其同位素有望为多种地球化学和宇宙化学过程提供重要信息。本文综述了碲的物理和化学性质、碲矿物学、各储库碲含量、陆地和海洋碲资源以及碲同位素地球化学等方面的研究现状。地壳中碲丰度很低,但碲矿物数量多,主要为自然碲、碲化物、碲硫(硒)化物、碲氧化物和含氧盐。碲在大洋结核和结壳、陆地富碲矿床及富有机质沉积物中含量较高。浅成低温热液矿床、造山型金矿、火山成因块状硫化物矿床等热液成因矿床和岩浆铜镍铂族硫化物矿床是重要的陆地富碲矿床类型。大洋结核和结壳中的碲达到了碲矿床的富集程度,且蕴含的碲资源量远超过陆地碲资源量。与球粒陨石相比,地球物质也存在显著的碲同位素分馏,碲同位素地球化学在陆地和海洋碲资源研究中已得到初步应用。

He,Ne and Ar isotopic composition of Fe-Mn crusts from the western and central Pacific Ocean and implications for their genesis

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.

Cadmium isotope compositions of Fe-Mn nodules and surrounding soils: Implications for tracing Cd sources

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.

中国海域固体矿产资源分布及其区划——砂矿资源和铁锰(微)结核—结壳

综述和研究了我国海域砂矿资源和(微)结核—结壳的分布及其区划。我国的滨海砂矿广泛分布于渤海、黄海、东海和南海,但各省区的砂矿资源分布不同。近年来在我国海域新发现和圈定了多处砂矿品位异常区和矿物高含量区,可分为3个成矿带和24个成矿远景区,资源储量可观。在黄海、东海仅分布铁锰结核,没有发现铁锰结壳,但它们的金属元素含量低,没有潜在资源意义。南海东北陆坡、中央海盆西部和中部是(微)结核、结壳分布较多的区域。南海东北陆坡、海山及其周缘坡脚处的(微)结核、结壳其稀土元素含量较高,可能具有一定的潜在经济价值,今后调查中应引起重视。

中太平洋海山多金属结壳的成矿特征

根据我国大洋多金属结壳的调查资料并结合其他相关的研究结果 ,对中太平洋海山区多金属结壳的类型、产状、成分、结构、分布等成矿特征进行了初步的研究 .结果表明 ,中太平洋海山区富钴结壳广泛发育 ,但成矿特征较大地受地形、水深、基岩类型等成矿环境因素的影响与制约 .

太平洋多金属结核和富钴结壳稀土元素地球化学对比及其地质意义

多金属结核和富钴结壳是大洋两类典型的铁锰产物。为探讨不同海区多金属结核和富钴结壳之间稀土元素特点及其揭示的地质意义,利用近年中国在太平洋获取的样品进行对比,采用ICP-AES对稀土元素测试。结果表明,结壳具有正Ce异常明显、LREE富集、∑REE高的特点,而结核表现为HREE相对富集、∑REE相对较低,因成因类型不同,Ce异常或表现为正异常、负异常或异常不明显。结核形成后受到成岩作用的影响,而结壳则为水成作用形成;结核和结壳中REE的存在形式比较复杂,不同海区各不相同,中太平洋东部产出的结壳和位于东太平洋的结核中REE可能主要赋存于铁矿物相,而西太平洋结壳REE可能主要赋存于锰矿物相;结核和结壳REE可能分别来自海水和海山蚀变玄武岩,热液作用影响有限。

太平洋海山富钴结壳铂族元素(PGE)和Os同位素地球化学及其成因意义

本文分析了中西太平洋海山富钴结壳及其各主要层圈(外层、疏松层、亮煤层)和玄武岩基岩的铂族元素(PGE)和Au 含量以及 Os 同位素组成,发现富钴结壳中 PGE 和 Au 含量均较高,且变化很大,∑PGE 为(70.09～629.26)×10^(-9),平均289.48×10^(-9),Au 为(0.60～26900)×10^(-9).具三层结构的富钴结壳中,疏松层(∑PGE=(339.37～545.82)×10^(-9))和亮煤层(∑PGE=(280.09～629.26)×10^(-9))的∑PGE 明显高于外层((70.09～133.27)×10^(-9).单层结壳的∑PGE 为(83.94～479.75)×10^(-9),Au 含量普遍高于具三层结构者.结壳的∑PGE 和 Au 含量远高于太平洋多金属结核(分别为(101.57～155.83)×10^(-9)和(1～4)×10^(-9)。沉积深度和海水氧逸度的不同是导致结壳和结核中 PGE 含量明显差异的主导因素。富钴结壳∑PGE 和 Pt 与 Mn(%)之间呈明显的正相关关系,而与 Fe(%)具负相关性,与多金属结核正好相反,显示结壳中的 PGE主要赋存在水羟锰矿(δ-MnO_2)等锰矿物相中,与针铁矿(FeOOH·nH_2O)等铁矿物相关系不大,而结核中的 PGE 主要赋存在铁矿物相中。PGE 球粒陨石标准化曲线和各项参数显示富钴结壳的 PGE 和 Au 主要来自海底玄武岩的蚀变释放,部分来自铁陨石微粒等地外物质,而与海底热水活动无关。计算显示西太平洋结壳距今42.5Ma 左右开始生长,生长过程中分别在8.0Ma 和21.8Ma 处出现间断,相应形成外层、疏松层和亮煤层,其各自沉积速率为2.64mm/Ma,1.45mm/Ma 和1.06mm/Ma,相应海水的^(187)Os/^(188)Os 分别为0.948～0.953,0.599～0.673和0.425～0.536,显示外层含有较多的大陆风化尘,而疏松层和亮煤层的沉积物主要来自海底洋壳蚀变和陨石碎屑或宇宙尘等地外物质。

太平洋铁锰结核与富Co结壳的矿物地球化学比较研究

本文对采自东太平洋CC区的2块不同类型的铁锰结核及中太平洋麦哲伦海山的1块富Co结壳，采用XRD和IcP—MS（AES）等分析研究方法，进行了矿物地球化学的比较研究。结果表明：铁锰结核主要由水羟锰矿及钡镁锰矿组成，富Co结壳主要以水羟锰矿为主。与2块铁锰结核相比，富Co结壳总体上Cu、Al、Na含量较低而Co含量较高；两块不同类型的结核相比较，水成型铁锰结核的P、Ti含量较高，而成岩型铁锰结核的Cu、Ni含量较高。3块样品的稀土元素含量均较高，为（521．8～1424．15）×10^-6。REE分布型式总体呈平缓型，（La／Yb）20为0．72～1.01，并具程度不同的Ce、Eu正异常。经估算，富Co结壳的生长速率为1．92～4．24mm／Ma，水成型铁锰结核的生长速率为1．31～14．29mm／Ma，成岩型铁锰结核的生长速率为¨．24~76．32mm／Ma。并根据铁锰结核的化学成分变化推测了其生长环境的变化。

东太平洋CC区多金属结核铂族元素(PGE)地球化学及其意义

文章采用火试金分离富集法和等离子发射光谱(ICP_MS)测定了东太平洋CC区多金属结核中PGE和Au元素的含量,结果显示:结核中PGE相对于洋壳明显富集,尤其是Pt含量较高,wPt平均值为100.90×10-9。各种类型的多金属结核PGE和Au的球粒陨石配分曲线及有关参数非常一致,均表现为Pt正异常和Pd负异常,显示其中PGE和Au具有相似的来源。多金属结核与海底海山富钴结壳PGE配分模式及特征元素比值对比表明,两者PGE可能具有相同的来源,可能主要来源于海底玄武岩的水岩反应,部分来源于铁陨石,而并非主要来自海底热液及正常海水。

南海铁锰结核(壳)的稀土元素地球化学

于1987年5—6月间,中、西德在南海进行地球科学调查,获得5个铁锰结壳、6个铁锰结核样品。本文在利用X荧光法测定15个稀土元素的基础上,对南海铁锰结核(壳)的稀土丰度、配分模式与伴生元素的关系以及稀土的来源作了较为详细的探讨。研究表明,南海铁锰结核(壳)的平均丰度为1625×10^(-6),铁锰结核为2167×10^(-6),分别要比太平洋结核高1—2倍,比太平洋北部沉积物高3—4倍,比南海沉积物高10—20倍;结核和结壳的稀土经球粒陨石标准化后的配分模式基本相同,Ce正异常,Eu亏损不明显;与伴生元素、沉积物及岩石稀土对比研究表明,结核(壳)中稀土主要来自南海中酸性岩类风化、淋漓后缓慢沉积。