中太平洋和中国南海富钴结壳稀土元素地球化学

对中太平洋海山和中国南沙海盆富钴结壳中稀土元素的含量、分布特征、配分模式分析结果表明:富钴结壳中稀土元素含量非常高,总量为1 380×10-6~2 360×10-6,约为正常深海沉积物和海水中稀土元素含量的10~100倍,与大陆地壳丰度相比Ce最为富集;中太平洋海山区和中国南沙海盆富钴结壳中的稀土元素配分模式与其他海域基本相同,属轻稀土元素富集、重稀土元素亏损型;Ce元素含量和轻重稀土元素的比值沿生长方向逐渐降低,底层比顶层高出近一倍;不同海域富钴结壳中稀土元素的含量变化较大,夏威夷群岛富钴结壳中的稀土元素总量最高,中太平洋海山区中等,中国南沙海盆偏低。     

麦哲伦海山群富钴结壳元素地球化学特征及赋存状态

为探究大洋富钴结壳的元素地球化学特征和赋存状态,以西太平洋麦哲伦海山群5个富钴结壳样品为研究对象,通过X射线衍射法、等离子体发射光谱法、等离子体质谱法及相态分析手段,分析了富钴结壳的矿物组成、主量元素和稀土元素含量。结果表明,富钴结壳样品主要结晶矿物为水羟锰矿,次要矿物包括石英、斜长石和钾长石,同时含有大量非晶态铁氧/氢氧化物。富钴结壳样品中Mn和Fe含量最高, Mn为16.87%～26.55%, Fe为14.34%～18.08%。富钴结壳明显富集稀土元素,其稀土总量为1 287～2 000μg/g,Ce含量为632～946μg/g,约占稀土总量的50%;轻稀土含量为1 037～1 604μg/g,重稀土含量为249～395μg/g,轻稀土元素明显高于重稀土元素。稀土元素配分模式呈现Ce正异常而Eu无异常,具有Ce富集特征。麦哲伦海山群富钴结壳是水成沉积成因,基本没有受到海底热液活动和成岩作用的影响。元素赋存状态与其矿物相密切相关, Na、K、Ca、Mg和Sr主要赋存于碳酸盐相, Mn、Ba、Co和Ni主要赋存于锰氧化物相, Fe、Al、P、Ti、Cu、Pb、V、Zn、Zr和REE主要...     

西太平洋采薇海山和徐福海山富钴结壳稀土元素地球化学特征及来源

利用X射线衍射法、等离子体发射光谱法和等离子体质谱法分析了西太平洋采薇海山和徐福海山富钴结壳矿物相组成以及常微量元素含量,探讨稀土元素地球化学特征和物质来源。研究表明,富钴结壳样品主要结晶矿物为水羟锰矿,次要矿物包括石英、斜长石、钾长石和碳氟磷灰石,同时含有大量非晶态铁氧/氢氧化物。富钴结壳的Mn和Fe含量最高,Mn含量为16.20%～26.62%,Fe含量为8.56%～18.19%,老壳层（IV和V）发生了磷酸盐化作用。富钴结壳的稀土元素明显富集,轻稀土元素明显高于重稀土元素,稀土总量为1 842～2 854μg/g,其中,Ce约占50%。老壳层中稀土元素含量明显高于新壳层,这可能与老壳层发生磷酸盐化作用有关。稀土元素配分模式呈现Ce正异常、Eu无异常,具有明显Ce富集特征。富钴结壳的稀土元素与Ce、Y、CaO、P₂O₅、Ba和Sr具有正相关性关系,与Fe、Al₂O₃、Na₂O、K₂O、MgO、TiO₂、Pb和V具有负相关性关系,与...     

太平洋徐福海山富钴结壳稀土元素和铂族元素赋存状态研究

利用等离子体发射光谱法、等离子体质谱法以及相态分析手段,对太平洋徐福海山富钴结壳稀土和铂族元素地球化学特征、赋存状态及富集机制进行研究。结果表明,富钴结壳稀土和铂族元素明显富集,其稀土总量为1 842～2 854 μg/g,铂族总量为144～1 180 ng/g,老壳层中稀土和铂族元素含量明显高于新壳层,这可能与老壳层发生磷酸盐化作用有关。轻稀土元素含量明显高于重稀土元素含量,呈现Ce正异常而Eu无异常,具有明显Ce富集特征。铂族元素之间发生了明显分异作用,PPGE含量明显高于IPGE,表现出明显Pt正异常而Pd负异常,具有明显Pt富集而Pd亏损特征。稀土元素赋存状态显示,新壳层中稀土元素主要赋存于铁氧化物相,其富集比例为65.40%～70.05%,老壳层中稀土元素主要赋存于残渣态,富集比例为62.27%～65.77%,这可能与残渣态中磷酸盐有关。铂族元素赋存状态显示,新壳层和老壳层中铂族元素都主要赋存于铁氧化物相,其富集比例为63.66%～69.51%,残渣态(29.20%～34.68%)对铂族元素也有一定的富集能力。富钴结壳稀土和铂族元素的富集推测为铁氧化物胶体粒子的吸附作用,受海水氧化性环境影响,可溶性Ce3+和Pt2+分别被氧化成不溶性Ce4+和Pt4+,沉淀被吸附到铁氧化物相中,从而造成富钴结壳稀土和铂族元素的富集。     

九州-帕劳海脊南段铁锰结壳物质组成特征及成因机制

铁锰结壳(又称富钴结壳、多金属结壳)富含Co、Cu、Mn、Ni、Ti、V、REE、Y和Zn等人类日常生活和高新技术产业亟需的关键金属,是一种重要的战略性矿产资源。本文对九州-帕劳海脊南段水深1 900～2 600 m处获得的9个站位铁锰结壳样品进行了矿物学和地球化学研究,分析了铁锰结壳的矿物组成、主微量元素和稀土元素含量,并进一步探讨了铁锰结壳的成因类型。结果表明,研究区铁锰结壳的矿物组成以水羟锰矿为主,同时含有大量非晶态铁氧/氢氧化物;Mn、Fe、Co、Ni、Cu平均含量分别为16.15%、15.38%、0.32%、0.33%、0.10%;CaO/P₂O₅均值为5.93,表明九州-帕劳海脊南段铁锰结壳样品均未发生磷酸盐化作用;铁锰结壳明显富集稀土元素(含Y,REYs),平均含量为1 194μg/g,轻稀土显著富集,稀土元素经后太古代澳大利亚页岩(PAAS)标准化后配分模式整体相对平坦,呈现Ce正异常而Eu无异常,与海水呈现镜像关系,说明铁锰结壳稀土元素主要来源于海水。铁锰结壳的矿物组成和元素判别图均表明九州-帕劳海脊南段铁锰结壳属于水成型,...     

西太平洋Lamont海山中新世以来富钴结壳成矿环境的演化

分析了西太平洋Lamont海山12个站位33个富钴结壳样品的主元素和稀土元素,结果表明,该海山富钴结壳成因类型属于水成成因,并且在形成过程中基本未受到磷酸盐化作用的影响。Lamont海山的一个富钴结壳样品剖面的电子探针数据显示,该海山富钴结壳的成矿环境在新第三纪以来至少存在2个演化阶段:第1阶段,23~15 Ma,富钴结壳中Mn相对富集,成矿环境以富氧贫硅为特征;第2阶段,15~0 Ma,富钴结壳中Fe相对富集,成矿环境以贫氧富硅为特征。成矿环境的氧化能力总体上呈现下降的趋势。联系新生代世界大洋,尤其是西太平洋的地质演化背景,认为引起成矿环境演变的原因主要是西太平洋大洋板块的WNW向漂移和新第三纪以来全球水道开合,造成了Lamont海山所处海区最低含氧带逐渐减薄。     

中太平洋富钴结壳Co元素地球化学特征

对在中太平洋研究区5座海山调查时获取的38个富钴结壳样品中主要金属元素的含量进行了化学分析,探讨了不同海山富钴结壳中Co元素含量的变化规律及结壳中元素间的相关关系,结果表明:(1)5座海山富钴结壳中的各主要金属元素含量相近,38个富钴结壳样品中Co元素的平均含量为0.67%,具有一定的开发前景。(2)不同海山富钴结壳中Co元素含量有一定变化,其变化与富钴结壳的类型、海水水深、地形地貌以及成矿作用等有密切的关系。Co元素在板状结壳中的含量为最高,在钴结核中的含量次之,而在砾状结壳中的含量为最低;富钴结壳中Co元素含量与海水水深呈负相关,浅水区富钴结壳中Co元素的含量明显高于深水区;海山地形地貌对Co元素的含量及富钴结壳的发育有一定影响,海山的椭圆状分支、支脉及边缘部分,Co元素的含量相对较高,富钴结壳发育得较好;Co元素富集成矿作用还主要受锰、铁水成成矿作用的控制。(3)富钴结壳中金属元素之间存在不同程度的相关性。Mn元素分别与Co、Ni、Cu、Zn、Mg、Na、Ba、Ti等元素呈强烈的正相关,而分别与Al、Si、Ca、P、Fe、Sr等元素呈负相关;Co元素分别与Cu、Al、P、Ca等元素呈负相关;Ca元素与P元素呈强烈正相关。     

冲绳海槽中部热液活动区岩芯沉积物稀土元素地球化学特征

针对冲绳海槽中部热液活动区附近的沉积物岩芯(H9),利用碱熔法和等离子体发射光谱法对其稀土元素组成进行了分析。结果表明,在岩芯中稀土元素含量在75—80cm段发生转折,75cm以上岩芯段沉积物中稀土元素总量相对较高,而且稀土元素总量,尤其是轻稀土元素总量,与(Fe+Mn)/Al相关性较好。该段沉积物中稀土元素页岩标准化配分模式呈右倾或近似水平,突出特征表现为轻稀土间的明显分异和Eu的相对富集,与热液源稀土元素组成极为相似。与热液流体和热液硫化物相比,分异程度和Eu正异常程度都较低,同时,具有明显的负Ce异常,与海水的稀土配分模式相类似。由此可见,热液活动对该岩芯上段沉积物中稀土元素组成具有重要影响,一方面表现为热液源物质的直接输入,另一方面表现为热液颗粒物质沉积过程中对海水中稀土元素的清扫。     

西太平洋Kocebu海山铁锰结壳稀土元素地球化学特征

西太平洋麦哲伦海山区是全球重要的铁锰结壳资源分布区,具有丰富的稀土元素资源潜力。本文对采自麦哲伦海山区Kocebu海山的11个铁锰结壳表层样(<1 mm)进行稀土元素地球化学研究,探讨其含量特征、成因和影响稀土元素富集的环境因素。结果表明:Kocebu海山铁锰结壳表层样品ΣREY(Rare earth elements and yttrium)平均含量为1366 mg/kg,低于前人在麦哲伦海山区其他海山以及邻近的马尔库斯–威克海山区的分析结果;样品轻稀土富集和Ce正异常(平均值为1.45)特征以及稀土元素成因图解、配分曲线和分配系数曲线等均表明该海山结壳属于水成成因;海水中稀土元素含量和溶解氧含量是控制结壳生长的关键环境参数,二者在Kocebu海山所在海区的浅水环境中含量较低;结壳ΣREY含量偏低与采样点水深较浅导致的海水稀土元素含量和溶解氧含量较低密切相关,受碎屑矿物的稀释作用影响较小。在开展铁锰结壳地球化学特征研究和资源勘探评价时应充分考虑采样水深的分布范围,局部水深样品的分析结果可能导致研究结果出现较大偏差。     

磷酸盐化作用对富钴结壳中稀土元素的影响

稀土(REY)是一组有效示踪物质源区和地质过程的元素,本研究利用X荧光光谱法(XRF)和电感耦合等离子光谱仪(ICP-MS)分析了马尔库斯-威克海山和中太平洋海山富钴结壳的主要元素和稀土元素,结合前人研究成果对比了磷酸盐化及未磷酸盐化富钴结壳的稀土特征。结果显示:磷(P)含量低的结壳具有相对低的稀土总量(∑REY),北美页岩标准化后显示铈(Ce)正异常和钇(Y)负异常;磷酸盐化后的结壳具有相对高的∑REY,并表现出Ce正异常和显著Y正异常。磷酸盐化结壳中应存在"富稀土磷酸盐"组分,特别是对Y具有重要贡献。将磷酸盐化结壳视为磷酸盐组分和结壳组分的混合,模拟结果显示富稀土磷酸盐组分具有海山磷块岩的稀土配分模式,但是其∑REY达到普通磷块岩的10倍或以上。考虑到海洋中富钙沉积物丰富,大量PO_4~(3-)不同程度地交代碳酸盐等钙质物质,容易形成贫稀土磷酸盐。而伴随结壳缓慢的成矿过程,部分磷酸盐的形成未受到碳酸盐的影响,容易形成富稀土磷酸盐。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

A Review of Some Environmental Issues Affecting Marine Mining

This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested.     

Increased Particle Fluxes at the INDEX Site Attributable to Simulated Benthic Disturbance

Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

Determination of In Situ Sediment Shear Strength from Advanced Piston Corer Pullout Forces

The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments.     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects

The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics.