中印度洋海盆富稀土沉积地球化学特征及富集机制研究

本文对中印度洋海盆深海富稀土沉积区两根柱样GC02和GC06开展了沉积物涂片观察,X-射线衍射分析,主量、微量和稀土元素分析,以及单矿物原位微区地球化学分析等,探讨了其地球化学特征、物质来源及稀土元素（REY）的富集机制。结果表明,GC02柱状沉积物类型为钙质黏土和沸石黏土,GC06柱状沉积物类型为钙质黏土、含沸石黏土和沸石黏土。稀土元素主要在含沸石黏土和沸石黏土中富集。北美页岩标准化（NASC）配分模式指示沉积物的REY主要来源于海水,矿物学和地球化学等特征表明该地区沉积物陆源组分可能主要源于澳大利亚的风尘物质。元素相关性和CaO/P₂O₅比值等指示了深海富稀土沉积中REY的主要赋存矿物为生物磷灰石（鱼牙/骨等）,其次为铁锰微结核。本文总结和探讨了深海富稀土沉积的形成机制,完善了深海富稀土沉积形成过程的概念模型。     

太平洋东部CC48孔沉积物稀土元素地球化学研究

研究样品于１９８８年采自太平洋东部ＣＣ４８孔。通过对沉积物稀土元素地球化学特征的分析发现：（１）各种类型深海沉积物的稀土含量有所差别，以稀土元素总量而论，深海粘土＞硅质软泥＞硅钙质软泥＞钙质软泥；沉积物中的自生矿物、硅质生物成因的非晶质ＳｉＯ２及碎屑矿物对稀土元素起富集作用，而生物ＣａＣＯ３则起分散作用。（２）稀土元素含量随深度发生变化。为地层划分提供了依据，应用元素地层学方法将岩芯分成５个层段。     

东太平洋CC区沉积物稀土元素特征及物源

对东太平洋CC区中西部33站表层沉积物进行了稀土元素(REE,包括Y)地球化学研究。结果表明,REE在沸石粘土中最富集,在硅质沉积物中含量明显偏低;所有沉积物样品中REE都存在Ce负异常和Eu正异常的轻稀土(LREE)亏损特征,表现为典型受到海水来源物质影响的REE配分模式;硅质粘土中Ce亏损程度、Eu正异常和REE富集程度都比硅质软泥更明显。与东区相比,西区沉积物中LREE、HREE(重稀土和钇元素)和∑REE(稀土元素总量)普遍偏高,LREE与HREE分异更明显,HREE相对更富集,LREE和Ce亏损更显著。研究区表层沉积物中REE主要来自海洋自生物质,同时受到陆源物质、海底火山物质的影响。     

东太平洋CC区西区表层沉积物黏土矿物和地球化学特征

本文以太平洋CC区西区12个表层沉积物样品作为研究对象,对其粒度、化学组分和矿物成分进行分析,讨论其沉积环境和物质来源。研究区地处深海,主要以深海黏土和硅钙质黏土为主,含有少量的硅质黏土、黏土质硅质软泥和黏土质钙质软泥。黏土矿物成分主要是蒙皂石和伊利石,含有部分的高岭石和绿泥石。黏土矿物组成表明,区内沉积物主要是陆源,由高空气流携带而来,南极底流和热液活动对其物源的来源有一定影响。沉积物地球化学特征也表明,物源以陆源为主,稀土元素分布曲线和北太平洋表层海水稀土曲线类似,且表现出强的Ce亏损,表明生物活动导致的生物沉降对表层沉积物也有一定的影响。     

庙岛群岛西部海域表层沉积物常量和稀土元素的分布特征及其物源指示意义

通过对庙岛群岛西部海域表层沉积物常量、稀土元素的系统研究,探讨了表层沉积物元素地球化学特征、控制因素及其物质来源。结果表明,庙岛群岛西部海域表层沉积物常量元素以SiO₂和A1₂O₃为主,SiO₂含量随着沉积物粒径变粗逐渐增大,Al₂O₃含量随着沉积物粒径变细逐渐增大。稀土元素(Rare Earth Element,REE)呈现轻稀土元素(Light Rare Earth Element,LREE)富集、重稀土元素(Heavy Rare Earth Element,HREE)平坦以及中等程度的Eu负异常等特征,轻重稀土分异明显,稀土元素球粒陨石配分曲线与黄河沉积物类似。通过因子分析和相关性分析发现研究区沉积物的元素含量主要取决于陆源碎屑,海洋生物沉积和化学作用对沉积物元素含量有一定的影响,元素含量基本服从粒度控制规律。物源判别结果显示,庙岛群岛西部海域沉积物主要来源于黄河物质和辽河物质,并且从南到北辽河物质的混合比例逐渐升高,黄河物质的混合比例逐渐降低。     

中印度洋洋盆GC11岩心富稀土深海沉积的元素地球化学特征

对中印度洋洋盆的沉积GC11岩心开展了主量元素、微量元素和稀土元素分析研究，根据主微量元素相关性特征、稀土元素富集程度以及澳大利亚后太古代平均页岩归一化模式特征，初步探讨了GC11岩心的沉积地球化学特征，以及影响稀土元素富集的可能因素。研究表明，GC11岩心稀土元素总量在400.64×10?6～742.74×10?6，平均值为658.41×10?6，略低于邻近海域的GC02岩心，与沃顿海盆DSDP213岩心中含沸石型深海粘土层位中的稀土元素含量相当。δCe负异常明显，(La/Yb)_N为0.42，显示重稀土相对富集的特点。稀土元素与P₂O₅呈显著正相关性，CaO/P₂O₅的平均值为2.3，表明生物钙磷灰石可能是稀土元素的主要载体矿物，而铁锰水合物可能对富集稀土元素有一定的促进作用，但影响不大；GC11岩心中δCe负异常程度远低于GC02岩心，略低于DSDP213岩心，中稀土富集特征与GC02和DSDP213岩心基本一致。不同程度陆源物质的混入可能是导致以上不同岩心中稀土元素富集程度和分馏特征的主要原因。     

太平洋深海富稀土沉积物的分类及成因

深海富稀土沉积物广泛分布在西太平洋、东太平洋、东南太平洋、印度洋等地区。本研究对东太平洋克拉里昂-克里珀顿断裂带(Clarion-Clipperton Fracture Zone,简称CC区)的两个站位富稀土沉积物的矿物学与地球化学特征进行了分析,并收集了太平洋92个站位深海富稀土沉积物元素地球化学数据,依据地球化学特征,结合矿物组成,将太平洋深海富稀土沉积物分为富Al型、富Fe型、富Ba型等三个类型。富Al型富稀土沉积物广泛布在西太平洋地区,沉积物类型以沸石黏土为主,全岩Al₂O₃平均含量可达14.9%。富Fe型富稀土沉积物位于东太平洋海隆附近的东南太平洋和东北太平洋区域,沉积物中TFe₂O₃平均含量高达18.8%,部分样品呈现明显的Eu正异常,热液活动可能为稀土元素的富集提供了丰富的稀土元素及载体矿物。富Ba型富稀土沉积物主要分布于东太平洋CC区,沉积物类型主要是(含)硅质黏土,Ba平均含量可达8 092×10^-6。高Ba含量指示了沉积物形成时期所在海域可能具有很高的初级生...     

北冰洋门捷列夫海岭富锰棕色层稀土元素组成特征与来源初步分析

北冰洋深海广泛分布的富锰棕色沉积层(棕色层)是海冰、洋流、物源供给等多种因素共同作用的结果，本文基于西北冰洋门捷列夫海岭ARC07-E25岩芯沉积物稀土元素与微量元素含量、颜色反射率参数、粗颗粒组分和无机碳含量的变化特征，对该类沉积层中稀土元素的组成特征、形成机制和物质来源进行了综合分析。结果显示，沉积物稀土元素总含量(∑REE)在122.37×10?6～231.94×10?6之间变化，北美页岩标准化配分模式显示出轻微的中稀土(MREE)富集以及由La、Ce、Nd主导的较强的轻稀土(LREE)优势。沉积物中∑REE随着粗组分颗粒(如冰筏碎屑)的增多而呈现降低趋势，表明门捷列夫海脊沉积物中的稀土元素主要富集在细粒沉积物中。根据∑REE在沉积物中的变化特征将E25岩芯沉积物划分为4种地层，反映出了冰期/间冰期的气候转变过程中温暖条件下形成的棕色层与寒冷条件下形成的浅灰绿色沉积层(灰色层)的岩性旋回中稀土元素组成的差异，由于两种沉积层在形成时受到不同的底层水氧化还原环境的控制，导致了铈(Ce)元素在氧化水体中会由Ce3+氧化为Ce4+并发生沉降，而在还原水体中则由Ce4+还原为Ce3+发生溶解，这一特性使LREE含量产生较大波动，进而影响到∑REE，使之趋于在代表氧化条件的棕色层中升高而在代表还原条件的灰色层中降低。R型因子分析和物质来源判别结果显示，E25岩芯沉积物中稀土元素与亲碎屑元素(Nb、U、Th)有较好的相关性，主要来源于东西伯利亚海和新西伯利亚群岛的近岸侵蚀物质以及勒拿河物质的输入。     

北极东西伯利亚陆架沉积物物源:来自黏土矿物和化学元素的证据

本文对北极东西伯利亚陆架表层沉积物进行了粒度、黏土矿物以及常微量元素测定,阐述了粒度、黏土矿物和常微量元素的分布特征。利用因子分析与聚类分析划分了不同的沉积区,并探讨了各区沉积物的主要来源。结果表明,研究区可以划分为4个沉积区:(1)东西伯利亚海近岸河口区(Ⅰ区),沉积物以粉砂和砂质粉砂为主,TiO₂、Zr、SiO₂含量较高,其他元素在该区都处于低值,La/Th与Zr/Hf比值在4个沉积区中为最大值,黏土矿物中伊利石含量占绝对优势,约为70%,该区受到河流与海岸侵蚀物质输入的强烈影响;(2)东西伯利亚海中部(Ⅱ区),沉积物以粉砂和泥为主,MnO、Ba与Ni等元素在该区含量较高,黏土矿物组合与Ⅰ区类似,La/Th和Zr/Hf比值比Ⅰ区略低,该区沉积物以河流输入的细粒沉积物为主,受海冰等过程的影响发生了混合,随着离岸距离的增加,海洋自生组分开始增多;(3)东西伯利亚海北部深水区(Ⅲ区),沉积物以泥为主,Al₂O₃、K₂O、V、Li等在该区达到最大值,La/Th和Rb/Th比值与Ⅱ区极其类似,伊利石含量在该区为最低值,蒙皂石与高岭石含量在该区达到最大值(>10%),该区细粒沉积物很可能受大西洋水体以及波弗特环流的影响;(4)楚科奇海(Ⅳ区),该区沉积物主要由粉砂和砂质粉砂组成,CaO、P₂O₅等在该区含量较高,Rb/Th、La/Th与Zr/Hf均为4个沉积区的最小值,绿泥石在该区最为富集,该区沉积物受太平洋入流水的影响强烈。     

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...     

Major,Trace, and Rare Earth Elements in the Sediments of the Central Indian Ocean Basin: Their Source and Distribution

Abstract

A large number of surface sediments as well as short sediment cores collected in the Central Indian Ocean Basin have been subjected to various geochemical investigations during the last one and half decade. The studies varied, covering different aspects of sediments and resulting in a number of publications. In the present article, we have put together the data from 82 surface sediments and 14 short sediment cores, including 25 new analyses, to study the trend of their distribution and source at large. The distribution maps of elements show that highest concentrations of Mn, Cu, Ni, Zn, Co, and biogenic opal in the surface sediment occurs between 10°S and 16°S latitude, where diagenetic ferromanganese nodules rich in Mn, Cu, Ni, and Zn are present. The studies highlight that the excess element concentration (detrital unsupported) such as Mn, Cu, Ba, Ni, Co, Pb, and Zn have contributed >80% of their respective bulk composition. These excess elements exhibit strong positive correlation with each other suggesting their association with a single authigenic phase such as Mn oxide. Biogenic opal contributes 30–50% of the total silica in the siliceous sediment. Aluminum, Fe, and K have contributed >60% from terrigenous detrital source compared to their bulk composition. In calcareous ooze, Ca, and Sr excess contribute >95% while, in siliceous ooze it is only 50% of their bulk composition. Nearly 35% of structurally unsupported Al in the sediment raises doubt of using Al as a terrigenous index element to normalize the trace and minor elements. Biogenic apatite is evident by the positive correlation between Ca (<1%) and P. Calcium, Sr, and P depict a common source such as biogenic. Bulk element concentration such as Li, V, Cr, Sc, and Zr are positively correlated with Ti indicating their terrigenous detrital source. Rare earth element (REE) concentration increases from calcareous ooze to siliceous ooze and reaches a maximum in the red clay. Presence of positive Eu-anomaly in these sediments has been attributed to aeolian input. REE in these sediments are mostly carried by authigenic phases such as manganese oxide and biogenic apatite. Based on the distribution of transition elements in the sediment cores, three distinct zones—oxic at top, suboxic at intermediate depth, and a subsurface maxima—have been identified. Oxic and suboxic zones are incidentally associated with high and low micronodule abundance in the coarse fraction (>63 μm) respectively. Ash layers encountered at intermediate depth between 10 to 35 cm are correlative with the Youngest Toba eruption of ～74ka from Northern Sumatra. This ash is mainly responsible for the high bulk Al/Ti ratio up to 48.5 (three times higher than Post Archean Australian Shale), other than scavenging of dissolved Al by biogenic components.     

南海东部海域表层沉积物类型的研究

南海东部海域表层沉积物可被分为11种类型:含岩块砾石黏土质粉砂、贝壳珊瑚砂、黏土质粉砂、钙质黏土、钙质软泥、有孔虫砂、深海黏土、含铁锰微粒粉砂质黏土、硅质黏土、含火山灰硅质黏土、含火山灰粉砂质黏土.这些类型按物源和成因可被分为陆源碎屑、钙质碎屑和硅质碎屑、火山碎屑3大类型,其中陆源碎屑分布面积约占50%,钙质碎屑占20%,硅质碎屑和火山碎屑各占15%.在物质来源、海底地形、火山作用、生物作用、水动力条件等因素影响和控制下,由于沉积环境的差异,故区内褐色类沉积物最多(60.68%),灰色类沉积物次之(38.20%),黄色类沉积物最少(1.12%).台湾省以南到17°N以北海区沉积物以陆源沉积物分布为主;巴士海峡以西海区沉积物较粗,常含砂岩块和砾石;东沙群岛以东海区钙质生物碎屑沉积丰富;中、西部海区以含铁锰微粒沉积物为主;中、南部海区水深大,主要分布硅质沉积物;南部海区、礼乐滩北缘沉积物受礼乐滩珊瑚碎屑影响大,沉积物类型为钙质软泥.     

深海沉积物分类与命名

详细分析了国内外深海沉积物分类与命名现状,迄今为止深海沉积物分类与命名问题没有很好解决。在调查研究南海、太平洋深海沉积物分类与命名基础上,提出了分类简便、科学合理、量化的深海沉积物分类与命名新方法,应用该方法得出南海东部海域深海沉积物有深海粘土、硅质粘土、钙质粘土、硅钙质粘土、钙质软泥、粘土质钙质软泥、粘土质-硅质钙质软泥、粘土-硅质-钙质混合软泥、粘土质硅质-钙质混合软泥、钙质硅质-粘土混合软泥。这10种沉积物基本上客观地反映了南海东部海域深海沉积物分布的实际情况,分类效果良好。     

Distribution pattern and morphochemical relationships of manganese nodules from the Central Indian Basin

In the Central Indian Basin manganese nodule abundance was variable in all sediment types. Mean abundance varied from 1.5 in calcareous ooze to 10.2 kg/m² in terrigenous-siliceous ooze sediments. Nodule grade and growth rates are positively correlated only up to 10 mm/My (million years), and grade shows no distinct relationship with abundance. Relationships between the morphochemical characteristics of the nodules and host sediment types are subtle. Both hydrogenetic and diagenetic nodules (with smooth and rough surfaces respectively) occur on almost all sediments, but in variable proportions. Thus, the overall distribution pattern shows that small nodules (<4-cm diameters) of lower grade (average value Ni+Cu+Co=1.21%) with smooth surfaces are more common on red clay, terrigenous, and terrigenous-siliceous ooze transition-zone sediments. By contrast, large nodules (>4-cm diameters) of higher grade (average value Ni+Cu+Co=1.80%) with rough surfaces are more prevalent on siliceous ooze, siliceous ooze-red clay, and calcareous ooze-red clay transition-zone sediments. This implies an enhanced supply of trace metals from pore waters to rough-surface nodules during early diagenesis.     

Iron and manganese micro-precipitates within a cretaceous biosiliceous ooze from the Arctic Ocean: possible hydrothermal source

The oldest sediment most recently recovered from the Arctic Ocean is a biosiliceous ooze nearly devoid of nonbiogenic particles and exhibiting small-scale color changes. Color variations are due to changes in iron and manganese content. These elements are probably of local hydrothermal origin, and the Mn precipitation may be bacteria-mediated. An iron silicate phase seems to form at the expense of biogenic silica. The ooze deposited slowly until a sudden sediment input, probably a volcanigenic deposit now weathered to clay minerals, induced dissolution of siliceous microfossils. This clay layer contains calcium phosphate microspheres enriched in rare earth elements.     

In Memoriam

Abstract

The engineering properties of deep continental margin sediments were determined on a worldwide basis. Deep Sea Drilling Project (DSDP) core data and material were utilized from over 900 cores obtained from 89 sites, primarily on the continental margins. Cores were recovered from penetrations to 200 m in water depths averaging 3000 m. Supplementary laboratory testing on selected cores was directed toward determining index properties and shear strength properties of the sediments. The study included a literature review of deep‐sea soil properties, the results of which are to be used by DSDP to evaluate foundation conditions for reentry cones with long casing strings. The results will also be used for a feasibility study of an ultradeepwater marine riser and well‐control system. The marine sediments examined can be divided into three main types: clay, calcareous ooze, and siliceous ooze. Sediment distribution consisted of 48% calcareous ooze, 43% clay, 6% siliceous ooze, and 3% volcanic ash. Because of the sample disturbance inherent in the deepwater coring operation, emphasis was placed on analyzing sediment properties not significantly affected by changes in in situ stresses and structure caused by sampling. Averages and ranges in values of water content and unit weight are presented for the three main sediment types. Plasticity and strength characteristics are discussed in detail and the elastic and compression properties are outlined. The geotechnical properties of deep continental margin soils are summarized.     

长江口海域表层沉积物常量元素地球化学及其地质意义

通过对长江口外海域187个表层沉积物样品进行常量元素氧化物(SiO₂,Al₂O₃,Fe₂O₃,MgO,CaO,Na₂O,K₂O,P₂O₅,TiO₂,MnO,TOC和 CaCO₃)测试,分析其空间分布特征及其地质意义。结果显示,研究区表层沉积物常量元素氧化物主要由SiO₂,Al₂O₃,Fe₂O₃,MgO,CaO,Na₂O,K₂O和TiO₂等组成,这8种组分约占沉积物总量的91.59%;其中SiO₂和Al₂O₃含量最高,平均值分别为62.43%和11.16%。R型因子分析结果表明,研究区表层沉积物的常量元素氧化物可以分为3类:第1类包括SiO₂,Al₂O₃,Fe₂O₃,MgO,P₂O₅,TiO₂和MnO;第2类包括CaO,K₂O,CaCO₃和TOC;第3类包括Na₂O,这3类可能分别代表了陆源碎屑沉积、海洋生物和陆源混合沉积以及海洋化学沉积。Al₂O₃/Na₂O和CIA的空间分布较为相似,指示了长江入海物质主要堆积在长江口及其以南的123.5°E以西海域,闽浙冬季沿岸流是其主要驱动力。