东太平洋海盆地山玄武岩特征

东太平洋海山玄下央属于大洋岛屿拉斑玄武岩，主要由橄榄拉斑玄武岩，石英拉斑玄武岩和橄榄玄武岩组成，具有拉斑玄武岩系列和过渡玄武央系列，岩石具有基质为斑拉玄武结构或间隐结构的斑状结构和气孔构造，斑晶主要由拉长石和普通辉石组成，基质除拉长石和玻璃质外，还有少量普通辉石和磁铁矿等，岩石化学成分中Ａｌ２Ｏ３Ｎａ２Ｏ，Ｋ２Ｏ含量偏高，玄武岩中稀土元素分配型式基本相同，曲线较平坦，稀土分馏不明显，具Ｃｅ，Ｅｕ异     

东太平洋海盆海山玄武岩特征

东太平洋海山玄武岩属于大洋岛屿拉斑玄武岩，主要由橄榄拉斑玄武岩、石英拉斑玄武岩和橄榄玄武岩组成，具有拉斑玄武岩系列和过渡玄武岩系列。岩石具有基质为拉斑玄武结构或间隐结构的斑状结构和气孔构造，斑晶主要由拉长石和普通辉石组成，基质除拉长石和玻璃质外，还有少量普通辉石和磁铁矿等，岩石化学成分中Ａｌ２Ｏ３、Ｎａ２Ｏ、Ｋ２Ｏ含量偏高。玄武岩中稀土元素分配型式基本相同，曲线较平坦，稀土分馏不明显，具Ｃｅ、Ｅｕ负异常，反映岩石具有共同的成因，属晚白垩世以来的产物     

马里亚纳海槽热液区岩石矿物学和岩石化学特征研究

马里亚纳海槽中央轴裂谷中的小扩张脊部位 ,广布火山喷发的玄武岩体 ,海底热液硫化物就是从这些岩体的裂隙中喷溢堆积起来的。利用我国“大洋一号”船拖网所获岩样进行了矿物学和岩石化学特征研究 ,认定为高铝低钾的大洋底玄武岩或拉斑玄武岩系列和钙 -碱玄武岩。为进一步弄清马里亚纳海槽区热液活动岩石学条件和探讨海槽区热液物质来源提供科学证据     

冲绳海槽浮岩中岩浆包裹体岩石化学成分特征

系统地分析了冲绳海槽酸性浮岸中玻璃质岩浆包裹体的岩石化学成分，探讨了包裹体的岩石化学成分特征及其在岩浆起源及结晶演化过程中的指示意义，并结合前期及前人工作讨论了冲绳海槽不同岩石类型之间的成因联系及演化关系。结果表明，斑晶结晶时岩浆熔体为钙碱性英安质或流纹质岩浆，是来自地幔的拉斑玄武质岩浆充分结晶分异作用的产物。尽管各斑晶矿物中玻璃质岩浆包裹体的化学成分有所差异，但根据包裹体的岩石化学成分特征可以断定包裹体所代表的岩浆具有同源性，其差异只是反映了岩浆结晶演化的不同阶段或不同矿物结晶期，为进一步详细研究浮岩岩浆的结晶演化过程提供了最直接的资料。对比冲绳海槽酸性浮岩与玄武岩等不同岩石类型的岩石化学特征，可以证明这些岩石类型之间存在着密切的成因联系，包括同源性与继承性，它们分别是岩浆作用不同阶段的产物。另外，包裹体的成分主要取决于包裹体所在斑晶矿物的种类与成分，分析中未发现岩石化学性质明显不同的岩浆包裹体共存的现象，也没有在中酸性矿物中发现基性玻璃质岩浆包裹体，因此可以推断基本不存在不同性质的岩浆之间的直接混合作用。     

科科斯脊玄武岩斜长石矿物化学及地质意义

综合大洋钻探计划(IODP) 334和344航次在U1381站位处的两个钻孔(A孔和C孔)获得了中美洲西海岸外科科斯脊基底拉斑玄武岩,对其岩浆过程开展研究可为理解其岩石成因提供重要依据。本文对科科斯脊玄武岩中斜长石斑晶和微晶进行了详细的原位主微量元素分析,结果表明,斜长石种属为培长石、拉长石及少量中长石。部分斜长石斑晶具有正环带结构;但多数斜长石斑晶不具有明显环带,仅从核部到边部存在微弱的成分变化。斜长石斑晶与微晶的微量元素差别较大:斜长石斑晶富集轻稀土和大离子亲石元素、亏损高场强元素,且具有明显的Eu正异常;斜长石微晶不相容元素含量通常高于斜长石斑晶。根据斜长石温度计计算获得斜长石斑晶结晶温度为1 050～1 253℃,斜长石微晶结晶温度为866～1 033℃。基于以上特征,推测斜长石斑晶核部是相对原始岩浆的产物,而斑晶边部以及微晶是演化岩浆的结晶产物。斜长石斑晶的成分变化及熔蚀麻点结构是由于岩浆补给及岩浆减压上升造成的。最后,本研究推测科科斯脊基底玄武岩来自于开放的岩浆房,且岩浆房内可能存在原始岩浆的不断注入及岩浆对流。     

麦哲伦海山区MA、MC海山玄武岩基岩的岩石学特征

麦哲伦海山区MA、MC海山玄武岩基岩的岩石学特征研究表明,岩性为蚀变玄武岩、橄榄玄武岩等;结构为基质具间隐、间往结构及拉斑玄武结构的斑状结构;矿物组成为斜长石、橄榄石、辉石及脱玻化玻璃等。按岩石化学成分分类属碱性玄武岩,而稀土分配模式属洋岛碱性玄武岩类型。     

冲绳海槽碱性玄武岩浆的起源及演化

利用电子探针对冲绳海槽133站位玄武岩的斑晶矿物、基质以及斑晶矿物中关晶石包体和岩浆包裹体作了化学主成分分析,结果表明,该站位玄武岩属橄榄玄武岩,岩石中斑晶矿物由培长石、普通辉石、贵橄榄石和磁铁矿组成,尚见有少量外来的脉石英碎块,基质成分由拉长石微晶和玻璃组成。培长石和贵橄榄石中含有玻璃质岩浆包裹体和铬镁尖晶石或铬镁铁尖晶石包体。尖晶石的化学成分证明它是地幔部分熔融成因的。岩浆包裹体代表了一种原生的碱性橄榄玄武岩浆,其化学成分相当于橄榄辉长岩。该站位的玄武岩浆起源于上地幔尖晶二辉橄榄岩的部分熔融,并沿着“碱性橄榄玄武岩浆-粗面玄武岩浆-玄武质粗面岩浆-粗面岩浆”方向演化,每一阶段的岩浆在上升过程中都不同程度地受到地壳物质的同化和混染作用。     

大洋岛屿玄武岩低温蚀变作用及其对大洋过渡金属循环的贡献

用化学方法和ICP-MS方法分别对中、西太平洋海山富钴铁锰结壳产出区玄武岩的主元素、微量元素和稀土元素(REE)含量进行了测定,结果表明,研究区玄武岩经受了强烈的洋底低温蚀变作用,主元素成分发生了明显的变化,失去了原岩的特征.样品与新鲜大洋岛屿玄武岩(OIB)极为相似的稀土元素配分模式和微量元素含量特征表明,所研究的岩石属典型的大洋板内玄武岩.受洋底低温蚀变作用的影响,样品的Al₂O₃,Fe₂O₃,MnO、K₂O,P₂O₅含量增加,MgO,FeO的含量降低.蚀变作用使大洋岛屿玄武岩中的镁、铁等活动组分大量流失,从而表现出相对富SiO₂的特征(标准矿物计算结果中出现石英).由于蚀变作用,活动组分的流失使样品的REE相对富集,而富REE铁锰氧化物在玄武岩气孔和裂隙中的沉淀不仅使样品的REE含量增大,而且引起轻稀土元素(LREE)与重稀土元素(HREE)分馏,表现为∑c(Ce)/∑c(Yb)值增大.以REE富集机制为基础,对样品中铁锰氧化物的沉淀量和单位质量新鲜玄武岩中活动组分的流失量进行了理论计算,结果表明,因低温蚀变作用所引起的新鲜玄武岩的单位质量亏损为0.150~0.657,而单位质量新鲜玄武岩中铁锰氧化物的沉淀量为0.006~0.042.主元素中以铁、镁的流失亏损最为明显,新鲜玄武岩中铁、镁的流失比例分别为18.28%~70.95%和44.50%~93.94%,超过了岩石总量的流失亏损比例(15.0%~65.7%),因而样品相对贫铁、镁.其他元素的流失量和流失比例都很好地印证了地球化学研究的结果.样品中铝、钾、磷负的流失量是由于沸石在岩石气孔中的充填和岩石的磷酸盐化.理论计算结果和地球化学研究都表明,大洋岛屿玄武岩的低温蚀变向海水提供了大量金属,这是大洋海水中金属循环的重要环节.     

南马里亚纳海槽岩石学特征

南马里亚纳海槽岩性比较复杂：有玄武岩，根据标准矿物组合，进一步划分为碱性玄武岩，橄揽拉斑玄武岩和石英拉斑玄武岩；火山碎屑岩，包括凝灰岩和角砾凝灰岩；以及方辉橄榄岩．大部分玄武岩样品是距今五百万年以后形成的，个别岩石样品的形成年龄为八百万年左右．不同类型的玄武岩是含Ｈ２Ｏ的地幔岩块在底辟上升过程中，局部熔融、分离的产物；火山碎屑岩是火山喷发的火山灰、火山砾被水化学分解的物质胶结而成；方辉橄榄岩是地幔岩浆底辟上升直接侵入结晶的产物．     

冲绳海槽南部橄揽拉斑玄武岩研究

1995年夏季航次冲绳海槽地质、地球物理调查对海底岩石实施拖网取样，在与那国海底洼地西南边线采集到新鲜玄武岩样品。对岩石样品进行了薄片鉴定、岩石化学分析、稀土和微量元素分析以及银同位素分析等。结果表明，岩石为橄榄拉斑玄武岩，岩石微量元素和稀土元素分布具有地慢柱洋中脊玄武岩的特点；成岩熔浆来自上地慢，分异程度较低，混合作用较弱，结晶液线温度为1150－1200℃。     

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.     

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.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.     

INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,     

Estimation of Sediment Properties during Benthic Impact Experiments

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.