冲绳海槽及邻区磁异常特征及其地质解释

对冲绳海槽及邻区的ΔT磁异常特征进行了定性分析和变纬度化极处理,通过对比ΔT磁异常和化极磁异常分布特征,对冲绳海槽及邻区几个构造地质学问题进行了探讨。冲绳海槽基底埋深较大,沉积中心位于海槽西部;钓鱼岛隆褶带大规模基底隆起的南端终止于渔山-久米断裂带,断裂带以南的东海陆架南部边缘覆盖了厚层沉积物;以渔山-久米断裂带、舟山-国头断裂带和吐噶喇断裂带为代表的NW-NWW向右旋平移断裂带在东海构造演化过程中自西向东逐渐前展,对构造应力场起到了重要的调节作用,是东海"南北分块"构造格局中主要的构造单元边界;中新世以来台湾碰撞造山作用引起了东海陆架南部主要构造单元的顺时针旋转;菲律宾海板块的俯冲对琉球弧前地区的磁异常分布产生了显著影响。     

东海瓯江凹陷早第三纪裂谷期盆地充填机制探讨

早第三纪东海瓯江凹陷曾是一个弧后拉张形成的裂谷盆地,拉张断裂在构造上控制了盆地地堑、半地堑地貌,从裂谷早期、中期到晚期,地层垂向演化表现出砂－泥－砂三重序列的充填型式,根据位于不同构造单元的SM－1、WZ6－1－1井为例证,从相对海平面、可容空间、物源供给诸方面探讨了地层成因机制。     

Germanium occurrence in Lincang superlarge deposit in Yunnan,China

Quantitative analyses have been carried out on radiolarians from 65 samples of Core 255 in the southern Okinawa Trough. The distribution of taxa and the results of Q-mode factor analysis show that during the last 20 000 years three radiolarian assemblages could be distinguished which can be correlated to high and low productivity levels indicated by the organic carbon content, radiolarian abundance and ratio of Nassellaria/Spumellaria in the sediment. TheTetrapyle quadriloba assemblage of thr last glaciation and deglaciation is associated with high productivity whereas the early HolocenePolysolenia spinosa and the middle and late HoloceneCarposhaera globosa assemblages correspond to low surface productivity. Meanwhile, the variations in the ratio of radiolarian fragments indicate higher SiO₂ dissolution during the Holocene than during the last glacial stage.     

Noble gases in pillow basalt glasses from the northern Mariana Trough back-arc basin

Noble gas concentrations and isotopic compositions have been measured in eight samples of pillow basalt glasses collected from seven different localities along 250 km of the Mariana Trough spreading and rifting axis. The samples have uniform and mid-ocean ridge basalt (MORB)-like ³He/⁴He values of 9–12 × 10^–6 (6.4–8.6 times atmospheric) despite large variations in ⁴He. Concentrations of the noble gases Ne, Ar, Kr, and Xe show much smaller variations between samples, but larger variations in isotopic compositions of Ne, Ar, and Xe. Excess radiogenic ²¹Ne is observed in some samples. ⁴⁰Ar/³⁶Ar varies widely (atmospheric to 1880). Kr is atmospheric in composition for all samples. Some samples show a clear excess ¹²⁹Xe, which is a well-known MORB signature. Isotopic compositions of the heavier noble gases (Ar, Kr, and Xe) in some samples, however, show more atmospheric components. These data reflect the interaction of a MORB-like magma with an atmospheric component such as seawater or of a depleted mantle source with a water-rich component that was probably derived from the subducting slab.     

冲绳海槽及其邻域地球物理场与地壳结构特征

分析了冲绳海槽及其邻域的重、磁场特征，同时对研究区域的布格重力数据进行了上延拓及二次垂直导数计算．根据分析与计算可知，在冲绳海槽及其周边区域，重磁异常的主要走向为NNE向，重、磁场的分布特征表明冲绳海槽及邻域地球物理场变化复杂，变化幅度大．参考地震解释结果，利用重力资料，应用调和级数法对研究区的莫霍界面进行了反演计算，得到了该地区莫霍界面深度分布，计算表明冲绳海槽及邻域地区莫霍界面深度在28-4km之间变化，地壳厚度自西向东逐渐减薄，显示出陆壳-过渡壳-洋壳的转变过程．     

冲绳海槽中部和南部玄武岩的区域性差异及其成因研究

本文从岩石学和岩石化学角度出发 ,对冲绳海槽中部和南部玄武岩样品进行了对比研究。结果表明中部和南部玄武岩均系亚碱性玄武岩 ,其中前者兼具钙碱性系列和拉斑玄武岩系列两种性质 ,后者则主要属拉斑玄武岩系列。根据岩石化学特征命名 ,中部样品主体为石英拉斑玄武岩 ,南部样品则为橄榄拉斑玄武岩。两区海槽玄武岩岩浆均由下伏地幔岩部分熔融而成 ,但源区地幔性质不均一 ,岩浆演化程度各异。中部样品源区地幔性质为过渡型 ,结晶分异程度较高 ;南部样品源于近亏损或富集型的地幔 ,结晶分异程度较弱 ;另外两区玄武岩样品均受到了不同程度的陆壳物质混染。中、南部海槽玄武岩在岩石学、岩石化学方面的差异与源区地幔性质不均一和岩浆演化程度各异有直接关系。海槽玄武岩构造环境属于过渡洋中脊玄武岩 (张性 )与岛弧玄武岩 (压性 )之间 ,代表的仍是海槽早期的岩浆活动。     

冲绳海槽沉积物混合作用的研究

介绍了利用方向性同位素＾２１０Ｐａ活度在岩芯中的垂直分布，根据沉积作用的数学模式，结合有关资料对冲绳海槽海水－海底界面沉积物的混合作用强度进行了了探讨。＾２１０Ｐｂ资料表明冲绳海槽表层沉积物中，＾２１０Ｐｂ放射性活度存在空间差异，介于２６．２６－９２．４０ｄｐｍ／ｇ，沉积物混合系数个于０．５１－６．８８ｃｍ＾２．ａ，这反映了研究海区不同的混合作用强度和沉积环境。     

Back-arc rifting in the Okinawa Trough

Geological and geophysical data reveal that the Okinawa Trough shows incipient continental rifting, and crustal separation started from about 2 Ma. The early extensional movements in the trough are probably of Miocene age. In addition to the Miocene phase, two main periods of extension are recognized: a Pleistocene phase between 1.9 and 0.5 Ma and the present day phase. During the stage short central rifts (Central Grabens) were formed. The opening however, may have occurred only in the southern part of the trough basin having an average half spreading rate of 2 cm yr^?1 since Early Pleistocene time, producing its present width of several tens of kilometres. These activities were well represented by igneous intrusions, sedimentary facies and sedimentary structures in and around the Okinawa Trough. The width of the zone affected by back-arc extension (defined as Greater Okinawa Trough) is larger than the present Okinawa Trough, whose width is 200–250 km. The present form of the Greater Okinawa Trough started to form at the same time as that of the Okinawa Trough.     

马里亚纳海槽两沉积岩芯主要化学元素的因子分析

通过对马里亚纳海槽两沉积岩芯中主要化学元素的因子分析,其结果表明,化学元素的共生组合和含量变化,与火山碎屑矿物以及大部分由海底玄武岩和玄武质火山玻璃蚀变而成的粘土矿物密切相关.岩芯的化学成分主要来自火山喷发物,因此,元素的地球化学特征反映了该区火山作用的影响.     

南沙海槽南部海区表层沉积物重金属元素含量及其影响因素

南沙海槽南部海区表层沉积物重金属元素表现为亲陆性,丰度为:Ba>Sr>Zn>Ni>Zr>Pb>Cr>Cu>Co,浓集程度为Ba>Sr>Cr>Zr>Pb>Zn>Co>Ni>Cu,元素Cu-Zn,Cu-Ni,Cu-Ba及Ba-Zn呈明显正相关,Cu,Ni,Ba,Zn,Cr与水深变化关系较为密切。元素与CaCO3含量、氧化物含量、粒度组成的相关系数表明:（1）Pb,Co,Zr,既存在于陆源碎屑矿物晶格中,又以吸附状态被黏土吸附,还受碳酸盐沉积影响。（2）Sr,主要受生物碳酸盐沉积作用影响。（3）Cu,Zn,Ni,Cr,Ba,主要受黏土的吸附作用及铁锰氧化物的影响。