RESEARCH ON THE BASIS OF ACCRETIONARY PRISM FORMATION IN VIEW OF DEFORMATION AND DIAGENESIS OF PELAGIC SEDIMENTS

这项为期三年的深海沉积物(远洋沉积物)研究项目，主要研究了深海沉积物在吸积棱柱上的沉积和吸积过程。我们的项目主要集中在远洋沉积物在沉积时的机制和作用。主要研究对象是沉积过程中的结构变化，特别是沉积物在成岩作用和变形过程中的作用；因为在公海上的原始远洋沉积物由于垂直载荷而受到压实，而在吸积棱柱内受到较高温度和压力的水平应力。沉积物有自己的沉积环境和时代控制，因此利用微体化石获得的生物地层数据和物源确定也很重要。此外，矿物和块状岩石的化学和矿物学变化也与物理变化有关。使用了许多方法，但扫描电子显微镜是了解…织构的最重要的方法更多的沉积物。结果表明：具有代表性的远洋沉积物矿物为粘土，局部差异较大；蒙皂石主要沉积在火山弧前，硅质微体化石在远洋沉积物中占主导地位，可用于年龄测定；含蒙脱石的层位对增生棱柱的形成最重要；这一带成为棱柱的滑脱(机械边界)；远洋硅质沉积物只有非常缓慢的结构变化和化学/矿物成岩作用，而它们在并入增生棱柱的过程中大量转化为硅质岩，这意味着远洋沉积物对增生棱柱的形成具有最重要的作用；大型构造以远洋沉积为主，具有双重构造特征；增生棱柱的重建需要放射虫生物地层学和铬系尖晶石砂岩岩石学。较少

These three year project on deep-sea sediments (pelagic sediments) has done the research on the process of sedimentation and accretion to the accretionary prism. We mainly focused the project on the mechanism and the role of the pelagic sediments when they are accreted. The main target is the textural change during accretion, particularly how the sediments work during the diagenesis and deformation ; for the original pelagic sediments on the open ocean suffer compaction due to vertical loading, while they get horizontal stress with higher temperature and pressure within the accretionary prisms. The sediments have their own depositional environments and age control, so that the biostratigraphic data by means of microfossils, and provenance determination are also important. In addition the chemical and mineralogical change of the minerals and bulk rocks are also related to the physical change. Many methods were used, but the SEM is above all the most important way to know the texture of … More the sediments. We obtained many results as follows ;The representative pelagic sediment minerals are clays, and they are locally different ; smectite is largely deposited in front of volcanic arcs ; siliceous microfossils are dominant within the pelagic sediments, and they are useful for determination of the ages ; smectite-bearing horizon is most important for the accretionary prism formation ; this zone becomes the decollement (the mechanical boundary) of the prism ; siliceous deposits in the open ocean have only very slow change of texture and chemical/mineralogncal diagenesis, while they vastly change into chert during incorporation into the accretionary prism ; this means the pelagic sediments have the most important role for the formation of the accretionary prism ; pelagic sediments are responsible for the large structures which are characterized by duplex structures ; reconstruction of the accretionary prism need radiolarian biostratigraphy and chromian spinel sandstone petrography. Less