日本Nankai增生楔中的宏观变形机制

This proposal aims at the geometrical, petro-physical, petro-chemical and modal aspects of maroscopic soft-sediment deformation structures, including vein structures, deformation bands, shear bands, faults, and so forth, in cores at the IODP C0002 Site, Nankai trough, IODP 338 Expedition. Their slip senses, sizes, orientations, internal fabrics, relative ages, spatial distributions, changes in porosity, and possible petro-chmeical and/or mineralogical changes, as well as their counterparts at outcrop, will be investigated in various ways, from which we know the similarities and differences in geometry, petro-physics and petro-chemistry between the structures of different types, and from which we determine determine the mechainisms of the structures. These results will add knowledage about soft-sediments deformation in shallow parts of the submerging accretionary prisms.

本申请将从几何形态、岩石物理、岩石化学和模态方面研究日本Nankai海槽IODP C0002点的钻孔取芯(IODP338航次)中发育的脉构造、变形带、剪切带和断层等宏观的松软沉积物变形构造，查明这些构造的性质、尺度、产状、内部结构、相对时代、空间分布、孔隙度变化、可能的岩石化学或矿物学变化等，找出它们之间在几何形态、岩石物理和岩石化学上的差同，且与地表露头的同类变形构造做对比，进而确定它们的形成机制，由此增进对隐伏增生楔的表层中松软沉积物构造变形的认识。

松软沉积物的变形构造发生在成早期岩与构造变形的共同或独立作用下，可以用来由表及里地研究正在发生、深处的构造过程。本项目以项目负责人参加IODP338（“Nankai海槽地震发震带实验”）和362（“苏门答腊海沟发震机制”）航次时所获取的变形构造样品、发育变形带的湖北远安白垩纪裂谷盆地和河南登封震旦系地层里发育的滑塌构造为研究对象，分析和对比典型的松软沉积物变形构造（如脉构造、变形带和剪切带等）的产状、性质、内部结构、空间分布等，进而确定它们的形成机制。发现在IODP362航次U1480G钻孔浅部（约700 MBSF）一个近水平、薄的粘土层中发育鳞片状结构（scaly fabric），具有与脉构造相似的诸多特征，意味着脉构造并不局限在海沟靠陆侧的增生楔里；在远安盆裂谷地变形带呈面状密集产出的下白垩统红花套组巨厚层细砂岩属于风成砂丘的成因，具有高的孔隙度，表明构造作用和沉积物或岩石的高孔隙度是造成变形带密集发育的两个必要条件。