Fluid flow and diagenesis in the incoming oceanic plate lithostatigraphy to the Sumatra subduction zone: a geochemical approach

2004年12月26日，苏门答腊-安达曼地震，矩震级为Mw=9.2破裂约。1300公里的板块界面，同震滑动向海传播到海沟，造成毁灭性的海啸。这一事件是不寻常的，因为最外层增生棱柱体下方的板块边界推力通常被认为是不稳定的。在传入部分的高度的岩化已被提出来解释向海移动的地震滑动和不寻常的几何形状的苏门答腊增生棱镜。 然而，这一假设的验证仍然悬而未决，因为迄今为止尚未通过科学海洋钻探对苏门答腊俯冲带的沉积物输入进行专门取样，这项研究建议的主要重点将是查明进入苏门答腊俯冲带的沉积物和海洋地壳中重要的成岩、蚀变和流体流动过程，并确定其时空特征。该研究将通过对孔隙流体和沉积物/基底样品进行地球化学分析来实施，这些样品将在2016年国际海洋发现计划第362次考察期间在苏门答腊西北部近海取样。具体而言，工作计划将包括：（1）通过锂和硼同位素分析，结合流体和全岩地球化学和X射线衍射分析，确定水-岩相互作用过程及其来源深度;（2）将地球化学数据与流通实验和反应传输模型的结果相结合，以了解传入大洋板块岩石地层学的水文地质学。

On 26 December 2004, the Sumatra-Andaman earthquake with a moment magnitude of Mw=9.2 ruptured approx. 1300 km of the plate interface with coseismic slip propagating seaward to the trench causing the devastating tsunami. The event is unusual because the plate boundary thrust beneath the outermost accretionary prism is usually assumed to be aseismic. A high degree of lithification in the incoming section has been proposed to explain the seaward shift of seismogenic slip and the unusual geometry of the Sumatra accretionary prism. However, validation of this hypothesis is still outstanding because the sedimentary input to the Sumatra subduction zone has not been specifically sampled by scientific ocean drilling so far.The main focus of this research proposal will be the identification and spatio-temporal characterization of important diagenetic, alteration and fluid flow processes in the incoming sediment and oceanic crust to the Sumatra subduction zone. The research will be implemented by geochemical analysis of both pore fluids and sediment/basement samples that will be sampled offshore NW Sumatra during Expedition 362 of the International Ocean Discovery Program in 2016. In detail the work program will encompass: (1) Identification of water-rock interaction processes and their source depths via lithium and boron isotope analysis in combination with fluid and whole rock geochemistry and X-ray diffraction analysis, and (2) integration of the geochemical data with results from flow-through experiments and reaction transport models to understand the hydrogeology of the incoming oceanic plate lithostratigraphy.