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

2004年12月26日，苏门答腊岛-安达曼震级为Mw=9.2的地震破裂。1300公里的板块界面与同震滑移向海沟传播，引发了毁灭性的海啸。这一事件是不寻常的，因为推向最外吸积棱柱下方的板块边界通常被认为是无地震的。在即将到来的部分，已经提出了高度的岩化作用，以解释发震滑动的海移和苏门答腊岛吸积棱柱的不寻常的几何形状。然而，这一假设的验证仍然很突出，因为到目前为止，对苏门答腊岛俯冲带的沉积输入还没有通过科学的海洋钻探进行专门的采样。这项研究计划的主要重点将是识别和描述进入苏门答腊岛俯冲带的沉积物和洋壳中重要的成岩、蚀变和流体流动过程。这项研究将通过对孔隙流体和沉积物/基底样品的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次远征期间在苏门答腊岛西北部近海取样。具体来说，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以及X射线衍射分析，识别水-岩相互作用过程及其来源深度，以及(2)将地球化学数据与渗流实验和反应输运模型的结果相结合，以了解即将到来的大洋板块岩石地层学的水文地质。

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.