Collaborative Research: Expedition 322 Objective Research on Sediment-Pore Water Interactions Controlling Sediment Cementation and Deformation in the NanTroSEIZE Drilling Transect

胶结作用影响控制沉积物强度和变形的力学性质。小掺量颗粒包衣水泥可大大提高泥沙强度。因此，即使是很小的胶结作用也可能影响盆地的固结和控制沉积边缘的变形。之前对深海钻探项目现场297和大洋钻探项目现场1173和1177的样品进行的研究记录了颗粒包覆硅水泥对菲律宾海板块接近四国盆地中部和西南部南开海槽俯冲带时沉积物物理性质的影响。在这些地点，少量弥散在半深海沉积物中的玻璃在埋葬时被改变为硅胶。这种凝胶层覆盖了颗粒接触，抑制了沉积物的固结。胶结沉积物具有异常的孔隙度、地震速度和硬度。随着进一步的埋藏、构造变形的开始和温度的升高，胶结物的溶解和机械破裂导致沉积骨架的刚性和坍塌(即孔隙度损失)显著降低。不同地点之间沉积物热历史、流体流动和孔隙水化学的差异如何控制胶结带位置和范围的变化？将具有瞬变性质的胶结单元并入边缘楔体中如何影响变形的性质和分布？为了回答这些问题，将确定IODP站点C0011和C0012处的硅胶结物分布，并对站点C0011、C0012、1173和1177进行多组分反应传输建模。将测定NANTROSEIZE钻探地点C0011和C0012的样品的横波速度，以确定异常强化区域。选定用于研究沉积物-孔隙水相互作用的四个地点提供了一系列沉积物堆积和热史。这一结果将有助于检验流体流速和热状态对四国盆地沉积物中二氧化硅胶结的垂直位置和程度的影响。拟议的调查针对南开海槽地震孕育区实验(NantroSEIZE)的主要目标之一：确定地质差异如何影响南开边缘内的力学性质、渗透率、流体流动、孔压、剪切强度和地震破裂过程。这项拟议的研究可能会改变我们对增长边缘过程的理解，因为它揭示了以前被低估的对楔形变形的控制。通过研究控制沉积物进入俯冲带的胶结作用的过程，拟议的研究具有社会意义，因为它促进了对潜在危险的地震孕育边缘所起作用的机制的理解。变形特征控制着流体通过边缘楔子的排出。因此，沉积胶结和变形对边缘水文地质和流体压力的影响与板块界面上的应变积累和地震活动有关。这项拟议的研究将引起地震学家、地球化学家和水文地质学家的兴趣。这项工作通过资助新墨西哥理工学院(NMT)的一名研究生来增强人力资源，NMT是一家为拉美裔服务的机构。拟议中的项目将加强国立理工大学用于研究和教学的设施。外展工作包括通过俄勒冈州立大学的SILE方案(http://smile.oregonstate.edu/)，)和正在进行的COAS成人教育方案(http://literacyworks.org/ocean/).)传播孕震带进程此外，Pi？FS还将与COSEE太平洋伙伴关系(www.Coseepacignpartnership s.org)合作，参加他们在纽波特举行的GScience酒吧之夜，或讨论环太平洋地区的地震相关过程。

Cementation affects the mechanical properties that control sediment strength and deformation. A small volume of grain coating cement can greatly increase sediment strength. Therefore, even minor cementation may affect consolidation in basins and control deformation in accretionary margins. The effects of grain-coating silica cement on the physical properties of sediment on the Philippine Sea plate as it approaches the Nankai Trough subduction zone in the central and southwestern portions of the Shikoku Basin were documented by previous work on samples from Deep Sea Drilling Project Site 297 and Ocean Drilling Program Sites 1173 and 1177. At these sites, a small amount of glass disseminated throughout hemipelagic sediment is altered to a silica gel upon burial. The gel coats grain contacts, and inhibits sediment consolidation. The cemented sediment has anomalous porosity, seismic velocity, and rigidity. With further burial, onset of tectonic deformation, and increasing temperature, cement dissolution and mechanical breakdown leads to dramatic reduction in rigidity and collapse of the sediment framework (i.e. porosity loss). How do differences in sediment thermal history, fluid flow, and pore water chemistry between sites control shifts in the location and extent of the cemented zone? How does the incorporation of cemented units with transient properties into the margin wedge influence the nature and distribution of deformation? Toward answers to these questions, the silica cement distribution at IODP Sites C0011 and C0012 will be determined, and multicomponent reactive transport modeling for Sites C0011, C0012, 1173, and 1177 will be performed. The shear-wave velocity of samples from NanTroSEIZE drilling sites C0011 and C0012 will be determined to locate regions of anomalous strengthening. The four sites selected for examining sediment-pore water interactions provide a range of sediment accumulation and thermal histories. The results will allow examination of the effects of fluid flow rate and thermal state on the vertical location and extent of silica cementation in the Shikoku Basin sediments. The proposed investigation addresses one of the main goals of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE); to determine how geologic differences affect mechanical properties, permeability, fluid flow, pore pressure, shear strength, and earthquake rupture processes within the Nankai margin. The proposed study may transform our understanding of accretionary margin processes by shedding light on a previously underappreciated control on wedge deformation. By examining processes that control cementation of sediment entering a subduction zone, the proposed research has societal relevance as it advances understanding of the mechanisms at play in potentially hazardous seismogenic margins. Deformation features control fluid drainage through a margin wedge. Therefore, sediment cementation and deformation impact margin hydrogeology and fluid pressure, which are related to strain accumulation and seismicity on the plate interface. The proposed research will be of interest to seismologists, geochemists, and hydrogeologists. This work enhances human resources by funding a graduate student at New Mexico Tech (NMT), a Hispanic-Serving Institution. The proposed project will enhance facilities used for both research and teaching at NMT. Outreach efforts include dissemination of seismogenic zone processes through The SMILE program at Oregon State University (http://smile.oregonstate.edu/), and through an ongoing Adult Education program at COAS (http://literacyworks.org/ocean/). In addition, the Pi?fs will work with the COSEE?]Pacific Partnerships (www.coseepacificpartnerships.org) by participating in one of their ?gscience pub nights?h in Newport, OR discussing earthquake related processes around the Pacific Rim.