Collaborative Research:Expedition 322 Objective Research on the nature and history of subsurface flow within the Nankai sediments prior to subduction

学术价值：NantroseIZE是孕震带倡议的中心部分，旨在揭示俯冲巨型逆冲的水文过程。项目的关键组成部分，也是IODP Exp的目标。322，是板块进入俯冲带之前进入的沉积地层和火成岩基底顶部的特征。在四国盆地钻探了两个参照点(C0012和C0011)，与以前在变形前锋(ODP131和190)海面钻探的其他地点进行分析时，这为描述俯冲输入的特征提供了一个理想的数据库。虽然仍然不受俯冲过程的影响，但这些输入受到来自深度脱水反应区的横向流体迁移的影响。限制这一水文状况是解开流体和成岩反应对深部板块界面地质力学性质影响的关键。船上的结果表明，有趣的可能性是，来自不同来源的两种流体通过海沟的沉积层向海迁移。一种体制(以流体清新和甲烷和较高级碳氢化合物的存在为特征)是由俯冲沉积物中的流体排出和俯冲输入中的高渗透性层位上倾迁移所驱动的。另一种流动模式(以深部硫酸盐的存在为特征)是由类似海水的流体通过上层大洋地壳进入上覆沉积物的砂岩浊积岩所驱动的。在这两种流体的交界处，微生物活动似乎受到了刺激；新发现的甲烷活性厌氧氧化(AOM)深区约为417Mbsf，甲烷浓度的峰值与硫酸盐的完全消耗和孔隙水硫化物的显著增加相吻合。在这里，我们建议：1)在与其他船上科学家的合作项目中使用孔隙水数据来表征这些流动状态的性质；以及2)通过分析自生相(碳酸盐和重晶石)来推断这些发现，其中包含流体来源(锶同位素)、代谢过程(碳和硫同位素)和形成温度(块状氧同位素)的记录。最近开发的块状氧同位素(即多重取代同位素)分析已被证明有效地将结晶温度限制在±2.4℃。对在井底附近发现的选定碳酸盐矿脉和胶结物的测量将提供有关流体温度的关键数据，这些数据有助于表征进入的沉积物的状态特征；依赖温度的成岩反应；地下微生物群落。在实验期间没有收集到现场温度数据。322.除了提供有关收入板块较低地层的基本地球化学信息(Exp.322)，这里产生的数据集将被用来促进我们对新假设的和非常重要的主题的理解：1)来袭板块下层中的流动的历史和性质，其中可能包括--到目前为止尚未记录在案的--上层洋壳中的流体流动状况；以及2)深生物圈过程，其中包括新发现的AOM带，它由上层含硫酸盐的基底流体提供的电子受体支持。广泛的影响：我们将收集的数据集将使我们能够提供关于流体在俯冲地层中的地球化学、地质力学和地球生物过程中的作用的基本信息，这是这次考察的一个关键目标。我们的数据将以完全整合和合作的方式与其他NantroSeize科学家共享。除了这些合作，Peckman教授(不来梅大学)已经同意分析碳酸盐中的生物标记物，这项提议是免费的。该项目将直接支持两名研究生和一名本科生的论文研究。外展工作包括通过俄勒冈州立大学(http://smile.oregonstate.edu/)，)的SILE计划传播孕震带进程(http://literacyworks.org/ocean/))，以及通过亚利桑那州教育部的数学-科学伙伴计划为在职教师开设专业发展课程。

Intellectual merit: NanTroSEIZE, a central part of the Seismogenic Zone Initiative, is aimed at unraveling hydrologic processes at subduction megathrusts. A key component of the project, and the target of IODP Exp. 322, is the characterization of the incoming sedimentary strata and the top of igneous basement prior to the plate entering the subduction zone. Two reference sites (Sites C0012 and C0011) were drilled in the Shikoku Basin, which, when analyzed in the context of other sites previously drilled seaward of the deformation front (ODP Legs 131 and 190), provide an ideal database to characterize subduction inputs. Though still unaffected by subduction processes, these inputs are influenced by lateral fluid migration from zones of deeperseated dehydration reactions. Constraining this hydrologic regime is key to unraveling the effect of fluids and diagenetic reactions on the geomechanical properties of the plate interface at depth. Shipboard results point to the intriguing possibility of two fluids from different sources migrating through the sedimentary strata seaward of the trench. One regime (characterized by fluid freshening and the presence of methane and higher hydrocarbons) is driven by expulsion of fluids from the subducting sediment and up-dip migration through high permeability horizons in the subduction inputs. The other flow regime (characterized by the presence of sulfate at depth) is driven by migration of a seawater-like fluid through the upper oceanic crust into the sandstone turbidites of the overlying sediment. At the interface of both fluid regimes, microbial activity appears to be stimulated; with a newly discovered deep zone of active anaerobic oxidation of methane (AOM) at approximately 417 mbsf, where peak methane concentrations coincide with the complete consumption of sulfate and a marked increase in pore-water sulfide. Here we propose to: 1) characterize the nature of these flow regimes using pore water data in a collaborative program with other shipboard scientists; and 2) extrapolate these findings through time by analyses of authigenic phases (carbonates and barites), which contain a record of fluidsources (strontium isotopes), metabolic processes (carbon and sulfur isotopes) and formation temperatures (clumped oxygen isotopes). The recently developed clumped oxygen isotope (i.e. multiply-substituted isotopologues) analysis has been shown to effectively constrain temperatures of crystallization to ± 2.4 °C. Measurement on select carbonate veins and cements recovered nearthe bottom of the holes will provide key data on fluid temperatures needed to characterize: the state properties of the incoming sediments; temperature-dependent diagenetic reactions; and subsurface microbial communities. No in situ temperature data was collected during Exp. 322. In addition to providing information on basic geochemistry in the lower strata of the incomingplate (a key objective of Exp. 322), the data sets generated here will be used to further our understanding of newly postulated and highly significant topics: 1) history and nature of flow in the lower strata of the incoming plate, which may include an -as of yet undocumented- fluid flow regime in the upper oceanic crust; and 2) deep biosphere processes, which include a newlydiscovered AOM zone that is sustained by the electron acceptors supplied by an upper basement flow of sulfate bearing fluids.Broader impact: The data set we will assemble will allow us to provide fundamental information on the role of fluids on the geochemical, geomechanical and geobiological processes in the subducting strata, a key objective of the expedition. Our data will be shared with other NantroSeize scientists, in a fully integrated and cooperative effort. In addition to thesecollaborations, Prof. Peckman (U. of Bremen) has agreed to analyze biomarkers in the carbonates at no cost to this proposal. The project will directly support the thesis research of two graduate students, and an undergraduate research fellow. Outreach efforts include dissemination of Seismogenic zone processes through The SMILE program at Oregon State University (http://smile.oregonstate.edu/), Adult Education across the State of Oregon(http://literacyworks.org/ocean/) and professional development courses for in-service teachers through the Math-Science Partnership Program of the Arizona Department of Education.