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

合作研究：322探险队 目的 研究俯冲前南开沉积物内地下流的性质和历史

• 批准号: 1029981
• 负责人: Marta Torres
• 金额: $ 18.24万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1029981&HistoricalAwards=false
• 关键词: Collaborative; Research; Expedition; 322; Objective

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.

智力价值：NanTroSEIZE 是地震带计划的核心部分，旨在揭示俯冲巨型逆冲断层的水文过程。该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传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考地点（地点 C0012 和 C0011），当在变形前缘向海钻探的其他地点（ODP 腿 131 和 190）的背景下进行分析时，这两个参考地点提供了一个理想的数据库来表征俯冲输入。尽管仍然不受俯冲过程的影响，但这些输入受到来自深层脱水反应区域的横向流体迁移的影响。限制这种水文状况是揭示流体和成岩反应对板块界面深度地质力学特性影响的关键。船上结果指出了来自不同来源的两种流体通过海沟沉积地层向海迁移的有趣可能性。一种状态（以流体清新以及甲烷和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以及通过俯冲输入中的高渗透性层位的上倾运移驱动的。另一种流态（其特征是在深处存在硫酸盐）是由类似海水的流体通过上洋壳迁移到上覆沉积物的砂岩浊积岩中驱动的。在两种流体状态的界面处，微生物活动似乎受到刺激。新发现的甲烷活性厌氧氧化 (AOM) 深层区域的压力约为 417 mbsf，其中甲烷浓度峰值与硫酸盐完全消耗和孔隙水硫化物显着增加一致。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； 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）和地层温度（簇氧同位素）的记录。最近开发的团簇氧同位素（即多重取代同位素同位素）分析已被证明可以有效地将结晶温度限制在±2.4°C。对在孔底部附近回收的选定碳酸盐矿脉和胶结物进行测量，将提供表征所需流体温度的关键数据：进入沉积物的状态特性；温度依赖性成岩反应；和地下微生物群落。实验期间没有收集现场温度数据。 322. 除了提供传入板块下地层的基本地球化学信息（Exp.322 的一个关键目标）之外，这里生成的数据集还将用于进一步理解新假设的和非常重要的主题：1）传入板块下地层的流动历史和性质，其中可能包括上洋地壳中尚未记录的流体流动状况； 2）深层生物圈过程，其中包括新发现的 AOM 区域，该区域由含硫酸盐流体的上基底流提供的电子受体维持。更广泛的影响：我们将收集的数据集将使我们能够提供有关流体对俯冲地层地球化学、地质力学和地球生物学过程的作用的基本信息，这是这次探险的一个关键目标。我们的数据将与其他 NantroSeize 科学家共享，以充分整合和合作。除了这些合作之外，Peckman 教授（不来梅大学）还同意分析碳酸盐中的生物标志物，而无需为此提案支付任何费用。该项目将直接支持两名研究生和一名本科生研究员的论文研究。外展工作包括通过俄勒冈州立大学的 SMILE 计划 (http://smile.oregonstate.edu/) 传播地震带过程、俄勒冈州的成人教育 (http://literacyworks.org/ocean/) 以及通过亚利桑那州教育部的数学科学合作伙伴计划为在职教师提供专业发展课程。