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探险队俯冲前南开沉积物内地下流性质和历史的客观研究

• 批准号: 1029972
• 负责人: James Sample
• 金额: $ 15.08万
• 依托单位: Northern Arizona 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 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1029972&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 fluid sources (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 near the 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 incoming plate (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 newly discovered 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 these collaborations, 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.

智力优点：NanTroSEIZE是地震带倡议的一个核心部分，旨在揭示俯冲巨型逆冲断层的水文过程。该项目的一个关键组成部分，以及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。在四国盆地钻取了两个参考点（C 0012和C 0011），当与先前在变形前缘（ODP Legs 131和190）向海方向钻取的其他点进行分析时，这两个参考点提供了一个理想的数据库来表征俯冲输入。虽然仍然不受俯冲过程的影响，这些输入的影响，从深层脱水反应区的横向流体迁移。约束这种水文制度的关键是解开流体和成岩反应的地质力学性质的板块界面在深度的影响。船上的结果指出了两种来自不同来源的流体通过海沟的沉积地层向海迁移的有趣的可能性。一个制度（特点是流体清新和甲烷和更高的碳氢化合物的存在）是由流体从俯冲沉积物和向上倾斜迁移通过高渗透性的地层俯冲输入驱逐驱动。另一种流态（其特征是深部存在硫酸盐）是由类似海水的流体通过上大洋地壳迁移到上覆沉积物的砂岩浊积岩中所驱动的。在两种流体状态的界面处，微生物活动似乎受到了刺激;在大约417 mbsf处新发现了甲烷活性厌氧氧化（AOM）的深层区，其中甲烷峰值浓度与硫酸盐的完全消耗和孔隙水硫化物的显着增加相一致。在此，我们建议：1）在与其他船上科学家的合作项目中，使用孔隙水数据来描述这些流动状态的性质; 2）通过分析自生相（碳酸盐和重晶石）来推断这些发现的时间，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（聚集氧同位素）的记录。最近开发的聚集氧同位素（即多取代同位素体）分析已被证明可以有效地将结晶温度限制在± 2.4 °C。对选定的碳酸盐岩脉和在孔底附近回收的水泥进行测量，将提供所需的流体温度的关键数据，以表征：进入沉积物的状态特性;温度依赖的成岩反应;和地下微生物群落。实验期间未收集原位温度数据。322.除了提供传入板块下部地层的基本地球化学信息（实验的一个关键目标）外，322），这里产生的数据集将用于进一步我们对新假设的和非常重要的主题的理解：1）传入板块下部地层中流动的历史和性质，其中可能包括上洋壳中的流体流动状态（迄今尚未记录）;（2）深部生物圈过程，包括新发现的AOM带，它是由上基底含硫酸盐流体提供的电子受体维持的。更广泛的影响：我们将收集的数据集将使我们能够提供关于流体对俯冲地层中地球化学、地质力学和地球生物学过程的作用的基本信息，这是考察的一个关键目标。我们的数据将与其他NantroSeize科学家共享，完全整合和合作。除了这些合作，Peckman教授（U。的不莱梅）已同意分析碳酸盐中的生物标志物，而无需为此提议支付任何费用。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。外联工作包括通过俄勒冈州州立大学的SMILE方案（http：//smile.oregonstate.edu/）、整个俄勒冈州的成人教育（http：//literacyworks.org/ocean/）传播地震带进程，以及通过亚利桑那州教育部的数学-科学伙伴关系方案为在职教师提供专业发展课程。