Collaborative Research: Chemical, pressure, temperature, and flow constraints on hydrologic horizons in the Costa Rica Subduction zone, ODP Sites 1253 and 1255

合作研究：哥斯达黎加俯冲带水文层的化学、压力、温度和流量限制，ODP 站点 1253 和 1255

• 批准号: 0825145
• 负责人: Miriam Kastner
• 金额: --
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-15 至 2013-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0825145&HistoricalAwards=false
• 关键词: Collaborative; Research; Chemical; pressure; temperature

During Leg 205 of the Ocean Drilling Program (ODP) two boreholes were drilled into active hydrologic formations on the Costa Rica margin west of the Nicoya Peninsula. One borehole penetrated through the overriding plate into the décollement at ODP Site 1255. The other borehole penetrated through the subducting sediment section and plate into permeable igneous basement at ODP Site 1253. These two boreholes were sealed and instrumented with a borehole observatory (CORK), allowing pressure, temperature, fluid flow velocity, and fluid chemical composition to be measured within the formation. The 1.5-yr pressure and two-year temperature, fluid velocity, and fluid chemical composition records collected to date have provided a basic knowledge of formation properties, although fluids within the boreholes had yet to reach steady state with the surrounding formations. The data also provide evidence that tectonic forcing related to subduction results in measurable transients in pressure, temperature, fluid velocity, and fluid composition within the décollement. While the initial data provide a baseline for approaching several important scientific and technical questions, they have raised new key questions that will be addressed from additional continuous borehole data. The investigators will a 6-day submersible operation to retrieve instruments and stored data that will provide a continuous record of formation temperature, pressure, fluid flow rate, and chemical composition for an additional five years, from the time of the last visit in 2004 to 2009. This project will result in an extremely valuable long-term synchronous record of hydrologic, geochemical, and geodynamic activity at this subduction zone, and establish a technical and scientific foundation for future borehole studies in a broad range of tectonically and hydrologically active settings.

在大洋钻探计划第205航次期间，在尼科亚半岛以西的哥斯达黎加边缘的活跃水文地层中钻了两个井眼。一个钻孔穿透覆盖板块进入ODP站点1255的滑脱层。另一个钻孔穿透俯冲沉积物段和板块，进入ODP站点1253的可渗透火成岩基底。这两个钻孔被密封，并装有钻孔观测台（CORK），允许测量地层内的压力、温度、流体流速和流体化学成分。迄今为止收集的1.5年压力和两年温度、流体速度和流体化学成分记录提供了地层性质的基本知识，尽管钻孔内的流体尚未与周围地层达到稳定状态。这些数据还提供了证据表明，与俯冲作用有关的构造作用力导致了滑脱层内压力、温度、流体速度和流体成分的可测量瞬变。虽然最初的数据为处理几个重要的科学和技术问题提供了一个基线，但它们也提出了新的关键问题，这些问题将从更多的连续钻孔数据中得到解决。调查人员将进行为期6天的潜水作业，以取回仪器和存储的数据，这些数据将提供从2004年到2009年的最后一次访问的连续五年的地层温度，压力，流体流速和化学成分记录。该项目将在这一俯冲带获得极其宝贵的水文、地球化学和地球动力学活动的长期同步记录，并为今后在广泛的构造和水文活动背景下进行钻孔研究奠定技术和科学基础。