Collaborative Research: Characterization of Subduction Channel Processes - Borehole Sampling at Active Serpentinite Mud Volcanoes on the Mariana Forearc

合作研究：俯冲通道过程的表征 - 马里亚纳弧前活跃蛇纹岩泥火山的钻孔采样

• 批准号: 1921654
• 负责人: Susan Lang
• 金额: $ 26.97万
• 依托单位: University of South Carolina at Columbia
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2022-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1921654&HistoricalAwards=false
• 关键词: Collaborative; Research; Characterization; Subduction; Channel

The Mariana Trench is the deepest location on Earth, resulting from the subduction of the Pacific Plate under the Philippine Plate. Fluids that were trapped in the pores and minerals of the Pacific Plate are liberated during this subduction. These fluids react with rock in the overriding Philippine Plate to produce a slurry of mud and fluids that are very alkaline (with a pH up to 12.5, more alkaline than Clorox), yet support microbial life that thrives in such extreme environments. The discharge produces the largest mud volcanoes on Earth, some spanning 50 km in diameter and several kilometers in height. Probing the mud volcanoes by sampling fluids from boreholes drilling into them, provides the means to examine processes that occur at depth during subduction. The subduction zone environment is the epicenter for most large earthquakes on Earth, and the fluids that flow through subduction zones can be connected with that earthquake generation. Moreover, the reactions that occur to produce the fluids provide energy that can support a wide variety of microbes, a subseafloor biosphere that is present throughout what has been referred to broadly as a "deep crustal aquifer".The research team proposes to the sample fluids and dissolved gases from this ascending slurry in three mud volcanoes that tap different pressure (depths ranging from 10 to 20 km) and temperature conditions at depth. These ascending fluids discharge from scientific boreholes that were emplaced during International Ocean Discovery Program (IODP) Expedition 366. Prior to sampling these fluids, CORK-Lite instruments will be deployed to enable sampling operations. This infrastructure will also provide for a range of potential experimentation and monitoring efforts that can be used in the future. Specifically, the project will: (i) design, fabricate, and deploy CORK-Lites, (ii) sample discharging fluids with gas-tight and large volume sampling systems, (iii) analyze collected fluids for a range of solutes, dissolved gases, and isotopes, and (iv) measure borehole pressure and fluid discharge rates. The CORK-Lites will be sealed at the end of the field program for future experimentation and monitoring efforts. Results from this effort will test a model of abiotic methane formation, constrain the extent of serpentinization during the initial stages of subduction, set limits on potential microbial metabolic capabilities, and resolve water-rock reactions and solute sources.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

马里亚纳海沟是地球上最深的地方，是太平洋板块俯冲到菲律宾板块之下形成的。被困在太平洋板块孔隙和矿物质中的流体在这次俯冲过程中被释放出来。这些液体与菲律宾板块上层的岩石发生反应，产生泥浆和强碱性液体（pH 值高达 12.5，比 Clorox 更碱性），但仍支持微生物在如此极端的环境中繁衍生息。喷发产生了地球上最大的泥火山，有些火山直径达 50 公里，高度达数公里。通过从钻孔中取样流体来探测泥火山，提供了检查俯冲过程中在深处发生的过程的方法。俯冲带环境是地球上大多数大地震的震中，流经俯冲带的流体可以与地震的产生有关。此外，产生流体的反应提供了可以支持多种微生物的能量，这是一种存在于广泛称为“深层地壳含水层”的海底生物圈。研究小组建议对流体进行采样以及三座泥火山中上升浆液中溶解的气体，这些泥火山的深度不同，压力（深度范围从 10 到 20 公里）和温度条件不同。这些上升流体从国际海洋发现计划 (IODP) 第 366 次探险期间设置的科学钻孔中排出。在对这些流体进行采样之前，将部署 CORK-Lite 仪器以进行采样操作。该基础设施还将提供一系列未来可使用的潜在实验和监测工作。具体来说，该项目将：(i) 设计、制造和部署 CORK-Lites，(ii) 使用气密和大容量采样系统对排放流体进行采样，(iii) 分析收集的流体中的一系列溶质、溶解气体、和同位素，以及 (iv) 测量井眼压力和流体排放速率。 CORK-Lites 将在现场计划结束时密封，用于未来的实验和监测工作。这项工作的结果将测试非生物甲烷形成的模型，限制俯冲初始阶段蛇纹石化的程度，限制潜在的微生物代谢能力，并解决水岩反应和溶质来源。该奖项反映了 NSF 的法定使命和通过使用基金会的智力优点和更广泛的影响审查标准进行评估，该项目被认为值得支持。