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

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的结果。被困在太平洋板块的孔隙和矿物中的流体在俯冲过程中被释放出来。这些流体与菲律宾板块上的岩石发生反应，产生一种非常碱性的泥浆和流体（pH值高达12.5，比Clorox碱性更强），但支持在这种极端环境中蓬勃发展的微生物生命。这种喷发产生了地球上最大的泥火山，有些直径达50公里，高度达几公里。通过从钻孔中采集流体样本来探测泥火山，提供了研究俯冲过程中发生的深度过程的方法。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发生有关。此外，产生流体的反应提供了可以支持各种微生物的能量，这是一个海底下的生物圈，存在于被广泛称为“深层地壳含水层”的地方。研究小组建议在三个不同压力的泥火山中对这种上升的泥浆中的液体和溶解气体进行采样（深度10至20公里）和深度温度条件。这些上升的液体从国际海洋发现计划（IODP）366远征期间布设的科学钻孔中排出。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。这一基础设施还将提供一系列可在未来使用的潜在实验和监测工作。具体而言，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）测量钻孔压力和流体排放速率。CORK-Lites将在现场项目结束时密封，以便将来进行实验和监测工作。这项工作的结果将测试一个非生物甲烷形成的模型，限制在俯冲的初始阶段蛇纹石化的程度，对潜在的微生物代谢能力设置限制，并解决水岩反应和溶质来源。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.