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。被困在太平洋板块孔隙中的流体和矿物质在这次俯冲过程中被释放出来。这些流体与覆盖菲律宾板块的岩石发生反应，产生一种泥浆和液体，这种泥浆和液体非常碱性（pH值高达12.5，比高乐氏碱性更高），但却支持微生物在这种极端环境中茁壮成长。这一喷发形成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。对泥火山进行探测，从钻孔中提取流体样本，为研究俯冲过程中发生的深层过程提供了手段。俯冲带环境是地球上大多数大地震的震中，而流经俯冲带的流体可以与地震的发生联系起来。此外，为产生流体而发生的反应提供了能量，可以支持各种各样的微生物，这是一个海底生物圈，遍布于被广泛称为“深地壳含水层”的地方。研究小组建议将这些上升的泥浆中的液体和溶解气体取样到三座泥火山中，这些火山利用不同的压力（深度从10到20公里不等）和深度的温度条件。这些上升的液体是从国际海洋发现计划（IODP） 366号探险期间放置的科学钻孔中排放出来的。在对这些流体进行取样之前，将部署CORK-Lite仪器进行取样操作。该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）使用气密和大容量取样系统对排出流体进行取样，（iii）分析收集到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出速率。CORK-Lites将在现场项目结束时密封，用于未来的实验和监测工作。这项工作的结果将测试一种非生物甲烷形成模型，限制俯冲初期蛇纹岩化的程度，限制潜在的微生物代谢能力，并解决水岩反应和溶质来源问题。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.