OCE-PRF: Determining the depth of fluid infiltration in slow and ultra-slow spread oceanic crust

该奖项全部或部分由2021年美国救援计划法案（公法117-2）资助。Benjamin Urann博士已被授予NSF OCE PRF，与怀俄明州大学地质地球物理系的Barbara John和J. Michael Cheadle博士一起工作。该项目的目标是评估海水渗透海洋地壳的深度，以及海水渗透深度是否随不同海洋盆地的构造板块扩张速度而变化。 研究产品将促进对地球系统过程的更深入了解，包括俯冲和水圈与地球深部之间的相互作用。此外，这项工作将有助于限制深海地壳微生物生命的可居住性，因为微生物生命依赖于循环热液流体提供有机和无机碳。科学宣传和教育将是该项目的一个中心宗旨，涉及：（1）与怀俄明州多样性，公平和包容办公室的外联活动，以促进代表性不足的群体的STEM和地球科学（2）社区讲座，在线和面对面，包括在风河印第安人保留区（3）创建怀俄明州地质博物馆关于海洋地壳生成的展览，深海断层使缓慢和超缓慢扩张海脊的广大海底（占全球所有扩张海脊的三分之一以上）的地幔橄榄岩和下地壳暴露出来。丰富的糜棱岩表明，这些断层必须根以下的地震活动区，但这些剪切带开始的深度仍然未知。这些断层充当流体通道，但对海水渗入地幔岩石圈的深度知之甚少。PI将调查来自几个洋中脊地区的一套岩石样本的地球化学和结构特征（大西洋中部、西南印度洋、开曼中部和加克尔岭）了解：（1）海水沿沿着断层侵入出露地幔橄榄岩的深度;（2）海水侵入深度随板块扩张速率的变化;（3）海水侵入对全球挥发分的影响（H_2 O，F，Cl，C）循环;（4）深海海水入侵对大洋地壳可居住性的影响。PI将通过二次离子质谱法测量挥发物丰度和B同位素，并结合岩石学和地球化学温压计以及相平衡建模来限制海水渗透深度。总之，这个项目将提供新的见解，岩石圈水圈相互作用，并把一些较低的界限上的可居住性深lithosepher.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Dr. Benjamin Urann has been granted an NSF OCE PRF to work alongside Drs. Barbara John and J. Michael Cheadle in the Dept of Geology & Geophysics at the University of Wyoming. The goal of this project is to evaluate the depth to which seawater penetrates ocean crust, and whether seawater penetration depth varies with tectonic plate spreading rates across different ocean basins. Research products will promote a deeper understanding of earth system processes including subduction and the interaction between the hydrosphere and deep Earth. In addition, this work will help to constrain the habitability of deep ocean crust for microbial life, which relies on delivery of organic and inorganic carbon by circulating hydrothermal fluids. Science outreach and education will be a central tenet of the project and involve: (1) outreach with UWyoming Office of Diversity, Equity and Inclusion to promote STEM and geoscience for underrepresented groups (2) community lectures, both online and in person, including at the Wind River Indian Reservation (3) creation of a UWyoming Geological Museum exhibit on the generation of ocean crust, hydrothermal vents and the biological diversity of the seafloor.Deep-seated faults expose mantle peridotite and lower crust across broad expanses of seafloor (more than one third of all spreading ridges globally) at slow and ultra-slow spreading ridges. Abundant mylonites suggest that these faults must root below regions of earthquake activity, however the depth at which these shear zones initiate remains unknown. These faults act as fluid conduits, yet little is known about the depth to which seawater infiltrates the mantle lithosphere. The PI will investigate the geochemical and textural characteristics of a suite of rock samples from several mid-ocean ridge localities (Mid-Atlantic, Southwest Indian, Mid-Cayman and Gakkel Ridges) to understand: (1) the depth to which seawater penetrates exposed mantle peridotite along faults, (2) if seawater penetration depth varies with plate spreading rate, (3) the effect of seawater intrusion on global volatile (H2O, F, Cl, C) cycles and (4) the implications of deep seawater intrusion on the habitability of deep ocean crust. The PI will measure volatile abundances and B isotopes by secondary ion mass spectrometry, in conjunction with petrologic and geochemical thermobarometers and phase equilibria modeling to constrain seawater penetration depths. Taken together, this project will provide novel insights into lithosphere-hydrosphere interaction and place some lower bounds on the habitability of the deep lithosphere.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.