Study of Magmatic and Hydrothermal Processes in an Ultramafic Setting (Rainbow, Mid-Atlantic Ridge) Using Advanced Seismic Modeling and Imaging

使用先进的地震建模和成像研究超镁铁质环境（彩虹、大西洋中脊）中的岩浆和热液过程

• 批准号: 2001012
• 负责人: Juan Pablo Canales
• 金额: $ 39.82万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-01 至 2023-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2001012&HistoricalAwards=false
• 关键词: Study; Magmatic; Hydrothermal; Processes; Ultramafic

The ocean crust is created at Mid-Ocean Ridges as magmas rise from the mantle and cool. In order to cool this melt, seawater penetrates the ocean crust, resulting in many chemical changes of both the rocks of the crust as well as the oceans. Thus, “hydrothermal” fluid flow is a primary mechanism for mass and heat transfer between the deep Earth and the oceans, accounting for approximately one third of the global yearly heat loss. Of particular interest are hydrothermal systems hosted in rocks that were brought up from the deeper mantle, so-called “ultramafic” rocks due to their composition. This is because: (1) the mechanisms that produce such mantle exposures are not fully understood; (2) there is potential for these ultramafic rocks to sequester CO2 sequestration; and (3) the fluids resulting from hydration of ultramafic rocks can create unique chemical environments that are important for biology on earth. This project will use an existing dataset acquired in 2013 that probes the subsurface of such an ultramafic exposure beneath an active hydrothermal system along the Mid-Atlantic Ridge. This project will serve the national interest by promoting the progress of science, in particular by investigating the linkages and interactions between mantle rocks, fluids, and (sub)surface ecosystems. This is a major scientific goal of the geoscience community and its importance has been highlighted in science plans providing guidance to scientists, funding agencies and policy makers, such as the IODP Science Plan for 2013-2023 or The National Academy of Sciences Sea Change 2015-2025 Decadal Survey of Ocean Sciences Report. This project will support a postdoctoral investigator, providing an opportunity for developing the early career of an independent scientist, and contributing to the new generation of geoscientists with expertise in advanced seismic imaging techniques. Such expertise is of great importance for the US industries in the field of exploration and production of natural resources. By making use of existing seismic datasets, this project will also leverage previous NSF investments in marine seismic acquisition. This project will conduct a multi-scale advanced seismic modeling and imaging study of a subset of a seismic data collected in 2013. These data were collected as part of the NSF-funded MARINER experiment in the Rainbow massif of the Mid-Atlantic Ridge. The dataset includes active-source long-streamer seismic reflection data, ocean bottom seismometer wide-angle data, and a microseismicity catalog. The approach will consist of (1) downward continuation and travel-time tomography, yielding intermediate resolution models of the P-wave velocity structure; (2) elastic full waveform inversion, yielding high-resolution models of the P-wave velocity structure; (3) reverse time migration, yielding geometrically accurate, high fidelity seismic reflection images; and (4) micro-earthquake tomography, yielding a km-scale regional 3-D model of the S-wave velocity structure. These models and images will be used to investigate the physical properties of magmatic rocks within the oceanic crust. They will help to quantify their partially molten or solidified state, and how they are linked to active and inactive hydrothermal fields. Furthermore, the models and images will illuminate fluid pathways and small-scale faulting, potential connecting the seafloor hydrothermal fields to the magmatic system at depth. The results, when jointly interpreted with existing seafloor geology observations, seafloor sampling and near-bottom imagery from previous studies will provide a comprehensive understanding of the role of magmatism and other geological controls on hydrothermal activity in regions of mantle exposures along mid-ocean ridges.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.

当岩浆从地幔升起并凉爽时，海层是在海脊中产生的。为了冷却这种熔体，海水穿透了海皮，从而导致了地壳的岩石和海洋的许多化学变化。这是“热液”流体流量是深层和海洋之间质量和传热的主要机制，约占全球年度热量损失的三分之一。特别令人感兴趣的是托管在岩石中的水热系统，这些岩石是由于其组成而从更深的地幔，所谓的“超镁铁质”岩石中提出的。这是因为：（1）尚未完全了解产生这种地幔暴露的机制； （2）这些超镁铁质岩石有可能隔离二氧化碳的隔离； （3）超镁铁质岩石水合产生的流体可能会产生独特的化学环境，这对于地球上的生物学很重要。该项目将使用2013年获得的现有数据集，该数据集探测了大西洋山脊沿着主动的热液系统下方的这种超光接触的地下。该项目将通过促进科学的进步，特别是通过研究地幔岩石，流体和（子）表面生态系统之间的联系和相互作用来实现国家利益。这是地球科学界的一个主要科学目标，其重要性在科学计划中得到了强调，为科学家，资助机构和政策制定者提供指导，例如2013 - 2023年的IODP科学计划或国家科学院Sea Change of Sea Change Academy Sea Change 2015 - 2025年2015-2025 decadal comession of Ocean Sciences报告。该项目将支持一名博士后研究者，为发展独立科学家的早期职业提供了机会，并为具有高级地震成像技术专业知识的新一代地球科学家做出了贡献。这种专业知识对于探索和生产自然资源领域的美国行业至关重要。通过利用现有的地震数据集，该项目还将利用以前的NSF投资于海洋地震收购。该项目将对2013年收集的地震数据的子集进行多尺度的先进地震建模和成像研究。这些数据是在大西洋山脊的彩虹弥撒中收集的，作为NSF资助的水手实验的一部分。该数据集包括主动源长流程震荡反射数据，海洋底部地震仪广角数据和微作用目录。该方法将包括（1）向下延续和旅行时间断层扫描，得出P波速度结构的中间分辨率模型； （2）弹性全波形反演，得出P波速度结构的高分辨率模型； （3）反向迁移，产生几何准确的高保真地震反射图像； （4）微电子断层扫描，得出S波速度结构的KM尺度区域3-D模型。这些模型和图像将用于研究海洋壳中岩浆岩石的物理特性。它们将有助于量化其部分熔融或固化状态，以及如何与活性和不活跃的热液场相关联。此外，模型和图像将照亮流体通路和小规模断层，潜在的潜力将海底热液场连接到深度的岩浆系统。结果，当与现有的海底地质观察共同解释时，先前研究的海底取样和近底图像将对岩浆主义和其他地质控制对沿着地幔式曝光的地区的水热区域的作用进行全面了解。更广泛的影响审查标准。

项目成果

Seismic imaging of magma sills beneath an ultramafic-hosted hydrothermal system

• DOI: 10.1130/g38795.1
• 发表时间: 2017-05-01
• 期刊: GEOLOGY
• 影响因子: 5.8
• 作者: Canales, J. Pablo;Dunn, Robert A.;Sohn, Robert A.
• 通讯作者: Sohn, Robert A.