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.

洋壳是在洋中脊形成的，因为岩浆从地幔中上升并冷却。为了冷却这种熔化，海水渗透到海洋地壳中，导致地壳岩石和海洋发生许多化学变化。因此，“热液”流体流动是地球深部与海洋之间物质和热量转移的主要机制，约占全球每年热量损失的三分之一。特别令人感兴趣的是热液系统，这些热液系统是从更深的地幔中产生的，由于其成分而被称为“超镁铁质”岩石。这是因为：（1）产生这种地幔暴露的机制尚未完全了解;（2）这些超镁铁岩有可能封存二氧化碳;（3）超镁铁岩水合作用产生的流体可以创造对地球上的生物非常重要的独特化学环境。该项目将利用2013年获得的现有数据集，探测大西洋中脊沿着活跃热液系统下这种超镁铁质暴露的地下情况。该项目将通过促进科学进步，特别是通过调查地幔岩石，流体和（次）表面生态系统之间的联系和相互作用，为国家利益服务。这是地球科学界的一个主要科学目标，其重要性在为科学家、资助机构和决策者提供指导的科学计划中得到了强调，如《2013-2023年国际海洋发展方案科学计划》或《国家科学院海洋变化2015-2025年海洋科学十年调查报告》。该项目将支持博士后研究员，为发展独立科学家的早期职业生涯提供机会，并为新一代具有先进地震成像技术专业知识的地球科学家做出贡献。这些专业知识对美国自然资源勘探和生产领域的工业非常重要。通过利用现有的地震数据集，该项目还将利用NSF以前在海洋地震采集方面的投资。该项目将对2013年收集的一部分地震数据进行多尺度高级地震建模和成像研究。这些数据是作为NSF资助的MARINER实验的一部分收集的，该实验位于大西洋中脊的彩虹海脊。该数据集包括有源长拖缆地震反射数据、海底地震仪广角数据和微震活动目录。该方法将包括：（1）向下延拓和走时层析成像，产生P波速度结构的中等分辨率模型;（2）弹性全波形反演，产生P波速度结构的高分辨率模型;（3）逆时偏移，产生几何精确的高保真地震反射图像;（4）微地震层析成像，建立了千米尺度的区域性三维S波速度结构模型。这些模型和图像将用于研究洋壳内岩浆岩的物理特性。它们将有助于量化它们的部分熔融或固化状态，以及它们如何与活跃和不活跃的热液场联系在一起。此外，这些模型和图像将阐明流体通道和小规模断层，可能将海底热液场与深部岩浆系统连接起来。当与现有的海底地质观测结果联合解释时，先前研究的海底采样和近底图像将全面了解岩浆作用和其他地质控制对地幔暴露沿着中部地区热液活动的作用该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和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.