Collaborative Research: Rodingites as Recorders of Tectonic Processes from the Seafloor to Convergence: A case study of the Dun Mountain Ophiolite Belt

合作研究：罗丁岩作为从海底到聚合的构造过程的记录者：以敦山蛇绿岩带为例

• 批准号: 2147571
• 负责人: Michelle Gevedon
• 金额: $ 9.4万
• 依托单位: Colorado College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-15 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2147571&HistoricalAwards=false
• 关键词: Collaborative; Research; Rodingites; Recorders; Tectonic

The hydration of ultramafic rock (called serpentinization) is a fundamental Earth process that influences the rheology of materials and thus how rocks deform, localize strain, and behave seismically. In addition, serpentinization affects geochemical cycling of key elements such as hydrogen, carbon, and sulfur and therefore influenced the evolution of life. Serpentinization is a widespread process most common at the boundaries of tectonic plates. By understanding the conditions (pressure, temperature, deformation, fluid source) and timing of serpentinization, one can place constraints on major tectonic processes occurring at plate boundaries, such as continental rifting, seafloor spreading, subduction, and strain-localization along strike-slip faults. Unfortunately, determining the pressure-temperature-deformation-fluid-time (P-T-d-f-t) histories of serpentinites themselves has long been challenging; therefore the team will determine the P-T-d-f-t histories of rodingites, rocks associated with serpentinites, as a proxy to place constraints on the timing and conditions of serpentinization in order to interpret the tectonic evolution of plate boundaries. This multi-disciplinary project invokes a tiered mentorship structure from full professors to assistant professors to graduate and undergraduate students. This work will support student education and scientific training by partial funding of multiple students at the graduate (Ph.D. and M.S.) and undergraduate levels, as well as a minority student summer internship program. The research team will determine the conditions and timing of rodingitization (and associated serpentinization) of the Dun Mountain Ophiolite Belt in the Nelson region of New Zealand to place constraints on the tectonic evolution of the ophiolite. Despite New Zealand being the type locality of rodingites, limited work has focused on their tectonic setting of formation with interpretations ranging from formation on the seafloor to post-emplacement on land due to either crustal fluids or fluid focusing along late faults. The team will test the hypothesis that the rodingites from the Dun Mountain Ophiolite formed during seafloor hydrothermal alteration or in the overlying forearc mantle wedge during the mid-Permian. In contrast, the rodingites from associated serpentinite mélanges formed during subduction and/or exhumation via interaction with slab-derived fluids along the plate interface and will be of slightly younger age. The team will also test the hypothesis that minimal rodingitization occurred post-emplacement. They will determine the conditions and timing of rodingitization of the Dun Mountain Ophiolite Belt by using phase equilibria modeling to determine the P-T conditions of rodingitization, combined with the new and novel techniques of U-Pb geochronology and Ca and Sr isotope composition of andradite garnet in the rodingites to determine the timing of and fluid source responsible for rodingitization, respectively. Field structural and microstructural data will help in evaluation of timing of rodingitization, particularly with multiple generations of rodingites related to different tectonic fabrics (e.g., preservation of undeformed igneous textures; penetrating fabric within both the rodingite and host serpentinite). As the applications to U-Pb geochronology and Ca and Sr isotope composition to rodingites are limited, the team will first reconstruct the tectonic histories from well-known localities on the seafloor (fast-spreading ridge and passive rifted margin) and in the Western Alps (exhumed subducted metamorphic terrane) to provide proof of concept. They will then determine when rodingitization within the Dun Mountain Ophiolite Belt occurred and how these metasomatic event(s) record the tectonic history of the Dun Mountain Ophiolite Belt.Funding for this project is provided by NSF EAR Tectonics and OCE Marine Geology and Geophysics Programs.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.

超镁铁质岩石的水化（称为蛇纹石化）是地球的一个基本过程，它影响材料的流变性，从而影响岩石的变形、局部应变和地震行为。此外，蛇纹石化影响氢、碳和硫等关键元素的地球化学循环，从而影响生命的进化。蛇纹石化是一个广泛的过程，最常见于构造板块的边界。通过了解蛇纹石化的条件（压力、温度、变形、流体来源）和时间，人们可以对板块边界发生的主要构造过程施加限制，例如大陆裂谷、海底扩张、俯冲和沿走滑断层的应变局部化。不幸的是，确定蛇纹岩本身的压力-温度-变形-流体-时间（P-T-d-f-t）历史长期以来一直具有挑战性。因此，该团队将确定罗丁岩（与蛇纹岩有关的岩石）的 P-T-d-f-t 历史，作为对蛇纹石化时间和条件施加限制的代理，以解释板块边界的构造演化。这个多学科项目采用了从正教授到助理教授再到研究生和本科生的分层指导结构。这项工作将通过为研究生（博士和硕士）和本科生以及少数族裔学生暑期实习计划提供部分资助来支持学生教育和科学培训。研究小组将确定新西兰尼尔森地区敦山蛇绿岩带的罗金石化（以及相关的蛇纹石化）的条件和时间，以限制蛇绿岩的构造演化。尽管新西兰是罗丁岩的典型产地，但有限的工作集中在其形成的构造环境上，解释范围从海底的形成到由于地壳流体或沿晚期断层聚集的流体而在陆地上的形成。研究小组将验证这样的假设：来自敦山蛇绿岩的罗丁岩是在二叠纪中期海底热液蚀变期间或上覆的弧前地幔楔中形成的。相比之下，来自相关蛇纹岩混杂岩的罗丁岩是在俯冲和/或折返过程中通过与板块界面上的板片衍生流体相互作用而形成的，并且年龄稍年轻。该团队还将测试安置后发生最小程度的罗金吉特化的假设。他们将利用相平衡模型确定罗金石化的P-T条件，结合U-Pb年代学和罗金石中Ca、Sr同位素组成等新技术，分别确定罗金石化的时间和流体来源，从而确定盾山蛇绿岩带的罗金石化的条件和时间。现场结构和微观结构数据将有助于评估罗丁岩化的时间，特别是与不同构造织物相关的多代罗丁岩（例如，保存未变形的火成岩纹理；罗丁岩和宿主蛇纹岩内的穿透织物）。由于U-Pb地质年代学以及Ca和Sr同位素组成在罗丁岩中的应用有限，该团队将首先重建海底（快速扩张的海脊和被动裂谷边缘）和西阿尔卑斯山（挖出的俯冲变质地体）的著名地点的构造历史，以提供概念证明。然后，他们将确定敦山蛇绿岩带内的罗金化作用何时发生，以及这些交代事件如何记录敦山蛇绿岩带的构造历史。该项目的资金由 NSF EAR Tectonics 和 OCE 海洋地质和地球物理项目提供。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进行评估，认为值得支持。 审查标准。