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

超镁铁岩的水合作用（称为蛇纹石化）是一个基本的地球过程，它影响着物质的流变学，从而影响着岩石的变形、应变局部化和地震行为。此外，蛇纹岩化还影响了氢、碳、硫等关键元素的地球化学循环，从而影响了生命的演化。蛇纹石化是一种广泛的过程，最常见于构造板块的边界。通过了解蛇纹岩化的条件（压力、温度、变形、流体来源）和时间，人们可以限制发生在板块边界的主要构造过程，如大陆裂谷、海底扩张、俯冲和沿着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，该团队将确定与蛇纹岩有关的岩石的P-T-d-f-t历史，作为对蛇纹岩化的时间和条件进行限制的代理，以解释板块边界的构造演化。这个多学科的项目调用了一个分层的导师结构，从正教授到助理教授，再到研究生和本科生。这项工作将通过部分资助研究生（博士）的多名学生来支持学生教育和科学培训。和MS）和本科水平，以及少数民族学生暑期实习计划。研究小组将确定新西兰纳尔逊地区敦山蛇绿岩带的rodingitization（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rodingites的典型产地，但有限的工作集中在其形成的构造背景上，解释范围从海底形成到陆地上的就位后，由于地壳流体或流体沿沿着晚期断层聚集。研究小组将检验这一假设，即来自敦山蛇绿岩的罗丁岩是在海底热液蚀变过程中形成的，或者是在二叠纪中期的弧前地幔楔中形成的。相比之下，在俯冲和/或折返过程中，通过与板片衍生流体沿着板块界面相互作用，形成了伴生蛇纹岩混杂岩中的杆柱岩，其年龄略年轻。该小组将检验这一假设，即最低限度的rodingitization发生后，安置。利用相平衡模拟确定蛇绿岩带中蛇绿岩化的P-T条件，结合U-Pb年代学和钙锶同位素组成等新技术，确定蛇绿岩带中蛇绿岩化的时间和流体来源，从而确定蛇绿岩带中蛇绿岩化的条件和时间。野外构造和显微构造数据将有助于评估rodingitization的时间，特别是与不同构造组构相关的多代rodingites（例如，保留未变形的火成岩结构;在杆柱岩和寄主蛇纹岩中渗透组构）。由于U-Pb地质年代学以及钙和锶同位素组成对罗丁岩的应用有限，研究小组将首先重建海底（快速扩张脊和被动裂谷边缘）和西阿尔卑斯山（折返俯冲变质岩）著名地点的构造历史，以提供概念证明。从而确定敦山蛇绿岩带内的rodingitization何时发生以及这些交代事件是如何发生的记录敦山蛇绿岩带的构造历史。该项目的资金由NSF地质构造学和OCE海洋地质与地球物理计划提供。该奖项反映了NSF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进行评估，被认为值得支持审查标准。

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 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.