Collaborative Research: Deformation-induced Hydration of Peridotite Mylonites in Nature and Experiments

对海洋断裂带的研究表明，流体循环可能导致这些断裂带浅层脆性部分的弱化和地震破坏。一般认为，当岩石从脆性破坏（断层）向塑性流动（糜棱岩）转变时，流体循环就结束了。然而，最近对海洋橄榄岩糜棱岩的分析揭示了普遍存在的含水矿物相。该项目评估了海洋断裂带中水通过脆性-韧性转变的循环程度，地震事件中裂缝的扩展可以将水向下输送到糜棱岩带。在这个项目中，橄榄岩糜棱岩分析了两个互补环境中的剪切带，圣保罗？大西洋中脊的岩石和新喀里多尼亚蛇绿岩。本研究使用的方法包括实地考察、微观结构分析、稳定同位素测量和矿物温度测量。此外，通过室内岩石变形实验，研究了流体包裹体在变形过程中的行为，水反应形成含水矿物的化学环境，以及这些含水相对弱化地幔岩石的影响，从而局部化变形。板块构造使水从水圈循环到深部地幔。俯冲的海洋板块把水推到几百公里深的地方，火山活动又把水带回地球。年代的表面。这项研究的重点是水是如何融入大洋中脊海底下的岩石的，在那里，伸展和转换断层与浅层岩浆的加热结合在一起，驱动海水循环。断层作用为水流创造了通道：在地震周期中，裂缝传播到断层带的较深处，使水能够穿透岩石通常发生塑性变形的区域。随着时间的推移，这些裂缝愈合，液体被困在大量的流体包裹体中。该项目研究了这些流体包裹体在长期变形过程中的命运，以及与地幔岩石形成含水矿物的化学反应，这些含水矿物充当富水物质的胶囊。当板块最终进入俯冲带时，这些水将可用于全球循环。这项研究的结果涉及到与水在地球过程中的作用有关的学科，包括地震学、岩石学和地球化学、构造学和地球动力学。拟议的研究将通过以下方式促进预期的社会成果：1)女性充分参与STEM；2)通过对研究生的培训和对本科生的延伸努力，发展具有竞争力的STEM劳动力；3)通过与新喀里多尼亚地质学家的合作和向新喀里多尼亚社区的公众宣传，加强国际伙伴关系。

Studies of oceanic fault zones have shown that fluid circulation may drive weakening and seismic failure in the shallow brittle part of these faults. It is generally assumed that fluid circulation ends when rocks transition from brittle failure (fault) to plastic flow (mylonite). However, recent analysis of oceanic peridotite mylonites has revealed the ubiquitous presence of hydrous mineral phases. This project assesses the degree to which water circulates though the brittle-ductile transition in oceanic fault zones, where fracture propagation during seismic events can send water downward into mylonite zones. In this project, peridotite mylonites are analyzed from shear zones in two complementary settings, the St. Paul?s Rocks on the Mid-Atlantic Ridge and the New Caledonia ophiolite. Methods used in this research include fieldwork, microstructural analysis, stable isotope measurements, and mineral thermometry. In addition, laboratory rock deformation experiments are used to investigate the behavior of fluid inclusions during deformation, the chemical environment in which water reacts to form hydrous minerals, and the influence these hydrous phases have in weakening mantle rocks and therefore localizing deformation.Plate tectonics cycles water from the hydrosphere to the deep mantle. Subducted oceanic plates drive water to several hundred kilometers depth, and volcanism brings it back to the Earth?s surface. This research focuses on how water is incorporated into rocks beneath the ocean floor at mid-ocean ridges, where extension and transform faulting combine with heating from shallow magma to drive seawater circulation. Faulting creates pathways for water flow: during a seismic cycle, fractures propagate to the deeper part of fault zones, allowing water to penetrate the region where rocks normally deform plastically. These fractures heal over time and the fluids are trapped as numerous fluid inclusions. This project investigates the fate of these fluid inclusions during long-term deformation and chemical reaction with mantle rocks to form hydrous minerals, which act as capsules of water-rich material. When the plate eventually dives into a subduction zone, this water will be available for global circulation. Results of this research are relevant to disciplines that are concerned with the role of water in Earth processes, including seismology, petrology and geochemistry, tectonics, and geodynamics. The proposed study would advance desired societal outcomes through: 1) full participation of women in STEM; 2) development of a competitive STEM workforce through training of graduate students and in-reach efforts to undergraduate students; and 3) increased international partnerships through collaboration with New Caledonian geologists and public outreach to New Caledonian communities.