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

合作研究：自然界和实验中橄榄岩糜棱岩变形引起的水化

基本信息

批准号：
1619880
负责人：
Jessica Warren
金额：
$ 18.06万
依托单位：
University of Delaware
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2015
资助国家：
美国
起止时间：
2015-10-01 至 2018-03-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1619880&HistoricalAwards=false
关键词：
Collaborative Research Deformation induced Hydration

项目摘要

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.

对海洋断层区域的研究表明，流体循环可能会导致这些断层的浅脆性部分削弱和地震衰竭。通常认为，当岩石从脆性故障（断层）到塑料流量（肌lon虫）过渡时，流体循环结束。然而，最近对海洋橄榄岩肌lon虫的分析表明，遗传矿物相无处不在。该项目评估了水在海洋断层区的脆性延性过渡时循环的程度，在地震事件期间裂缝传播可以使水向下延伸到肌隆区。在这个项目中，在两个互补环境中的剪力区域分析了橄榄岩甲状腺藻，分析了中大西洋山脊上的圣保罗岩石和新的喀里多尼亚ophiolite。这项研究中使用的方法包括现场工作，微结构分析，稳定的同位素测量和矿物质温度法。此外，实验室岩石变形实验用于研究变形过程中流体夹杂物的行为，水反应形成液压矿物质的化学环境以及这些液压相在弱化地幔岩石中具有的影响。俯冲的海洋板将水驱动到几百公里的深度，而火山将其带回地球表面。这项研究的重点是如何将水掺入中山脊的海底下方的岩石中，在那里延伸和转化断层与从浅层岩浆到驱动海水循环的加热结合在一起。断层创造水流的途径：在地震循环期间，断裂式向上延伸到断层区域的更深部分，使水可以穿透岩石通常塑性变形的区域。这些裂缝会随着时间的流逝而愈合，流体被困为许多流体夹杂物。该项目调查了这些流体夹杂物在长期变形和与地幔岩石岩石化学反应过程中形成含水矿物的命运，这些矿物是富含水的材料的胶囊。当板最终进入俯冲带时，该水将用于全球循环。这项研究的结果与与水在地球过程中的作用有关的学科有关，包括地震学，岩石学和地球化学，构造和地球动力学。拟议的研究将通过：1）妇女在STEM中的全面参与来提高所需的社会成果； 2）通过培训研究生的培训和本科生的范围努力来发展竞争性的STEM劳动力； 3）通过与新喀里多尼亚地质学家的合作以及与新喀里多尼亚社区的公众宣传来增加国际伙伴关系。