CAREER: Rheological Evolution of Subduction Interface Shear Zones: Insights From Exhumed Subduction Complexes

职业：俯冲界面剪切带的流变演化：来自挖掘出的俯冲复合体的见解

• 批准号: 1555346
• 负责人: Jaime Barnes
• 金额: $ 19.9万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1555346&HistoricalAwards=false
• 关键词: CAREER; Rheological; Evolution; Subduction; Interface

Geophysical data from subduction zones worldwide illustrate that subduction interfaces are rheologically complex and heterogeneous. Observations of exhumed remnants of subduction interface shear zones yield fundamental insight into the processes that control this complexity. The scientific objective of this project is to systematically investigate the rheological properties and evolution of the subduction interface using exhumed rocks. Specifically, the project will investigate the heterogeneity of deformation within subduction interface shear zones and the nature of changes in deformational styles and mechanisms as rocks are progressively subducted to depth. The research component of this project will focus on three exhumed subduction shear zones that each record prograde deformation and that together represent a wide range of pressure-temperature conditions. The field sites include the: 1) Chugach accretionary complex, Alaska (T = 150-300 degrees C, P = 2-5 kilobars), 2) the Condrey Mountain Window, southern Klamath Mountains, northern California (T = 300-420 degrees C, P = 5-7 kilobars), and 3) the Cycladic Blueschist Unit in Syros Island, Greece (T = 450-550 degrees C, P = 2-15 kilobars). The project uses a wide range of structural, microstructural, and petrological tools to track macro-scale distributions of strain, degrees and mechanisms of strain localization, fluctuations in fluid pressures and strain rates, microphysical mechanisms of rock creep, effects of metamorphic reactions on deformation, and sources of anisotropy, in rocks that have been cycled through the subduction process. The research involves: 1) identifying domains in each field area that represent deformation under prograde conditions; 2) documenting macro-scale strain distributions; 3) determining the microphysical mechanisms of rock creep in different rock and mineral phases; and 4) synthesizing the field and microstructural observations in the context of subduction zone mechanics. The integrated educational objective of this CAREER award is to establish a five-year mentoring and research program at the University of Texas ? the Jackson School of Geosciences-Catalyst (JSGC) ? aimed at ethnic and racial minorities and first-generation college students in the Earth Sciences. JSGC will provide 1) mentoring, community support, and career advice for undergraduates through mentorship pairing, monthly meetings, social events, and field trips; and 2) financial support for members while simultaneously enhancing their undergraduate research experience through summer internships, senior thesis projects and participation in field-based team research. The JSGC program is designed to increase retention and completion rates of underrepresented minorities in STEM fields and to prepare and encourage these students to go on to graduate school.Processes in the zone between a subducting oceanic plate and the overriding plate ? the subduction zone interface - are responsible for a all-too-familiar yet poorly understood phenomena such as large devastating earthquakes as well as other more enigmatic events such as episodic slip and tremor. This project aims to improve understanding of this zone through a systematic study of terranes that were exhumed from the depths of the interface by various tectonic processes. These terranes provide an unusual opportunity to understand the geologic processes associated with the various phenomena along the subduction zone interface. Additionally, the project will advance desired societal outcomes through: (1) full participation of women and underrepresented minorities in STEM through support of an early career Hispanic female PI, a female graduate student, and, most notably, a robust plan to provide mentoring, and research and professional development opportunities to underrepresented minorities majoring in Earth Science, thus directly contributing to retention and promotion of underrepresented minorities in STEM fields; (2) development of a diverse, globally competitive STEM workforce through undergraduate and graduate student training with emphasis on mentoring students from underrepresented groups in Earth science; and (3) increased partnerships through international collaboration.

全球俯冲带的地球物理数据表明，俯冲界面具有流变学上的复杂性和不均匀性。对俯冲界面剪切带的挖掘遗迹的观测，使我们对控制这种复杂性的过程有了基本的了解。该项目的科学目标是利用折返岩石系统地研究俯冲界面的流变特性和演化。具体而言，该项目将调查俯冲界面剪切带内变形的不均匀性，以及随着岩石逐渐向深处俯冲，变形方式和机制的变化性质。该项目的研究部分将侧重于三个折返的俯冲剪切带，每个剪切带都记录了俯冲变形，共同代表了广泛的压力-温度条件。实地地点包括：1）阿拉斯加州楚加奇增生杂岩（T = 150-300 ℃，P = 2-5帕），2）加州北部北方克拉马斯山脉南部康涅兹山窗（T = 300-420 ℃，P = 5-7帕），3）希腊锡罗斯岛基克拉迪蓝片岩单元（T = 450-550 ℃，P = 2-15帕）。该项目使用广泛的结构，显微结构和岩石学工具来跟踪宏观尺度的应变分布，应变局部化的程度和机制，流体压力和应变率的波动，岩石蠕变的微观物理机制，变质反应对变形的影响，以及各向异性的来源，在已经通过俯冲过程循环的岩石中。研究涉及：1）识别每个野外区域中代表俯冲条件下变形的区域; 2）记录宏观尺度应变分布; 3）确定不同岩石和矿物相中岩石蠕变的微观物理机制;以及4）在俯冲带力学的背景下综合野外和微观结构观察。该职业奖的综合教育目标是在德克萨斯大学建立一个为期五年的指导和研究项目？杰克逊地球科学催化剂学院针对少数民族和种族以及地球科学领域的第一代大学生。JSGC将提供1）通过导师配对，每月会议，社交活动和实地考察为本科生提供指导，社区支持和职业建议;和2）为成员提供财政支持，同时通过暑期实习，高级论文项目和参与实地团队研究来增强他们的本科研究经验。JSGC项目旨在提高STEM领域中代表性不足的少数民族的保留率和完成率，并为这些学生做好准备，鼓励他们继续读研究生。俯冲大洋板块和覆盖板块之间的过程？俯冲带界面-是造成一个太熟悉但知之甚少的现象，如大破坏性地震以及其他更神秘的事件，如幕式滑动和震颤。该项目旨在通过系统研究各种构造过程从界面深处挖出的岩石，增进对这一地带的了解。这些岩石提供了一个不寻常的机会，了解地质过程与各种现象沿着俯冲带界面。此外，该项目还将通过以下方式促进预期的社会成果：（1）通过支持早期职业生涯的西班牙裔女性PI，女性研究生，以及最值得注意的是，一个强大的计划，为地球科学专业的代表性不足的少数民族提供指导，研究和专业发展机会，（2）通过对本科生和研究生的培训，培养一支多元化的、具有全球竞争力的STEM人才队伍，重点是指导来自地球科学领域代表性不足群体的学生;（3）通过国际合作加强伙伴关系。