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

世界范围内俯冲带的地球物理资料表明，俯冲界面在流变学上是复杂和非均质的。对俯冲界面剪切带出土残余物的观察，使我们对控制这种复杂性的过程有了基本的认识。该项目的科学目标是利用挖掘出的岩石系统地研究俯冲界面的流变特性和演化。具体而言，该项目将研究俯冲界面剪切带内变形的非均质性，以及随着岩石逐渐俯冲到深处，变形样式和机制变化的性质。该项目的研究部分将集中在三个被挖掘出来的俯冲剪切带上，每个剪切带都记录了递进变形，并共同代表了广泛的压力-温度条件。野外地点包括：1)阿拉斯加Chugach沉积杂岩（T = 150-300℃，P = 2-5千巴），2)加州北部Klamath山脉南部Condrey Mountain Window （T = 300-420℃，P = 5-7千巴），以及3)希腊Syros岛基克拉迪奇蓝片单元（T = 450-550℃，P = 2-15千巴）。该项目使用广泛的结构、微观结构和岩石学工具来跟踪通过俯冲过程循环的岩石的宏观应变分布、应变局部化程度和机制、流体压力和应变率波动、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。研究内容包括：1)识别各场域中代表进动条件下变形的区域；2)记录宏观应变分布；3)确定不同岩石和矿物相下岩石蠕变的微观物理机制；4)在俯冲带力学背景下，综合野外和微观构造观测。CAREER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。杰克逊地球科学学院-催化剂（JSGC） ？针对少数民族和种族以及地球科学专业的第一代大学生。JSGC将通过导师配对、月度会议、社交活动和实地考察，为本科生提供1)指导、社区支持和职业建议；2)为成员提供经济支持，同时通过暑期实习、毕业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领域代表性不足的少数族裔学生的留校率和完成率，并为这些学生继续读研做好准备和鼓励。俯冲洋板块与上覆板块之间的过程？俯冲带界面——是我们非常熟悉但却知之甚少的现象的原因，比如毁灭性的大地震，以及其他更神秘的事件，比如间歇性的滑动和震颤。本项目旨在通过对各种构造过程从界面深处挖掘出来的地体进行系统研究，提高对该带的认识。这些地体为了解与俯冲带界面沿线各种现象相关的地质过程提供了难得的机会。此外，该项目将通过以下方式推进预期的社会成果：(1)通过支持一名早期职业生涯的西班牙裔女性PI和一名女研究生，让女性和未被充分代表的少数族裔充分参与STEM，最值得注意的是，为未被充分代表的地球科学专业少数族裔提供指导、研究和专业发展机会的强有力计划，从而直接有助于保留和促进STEM领域未被充分代表的少数族裔；(2)通过本科生和研究生培训，重点指导来自地球科学领域代表性不足群体的学生，培养一支多元化的、具有全球竞争力的STEM劳动力队伍；(3)通过国际合作加强伙伴关系。

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.