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.

来自世界各地俯冲带的地球物理数据表明，俯冲界面具有复杂的流变性和非均质性。对俯冲界面剪切带挖出的残留物的观察，为控制这种复杂性的过程提供了基本的见解。该项目的科学目标是利用折返的岩石系统地研究俯冲界面的流变性和演化。具体地说，该项目将调查俯冲界面剪切带内变形的不均质性，以及随着岩石逐渐俯冲到深处，变形方式和机制变化的本质。该项目的研究部分将集中在三个折返的俯冲剪切带上，每个俯冲剪切带都记录了前进的变形，它们共同代表了广泛的压力-温度条件。野外地点包括：1)阿拉斯加的Chugach增积杂岩(T=150-300摄氏度，P=2-5千巴)，2)加利福尼亚州北部克拉马斯山脉南部的康德雷山窗(T=300-420摄氏度，P=5-7千巴)，以及3)希腊锡罗斯岛的Cycldic蓝片岩单元(T=450-550摄氏度，P=2-15千巴)。该项目使用广泛的构造、微观构造和岩石学工具来跟踪岩石中的宏观应变分布、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。这项研究包括：1)确定每个区域中代表前进条件下变形的区域；2)记录宏观尺度的应变分布；3)确定不同岩石和矿物相中岩石蠕变的微观物理机制；4)在俯冲带力学的背景下综合野外和微观结构观察。这一职业奖项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计划。杰克逊地球科学学院催化剂(JSGC)？面向少数族裔和少数族裔以及地球科学领域的第一代大学生。JSGC将通过导师配对、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、高级论文项目和参与实地团队研究来增强他们的本科生研究经验。JSGC计划旨在提高STEM领域中代表性不足的少数民族的保留率和毕业率，并为这些学生继续深造做准备和鼓励他们继续读研究生。俯冲带界面--这是一种非常熟悉但却鲜为人知的现象，如大的破坏性地震，以及其他更神秘的事件，如幕式滑动和震动。该项目旨在通过对各种构造作用从界面深处挖掘出来的地体进行系统研究，增进对该地带的了解。这些地体提供了一个不同寻常的机会来了解与俯冲带界面上的各种现象相关的地质过程。此外，该项目还将通过以下方式促进预期的社会成果：(1)妇女和任职人数不足的少数群体充分参与STEM，途径是支持一名西班牙裔女性PI，这是一名女研究生，并且最值得注意的是，制定一项强有力的计划，为攻读地球科学专业的任职人数不足的少数群体提供辅导、研究和职业发展机会，从而直接有助于留住和促进STEM领域中任职人数不足的少数群体；(2)通过本科生和研究生培训，发展一支多样化的、具有全球竞争力的STEM工作人员队伍，重点是辅导地球科学领域任职人数不足的群体的学生；(3)通过国际合作增加伙伴关系。