Collaborative Research: Origin of Long-lived Crustal Shear Zones as Transforms or Subduction Zones?

合作研究：作为转换带或俯冲带的长寿地壳剪切带的起源？

• 批准号: 1549902
• 负责人: William McClelland
• 金额: $ 11.2万
• 依托单位: University of Iowa
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2019-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1549902&HistoricalAwards=false
• 关键词: Collaborative; Research; Origin; Long; lived

Large-scale faults (1000 kilometer) are first-order features observed at Earth's active and ancient plate boundaries. Active faults, such as the San Andreas, accommodate relative motion between tectonic plates. Ancient plate boundary faults now within plates, such as the New Madrid fault in Missouri, can also continue to be active, as demonstrated by major earthquakes on them. Why some plate boundary faults remain the locus of crustal deformation and uplift 100s of millions of years after they form has remained a topic of debate. This study will provide ideas on how and why some major faults that form at plate boundaries persist as zones of weakness in the crust, prone to reactivation. The results will ultimately inform a broad group of scientists on deep crustal processes that control the location of seismicity, high heat flow, and hydrothermal systems that may have implications for the understanding of geologic hazards and resources. In addition to the scientific goals of the project, important societal relevant outcomes of the project will include the training of graduate and undergraduate students in an important STEM (Science, Technology, Engineering and Mathematics) discipline. The project will facilitate collaborative research between three U.S. research institutions, thus contributing to support of scientific infrastructure. It will provide research funding for two early career gescientists. The project will contribute to the broadening of participation of underrepresented groups in STEM. Importantly, the project will foster international collaboration and exchange between U.S. and Argentine scientists. Results of the research will be broadly disseminated through presentations at professional society meetings and in peer-reviewed scientific publications. The presence of major fault zones within continental crust which show evidence for reactivation over 100s of millions of years defies models for continuum deformation of the continents, wherein faults are viewed as passive features responding to mantle flow. Large-scale faults occur on every continent and many long-lived intracontinental fault systems record complex histories of reactivation, in particular localizing convergent and strike-slip deformation. This research will test competing models for the origin of persistent large-scale faults by studying the tectonic history of exhumed middle and lower crust sections of an ancient fault zone. End member models predict that such fault zones originate either as: 1) convergent-collisional boundaries between blocks of different strength, 2) transform boundaries along pre-existing zones of weakness, or 3) strike-slip boundaries within the arc-forearc region of oblique subduction settings. The Valle Fertil fault zone of western Argentina is an approximately 1200-kilometer-long major crustal lineament that records at least 400 million years of intermittent deformation and is an ideal location to test the above models because of excellent geophysical constraints on crustal strength contrasts, variable depths of exposure along strike, a well constrained tectonic evolution, and ideal mineral assemblages for dating the history of deformation within the fault. The results from the Valle Fertil fault can be applied to other intracontinental faults to address what factors determine the origin of major structures within complex orogens and the processes by which they ultimately become large-scale faults with complex histories of continued reactivation.

大型断层（1000公里）是在地球活动和古老的板界处观察到的一阶特征。主动断层（例如San Andreas）适应构造板之间的相对运动。如今的主要地震表明，现在板块内的古老板块边界断层（例如密苏里州的新马德里断层）也可以继续活跃。为什么某些板边界断层仍然是地壳变形的轨迹和形成后数百万年的升起的座位，这仍然是一个辩论的话题。这项研究将提供有关在板边界处形成的一些主要故障的想法，为什么仍然是地壳中弱点的区域，容易重新激活。结果最终将为一群科学家提供深层的地壳过程，这些过程控制着地震性，高热量流量和水热系统的位置，这可能对理解地质危害和资源有影响。除了该项目的科学目标外，该项目的重要社会相关结果还将包括在重要的STEM（科学，技术，工程和数学）学科中培训研究生和本科生。该项目将促进三个美国研究机构之间的合作研究，从而有助于支持科学基础设施。它将为两位早期职业生涯主义者提供研究资金。该项目将有助于扩大STEM代表性不足的群体的参与。重要的是，该项目将促进美国和阿根廷科学家之间的国际合作与交流。这项研究的结果将通过专业社会会议和同行评审的科学出版物的演讲进行广泛传播。大陆地壳中存在主要断层区域的存在，这些区域显示了超过100千年来重新激活的证据，违反了大陆连续变形的模型，其中将断层视为对地幔流动响应的被动特征。大规模断层发生在每个大陆上，许多长寿命内的断层系统都记录了重新激活的复杂历史，尤其是定位的收敛和滑移变形。 这项研究将通过研究古代断层区的中层和下地壳部分的构造历史来测试持续大规模断层的竞争模型。最终成员模型预测，这种断层区域的起源为：1）不同强度的块之间的收敛 - 碰撞边界，2）沿着弱点的预先存在的区域转变边界，或者3）在斜体缩减设置的Arc-Forearc区域内的滑滑边界。 阿根廷西部的Valle受精断断带是一个约1200公里的重大地壳谱系，记录了至少4亿年的间歇性变形，并且是测试上述模型的理想位置，因为对地壳强度对比的地球物理强度极好的地球物理限制，沿撞击的可变深度，沿撞击的可变深度，构成了良好的结构性变化，并构成了良好的临近型号，并理想的是，构造的经验丰富了，并且是理想的，理想的经验丰富的经验。 Valle受精断断的结果可以应用于其他肠内断层，以解决哪些因素决定了复杂的Orogens中主要结构的起源以及它们最终成为具有持续重新激活历史的大规模断层的过程。