Collaborative Research: Deformation and Magmatic Modification of a Steep Continental Margin, Western Idaho-eastern Oregon

合作研究：爱达荷州西部-俄勒冈州东部陡峭大陆边缘的变形和岩浆改造

• 批准号: 0844264
• 负责人: John Hole
• 金额: $ 75.52万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0844264&HistoricalAwards=false
• 关键词: Collaborative; Research; Deformation; Magmatic; Modification

This award is funded under the American Recovery and Reinvestment Actof 2009 (Public Law 111-5).Much of the land area of Washington, Oregon, and California was added to continental North America during the last 200 million years. Exactly how this dominantly oceanic lithosphere accreted to the continent is not well understood, although it is clear that the processes involved differed from north to south along North America's former western margin. In the Idaho-Oregon border region, the boundary between oceanic and continental lithospheres is well exposed in a very narrow zone of high deformation known as the western Idaho shear zone. This project is providing insight into how this sharp boundary formed, how it has controlled subsequent deformation and magmatism regionally, and the role it has played in the formation of North America. Because the Oregon-Idaho segment separates distinct styles of mountain building in California and the southern Canadian Cordillera, a better understanding of this complex region is critical for developing a coherent model for the tectonic evolution of western North America and ultimately helping us understand proceses by which continents are created and evolve through time.Research scientists from the University of Wisconsin, Virginia Tech, The University of Florida, and Washington State University are integrating the results of seismological, geochemical, geochronologic, and structural geologic studies in order to investigate three major issues associated with the evolution of this continental margin: 1) How do fundamental lithospheric structures, such as the continental-oceanic lithosphere boundary exposed in the western Idaho shear zone, guide subsequent deformation and magmatism?; 2) How do magmatism and extensional deformation modify (destabilize) the continental lithosphere, and at what lithospheric levels?; and 3) What are the tectonic implications of this destabilization for evolving magmatism, deformation, and lithospheric strength? A swath of broadband passive seismic instruments and a seismic refraction line will delineate the current geometry of the major geologic units and their boundaries to several hundred kilometers depth. Geochemistry and geochronology will characterize post- western Idaho shear zone magmatism to provide the timing of events and the tectonic context in which these processes occurred. Structural geology will provide the kinematic and dynamic deformation path by which the continent was modified, by defining the major tectonic boundaries and establishing the kinematic history of the major structures.In addition to the research objectives of this project, the award will support the education and training of four graduate students and eight undergraduate students distributed between the four universities, and supports an early career researcher at the University of Florida.

该奖项根据 2009 年美国复苏和再投资法案（公法 111-5）提供资金。华盛顿、俄勒冈和加利福尼亚的大部分土地面积在过去 2 亿年中被纳入北美大陆。尽管很明显，沿北美前西缘从北到南所涉及的过程有所不同，但这种主要为海洋的岩石圈到底是如何增生到大陆的尚不清楚。在爱达荷州和俄勒冈州边境地区，海洋和大陆岩石圈之间的边界在一个非常狭窄的高变形区域（称为西爱达荷剪切带）中充分暴露。该项目旨在深入了解这一尖锐边界是如何形成的，它如何控制随后的区域变形和岩浆活动，以及它在北美形成中所发挥的作用。由于俄勒冈-爱达荷段将加利福尼亚州和加拿大南部科迪勒拉山脉的不同造山风格分开，因此更好地了解这一复杂地区对于开发北美西部构造演化的连贯模型并最终帮助我们了解构造演化的过程至关重要。大陆随着时间的推移而形成和演变。来自威斯康星大学、弗吉尼亚理工大学、佛罗里达大学和华盛顿州立大学的研究科学家正在整合地震学、地球化学、地质年代学和构造地质学的成果为了调查与该大陆边缘演化相关的三个主要问题：1）基本岩石圈结构，例如暴露在爱达荷州西部剪切带的大陆-海洋岩石圈边界，如何指导随后的变形和岩浆活动？ 2）岩浆作用和伸展变形如何改变（破坏）大陆岩石圈，以及在什么岩石圈水平？ 3）这种不稳定对于不断演化的岩浆作用、变形和岩石圈强度有什么构造影响？一系列宽带被动地震仪器和地震折射线将描绘出主要地质单元的当前几何形状及其数百公里深度的边界。地球化学和地质年代学将描述爱达荷州西部剪切带岩浆作用后的特征，以提供事件的时间和这些过程发生的构造背景。构造地质学将通过定义主要构造边界并建立主要构造的运动学历史，提供改变大陆的运动学和动态变形路径。除了该项目的研究目标外，该奖项还将支持教育和培训分布在四所大学的四名研究生和八名本科生，并支持佛罗里达大学的一名早期职业研究员。