CAREER: Understanding Major Intracontinental Strike-slip Faults from the Lower Crust's Perspective: Tibetan Insights from the Canadian Shield

职业：从下地壳的角度了解主要的陆内走滑断层：来自加拿大地盾的西藏见解

• 批准号: 1255277
• 负责人: Gregory Dumond
• 金额: $ 45.35万
• 依托单位: University of Arkansas
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-06-01 至 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1255277&HistoricalAwards=false
• 关键词: CAREER; Understanding; Major; Intracontinental; Strike

The relationship between continental collision and deformation along lithosphere-scale (hundreds of km-long) intracontinental strike-slip faults remains intensely debated. Debate persists because despite what we know about this important class of faults at the surface, we know comparatively little about how these structures work in the lower crust. Questions regarding the degree of strain localization, the lateral extent of rheological heterogeneities, and the physical nature of major intracontinental faults at depth will be answered "in situ" in this project by studying a well-exposed deep crustal shear zone and its wall rocks, i.e., the 400 km-long intracontinental Grease River shear zone in the western Canadian Shield (exhumed from ~30 to 40 km-paleodepths). Preliminary data support the hypothesis that at ca. 1.92-1.90 Ga, lower crust NW of the Grease River shear zone was melt-weakened at the same time that lower crust SE of the Grease River shear zone was dehydrated and strong. This ?rheological dichotomy? may be analogous to lower crust beneath the steep topographic gradients and major intracontinental fault systems that mark the margins of the Tibetan Plateau, e.g., the Altyn Tagh and Longmen Shan ranges.This project will provide field-based constraints on the role of rheological heterogeneity in facilitating strain localization across a major intracontinental strike-slip fault from the lower crust's perspective. Anticipated results include: (1) resolving the Pressure-Temperature conditions and paths for metamorphic tectonites in the Grease River shear zone and its wall rocks, (2) testing the contemporaneity of deformation, shearing, and partial melting using in situ Th-U-total Pb dates on monazite via EPMA, and (3) constraining a 500 m.y. history of shear zone reactivation via high-precision ID-TIMS U-Pb dates on zircon from a suite of cross-cutting and variably-deformed dikes.Broader impacts of this project include: (1) implementing a program of 6th-8th grade teacher preparation and enhancement, and (2) public outreach via classroom visits and panel discussions that are all focused on faulting and earthquakes in intracontinental systems. These efforts will directly impact teachers and students who live in the immediate vicinity of unexposed intracontinental faults of the New Madrid seismic zone ? the most seismically active region east of the Rocky Mountains. Two professional development summer institutes (workshops + field trips) will be provided to teachers utilizing inquiry-based modules to be developed by the PI. Implementation and assessment of these modules will impact middle school Earth Science frameworks in Arkansas (and nationally via on-line dissemination of the modules). These efforts will be in collaboration with the University of Arkansas' Center for Math and Science Education. Training and education will be provided to at least one Ph.D. student, one M.S. student, and several undergraduate students who will be integrally involved in the research and outreach efforts. This project directly impacts the new geoscience Ph.D. program at the University of Arkansas. Benefits to the EarthScope community are also anticipated, as this project uses an exposed deep crustal shear zone in the Canadian Shield to inform our understanding of the structure, rheology, and timing of a major intracontinental strike-slip fault as it may have existed in the lower crust near the Moho.

大陆碰撞与沿着岩石圈尺度（数百公里长）的陆内走滑断层变形之间的关系一直存在着激烈的争论。争论仍在继续，因为尽管我们对地表的这类重要断层有所了解，但我们对这些结构在下地壳中的作用知之甚少。关于应变局部化程度、流变不均匀性的横向范围以及深部主要陆内断层的物理性质的问题，将在本项目中通过研究一个暴露良好的深部地壳剪切带及其围岩来"就地"回答，加拿大地盾西部400 km长的陆内Grease River剪切带（从~30 - 40 km古深度挖掘）。初步数据支持的假设，在CA。1.92 - 1.90 Ga，Grease River剪切带NW向下地壳熔融弱化，同时，Grease River剪切带SE向下地壳脱水变强。这个吗流变学二分法可能类似于陡峭地形梯度下的下地壳和标志着青藏高原边缘的主要陆内断层系统，例如，该项目将从下地壳的角度提供流变学非均匀性在促进跨主要陆内走滑断层的应变局部化中的作用的基于现场的约束。预期成果包括：（1）解决了Grease River剪切带及其围岩中变质构造岩的压力-温度条件和路径;（2）利用电子探针对独居石进行的原位Th-U-总Pb测年测试了变形、剪切和部分熔融的同时代性;剪切带再活化的历史，通过高精度ID-TIMS U-Pb年龄锆石从一套横切和可变变形的dikes.The更广泛的影响，该项目包括：（1）实施一个计划，6 - 8年级教师的准备和提高，（2）通过课堂访问和小组讨论，都集中在断层和地震的陆内系统的公众宣传。这些努力将直接影响教师和学生谁住在附近的未暴露的陆内断层的新马德里地震带？落基山脉以东地震最活跃的地区两个专业发展暑期学院（讲习班+实地考察）将提供给教师利用调查为基础的模块将由PI开发。这些模块的实施和评估将影响阿肯色州的中学地球科学框架（并通过模块的在线传播在全国范围内）。这些努力将与阿肯色州大学的数学和科学教育中心合作。将向至少一名博士提供培训和教育。学生，一个MS。学生，和几个本科生谁将在研究和推广工作的整体参与。这个项目直接影响到新的地球科学博士。阿肯色州大学的一个项目。对EarthScope社区的好处也是预期的，因为这个项目使用了加拿大地盾中暴露的深地壳剪切带，以告知我们对一个主要陆内走滑断层的结构、流变学和时间的理解，因为它可能存在于莫霍面附近的下地壳中。

项目成果

Monazite as a monitor of melting, garnet growth and feldspar recrystallization in continental lower crust

• DOI: 10.1111/jmg.12150
• 发表时间: 2015-09
• 期刊: Journal of Metamorphic Geology
• 影响因子: 3.4
• 作者: G. Dumond;P. Goncalvès;Michael L. Williams;M. Jercinovic

Tibetan dichotomy exposed in the Canadian Shield: A lower crustal perspective

加拿大地盾中暴露的西藏二分法：下地壳视角

• DOI: 10.1016/j.epsl.2020.116375
• 发表时间: 2020
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Dumond, Gregory

Garnet-forming reactions in felsic orthogneiss: Implications for densification and strengthening of the lower continental crust

长英质正片麻岩中的石榴石形成反应：对下大陆地壳致密化和强化的影响

• DOI: 10.1016/j.epsl.2014.08.030
• 发表时间: 2014
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Williams, M.L.;Dumond, G.;Mahan, K.;Regan, S.;Holland, M.
• 通讯作者: Holland, M.

Monazite as a monitor of shear strain in orogenic crust

独居石作为造山地壳剪切应变的监测器

• DOI: 10.1016/j.jsg.2022.104672
• 发表时间: 2022
• 期刊: Journal of Structural Geology
• 影响因子: 3.1
• 作者: Dumond, Gregory;Mahan, Kevin H.;Goncalves, Philippe;Williams, Michael L.;Jercinovic, Michael J.
• 通讯作者: Jercinovic, Michael J.

Backarc origin for Neoarchean ultrahigh-temperature metamorphism, eclogitization, and orogenic root growth

新太古代超高温变质作用、榴辉岩作用和造山根生长的弧后起源

• DOI: 10.1130/g39254.1
• 发表时间: 2017
• 期刊: Geology
• 影响因子: 5.8
• 作者: Dumond, Gregory;Williams, Michael L.;Baldwin, Julia A.;Jercinovic, Michael J.
• 通讯作者: Jercinovic, Michael J.