Collaborative Research: Unraveling Protracted Tectonic Reactivation in Cordilleran Metamorphic Core Complexes: Funeral Mountains, California

合作研究：解开科迪勒拉变质核复合体中长期的构造重新激活：加利福尼亚州葬礼山

• 批准号: 1550154
• 负责人: Thomas Hoisch
• 金额: $ 24.96万
• 依托单位: Northern Arizona University
• 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: 2016-01-01 至 2021-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1550154&HistoricalAwards=false
• 关键词: Collaborative; Research; Unraveling; Protracted; Tectonic

The propensity for fault zones to become long-lived zones of weakness that can be reactivated during geologic history plays a significant role in the migration of fluids in Earth?s crust and formation of hydrocarbon, economic mineral and ground water resources, seismic hazards, and the evolution of mountain belts. From 160 to 50 million years ago, the western U.S. was tectonically similar to modern day western South America, which is characterized by high elevation mountains (the Andes) that formed in the continental crust above an actively subducting oceanic plate. When subduction ceased along western North America, a new regime of widespread crustal extension began, resulting in localized exposures at the surface of deep levels of the ancient mountain belt. This project will examine the Funeral Mountains in Death Valley National Park, which the principal investigators hypothesize records the cycle of mountain building followed by extension. In particular, they hypothesize that the same fault (a thrust fault) initially responsible for substantial burial and thickening of the crust was reactivated twice during the exhumation of the rocks to the surface. They further argue that the reactivation of thrust faults may be a common phenomenon in the western U.S., explaining many similar occurrences in other mountain ranges. Rocks in the Funeral Mountains are ideal for testing this hypothesis due to excellent exposures and abundant rocks suitable for study. This project will accomplish many benefits to society as identified by NSF: (1) helping the U.S. maintain competitiveness and leadership in the global Science Technology Engineering and Mathematics (STEM) workforce; students who participate in the project (three graduate students and five undergraduates) will develop high-level expertise and teamwork experience in a STEM discipline; (2) increased public scientific literacy by dissemination of findings to the academic community through presentations at professional conferences and publications, and to the general public and Death Valley enthusiasts by presenting at meetings of the Death Valley Natural History Association, the Las Vegas Natural History Museum, and the Nevada Geological Society; (3) development of research partnerships between two universities as part of collaborative research efforts, and the development of research infrastructure at each institution; and; (4) the investigators seek to engage the full participation of women and underrepresented students in STEM education through targeted recruiting efforts.Reactivation and tectonic inheritance are long-recognized phenomena, important to our understanding of how the continental lithosphere deforms. The thesis of this proposal is that many Tertiary detachment faults and shear zones in the western US reactivate faults or sub-planar zones of earlier deformation. The Funeral Mountains metamorphic core complex of the Death Valley region represents an ideal locality in the Sevier-Laramide hinterland to evaluate the role of tectonic reactivation in the development of metamorphic core complexes, as well as to resolve important details regarding the tectonic history that predates Tertiary extension. We hypothesize that the Boundary Canyon detachment fault, which underwent greater than 40 kilometers of top-the northwest slip in the Miocene, formed as the last reactivation of a major Jurassic thrust of opposite slip that was responsible for deep burial and regional metamorphism of the footwall. We propose a multi-faceted approach to evaluate the hypothesis of protracted tectonic reactivation through detailed studies along the metamorphic and strain gradient that includes: (1) field mapping and structural analysis, (2) petrographic, microstructural, and kinematic analyses aided by Electron Backscatter Diffraction analysis of quartz-rich rocks, (3) applying petrochronology (Laser Ablation Split Stream Inductively Coupled Plasma Mass Spectrometry) to date accessory minerals (metamorphic titanite, monazite, xenotime, and zircon overgrowths) and Lutetium-Hafnium dating of garnet in garnet amphibolites, and (4) determining the metamorphic conditions and prograde pressure-temperature paths to evaluate the prograde burial history, possible grade discordances across major shear zones, and the regional thrust-induced paleodip. Recognition of tectonic reactivation has important implications for understanding the older Jurassic and Cretaceous history of the Sevier-Laramide orogen, the magnitude and distribution of contraction and extension that occurred during orogenesis, and the episodic nature of post-orogenic extension.

断层区成为长期弱点的倾向，在地质历史上可以重新激活，在地球中的液体的迁移以及碳氢化合物，经济矿物质和地下水资源，地震危害以及山皮带的演变中起着重要作用。从160年到5000万年前，美国西部与现代南美西部相似，西部的特征是高海拔山脉（安第斯山脉），在积极俯冲的海洋板上的大陆壳中形成。 当俯冲沿北美西部停止时，开始了广泛的地壳扩展，从而在古代山带深层的地面上导致局部暴露。该项目将检查死亡谷国家公园中的葬礼山，主要调查人员假设该葬礼记录了山区建筑的周期，其次是扩展。 特别是，他们假设在岩石挖掘到表面的过程中，两次重新激活了相同的断层（推力断层），最初是造成大量埋葬和地壳增厚的相同断层（螺栓断层）。他们进一步认为，在美国西部，推力断层的重新激活可能是一个普遍现象，这解释了其他山区的许多类似事件。葬礼山上的岩石是检验该假设的理想选择，这是由于出色的暴露和适合研究的丰富岩石。 该项目将为NSF确定的社会带来许多好处：（1）帮助美国在全球科学技术工程和数学（STEM）劳动力中保持竞争力和领导力；参加该项目的学生（三名研究生和五名大学生）将在STEM学科中发展高级专业知识和团队合作经验； （2）通过在专业会议和出版物上的演讲向学术界传播发现，以及向公众和死亡谷爱好者在死亡谷自然历史协会，拉斯维加斯自然历史博物馆和内华达地质社会的会议上提出的，提高了公共科学素养； （3）作为协作研究工作的一部分以及每个机构研究基础设施的发展，建立了两所大学之间的研究伙伴关系；和; （4）调查人员试图通过有针对性的招聘工作来吸引妇女和代表性不足的学生参与STEM教育。反应和构造遗传是长期认可的现象，对我们对大陆岩石圈如何变形的理解很重要。该提议的论点是，美国西部的许多高等脱离断层和剪切区都重新激活了早期变形的断层或亚平面区。死亡谷地区的葬礼山变质核心复合物代表了塞维尔 - 德拉米德腹地的理想位置，以评估构造重新激活在变质核心复合物发展中的作用，并解决有关涉及tectonic历史的重要细节。我们假设，边界峡谷脱离断层在中新世中经历了超过40公里的西北滑动，这是对相反滑动的主要侏罗纪推力的最后一次重新激活，这是造成脚壁的深层埋葬和区域变质的原因。 We propose a multi-faceted approach to evaluate the hypothesis of protracted tectonic reactivation through detailed studies along the metamorphic and strain gradient that includes: (1) field mapping and structural analysis, (2) petrographic, microstructural, and kinematic analyses aided by Electron Backscatter Diffraction analysis of quartz-rich rocks, (3) applying petrochronology (Laser Ablation Split Stream电感耦合等离子体质谱法）至日期辅助矿物（变质钛矿，单位岩，异族，异种和锆石过度生长）和石榴石中石榴石的Lutetium-hafnium在石榴石片剂中的日期，以及（4）确定变态的差异较高的谱系较高的疗程主要的剪切区和区域推力引起的古代。识别构造重新激活对理解塞维尔 - 拉酰胺造山机的较早的侏罗纪和白垩纪历史具有重要意义，在造山机发生过程中发生的收缩和扩展的大小和分布以及后巨型延伸的发作性质。