Collaborative Research: Documenting the transition from contraction to extension in the Ruby-East Humboldt-Wood Hills Metamorphic Core Complex, Southwestern U.S. Cordillera

合作研究：记录美国西南部科迪勒拉红宝石-东洪堡-伍德山变质核心复合体从收缩到扩张的转变

• 批准号: 1728274
• 负责人: Caroline Meisner
• 金额: $ 6.83万
• 依托单位: Great Basin College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-01 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1728274&HistoricalAwards=false
• 关键词: Collaborative; Research; Documenting; transition; contraction

The mountainous western U.S., commonly referred to as the Cordillera, has experienced near constant geologic deformation and reorganization over the past few hundred million years. Large mountain ranges have been created and destroyed, volcanism has flared up and died away, and an enormous section of the west, basically from Salt Lake City, Utah to Reno, Nevada, has roughly doubled in size due to extreme stretching and extension of Earth's upper crust. This extended region, the Basin and Range province, has been the focus of decades of research and exploration by geoscientists and prospectors, and now hosts some of the largest mineral deposits in North America. Despite years of investigation using a wide range of methods, fundamental questions persist about the mechanisms that drove extension. Central to these debates is the timing and rate of deformation. Fundamentally, evidence from different depths of the crust yield differing interpretations, with evidence from the deeper earth documenting older, Cretaceous (approximately 70 million years ago) deformation, whereas studies of the shallower crust highlight later, Miocene (approximately 15 million years ago) processes. This study proposes to bridge the gap between these two data sets and reconcile these seemingly disparate histories by focusing on an exceptionally well-exposed section of crust in the Ruby Mountains - East Humboldt Range - Wood Hills Metamorphic Core Complex, an area of northeastern Nevada that is also of great economic interest due to its situation in the heart of North America's richest gold-producing province. The rocks that make up these ranges represent a thick column of the crust that was brought to the surface and tilted on its side during extension, and offer an unprecedented view into the geologic processes operating across multiple crustal levels. A suite of relatively new isotopic dating techniques will document the time - temperature history of the rocks and thus the full history of tectonic uplift. The research conducted during this study will provide important societal outcomes through training of undergraduate students in an important STEM (science, technology, engineering, and mathematics) discipline, thus contributing to development of a globally competitive workforce. The project will also contribute to increased scientific literacy and public engagement with STEM. The project embeds substantial outreach and educational components. The world-class geology of the study area provides an ideal stage for direct community engagement through strategic and comprehensive outreach to local science educators and geoscience professionals. By forging an innovative collaboration between two R1 Research institutions and Great Basin College--the institution primarily responsible for training science educators across most of rural Nevada. The principal investigator's educational outreach will focus on three main goals; (1) creating and making widely available interactive field trip guides and tutorials focusing on both the research as well as numerous fundamental geoscience concepts that can be demonstrated in the proposed research area; (2) creating permanent and mobile displays for Great Basin College campuses across the state of Nevada; and (3) creating learning modules and tutorials for learners at a variety of levels, including dual-credit high school students enrolled in geology courses, traditional college students, and education students preparing to become K-12 educators. Outreach materials will highlight the central role that northeastern Nevada's tectonic history plays in its citizens' physical and economic well-being. Technical results of the research will be widely disseminated through presentations at professional geoscience meetings and the peer-reviewed scientific literature. One of the most dramatic shifts in the tectonic architecture of North American in the Phanerozoic is the Late Cretaceous to Cenozoic transition of the Cordillera from large-scale shortening and crustal thickening to widespread regional extensional collapse. While certain aspects of this geologic history are well understood, critical questions remain unresolved regarding the distribution, rates, style, and timing of the early extensional evolution. Key to addressing these crucial questions are the metamorphic core complexes--regions where extreme crustal extension has exposed thick crustal sections with protracted tectonic histories. However, each of the classic metamorphic core complexes of the northeastern Great Basin yield fundamentally disparate interpretations of the timing and tectonic significance of exhumation depending on whether the data derive from deeper or shallower structural levels. In each case, lines of evidence drawn primarily from higher temperature thermochronometry, integrated Pressure-Temperature-time paths, and structural analyses of mid- to deep-crustal rocks suggest older, more protracted and often more complex exhumational histories; in contrast, low-temperature thermochronometry and syntectonic sedimentation commonly record a simpler and more youthful record of widespread Miocene extensional unroofing. This study will directly address these problems and bridge the current gap in understanding by using low- and medium-temperature (Uranium-Thorium)/Helium and 40Argon/39Argon thermochronology within a detailed and well-understood structural framework to constrain a complete cooling and exhumational history for northeastern Nevada's Ruby Mountains - East Humboldt Range - Wood Hills metamorphic core complexes. By integrating a range of thermochronometers and field relationships this study will reconcile disparate exhumational histories derived from disconnected investigations of deep-crustal and upper-crustal processes. In doing so, it will directly test competing hypotheses for the onset, duration, and driving forces of Basin and Range extension and exhumation. Specifically, this proposal will address three key questions: (1) when did extension initiate in the Ruby Mountains - East Humboldt Range - Wood Hills metamorphic core complexes, (2) how did the crustal geotherm evolve during the Cretaceous to present, and (3) if early phases of extension occurred, why did they fail to produce a syntectonic stratigraphic record?

在过去的几亿年中，美国山区西部通常被称为Cordillera，经历了几乎持续的地质变形和重组。大型山脉已经被创造和摧毁，火山爆发了，爆发了，西部的一部分地区基本上是从犹他州的盐湖城到内华达州里诺的，由于地球上层地壳的极端伸展和延伸，大约翻了一番。这个扩展的地区是盆地和山脉省，一直是地球科学家和探矿者数十年来研究和探索的重点，现在是北美一些最大的矿藏。尽管使用了多种方法进行了多年的调查，但基本问题仍然存在有关推动扩展的机制。这些辩论的核心是变形的时机和速率。从根本上讲，来自地壳不同深度的证据产生了不同的解释，从更深的地球上记录了更老的白垩纪（大约7000万年前）变形的证据，而对浅层地壳的研究则突出显示后来，中新世（大约1500万年前）过程。这项研究提议弥合这两个数据集之间的差距，并通过重点关注红宝石山脉中的外壳（East Humboldt Range） - 伍德希尔斯变态核心复合物（Nevada）的一个地区，在内华达州东北部的一个地区，由于其在北部美国北部美国的富有良好的经济兴趣，它也具有极大的经济利益，因此它在红宝石山上 - 伍德希尔斯变态核心综合体（East Humboldt range） - 伍德希尔斯变态核心（East Humboldt Range），并调和了这些看似截然不同的历史。构成这些范围的岩石代表了地壳的厚柱，在延伸过程中，将其带到表面并在其侧面倾斜，并为在多个地壳水平运行的地质过程中提供前所未有的视图。一套相对较新的同位素约会技术将记录岩石的时间温度历史，从而记录构造隆起的完整历史。在本研究中进行的研究将通过在重要的STEM（科学，技术，工程和数学）学科中培训本科生来提供重要的社会成果，从而有助于发展具有全球竞争性的劳动力队伍。该项目还将有助于提高科学素养和与STEM的公众参与。该项目嵌入了大量的外展和教育组成部分。研究领域的世界一流地质通过战略和全面的宣传到当地科学教育者和地球科学专业人员，为直接社区参与提供了理想的阶段。通过在两家R1研究机构和大盆地学院之间建立创新的合作，该机构主要负责培训内华达州大部分农村地区的科学教育者。首席调查员的教育外展将重点介绍三个主要目标； （1）创建并制作广泛可用的互动实地旅行指南和教程，重点介绍了研究以及众多基本地球科学概念，这些概念可以在拟议的研究领域中证明； （2）为整个内华达州的大盆地大学校园创建永久性和移动展示； （3）在各个层面上为学习者创建学习模块和教程，包括参加地质课程，传统大学生和准备成为K-12教育者的教育学生的双学分高中生。外展材料将强调内华达州东北部构造历史在其公民的身体和经济福祉中发挥的核心作用。这项研究的技术结果将通过专业地球科学会议和同行评审的科学文献进行广泛传播。北美构造建筑中最急剧的转变之一是白垩纪已晚白垩纪，从大规模缩短和地壳增厚到广泛的区域扩散量崩溃。尽管这一地质历史的某些方面是充分理解的，但关于早期扩展进化的分布，速率，风格和时机仍未解决关键问题。解决这些关键问题的关键是变质核心复合物 - 极端地壳延伸的区域将厚实的地壳切片带有延伸的构造历史。但是，东北大盆地的每一个经典的变质核心复合物在根本上产生了对时序和构造意义的解释，这取决于数据是从更深层次还是较浅的结构水平中得出的。在每种情况下，主要来自较高温度的热态计，综合压力温度路径以及中壳至深层岩石的结构分析的证据线表明，较旧，更长时间且较为持久且通常更复杂的挖掘历史；相比之下，低温的热塑料计和含义沉积通常记录了更简单，更年轻的中新世扩展不盖式的记录。这项研究将直接解决这些问题，并通过使用低温和中温度（铀）/氦气和40argon/39argon/39argon的热量照相框架来限制详细且富有良好的结构框架，以限制北部内华达州北部型卢比山脉 - 东蜂山（East Humboldt fromsil）的完整冷却和挖掘的历史，弥合了当前的理解差距。通过整合一系列热化学计和现场关系，这项研究将调和源自对深壳和上壳过程的脱节研究得出的不同挖掘历史。这样一来，它将直接测试盆地，范围扩展和挖掘的发作，持续时间和驱动力的竞争假设。 Specifically, this proposal will address three key questions: (1) when did extension initiate in the Ruby Mountains - East Humboldt Range - Wood Hills metamorphic core complexes, (2) how did the crustal geotherm evolve during the Cretaceous to present, and (3) if early phases of extension occurred, why did they fail to produce a syntectonic stratigraphic record?