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?

美国西部山区，通常被称为科迪勒拉山脉，在过去的几亿年里经历了近乎持续的地质变形和重组。大山脉被创造和摧毁，火山活动爆发和消失，西部的一大片地区，基本上从犹他州盐湖城到内华达州里诺，由于地球的极端拉伸和延伸，其面积大约增加了一倍。上地壳。这个广阔的地区，即盆岭省，一直是地球科学家和探矿者几十年来研究和勘探的焦点，现在拥有北美一些最大的矿藏。尽管多年来使用各种方法进行了研究，但关于驱动扩展的机制的基本问题仍然存在。这些争论的核心是变形的时间和速度。从根本上来说，来自地壳不同深度的证据会产生不同的解释，来自较深层地球的证据记录了更古老的白垩纪（大约 7000 万年前）变形，而对较浅地壳的研究则强调了后来的中新世（大约 1500 万年前）过程。 。本研究旨在弥合这两个数据集之间的差距，并通过关注红宝石山脉 - 东洪堡山脉 - 伍德山变质核心复合体（内华达州东北部的一个地区）中异常暴露的地壳部分来协调这些看似不同的历史。由于其位于北美最富有的黄金生产省份的中心地带，因此也具有巨大的经济利益。构成这些山脉的岩石代表了地壳的厚柱，在伸展过程中被带到地表并在其一侧倾斜，并为跨越多个地壳层面的地质过程提供了前所未有的视角。一套相对较新的同位素测年技术将记录岩石的时间-温度历史，从而记录构造隆升的完整历史。这项研究期间进行的研究将通过对本科生进行重要的 STEM（科学、技术、工程和数学）学科培训来提供重要的社会成果，从而为培养具有全球竞争力的劳动力做出贡献。该项目还将有助于提高科学素养和公众对 STEM 的参与。该项目包含大量的外展和教育内容。研究区域的世界级地质学通过对当地科学教育者和地球科学专业人士进行战略性和全面的宣传，为直接社区参与提供了理想的舞台。通过在两个 R1 研究机构和大盆地学院（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工作者）之间建立创新合作。首席研究员的教育推广将集中于三个主要目标； (1) 创建并广泛提供交互式实地考察指南和教程，重点关注研究以及可在拟议研究领域展示的众多基本地球科学概念； (2) 为内华达州的大盆地学院校园创建永久和移动显示屏； (3) 为不同层次的学习者创建学习模块和教程，包括参加地质学课程的双学分高中学生、传统大学生以及准备成为 K-12 教育工作者的教育学生。宣传材料将强调内华达州东北部的构造历史对其公民的身体和经济福祉所发挥的核心作用。研究的技术成果将通过在专业地球科学会议上的演讲和同行评审的科学文献来广泛传播。北美显生宙构造结构最显着的转变之一是科迪勒拉山脉从晚白垩世到新生代的过渡，从大规模缩短和地壳增厚到广泛的区域性伸展塌陷。虽然这段地质历史的某些方面已得到很好的了解，但有关早期伸展演化的分布、速率、风格和时间的关键问题仍未得到解决。解决这些关键问题的关键是变质核复合体，即极端地壳伸展暴露出具有长期构造历史的厚地壳部分的区域。然而，大盆地东北部的每个经典变质核杂岩体对折返的时间和构造意义产生了根本不同的解释，具体取决于数据是来自更深还是更浅的构造水平。在每种情况下，主要来自高温热测时法、综合压力-温度-时间路径以及中深层地壳岩石的结构分析的证据表明，剥露历史更古老、更持久且往往更复杂；相比之下，低温热测时法和同构造沉积通常记录了中新世广泛的伸展剥落的更简单、更年轻的记录。这项研究将直接解决这些问题，并通过在详细且易于理解的结构框架内使用低温和中温（铀-钍）/氦和 40Argon/39Argon 热年代学来弥补当前的理解差距，以限制完整的冷却和折返。历史上为内华达州东北部的红宝石山脉-东洪堡山脉-伍德山变质核杂岩。通过整合一系列测温仪和现场关系，这项研究将协调源自深地壳和上地壳过程的互不相关研究的不同掘出历史。在此过程中，它将直接检验关于盆地和山脉延伸和折返的开始、持续时间和驱动力的竞争假设。具体来说，该提案将解决三个关键问题：(1) 红宝石山脉 - 东洪堡山脉 - 伍德山变质核复合体何时开始伸展，(2) 白垩纪期间地壳地温是如何演化到现在的，以及 (3) ）如果发生了早期伸展阶段，为什么他们未能产生同构造地层记录？