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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

基本信息

批准号：
1728537
负责人：
James Metcalf
金额：
$ 14.73万
依托单位：
University of Colorado at Boulder
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 2023-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1728537&HistoricalAwards=false
关键词：
Collaborative Research Documenting transition contraction

项目摘要

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?

多山的美国西部，通常被称为科迪勒拉，在过去的几亿年中经历了几乎不断的地质变形和重组。巨大的山脉被创造和摧毁，火山活动爆发和消失，西部的一大片地区，基本上从犹他州的盐湖城到内华达州的里诺，由于地球上地壳的极端拉伸和延伸，面积大约翻了一番。这个延伸的地区，盆地和山脉省，几十年来一直是地球科学家和勘探者研究和勘探的重点，现在拥有北美一些最大的矿藏。尽管多年来使用了各种各样的方法进行了调查，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。从根本上说，来自不同地壳深度的证据产生了不同的解释，来自更深的地球的证据记录了更早的白垩纪（大约7000万年前）的变形，而对较浅地壳的研究则强调了晚些时候的中新世（大约1500万年前）的过程。这项研究建议通过关注红宝石山脉-东洪堡山脉-伍德山变质核复杂岩的一个异常暴露的地壳部分来弥合这两个数据集之间的差距，并调和这些看似不同的历史，该地区位于内华达州东北部，由于其位于北美最富有的黄金生产省的中心，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向一侧倾斜，这为研究跨多个地壳水平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定年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。在本研究期间进行的研究将通过培养重要的STEM（科学、技术、工程和数学）学科的本科生，从而为培养具有全球竞争力的劳动力做出贡献，从而提供重要的社会成果。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联和教育内容。研究区的世界级地质条件为社区直接参与提供了一个理想的舞台，通过对当地科学教育工作者和地球科学专业人员进行战略性和全面的推广。通过两家R1研究机构和大盆地学院之间的创新合作，该学院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。首席研究员的教育推广将集中在三个主要目标上；(1)创建并广泛提供互动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础地球科学概念；(2)为内华达州的大盆地学院校园创建永久性和可移动的显示器；(3)为不同层次的学习者创建学习模块和教程，包括参加地质课程的双学分高中生、传统大学生和准备成为K-12教育工作者的教育学生。外展材料将突出内华达州东北部的构造历史在其公民的身体和经济福祉中发挥的核心作用。这项研究的技术成果将通过专业地球科学会议的报告和同行评议的科学文献广泛传播。北美显生宙构造结构中最引人注目的变化之一是晚白垩世到新生代科迪勒拉从大规模缩短和地壳增厚到广泛的区域伸展塌陷的转变。虽然这段地质历史的某些方面已经得到了很好的理解，但关于早期伸展演化的分布、速率、样式和时间等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杂岩——在这些区域，地壳的极端伸展暴露出具有漫长构造历史的厚地壳剖面。然而，大盆地东北部的每一个经典变质岩心杂岩对挖掘的时间和构造意义产生了根本不同的解释，这取决于数据是来自较深还是较浅的构造水平。在每一种情况下，主要从高温热时计、综合压力-温度-时间路径和地壳中深部岩石的结构分析中获得的证据表明，挖掘历史更古老、更漫长，往往也更复杂；相比之下，低温温度测年法和同构造沉积法通常记录的是更简单、更年轻的广泛中新世伸展拆顶记录。本研究将直接解决这些问题，并通过在详细且已被充分理解的结构框架内使用低温和中温（铀-钍）/氦和40Argon/39Argon热年代学来限制内华达州东北部红宝石山脉-东洪堡山脉-伍德山变质岩心复合物的完整冷却和挖掘历史，弥合目前在理解上的差距。通过整合一系列的温度表和野外关系，本研究将调和从地壳深部和地壳上层过程的不相关调查中得出的不同的挖掘历史。在这样做的过程中，它将直接测试关于盆地和山脉扩展和挖掘的开始、持续时间和驱动力的相互竞争的假设。具体来说，本文将解决三个关键问题：(1)红宝石山-东洪堡山脉-伍德山变质核杂岩的伸展是何时开始的；(2)白垩纪至今的地壳地热是如何演变的；(3)如果早期伸展发生过，为什么它们没有产生同构造地层记录？