Evolution of Cordilleran Lithosphere: Transition From Mesozoic Shortening to Cenozoic Extension, East-Central Nevada

内华达州中东部科迪勒拉岩石圈的演化：从中生代缩短到新生代伸展的转变

• 批准号: 1322084
• 负责人: Elizabeth Miller
• 金额: $ 9.22万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1322084&HistoricalAwards=false
• 关键词: Evolution; Cordilleran; Lithosphere; Transition; Mesozoic

The geologic history of the western U. S. Cordilleran is complex and an increasing number of questions have been raised about its deep crustal architecture. The most debated question is how its geology was shaped during the transition from plate convergence and crustal shortening in the Mesozoic to divergence and extension in the Cenozoic. Across today's Basin and Range Province, this transition period is characterized by shallow-slab subduction and the shut-off of arc magmatism ~ 70-50 m.y. ago followed by one of the biggest volcanic eruption events in its history, ~ 45-20 m.y. ago, setting the stage for Miocene Basin and Range faulting. This research focuses on placing better absolute ages on events occurring during this transition period across the central part of the Basin and Range province (east-central Nevada and adjacent Utah) in order to address current controversies about this history and produce a more holistic whole-crust model for this time-span. A multidisciplinary and comprehensive approach will mesh: 1. A pioneering effort to detail the U-Pb radiometric ages, trace element and isotopic geochemistry of xenocrystic/inherited zircon populations in magmatic rocks that span the transition from shortening to extension, revealing the temperature-time history of the deep crust 2. Structural/ microstructural studies coupled with petrology, geochronology and thermochronology of key rock transects that link inferred deep levels of the crust to near surface levels in the Snake Range metamorphic core complex- a locality where deformation and cooling histories figure prominently in the debate between very thick versus thinner crust and its role in crustal flow and collapse during the transition period. 3. The time-space evolution of sedimentary basins whose history provides a robust, definitive set of constraints for evolving landforms, their relation to volcanic eruptins, and the onset of fault uplift of the deeper rocks of core complexes. This comprehensive approach will allow us to better link deep lithospheric/crustal processes such as magmatism and deformation/flow to surface processes and thus provide data to test a range of ideas and hypotheses about the lithospheric evolution of the Great Basin as it transitioned from shortening to extension. Our geologic knowledge of the Cordillera and Rocky Mountains of the western U.S. forms the foundation for understanding its broad spectrum of natural resources, yet there are many aspects of the history of this mountain belt that are still highly debated and controversial. One of these is our conceptual understanding of fault systems formed during stretching or extension of continental crust (such as is happening today across the Basin and Range province). Despite the importance of such fault systems to the exploration of natural resources such as groundwater and hydrocarbons in continental and offshore basins, there is no consensus on how their geometries evolve through time. We also don't fully understand how surface-breaking extensional faults are linked to processes in the deep earth such as magmatic activity, heating and solid-state ductile flow of the crust, despite the importance of these questions to mineral resource exploration, hydrothermal energy sources, earthquake and volcanic hazards. Our research goals are to provide a more comprehensive data set that provides radiometric dating of events from the deep crust to surface breaking faults, volcanic eruption and sedimentary basins in order to understand the time-constrained links between deep earth processes and surface events during a time span where the Cordillera transitioned from plate tectonic convergence and shortening to divergence and extension from ~ 80 Ma to 20 Ma ago. This project will provide partial support for field and laboratory work of 3 Ph.D. and one M.S. student(s) contributing to professional training of future earth scientists. The project provides leverage to obtain funding for undergraduate research from Stanford. Compilation of geologic map data at 1:62,500 spanning the Great Basin National Park to the Kern Mountains will be made available to the general public. This map will stimulate new research and benefit teaching of geology field classes and field trips in this region.

美国西部的地质历史。S.科迪勒拉是复杂的，越来越多的问题已经提出了关于其深部地壳结构。最有争议的问题是它的地质是如何形成的，从中生代的板块会聚和地壳缩短到新生代的扩张和伸展。 在今天的盆岭省，这一过渡时期的特点是浅板俯冲和弧岩浆活动的关闭~ 70-50百万年。45-20百万年前发生了历史上最大的火山爆发事件之一。为中新世盆地和山脉断裂奠定了基础。 本研究的重点放在放置更好的绝对年龄发生在这一过渡时期的盆地和山脉省中部（中东部内华达州和邻近的犹他州），以解决目前的争议，这段历史，并产生一个更全面的全地壳模型的时间跨度。 一个多学科和全面的方法将啮合：1。详细描述了岩浆岩中捕虏晶/继承锆石群的U-Pb放射性年龄、微量元素和同位素地球化学的开创性努力，这些岩浆岩跨越了从缩短到伸展的过渡，揭示了地壳深部的温度-时间历史2。 结构/微结构研究，加上岩石学、地质年代学和关键岩石断面的热年代学，这些断面将推断的地壳深层与蛇岭变质核杂岩的近地表联系起来，蛇岭变质核杂岩是一个变形和冷却历史在地壳很厚还是很薄及其在过渡期地壳流动和坍塌中的作用的辩论中占有突出地位的地方。 3. 沉积盆地的时空演化，其历史为地貌的演化、它们与火山爆发的关系以及核杂岩的深层岩石的断层隆起的开始提供了一套强有力的、确定的约束条件。这种全面的方法将使我们能够更好地联系深部岩石圈/地壳过程，如岩浆作用和变形/流动的表面过程，从而提供数据，以测试一系列的想法和假设的岩石圈演变的大盆地，因为它从缩短过渡到延伸。 我们对美国西部的科迪勒拉山脉和落基山脉的地质知识构成了了解其广泛自然资源的基础，但这条山脉的许多历史方面仍然存在高度争议和争议。其中之一是我们对大陆地壳伸展或延伸过程中形成的断层系统的概念性理解（例如今天发生在盆地和山脉省的断层系统）。尽管这种断层系统对大陆和近海盆地的地下水和碳氢化合物等自然资源的勘探具有重要意义，但对于它们的几何形状如何随着时间的推移而演变却没有达成共识。 我们也不完全了解地表断裂的伸展断层如何与地球深部的过程联系在一起，例如岩浆活动，地壳的加热和固态韧性流动，尽管这些问题对矿产资源勘探，热液能源，地震和火山灾害非常重要。 我们的研究目标是提供一个更全面的数据集，提供从地壳深部到地表断裂断层的事件的放射性测年，火山爆发和沉积盆地，以了解在时间跨度内，科迪勒拉从板块构造会聚和缩短到发散和伸展的时间跨度内，地球深部过程和地表事件之间的时间约束联系约80至20 Ma前。 该项目将为3名博士的野外和实验室工作提供部分支持。 一个MS为未来地球科学家的专业培训做出贡献的学生。 该项目为从斯坦福大学获得本科研究资金提供了杠杆。 将向公众提供从大盆地国家公园到克恩山脉的1：62 500地质图数据汇编。 这幅地图将促进新的研究，并有利于该地区的地质野外教学和实地考察。