Collaborative Research: Investigating Magmatic Differentiation in a Fossil Upper-Crustal Silicic Magma System: Stillwater Range, NV

合作研究：调查化石上地壳硅质岩浆系统的岩浆分异：内华达州斯蒂尔沃特山脉

• 批准号: 2006254
• 负责人: Joel DesOrmeau
• 金额: $ 12.05万
• 依托单位: Board of Regents, NSHE, obo University of Nevada, Reno
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-15 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2006254&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Magmatic; Differentiation

Volcanic eruptions involving high-silica rhyolite magmas are explosive, violent, and have high hazard potential. Yet, there remain significant debates as to how these magmas are generated and when and why they erupt. Understanding the processes and timescales related to these questions is key to developing effective volcanic hazard programs and requires an understanding of how the physical and thermal conditions of a magmatic system change over timescales ranging from days to millions of years. Efforts focused on monitoring and imaging the subsurface at active volcanoes can provide some of this information, but they cannot inform on processes that occur on very long timescales (thousands to million years). Consequently, research on systems where both erupted and non-erupted portions of the magmatic system are preserved can be used to better understand the entire history of a volcanic system. The goal of this project is to study a ‘fossil’ magmatic system – the IXL pluton (Nevada) –in an effort to constrain the processes that lead to the generation, and possible eruption, of high-silica rhyolite magma. Funding will support two graduate and three undergraduate students from Purdue University, Stanford University, and the University of Nevada-Reno. An additional important outcome of this work will be the production of a student-led documentary that will highlight the research, with an emphasis on women conducting field-based scientific research. This will be done through collaboration with the Science Communication Hitchcock Project within the Reynolds School of Journalism at the University of Nevada-Reno and will result in the dissemination of this research to the general public in an engaging fashion.Most of the proposed mechanisms for production of high-silica rhyolite involve its separation from a crystal-rich magma reservoir through gravitationally driven processes like crystal settling and compaction. Importantly, both processes should produce vertical geochemical and textural gradients in magma reservoirs. The Miocene IXL pluton offers an ideal location to document these gradients because it is well exposed in a coherent crustal section with a known paleo-vertical orientation. To assess whether these gradients are present, the PIs will utilize high-density geochemical measurements coupled with electron back scattered diffraction (EBSD) textural studies and constrain the timescales over which they occurred using high-precision U-Pb zircon geochronology. Additionally, U-Pb zircon geochronology, diffusion chronometry, and geochemical studies will be used to determine whether any of the overlying volcanic rocks are related to the pluton and to assess the magmatic processes that led to their eruption. The combination of these techniques will provide a holistic view of silicic magma evolution in the upper crust and can be used to better interpret the geophysical data that is used to assess volcanic hazards at modern volcanoes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

涉及高硅流纹岩岩浆的火山喷发是爆炸性的，猛烈的，具有很高的危险性。然而，关于这些岩浆是如何产生的，何时以及为什么爆发，仍然存在重大争议。了解与这些问题相关的过程和时间尺度是制定有效的火山灾害计划的关键，需要了解岩浆系统的物理和热条件如何在从几天到数百万年的时间尺度上变化。专注于对活火山地下进行监测和成像的努力可以提供其中的一些信息，但它们无法提供有关很长时间尺度（数千到数百万年）上发生的过程的信息。因此，对岩浆系统的喷发和未喷发部分都保存下来的系统的研究可以用来更好地了解火山系统的整个历史。该项目的目标是研究一个“化石”岩浆系统-IXL岩体（内华达州）-努力限制导致高硅流纹岩岩浆生成和可能喷发的过程。资金将支持来自普渡大学、斯坦福大学和内华达大学里诺分校的两名研究生和三名本科生。这项工作的另一个重要成果是制作一部由学生主导的纪录片，突出介绍这项研究，重点是妇女进行实地科学研究。这将通过与内华达大学雷诺新闻学院内的科学传播希区柯克项目的合作来完成，并将导致以一种引人入胜的方式向公众传播这项研究。大多数提出的高硅流纹岩生产机制涉及通过重力驱动的过程，如晶体沉降和压实，从富含晶体的岩浆库中分离出来。重要的是，这两个过程应该产生垂直的地球化学和结构梯度的岩浆库。中新世IXL岩体提供了一个理想的位置来记录这些梯度，因为它是一个已知的古垂直方向的连贯的地壳部分，以及暴露。为了评估这些梯度是否存在，PI将利用高密度地球化学测量加上电子背散射衍射（EBSD）纹理研究，并使用高精度U-Pb锆石地质年代学来限制它们发生的时间尺度。此外，U-Pb锆石地质年代学、扩散测年和地球化学研究将用于确定上覆火山岩是否与该岩体有关，并评估导致其喷发的岩浆过程。这些技术的结合将提供一个整体的观点，岩浆演化在地壳上部，并可用于更好地解释地球物理数据，用于评估火山灾害在现代volcanoes.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用该基金会的智力价值和更广泛的影响审查标准。