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

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，以及它们何时喷发和为什么喷发，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方案的关键，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。侧重于监测和成像活火山地下的工作可以提供其中一些信息，但它们不能提供发生在非常长的时间尺度(数千年到100万年)的过程。因此，对岩浆系统中已喷发和未喷发部分都被保存下来的系统的研究可以用来更好地理解火山系统的整个历史。该项目的目标是研究一种“化石”岩浆系统--内华达州的IXL岩体--以限制导致高硅质流纹岩岩浆产生和可能喷发的过程。资金将支持普渡大学、斯坦福大学和内华达大学雷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将是制作一部由学生主导的纪录片，突出这项研究，重点是妇女进行实地科学研究。这将通过与内华达-雷诺大学雷诺兹新闻学院的科学传播希区柯克项目合作完成，并将导致这项研究以一种引人入胜的方式向公众传播。大多数拟议的高硅流纹岩生产机制涉及通过重力驱动过程从富含晶体的岩浆储集层分离，如结晶沉淀和压实。重要的是，这两个过程都应该在岩浆储集层中产生垂直的地球化学和结构梯度。中新世IXL岩体提供了记录这些梯度的理想位置，因为它很好地暴露在一个连贯的地壳剖面上，具有已知的古垂直方向。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结合电子背散射衍射(EBSD)结构研究，并使用高精度的U-Pb锆石年代学来限制它们发生的时间尺度。此外，还将利用U-Pb锆石年代学、扩散计时和地球化学研究来确定上覆的火山岩是否与该岩体有关，并评估导致它们喷发的岩浆过程。这些技术的结合将提供上地壳硅质岩浆演化的整体观点，并可用于更好地解释用于评估现代火山火山灾害的地球物理数据。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.