Collaborative Research: Using K-feldspar megacryst and mineral inclusion T-X-t histories to assess batholith growth and evolution in the Tuolumne intrusive complex, CA

火山是众所周知的，但人们对它知之甚少。岩浆是如何在活火山下形成的，需要多长时间才能形成？是什么控制着它是在地下深处喷发还是冷却形成深成岩？它在那里熔化多久，其中有多少是可喷发的？数以亿计的人生活在活火山周围100英里内。他们面临着暴露在火山灾害中的风险。火山喷发也会影响气候和环境。然而，几十年的研究并没有回答这些基本问题中的一些。这个项目将在Tuolumne岩体中解决这些问题。它是约塞米蒂国家公园壮观的岩石裸露之地。小型矿物的铀-铅年龄将决定这些钚何时冷却为今天暴露在地表的岩石。它们还将揭示岩浆存在的持续时间。此外，这些小得多的矿物被发现包含在几英寸大的钾长石晶体中。长石的化学作用就像犯罪现场的指纹。他们将确定9000万年前为火山喷发提供燃料的时间、地点和数量。岩浆的粘性和热度将有助于确定这些喷发可能是什么样子。该项目支持两个研究小组：1)梅梅蒂研究员，一位在西班牙裔服务的、专注于本科生的加州州立大学富勒顿分校的女性研究员，以及2)普林斯顿大学专注于研究的舍内研究员。该团队将对几名研究生进行年龄约会和化学方法方面的培训。研究生帮助培养参与该项目不同部分的本科生。所有学生都参加研究活动的方方面面，包括实地考察和出版。Memeti将完成以下活动：1)根据本项目的结果更新作者的Yosemite Audiotour手机应用程序；2)继续组织到Yosemite国家公园的实地考察；3)与公园护林员分享研究成果。4)她将为地质学专业的学生开发入门地质学实验室，5)继续在南加州公共活动中推广火山灾害。斯库内将在普林斯顿大学的一个研讨会上向当地的K-12教师讲授火山和危险。加州州立大学富勒顿和普林斯顿大学的这项为期3年的RUI合作项目旨在确定岩浆弧中岩浆体的时间和长度尺度，以及它们的成分、结晶度和体积随时间的变化。这项研究将使用长达12厘米的钾长石斑晶和巨晶，以及来自内华达山脉中部95-85.5 Ma图奥伦侵入杂岩的半穹顶和大教堂峰单元的巨晶矿物包裹体。钾长石结构和分带将通过CT扫描和CL图像进行三维成像，并使用电子探针和激光消融ICPMS进行定量分析。钾长石矿物包裹体将被测量TIMS-TEA锆石和钛铁矿年代学，SIMS钛英石和锆英石测温法，EMP和LA-ICPMS斜长石和角闪石测温法和化学计量学(确定熔体成分)。这些数据将被综合起来，以检验这样的假设，即托列侵入杂岩在递增建造过程中热成熟，创造出长达数千公里的相互关联的岩浆体，能够进行岩浆流动、分馏、混合和可能的喷发。这些数据将反映当前的争论，即像图奥伦杂岩这样的长寿和大型复合侵入体的特征是“热”还是“冷”的。“冷”储存的特点是小而硬的岩浆泥，它们大部分时间都在固相线附近或在固相线附近的温度下度过，限制了与同时代岩浆体的相互作用，只有偶尔(如果有的话)通过岩浆补充来“解冻”以促进火山喷发。相比之下，“热存储”允许在大型(10-100平方公里)岩浆体中进行动态的单元间岩浆混合和晶体回收，温度显著高于固相线和较低的结晶度，时间尺度长达数百万年。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。

Volcanoes are well-known but poorly understood. How does magma build up beneath active volcanoes, and how long does it take to do so? What controls whether it erupts or cools deep underground to form plutons? How long does it stay molten there, and how much of it is eruptible for how long? Hundreds of millions of people live within 100 miles of active volcanoes. They are at risk of being exposed to volcanic hazards. Volcanic eruptions also affect climate and the environment. Yet decades of research have not answered some of these basic questions. This project will address these questions in the Tuolumne pluton. It is home to the spectacular rock exposures of Yosemite National Park. Uranium-lead age dates of small minerals will determine when the plutons cooled to the rocks that are exposed at the surface today. They will also reveal the duration of time that magma was present. Additionally these much smaller minerals are found included in several-inch-large potassium feldspar crystals. The chemistry of the feldspars serves like fingerprints in a crime scene. They will determine when, where and how much magma was stored 90 million years ago to feed volcanic eruptions. How sticky and hot magma was will help determine what these eruptions might have looked like. This project supports two research groups: 1) Researcher Memeti, a woman at Hispanic-serving, undergraduate-focused California State University Fullerton, and 2) Researcher Schoene at research-focused Princeton University. The team will train several graduate students in age dating and chemistry methods. Graduate students help train undergraduate students involved in different parts of the project. All students take part in all aspects of research activities including field work and publishing. Memeti will complete following activities: 1) update authored Yosemite audiotour mobile app based on this project’s results, 2) continue to organize field trips to Yosemite National Park, and 3) share research results with park rangers. 4) She will develop introductory geology labs for geology students, and 5) continue her outreach efforts on volcanic hazards at southern California public events. Schoene will teach local K-12 teachers on volcanoes and hazards in a seminar at Princeton University. This 3-yr collaborative RUI project between California State University Fullerton and Princeton University seeks to determine the time and length scales of magma bodies in magmatic arcs and their changes in composition, crystallinity, and volume over time. The study will use K-feldspar pheno- and megacrysts up to 12 cm long and megacryst-hosted mineral inclusions from the Half Dome and Cathedral Peak units of the 95-85.5 Ma Tuolumne intrusive complex in the central Sierra Nevada. K-feldspar textures and zoning will be imaged in 3D with CT scans and CL images and quantitatively analyzed with electron microprobe and laser ablation ICPMS for geochemistry. K-feldspar mineral inclusions will be measured for TIMS-TEA U-Pb zircon and titanite geochronology, SIMS Ti-in-zircon and Zr-in-titanite thermometry, and EMP and LA-ICPMS plagioclase and hornblende thermometry and chemometry (determining melt compositions). These data will be synthesized to test the hypotheses that the Tuolumne intrusive complex matured thermally during incremental construction, creating interconnected magma bodies many kilometers in length, capable of magma flow, fractionation, mixing, and likely eruption. These data will reflect on current debates about whether long-lived and large composite intrusions like the Tuolumne complex are characterized by “hot” or “cold” storage. “Cold” storage is characterized by small, rigid magma mushes that spend most of their time at temperatures near or at the solidus, limiting interaction with coeval magma bodies, only occasionally, if ever, “defrosting” by magma recharge to feed volcanic eruptions. In contrast, “hot storage” allows for dynamic inter-unit magma mixing and crystal recycling in large (10-100s of square kilometers) magma bodies at significantly higher temperatures above the solidus and lower crystallinities and at time scales of up to millions of years.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.