Collaborative Research: "SUPERERUPTIONS," MAGMA CHAMBERS, & PLUTONIC RESIDUE: Insights from Peach Spring Tuff, Significance of Sphene

合作研究：“超级爆发”，岩浆室，

• 批准号: 0911726
• 负责人: Calvin Miller
• 金额: $ 34.75万
• 依托单位: Vanderbilt University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911726&HistoricalAwards=false
• 关键词: Collaborative; Research; SUPERERUPTIONS; MAGMA; CHAMBERS

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Intellectual merit: "Super-eruptions" - explosive eruptions that produce 450 km3 of magma -arguably are the most catastrophic of all natural processes on Earth. They play a central role in ongoing debates about the nature of crustal magmatism. Study of super-eruptions may illuminate [1] the processes by which large quantities of magma accumulate in the upper crust, are stored and modified, and erupt; [2] the relations between intrusive and extrusive igneous rocks; and [3] the construction of plutons and batholiths. We propose a multi-faceted approach to investigate the generation and eruption of the 600 km3 Peach Spring Tuff (PST: Miocene, Arizona-California-Nevada). Exposure of the extensive outflow sheet as well as a thick intracaldera tuff section and related granite makes this a particularly appealing target for study. The PST phenocryst assemblage comprises a diverse array of accessory minerals, notably including abundant sphene (titanite), which plays a vital role in both recording evolving conditions and driving trace element variation. Critical questions to be addressed include: [1] What environmental factors control occurrence of key accessory minerals - especially sphene? [2] How does growth of accessories influence geochemical signatures of magmas - and how can these signatures be used to characterize evolution of magmatic environments? [3] What are the conditions in giant chambers immediately prior to super-eruptions? [4] How much do conditions fluctuate, and are they a direct response to replenishment, eruption, or wholesale contamination? [5] How long do large systems last, and during how much of their lifetime is there a large chamber? [6] Are chambers containing super-volumes of eruptible magma inherently unstable, or is triggering suppressed for unusual lengths of time to permit accumulation of enormous quantities of magma? [7] How, and how efficiently, are large volumes of melt-rich magma extracted from crystal-rich residue? [8] How and where are highly-evolved, high-silica rhyolites generated? [9] What is the significance of similarities and differences between felsic intrusive and extrusive rocks? [10] Why are highly evolved plutonic rocks less voluminous than volcanic equivalents? [11] Do giant eruptions have a different relation to their residual plutonic equivalents than 'normal'-sized eruptions? Are their chambers far larger, or do they more efficiently extract the eruptible material?This project will entail an integrated, multi-disciplinary approach involving PIs and collaborators with diverse expertise and perspectives. The project will combine extensive field work, elemental and isotopic analyses of rock, glass, mineral, and melt inclusion samples, dating using several complementary geochronological methods, quantitative textural investigations, and experimental studies aimed at elucidating the stability and saturation behavior of sphene. We will employ, among other methods, high-resolution SIMS, CA-TIMS, LA-ICPMS, imaging by X-ray tomography as well as CL and BSE, and piston cylinder and cold seal experimental procedures.Broader impacts: This project will provide research training for 5 graduate students (one PhD, 4 MS) and 7-8 undergraduate students leading to publishable contributions in petrology, geochemistry, and tectonics. A large proportion of these students will be female (and possibly minority students, especially at San Jose State). The proposed collaboration involves junior and senior faculty PIs at private and public universities (Vanderbilt, SJSU) and collaborators affiliated with government-university partnerships (AZ Geological Survey- UAZ; USGS-Stanford; NM Bureau of Geology-NM Tech). Other less formal participants include undergraduate and graduate students and faculty from a wide range of institutions who will provide valuable perspectives on the diverse problems that are to be addressed. Scientific results will be incorporated into teaching modules at the respective universities. Although this is principally a basic science project, the results will bear upon two issues of societal importance: behavior of giant systems that may produce catastrophic eruptions, and possible relationship between such systems and major gold deposits

“这项奖励是根据2009年美国复苏和再投资法案（公法111-5）资助的。”学术价值：“超级喷发”——产生450立方千米岩浆的爆炸性喷发——可以说是地球上所有自然过程中最具灾难性的。它们在正在进行的关于地壳岩浆活动性质的辩论中发挥着核心作用。对超级喷发的研究可以阐明大量岩浆在上地壳中积聚、储存、变质和喷发的过程；[2]侵入岩与喷出火成岩的关系；以及深部岩和岩基的构造。我们提出了一个多角度的方法来研究600 km3桃泉凝灰岩（PST：中新世，Arizona-California-Nevada）的形成和喷发。广泛的流出层以及厚的破壳内凝灰岩剖面和相关花岗岩的暴露使其成为一个特别吸引人的研究目标。PST斑晶组合包含多种辅助矿物，特别是丰富的榍石（钛矿），在记录演化条件和驱动微量元素变化方面起着至关重要的作用。需要解决的关键问题包括：什么样的环境因素控制着关键辅助矿物（尤其是榍石）的发生？附件的生长如何影响岩浆的地球化学特征，以及这些特征如何用于描述岩浆环境的演化？在超级喷发之前，巨大的洞穴里的条件是什么？情况波动有多大？它们是对补给、喷发或大规模污染的直接反应吗？[5]大型系统能持续多久，在它们的生命周期中有多少时间是有一个大的腔室？是含有大量可喷发岩浆的岩浆室本身就不稳定，还是触发被抑制了异常长的时间，以允许大量岩浆的积累？如何从富含晶体的残留物中提取大量富含熔体的岩浆，以及提取效率如何？高度演化的高硅流纹岩是如何以及在哪里形成的？长英质侵入岩与喷出岩的异同有何意义？为什么高度演化的深成岩比同等的火山岩体积小？与“正常”规模的火山爆发相比，巨型火山爆发与其残余的深部当量有不同的关系吗？是它们的腔室大得多，还是它们能更有效地提取可喷发物质？该项目将需要一个综合的、多学科的方法，涉及pi和具有不同专业知识和观点的合作者。该项目将结合广泛的野外工作，对岩石、玻璃、矿物和熔融包裹体样品进行元素和同位素分析，使用几种互补的地质年代学方法测定年代，定量结构调查，以及旨在阐明榍石稳定性和饱和行为的实验研究。除其他方法外，我们将采用高分辨率SIMS， CA-TIMS, LA-ICPMS， x射线断层扫描成像以及CL和BSE，以及活塞缸和冷密封实验程序。更广泛的影响：该项目将为5名研究生（1名博士，4名硕士）和7-8名本科生提供研究培训，在岩石学，地球化学和构造学方面发表论文。这些学生中很大一部分将是女性（可能还有少数民族学生，特别是在圣何塞州立大学）。拟议的合作涉及私立和公立大学（Vanderbilt， SJSU）的初级和高级教师pi，以及隶属于政府-大学合作伙伴关系的合作者（AZ地质调查局- UAZ，美国地质勘探局-斯坦福大学，NM地质局-NM技术）。其他不太正式的参与者包括来自广泛机构的本科生、研究生和教师，他们将就将要解决的各种问题提供有价值的观点。科学成果将被纳入各自大学的教学模块。虽然这主要是一个基础科学项目，但其结果将对两个具有社会重要性的问题产生影响：可能产生灾难性喷发的巨型系统的行为，以及这些系统与主要金矿床之间的可能关系