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

“该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。“智力优点：“超级喷发”-产生450立方公里岩浆的爆炸性喷发-可以说是地球上所有自然过程中最具灾难性的。它们在关于地壳岩浆活动性质的持续争论中发挥着核心作用。对超级喷发的研究可以阐明[1]大量岩浆在上地壳中积聚、储存、改造和喷发的过程; [2]侵入和喷出火成岩之间的关系;[3]深成岩和岩基的构造。我们提出了一个多方面的方法来调查600 km 3的桃泉凝灰岩（太平洋标准时间：中新世，亚利桑那州-加利福尼亚州-内华达州）的生成和喷发。广泛的外流片以及厚的intracaldera凝灰岩部分和相关的花岗岩的曝光，使这一研究特别有吸引力的目标。PST斑晶组合包括一系列不同的副矿物，特别是包括丰富的黑云母（钛铁矿），它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：[1]哪些环境因素控制着关键副矿物的出现-特别是异戊烯？ [2]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表征岩浆环境的演化？[3]在超级爆发之前，巨大的房间里的条件是什么？[4]条件波动有多大，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，在它们的寿命中有多少时间是一个大的腔室？[6]含有超大体积可喷发岩浆的岩浆库是否天生就不稳定，或者是否在异常长的时间内抑制了触发，以允许大量岩浆的积累？[7]大量富含熔融物的岩浆是如何从富含晶体的残留物中提取出来的？[8]高度进化的高硅质流纹是如何以及在何处产生的？[9]长英质侵入岩和喷出岩的异同有什么意义？[10]为什么高度演化的深成岩的体积小于火山岩？[11]巨型火山喷发与其残余的深成当量之间的关系是否与“正常”规模的火山喷发不同？是它们的腔室大得多，还是它们更有效地提取了可喷发的物质？这个项目将需要一个综合的，多学科的方法，涉及PI和合作者具有不同的专业知识和观点。该项目将结合联合收割机广泛的实地工作，岩石，玻璃，矿物和熔融包裹体样品的元素和同位素分析，使用几种互补的地质年代学方法，定量结构调查和实验研究，旨在阐明的稳定性和饱和度行为。我们将采用高分辨率西姆斯，CA-TIMS，LA-ICPMS，X射线断层成像以及CL和BSE，活塞缸和冷密封实验程序等方法。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，从而在岩石学，地球化学和构造学方面做出贡献。这些学生中有很大一部分是女生（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（范德比尔特，SJSU）的初级和高级教师PI以及与政府-大学合作伙伴关系（AZ地质调查局- UAZ; USGS-斯坦福大学; NM地质局-NM技术）有关的合作者。其他不太正式的参与者包括来自广泛机构的本科生和研究生以及教职员工，他们将就有待解决的各种问题提供宝贵的观点。科学成果将纳入各大学的教学单元。虽然这主要是一个基础科学项目，但其结果将涉及两个具有社会重要性的问题：可能产生灾难性喷发的巨型系统的行为，以及此类系统与主要金矿之间的可能关系

"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