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作用性质的持续争论中起着核心作用。对超级喷发的研究可以阐明：[1]大量岩浆在地壳上部积聚、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研究600 km3的桃泉凝灰岩（PST：中新世，亚利桑那州-加利福尼亚州-内华达州）的生成和破坏。广泛的外流席，以及厚的intracaldera凝灰岩部分和相关的花岗岩暴露，使这一研究特别有吸引力的目标。PST斑晶组合中含有丰富的副矿物，其中尤以富钛辉石（Titanite）为主，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]什么样的环境因素控制着关键副矿物的出现，特别是异戊烯？[2]副产物的生长如何影响岩浆的地球化学特征--这些特征又如何用来描述岩浆环境的演化？[3]超级火山爆发前巨室的条件是什么？[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，有多少时间是大腔室？[6]含有超大体积可喷发岩浆的岩浆室是不稳定的，还是在异常长的时间内抑制触发以阻止大量岩浆的积累？[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比火山岩体积小？[11]巨型喷发与其残余的深成当量的关系是否不同于"正常"规模的喷发？是它们的腔室大得多，还是它们更有效地提取可喷发的物质？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。该项目将结合广泛的实地工作，岩石，玻璃，矿物和熔体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来确定年代，旨在阐明乌洛托品的稳定性和饱和行为。除其他方法外，我们将采用美国科学基金会提案摘要提案：0911726 PI姓名：米勒，卡尔文打印自

"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 ofmagma -arguably are the most catastrophic of all natural processes on Earth. They playa central role in ongoing debates about the nature of crustal magmatism. Study ofsuper-eruptions may illuminate [1] the processes by which large quantities of magmaaccumulate in the upper crust, are stored and modified, and erupt; [2] the relationsbetween intrusive and extrusive igneous rocks; and [3] the construction of plutons andbatholiths. We propose a multi-faceted approach to investigate the generation anderuption of the 600 km3 Peach Spring Tuff (PST: Miocene,Arizona-California-Nevada). Exposure of the extensive outflow sheet as well as a thickintracaldera tuff section and related granite makes this a particularly appealing target forstudy. The PST phenocryst assemblage comprises a diverse array of accessoryminerals, notably including abundant sphene (titanite), which plays a vital role in bothrecording evolving conditions and driving trace element variation. Critical questions tobe addressed include: [1] What environmental factors control occurrence of keyaccessory minerals - especially sphene? [2] How does growth of accessories influencegeochemical signatures of magmas - and how can these signatures be used tocharacterize evolution of magmatic environments? [3] What are the conditions in giantchambers 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 alarge chamber? [6] Are chambers containing super-volumes of eruptible magmainherently unstable, or is triggering suppressed for unusual lengths of time to permitaccumulation of enormous quantities of magma? [7] How, and how efficiently, are largevolumes of melt-rich magma extracted from crystal-rich residue? [8] How and where arehighly-evolved, high-silica rhyolites generated? [9] What is the significance of similaritiesand differences between felsic intrusive and extrusive rocks? [10] Why are highlyevolved plutonic rocks less voluminous than volcanic equivalents? [11] Do gianteruptions have a different relation to their residual plutonic equivalents than'normal'-sized eruptions? Are their chambers far larger, or do they more efficientlyextract the eruptible material?This project will entail an integrated, multi-disciplinary approach involving PIs andcollaborators with diverse expertise and perspectives. The project will combineextensive field work, elemental and isotopic analyses of rock, glass, mineral, and meltinclusion samples, dating using several complementary geochronological methods,quantitative textural investigations, and experimental studies aimed at elucidating thestability and saturation behavior of sphene. We will employ, among other methods,NATIONAL SCIENCE FOUNDATIONProposal AbstractProposal:0911726 PI Name:Miller, CalvinPrinted from