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

“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；以及岩体和岩基的构造。我们提出了一个多方面的方法来研究600 km3桃泉凝灰岩（PST：中新世，亚利桑那州-加利福尼亚州-内华达州）的形成和喷发。广泛的流出层以及厚的破壁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），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：什么样的环境因素控制着关键辅助矿物的发生——尤其是榍石？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？在超级火山爆发之前，巨型洞穴的条件是什么？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长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质上是不稳定的，还是触发被抑制了异常长的时间以允许大量岩浆的积累？大量富含熔体的岩浆是如何从富含晶体的残留物中提取出来的？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”规模的火山喷发相比，巨型火山喷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年，定量纹理调查和旨在阐明斯芬的稳定性和饱和行为的实验研究。我们将采用，除其他方法外，国家科学基金会提案摘要提案：0911726 PI名称：Miller， calvin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