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Collaborative research: Andean Plutonic Perspectives on Generation, Storage, and Eruption of Rhyolite

合作研究：安第斯深成流纹岩生成、储存和喷发的观点

基本信息

批准号：
1650232
负责人：
Bradley Singer
金额：
$ 25.4万
依托单位：
University of Wisconsin-Madison
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-01-15 至 2019-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1650232&HistoricalAwards=false
关键词：
Collaborative research Andean Plutonic Perspectives

项目摘要

Large-scale, caldera-forming volcanic eruptions, for example those characteristic of Yellowstone National Park, owe their explosivity and widespread impact to the composition of molten rock called magma that fuels their plumbing systems. Yet, the generation of such magma plumbing systems, and how the erupted volcanic rock rhyolite is related to the unerupted magma that crystallizes at depth to form plutons of rock called granite that makes up the continental crust which we live on, remains unknown and highly controversial among earth scientists. Our study focuses on the formation of a plutonic body of granite in the southern Andes in Chile that preserves a record of processes required to generate large quantities of potentially explosive volcanic rhyolite. We will map spatially distinct rock types, measure their compositions, and determine the compositions of the constituent minerals that comprise this very young, and exceptionally well-exposed pluton. A multidisciplinary approach using modern geochemical methods, geochronology, and numerical modeling will then be used to interpret the processes, timescales, and thermal history of magma that are preserved in this pluton. We aim to bring the discipline of igneous petrology one step closer to a universal model of magma dynamics that incorporates both the plutonic and volcanic realms.High silica granites are hypothesized to form via crystal-melt fractionation in the shallow crust yet, the resulting crystal residues are rarely identified and can be difficult to distinguish from plutons whose compositions plot along liquid lines of descent. Bulk rock compositional mass balance in the late Miocene Risco Bayo-Huemul plutonic complex in the Southern Andes of Chile suggests that lithological differences reflect crystal concentration in response to melt extraction. We aim to combine field observations with U-Pb petrochronology of zircon and titanite, 40Ar/39Ar thermochronology, compositional and isotopic measurements of whole rocks and minerals within the plutonic complex, and thermal modeling to: (1) establish the rates and mechanisms of emplacement, (2) identify individual magma batches and assess any interaction between them, (3) determine the timescales of crystallization and cooling of individual magma batches and system-wide, (4) establish petrogenetic relationships between the Risco Bayo and Huemul plutons including subdomains within each, and (5) evaluate whether eruptible rhyolitic melt may have formed within this system. This young plutonic complex preserves a detailed record of a process commonly associated with the formation of rhyolite that has propelled large silicic eruptions during the past million years within the adjacent Andean subduction zone.

大规模的火山爆发，例如黄石国家公园的火山爆发，其爆炸性和广泛的影响归功于称为岩浆的熔融岩石的成分，这些岩浆为其管道系统提供燃料。然而，这种岩浆管道系统的产生，以及喷发的火山岩流纹岩如何与未喷发的岩浆有关，未喷发的岩浆在深处结晶形成称为花岗岩的岩石，构成我们生活的大陆地壳，仍然是未知的，在地球科学家中极具争议。我们的研究重点是在智利南部的安第斯山脉的花岗岩深成体的形成，保存了产生大量潜在的爆炸性火山流纹岩所需的过程的记录。我们将绘制空间上不同的岩石类型，测量它们的成分，并确定构成这个非常年轻，异常暴露的岩体的组成矿物的成分。一个多学科的方法，使用现代地球化学方法，地质年代学和数值模拟，然后将被用来解释的过程，时间尺度和热历史的岩浆保存在这个岩体。我们的目标是使火成岩石学的学科更接近一个普遍的岩浆动力学模型，包括深成和火山领域。高硅花岗岩被假设为形成通过晶体熔体分馏在地壳浅，但由此产生的晶体残留物很少被确定，并可能难以区分的组成图沿着液体下降线的岩体。大块岩石组成的质量平衡在晚中新世里斯科Bayo-Huemul深成杂岩在智利南部安第斯山脉表明，岩性差异反映晶体浓度熔体提取。我们的目标是将联合收割机野外观测与锆石和钛铁矿的U-Pb岩石年代学、40 Ar/39 Ar热年代学、深圳湾杂岩内整个岩石和矿物的成分和同位素测量以及热模拟相结合，以便：（1）确定侵位的速率和机制，（2）识别单个岩浆批次并评估它们之间的任何相互作用，（3）确定单个岩浆批次和整个系统的结晶和冷却时间尺度，（4）建立Risco Bayo和Huemul岩体之间的岩石成因关系，包括每个岩体内的子域，（5）评估该系统内是否可能形成可喷发的流纹岩熔体。这个年轻的深成杂岩保存了通常与流纹岩形成相关的过程的详细记录，该过程在过去一百万年里推动了邻近安第斯俯冲带内的大型硅质喷发。