Collaborative Research: RUI: Probing Caldera-Forming Magmatism: Crystal Accumulation in Large, Upper Crustal Silicic Magma Chambers

合作研究：RUI：探测火山口形成的岩浆作用：大型上地壳硅质岩浆室中的晶体积累

• 批准号: 1250259
• 负责人: Rachel Beane
• 金额: $ 4.67万
• 依托单位: Bowdoin College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1250259&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Probing; Caldera

The next volcanic super-eruption will have global consequences for humanity. During one of these large eruptions, the explosive potential and the amount of lava and ash erupted are largely controlled by what happens in shallow magma reservoirs in Earth's crust. This project combines the study of frozen magma reservoirs trapped below-ground - plutons - with their associated above-ground volcanic rocks for two ancient super-volcanoes: the Lake City Caldera, Southern Rocky Mountain Volcanic Field in Colorado and the Turkey Creek Caldera in Arizona. The results of this study will provide unprecedented insight into processes occurring within shallow magma reservoirs that lead to super-eruptions, and ultimately will be applied to predict the behavior of potentially extremely hazardous active volcanic regions such as the Taupo Volcanic Zone, the Bay of Naples, and the Aegean Arc. The hypothesis being tested is that the plutonic porphyries in both the Lake City Caldera and the Turkey Creek Caldera are the quenched magma reservoirs remaining in the crust following caldera collapse. If this hypothesis is confirmed, these porphyries provide a unique snapshot of the evolution and post-eruptive conditions of the mushy rootzone associated with a super-eruption. The methods that will be applied to the volcanic and plutonic lithologies are: (1) detailed field mapping of the plutonic porphyries and field sampling of the volcanic units, (2) geochemical characterization of all units, (3) quantitative investigation of primary and accessory crystals in all units using electron microprobe analysis (EPMA), laser ablation inductively coupled mass spectrometry (LA-ICP-MS), and electron backscattered diffraction (EBSD), and (4) high resolution U-Pb dating and trace element analysis of zircons (CA-TIMS-TEA) in selected lithologies. This multi-analytical approach to the sub-volcanic intrusions and overlying silicic volcanic units is applied to establish the genetic relationship between the large, zoned ignimbrites and their plutonic roots, and to unravel the processes involved in chemical differentiation of large silicic magma chambers.

下一次超级火山喷发将对人类产生全球性的影响。在一次大型喷发中，爆发的潜力以及喷发出的熔岩和火山灰的数量在很大程度上取决于地壳中浅层岩浆库中发生的情况。这个项目结合了对两个古老超级火山的地下冻结岩浆储层的研究——地下岩浆——以及与之相关的地上火山岩：科罗拉多州的湖城火山口、南落基山火山场和亚利桑那州的土耳其溪火山口。这项研究的结果将为浅层岩浆储层中发生的导致超级火山爆发的过程提供前所未有的见解，并最终将应用于预测潜在极端危险的活火山区域的行为，如陶波火山带、那不勒斯湾和爱琴海弧。正在验证的假设是，湖城火山口和土耳其溪火山口的深成斑岩是火山口崩塌后留在地壳中的淬灭岩浆储层。如果这一假设得到证实，这些斑岩提供了与超级喷发相关的糊状根区的演化和喷发后条件的独特快照。将应用于火山和深部岩石学的方法有：(1)详细的深部斑岩野外填图和火山单元野外采样；(2)所有单元的地球化学表征；(3)利用电子探针分析（EPMA）、激光烧蚀电感耦合质谱（LA-ICP-MS）和电子背散射衍射（EBSD）对所有单元的主晶和副晶进行定量研究；(4)选定岩性的锆石高分辨率U-Pb定年和微量元素分析（CA-TIMS-TEA）。通过对次火山侵入岩及其上覆硅质火山单元的综合分析，建立了大型分带状火成岩及其深成根的成因关系，揭示了大型硅质岩浆房的化学分异过程。