Dynamics of Large Silicic Magma Reservoirs: Combining Geochemical Data and Physical Models on Voluminous Ignimbrites From the San Juan Volcanic Field, Colorado

大型硅质岩浆储层的动力学：结合科罗拉多州圣胡安火山场大量熔凝结岩的地球化学数据和物理模型

• 批准号: 0809828
• 负责人: Olivier Bachmann
• 金额: $ 30.49万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0809828&HistoricalAwards=false
• 关键词: Dynamics; Large; Silicic; Magma; Reservoirs

Large volcanic eruptions are fascinating displays of our Earth's internal energy. They involve a series of complex processes from magma generation in the mantle and deep crust to the catastrophic outpourings of hot ash and gas on the surface of our planet. The processes by which silicic magma behave in shallow crustal reservoirs are critical to our understanding of volcanism and crustal construction. In that respect, large silicic ignimbrites (i.e., pyroclastic flow deposits) provide an exceptional record of how such magmas evolve in interaction with their environment. An ideal region in which to study large-volume silicic magmatism (especially from perspectives of crustal evolution and petrological processes occurring in large silicic magma reservoirs) is the San Juan volcanic field (Colorado, USA). Highly productive Tertiary magmatism (at least 17 large-volume ash-flow sheets erupted between ~29.5 to 26.9 Ma) through continental crust dominated by Precambrian lithologies allows a number of possible studies, some of which will be explored in this proposal.It is proposed to use large ignimbrite sheets from the San Juan volcanic field as natural laboratories for silicic magma evolution processes. The team will combine results from geochemical micro-analytical techniques (such as electron microprobe, LA-ICP-MS and microdrilling-TIMS analyses) in conjunction with numerical simulations of magma dynamics to better understand the mechanisms leading to compositional zoning in large ash-flow tuffs; the dynamics of crustal assimilation in upper crustal conditions; and examine all necessary conditions leading to eruption of large reservoirs. New analytical data in addition to published geochronological and geochemical data on San Juan magmas will be used to provide the ideal stepping stone for scrutinizing key rock units and merging physical and geochemical models of magmatic processes.

大型火山喷发是地球内部能量的迷人展示。它们涉及一系列复杂的过程，从地幔和地壳深处的岩浆生成到地球表面热火山灰和气体的灾难性喷发。硅质岩浆在浅层地壳储层中的活动过程对我们理解火山作用和地壳构造是至关重要的。在这方面，大型硅质火成岩（即火山碎屑流沉积）提供了这种岩浆如何与环境相互作用的特殊记录。美国科罗拉多州的圣胡安火山场是研究大体积硅质岩浆活动（特别是从地壳演化和大型硅质岩浆储层中的岩石学过程的角度）的理想区域。高产的第三纪岩浆活动（在~29.5 ~ 26.9 Ma之间爆发了至少17个大体积的火山灰流片）穿过以前寒武纪岩性为主的大陆地壳，这使得许多可能的研究成为可能，其中一些将在本提案中进行探讨。建议利用来自圣胡安火山场的大型褐煤片作为硅岩浆演化过程的天然实验室。该团队将结合地球化学微分析技术（如电子探针、LA-ICP-MS和微钻- tims分析）的结果，结合岩浆动力学的数值模拟，以更好地理解导致大型火山灰流凝灰岩成分分区的机制；上地壳条件下地壳同化动力学；并检查导致大型水库喷发的所有必要条件。新的分析数据，加上已公布的圣胡安岩浆的地质年代和地球化学数据，将为仔细检查关键岩石单元和合并岩浆过程的物理和地球化学模型提供理想的垫脚石。