Collaborative Research: Caldera Magmatism from the Inside Out: A geochronologic and Geochemical Investigation of Plutonic and Volcanic Rocks in Three Contrasting Calderas

合作研究：由内而外的火山口岩浆作用：三个对比火山口中的深成岩和火山岩的年代学和地球化学研究

• 批准号: 1050215
• 负责人: Drew Coleman
• 金额: $ 23.61万
• 依托单位: University of North Carolina at Chapel Hill
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-15 至 2014-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1050215&HistoricalAwards=false
• 关键词: Collaborative; Research; Caldera; Magmatism; Inside

Collaborative research: Caldera magmatism from the inside out - A geochronologic and geochemical investigation of plutonic and volcanic rocks in three contrasting calderasIntellectual Merit. The proposed research will use geochronology and geochemistry of cogenetic volcanic and plutonic rocks to understand critical aspects of caldera magmatism. During caldera magmatism, large volumes of compositionally diverse magmas are emplaced into the upper crust. Some fraction of this magma erupts and the remainder crystallizes to form a pluton. Much of our current understanding of caldera magmatic processes is from detailed studies of the vocanic rocks. Cogenetic plutonic rocks also record useful information about sub-caldera magmatic processes such as rejuvenation and modification of existing magma chambers, dike and sill emplacement, upwelling magma related to resurgence, and the waning stages of magmatism. None of these processes are directly recorded in the volcanic record. By establishing the temporal, chemical, and spatial relationship of both caldera-related volcanic and plutonic rocks, a more comprehensive model of caldera magmatism can be developed. Objectives of this proposal include investigating the depth of magma differentiation, exploring rates of magma emplacement into the upper crust, establishing the role of nonerupted magma in postcaldera magmatism, estimating the fraction of a caldera magma chambers that erupt, determining differences between zoned and nonzoned igneous suites, and understanding the relationship between large-volume silicic volcanism and plutonism. Three mid-Cenozoic caldera systems - Questa and Organ in New Mexico, and Mt. Aetna in Colorado, have been selected for investigating caldera related magmatism. Rio Grande-rift-faulting at these locations has exposed both intracaldera volcanic rocks and subcaldera intrusions. A challenge in developing caldera magmatism models is the likelihood that processes vary between different caldera systems. Because the field locations differ with respect to style of caldera magmatism and volume and depth of exposed volcanic and plutonic rocks, these caldera systems provide the necessary diversity to understand the associated magmatic processes. Fieldwork during the past several years has already yielded a comprehensive sample suite for each location. The Ar-Ar method will be used to establish the timing of volcanism and pluton emplacement and cooling histories. Laser ablation ICP-MS U-Pb dating will be used as a reconnaissance tool to identify samples for which high-precision ages will subsequently be determined using the CA-ID-TIMS method. Post-eruptive zircon modification in the plutonic rocks will be monitored using ion-probe O-isotope analysis. Geochemistry of coeval plutonic and volcanic rocks will be used to determine the roles of fractionation, partial melting, and assimilation in generating large volumes of silicic melt.Broader Impacts. Understanding the magmatism associated with calderas is essential to assessing volcanic hazards. Comprehensive caldera magmatic models may also be used to explore for volcanorelated geothermal activity and economic ore deposits. Because this study will produce high-precision UPb and Ar-Ar ages for rapidly cooled rocks (e.g. ignimbrites, ring dikes), the proposed research will test the accuracy of recent efforts to intercalibrate the two radiometric systems. The project will provide the PIs, two doctoral students, two masters students, and at least three undergraduate students a collaborative research experience between New Mexico Tech, the University of North Carolina, the USGS and UCLA. Research will provide graduate students with useful laboratory training to develop skills necessary for professional careers. The PIs, along with help from the graduate students, will continue interacting with national and state parks to provide an education experience for the community. Data will be submitted to the NAVDAT database, which was, and will continue to be, used extensively in developing the ideas central to this proposal.

合作研究：从内到外的火山口岩浆作用--对三个不同火山口的深成岩和火山岩进行地质年代学和地球化学调查，具有智力上的价值。拟议的研究将利用同源火山岩和深成岩的地质年代学和地球化学来了解火山口岩浆活动的关键方面。在火山口岩浆作用期间，大量成分各异的岩浆侵位到上地壳。岩浆中的一部分喷发，其余部分结晶形成深成岩浆。我们目前对火山口岩浆作用的大部分了解都来自于对火山岩的详细研究。同生深成岩还记录了有关破火山口下岩浆作用的有用信息，如现有岩浆室的恢复和改造、岩脉和岩床侵位、与回升有关的上涌岩浆以及岩浆作用的减弱阶段。这些过程都没有直接记录在火山记录中。通过建立与火山口有关的火山岩和深成岩的时间、化学和空间关系，可以开发出更全面的火山口岩浆活动模式。这一建议的目标包括调查岩浆分异的深度，探索岩浆侵入上地壳的速度，确定未喷发的岩浆在火山口后岩浆作用中的作用，估计喷发的火山口岩浆室的比例，确定带状和非带状火成岩之间的差异，以及了解大体积硅质火山作用和深成岩作用之间的关系。三个中新生代火山口系统--新墨西哥州的Questa和Organ，以及Mt.科罗拉多州的Aetna被选为研究与火山口有关的岩浆活动的地点。里奥格兰德--这些地方的断裂暴露了火山口内的火山岩和火山口下的侵入。开发破火山口岩浆作用模型的一个挑战是，不同的破火山口系统之间可能存在不同的过程。由于火山口岩浆活动的类型以及暴露的火山和深成岩的体积和深度不同，这些火山口系统为理解相关的岩浆过程提供了必要的多样性。在过去的几年里，实地考察已经为每个地点产生了一套全面的样本。Ar-Ar方法将被用来确定火山活动的时间、岩体侵位和冷却历史。激光烧蚀电感耦合等离子体质谱U-Pb测年将被用作一种侦察工具，以确定随后将使用CA-ID-TIMS方法确定其高精度年龄的样品。将使用离子探针氧同位素分析来监测深成岩中喷发后的锆石变质作用。同时代的深成岩和火山岩的地球化学将被用来确定分馏、部分熔融和同化作用在产生大量硅质熔体中的作用。了解与火山口有关的岩浆活动对于评估火山灾害至关重要。综合的火山口岩浆模型也可用于勘探与火山有关的地热活动和经济矿床。由于这项研究将为快速冷却的岩石(如原火岩、环形岩脉)提供高精度的UPB和Ar-Ar年龄，拟议的研究将测试最近对两个辐射测量系统进行相互校准的努力的准确性。该项目将为PI、两名博士生、两名硕士学生和至少三名本科生提供新墨西哥理工大学、北卡罗来纳大学、美国地质调查局和加州大学洛杉矶分校之间的合作研究体验。研究将为研究生提供有用的实验室培训，以发展专业生涯所需的技能。在研究生的帮助下，PI将继续与国家和州立公园互动，为社区提供教育体验。数据将提交给NAVDAT数据库，该数据库过去在制定本提案的核心思想时曾被广泛使用，现在仍将广泛使用。