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：从内到外的破火山口岩浆作用--三个对比破火山口中深成岩和火山岩的地质年代学和地球化学研究。拟议中的研究将利用同生火山岩和深成岩的地质年代学和地球化学来了解破火山口岩浆活动的关键方面。在破火山口岩浆活动期间，大量成分多样的岩浆侵位到上地壳。部分岩浆喷发，其余部分结晶形成深圳湾。我们目前对火山口岩浆过程的了解大多来自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过程的有用信息，如现有岩浆房的再生和修改、岩墙和岩床就位、与复活有关的上涌岩浆以及岩浆活动的衰退阶段。这些过程都没有直接记录在火山记录中。通过建立与破火山口有关的火山岩和深成岩的时间、化学和空间关系，可以建立一个更全面的破火山口岩浆活动模型。本提案的目标包括调查岩浆分异的深度，探索岩浆侵位到地壳上部的速率，建立未喷发的岩浆在破火山口后岩浆活动中的作用，估计破火山口岩浆房喷发的比例，确定分区和非分区火成岩套房之间的差异，并了解大体积火山岩和深成岩之间的关系。三个中新生代破火山口系统-新墨西哥州的奎斯塔和奥根，和Mt. Aetna在科罗拉多，已被选为调查火山口有关的岩浆活动。这些地点的Rio Grande裂谷断裂暴露了火山口内的火山岩和火山口下的侵入体。开发破火山岩浆活动模型的一个挑战是，不同的破火山系统之间的过程可能有所不同。由于现场位置不同的风格火山岩浆和体积和深度暴露的火山岩和深成岩，这些火山口系统提供了必要的多样性，以了解相关的岩浆过程。过去几年的实地工作已经为每个地点产生了一套全面的样本。Ar-Ar方法将用于确定火山作用和深成岩侵位和冷却历史的时间。激光烧蚀ICP-MS U-Pb测年将被用作一种侦察工具，以确定样品，随后将使用CA-ID-TIMS方法确定其高精度年龄。火山喷发后的锆石修改的深成岩将监测使用离子探针O-同位素分析。将利用同时代的深成岩和火山岩的地球化学来确定分馏、部分熔融和同化作用在产生大量的岩浆熔体中的作用。了解与破火山口有关的岩浆活动对评估火山灾害至关重要。综合破火山口岩浆模型也可用于探索与火山有关的地热活动和经济矿床。由于这项研究将产生高精度的UPb和Ar-Ar年龄的快速冷却的岩石（如熔结凝灰岩，环形岩脉），拟议的研究将测试最近的努力，以相互校准的两个辐射系统的准确性。该项目将为PI，两名博士生，两名硕士生和至少三名本科生提供新墨西哥州理工学院，北卡罗来纳州大学，USGS和UCLA之间的合作研究经验。研究将为研究生提供有用的实验室培训，以培养职业生涯所需的技能。在研究生的帮助下，PI沿着将继续与国家公园和州立公园互动，为社区提供教育体验。数据将提交给NAVDAT数据库，该数据库过去和将来都将被广泛用于发展本提案的核心思想。

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.