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 - 对三个对比鲜明的火山口中的深成岩和火山岩进行地质年代学和地球化学研究智力价值。拟议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火山口岩浆作用的关键方面。在火山口岩浆作用期间，大量成分多样的岩浆被注入上地壳中。部分岩浆喷发，其余部分结晶形成岩体。我们目前对火山口岩浆过程的了解大部分来自对火山岩的详细研究。 同生深成岩还记录了有关火山口下岩浆过程的有用信息，例如现有岩浆房的更新和改造、岩脉和岩床的就位、与复活相关的上涌岩浆以及岩浆作用的衰弱阶段。这些过程都没有直接记录在火山记录中。通过建立与火山口相关的火山岩和深成岩的时间、化学和空间关系，可以开发更全面的火山口岩浆作用模型。该提案的目标包括调查岩浆分异的深度，探索岩浆侵位到上地壳的速率，确定未喷发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房的比例，确定分区和非分区火成岩套之间的差异，以及了解大体积硅质火山活动和深成作用之间的关系。三个中新生代火山口系统——新墨西哥州的Questa和Organ，以及科罗拉多州的Mt. Aetna，已被选来研究与火山口相关的岩浆作用。这些地点的格兰德河裂谷断层暴露了火山口内的火山岩和火山口下的侵入体。开发火山口岩浆作用模型的一个挑战是不同火山口系统之间的过程可能会有所不同。由于现场位置在破火山口岩浆作用的类型以及暴露的火山和深成岩的体积和深度方面有所不同，因此这些破火山口系统为了解相关的岩浆过程提供了必要的多样性。过去几年的实地工作已经为每个地点提供了全面的样本套件。 Ar-Ar 方法将用于确定火山活动和岩体就位和冷却历史的时间。激光烧蚀 ICP-MS U-Pb 测年将用作识别样品的勘察工具，随后将使用 CA-ID-TIMS 方法确定样品的高精度年龄。将使用离子探针 O 同位素分析来监测深成岩中喷发后的锆石改性。同期深成岩和火山岩的地球化学将用于确定分馏、部分熔融和同化在产生大量硅质熔体中的作用。更广泛的影响。了解与破火山口相关的岩浆作用对于评估火山危害至关重要。综合火山口岩浆模型也可用于勘探与火山相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（例如火凝岩、环脉）提供高精度的 UPb 和 Ar-Ar 年龄，因此拟议的研究将测试最近相互校准两个辐射系统的努力的准确性。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理工学院、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。 PI 将在研究生的帮助下继续与国家公园和州立公园互动，为社区提供教育体验。数据将提交至 NAVDAT 数据库，该数据库曾经并将继续广泛用于制定本提案的核心思想。

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.