EAR-PF: Resolving the tempo of edifice development and rhyolite formation in a large-caldera system, Atitlan, Guatemala

石楠S坎宁安博士已被授予美国国家科学基金会地球科学博士后奖学金，在威斯康星州-麦迪逊大学开展研究和教育计划。调查的目的是详细说明危地马拉Atitlán Caldera火山口建筑物发展的短期和长期趋势。将在实地活动期间收集代表大规模火山喷发、相关火山渣层和火山锥生长阶段的选定火山灰和熔岩，以进行地球化学分析。主要和微量元素数据将被整合到岩石学模型中，以确定大型硅质岩浆体的发育情况，以及它们是否与浅层改性过程（例如分离结晶、岩浆混合或同化）相关。将测量同位素数据（87 Sr/86 Sr和143 Nd/144 Nd）以支持岩石学模型，因为这些同位素比值与源成分不同。为了确定喷发年龄，将对不同喷发单元的斑晶进行40 Ar/39 Ar同位素分析。将测量火山灰中的230 Th/238 U不平衡，以确定大型岩浆体是否从同质源（例如由几个岩浆体合并形成的深地壳热区或地壳同化产物）迅速分化。通过解析导致大破火山口喷发的时间尺度和过程以及相关的火山锥形成阶段，可以推断潜在的火山风险。然而，我们对导致大型火山口形成喷发的过程的理解受到缺乏最近暴露的沉积物的限制。因此，阿蒂特兰火山复合体非常适合于测试产生大体积火山喷发的相互冲突的模型，更重要的是，破火山口系统发展的时间尺度。除了开发地球化学模型外，还将开展教育活动。将向教育工作者提供阿蒂特兰火山口动态数字地图，使学生能够亲自接触真实的世界数据。

Dr. Heather S Cunningham has been granted the NSF Earth Sciences Postdoctoral Fellowship to carry out a research and education plan at the University of Wisconsin - Madison. The investigation aims to detail the short- and long-term trends in caldera edifice development at Atitlán Caldera, Guatemala. Selected volcanic ash and lavas representing the large silicic eruptions, associated scoria layers and cone-growth phases will be collected during a field campaign for geochemical analysis. Major and trace element data will be integrated into petrologic models to determine how large silicic magma bodies develop and if they are related by shallow-level modification processes such as fractional crystallization, magma mixing or assimilation. Isotopic data (87Sr/86Sr and 143Nd/144Nd) will be measured to support petrologic models since these isotopic ratios are distinctive to source composition. To constrain eruptive age, 40Ar/39Ar isotopes will be analyzed on phenocrysts in distinctive eruptive units. 230Th/238U disequilibrium will be measured on volcanic ash to resolve whether large silicic bodies are rapidly differentiated from a homogeneous source, such as a deep crustal hot zone, formed by the coalescence of several magma bodies or the product of crustal assimilation. By resolving the time scales and processes that lead to large-caldera eruptions and associated cone-building phases potential volcanic risk can be inferred. However, our understanding of the processes that lead to large caldera-forming eruptions is limited by the lack of recent, well-exposed deposits. Thus, the Atitlán volcanic complex is ideally suited to test conflicting models for the generation of large-volume silicic eruptions and more importantly time scales over which caldera-systems develop. In addition to the development of geochemical models, an educational exercise will be created. A Dynamic Digital Map of Atitlán Caldera will be made available to educators that will allow students hands-on access to real world data.