Collaborative Research: The History of Degassing and Differentiation of the Bishop Tuff Rhyolitic Magma

9714187克里斯滕森这项研究旨在记录大约76万年前在加利福尼亚州中东部喷发的大量富含硅质的岩浆(凝灰岩主教)的物理和化学演化。新的野外工作提供了一个地层框架，可以评估岩浆的分化、上升、结晶和喷发之间的时空关系。合作者们将分析火山斑晶中亚毫米大小的玻璃和沙漏包裹体(喷发熄灭的熔体)中的主要、次要和微量元素，以及挥发性物质H2O和CO2以及Ar、锶和Nd的同位素。他们还将分析长石晶体，特别注意微量元素和同位素分带，以便将结晶年龄与结晶压力、熔体和岩浆成分以及喷发的时间和序列联系起来。一个主要的目标是测试由于脱气而产生的Ar和CO2相互作用的观点，并揭示岩浆与含有溶解空气的大气水之间的相互作用。本科生和青年科学家将参与该项目，并在研究和合作方面获得经验。这一结果将限制有关如此庞大的硅质岩浆如何形成、形成密度和成分梯度以及喷发的概念。这一结果将对硅质岩浆作用在陆壳脱气和演化中的作用具有重要意义。

9714187 Christensen This study aims to document the physical and chemical evolution of a large body of silica-rich magma (Bishop Tuff) that erupted about 0.76 million years ago in east-central California. New field work provides a stratigraphical framework that permits evaluation of space-time relations between differentiation, ascent, crystallization and eruption of the magma. The collaborators will analyze submillimeter-sized glass and hourglass inclusions (eruptively quenched melt) in volcanic phenocrysts for major, minor, and trace elements in addition to volatile species H2O and CO2 and isotopes of argon, strontium and neodymium. They will also analyze feldspar crystals paying particular attention to trace element and isotopic zonations so as to associate age of crystallization with pressure of crystallization, melt and magma composition as well as time and sequence of eruption. A main goal is to test the idea that argon and CO2 correlate as a result of degassing and reveal interaction of magma with meteoric water that contained dissolved air. Undergraduate students and young scientists will participate in the project and gain experience in research and collaboration. The results will constrain concepts regarding how such large bodies of silicic magma form, develop density and composition gradients, and erupt. The results will have significant implications for the role of silicic magmatism in the degassing and evolution of continental crust.