Circulation of Magma in Volcanic Conduits as a Degassing Mechanism at Active Volcanoes: A Geochemical and Fluid-Dynamic Approach

Kress9980566该项目的目标是更好地了解火山气体来源和高气体通量火山的非爆炸性被动脱气机制。 我们推测，“过量”的气体排放在被动脱气火山可能是由岩浆在火山管道在镁铁质和俯冲带火山的循环。两个对比鲜明的火山，波波卡特佩特（墨西哥）和比利亚里卡（智利），是拟议研究的重点。尽管岩浆产量非常有限，但在过去的5年里，波波卡特佩特一直在被动地排出大量的二氧化硫蒸气。 在过去的15年里，比利亚里卡的山顶火山口一直有一个活跃的熔岩湖。与管道循环相关的高热量和气体传递率可能能够解释在Popocatepetl和比利亚里卡观察到的现象。 我们将采取两步调查程序进行这项研究。首先，对波波卡特佩特和比利亚里卡岩石样本的地球化学分析将使我们能够确定岩浆房中喷发前的条件（例如，温度和压力），并量化火山气体源的成分和大小。其次，使用多相，流体动力学模型的岩浆循环的管道，我们将量化的被动脱气率在两个火山的审查。除了上述实验室和模拟研究外，在比利亚里卡的一次实地活动将对COSPEC的二氧化硫通量进行测量，直接从山顶火山口采集气体样本，并从代表性的爆炸和喷发中收集岩石样本。 这项研究的结果将揭示爆炸性和非爆炸性火山活动的动力学之间的差异，以及帮助量化被动火山脱气的火山气体对大气的贡献。

Kress9980566The goal of this project is to better understand the volcanic gas source and the mechanism for non-explosive, passive degassing at high-gas-flux volcanoes. We hypothesize that "excess" gas emission at passively degassing volcanoes may be explained by circulation of magma in the volcanic conduit at both mafic and silicic subduction zone volcanoes. Two contrasting volcanoes, Popocatepetl (Mexico) and Villarrica (Chile), are the focus of the proposed research. Popocatepetl has been passively degassing enormous quantities of SO2 vapor for the last 5 years despite very limited magma production. Villarrica has had an actively degassing lava lake perched in its summit crater for the last 15 years. High rates of heat and gas transfer associated with conduit circulation may be able to explain the observed phenomena at Popocatepetl and Villarrica. We will adopt a two-step investigative process for this study. First, geochemical analysis of rock samples from Popocatepetl and Villarrica will enable us to define pre-eruptive conditions in the magma chamber (e.g., temperature and pressure) and quantify the composition and size of the volcanic gas source. Second, using multiphase, fluid dynamic modeling of magma circulation in the conduit, we will quantify the rates of passive degassing at the two volcanoes under scrutiny. In addition to the laboratory and modeling studies described above, a field campaign at Villarrica will make COSPEC measurements of SO2 flux, directly sample gas from summit fumaroles, and collect rock samples from representative explosive and effusive eruptions. Results of this study will shed light on the differences between the dynamics of explosive and non-explosive volcanic activity as well as help quantify the contribution of volcanic gases to the atmosphere from passive volcanic degassing.