Collaborative Research: Structure, Conditions and Magmatic Processes Within an Active Volcano: Analysis of Samples from Boreholes Drilled into the Conduit of Unzen Volcano, Interna

该项目将允许pi参与目前由日本Unzen科学钻探项目（USDP）钻探的钻孔和样品的国际合作调查。USDP是国际大陆钻探计划（ICDP）的一部分，该计划旨在利用钻探作为一种工具来促进对地壳基本过程的理解。USDP的目标是了解云仙火山的喷发行为，作为安山岩弧火山的重要代表。在现已完成的第一期钻井工程中，为了获得火山活动的完整物理和化学记录，在火山大厦的底部钻了750米和1500米的侧孔。这项提议的目的是继续一个为期一年的试点项目，该项目表明，目前的Unzen岩浆系统已经持续了50万年，其特征是频繁地将分块基性岩浆注入到组成非常恒定的地壳泥浆中。钻探项目下一阶段的智力目标将是：1)了解粘性岩浆在接近地球时的机械、化学和热行为。年代表面;2.)确定为什么云仙火山是最初湿岩浆非爆炸性喷发的典型案例，3.)通过提供直接的地下观测来改进预测喷发的技术，这些观测可以解释地震活动、变形和脱气的前兆。研究人员建议使用光学、扫描电镜、电子探针、XRF和LA-ICPMS技术来检查样品。特别是，将近端单元与侧钻中遇到的单元进行对比，绘制热液蚀变带，识别侵入特征。最重要的是，1991-1994年爆发的管道将被划定。为了约束脱气行为，将特别注意导管边缘的侵入玻璃和中心部分残余熔体的出现。将玻璃状穹窿熔岩与部分结晶管状物质（如果残余熔体残留）和结晶管状物质进行比较，将有助于确定云仙岩浆的完整结晶路径。将确定管道宽度、管道内与脱气和冷却有关的结构变化、岩浆和围岩的似是而非的流变学以及管道流动和脱气对围岩的影响。就更广泛的影响而言，这项工作应该提高对这种危险的火山活动的理解和可预测性，这种火山活动不仅影响了日本的岛原，而且近年来还影响了菲律宾皮纳图博火山附近的城镇和蒙特塞拉特岛的苏弗里埃尔山火山。该项目在日本引起了公众的极大兴趣，一旦管道的钻探开始，可能会引起全世界的兴趣。因此，USDP团队计划在万维网上以近乎实时的英语、日语和德语向公众提供结果。作为团队中美国科学界的代表，研究人员将适当利用这一机会，使他们的美国同事了解出现的研究机会。这将有助于增加从事云禅宗事业的专业知识的广度，同时使美国人了解日本火山学界非常丰富的资源、经验和思想。

This project will allow the PIs to participate in internationally collaborative investigations of boreholes and samples now being drilled by the Unzen Scientific Drilling Project (USDP), Japan. The USDP is part of the International Continental Drilling Program (ICDP), which seeks to use drilling as a tool to advance understanding of fundamental processes of Earth's crust. The goal of the USDP is to understand the eruptive behavior of Unzen as representative of an important class of andesitic arc volcanoes. In the now-completed first phase of the drilling project, flank holes of 750 m and 1500 m were drilled to the base of the volcanic edifice in order to obtain a complete physical and chemical record of the volcano's activity. This proposal aims to continue a one-year pilot project that has shown that the present Unzen magma system, which is characterized by frequent injection of fractionated mafic magma into a crust-resident slush of remarkably constant composition, has persisted for 500,000 years. The intellectual targets for the next phase of the drilling project will be: 1.) to understand how viscous magma behaves mechanically, chemically, and thermally as it approaches Earth.s surface; 2.) to determine why Unzen is such an exemplary case of non-explosive eruption of initially wet magma, and 3.) to improve techniques to forecast eruptions by providing direct subsurface observations that inform interpretation of precursory seismicity, deformation, and degassing. The investigators propose to use optical, SEM, electron microprobe, XRF, and LA-ICPMS techniques to examine the samples. In particular, proximal units will be correlated to units encountered in flank drilling, zones of hydrothermal alteration will be mapped, and intrusive features identified. Most importantly, the conduit that fed the 1991-1994 eruption will be delineated. In order to constrain degassing behavior, special attention will be paid to occurrence of intrusive glass on the margin of the conduit and residual melt in the central portion. Comparison of glassy dome lava with partially crystalline conduit material (if residual melt remains) and with crystalline conduit material will serve to define the complete crystallization path of Unzen magma. Conduit width, textural variations within the conduit related to degassing and cooling, plausible rheologies of the magma and wallrock, and effects of conduit flow and degassing on the wallrock will be determined. In terms of broader impacts, the work should improve the understanding and predictability of this dangerous type of volcanic activity, which has afflicted not only Shimabara, Japan but also towns near Pinatubo Volcano in the Philippines and Soufriere Hills Volcano in Montserrat in recent years. The project has attracted much public interest in Japan, and will likely do so worldwide once drilling to the conduit has begun. Accordingly, the USDP team plans to make results available to the public in near-real time in English, Japanese, and German over the Worldwide Web. As representatives of the US scientific community on the team, the investigators will make appropriate use of this opportunity to acquaint their American colleagues with research opportunities as they arise. This will serve to increase the breadth of expertise engaged in the Unzen enterprise, while at the same time acquainting Americans with the very substantial resources, experience, and ideas of the volcanological community of Japan.