Collaborative Research: Magnetotelluric and Seismic Investigations of Arc Melt Generation, Deliver and Storage Beneath Okmok Volcano

调查人员将在阿留申弧区的奥克莫克火山进行大地电磁(MT)调查，以确定火山下方的岩浆系统。将收集新的陆上被动地震和大地电磁数据以及海上大地电磁数据，以检验有关板条流体在弧形熔体生成、地壳内熔体迁移和活动火山口下的地壳岩浆管道和储存系统中所起作用的假设。该项目将支持一名女性早期职业调查员、几名研究生和本科生，为后者提供海上实践研究。本项目的数据计划纳入本科生的地球科学课程和演示文稿。第二部分阿留申火山弧是GeoPRISMS的主要调查地点，是被认为是研究弧岩浆作用的理想构造活动区。奥克莫克活火山位于阿留申弧中部，距离荷兰港仅100公里，这为陆上和近海两栖地球物理成像弧形S岩浆系统提供了有利条件。奥克莫克之所以被选中，也是因为它的已知火山活动、先前研究推断的地壳岩浆库的存在以及2008年喷发前缺乏预警所证明的火山灾害。它有2次火山口形成喷发(CFE)，是阿留申弧内和世界各地经历长时间喷发的火山的代表，其间穿插着更大的爆炸性CFE。该项目将测试流体在熔化地幔楔体中所起的作用，以及熔体如何通过地幔楔体的角落流动区域上升的假说。它还将测试关于上地幔和地壳内熔体迁移和储存的相互竞争的假设，以及这如何影响爆炸性CFE。该项目收集的数据将用于绘制弧内地震速度和电导率变化图，提供对温度、矿物学和流体含量的独特约束。这些约束将被用来研究地幔熔体的流动，它在地壳底部的可能储存，中上地壳部分熔体/岩浆体的分布，以及火山口下的上地壳的热和力学性质。将支助1名女性早期职业调查员和3名研究生(1名斯克里普斯；2名威斯康星大学麦迪逊分校)。七名本科生将得到支持(部分来自该项目的资金和Scripps NSF REU资助的SURF计划)，以参与陆上/离岸实地考察工作。该项目的数据将被纳入本科生的地球科学课程，并将在当地的K-12学校和几所阿拉斯加学校通过现场网络研讨会进行演讲。威斯康星大学麦迪逊分校将举办一期关于大地电磁测深方法的短期课程，并将为威斯康星大学地质博物馆的S活动地球展示项目制作一台电脑显示器。

Part 1The investigators will conduct a magnetotelluric (MT) survey at Okmok volcano in the Aleutian arc in order to characterize the magmatic system beneath the volcano. New onshore passive seismic and MT data and offshore MT data will be collected to test hypotheses regarding the role of slab fluids in arc melt generation, melt migration within the crust, and the crustal magmatic plumbing and storage system beneath an active caldera. The project will support a female early career investigator several graduate and undergraduate students providing the latter hands-on research at sea. Data from this project is planned to be incorporated into undergraduate Earth Sciences courses and presentations.Part 2The Aleutian volcanic arc is a GeoPRISMS primary investigation site that is tectonically active region considered to be ideal for studying arc magmatism. Okmok, an active volcano located in the central Aleutian arc, is only about 100 km from Dutch Harbor making it a logistically advantageous for an amphibious onshore and offshore geophysical imaging of the arc?s magmatic system. Okmok is also selected due to its known volcanic activity, the presence of a crustal magma reservoir, as inferred from previous studies, and the volcanic hazard it presents, as evidenced by the lack of warning prior to 2008 eruption. It has hosted 2 caldera-forming eruptions (CFE) and is representative of volcanoes both within the Aleutian arc and worldwide that experience long periods of effusive eruptions punctuated by much larger explosive CFE. The project will test hypotheses on the role fluids play in melting the mantle wedge and how melts ascend through the corner flow regime of the mantle wedge. It will also test competing hypotheses about melt migration and storage within the upper mantle and crust and how this impacts explosive CFE. Data collected by this project will be used to map seismic velocity and electrical conductivity variations within the arc, providing unique constraints on temperature, mineralogy and fluid content. These constraints will be used to study the mantle melt flux, its possible storage at the base of the crust, the distribution of partial melt/magma bodies in the mid-upper crust, and the thermal and mechanical properties of the upper crust beneath the caldera.Broader Impacts: The proposed work would help improve our understanding of magma storage and transport and its implications on volcanic hazards at Okmok volcano. A female early career investigator and three graduate students (1 Scripps; 2 UW-Madison) would be supported. Seven undergraduate students would be supported (partially through funds from this project and via Scripps NSF REU supported SURF program) to participate in onshore/offshore fieldwork. Data from this project will be incorporated into undergraduate Earth Sciences courses and presentations will be given at local K-12 schools and via live webinars to a few Alaskan schools. A short course on MT methods will be given at UW-Madison and a computer display for this project will be created for the UW Geology Museum?s Active Earth display.