The Mantle Melt Column and Melt Migration Revealed by Deglaciation Melting Beneath Iceland's Western Rift Zone

该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)提供资金的。为大洋岛屿和大部分深海的火山喷发提供燃料的岩浆是由下伏地幔熔融产生的。目前有关岩浆成因和运移细节的知识来源于对喷发速度和玄武岩化学的观察，并辅之以数值模拟。然而，由于火山活动的产物通常只提供熔体迁移过程的时间综合视图，因此通常很难限制熔体迁移的重要速率和时间尺度。该项目将利用冰岛冰川卸荷引起的随时间变化的融化扰动的独特情况，对地幔融化的各个方面提供前所未有的限制，这将适用于在广泛的地质环境中进行的地幔融化研究。该项目有一个重要的国际组成部分，涉及与冰岛大学的合作。该项目还为一位最近在夏威夷大学获得博士学位的年轻科学家提供了一个重要的教育和培训部分。通过这个项目，她将获得野外测绘、冰岛地质学和火山学方面的经验，并学习一系列地球化学分析和复杂地球动力学建模方面的新技术。该项目旨在让夏威夷大学的本科生参与实地工作和后续研究。这项拟议的研究将丰富夏威夷大学的教学和研究项目，该大学位于一个种族多元化的社区，其中包括来自一系列亚洲和太平洋岛国的人。因此，它将为具有不同文化背景的理科学生提供先进的技术培训和指导。理论和初步观察表明，上一次冰期末期冰的清除对冰岛的火山生产和岩浆化学产生了深远的影响。项目调查人员将使用冰芯数据和地质重建来限制冰川消退的时间，时间从现在的1.5万年到1.1万年之间。他们将使用新的地质制图和样品收集、地球化学分析和跨越晚冰川台面山脉的空中熔岩的3He暴露年龄测定，将喷发速度和熔岩成分的记录延长到15ka。数值模型将模拟更新的冰川卸载历史，以及由此产生的地幔融化、熔体迁移和化学运输的扰动。通过模拟观测到的喷发速度、微量元素和同位素组成的时间变化，它们将限制熔体的运移速度，确定地幔熔体柱的基本性质，并测试是否存在小规模地幔不均匀。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Magma that feeds volcanic eruptions on oceanic islands and most of the deep ocean is produced by melting of the underlying mantle. Current knowledge of the details of magma genesis and transport are derived from observations of eruption rates and basalt chemistry coupled to numerical modeling. However, because the products of volcanic activity usually provide only a time-integrated view of the melt migration process, it is normally very difficult to constrain the important rates and time scales of melt transport. This project will exploit the unique situation of time-varying melting perturbations due to glacial unloading in Iceland to provide unprecedented constraints on aspects of mantle melting that will be applicable to mantle melting studies in a wide range of geological settings. The project has a significant international component involving collaboration with the University of Iceland. It also has a major educational and training component for a young scientist who will have recently obtained her PhD at the University of Hawai'i. With this project she will gain experience in field mapping and Icelandic geology and volcanology as well as learn new techniques in a range of geochemical analyses and in sophisticated geodynamic modeling. The project is intended to involve undergraduate students from the University of Hawaii in the field work and follow-on research. The proposed research will enrich teaching and research programs at the University of Hawaii, which is located in an ethnically diverse community, including people from a range of Asian and Pacific island countries. It will therefore provide advanced technological training and mentoring of science students with diverse cultural backgrounds. Theory and preliminary observations indicate that the removal of ice at the end of the last glacial period profoundly affected volcanic production and magma chemistry in Iceland. The project investigators will constrain the timing of glacial retreat using ice core data and geologic reconstructions for the period between 15 and 11 thousand years before present. They will use new geologic mapping and sample collections, geochemical analyses, and 3He exposure age dating of subaerial lavas that surmount late-glacial table mountains to extend the record of eruption rates and lava composition back to 15 ka. Numerical models will simulate the updated glacial unloading history as well as the resulting perturbations to mantle melting, melt migration, and chemical transport. By modeling the observed temporal variations in eruption rate and trace-element and isotopic compositions, they will constrain the rates of melt transport, determine basic properties of the mantle melt column, and test for the presence of small-scale mantle heterogeneity.