Magma Sources, Residence and Pathways of Mount Erebus Phonolitic Volcano, Antarctica, from Magnetotelluric Resistivity Structure

从大地电磁电阻率结构看南极洲埃里伯斯火山的岩浆源、居住地和路径

• 批准号: 1443522
• 负责人: Philip Wannamaker
• 金额: $ 43.88万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1443522&HistoricalAwards=false
• 关键词: Magma; Sources; Residence; Pathways; Mount

General Description:This project is intended to reveal the magma source regions, staging areas, and eruptive pathways within the active volcano Mount Erebus. This volcano is an end-member type known as phonolitic, which refers to the lava composition, and is almost purely carbon-dioxide-bearing and occurs in continental rift settings. It is in contrast to the better known water-bearing volcanoes which occur at plate boundary settings (such as Mount St Helens or Mount Fuji). Phonolitic volcanic eruptions elsewhere such as Tamboro or Vesuvius have caused more than 50,000 eruption related fatalities. Phonolites are also associated with rare earth element deposits, giving them economic interest. To illuminate the inner workings of Mount Erebus, we will cover the volcano with a dense network of geophysical probes based on magnetotelluric (MT) measurements. MT makes use of naturally occurring electromagnetic (EM) waves generated mainly by the sun as sources to provide images of the electrical conductivity structure of the Earth's interior. Conductivity is sensitive to the presence of fluids and melts in the Earth and so is well suited to understanding volcanic processes. The project is a cooperative effort between scientists from the United States, New Zealand, Japan and Canada. It implements new technology developed by the lead investigator and associates that allows such measurements to be taken on snow-covered terrains. This has applicability for frozen environments generally, such as resource exploration in the Arctic. The project supports a new post-doctoral researcher, and leverages imaging and measurement methods developed through support by other agencies and interfaced with commercial platforms.Technical Description:The investigators propose to test magmatic evolution models for Mount Erebus volcano, Antarctica, using the magnetotelluric (MT) method. The phonolite lava flow compositions on Mount Erebus are uncommon, but provide a window into the range of upper mantle source compositions and melt differentiation paths. Explosive phonolite eruptions have been known worldwide for devastating eruptions such as Tambora and Vesuvius, and commonly host rare earth element deposits. In the MT method, temporal variations in the Earth's natural electromagnetic (EM) field are used as source fields to probe the electrical resistivity structure in the depth range of 1 to 100 kilometers. This effort will consist of approximately 100 MT sites, with some concentration in the summit area. Field acquisition will take place over two field seasons. The main goals are to 1) confirm the existence and the geometry of the uppermost magma chamber thought to reside at 5-10 kilometer depths; 2) attempt to identify, in the deeper resistivity structure, the magma staging area near the crust-mantle boundary; 3) image the steep, crustal-scale, near-vertical conduit carrying magma from the mantle; 4) infer the physical and chemical state from geophysical properties of a CO2-dominated mafic shield volcano; and 5) constrain the relationships between structural and magmatic/ hydrothermal activity related to the Terror Rift. Tomographic imaging of the interior resistivity will be performed using a new inversion platform developed at Utah, based on the deformable edge finite element method, that is the best available for accommodating the steep topography of the study area. The project is an international cooperation between University of Utah, GNS Science Wellington New Zealand (G. Hill, Co-I), and Tokyo Institute of Technology Japan (Y. Ogawa, Co-I), plus participation by University of Alberta (M. Unsworth) and Missouri State University (K. Mickus). Instrument deployments will be made exclusively by helicopter. The project implements new technology that allows MT measurements to be taken on snow-covered terrains. The project supports a new post-doctoral researcher, and leverages imaging and measurement methods developed through support by other agencies and interfaced with commercial platforms.

概述：该项目旨在揭示活动火山埃里伯斯山内的岩浆源区、集结区和喷发路径。这座火山是一种被称为响岩的端元类型，指的是熔岩成分，几乎纯含二氧化碳，发生在大陆裂谷环境中。它与更著名的含水火山形成对比，后者发生在板块边界（如圣海伦山或富士山）。 在其他地方，如Tamboro或Vesuvius的响岩火山爆发已造成超过50，000人死亡。辉铜矿还与稀土元素矿床有关，使其具有经济利益。为了阐明埃里伯斯山的内部运作，我们将在火山上覆盖一个基于大地电磁（MT）测量的密集地球物理探测网络。MT利用主要由太阳产生的自然发生的电磁（EM）波作为源，提供地球内部导电结构的图像。电导率对地球中流体和熔体的存在很敏感，因此非常适合于了解火山过程。该项目是来自美国、新西兰、日本和加拿大的科学家之间的合作努力。它采用了首席调查员和同事开发的新技术，使这种测量能够在积雪覆盖的地形上进行。这适用于一般的冰冻环境，例如北极的资源勘探。该项目支持一名新的博士后研究人员，并利用通过其他机构的支持开发的成像和测量方法，并与商业平台对接。技术说明：研究人员建议使用大地电磁法（MT）测试南极洲埃里伯斯火山的岩浆演化模型。埃里伯斯山的响岩熔岩流成分是不常见的，但提供了一个窗口，上地幔源成分和熔体分异路径的范围。响岩爆发在世界范围内以毁灭性的喷发而闻名，如坦博拉和维苏威火山，通常含有稀土元素矿床。在MT方法中，地球的天然电磁（EM）场的时间变化被用作源场，以探测1至100公里深度范围内的电阻率结构。 这 这项工作将包括大约100个MT站点，其中一些集中在山顶地区。实地收购将在两个实地季节进行。其主要目的是：1）确认最上层岩浆房的存在及其几何形状，该岩浆房被认为位于5-10公里深处; 2）试图在更深的电阻率结构中识别壳幔边界附近的岩浆分期区; 3）成像陡峭的、地壳尺度的、近垂直的从地幔输送岩浆的管道; 4）从地球物理性质推断CO2主导的镁铁质盾状火山的物理和化学状态; 5）限制与恐怖裂谷有关的构造和岩浆/热液活动之间的关系。内部电阻率的层析成像将使用犹他州开发的新的反演平台进行，该平台基于变形边缘有限元法，该方法是适应研究区域陡峭地形的最佳方法。该项目是犹他州大学、GNS科学惠灵顿新西兰（G。Hill，Co-I）和日本东京工业大学（Y。Ogawa，Co-I），加上阿尔伯塔大学（M. Unsworth）和密苏里州州立大学（K。Mickus）。仪器部署将完全由直升机进行。该项目采用了新技术，允许在积雪覆盖的地形上进行MT测量。该项目支持一名新的博士后研究人员，并利用通过其他机构的支持开发的成像和测量方法，并与商业平台对接。