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.

一般描述：该项目旨在揭示岩浆源区域，分期区域和爆发途径。这座火山是一种被称为Phonolitic的末端型，它是指熔岩成分，几乎是纯二氧化碳的含量，并且发生在大陆裂谷环境中。这与在板边界设置（例如圣海伦斯山或富士山）处发生的较知名的含水火山相反。 其他地方（例如Tamboro或Vesuvius）的语音火山喷发造成了50,000多次与爆发有关的死亡。音载也与稀土元素的沉积物有关，从而使它们具有经济利益。为了阐明Erebus山的内部运作，我们将使用基于磁铁（MT）测量的密集地球物理探针网络覆盖火山。 MT利用自然存在的电磁（EM）波，主要由太阳产生，以提供地球内部电导率结构的图像。电导率对地球中的流体和熔体的存在敏感，因此非常适合理解火山过程。该项目是美国，新西兰，日本和加拿大科学家之间的合作努力。它实施了由主要研究人员和同事开发的新技术，该技术允许在雪覆盖的地形上进行此类测量。这通常适用于通常的冷冻环境，例如北极中的资源探索。该项目支持一名新的博士后研究人员，并利用其他机构的支持并与商业平台交互开发的成像和测量方法。技术描述：研究人员建议使用Magnettotelluric（MT）方法测试南极洲Erebus火山的岩浆进化模型。 Erebus山上的语音熔岩流组合物并不常见，但为上套源源组成和熔体分化路径提供了一个窗口。爆炸性的语音爆发因tambora和Vesuvius等毁灭性喷发而在全球范围内闻名，并且通常是稀土元素沉积物。在MT方法中，将地球自然电磁（EM）场的时间变化用作探测1至100公里深度范围内的电阻率结构的源场。 这项工作将由大约100吨站点组成，在山顶区域中有一定的浓度。现场收购将在两个实地季节进行。主要目标是1）确认最高的岩浆室的存在和几何形状，被认为位于5-10公里的深度； 2）试图在更深的电阻率结构中识别地壳螺栓边界附近的岩浆分期； 3）图像陡峭的地壳尺度，近垂直的导管从地幔中载着岩浆； 4）从二氧化碳主导的镁铁质盾牌火山的地球物理特性中推断出物理和化学状态； 5）限制与恐怖裂谷有关的结构与岩浆/水热活动之间的关系。基于可变形的边缘有限元方法，将使用在犹他州开发的新反转平台进行内部电阻率的层析成像成像，该方法最适合容纳研究区域的陡峭地形。该项目是犹他大学，GNS科学惠灵顿新西兰（G. Hill，Co-I）与日本东京理工学院（Y. Ogawa，Co-I）之间的国际合作，以及艾伯塔大学（M. Unsworth）和密苏里州州立大学（K. Mickus）的参与。仪器部署将由直升机专门进行。该项目实施了允许在雪覆盖的地形上进行MT测量的新技术。该项目支持一名新的博士后研究人员，并利用其他机构的支持并与商业平台相连开发的成像和测量方法。