Electromagnetic imaging of continental lithosphere

大陆岩石圈电磁成像

• 批准号: 105748-2007
• 负责人: Ferguson, Ian
• 金额: $ 1.64万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=365751
• 关键词: Electromagnetic; imaging; continental; lithosphere

The theory of plate tectonics describes how the rigid plates at the surface of the Earth are formed and destroyed, and how they move over a time scale of millions of years. These plates, which may contain continents or oceans or both, make up a rigid outer shell of the Earth called the lithosphere. My research involves improving our understanding of how continental lithosphere forms, how it preserved, and how it has been changed after its formation. I am focussing on studying the lithosphere of the Precambrian shield in central Canada that was formed between about  one and three billion years ago.  Seismic and electromagnetic geophysical methods can provide detailed images of the upper several hundred kilometres of the Earth. These images can show how how thick the lithosphere is, how heterogenous it is, how different parts of the lithosphere were amalgamated, and whether the lithosphere has been significantly changed since it first formed. My research involves using electromagnetic methods which provide images of the electrical conductivity. Studies involve recording and analyzing low-frequency electromagnetic (EM) signals produced in the ionosphere (often during auroral activity) and in the atmosphere (during thunderstorms). Signals with different frequencies flow through the ground at different depths enabling the measurement of electrical conductivity over a range of depths. The varying conductivity within the Earth depends on the presence of conductive minerals such as oxides, sulphides, and graphite and the on presence of fluids such as water and magma. In turn this information is related to the types of rock present and the geological structure and history.

板块构造理论描述了地球表面的刚性板块是如何形成和摧毁的，以及它们如何在数百万年的时间尺度上移动。这些板块可能包含大陆或海洋，或者两者兼而有之，它们构成了一个坚硬的地球外壳，称为岩石圈。我的研究涉及提高我们对大陆岩石圈如何形成、如何保存以及在形成后如何变化的理解。我正在重点研究加拿大中部前寒武纪地盾的岩石圈，它形成于大约10亿到30亿年前。现在的地震和电磁地球物理方法可以提供地球上部数百公里的详细图像。这些图像可以显示岩石圈有多厚，它的非均质性有多大，岩石圈的不同部分是如何融合的，以及岩石圈自最初形成以来是否发生了重大变化。我的研究涉及使用电磁方法，这些方法提供了导电性的图像。研究涉及记录和分析电离层(通常在极光活动期间)和大气层(在雷暴期间)产生的低频电磁信号。具有不同频率的信号在不同深度流经地面，从而能够测量一定深度范围内的电导率。地球内部不同的电导率取决于氧化物、硫化物和石墨等导电矿物的存在，以及水和岩浆等流体的存在。反过来，这些信息又与存在的岩石类型以及地质结构和历史有关。