Deep seismic imaging the evolution of continental lithosphere

深地震成像大陆岩石圈的演化

• 批准号: RGPIN-2018-04185
• 负责人: Calvert, Andrew
• 金额: $ 2.62万
• 依托单位: Simon Fraser University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=751125
• 关键词: Deep; seismic; imaging; evolution; continental

Earth's tectonic processes have changed dramatically as the planet has cooled. Soon after its formation 4.5 billion years ago, Earth's surface comprised a thick immobile mafic crust marked by extensive volcanism, perhaps punctuated by major resurfacing events, as plumes transported heat upward in a chaotic mantle convection regime. Approximately 3.0-3.5 billion years ago, a form of embryonic, transient plate tectonics developed, which eventually evolved into the well organised plate tectonic system we observe today. Earth's continents have recorded the effects of over four billion years of this tectonic activity, but the nature of these early tectonic processes remains controversial with vertical subsidence of the dense early crust often invoked as an alternative to horizontal processes tied to seafloor spreading and subduction. Our understanding of the early Earth comes from a wide variety of geoscientific data and increasingly sophisticated numerical geodynamic simulations, which can predict the deformation of the crust and upper mantle in various scenarios. Since deep seismic reflection surveys can reveal in detail structures preserved in the continental lithosphere from earlier episodes of tectonic deformation, these surveys provide an ideal way to verify the predictions of geodynamic modelling, and their depth constraints are a critical complement to geological mapping at the surface. High quality seismic data recently recorded in Australia build upon extensive Canadian datasets from the Lithoprobe program, and provide an unprecedented insight into the structure of ancient continental crust. The objective of the proposed research is to use seismic reflection data, integrated with a broad range of geological and geochronological data, to determine the nature of the changing tectonic processes that operated early in Earth history from creation of the first microcontinents to assembly of the stable cores of today's continents. Using new methods developed to determine 3-D reflector orientations in crooked 2-D surveys, it is now possible to better distinguish multiple episodes of tectonic deformation. With my students, I will study the assembly and subsequent collapse of Archean crust, which probably has no modern equivalent, determine the nature of lower crustal flow, and reveal the setting of Archean greenstone belts that host much of Earth's gold and base metal resources. Seismic surveys indicate that a significant change in the nature of continental assembly occurred during, or just prior to, the Early Proterozoic, with the underthrusting of very thick crustal sections, which may be related to the growth of strong cratonic roots. We will develop methods to distinguish domains in the uppermost mantle by their dominant reflector orientation, aiming to determine if they formed by processes such as magmatism, continental subsidence, or imbrication of subducted slabs.

随着地球的冷却，地球的构造过程发生了巨大变化。在45亿年前形成45亿年后不久，地球的表面包括厚厚的火山岩层，以广泛的火山为标志，可能是重大重塑事件的刺激，因为羽毛在混乱的地幔对流方向上向上传输热量。大约30-35亿年前，开发了一种胚胎，瞬态板岩构造形式，最终进化为我们今天观察到的组织良好的板块构造系统。地球大陆记录了这种构造活动超过40亿年的影响，但是这些早期的构造过程的性质仍然引起争议，而垂直沉降的垂直沉降通常被引用为与海底扩散和俯冲相关的水平过程的一种替代方法。我们对早期地球的理解来自多种地球科学数据和越来越复杂的数值地球动力学模拟，这些模拟可以预测各种情况下地壳和上地幔的变形。由于深层地震反射调查可以从较早的构造变形的早期发作中保存在大陆岩石圈中的详细结构中，因此这些调查提供了验证地球动力学建模预测的理想方法，其深度约束是对地面地质图的关键补充。最近在澳大利亚记录的高质量地震数据建立在岩杆螺旋桨计划的广泛数据集的基础上，并对古代大陆壳的结构提供了前所未有的见解。拟议的研究的目的是使用与广泛的地质和地质学数据集成的地震反射数据，以确定从创建第一个微观构成到当今大陆稳定核心的组装的地球历史早期经营的不断变化的构造过程的性质。使用开发的新方法来确定弯曲的二维调查中的3-D反射器方向，现在可以更好地区分构造变形的多个发作。与我的学生一起，我将研究可能没有现代等效的大将壳的组装和随后的崩溃，确定了下层地壳的性质，并揭示了拥有地球大部分黄金和倒数金属资源的Archean Greenstone带的设置。地震调查表明，大陆装配的性质发生了重大变化，发生在早期的proterorocic期间，或者是在早期的proteroyoic期间发生的，并且构成了非常厚的地壳切片，这可能与强cratonic根部的生长有关。我们将开发方法来通过其主要反射剂取向区分最高地幔中的域，旨在确定它们是由岩浆，大陆沉降或俯冲板的嵌入等过程形成的。