Advanced Seismic Imaging of Eastern Canadian Margins and Crustal Analogues

加拿大东部边缘和地壳类似物的高级地震成像

• 批准号: 8459-2012
• 负责人: Louden, Keith
• 金额: $ 1.97万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2013
• 资助国家: 加拿大
• 起止时间: 2013-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=521133
• 关键词: Advanced; Seismic; Imaging; Eastern; Canadian

Rifted continental margins form by extension and breakup of the continental lithosphere, as one major component of the Earth's plate tectonic cycle. They also contain major deposits of the world's hydrocarbon resources. The nature of rifting varies dramatically by the amount of melt produced: from margins with little or no melt (magma-poor) to margins with large volumes of melt (magma-rich). The purpose of this proposal is to investigate the nature of the rifting process by imaging structures formed across the rifted margins of eastern Canada and analogues of these structures on the Southeast Indian Ridge. Reconstructing the geometry of the crust and sediment throughout their extensional histories and comparing these geometries with theoretical model archetypes will help to identify fundamental attributes of the extensional processes. Three key elements are to better understand: i) the depth-dependent distribution of continental crustal deformation, ii) the nature of basement and mantle within the ocean-continent transition zone and on ultraslow mid-ocean ridges, and iii) the cause of variations between magma-rich and magma-poor rifting. Existing images can define the basic overall structure of margins but specific regions or transitions within such images are often poorly defined. For instance, the ocean-continent transition zone can exhibit complex structures, including highly extended continental crust, exposed mantle and thin oceanic crust, which are difficult to distinguish with existing data. These complexities are critically important for an improved understanding of such widely-held concepts as the continent-ocean boundary, the breakup unconformity, and the nature of early oceanic seafloor spreading. Occurrences of exhumed mantle in similar rifted margin settings have also been recognized in continental orogens, such as the Alps and the northern Canadian Cordillera. These studies thus have broad application to a wide range of fundamental Earth processes with additional applied value to further understanding the formation of offshore hydrocarbon resources.

裂谷大陆边缘是大陆岩石圈伸展和裂解的产物，是地球板块构造旋回的主要组成部分。它们还拥有世界碳氢化合物资源的主要矿藏。裂谷作用的性质因所产生的熔体量而变化很大：从几乎没有熔体的边缘（岩浆贫乏）到有大量熔体的边缘（岩浆丰富）。本提案的目的是通过对加拿大东部裂谷边缘形成的构造以及东南印度洋脊上这些构造的类似物进行成像来调查裂谷过程的性质。重建地壳和沉积物的几何形状，在其整个拉伸历史和比较这些几何形状与理论模型原型将有助于确定拉伸过程的基本属性。三个关键要素是更好地理解：i）大陆地壳变形的深度依赖性分布，ii）洋-陆过渡带和超低洋中脊的基底和地幔的性质，以及iii）富岩浆和贫岩浆裂谷之间的变化原因。现有的图像可以定义边缘的基本整体结构，但这些图像中的特定区域或过渡通常定义不好。例如，洋-陆过渡带可能呈现复杂的结构，包括高度伸展的大陆地壳、暴露的地幔和薄洋壳，这是很难用现有数据区分的。这些复杂性对于更好地理解诸如大陆-海洋边界、断裂不整合和早期大洋海底扩张的性质等广泛持有的概念至关重要。在大陆造山带，如阿尔卑斯山和北方加拿大科迪勒拉山脉，也发现了类似的裂谷边缘环境中的折返地幔。因此，这些研究对广泛的基本地球过程具有广泛的应用价值，对进一步了解近海碳氢化合物资源的形成具有额外的应用价值。