Measuring the depth extent of processes driving the tectonic evolution of North America

测量驱动北美构造演化过程的深度范围

• 批准号: RGPIN-2017-03946
• 负责人: Gilbert, Hersh
• 金额: $ 1.6万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=678774
• 关键词: Measuring; depth; extent; processes; driving

The accretion of rifted continental margin fragments, island arcs, and oceanic plateaus onto the western margin of North America has contributed to its growth since the Mesozoic. However, Precambrian ages of the upper mantle underlying these terranes in the Canadian Cordillera indicate that they are underlain by older lithosphere. It would therefore appear that the orogenic processes associated with the growth of this portion of North America were limited to the shallow crust. Contrasting ages between terranes at the surface and deeper structures represent a clear departure in tectonic style from other orogenic systems where the crust and its underlying mantle possess a similar evolutionary history. The research program proposed here seeks to understand the mechanisms by which terranes combine to form continents and will accomplish this goal by surveying the crust and upper mantle of the western margin of North America. Determining the present-day structure of the crust and upper mantle within suture zones that juxtapose formerly disparate terranes, and comparing their structures to stable continental regions, will clarify the process of continental growth. The short-term objectives of this program will be to systematically map the structure of the crust and upper mantle within and across terranes utilizing existing datasets from the northern cordillera of North America. ******This program will additionally collect new broadband seismic data along a profile spanning from the Canadian Cordillera into the interior of North America. New broadband seismic data recorded by arrays located at this sharp lateral gradient in surface deformation will help characterize how the lithosphere changes at this structural boundary at the surface. Integrating observations from new and already available seismic datasets will yield insights into the properties that characterize portions of the crust and upper mantle that have been deformed and how those differ from regions that resist deformation. These observations will address the long-term objective of this study to identify the factors responsible for intraplate deformation in western North America. This long-term goal will be accomplished by answering the following questions: (1) How do the combined contributions from gravitational potential energy and boundary forces cause deformation within the interior of continents? (2) In what ways do the structures of terranes change as they are integrated into continents? And (3) What structures or processes in the lower crust and upper mantle influence surface tectonics? This program will benefit the geoscience community by increasing our understanding of a fundamental aspect of continental evolution. Additionally, the population in and around the Canadian Cordillera will benefit from improved understanding of crustal and upper mantle structures that can be responsible for regional seismic hazards.

自中生代以来，裂谷大陆边缘碎片、岛弧和大洋高原在北美西部边缘的沉积促进了北美的增长。然而，加拿大科迪勒拉地区这些地体下面的上地幔的前寒武纪时代表明，它们是被更古老的岩石圈覆盖的。因此，与北美这一部分的生长有关的造山过程似乎仅限于地壳浅层。地表地体和深层结构的年龄对比表明，地壳及其下部地幔具有相似演化史的其他造山系统在构造样式上明显不同。这里提出的研究计划试图了解地体结合形成大陆的机制，并将通过调查北美西部边缘的地壳和上地幔来实现这一目标。确定与以前不同的地体并列的缝合带内地壳和上地幔的现代结构，并将它们的结构与稳定的大陆地区进行比较，将有助于阐明大陆增长的过程。该方案的短期目标将是利用北美北部考迪拉的现有数据集，系统地绘制地体内部和跨地体的地壳和上地幔结构图。*该计划还将沿着从加拿大科迪勒拉到北美内陆的剖面收集新的宽带地震数据。位于地表形变这一尖锐横向梯度的阵列记录的新的宽带地震数据将有助于描述岩石圈在地表这一构造边界处的变化。综合来自新的和已有的地震数据集的观测结果，将深入了解地壳和上地幔已变形部分的特性，以及这些特性与抵抗变形的区域有何不同。这些观察将解决这项研究的长期目标，以确定导致北美西部板内变形的因素。这一长期目标将通过回答以下问题来实现：(1)重力势能和边界力的综合作用如何导致大陆内部的变形？(2)当地体整合成大陆时，它们的结构以什么方式变化？以及(3)下地壳和上地幔中的什么结构或过程影响地表构造？这项计划将通过增加我们对大陆演化的一个基本方面的理解，使地球科学界受益。此外，加拿大科迪勒拉及其周围的人口将受益于对地壳和上地幔结构的更好了解，这些结构可能是区域性地震灾害的原因。