Towards a Lithospheric History of North America

走向北美岩石圈历史

• 批准号: RGPIN-2015-04933
• 负责人: Frederiksen, Andrew
• 金额: $ 1.6万
• 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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=613262
• 关键词: Towards; Lithospheric; History; North; America

The Earth's lithosphere represents a boundary layer between the convective processes of the deep Earth and the tectonic processes that define the history of the crust. Understanding the relationship between plate tectonics at the surface and mantle dynamics at depth, and how this relationship has changed over time, requires knowledge of the structure of the lithosphere at a level of detail comparable to the major crustal tectonic blocks. My program is to map the continental lithosphere through seismic methods, relate lithospheric features to crustal bodies of known age, and develop a history of lithospheric processes that extends through the full thickness of the plate. The largest-scale aspect of this program is production of a new tomographic model of the Canadian lithosphere using two-station analysis of surface waves. In this approach, the change in waveform between two instruments aligned along a common path to the source is examined, producing a dispersion curve related to the laterally-averaged structure along the path between the instruments. Given a large set of instruments, we can build a grid of intersecting paths on which the average structure is known; combining the paths via tomographic inversion yields 3-D images of structure. I propose to combine existing and new dispersion-curve data to form a 3-D image of the lithosphere across Canada. Existing North American models are largely based on single-station methods which are poorly adapted to low-seismicity settings like the Canadian Shield; the model produced by this technique will thus provide a novel constraints on the structure and dynamics of the North American lithosphere and the relationship between crustal geology and upper-mantle structures. I further propose to instrument the Trans-Hudson Orogen, west of the Superior, to fill in the largest gap in Canadian instrument coverage. More focused studies are also proposed here, based on data from the Mid-Continent Rift, a billion-year-old rift structure curving through the Great Lakes. A new data set from this region has become available as of 2013, via the international SPREE project. I propose two student projects to examine crustal and lithospheric fabric across the rift axis and in the adjacent Superior Province, to explore the effect of the rifting process on the lithosphere, the role of lithospheric factors in the rifting process, and the imprint of the Superior accretionary process on lithospheric fabric; new techniques for measuring lithospheric fabric in detail will be explored. A related study will examine a similar data set from a contemporary rift -- the Main Ethiopian Rift -- in order to compare fossil and active rift structures.   Better constraints on Canadian lithospheric structure will have large-scale impact on Canadian geology, through a better understanding of lithospheric participation in tectonic events, and will assist in large-scale mineral exploration.

地球的岩石圈代表了地球深部对流过程和地壳构造过程之间的边界层。要了解地表板块构造与深部地幔动力学之间的关系，以及这种关系如何随时间而变化，就需要了解岩石圈结构的详细程度，可以与主要的地壳构造块体相媲美。我的计划是通过地震方法绘制大陆岩石圈图，将岩石圈特征与已知年龄的地壳体联系起来，并发展贯穿板块全厚度的岩石圈过程史。 该计划的最大规模的方面是生产一个新的断层模型的加拿大岩石圈使用两个站的表面波分析。在这种方法中，检查沿沿着到源的公共路径对准的两个仪器之间的波形变化，产生与沿仪器之间的路径沿着的横向平均结构相关的频散曲线。给定一个大的仪器组，我们可以建立一个交叉路径的网格，其上的平均结构是已知的;通过层析反演结合路径产生结构的3D图像。我建议结合联合收割机现有的和新的色散曲线数据，形成一个横跨加拿大的岩石圈的三维图像。现有的北美模型主要是基于单站的方法，这是不适应低地震活动设置，如加拿大地盾，这种技术产生的模型将提供一个新的约束结构和动力学的北美岩石圈和地壳地质和上地幔结构之间的关系。我还建议在上级以西的哈德逊造山带上安装仪器，以填补加拿大仪器覆盖范围的最大空白。 这里也提出了更有针对性的研究，基于来自中大陆裂谷的数据，这是一个弯曲穿过五大湖的十亿年前的裂谷结构。截至2013年，通过国际SPREE项目，该区域的一套新数据已经可用。我提出了两个学生的项目，检查地壳和岩石圈结构的裂谷轴和相邻的上级省，探讨裂谷过程对岩石圈的影响，岩石圈因素在裂谷过程中的作用，和印记的上级增生过程对岩石圈结构，将详细探讨测量岩石圈结构的新技术。一项相关的研究将检查来自当代裂谷-埃塞俄比亚主裂谷-的类似数据集，以便比较化石和活动裂谷结构。   通过更好地了解岩石圈参与构造活动，对加拿大岩石圈结构的更好约束将对加拿大地质产生大规模影响，并将有助于大规模矿产勘探。