The subcontinental lithosphere-asthenosphere boundary

我们对岩石圈（地球坚硬的外壳）的认识主要局限于它的上部区域。岩石圈-软流圈边界（LAB）形成了构造板块的基础，其深度从洋中脊的有效零到古大陆核下100公里处存在厚岩石圈龙骨的地方不等。作为一种机械分离，它容纳了板块和底层更容易变形的软流层之间的相对运动，拉布拉多构成了地球上最广泛的板块边界。然而，即使是基本的物理参数也仍然不确定，特别是在大陆之下；这些因素包括岩浆带的深度、向下过渡到软流圈的厚度、流体的丰度和分布，以及驱动（或阻碍）板块运动和影响板块内地震的基底牵引力的大小。这些参数以各种地球物理观测值表示，包括纵波和横波速度以及地震各向异性。该研究计划将采用被动地震学方法，包括表面波断层扫描、矩张量反演和s接收函数分析，以及大陆上地幔热流变演化的数值模拟，对选定地区的次大陆LAB进行研究。研究区域位于哈德逊湾、艾伯塔省和摩洛哥附近，分别在大陆下的古代岩石圈龙骨内部、边缘附近和邻近不同的区域取样。将有1名硕士生、5名博士生、2名博士后和5名本科生接受学术培训。通过提高我们对构造板块基础和大陆岩石圈内部结构的认识，这项工作将解决有关板块构造驱动力以及大陆如何形成并与底层地幔对流系统相互作用的基本科学问题。这些知识的实际应用包括指导钻石勘探和提高我们对控制板内地震因素的理解。

Our knowledge of the lithosphere, Earth's rigid outer shell, is mainly confined to its upper regions. The lithosphere-asthenosphere boundary (LAB) forms the base of tectonic plates and varies in depth from effectively zero at mid-oceanic ridges to 100's km beneath ancient continental nuclei, where thick lithospheric keels exist. As a mechanical detachment that accommodates relative motion between the plate and underlying, more easily deformed asthenosphere, the LAB constitutes the most extensive class of plate boundary on Earth. Yet, even fundamental physical parameters remain uncertain, particularly beneath continents; these include depth of the LAB, thickness of the downward transition into asthenosphere, abundance and distribution of fluids, as well as the magnitude of basal traction forces that drive (or impede) plate motion and influence intraplate earthquakes. These parameters are expressed in various geophysical observables, including P- and S-wave velocities and seismic anisotropy. This proposed research program will investigate the subcontinental LAB in selected regions using passive seismological methods, including surface-wave tomography, moment-tensor inversion and analysis of S-receiver functions, coupled with numerical simulations of the thermal and rheological evolution of the continental upper mantle. The study areas, located around Hudson Bay, Alberta and Morocco, sample diverse regions that are, respectively, within, near the margin of, and adjacent to ancient lithospheric keels beneath continents. One M.Sc. student, 5 doctoral students, 2 postdoctoral fellows and 5 senior undergraduate students will receive academic training as part of this research program. By improving our knowledge of the base of tectonic plates and internal architecture of continental lithosphere, this work will address fundamental scientific questions about driving forces of plate tectonics and how continents form and interact with underlying mantle convection systems. Practical applications of this knowledge include guiding exploration for diamonds and improving our understanding of factors that control intraplate earthquakes.