Very-Long-Period Investigation of the Mantle Beneath the Canadian Shield: A Lakebottom Magnetotelluric Observatory

板块构造模型的一个主要特征是地球表面的热边界层的概念。这一边界层作为驱动板块运动的对流系统的上边界，并受传导热区的支配。热流、下沉和其他数据被用来证明旧洋盆和旧大陆下的深部结构没有显著差异，这两个盆地都处于或非常接近热平衡状态。这表明大陆岩石圈和大洋岩石圈在平衡状态下具有相同的厚度，约为150公里。上层岩石圈和地壳必须存在差异，才能解释大陆物质的浮力和力学行为，这有助于控制其在板块构造中的作用。已经提出了一些关于大陆深层结构的相互竞争的模型，这些模型将通过估计加拿大盾下的深层电导率结构来进行测试。电导率是一个热激活过程，应该对与大陆岩石圈的不同模型有关的根本不同的深次屏蔽地幔条件非常敏感。PI将在一个深淡水湖的底部运行一个甚长周期(VLP)大地电磁观测站。这一创新的部署方案克服了以前在获取VLP MT数据时遇到的许多困难。

A major feature of the plate tectonic model is the concept of a thermal boundary layer (TBL) at the earth's surface. This TBL serves as the upper boundary of the convective systems which drive the plate motions, and is dominated by a conductive thermal regime. Heat flow, subsidence, and other data have been used to argue for no significant differences between the deep structures under old ocean basins and old continents, both of which are at or very near a thermal equilibrium state. This suggests that the continental and oceanic lithospheres have the same thickness of about 150 km at equilibrium. Differences must exist in the upper lithosphere and crust to explain the buoyancy and mechanical behavior of continental material which helps govern its role in plate tectonics. A number of competing models for the deep structure of the continents have been proposed which will be tested by estimating the deep electrical conductivity structure beneath the Canadian Shield. The conductivity is a thermally activated process, and should be extremely sensitive to the radically different deep sub-shield mantle conditions associated with differing models of the continental lithosphere. The PIs will operate a very long period (VLP) magnetotelluric observatory in the bottom of a deep freshwater lake. This innovative deployment scheme overcomes many of the difficulties previously encountered in obtaining VLP MT data.