Collaborative Research: Growth, Assembly, and Exhumation of Deep Crust, Southwestern Churchill Province, Canadian Shield

加拿大西部的丘吉尔省保存了早期大陆地壳生长、演化、折返和稳定过程的非凡地质记录。 特别是东阿萨巴斯卡地区暴露出一大片（1000平方公里）的岩石，这些岩石在20公里以上的深度被加热到近1000摄氏度的温度。 事实上，一些岩石是在北美有史以来最高的压力下形成的。 该地区可以分为许多小的区域，保留不同的岩石类型和地质历史。 每一个单独的域记录，令人印象深刻的清晰度，在加拿大地盾的构造演化的关键阶段。它们一起提供了一个复杂性的地图视图，可以概括地描述深部地壳的特征。 由于地壳深部通常无法进行研究，这一区域为了解地壳深处发生的事情提供了一个独特的视角。 在东阿萨巴斯卡地区的实地和实验室研究记录了一个更年轻的事件（19亿年前）的影响，该事件改变了这些岩石，导致假设该地区代表了19亿年前在地壳深处组装的域的地图视图，然后立即被抬升和暴露。 因此，该区域可以提供对岩石类型、结构和几公里波长的不均匀性的直接观察，这些岩石类型、结构和不均匀性通过地震成像或推断存在于地壳深部未暴露的其他地区。 加强这一假设的关键是更好地理解各个域的内部结构及其边界。该项目的目标是了解（1）非均匀深地壳域的组合;（2）19亿年前变质作用的意义和原因;（3）从地球深处向深地壳添加熔体的作用;（4）如何挖掘出巨大的深地壳岩石;以及（5）这些岩石在北美西部更广泛的背景下的背景。 这种综合方法对地壳组装、稳定化和折返过程中下地壳的性质、行为和演化施加了重要的一阶约束。

The western Churchill Province of Canada preserves an extraordinary geologic record of processes active during the growth, evolution, exhumation, and stabilization of early continental crust. The East Athabasca area in particular exposes a huge tract (1000's of km2) of rocks that were heated to temperatures of nearly 1000 deg C at depths of more than 20 km. In fact some of the rocks were formed at the highest pressures ever recognized in North America. The region can be divided into a number of small domains that preserve distinct rock types and geological histories. Each of the individual domains record, with impressive clarity, key stages in the tectonic evolution of the Canadian shield. Together, they provide a map view of the complexity that may characterize the deep crust in general. Since the deep crust is generally not accessible for study this area provides a unique view of what happens deep in the earth's crust.Most of the rocks in this study are about 2.6 billion years old. Field and laboratory research in the East Athabasca area documents the effects of a much younger event (1.9 billion years ago) that has transformed these rocks leading to the hypothesis that the area represents a map view of domains assembled in the deep crust 1.9 billion years ago immediately prior to being uplifted and exposed. As such, the region may provide a direct view of the rock types, structures, and heterogeneity at several km wavelengths that are seismically imaged or inferred to exist in other areas where the deep crust is not exposed. Crucial to strengthening this hypothesis is a better understanding of the internal structure of individual domains and their boundaries. Goals of this project are to understand (1) the assembly of heterogeneous deep crustal domains; (2) the significance and cause of metamorphism 1.9 billion years ago; (3) the role of adding melts from deep within the earth to the deep crust (4) how an enormous area of deep crustal rocks can be exhumed; and (5) the setting of these rocks within the broader context of western North America. This integrated approach is placing important first-order constraints on the character, behavior, and evolution of lower crust during crustal assembly, stabilization, and exhumation.