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

加拿大西部丘吉尔省保存了早期大陆地壳生长、演化、折返和稳定过程中活动的非凡地质记录。尤其是东阿萨巴斯卡地区暴露出一大片岩石(1000‘S平方公里)，这些岩石在20多公里深处被加热到近1000摄氏度的温度。事实上，其中一些岩石是在北美有史以来最高的压力下形成的。该地区可划分为多个小区域，保存着不同的岩石类型和地质历史。每个单独的域都以令人印象深刻的清晰度记录了加拿大地盾构造演化的关键阶段。它们共同提供了一幅地图，展示了地壳深部总体上可能具有的复杂性。由于深部地壳一般无法进行研究，这一区域提供了地球地壳深处发生的独特景象。这项研究中的大多数岩石大约有26亿年的历史。东阿萨巴斯卡地区的野外和实验室研究记录了一次更年轻的事件(19亿年前)的影响，该事件改变了这些岩石，导致了该地区代表了19亿年前就在隆起和暴露之前聚集在地壳深处的区域的地图视图。因此，该地区可以提供几公里波长的岩石类型、结构和不均质性的直接视图，这些岩石类型、结构和不均质性在地震成像或推断存在于其他未暴露地壳的地区。加强这一假设的关键是更好地理解各个领域的内部结构及其边界。该项目的目标是了解(1)非均匀深部地壳区域的组合；(2)19亿年前变质作用的意义和原因；(3)从地球深处向深部地壳添加熔体的作用；(4)如何能够挖掘出大片深部地壳岩石；以及(5)这些岩石在北美西部更广泛的背景下的背景。这种综合的方法对地壳组装、稳定和折返过程中下地壳的特征、行为和演化施加了重要的一级约束。

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.