Constraining the Secular Compositional Evolution of the Upper Continental Crust Using Ancient Glacial Deposits and Creation of an Upper Crustal Reference Suite

在太阳系的行星中，地球是独一无二的，因为它拥有一层富含二氧化硅的低密度岩石，形成了我们的大陆。我们的物种正是在这个平台上进化的，它提供了维持我们社会所需的必要资源。了解大陆地壳的形成过程是地质学中的重大问题之一。关于大陆地壳起源的一个线索是它的平均成分。地壳的组成也是决定地壳形成后留在地幔中的产热元素数量的重要因素；这些元素提供了驱动板块构造所需的能量。在大陆地壳内，大部分生热要素集中在10公里以上。因此，确定上地壳的组成及其相关的不确定性，对于了解大陆地壳的形成和演化以及地球内部的能量平衡至关重要。该项目试图通过分析世界各地的冰川沉积沉积来深入了解大陆上地壳的组成。这些沉积物的年代从2.9到0.3Ga，并提供了对地球上地壳平均成分如何随时间变化的洞察。反过来，这种变化的成分可以用来推断形成地壳的过程，以及地球表面普遍存在的变化条件。将对细粒碎屑岩基质进行分析，以获得一套全面的常量元素、微量元素和同位素组成。将评估风化和大气成分变化对地壳成分的影响。这些样品将构成上地壳参考套装的基础，该套参考套装将向社区提供，以便随着时间的推移进一步描述上大陆地壳的特征。

The Earth is unique amongst the planets of our Solar System in having a crust of silica-rich, low-density rock that forms our continents. It is upon this platform that our species evolved and it provides the essential resources needed to maintain our society. Understanding the processes by which the continental crust formed is one of the grand questions in geology. A clue to the origin of continental crust is its average composition. The crust's composition also factors prominently in determining the amount of heat producing elements that remained in the Earth's mantle after formation of the crust; these elements provide the energy needed to drive plate tectonics. Within the continental crust, most of the heat-producing elements are concentrated in the upper 10 km. Hence, determining the composition of the upper crust, and associated uncertainties, is crucial in understanding continental crust formation and evolution, as well as the energy balance of the Earth's interior.This project seeks insights into the composition of the upper continental crust through analysis of glacial sedimentary deposits from around the world. These deposits date from 2.9 to 0.3 Ga and provide insight into how the average composition of the Earth's upper crust has changed with time. The changing composition can, in turn, be used to infer the processes that formed the crust, as well as the changing conditions prevalent at the Earth's surface. The fine-grained matrix of the tillites will be analyzed for a comprehensive suite of major and trace elements and isotopic compositions. The effects of weathering and of changes in atmospheric composition on crustal composition will be assessed. These samples will form the basis of an upper crustal reference suite that will be made available to the community for further characterization of the upper continental crust through time.