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

利用古冰川沉积物约束上陆壳的长期成分演化并创建上地壳参考套件

• 批准号: 1321954
• 负责人: Roberta Rudnick
• 金额: $ 22.6万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2015-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1321954&HistoricalAwards=false
• 关键词: Constraining; Secular; Compositional; Evolution; Upper

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.

地球在太阳系的行星中是独一无二的，它有一个富含二氧化硅的低密度岩石的地壳，形成了我们的大陆。 正是在这个平台上，我们的物种进化了，它提供了维持我们社会所需的基本资源。了解大陆地壳的形成过程是地质学的重大问题之一。 大陆地壳起源的一个线索是其平均成分。 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，大多数产热元素集中在上10公里。 因此，确定上地壳的组成及其不确定性，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。本项目通过分析世界各地的冰川沉积物，探索上大陆地壳的组成。 这些沉积物的年代从2.9到0.3 Ga，并提供了地球上地壳的平均成分如何随时间变化的见解。 反过来，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。 细粒度的基质的冰碛岩将进行分析的一套全面的主要和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。 这些样本将构成上地壳参考套件的基础，供社区进一步确定上大陆地壳的时间特征。