CAREER: Evolution of the Southern African Plateau Using Advances in (U-Th)/He Thermochronometry, and Enhancing Student Critical Thinking in Science

南部非洲高原是大陆高原的一个独特而特别有趣的例子，大陆高原是大陆的一个大的高内陆地区。高原海拔升高的原因，无论是南部非洲高原还是整个大陆的高原，都没有得到很好的理解。在这个项目中，磷灰石(U-Th)/He和4He/3He热时计的最新进展被用于研究南部非洲高原的侵蚀历史。这些方法解决了岩石在地壳上层几公里处移动时的冷却历史，并使我们能够深入了解地球表面的剥蚀和地形演变。侵蚀或剥蚀是由水、风或冰等移动介质在地球表面运输岩石材料的过程。我们对南部非洲高原侵蚀史的认识存在两大空白：高架高原本身的剥蚀史知之甚少，以及65 Ma以后高原和沿海被动边缘的剥蚀史尚不清楚。没有公布南非任何地点的磷灰石(U-Th)/He数据。研究策略是专门设计的，以利用新的方法进步，扩大磷灰石(U-Th)/He和4He/3He技术的应用。四个研究问题激发并将在本研究中解决：1)南部非洲高原高架内部的侵蚀历史是什么，以及它对高原高程增益的影响是什么？2)是否存在空间上的剥蚀异质性，模拟了岩浆活动的空间波及、金刚石管道的就位和整个区域的区域加热？3)区域侵蚀是否应归因于高原内部水系的演变？4) 65 Ma之后是否有一个加速侵蚀的阶段，可以归因于高原表面隆起的阶段？目前正在进行一项全面的教育工作。项目人员正在与非洲地球观测网合作，在南非开办一个关于(U-Th)/He热时计的短期课程，作为非洲地球观测网全非洲网络计划的一部分。在非洲任何地方都没有(U-Th)/He设施。与非洲地球观测网络有关的一名非洲学生将参与该项目，并前往美国获得尖端分析方法的实践经验。首席研究员还参与了科罗拉多大学的科学教育计划，通过开发、实施和评估模块化方法来教授地球科学中的批判性思维。拟议的南非项目的研究动机将发展成为这些模块之一。新教材的有效性将在模块和课程层面进行评估，由科罗拉多州科学教育倡议的科学教学研究员提供帮助。该项目由美国国家科学基金会国际科学与工程办公室的地球科学部的构造、教育和人力资源项目以及非洲、近东和南亚项目支持。

The southern African Plateau is a unique and particularly intriguing example of a continental plateau, a large elevated interior region of a continent. The causes of plateau elevation gain, both of the southern African plateau and of continental plateaus generally, are not well understood. In this project, recent advances in apatite (U-Th)/He and 4He/3He thermochronometry are used to investigate the erosional history of the southern African plateau. These methods resolve the cooling history of rocks as they move through the upper few kilometers of the Earth's crust, and allow insight into denudation and topographic evolution at the Earth's surface. Erosion, or denudation, is the transport of rock materials at the Earth's surface by a mobile agent, such as water, wind or ice.There are two major gaps in our knowledge of the erosional history of the southern African Plateau: the denudation history of the elevated plateau itself is poorly constrained, and the post-65 Ma denudation history of both plateau and coastal passive margins is not well known. No apatite (U-Th)/He data has been published for any location in South Africa. The research strategy is specifically designed to capitalize on new methodological advances that broaden the utility of the apatite (U-Th)/He and 4He/3He techniques. Four research questions motivate and will be addressed by the present study: 1) What is the erosional history of the elevated interior of the southern African plateau, and what are its implications for elevation gain of the plateau? 2) Is there a spatial heterogeneity of denudation that mimics the spatial sweep of magmatism, diamondiferous pipe emplacement, and regional heating across the region? 3) Is regional erosion instead attributable to the evolution of river systems in the plateau interior? 4) Is there a phase of accelerated erosion after 65 Ma that could be attributable to a phase of plateau surface uplift?A comprehensive education component is being carried out. Project personnel are collaborating with the African Earth Observatory Network to run a short course on (U-Th)/He thermochronometry in South Africa as part of African Earth Observatory Network's Africa-wide network plans. There is no (U-Th)/He facility anywhere in Africa. An African student associated with African Earth Observatory Network will be involved in the project and travel to the U.S. to gain hands-on experience with cutting-edge analytical methods. The principal investigator is also participating in the University of Colorado's Science Education Initiative through development, implementation, and evaluation of a modular approach to teaching critical thinking in Earth Science. The research motivations for the proposed South African project will be developed into one of these modules. The effectiveness of the new materials will be assessed at the module and course level with help from a Science Teaching Fellow affiliated with the Colorado's Science Education Initiative.This project is supported by the Tectonics and Education and Human Resources Programs in the Earth Sciences Division and the Africa, Near East & South Asia Program in NSF's Office of International Science and Engineering.