Age and Composition of the East Antarctic Shield by Isotopic Analysis of Granite and Glacial Till

知识价值：由于广泛的冰层覆盖和稀疏的遥感数据，前寒武纪东南极盾（EAS）的地质情况在很大程度上仍未被探索，信息仅限于非洲、印度和澳大利亚部分的沿海露头。南极东部岩石圈在全球具有重要意义：作为最大的前寒武纪相干盾构之一，其岩石年龄可达~3.8 Ga，在全球地壳生长中发挥了重要作用；它是罗迪尼亚和冈瓦纳超大陆组合的关键部分；它是地球的基底？S主要冰盖，包括许多冰下湖泊，并影响其热状态和机械稳定性；它与南非、印度和澳大利亚以前相邻的大陆地块的地质构造联系表明，它可能蕴藏着重要的矿产资源。本项目将通过对早古生代花岗岩类和更新世冰川碛体中锆石的U-Pb年龄和Hf- o同位素分析，增加对横贯南极山脉（TAM）下伏和邻近的EAS西部岩石圈年龄和组成的认识。早古生代罗斯造山带的TAM花岗岩代表了一个非常广泛的大陆边缘弧套件，可以提供关于它从何处熔化和/或穿过何处的直接信息。在穿越TAM的主要出口冰川顶部的冰川碛物中携带的火成岩和变质岩的大块岩石碎屑提供了近端EAS基底的侵蚀样本。这些材料中的锆石将提供年龄和继承（U-Pb）、地壳和地幔起源（O同位素）以及地壳来源和演化（Hf同位素）的数据。沿着TAM的重要部分整合，这些数据将有助于定义更广泛的地壳区域，这些区域可以与地球物理数据相关联，并用于测试地壳组合模型。更广泛的影响：该项目将为本科生和研究生提供一个研究机会。本科生将作为研究助理参与样品制备，成像和分析程序，并进行自己的独立研究。这个项目的两个主要元素将构成马里兰大学两名研究生硕士论文项目的基础。通过这个项目，他们将对岩石学、同位素地球化学和分析方法有很好的了解。这项工作的更广泛的科学影响是，它将有助于更好地了解南极东部岩石圈的起源和演化，这将对更广泛的地球科学和冰川学界有价值。此外，由于对过去的超级大陆有强烈的好奇心，公众对南极东部的地质知识一直很感兴趣，什么？以及全球变暖对冰盖稳定性的影响。

Intellectual Merit: Because of extensive ice cover and sparse remote-sensing data, the geology of the Precambrian East Antarctic Shield (EAS) remains largely unexplored with information limited to coastal outcrops from the African, Indian and Australian sectors. The East Antarctic lithosphere is globally important: as one of the largest coherent Precambrian shields, including rocks as old as ~3.8 Ga, it played an important role in global crustal growth; it is a key piece in assembly of the Rodinia and Gondwana supercontinents; it is the substrate to Earth?s major ice cap, including numerous sub-glacial lakes, and influences its thermal state and mechanical stability; and its geotectonic association with formerly adjacent continental blocks in South Africa, India and Australia suggest that it might harbor important mineral resources. This project will increase understanding of the age and composition of the western EAS lithosphere underlying and adjacent to the Transantarctic Mountains (TAM) using U-Pb ages, and Hf- and O-isotope analysis of zircon in early Paleozoic granitoids and Pleistocene glacial tills. TAM granites of the early Paleozoic Ross Orogen represent an areally extensive continental-margin arc suite that can provide direct information about the EAS crust from which it melted and/or through which it passed. Large rock clasts of igneous and metamorphic lithologies entrained in glacial tills at the head of major outlet glaciers traversing the TAM provide eroded samples of the proximal EAS basement. Zircons in these materials will provide data about age and inheritance (U-Pb), crustal vs. mantle origin (O isotopes), and crustal sources and evolution (Hf isotopes). Integrated along a significant part of the TAM, these data will help define broader crustal provinces that can be correlated with geophysical data and used to test models of crustal assembly. Broader impacts: This project will provide a research opportunity for undergraduate and graduate students. Undergraduates will be involved as Research Assistants in sample preparation, imaging, and analytical procedures, and conducting their own independent research. The two main elements of this project will form the basis of MS thesis projects for two graduate students at UMD. Through this project they will gain a good understanding of petrology, isotope geochemistry, and analytical methods. The broader scientific impacts of this work are that it will help develop a better understanding of the origin and evolution of East Antarctic lithosphere underlying and adjacent to the TAM, which will be of value to the broader earth science and glaciological community. Furthermore, knowledge of East Antarctic geology is of continuing interest to the general public because of strong curiosity about past supercontinents, what?s under the ice, and the impact of global warming on ice-sheet stability.