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

通过花岗岩和冰碛同位素分析确定东南极地盾的年龄和成分

• 批准号: 0944645
• 负责人: John Goodge
• 金额: $ 45.54万
• 依托单位: University of Minnesota Duluth
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-15 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0944645&HistoricalAwards=false
• 关键词: Age; Composition; East; Antarctic; Shield

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.

智力优势：由于冰层覆盖广泛，遥感数据稀少，前寒武纪东南极地盾（EAS）的地质基本上尚未探索，信息仅限于非洲，印度和澳大利亚部分的沿海露头。东南极岩石圈具有重要的全球意义：作为前寒武纪最大的连贯性地盾之一，包括年龄约为3.8 Ga的岩石，它在全球地壳生长中发挥了重要作用;它是Rodinia和Gondwana超大陆组装的关键部分;它是地球的基底。它的主要冰帽，包括许多冰下湖泊，并影响其热状态和机械稳定性;其与南非，印度和澳大利亚以前相邻的大陆块的大地构造关系表明，它可能蕴藏着重要的矿产资源。本项目将利用U-Pb年龄、早古生代花岗岩类和更新世冰碛物中锆石的Hf-和O-同位素分析，加深对横贯南极山脉（TAM）下和邻近的西部EAS岩石圈的年龄和组成的了解。TAM花岗岩的早古生代罗斯造山带代表了一个面积广泛的大陆边缘弧套件，可以提供直接的信息EAS地壳从它熔化和/或通过它通过。在穿越TAM的主要出口冰川头部的冰碛中夹带的火成岩和变质岩性的大岩石碎屑提供了近端EAS基底的侵蚀样品。这些材料中的锆石将提供有关年龄和遗传（U-Pb）、地壳与地幔起源（O同位素）以及地壳来源和演化（Hf同位素）的数据。这些数据沿着TAM的重要部分，将有助于确定更广泛的地壳区，这些地壳区可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形成两个研究生在UMD的MS论文项目的基础。通过这个项目，他们将获得岩石学，同位素地球化学和分析方法的良好理解。这项工作的更广泛的科学影响是，它将有助于更好地了解东南极岩石圈的起源和演变的底层和邻近的TAM，这将是更广泛的地球科学和冰川学界的价值。此外，公众对东南极洲地质学的知识一直很感兴趣，因为他们对过去的超级大陆有着强烈的好奇心。冰下的温度，以及全球变暖对冰盖稳定性的影响。