SGER-Lu-Hf and Re-Os Systematics of the Earliest Crust in Antarctica: The Napier Complex of Enderby Land

该奖项由极地项目办公室提供，允许一名美国研究人员参与对东南极洲一组不寻常的古代岩石的综合地球化学和同位素调查。该项目需要使用1996-97年和1998年两次日本探险队在里瑟-拉森山和托纳岛偏远地区收集的岩石样本，对南极东部盾上的太古代纳皮尔杂岩进行Lu-Hf和Re-Os同位素研究。这些样本将用于与日本科学家的合作调查。美国和日本的工作必须同时进行。日本研究小组的重点是岩石和矿物的主要氧化物组成，Nd、Sr和Pb同位素组成，以及SHRIMP锆石U-Pb定年法对这些样品的等分物进行测定。该奖项支持的工作主要集中在太古代地壳和地幔的演化上，纳皮尔复合体可能拥有地球上保存最完好的一些岩石。该项目将使用Lu-Hf和Re-Os方法，因为越来越多的人认识到Sm-Nd系统可能受到年轻变质和交代事件的严重干扰。此外，目前世界范围内太古宙基性-超基性岩浆初始Os同位素组成的数据数量很少，这主要是由于结晶后蚀变事件和最近才克服的分析挑战。与卡耐基研究所的里克·卡尔森博士合作，我们将尝试利用纳皮尔复合体超镁铁和基性岩石的新鲜度，并在几个样品上生成Re-Os数据。除了提供一种对缺乏锆石的岩石定年的方法外，这种方法还将获得对理解地幔的Os同位素演化至关重要的数据，其含义包括地壳再循环的时间和性质、晚球粒质单板的增生以及随着时间的推移可能的核幔交换。

This award, provided by the Office of Polar Programs, allows a US investigator to participate in integrated geochemical and isotopic investigations of an unusual suite of ancient rocks from East Antarctica. This project entails a Lu-Hf and Re-Os isotopic study of the Archean Napier Complex on the East Antarctic Shield using rock samples collected by two Japanese expeditions to the remote regions of Mt. Riiser-Larsen and Tonagh Island in 1996-97 and 1998. These samples are being made available for a collaborative investigation with Japanese scientists. It is imperative that the work in the US and Japan move ahead simultaneously. The Japanese team is focusing on rock and mineral major oxide compositions, Nd, Sr and Pb isotopic compositions, as well as SHRIMP zircon U-Pb dating on aliquots of these samples. The component of the work supported by this award focuses specifically on Archean crustal and mantle evolution for which the Napier Complex has, potentially, some of the best-preserved rocks on Earth. This project will use the Lu-Hf and Re-Os approach because of increasing recognition that the Sm-Nd system can be perturbed severely by younger metamorphic and metasomatic events. Furthermore, presently the number of data for initial Os isotopic compositions of Archean mafic-ultramafic magmas worldwide is very small, largely because of post-crystallization alteration events and the analytical challenges that have only recently been overcome. In collaboration with Dr. Rick Carlson at the Carnegie Institution, we will attempt to exploit the freshness of Napier Complex ultramafic and mafic rocks and generate Re-Os data on several samples. In addition to providing a means of dating rocks that lack zircon, this approach will yield data critical to the understanding of Os isotopic evolution of the mantle with its implications for the timing and nature of crustal recycling, accretion of a late chondritic veneer and possibly core-mantle exchange through time.