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

这一奖项由极地项目办公室提供，允许一名美国调查人员参与对东南极一套不同寻常的古代岩石进行的综合地球化学和同位素调查。该项目对东南极盾上的太古界纳皮尔杂岩进行了Lu-Hf和Re-Os同位素研究，使用了两次日本探险队在偏远地区收集的岩石样品。1996-97年和1998年在Riiser-Larsen和Tonagh岛。这些样本将被提供给日本科学家进行合作调查。美国和日本的工作必须同步推进。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，以及这些样品等分的SHRIMP锆石U-Pb年龄。该奖项支持的工作部分特别关注太古宙地壳和地幔演化，纳皮尔杂岩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系统可能会受到更年轻的变质和交代事件的严重干扰。此外，目前世界范围内太古代镁铁质-超镁铁质岩浆初始Os同位素组成的数据很少，这主要是由于结晶后蚀变事件和最近才克服的分析挑战。与卡内基研究所的Rick Carlson博士合作，我们将尝试利用纳皮尔杂岩超镁铁质和镁铁质岩石的新鲜度，并生成几个样品的Re-Os数据。除了提供一种测定缺乏锆石的岩石的方法，这种方法还将产生对理解地幔的Os同位素演化及其对地壳再循环的时间和性质、晚期球粒陨石薄片的积累以及可能随时间进行的核-地幔交换的关键数据。

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.