Paleomagnetism of the Rocks of Ascension Island

来自火山岩的古地磁数据的缺乏阻碍了我们对过去5000年来地磁场时间变化的理解，包括磁场逆转。虽然近年来提出了一些日益复杂的地球动力学和逆转过程模型，但这些模型是在对磁场变化性质的认识严重有限的情况下进行检验的。古地磁资料的地理偏差是古地磁资料长期变化（PSV）、时均场（TAF）和反演建模中存在的最大问题之一。目前的大部分数据来自北半球的站点，而过去5万年古地磁站点的更均匀分布对提高我们的理解至关重要。PI对阿森松岛岩石进行的初步古地磁研究表明，阿森松岛具有提供优质PSV、TAF和反转资料的潜力。本研究将对阿森松岛岩石进行详细的古地磁研究，并结合精确的40Ar/39Ar定年和矿物学分析，产生高质量的PSV和TAF数据。它也有可能揭示阿森松岛火山流记录的逆转。此外，磁矿物学工作，包括确定任何就位后的矿物学变化，以及精确的岩石放射性测年，肯定有助于更好地定义这个位于大西洋中脊侧翼的热点岛屿的地质历史。该项目将主要涉及本科生，他们将参与令人兴奋的前沿研究。

Valentine EAR-0003411 A dearth of paleomagnetic data from volcanic rocks hampers our understanding of temporal variations of the geomagnetic field, including field reversals, during the last 5 My. Although a number of increasingly sophisticated models for the geodynamo and the reversal process have been proposed in recent years, such models are being tested with a severely limited knowledge of the nature of field variation. One of the greatest problems with regard to paleosecular variation (PSV), time-averaged field (TAF), and reversal modeling is a geographical bias in the paleomagnetic data set. Most of the current data come from sites in the northern hemisphere, and a more uniform distribution of paleomagnetic sites for the last 5 My is critical to improving our understanding. Preliminary paleomagnetic study of Ascension Island rocks by the PI has shown that Ascension Island has the potential to provide quality PSV, TAF, and reversal data. This study will perform a detailed paleomagnetic study of Ascension Island rocks in conjunction with precision 40Ar/39Ar dating and mineralogical analyses, producing high-quality PSV and TAF data. It also has the potential to reveal reversals recorded in the volcanic flows of Ascension Island. In addition, magnetic mineralogy work, including identification of any post-emplacement alteration of mineralogy, and precision radiometric dating of the rocks will certainly help to better define the geologic history of this hot spot island on the flank of the Mid-Atlantic Ridge. The project will significantly involve undergraduate students, who will participate in exciting, cutting-edge of research.