Paleomagnetism of the Rocks of Ascension Island

阿森松岛岩石的古地磁学

• 批准号: 0003411
• 负责人: Michael Valentine
• 金额: $ 8.23万
• 依托单位: University of Puget Sound
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-01 至 2004-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0003411&HistoricalAwards=false
• 关键词: Paleomagnetism; Rocks; Ascension; Island

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.

缺乏火山岩的古地磁数据阻碍了我们对地磁场的时间变化的理解，包括场反转，在过去的5 My。虽然近年来提出了一些日益复杂的地球发电机和逆转过程的模型，这些模型正在测试的领域变化的性质的知识非常有限。古地磁数据集的地理偏差是古地磁变化（PSV）、时均场（TAF）和反演模拟的最大问题之一。目前的大部分数据来自北方的站点，过去5百万年古地磁站点的更均匀分布对于提高我们的理解至关重要。PI对Ascension岛岩石的初步古地磁研究表明，Ascension岛有可能提供高质量的PSV、TAF和反转数据。这项研究将结合精确的40 Ar/39 Ar定年和矿物学分析，对Ascension岛岩石进行详细的古地磁研究，产生高质量的PSV和TAF数据。它也有可能揭示记录在Ascension岛火山流的逆转。此外，磁性矿物学工作，包括查明任何侵位后的矿物学变化，以及对岩石进行精确的放射性测年，肯定有助于更好地确定大西洋中脊侧翼这一热点岛屿的地质历史。该项目将显著涉及本科生，他们将参与令人兴奋的前沿研究。