SGER - Ash Flow Tuffs: a New Material for Reliable Paleointensities

SGER - 灰流凝灰岩：一种可靠古强度的新材料

• 批准号: 0521374
• 负责人: Jeffrey Gee
• 金额: $ 4.74万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-15 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0521374&HistoricalAwards=false
• 关键词: SGER; Ash; Flow; Tuffs; New

The PIs suggest that carefully selected samples from many ash flow tuffs (ignimbrites) should yield reliable estimates of the ancient field intensity. Preliminary data from the Bishop Tuff have yielded high qualitypaleointensity results with a high success ratio (75%). In addition, the well documented presenceof fine-grained cubic Fe-oxides spanning the superparamagnetic (SP) to single domain (SD) sizerange in silicic glasses from tuffs should be well suited for paleointensity determinations. Thesefine grained magnetic minerals in a glassy matrix may also be effectively armored during themultiple laboratory heatings necessary for a paleofield determination. Finally, ash flow tuffs aretypically well suited for high precision 40Ar/39Ar dating that can provide an accurate ageframework for any paleointensity results.This project is a pilot study of the Pleistocene Bishop Tuff aimed at evaluating the suitability of ashflow tuffs for absolute paleointensity studies. Because only portions of a particular ignimbrite will ultimately prove suitable for paleointensity work, a goal of the study will be to develop a strategy to identify the most likely materials for reliable paleointensities.The variability in magnetic mineralogy and cooling history in ash flows will also allow the testing ofseveral additional aspects of paleointensity determinations, including the effects of cooling rate,magnetic mineralogy and the influence of chemical remanence on paleointensity results. Theseare important controls on paleointensity in all recording media and so these tests will yieldvaluable information for interpreting other paleointensity results.The main goal of this proposal is to evaluate whether reliable paleointensitiescan be determined from ignimbrites. If absolute paleointensities can be determined from ash flows, it maybe possible to compile a much more comprehensive database of past field intensity fluctuationsof the geomagnetic field. All data generated during the present project will be archived in thepaleomagnetic data base (http://www.earthref.org/MAGIC/index.html) and the results will bepresented at international conferences and in published papers.

PI建议，从许多灰烬流凝灰岩（Ignimbrites）中精心选择的样品应得出古代田间强度的可靠估计。来自主教凝灰岩的初步数据产生了高质量的大压结果，其成功率很高（75％）。此外，横跨超par磁化（SP）的细颗粒的fe-氧化物的存在良好的存在与凝灰岩中硅质玻璃中的单个结构域（SD）serange的存在，应非常适合于测定镜头。在玻璃基体中，这些精细的磁性磁性矿物质也可以在它们的文化四重实验室暖气中有效地装甲，以进行古场测定。最后，烟灰流tuffs在型号上非常适合高精度40AR/39AR约会，可以为任何古显着结果提供准确的年龄框架。该项目是对更新世毕晓普tuff的试点研究，旨在评估Ashflow tuffs对绝对强度研究的适用性。因为只有特定的Ignimbrite的部分最终才能证明适合于古显微工作，所以该研究的目标是制定一种策略，以识别最可能的可靠质感材料。磁性矿物学和灰分流中的冷却历史的可变性还将允许对古质量测定的其他方面测试，包括对冷却速率的效果，包括对磁性矿物质的效果，对磁性矿物质的效果进行了重新效果。 TheSeare对所有记录介质的古显度的重要控件，因此这些测试将产生可解释其他古显着结果的信息。该提案的主要目标是评估是否可以从Ignimbrites确定可靠的Paperointensitiescan。如果可以从灰分流中确定绝对的古敏性，则可能可以编译出更全面的过去磁场强度波动的数据库。本项目期间生成的所有数据将归档在Paleomagnetic数据库（http://www.earthref.org/magic/index.html）中，结果将在国际会议上和发表的论文中提出。