Reconstructing the full vector paleomagnetic field information from dated volcanic glass and correcting for cooling rate effects

从过时的火山玻璃重建全矢量古磁场信息并校正冷却速率影响

• 批准号: 34240892
• 负责人: Dr. Roman Leonhardt
• 金额: --
• 依托单位: Zentralanstalt für Meteorologie und Geodynamik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2008-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/34240892?language=en
• 关键词: Reconstructing; full; vector; paleomagnetic; field

Reliable paleomagnetic data, giving information about both direction and intensity of the Earth’s magnetic field, is crucial to understand the evolution of this field throughout the geological past. It is suggested that volcanic glass is an ideal material for such paleomagnetic records, because all biasing effects which are usually hard or impossible to detect in other recording media, are either absent or can be corrected for by using mineralogical and rock magnetic constraints. Volcanic glass is often pristine and contains a magnetic fraction in the single domain range. In collaboration with volcanologists the structural properties of volcanic glass, particularly the glass transition and the natural cooling rate across this transition are investigated by relaxation geospeedometry. Determination of cooling rate dependency of the thermoremanence allows for an extrapolation to natural cooling rates and, thus, a correction of absolute paleointensity determinations conducted on laboratory time scales. It is proposed to investigate a collection of glass yielding different age, composition, facies and quenching environment. In dependency of these conditions, the ideal character of volcanic glass regarding paleomagnetic research will be verified. The obtained paleomagnetic records will be used to reconstruct the past global geomagnetic field evolution and to improve analyzes techniques, in particular, paleointensity determination.

可靠的古地磁数据提供了有关地球磁场方向和强度的信息，对于了解整个地质历史中地球磁场的演变至关重要。火山玻璃是这种古地磁记录的理想材料，因为在其他记录介质中通常很难或不可能检测到的所有偏倚效应，要么不存在，要么可以通过矿物学和岩石磁约束来纠正。火山玻璃通常是原始的，在单畴范围内含有磁性成分。在与火山学家的合作下，利用弛豫地质速度测量法研究了火山玻璃的结构特性，特别是玻璃转变和在这一转变过程中的自然冷却速率。测定温度对冷却速率的依赖性，可以外推自然冷却速率，从而对在实验室时间尺度上进行的绝对古强度测定进行校正。提出了一组不同年龄、成分、相和淬火环境的玻璃。在此基础上，验证了火山玻璃在古地磁研究中的理想特性。获得的古地磁记录将用于重建过去的全球地磁场演变，并改进分析技术，特别是古强度测定。