Suitability of volcanic glasses with different compositions and evolution histories to gain paleointensity data

高质量的古强度数据对许多地球科学问题至关重要，例如长期持续的磁静区（所谓的超年代）或考古文物的年代测定期间的磁场状态。然而，获得它们是非常耗时的，并且实验的成功率很低。有人建议，使用理想的材料，如火山玻璃，可以提高强度数据的质量和数量，但有关剩磁载体，剩磁的起源，成分的影响，冷却速度，水化和失透的问题尚未得到完全回答。在这里，我们建议联合收割机的合成玻璃（已知的历史：组成，氧逸度，磁场）的研究与不同组成的天然玻璃的研究。虽然合成玻璃将有助于回答有关剩磁载体和剩磁起源的问题，但该项目的第二部分是关于差异化火山玻璃，即。e.来自不同地质环境（如大洋中脊、大陆碰撞区）、具有不同演化历史（如气生、冰下、水化、珍珠岩化、变晶化）和不同成分（如流纹岩、响岩）的黑曜石将有助于了解这些不同环境的影响。所需的黑曜石样品要么已经有了（从早些时候到亚美尼亚和冰岛的实地考察中得到的），要么将在冰岛的实地考察中得到。此外，还将调查海底和冰下起源的玄武岩玻璃，以检查老化效应。我们将采取岩石磁学、古磁学和火山学相结合的方法来分析各种样品：将确定剩磁载体和磁性、古方向和古强度、玻璃化转变温度、自然冷却速率和挥发物含量。来自实验的额外信息将使我们能够校正古强度数据的影响，如冷却速率依赖性或水合作用。古地磁数据将包括在古和/或古地磁数据库和我们获得的知识的意义不同的演化历史的玻璃将被用来开发一个目录的paleointensity样本的适用性标准，如果有必要提出适应到目前为止使用的paleointensity方法。

High quality paleointensity data is essential to many geoscientific problems like the state of the magnetic field during long lasting magnetic quiet zones (so-called superchrons) or dating of archeological artefacts. However, obtaining them is very time-consuming and success rates of the experiments are low. It has been suggested that usage of ideal materials like volcanic glass can improve both quality and quantity of intensity data, but questions regarding the remanence carriers, the origin of the remanence, the influence of composition, cooling rate, hydration and devitrification are yet to be answered completely. Here we propose to combine a study on synthesized glasses (with known history: composition, oxygen fugacity, magnetic field) with a study on natural glasses of different compositions. While the synthetic glasses will help to answer questions regarding the remanence carriers and the origin of the remanence, the second part of the project on differentiated volcanic glasses, i. e. obsidians, from different geological settings (e.g. mid ocean ridge, continental collision zone), with varying evolution histories (e.g. aerial, subglacial; hydration, perlitization, devitirfication) and diverse compositions (e.g. rhyolite, phonolite) will help to understand the influences of these different circumstances. The required obsidian samples are either already available (from earlier field trips to Armenia and Iceland) or will be taken on a field trip to Iceland. Additionally basaltic glasses of both submarine and subglacial origin will be investigated to also check for ageing effects. We will take a combined rock magnetic, paleomagnetic and volcanological approach to analyze the various samples: Remanence carriers and magnetic properties, paleodirections and -intensities, glass transition temperatures, natural cooling rates and volatile contents will be determined. The additional information from experiments will enable us to correct the paleointensity data for influences like cooling rate dependency or hydration effects. The paleomagnetic data will be included in paleo- and/or archeomagnetic data bases and our gained knowledge about the significance of different evolution histories of the glasses will be used to develop a catalogue of suitability criteria for paleointensity samples and if necessary to propose adaptations to the so far used paleointensity methods.