中国东部白垩纪以来火山岩记录的地磁场古强度可靠性及演化模式研究

地磁场古强度(GPI)蕴含丰富的地球内部动力学过程信息。目前GPI研究的核心问题是GPI数据的可靠性。GPI测量涉及多次加热，造成过程中矿物的生成与转化，对实验结果造成重大影响。新的研究表明，即使是目前所用的常规pTRM检测技术也不能完全剔除矿物热转化的影响。这暗示着已经发表的数据中可能存在着大量的不确定性，阻碍了应用GPI数据探讨地球内部演化过程。解决这一问题的突破点就是研究最近喷发的历史熔岩流。这些熔岩流具有已知的地磁场强度值，因此，可以直接有效地检验各种实验方法。为此，本项目首先计划研究近期喷发的熔岩流，尤其系统研究那些能够通过pTRM检测，却不能准确记录GPI样品的磁学性质和基质成分，建立鉴别这些样品的岩石磁学标准。在此基础上，进一步研究中国东部分布的白垩纪以来喷发的熔岩流，构建这一时期GPI的变化模式，探讨白垩纪以来GPI特征及相应的地球内部动力学信息，全面推动这一领域的发展。

The Earth’s geomagnetic paleointensity (GPI) bears great information on the dynamic processes in the Earth’s interior. Although many GPI data have been obtained, great uncertainties still exist on its fidelity. The theory of GPI is rather simple (thermal remanence magnetization, TRM), but the experimental processes involve in many steps of thermal treatments which results in possible mineral transformation and neoformation. In addition, the domain states also greatly bias the GPI results. To check the effects of thermal treatments, partial TRM (pTRM) checking has been designed. However, recent studies showed that the pTRM checking cannot fully avoid the thermal effects. For example, if the unblocking temperatures of the newly-formed magnetic minerals are higher than the treatment temperature, the pTRM checking fails. To resolve these problems, we need to investigate the historic lava flows with known GPI values. This will easily facilitate the tests of all related experiments. Therefore, first, this project aims to systematically investigate the historic lavas and set up criteria for excluding these samples with biased GPI values. Then, we will systematically investigate the lava flows since the Cretaceous in the Eastern China and the corresponding geodynamic processes in the Earth interior.