偏极性现象研究及其地球动力学意义

对于１０８年或更长的地史时期而言，地磁场表现出偏极性特征。统计表明，偏极性变化与磁极倒转频率、长期变、古强度变化等古地磁现象以及地球自转速率变化、真极移和海底扩张等地球动力学现象均有不同程度的相关关系。偏极性呈现周期性变化，其中６４０～５３３Ｍａ的周期对应于王鸿祯等（１９９７）所提出的联合古陆周期。笔者认为，Ｍａｒｕｙａｍａ（１９９４）的地幔羽模型可能有助于说明岩石圈板块通过全地幔对流的方式介入核幔边界条件，进而影响或控制了偏极性的长周期变化。

GEOMAGNETIC POLARITY BIAS AND ITS GEODYNAMICS SIGNIFICANCE

In the time scale of 10 8 years or longer, the geomagnetic field is characterised by polarity bias. Variation of the polarity bias statistically correlate with the phenomena of paleomagnetism, such as frequency of reversals, paleosecular variation and paleointensity variation, and the phenomena of geodynamics, such as rate variation of Earth rotation, true polar wandering and sea floor spreading. The periodicity of polarity bias variation of 640～533Ma is also consistent with the Pangea cycle proposed by Wang, et al.(1997). It is suggested that the whole mantle convection model by Maruyama(1994) is hopeful to interpret the above mentioned relations, his“cold sinking superplume”can make the influence both on the core mantle boundary and on the continental plates.