热剩磁偏离古地磁场的校正及其应用

THE CORRECTION OF TRM DEVIATION INDUCED BY AMS AND ITS APPLICATION

根据含多畴磁铁矿岩石的热剩磁(TRM)及其磁化率各向异性(AMS)张量间的特征值的比值关系,推导出一种因AMS 而引起的TRM 方向偏离外磁场方向的具体校正公式,并将其成功地应用到中国月山闪长岩体及法国Flamanville 花岗岩体的古地磁研究中.

Based on that the order of magnitude of the anisotropy eigenvalue ratios of thermal remanentmagnetization(TRM)is expected to be the square of the principal susceptibility ratios in anisotropicmultidomain magnetite assemblages(Conge,1987),a concrete correction foumula is derived in this paper,which can be used to correct the TRM deviation induced by the anisotropy of magnetic susceptibility(AMS)away from the ambient field,and successfully applied to the practical paleomagnetic researches inYueshan diorite(china)and Flamanville granite(France).An interesting discovery is that TRM directionis deflected away from that of the paleoficld in each site.In contrast,the overall mean TRM direction isquite a good estimation of the paleofield direction,because the longest axis of susceptibility ellipsoid are inthe radial distribution.