Effect of Low-Temperature Oxidation on the Remanence Properties of Titanomagnetites

Abstract

Changes in remanent magnetization and hysteresis parameters associated with low-temperature oxidation have been investigated using x=0.3, 0.5 and 0.7 synthetic titanomagnetite samples and natural submarine basalts. The intensity of remanence and the median destructive field (MDF) of TRM decreases with increasing oxidation. As oxidation proceeds, the intensity of CRM increases and its MDF decreases, except for x=0.7 titanomagnetite samples, which show maximum intensity and MDF around 0.6 of oxidation state (z). The intensity and stability of CRM become almost comparable to those of TRM in a high oxidation state. Saturation magnetization (J_s) decreases with increasing oxidation and in a fully oxidized state J_s is about 60% of initial values. The saturation remanence of titanomagnetite samples is almost constant until z-0.6 and tend to decrease as z increases further. The coercive force and coercivity of remanence decrease for x=0.3 and 0.5 samples monotonically with increasing z, whereas those for x=0.7 samples show maximum values for oxidation states of about 0.6. The correlation is not good between oxidation state z and the NRM intensity of submarine basalts, while the NRM becomes more stable with increasing low-temperature oxidation. Changes exhibited by DSDP samples against AF demagnetization show almost the same tendency for MDF of CRM for the x=0.7. However, other parameters are not always consistent with those of synthetic samples.