Singular solutions to Maxwell's equations and their significance for geomagnetic induction

Low-temperature oxidation of titanomagnetites (x=0.3, 0.5 and 0.7) was investigated in this study. Starting materials were carefully prepared so that their Curie points and lattice constants were in agreement with reliable values. Changes in Curie points and lattice constants during the process of low-temperature oxidation were then studied in detail. Independent heatings were performed under various conditions and oxidation parameters (z) were determined by chemical analyses. Though this method could not provide continuous z values like the weight increase method, reproducibility was very high when samples were heated in the same condition and the various states were consistent with each other. Oxidation states from z=0.0 to 1.0 were realized in three compositions. When titanomagnetite in basalt was heated under various conditions a change occurred, either oxidation, decomposition or reduction. Natural titanomagnetite minerals closely followed the oxidation-reduction trends established for synthetic samples. The present results are consistent with those of Readman & O'Reilly with some exceptions. The differences may have been caused by the differences in starting materials. The results of Keefer & Shive are similar to those of Ozima & Sakamoto and are completely different from ours. They detected a rhombohedral phase and indicated that the decomposition process proceeds in the same manner reported by Ozima & Sakamoto. We are unable to account for their results. It may be useful to consider the results of Ozima & Sakamoto as a decomposition process. This idea has not been presented previously in the literature.