An experimental approach to the study of Fe-Ti minerals originally contained in Paleozoic to Mesozoic red cherts from the Tamba, Mino and Shimanto terrains in Southwest Japan has been made. The main purpose of the study is to establish a foundation for the paleomagnetic reliability of cherts to support paleomagnetic results which were already reported by the author and his collaborators. (SHIBUYA and SASAJIMA, 1980; KATSURA et al., 1980). Thermomagnetic analyses combined with some heating experiments under an appropriate vacuum condition, lend an effective way to recover the original ferromagnetic mineral assemblage of these cherts. As the results, the possible ferromagnetic minerals (β phase) of the red cherts, which are found in stratigraphic sequences that contain greenstones, show an affinity with that of tholeiitic basalt (x=0.62±0.05), suggesting that the primary ferromagnetic minerals in the red cherts were probably derived from related submarine basaltic tuffs. If we accept a view that red cherts underwent submarine weathering or hydrothermal alteration almost the same time as the greenstones associated with them, a closed system with respect to Fe-Ti minerals and consequently blocking of their remanent magnetization as well, was maintained after an uncertain diagenetic event: this condition presumably related to the time of crystallization of major silica of the chert
