Paleomagnetic study of the greenstone in the Mugi-Kamiaso area, Gifu Prefecture, central Japan.

要旨

We studied petrographically and paleomagnetically the greenstone exposed in the MugiKamiaso area, Gifu Prefecture, central Japan. This greenstone is unmetamorphosed generally but propylitized weakly, and is appropriate for paleomagnetic researches. Various tests with respect to the magnetic stability revealed that the greenstone preserves reliable records of magnetization acquired, probably, at the time of eruption. Paleomagnetic measurements provided reasonable ground to us for concluding that the greenstone is not an assemblage of randomly-oriented blocks which were emplaced as debris flows or grain flows. The greenstone occasionally occurs by accompanying Permian limestone, but both of them intervene stratigraphically between Mesozoic strata. It is highly probable that they have migrated as exotic sliding sheets from somewhere and have been accreted to the Mesozoic unit. Based on the regional geologic and sedimentologic information from this area, some discussions are directed toward the possible pre-emplacement setting of the greenstone.

主題