中部地方上松町西方の小川花こうせん緑岩体について Ｉ

Abstract

Ogawa Granodiorite Mass, one of the late Cretaceous granite, can be classified into the following three rock facies: (a) medium-grained facies, (b) porphyritic facies, (c) finegrained facies. According to the mode of occurrence and microscopic observations, these three rock facies are considered to be formed in situ through the crystallization differentiation process, after the intrusive movement of Ogawa Mass. Zoning patterns of plagioclases consisting the above-stated rock facies are investigated, and the following results were obtained. In the case of Ogawa Granodiorite Mass, zoning structures of plagioclases are correlative among the most crystals of the three rock facies. The type of zoning pattern of plagioclases of Ogawa Mass is distinguishable as follows from inner part to the outward. -inner patchy zone-inner oscillatory zone-outer patchy zone-outer oscillatory zone-rim. From the comparison of zoning structures of plagioclases in above three rock facies, the present author concluded that the outer oscillatory zone might have been formed after/or the same time of crystallization differentiation.