長野県新野地域の領家花崗岩類(その2)

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The writer has carried out the geological and petrochemical researches on granites in the Niino district, Nagano prefecture, in the Ryoke metarmorphic belt of Central Japan. Granites are classified into four types and the succession of their emplacement is as follows from the older one; the Karnihara granite, the Kadoshima granite, the Tenryukyo granite and the Habakawa granite. Of these four types, the Kadoshima, the Tenryukyo and the Habakawa granites are assumed to be correlated to the Busetsu, the Sumikawa and the Mitsuhashi granites in the Dando district studied by KOIDE (1958), respectively. It is not clear whether the Kamihara granite is correlated to the Kiyosaki granodiorite or not, anyhow their petrographic and chemical natures are different each other. The geological evidences in field and the plagioclase twin laws after GORAI (1950; 1951) suggest that the generation of these granites is not related with granitization in situ, but related with magma. The normative proportions of albite, orthclase and quartz of the granites are compared with the experimental data of the system, KAlSi_3O_8-NaAlSi_3_8-SiO_2-H_2O by TUTTLE and BOWEN (1958) and LUTH et al. (1964). The compositions of the Kamihara and the Tenryukyo granites gradually approach to the thermal valley of this system with increase of SiO_2 wt. % in the chemical composition. Particularly, the latter is closely related with the thermal valley. The normative compositions of the Kadoshima and the Habakawa granites are hardly related to the thermal valley, and plotted to more siliceous side. These granites are rich in calcium to alkali components, and it is conceivable that the calcium content in granite magma influences upon the chemical composition of the lowest melting liquid. The trend of the granites in the above system suggests that these granite magmas do not originate from melting of Ryoke metamorphic rocks at least.
地学団体研究会の論文
1968-11-25

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加々美寛雄
東京支部

長野県新野地域の領家花崗岩類(その2)

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