On the Orikabe granitic body, Kitakami mountainland

• Published in: Ganseki kōbutsu kōshō gakkaishi Vol. 65; no. 4; pp. 149 - 161
• Main Authors: Ishijima, Masami, Kato, Yuzo
• Format: Journal Article
• Language: English
• Published: Japan Association of Mineralogical Sciences 1971
• ISSN: 0021-4825; 1883-0765
• DOI: 10.2465/ganko1941.65.149

The Orikabe granitic body, Kitakami mountainland, intruded in middle-upper Cretaceous, is studied petrographically. From field and microscopic observations, this body is divided into three rock types of Sasamori, Orikabe and Tokusenjo. The Sasamori type is the most leucocratic of the three and contains no pyroxenes. The Orikabe type rocks carry pyroxenes always rimmed by amphibole (hornblende with or without cummingtonite) and a small amount of biotite. The Tokusenjo type is melanocratic and contains among the three types the largest amount of pyroxenes with or without a hornblende mantle. The results of fourty modal analyses and seven chemical analyses are given in Tables 1 and 2, respectively. Petrochemically, the Sasamori type is lower in K2O and higher in SiO2 than the Orikabe type, corresponding with the evidence that the Qz/Kf ratio of the former is higher than the latter (Figs. 2, 4 and 7). Comparing with the other granitic bodies in the Kitakami mountainland the Orikabe granitic body is petrographically similar to the Tabashine granitic body.