山陰帯および飛騨帯花崗岩類中の角閃石に見られる累帯構造について : 鉛山グラノファイア類・奥津花崗閃緑岩体・船津複合岩体を例に(<特集II.>角閃石研究の現状と課題-地団研第37回総会造岩鉱物シンポジウム-)

概要

論文の詳細を見る
Chemical variations of amphiboles with the crystallization have been clarified for some calc-alkaline plutonic rocks in the Innerside of Southwest Japan. The chemical compositions of amphiboles from the Namariyama granophyres in the eastern San'in district, show wide range from ferroan pargasite to actinolite. In the progress of the crystallization of amphiboles, Si increases and Al, Ti, Na and K decrease. This tendency can be explained by lowering of the temperature and increase of the silica activity in the liquid with the crystallization. On the other hand, mg-value decreases in the early stage and increases in the later stage during the crystallization of the Namariyama granophyres. This fact indicates that the oxygen partial pressure has increased in the later stage of the crystallization. Amphiboles from the Okutsu granodioritic mass in the eastern San'in district are mainly magnesio hornblende with subordinate ferro hornblende. They have a zonal structure, decreasing the mg-value from the core to the rim. However, the zoning pattern can be classified into two types with respect to the variations of the Si and Al contents. The amphiboles of A-type increase in Si and decrease in Al and those of B-type increase in Al and decrease in Si from core to rim. From detailed description of the mode of occurrence of the amphiboles, genetic process of. these two types of zoning have been clarified. That is, A-type amphibole, has been primarily preceded by the formation of Al-rich amphibole, while B-type amphibole by the formation of the primary clinopyroxene. Amphiboles from the Funatsu granitic complex in the Hida belt are mainly magnesio hornblende. They have a zonal structure showing the increase in Si and the decrease in mg-yalue, Al, Ti, Na and K from core to rim. Furthermore, in the later stage of crystallization, some amphiboles are replaced by the Si-rich amphibole which appears to have been formed by reaction between amphibole and acidic liquid. As mentioned above, generally, amphiboles in these plutons increases in Si and decreases in mg-value, Al, Ti, Na and K with crystallization, except for a part of them in the Namariyama granophyres and the Okutsu granodioritic mass. This trend is different from a zonal structure reported from the San'yo and Kitakami zone in which amphiboles increase in Al, Ti, Na and K and decrease in Si and mg-value with crystallization. Such differences of zoning patterns may be ascribed to which dominantly appears in the early stage of the crystallization, amphibole or clinopyroxene.
1984-09-25

山陰帯および飛騨帯花崗岩類中の角閃石に見られる累帯構造について : 鉛山グラノファイア類・奥津花崗閃緑岩体・船津複合岩体を例に(<特集II.>角閃石研究の現状と課題-地団研第37回総会造岩鉱物シンポジウム-)

スポンサーリンク

概要

著者

関連論文

スポンサーリンク