飛騨変成帯の原岩構成とその地球化学的検討

概要

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The Hida metamorphic gneisses can be divided into sixth groups on the basis of mineral assemblages; Type I, Calcite+Cpx±Olivine±Dolomite (Calc-silicate gneiss); Type II, Cpx+Scapolite±Plagioclase±Calcite; Type III, Cpx+Plagioclase; Type IV, Cpx+Garnet+Plagloclase (the foregoing Cpx-gneisses); Type V, Hornblende+Plagioclase±Cpx+Biotite (Hornblende gneiss); Type VI, Biotite+Garnet+Plagioclase±Sillimanite (Biotite gneiss). Gneiss of each types is alternated layer by layer and called banded gneiss. From the characteristic of chemical compositions which are changed gradually from calc-silicate gneiss to biotite gneiss and their occurence in the field, their variety can be explained by the mixing of their protolith during sedimentation. The protolithes of biotite gneisses are infered to be graywacke from their major chemical compositions. Although the REE patterns of biotite gneisses are slightly different among them, there is a systematic variation in them. It can be considered that the rocks which REE patterns are resemble to alkaline rock and calc-alkaline rock were distributed at their prvonance and the detritals derived from there were mixed during the sedimenation.
1993-04-30