奥秩父荒川小屋附近の石英閃緑岩の接触変成作用 : とくに火成岩様組織をもつホルンフェルスの形成について

概要

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Small masses of quartz-dioritic stock are distributed in the upstream area of the Arakawa River in Saitama Prefecture. These rocks intrude into the Mesozoic strata which are composed mainly of slate and sandstone. In this paper, the contact phenomena of one of the quartzdiorites are describcd and discussed, with special reference to the formation of pyroxene-hornefels with igneous texture. From the results of the field and laboratry investigations, the following conclusions are obtained: 1) The contact metamorphosed rocks can be subdivided into the biotite hornfels, the biotitecordierite-potash feldsper hornfels, and the biotite-hypersthene hornfels zones, from the outer to the inner aureoles. The characteristics of the respective zones are summarized in Table 2. 2) The texture of the rocks of the biotite hornfels zone resembles that of sandstone ; the rocks of the biotite-cordierite-potash feldspar zone has a normal hornfels texture. On the other hand, the rocks of the biotite-hypersthene hornfels zone has diorite-like texture. 3) From the outer biotite-hornfels zone to the inner hypersthene zone, Si, Al and K gradually decrease, on the other hand, Fe'', Fe''', Mg, Ca and Na increase. 4) Judging from the twin-types of plagioclase and textural features (Plate), in the biotitehypersthene hornfels zone, the rocks may have been partially remelted during their metamorphism.
地学団体研究会の論文
1961-07-25