四國吉野川地方の大歩危砂岩片岩層中の碎屑物質について
スポンサーリンク
概要
- 論文の詳細を見る
1) G., Kojima (1950) divided the so-called Sambagawa crystalline schists complex of the central part of Shikoku into the Nishiya Group (the lower) and the Yoshinogawa Group (the upper), and named the clino-unconformity between them Minamihiura unconformity., The Oboke sand-stone-schist beds belong to the lower part of Yoshinogawa Group., 2) About 40 pebbles were collected from the conglomerate-schists occurring in the Oboke sandstone-schist beds., They are classified according to the original rock-species as follows : -1) granite, 2) granite-aplite, 3) fine-grained biotite-quartz-diorite, 4) granite-porphyry, 5) quartz-porphyry, 6) qsuartz-porphyrite, 7) porphyrite, 8) andesite, 9) qsuartzite, 10) sandstone, 11) clayslate, and 12) basic igneous rocks, the original rock-species of which cannot be known precisely, Among them, 4) and 5) cover more than 90% of all pebbles, 3) The relic clastic minerals in the Oboke sandstone-schists were also examined., Quartz and plagioclse are present in all sandstone-schists ; orthoclase, microcline, and augite are common ; brown or green common hornblende, tourmaline (brownish), garnet, allanite, epidote, titanite, and zircon are sporadic., The areal distribution of the characteristic clastic minerals is shown in Fig., 1., The lower part of the sandstone-schist beds and the northern region are characterized by augite, while the upper part and the southern region by tourmaline., 4) The pebbles 7) to 11), and augite and saussuritized basic plagioclase may have been derived from rocks of the Nishiiya Group, which are composed of crystalline schists derived from basic igneous and pyroclastic rocks, clay-slates, sandstone, and siliceous rocks., The pebbled 1) to 6), and quartz, orthoclase, microcline, sodic plagioclase, allanite, garnet, and tourmaline indicate that acid igneous rocks were exposed on the surface when the conglomerates and sandstones were laid down., Judging from the petrographical characteristics of these acid igneous rocks, they may have been intruded into the shallower zone of earth's crust or extruded on the surface, The direct relation between these acid igneous rocks and the Nishiiya Group cannot be known, but the writers believe that the forme was intruded into the latter.,
- 日本地質学会の論文
- 1950-10-05