佐渡島の変成岩と花崗岩類 : 概報

概要

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Sado island, 30 kilometers off the Japan Sea coast of Niigata prefecture (northern part of central Japan), is composed mainly of the Tertiary volcanic rocks. At the northern tip of the island, basement rocks are exposed nearly 10 kilometers just along the coast line. Another narrow belt of basement rocks is located at the southern part of the island as shown in Figure 1. All these basement rocks are metamorphic rocks and granitic rocks which have been formed in the following geologic episode. Paleozoic sedimentary rocks with considerable amount of volcanic material were folded regionally and became phyllitic by the regional metamorphism, accompanied with the intrusion of dioritegabbro. Afterwards, porphyritic hornblende-biotite quartz diorite-granodiorite intruded into the regional metamorphic rocks. Heat effect was dominant at the time of the second intrusion. The regional metamorphic rocks not metamorphosed by the heat of the second intrusion might be of greenschist facies, judging from the following mineral assemblages ; pelitic rock : graphite-chloritemuscovite-albite ; andesitic rock : actinolite-epidotechlorite -oligoclase.
地学団体研究会の論文
1966-05-30