東中国, 三朝・奥津・湯原地域の白亜紀後期〜古第三紀火成岩類

概要

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Two stages of volcano-plutonism are recognized in the Misasa-Okutsu-Yubara area. The older stage is represented by the Cretaceous volcanic rocks and the Imbi Intrusives. The younger one is represented by the Paleogene volcanic rocks and the Namariyama intrusives. The Cretaceous volcanic rocks are composed of andesitic to rhyolitic lavas and pyroclastics including welded tuffs. The activity of the Imbi Intrusives began with the intrusion of gabbro and quartz gabbro, most of which constitute small stocks. The composition of succeeding intrusions generally varied to more acid one. Some of the granodiorite and granite constitute composite masses. The batholithic Tottori Granite, mainly composed of biotite granite, intrude data later stage. The dikes of diabase and porphyrite would have finally intruded. Paleogenevolcanic rocks are composed mainly of andesitic lava and pyroclastics. They unconformably overlie the Imbi Intrusives. The Namariyama intrusives are composed of granophyre, granite porphyry, fine-grained biotite granite to granodiorite and others, characterized by hypabyssal texture. They intruded the Paleogene volcanic rocks.
日本地質学会の論文
1979-09-20