金華山の地質構造にまつわる若干の問題

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The geological differences between the Ojika peninsula and Kinkazan islet, Miyagi Prefecture, have been known very well since about 70 years ago (Kikuchi, Y., 1891 and Iki, J., 1901); the former is composed principally of the Mesozoic sediments and volcanics, partly intruded by dioritic and gabbroic rocks, and the latter, of granitic rocks, gneissose quartz-diorite and granodiorite accompanied with metamorphic rocks, which were named the Kinkazan metamorphic rocks, such as biotite schist, amphipolite, quartz schist, etc., constituting a narrow belt along the north western margin of the islet. And it has been considered that a fault zone might run from north to south, under a strait of the Kinkazan-seto between the Ojika peninsula and the Kinkazan islet. Quite recently, in this estimated fault zone, dunitic ultramafic rock, partially serpentinized, is found, occurring as a shore roof along the coastcliff of the Kinkazan metamorphic rocks. So, we propose here that the fault zone, with the ultramafic rock, in the Kinkazan-seto, is favourable to be called as the " Kinkazan tectonic line", and the area, composed of the above-mentioned rocks as seen in Kinkazan islet, may correspond to a structural belt, "Kinkazan structural belt". Although the gneissose quartz diorite of Ashizima islet is of the northern extension of the equivalent in Kinkazan islet, the other rocks, such as the" Kinkazan metamorphic rocks" and ultramafic rocks, are not found anywhere, in the north of the Kinkazan islet, because of lying themselves beneath the sea. However, it is fairly presumable that the further extension "towards the north, of the "tectonic line" or structural belt may accord with the median Kitakami structural belt (Kano and Seki, 1954) or the Hikami structural belt (Yamashita, 1957) in the northern part of the South Kitakami Mountains, judging from their geological enviornments.
地学団体研究会の論文
1972-07-25

金華山の地質構造にまつわる若干の問題

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