只見-片品構造帯の提唱 : 津川-会津区における只見南部地域の地質構造

概要

論文の詳細を見る
Geological successions of the Tadami area situated in the south-western part of the Tsugawa-Aizu geological province, Northeast Japan are composed mainly of the Pre-Neogene basement rocks and the Neogene green tuff formations. The basement rocks are exposed in the steep mountainous region surrounding the area, and consist of unmetamorphosed late Paleozoic and Mesozoic sediments (slate, grey-wacke, sandstone, chert, limestone etc.) and granitic rocks and basic plutonic rocks intruding these sediments. The Neogene formations in this area are characterized by the acidic volcanic rocks and its pyroclastics, and can be divided into the following seven formations in ascending order; Takisawagawa (Shionomata), Oshio, Ogawazawa, Fuzawa, Matsusakatoge, Yashioda and Komadotoge formations. The structural features of the area are recognized three structural trends such as NW-SE, N-S and NE-SW systems. Among them the NW-SE trend (Tadami-Ina structural zone) is most conspicuous, being observed in the trends of the zones of upheaval and dubsidence, axes of folding, strikes of major faults, alignment of extrusive and intrusive rocks, and even in alignment of kuroko ore deposits. In addition to these NW-SE structural trends, the Tadakozawa-Ogawa fracture zone (SHIMADA et al., 1969) which probably acted as feeders for a large amount of acidic volcanics in the Ogawazawa formation, is N-S trending, and is also one of the noticeable structure in this area. It has a width about 0.8-1.0 Km at Tadakozawa of the north side, but about 4-6 Km at Ogawa of the south side. In the Tadakozawa-Ogawa fracture zone, lava and pyroclastics of rhyolitic to dacitic composition erupted from numerous N-S trending fissures, and also N-S trending dikes of basaltic composition are observed in this zone. Occurrence of multiple dykes of rhyolite and basalt concerning bimodal volcanism is one of the features in this fracture zone. Several small bodies of gabbroic to ultrabasic rocks were found along the Kurodani River in the southern extension of the zone. Occurrence of these rocks is also a noticeable feature in the zone. Furthermore, mafic rocks such as gabbroic and diabasic rocks occur along the Katashina River in Gunma Prefecture in the southern extension of the fracture zone, these rocks were called the Katashina basic rocks by HAYAMA et al. (1969). The Katashina basic rocks are confined with the Katashina tectonic zone (YAMASHITA et al., 1965) which defines a boundary between the Joetsu metamorphic belt and the Ashio belt. On the basis of the structural features and similarity in both area mentioned above, the author proposes the "Tadami-Katashina tectonic zone" run in connection with the Tadakozawa-Ogawa fracture zone and the Katashina tectonic zone. It is considered that this tectonic zone has an important significance in the Tsugawa-Aizu geological province.
1982-01-25

只見-片品構造帯の提唱 : 津川-会津区における只見南部地域の地質構造

スポンサーリンク

概要

著者

関連論文

スポンサーリンク