飛騨変成帯の構造区分と造構史

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The Hida metamorphic region, central Japan is mainly made up of various gneisses and plutonic rocks of the Funatsu-stage intruding into the Hida gneisses at the early Mesozoic age. Its tectonic divisions and development are discussed in this report. The gneisses are divided into three major tectonic provinces, based on the minor and major structures, lithological features and distributions: the eastern massif, the central massif and the western massif. Three major tectonic events are presumed in the region: (1) Initial Structure (Structure of the original rocks), (2) Secondary structure (formation of gneisses) and (3) Third structure (superposed deformation associated with the Funatsu-stage plutonism). The Funatsu-stage plutonic rocks occupies among the tectonic units of gneisses and the principal structure of the Hida complex is completed in this stage. A part of the gneisses, especially western-half of the eastern massif and the southern border of the western massif, are reconstructed by the superposition of tectonism at the Funatsu-stage. The northern-half of western massif (the Kubusugawa zone) is distinguishable from the eastern and central massifs (the Wadagawa-Kamioka zone) by the differences of major structure, tectonic and degree of folding, grades of deformation and migmatite structure etc. The Wadagawa-Kamioka zone is characterized by (1) N-S structural trend, (2) intence flow-type tight〜isoclinal foldings with acute limb angle, stort wave-length and high ratios of wave-length: amplitude (1:1〜3) and (3) complex and well deformed migmatite structure and diopside-bearing quartz-feldspathic rocks (Inishi-type rocks) and trondhjemitic rocks as neosomes. On the other hand, gneisses in the Kubusugawa zone are less deformed. The foldings are gentle〜open type with long wave-length and low ratios of wave-length: amplitude (1:1〜0.5). Migmatite structure is characterized by the simple veinlets injection of grey granite showing entectic and metatectic nature of formation. However, migmatite structure of the Wadagawa-Kamioka zone suggests the ectectic and metablastic origin during on the rather autochthonous processes. The differences between the Kubusugawa zone and the Wadagawa-Kamioka zone are seemed to be originated from the initial stage of developments of the Hida region zone are seemed to be originated from the initial stage of developments of the Hida region. It is estimated that the lithological and lithofacial features of the original strata are more uniform over the wide area in the Kubusugawa zone than in the Wadagawa-Kamioka zone. Although, many controversial problems still remain, two zones are recognized as the fundamental tectonic divisions of the Hida region, thus the Wadagawa-Kamioka zone is the re-mobile belt around the Kubusugawa zone which may be supposed to be the Precambrian core.
日本地質学会の論文

飛騨変成帯の構造区分と造構史

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