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Journal of science of the Hiroshima University. Series C, Geology and mineralogy Volume 3 Issue 3-4
published_at 1961-03-15
Structural-Petrological Studies of Metamorphic Complex of the Seburi Mountainland, with Special Reference to its Bearing on the Metamorphism of the Sangun Metamorphic Zone in Northern Kyûshû
INOUE Tamotsu
Abstract
It has long been a theory generally accepted by Japanese geologists that the Sangun metamorphic zone is mainly composed of low-grade metamorphic rocks, and that those higher-grade metamorphic rocks found sporadically in the zone were formed by thermal effect of either older or younger granite.
The writer was interested in the presence of higher-grade metamorphic rocks in the Seburi mountainland, which belongs to the Sangun metamorphic zone, and thenceforth attempted to solve a problem as to whether the higher-grade metamorphic rocks which attain to the amphi-bolite facies in metamorphic grade were formed by the thermal effect of granite or by the dynamo-thermal metamorphism. In an attempt to find a solution to this problem, the writer began in the present paper by giving the outline of the basement geology of Northern Kyûshû as the geo-logical background of the Seburi district, and proceeded to discuss the geology and petrology of the district, with particular reference to the mineral-paragenetic relation and petrofabric analysis.
With regard to the genesis of minerals, especially of garnet, epidote, tourmaline and cumming-tonite, the writer has discussed from the standpoint of the mode of occurrence, and the genesis of biotite and amphibole has been dealt with from the viewpoint of petrofabrics. From the results the writer has drawn the conclusion that garnet, epidote, tourmaline, and cummingtonite were formed by the thermal effect of older granite and the greater part of biotite and amphibole by the preceding dynamo-thermal metamorphism. Therefore, these metamorphic rocks referred to the amphibolite facies were formed not by the thermal effect of older granite, but by the dynamo-thermal metamorphism.
In addition the writer has discussed at some length the geological significance of the above conclusion in the basement geology of Northern Kyûshû.
The writer was interested in the presence of higher-grade metamorphic rocks in the Seburi mountainland, which belongs to the Sangun metamorphic zone, and thenceforth attempted to solve a problem as to whether the higher-grade metamorphic rocks which attain to the amphi-bolite facies in metamorphic grade were formed by the thermal effect of granite or by the dynamo-thermal metamorphism. In an attempt to find a solution to this problem, the writer began in the present paper by giving the outline of the basement geology of Northern Kyûshû as the geo-logical background of the Seburi district, and proceeded to discuss the geology and petrology of the district, with particular reference to the mineral-paragenetic relation and petrofabric analysis.
With regard to the genesis of minerals, especially of garnet, epidote, tourmaline and cumming-tonite, the writer has discussed from the standpoint of the mode of occurrence, and the genesis of biotite and amphibole has been dealt with from the viewpoint of petrofabrics. From the results the writer has drawn the conclusion that garnet, epidote, tourmaline, and cummingtonite were formed by the thermal effect of older granite and the greater part of biotite and amphibole by the preceding dynamo-thermal metamorphism. Therefore, these metamorphic rocks referred to the amphibolite facies were formed not by the thermal effect of older granite, but by the dynamo-thermal metamorphism.
In addition the writer has discussed at some length the geological significance of the above conclusion in the basement geology of Northern Kyûshû.
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PP. 343 - 402