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ID 27366
file
creator
NDC
Earth sciences. Geology
abstract
The main purpose of this paper is throwing light on the mechanism of emplacement of the Hiroshima granite and on the space problem of volcano-plutonism in the Inner Zone of Southwest Japan during the late Cretaceous. In order to discuss these problems which are classical and have so far been unsolved, the author has selected the Togouchi-Yuu-Takehara district as a granite field of the San-yo zone. In the southern end of the district, the granite is in contact with Ryoke granitic and metamorphic rocks formed in 10km depth of crust, and in the central area it intruded into pre-Cretaceous sedimentary rocks and into both the sedimentary rocks and Cretaceous surficial volcanic rocks in northern and eastern areas. The author have investigated the granite distributed in the Togouchi area and another several areas in the district, focuing mainly on contact feature between the granite and wall rocks and internal structure of the granite mass. As a result, it is clarified that throughout the district the Hiroshima granite is not a uniform mass but a mass formed by accumlation of layered bodies of granitic rocks. In the mass, rather mafic granite as granodiorite or hornblende granite occurs overlying rather felsic granite as medium to coarse-grained biotite granite. The forming order of them is closely connected with the stratigraphical sequence of the Cretaceous volcanic rocks. As a whole, it can be regarded that the Hiroshima granite is a large tabular mass gently dipping toward the south, and that the Hiroshima granite passively intruded along the fracture zone gently dipping southward, and at the head of the zone the Cretaceous volcanic activities took place. Additionaly, the stress field during and after the emplacement of granodiorite in the Togouchi area has been analysed based upon microfabric and homogenization temperature of fluid inclusion planes in quartz. Finally, the author propose flat-dike type mass for the emplacement mechanism of a large granite mass.
journal title
Bulletin of the Faculty of School Education, Hiroshima University. Part II
volume
Volume 17
start page
95
end page
150
date of issued
1995-01-20
publisher
広島大学学校教育学部
issn
0387-4869
ncid
language
eng
nii type
Departmental Bulletin Paper
HU type
Departmental Bulletin Papers
DCMI type
text
format
application/pdf
text version
publisher
department
Graduate School of Education
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