兵庫県南東部, 六甲山地の白亜紀後期花崗岩類の岩体・岩相区分と火成活動史 [in Japanese] Lithologic variation and plutonic history of the Late Cretaceous granitoids in the Rokko Mountains, southwest Japan [in Japanese]
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兵庫県南東部に位置する六甲山地に分布する白亜紀後期花崗岩類の岩相区分と岩石記載を行った. これらの花崗岩類は, 布引花崗閃緑岩, 八幡谷花崗岩, 土橋石英閃緑岩, 六甲花崗岩に区分される. このうち, 布引花崗閃緑岩はその岩相により, 斑状相と等粒状相の2つの岩相に区分される. また, 六甲花崗岩類は, 中～粗粒相, 細粒相, 微文象相の3つの岩相に区分される. 六甲花崗岩は, 細粒相が岩体上部に, 中～粗粒相が岩体中, 下部に分布しており, 垂直的な岩相変化を示す. さらに, 六甲花崗岩の岩体の上部ではSiO<SUB>2</SUB>やK<SUB>2</SUB>Oに富み, 下部はTiO<SUB>2</SUB>, MgO, CaOに富むなど, 化学組成も垂直方向に変化する.
Late Cretaceous granitic rocks are widely distributed in the Rokko Mountains. They are divided into Nunobiki Granodiorite, Yahatadani Granite, Dobashi Quartz Diorite and Rokko Granite, according to their field occurrence and petrographical characteristics. The Nunobiki Granodiorite occurs at the southern foot of the Rokko Mountains. This granodiorite shows a weak gneissic fabric, trending east-west and dipping to the north. This rock is subdivided into porphyritic and equigranular facies. The Yahatadani Granite occurs as a small pluton in the southeastern Rokko Mountains. The Nunobiki Granodiorite and the Yahatadani Granite belong to the Younger Ryoke granitoids. The Dobashi Quartz Diorite occurs as aggregations of small xenoblocks within the Rokko Granite. The Rokko Granite is the most extensively developed pluton in the Rokko Mountains. This rock is subdivided into medium- to coarse-grained facies, fine-grained facies and micrographic facies according to the grain-size differences and petrographical characteristics. The Rokko Granite is a vertically zoned pluton. The fine-grained facies occupies the higher part, the medium-grained facies the middle part, and the coarse-grained facies the lower part in altitude of the Rokko Mountains. The upper part of the Rokko Granite is rich in SiO<SUB>2</SUB> and K<SUB>2</SUB>O, whereas the lower part of the Rokko Granite is rich in TiO<SUB>2</SUB>, MgO, and CaO.
- The Journal of the Geological Society of Japan
The Journal of the Geological Society of Japan 110(8), 452-462, 2004-08-15
The Geological Society of Japan