SECOND SERIES BULLETIN OF THE VOLCANOLOGICAL SOCIETY OF JAPAN

PyrocLastic Flow-like Deposit of Futagoyama Volcano

Masato Nakamura, Kazuki Tsuji, Katsusuke Nuruyu

Article type: Article
1976 Volume 21 Issue 1 Pages 1-10
Published: August 15, 1976
Released on J-STAGE: January 15, 2018

DOIhttps://doi.org/10.18940/kazanc.21.1_1

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Futagoyama volcanoes at Kunisaki peninsula, Kyushu, consist of many lava domes of pyroxene andesite, hornblende andesite and biotite hornblende dacite. Pumiceous deposit with two parts, stratified tuffuceous mud bed (the upper) and pumice rich bed (the lower), is found at Matamizu, the southern base of the volcanoes. Studying the deposit, it is concluded the the pumices were empted perhaps as pyroclastic flow from the Futagoyama volcanoes at its almost last stage and then deposited in the shallow water enviroment.

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Petrology and Chemistry of the Volcanic Rocks from the Western and Southern Part of Izu Peninsula, Central Japan

Hajime Kurasawa, Kaori Michino

Article type: Article
1976 Volume 21 Issue 1 Pages 11-29
Published: August 15, 1976
Released on J-STAGE: January 15, 2018

DOIhttps://doi.org/10.18940/kazanc.21.1_11

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In the Izu Peninsula, Quaternary volcanoes arearranged apparently on two lines of NE direction. The volcanoes of Ida, Daruma, Tanaba, and Irozaki alkali basalts distribute on the west line in the peninsula (Fig.1). Most of the rocks of those volcanoes range in composition from basaltic andesite to andesite. Only a little alkaline basalt is represented in the southern end of the peninsula. Microscopically, the following rock types are distinguished: olivine-bearing two-pyroxene andesite (type Yd) for Darnma Volcano, olivine-augite andesite～basaltic andesite (IVc,IVb→c) for Ida Volcano, olivine-bearing hypersthene andesite (IId→c) for Tanada. Volcano, two-pyroxene andesite (Vc, Vd→c) for Tenshi and Jaishi Volcanoes, and olivine-augite basalt (IVb) of the Irozaki alkali basalts.

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High Temperature Experiments Related to Fe-Ti-oxide Minerals in Volcanic Rocks

Takashi Katsura, Kenzo Kitayama, Ryuji Aoyagi, Sadao Sasajima

Article type: Article
1976 Volume 21 Issue 1 Pages 31-56
Published: August 15, 1976
Released on J-STAGE: January 15, 2018

DOIhttps://doi.org/10.18940/kazanc.21.1_31

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After reviewed previous petrological and chemical studies on Fe-Ti oxides in igneous rocks, two facts were emphasized to develop the further study of titanomagnetite in alkali basalts, that is, (1) the oxidation state of titanomagnetite, and (2) high contents of both Mg and Al in titanomagnetite. A series of the present studies comprise two parts, and This is concerned with the background to interpretate the equilibrium compositoins of both ilmenite-hematite and ulvospinel-magnetite solid solutions during decreasing temperture. Experimental results clarified the equilibria in the FeO-Fe₂0₃-Ti0₂ system at 1OOO°, 1100°, 1200℃, and compared it with that obtained by Webster and Bright. By applying the results obtained by Taylor, and Buddington and Lindsley together with the present study, the equilibrium compositions of both solid solutions were explained under two conditions of constant composition of bulk mixture and constant oxygen partial pressure during decreasing temperature. The exchange reaction equilibrium, Fe₂Ti0₄+Fe₂0₃=Fe₃0₄+FeTi0₃, was proposed to treat with the equilibrated compositions of ilmenite-hematite and ulvospinel-magnetite solid solutions at temperature above 1000℃.

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¹⁴C Ages of Tairoike and Yaema lateral explosion craters, Miyake-jima volcano, Izu.

Shozo Yokoyama, Tadashi Arai

Article type: Letter
1976 Volume 21 Issue 1 Pages 57-58
Published: August 15, 1976
Released on J-STAGE: January 15, 2018

DOIhttps://doi.org/10.18940/kazanc.21.1_57

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