start-ver=1.4
cd-journal=joma
no-vol=4
cd-vols=
no-issue=1
article-no=
start-page=33
end-page=40
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=1997
dt-pub=19970920
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=Ferroglaucophane schist from the Ohsa-yama srea, Okayama Prefecture, Japan
kn-title=岡山県大佐山地域に産するフェロ藍閃石片岩
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=A ferroglaucophane schist occurs in fault contact with serpentinites at the Ohsa-yama area, Southwest Japan. It consists of albite, ferroglaucophane and actinolite with small amounts of stilpnomelane, sphene, apatite and K-feldspar. Petrological studies reveal that the schist was originally igneous rock of felsic or intermediate composition and has suffered two stages of metamorphism : ferroglaucophane has been formed at the first stage and actinolite at the second stage. In a basic schist from the same outcrop that the ferroglaucophane schist occurs, tremolitic amphibole instead of alkali amphibole has been formed along with chlorite, phengite and albite. Such a difference in mineral association between the schists is ascribed to a difference in whole rock composition, particu-larly in Fe/Mg ratio.
 Some of the schists from th Ohsa-yama area characteristically contain glaucophane or ferroglaucophane and have low Fe2O3/FeO ratios, forming a striking contrast to the crossite schists that commonly occur in the so-called "Sangun metamorphic terrane". These facts suggest that the alkali amphiboles of the Ohsa-yama schists were formed under higher P/T and more reducing conditions than those of the regional metamrphic rocks. On the other hand, development of the second-stage actinolite in the ferroglaucophane schist is consistent with the meta-morphic parageneses of greenschists from adjacent areas. Consequently the ferroglaucophane schist is considered one of the tectonic blocks that were captured by mobile serpentinites and have suffered the regional metamor-phism after the emplacement of the serpentinites into the present geologic position.
en-copyright=
kn-copyright=

en-aut-name=NozakaToshio
en-aut-sei=Nozaka
en-aut-mei=Toshio
kn-aut-name=野坂俊夫
kn-aut-sei=野坂
kn-aut-mei=俊夫
aut-affil-num=1
ORCID=

affil-num=1
en-affil=
kn-affil=岡山大学理学部地球科学科
en-keyword=ferroglaucophane
kn-keyword=ferroglaucophane
en-keyword=petrology
kn-keyword=petrology
en-keyword=tectonic block
kn-keyword=tectonic block
en-keyword=serpentinite
kn-keyword=serpentinite
en-keyword=high P/T metamorphism,
kn-keyword=high P/T metamorphism,
en-keyword=Ohsa-yama
kn-keyword=Ohsa-yama
en-keyword=Sangun metamorphic terrane
kn-keyword=Sangun metamorphic terrane
en-keyword=Southwest Japan
kn-keyword=Southwest Japan
END

start-ver=1.4
cd-journal=joma
no-vol=2
cd-vols=
no-issue=1
article-no=
start-page=1
end-page=12
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=1995
dt-pub=19950920
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Mineral paragenesis in thermally metamorphosed serpentinites, Ohsa-yama, Okayama Prefecture
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=The Ohsa-yama ultramafic body, which consists of several types of serpentinized peridotites, underwent contact metamorphism caused by a Cretaceous granite intrusion ; this metamorphism resulted in the formation of contact aureole, 1.5-2.0 km wide, around the granite intrusion, and produced progressive mineral changes in metaserpentinites toward the contact between the Ohsa-yama body and the granite intrusion. On the basis of analysis of mineral paragenetic relations, the Ohsa-yama ultramafic body can be divided into three zones with progressive changes in mineral assemblages as follows : 
 Zone Ⅰ : serpentine ± chlorite ± brucite
 Zone Ⅱ : olivine + talc ± tremolite ± chlorite
 Zone Ⅲ : olivine + orthopyroxene ± tremolite ± spinel
Zone Ⅰ corresponds to the parts unaffected by the thermal event, and Zones Ⅱ and Ⅲ correspond to the thermally metamorphosed parts of the Ohsa-yama body. The results obtained in this study are generally consistent with those of the  previous studies on metamorphic peridotites from the Sangun and Muzuru zones.
en-copyright=
kn-copyright=

en-aut-name=NozakaToshio
en-aut-sei=Nozaka
en-aut-mei=Toshio
kn-aut-name=野坂俊夫
kn-aut-sei=野坂
kn-aut-mei=俊夫
aut-affil-num=1
ORCID=

en-aut-name=ShibataTsugio
en-aut-sei=Shibata
en-aut-mei=Tsugio
kn-aut-name=柴田次夫
kn-aut-sei=柴田
kn-aut-mei=次夫
aut-affil-num=2
ORCID=

affil-num=1
en-affil=
kn-affil=Department of Earth Sciences, Faculty of Science Okayama University

affil-num=2
en-affil=
kn-affil=Department of Earth Sciences, Faculty of Science Okayama University
en-keyword=peridotite
kn-keyword=peridotite
en-keyword=serpentinite
kn-keyword=serpentinite
en-keyword=thermal metamorphism
kn-keyword=thermal metamorphism
en-keyword=contact metamorphism
kn-keyword=contact metamorphism
END

start-ver=1.4
cd-journal=joma
no-vol=1
cd-vols=
no-issue=1
article-no=
start-page=1
end-page=8
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=1994
dt-pub=19940920
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Petrography of primary peridotites from the Ohsa-yama area, Okayama Prefecture
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Ultramafic rocks exposed around Mt. Ohsa(= Ohsa-yama), Okayama prefecture, designated as "Ohsa-yama ultramafic body" all together, are one of the Alpine-type peridotites in the Sangun metamorphic belt. They are intensely serpentinized and locally suffered contact metamorphism by younger granitic intrusions. In a por-tion of the ohsa-yama body where it has been affected by the contact metamorphism, the constituent minerals, texture and structure of primary ultramafic rocks have been locally preserved. Petrographic studies revead that the primary ultramafic rocks of the ohsa-yama body consist domimantly of dunite and harzburgite possessing no obvious layering, and their constituent minerals are similar in composition to those of the Tari-Misaka and Ashidachi ultramafic bodies. These features indicate that unlike the Ochiai-Hokubo body, the Ohsa-yama ultra-mafic body belongs to the "massive group" of the Arai's (1980) classification.
en-copyright=
kn-copyright=

en-aut-name=NozakaToshio
en-aut-sei=Nozaka
en-aut-mei=Toshio
kn-aut-name=野坂俊夫
kn-aut-sei=野坂
kn-aut-mei=俊夫
aut-affil-num=1
ORCID=

en-aut-name=ShibataTsugio
en-aut-sei=Shibata
en-aut-mei=Tsugio
kn-aut-name=柴田次夫
kn-aut-sei=柴田
kn-aut-mei=次夫
aut-affil-num=2
ORCID=

affil-num=1
en-affil=
kn-affil=Department of Earth Sicences, Faculty of Science Okayama University

affil-num=2
en-affil=
kn-affil=Department of Earth Sicences, Faculty of Science Okayama University
en-keyword=petrography
kn-keyword=petrography
en-keyword=dunite
kn-keyword=dunite
en-keyword=harzburgite
kn-keyword=harzburgite
en-keyword=massive ultramafic body
kn-keyword=massive ultramafic body
END

start-ver=1.4
cd-journal=joma
no-vol=17
cd-vols=
no-issue=1
article-no=
start-page=1
end-page=5
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2010
dt-pub=20101224
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=西南日本の熱変成超苦鉄質岩体中のかんらん石と輝石の組成変化に関する覚書
kn-title=A note on compositional variation of olivine and pyroxene in thermally metamorphosed ultramafic complexes from SW Japan
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=This short article presents some diagrams showing the compositional variations of primary and metamorphic olivine, orthopyroxene and clinopyroxene in peridotites and serpentinites from thermally metamorphosed ultramafic complexes in SW Japan. In contrast to olivine, which shows a gradual change of chemical composition corresponding with metamorphic grade, orthopyroxene and clinopyroxene show clear differences in composition between primary and metamorphic phases. Compared with primary pyroxenes, even though their compositions could be variable depending on original rock composition, metamorphic orthopyroxene and
metamorphic clinopyroxene is clearly deficient in Cr(2)O(3) and CaO, and in Cr(2)O(3) and Al(2)O(3), respectively. These characteristics are useful for the discrimination between the pyroxenes of different origin.
en-copyright=
kn-copyright=

en-aut-name=NozakaToshio
en-aut-sei=Nozaka
en-aut-mei=Toshio
kn-aut-name=野坂俊夫
kn-aut-sei=野坂
kn-aut-mei=俊夫
aut-affil-num=1
ORCID=

affil-num=1
en-affil=
kn-affil=Department of Earth Sciences, Faculty of Science, Okayama University
en-keyword=chemical composition
kn-keyword=chemical composition
en-keyword=olivine
kn-keyword=olivine
en-keyword=orthopyroxene
kn-keyword=orthopyroxene
en-keyword=clinopyroxene
kn-keyword=clinopyroxene
en-keyword=metaperidotite
kn-keyword=metaperidotite
END

start-ver=1.4
cd-journal=joma
no-vol=30
cd-vols=
no-issue=1
article-no=
start-page=1
end-page=12
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2024
dt-pub=20240331
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=Petrological characteristics of the stone chamber of Tobiotsuka Kofun, Okayama Prefecture
kn-title=鳶尾塚古墳の石室石材の岩石学的特徴
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=　Tobiotsuka Kofun, a tumulus built on the Misu Hills in the Kofun period, has a horizontal stone chamber made of huge stone blocks with a width up to 2 meters or more. To specify the source of the stone blocks, we carried out the measurement of magnetic susceptibility, petrographic observation, and chemical analysis of minerals. The stones are amphibole-biotite granite with phenocrystic large grains of K-feldspar. The back-wall stone of the chamber has higher magnetic susceptibility than ceiling and side-wall stones, which probably results from a higher amount of magnetite formed by the alteration of biotite in the back-wall stone. Furthermore, the back-wall stone is different from ceiling stone in that it has lower XMg [Mg/(Mg + Fe) mole ratio], lower Al, Ti, and Na + K contents and higher Si contents of amphibole, higher XMg of biotite, and shows a tendency to have higher Na (albite component) contents at rims of plagioclase crystals and lower Ti contents of zircon. These characteristics of the back-wall stone are similar to those of granite exposed in the Koshinzan area about 2 km northeast of Tobiotsuka Kofun, whereas the ceiling and side-wall stones are similar to granite outcrops in the vicinity of Tobiotsuka Kofun, e.g., in the Midoriyama area. It is concluded that the quarry for the back-wall was located at a different place from that for the ceiling and side-wall stones.
en-copyright=
kn-copyright=

en-aut-name=KANEKOTakahiro
en-aut-sei=KANEKO
en-aut-mei=Takahiro
kn-aut-name=金子峻大
kn-aut-sei=金子
kn-aut-mei=峻大
aut-affil-num=1
ORCID=

en-aut-name=NOZAKAToshio
en-aut-sei=NOZAKA
en-aut-mei=Toshio
kn-aut-name=野坂俊夫
kn-aut-sei=野坂
kn-aut-mei=俊夫
aut-affil-num=2
ORCID=

en-aut-name=SEIKEAkira
en-aut-sei=SEIKE
en-aut-mei=Akira
kn-aut-name=清家章
kn-aut-sei=清家
kn-aut-mei=章
aut-affil-num=3
ORCID=

affil-num=1
en-affil=Department of Earth Sciences, Okayama University
kn-affil=岡山大学大学院自然科学研究科

affil-num=2
en-affil=Department of Earth Sciences, Okayama University
kn-affil=岡山大学学術研究院環境生命自然科学学域

affil-num=3
en-affil=Department of Archaeology, Okayama University
kn-affil=岡山大学学術研究院社会文化科学学域
en-keyword=Tobiotsuka Kofun
kn-keyword=Tobiotsuka Kofun
en-keyword=stone chamber
kn-keyword=stone chamber
en-keyword=granite
kn-keyword=granite
END