DUNITES AND SERPENTINITES IN THE SANBAGAWA METAMORPHIC BELT, CENTRAL SHIKOKU AND KII PENINSULA, JAPAN
DUNITES AND SERPENTINITES IN THE SANBAGAWA METAMORPHIC BELT, CENTRAL SHIKOKU AND KII PENINSULA, JAPAN
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日本中部四国和纪伊半岛三波川变质带中的榴岩和蛇纹岩
DOI：
10.2465/ganko1941.75.14
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
K. Kunugiza
中科院分区：
文献类型：
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作者：
K. Kunugiza
三坝川变质带的大型纯橄榄岩-蛇纹岩岩体产于大型平卧褶皱的轴向带中。东赤石和白贺体（四国中部）和龙门体（纪伊半岛）的橄榄石的结构和化学性质证明了该带中存在两种类型的纯橄榄岩。东赤石体的纯橄榄岩经历了两个阶段的变质作用，导致其橄榄石的成分略有变化，但纯橄榄岩仍然是纯橄榄岩，而白贺和龙门体的纯橄榄岩由蛇纹岩变质新形成的橄榄石组成。新形成的橄榄石中含有磁铁矿、叶蛇纹石、菱铁矿、水镁石和菱镁矿等蛇纹岩矿物作为包裹体，其中部分橄榄石的XFe与NiO含量呈正相关，与岩浆结晶形成的成分趋势相反。白贺和龙门岩体中橄榄石+叶蛇纹石的存在与三坝川地形的热结构相协调。这种协调性和新形成的橄榄石的广泛出现表明，这种纯橄榄岩是在三坝川变质作用期间由蛇纹岩变质形成的。从热历史的观点来看，三坝川变质带中的橄榄岩并非都是东赤石型橄榄岩的简单解体体。
Large dunite-serpentinite masses of the Sanbagawa metamorphic belt occur in the axial zone of large scale recumbent fold. The texture and chemistry of olivines from the Higashi-Akaishi and Shiraga bodies (central Shikoku) and the Ryumon body (Kii peninsula) demonstrate the two types of dunite to be present in this belt. Dunites of the Higashi-Akaishi body had experienced two stages of metamorphism, resulting in slight compositional change of their olivines, but the dunites remained dunite, whereas those of the Shiraga and Ryumon bodies consist of olivines newly formed by the metamorphism of serpentinite. The newly formed olivines contain the minerals of serpentinite, such as magnetite, antigorite, chlorite, brucite and magnesite, as inclusions, and some of them have a positive correlation between XFe and NiO content being the reverse to the compositional trend formed by igneous crystallization. The presence of olivine+antigorite in the Shiraga and Ryumon bodies is in harmony with the thermal structure of the Sanbagawa terrain. This harmony and the widespread occurrence of newly formed olivine indicate that this type of dunite was formed by the metamorphism of serpentinite during the Sanbagawa metamorphism. From the view point of thermal history, not all the peridotites in the Sanbagawa metamorphic belt are simple dismembered masses of the Higashi-Akaishi-type peridotite.