GEOSYNCLINE VOLCANISM OF THE MIKABU GREEN-ROCKS IN THE OKUKI AREA, WESTERN SHIKOKU, JAPAN
GEOSYNCLINE VOLCANISM OF THE MIKABU GREEN-ROCKS IN THE OKUKI AREA, WESTERN SHIKOKU, JAPAN
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日本西四国大久地区三甲绿岩的地同步火山作用
DOI：
10.2465/ganko1941.67.177
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发表时间：
1972
期刊：
影响因子：
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通讯作者：
H. Umemura
中科院分区：
文献类型：
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作者：
Takashi Suzuki;N. Kashima;S. Hada;H. Umemura
(1959, 1966)，蛇绿岩序列由来自上地幔的固态深成岩成分和由玄武质岩浆结晶的火山下和喷出岩成分组成。许多地质学家仍然不愿意接受这个模型，因为现场观测并没有表明这种成因关系，即“深成岩”与浅成岩和喷出岩之间往往存在逐渐的过渡。在这种情况下，蛇绿岩序列显示出所谓的“地层学”，范围从底部具有粗粒颗粒结构的超镁铁质或基性岩石到顶部具有细颗粒结构的连续基性岩石。 Aubouin（1965）将蛇绿岩定义为超镁铁质和基性岩的复杂块体，它们在地槽早期阶段被挤压到优地同步斜域上。根据目前的概念，蛇绿岩浆作用是一种强大的海底玄武岩浆裂隙喷发，在此过程中外表面被冷却，形成包围流体岩浆的细粒地壳，其中发生重力分异。 Reinhardt (1969) 讨论了阿曼蛇绿岩的起源和侵位，并得出结论认为，辉长岩-玄武岩系和超镁铁岩系之间的逐渐过渡是由于辉长岩在深部注入橄榄岩的同化造成的。无论如何，对于蛇绿岩浆作用的深成岩成分与次火山岩浆和喷出岩浆成分之间的亲缘关系，还没有既定的理论。近年来，从地槽火山作用的角度对日本晚古生代海底火山岩进行了许多研究(Kamera，1968、1969；Tanaka，1970；Hashimoto、Kashima和Saito，1970；Sugisaki、Tanaka和Hattori，1970；Kanisawa，1971)。 “Mikabu”绿色岩石沿着三波川结晶片岩带和由古生代地层组成的Chi Chibu 带之间的边界出现，现在被认为是晚古生代Chichibu 地槽上最初的基本海底火山作用的产物（Suzu ki，1966，1967；Iwasaki，1969）。铃木和其他人描述了非凡的岩浆
(1959, 1966), the ophiolite sequence is com posed of plutonic members which have been derived in solid state from the upper mantle, and of subvolcanic and extrusive members which have crystallized from a basaltic magma. Many geologists are still reluctant to accept this model because field observa tions do not suggest such genetic relation, that is, often there are gradual transitions between the "plutonic" and the hypabyssal and extrusive rocks. In such cases the ophiolite sequence shows what may be called "stratigraphy" , ranging from ultramafic or basic rocks with coarse-grained granular texture at the base to successively basic rocks with fine-grained texture at the top. Aubouin (1965) defined the ophiolite as complex masses of ultramafic and basic rocks which were extruded on the eugeosyn clinal domain at the earlier geosynclinal stage. After current conception the ophio litic magmatism is a type of powerful sub marine fissure-eruptions of basaltic magma, during which the outer surface was chilled to form a fine-grained crust enclosing the fluidal magma, in which gravitational differ entiation proceeded. Reinhardt (1969) discussed the origin and emplacement of the Oman ophiolites and concluded that the gradual transition between the group of gabbroic-basaltic suite and that of ultramafic rocks was caused by the assimilation of gabbroic injection into peridotites at a great depth. In any way, there are no established theories on the genetic relation between plutonic members and subvolcanic to ex trusive ones of the ophiolitic magmatism. In recent years, many works have been done about Late-Paleozoic submarine vol canic rocks in Japan from the viewpoint of geosynclinal volcanism (Kanmera, 1968, 1969; Tanaka, 1970; Hashimoto, Kashima and Saito, 1970; Sugisaki, Tanaka and Hattori, 1970; Kanisawa, 1971). The "Mikabu" green-rocks, which occur along the boundary between the belt of Sambagawa crystalline schists and the Chi chibu Belt, consisting of Paleozoic forma tions, are now thought to be a product of initial basic submarine volcanism on the Late-Paleozoic Chichibu geosyncline (Suzu ki, 1966, 1967; Iwasaki, 1969). Suzuki and others have described remarkable magmatic