Electron microprobe analyses of rock-forming minerals from the eastem Iratsu epidote amphibolite mass in the Sambagawa metamorphic belt, central Shikoku, Japan
Electron microprobe analyses of rock-forming minerals from the eastem Iratsu epidote amphibolite mass in the Sambagawa metamorphic belt, central Shikoku, Japan
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日本四国中部三波川变质带东部 Iratsu 绿帘石角闪岩体造岩矿物的电子显微探针分析
DOI：
10.1111/j.1525-1314.1990.tb00630.x
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发表时间：
1994
影响因子：
3.4
通讯作者：
チュウ タナカ
中科院分区：
文献类型：
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作者：
チュウ タナカ
变质作用最高温度时期产生的矿物反映了三巴川带的热构造，其特征一般为构造桩中部出现品位最高的片岩。本文以四国中部三巴川片岩层序上位为例，分析了该构造的成因。四国中部三巴川片岩层序上层由构造水平由高到低依次为Saruta推覆体II、Saruta推覆体I和Fuyunose推覆体3个推覆体组成。Saruta推覆体II从石榴石带、钠长石-黑云母带到寡长岩-黑云母带，变质品位呈递减趋势。Saruta推覆体I主要由钠长石-黑云母带组成，部分由寡长岩-黑云母带组成，但变质品位的增加方向不明确。富云鼻推覆体变质品位呈上升趋势，由蓝绢石带向辉石带转变。结果表明，沙罗塔推覆体II和沙罗塔推覆体ⅰ是被翻覆后与福游鼻推覆体发生机械耦合的。三巴川变质场是变质作用中温度最高的阶段，其热梯度倒转，其热结构与俯冲杂岩较深处的热结构相当。
The thermal structure of the Sambagawa belt, which is reflected by minerals produced during the highest temperature of metamorphism, generally is characterized by the occurrence of the highest grade schists in the middle of the structural pile. The origin of this structure has been analysed in the upper horizon of the Sambagawa schist sequence in Central Shikoku as an example for the structure of the whole belt. The upper horizon of the Sambagawa schist sequence in Central Shikoku consists of three nappes, the Saruta nappe II, the Saruta nappe I and the Fuyunose nappe in descending order of structural level. The Saruta nappe II shows a downward increase of metamorphic grade from the garnet zone, through the albite‐biotite zone, to the oligoclase‐biotite zone. The Saruta nappe I consists mainly of rocks in the albite‐biotite zone and partly in the oligoclase‐biotite zone, but the direction of the increase of metamorphic grade is not clear. The Fuyunose nappe shows an upward increase in metamorphic grade which changes from the glaucophane zone to the barroisite zone. It is concluded that the Saruta nappe II and Saruta nappe I were overturned and then mechanically coupled with the Fuyunose nappe. The Sambagawa metamorphic field, which is of the highest temperature phase of metamorphism, appears to have had an inverted thermal gradient and a thermal structure comparable with that expected in the deeper parts of a subduction complex.