Low-grade Progressive Metamorphism of Pelitic Schists of the Sazare area, Sanbagawa Metamorphic Terrain in central Sikoku, Japan
Low-grade Progressive Metamorphism of Pelitic Schists of the Sazare area, Sanbagawa Metamorphic Terrain in central Sikoku, Japan
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日本四国中部三波川变质地 Sazare 地区泥质片岩的低级渐进变质作用
DOI：
10.1093/petrology/15.2.361
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发表时间：
1974
影响因子：
3.9
通讯作者：
S. Banno
中科院分区：
文献类型：
--
作者：
Hisayuki Kurata;S. Banno
四国中部萨扎雷地区的三波川变质地形根据泥质片岩矿物组合分为 A、B 和 C 三个渐进变质作用带。 A区的特征矿物组合为多硅白云母+绿泥石，C区的特征矿物组合为多硅白云母+绿泥石+石榴石，较高品位部分可能含有黑云母。 B区是A和C之间的过渡区。随着品位的增加，石榴石边缘和绿泥石的化学变化很明显：绿泥石中的MnO和FeO含量降低，石榴石边缘的FeO含量随着品位的增加而增加。绿泥石-石榴石边缘对的 Fe-Mg 分配系数也随着组合定义的品位而系统地变化，这表明渐进变质作用主要是由于温度升高。巴罗文黑云母带与现区C区组合的差异，要么是由于后者普遍出现斜帘石，要么是由于三波川带与苏格兰黑云母带相比，平衡压力较高，导致共生关系不同。纬向测绘揭示的现区热结构要求存在大规模的翻转构造，该构造的年代晚于主要矿物的形成。
The Sanbagawa metamorphic terrain in the Sazare area, central Sikoku, is divided into three zones of progressive metamorphism, A, B, and C, on the basis of mineral assemblages of pelitic schists. The characteristic mineral assemblage of zone A is phengite+chlorite and that of zone C is phengite+chlorite+garnet with biotite possibly at a higher-grade part. Zone B is transitional between A and C. Variation of the chemistry of garnet rim and chlorite with increasing grade is conspicuous: the MnO and FeO contents of chlorite decrease and the FeO content of garnet rims increase with grade. The Fe-Mg partition coefficient for the chlorite—garnet rim pair also changes systematically with the grade defined by the assemblage suggesting that the progressive metamorphism is primarily due to temperature increase. The difference in assemblages between the Barrovian biotite zone and zone C of the present area is due either to the common occurrence of clinozoisite in the latter or to the different paragenetic relations induced by higher-pressure of equilibrium in the Sanbagawa belt as compared with the Scottish one.The thermal structure of the present area revealed by zonal mapping requires the presence of a large-scale overturned structure, which postdated the major mineral formation.