日本鉱物科学会研究奨励賞第 18 回受賞者
ベトナムに分布する変成岩類の多様性とその形成過程
キーワード:
P-T-t conditions,
Protolith,
Permian-Triassic,
Ordovician-Silurian,
Trans Vietnam Orogenic Belt
2016 年 45 巻 1 号 p. 26-32
詳細
2016 年 45 巻 1 号 p. 26-32
Trans Vietnam Orogenic Belt distributed in north to central Vietnam includes various types of metamorphic rocks. Most metamorphic rocks show the Permian-Triassic ages and are characterized by decompressional evolution with various metamorphic thermal gradients (8-25 ℃/km). In contrast, some metamorphic rocks having the Ordovician-Silurian age show isobaric heating prograde stage at low-pressure condition (25-30 ℃/km). Granitic rocks also show the Permian-Triassic or Ordovician-Silurian ages. The older granitoids have volcanic arc chemical signature, some of which were metamorphosed at the Permian-Triassic. These results suggest that island arc tectonic setting at the Ordovician-Silurian, where arc magmatism heated the arc crust and caused the low-pressure (with isobaric heating) metamorphism at this period. The Permian-Triassic metamorphic rocks and granitoids were formed by subsequent continental collision and subduction of the Indochina craton together with the past Ordovician-Silurian island arc beneath the South China craton.
