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[O06-P41] Circulating environment of hydrothermal solution based on the oscillatory zoned structure discovered from amphibole
Keywords:hydrothermal solution, oscillatory zoned structure, subsolidus
The oscillatory zoned structure of amphibole has recorded ion substitution due to the influence of the circulation of hydrothermal solution in a subsolidus environment after crystallization. The authors discovered a clear oscillatory zoned structure from amohibole of granodiorite in the Sanyo-belt for the first time. No similar microstructure has been found in dacitic amphibole, a volcanic rock formed by the consolidation of neutral magma active in the area at about the same time.
Compared to amphibole in plutonic rocks of the San-in belt, where the oscillatory zoned structure has developed over a wide area, the degree of development of the microstructure of amphibole is lower in the plutonic rocks of the San-yo belt. Since magma intruded into deep areas where hydrothermal solution due to foaming were less likely to form, it is presumed that the circulation of hydrothermal solution was in a reducing environment where it was less likely to occur than in the San-in belt. Amphibole, which forms an oscillating zone structure, forms a dark green rim at the outermost edge. This suggests that it was the oxidative environment of the final stage. On the other hand, volcanic rocks such as dacites have a short time to solidify and are a reductive environment, so hydrothermal solution is less likely to form or circulate.
Compared to amphibole in plutonic rocks of the San-in belt, where the oscillatory zoned structure has developed over a wide area, the degree of development of the microstructure of amphibole is lower in the plutonic rocks of the San-yo belt. Since magma intruded into deep areas where hydrothermal solution due to foaming were less likely to form, it is presumed that the circulation of hydrothermal solution was in a reducing environment where it was less likely to occur than in the San-in belt. Amphibole, which forms an oscillating zone structure, forms a dark green rim at the outermost edge. This suggests that it was the oxidative environment of the final stage. On the other hand, volcanic rocks such as dacites have a short time to solidify and are a reductive environment, so hydrothermal solution is less likely to form or circulate.