18:15 〜 19:30
[SMP46-P06] 花崗岩体貫入時のマイクロブーディン構造形成中の応力ー歪の関係：東ピルバラ、Mt.Edger花崗岩複合岩体の場合
キーワード：マイクロブーディン構造, 応力, 歪, 花崗岩複合岩体, 始生代
Stress and strain analysis is essential to improving the understanding of deformation process. Microboudinaged columnar minerals can be used as an indicator of stress and strain during the microboudinage for quartzose and calcareous metamorphic tectonites. In this presentation, we discuss the stress and strain history during the microboudinage deduced by the microboudin method with a collaboration of the strain reversal method.
We collected samples of metachert from the Archean Warrawoona greenstone belt around Mt. Edger granite complex, East Pilbara, Western Australia, and identified microboudinaged tourmaline grains embedded within quartz matrix in 10 samples. The result revealed that the samples experienced extensional strain at least -0.56 and differential stress in the range from 3.9 to 11.9 MPa. We obtained stress-strain curves which show increase in differential stress with increasing inverse natural strain (εinv). The frequency distribution of interboudine gaps between separated grains with respect to εinv for boudinaged tourmaline grains shows that end of microboudinage occurred immediately after the peak frequency of fracturing. This occurrence commonly appeared in all the 10 samples. These results provided us with keys to discuss a stress-strain history during the microboudinage in relation to evolution of the granite complex. The spectacular implication would be a drop or relaxation in increased differential stress at the end of the microboudinage.
We collected samples of metachert from the Archean Warrawoona greenstone belt around Mt. Edger granite complex, East Pilbara, Western Australia, and identified microboudinaged tourmaline grains embedded within quartz matrix in 10 samples. The result revealed that the samples experienced extensional strain at least -0.56 and differential stress in the range from 3.9 to 11.9 MPa. We obtained stress-strain curves which show increase in differential stress with increasing inverse natural strain (εinv). The frequency distribution of interboudine gaps between separated grains with respect to εinv for boudinaged tourmaline grains shows that end of microboudinage occurred immediately after the peak frequency of fracturing. This occurrence commonly appeared in all the 10 samples. These results provided us with keys to discuss a stress-strain history during the microboudinage in relation to evolution of the granite complex. The spectacular implication would be a drop or relaxation in increased differential stress at the end of the microboudinage.