TY - JOUR
T1 - Determination of amphibole fracture strength for quantitative palaeostress analysis using microboudinage structures
AU - Kimura, Nozomi
AU - Nakayama, Shotaro
AU - Tsukimura, Katsuhiro
AU - Miwa, Shinko
AU - Okamoto, Atsushi
AU - Masuda, Toshiaki
N1 - Funding Information:
The authors thank Kumiko Onodera for collection of the metachert sample analysed in this study, Mutsuki Aoya for a helpful review of an early version of the manuscript, and Nobuaki Niitsuma, Toshiyuki Hashida, and Hideo Awaji for their encouraging suggestions. We also thank Hideki Mori for assistance in the preparation of thin sections, Tom Blenkinsop, Oliver Lacombe, and Shaocheng Ji for constructive comments on an early version of the manuscript, and two anonymous referees for encouraging comments on the manuscript. This study was financially supported by the Japanese Society of the Promotion of Science (JSPS).
PY - 2010/2
Y1 - 2010/2
N2 - The fracture strength of amphibole is estimated with the aim of extending the applicability of the microboudin method to palaeostress analysis. Before estimating the fracture strength of amphibole, it is necessary to evaluate the influence of the size effect on fracturing. Among the three models of size effect (effective-length, effective-area, and effective-volume), the effective-length model is found to be the most suitable in our microboudinage analysis of a metachert from Turkey that contains numerous microboudinaged amphibole grains of variable width embedded within a quartz matrix. Taking into account the influence of the size effect on fracturing, we undertook a comparative microboudinage analysis of the metachert sample, which also contains coexisting microboudinage structures of tourmaline and epidote. The analysis revealed an instantaneous-fracture strength for amphibole of 80 MPa for a 1 mm cube. The far-field differential stress (σ0), calculated based on amphibole microboudinage structures and considering the effect of the fatigue limit, is σ0 = 8 λ (frac(1, over(w, -)))1 / 2, where λ is the dimensionless stress parameter determined by microboudinage analysis and over(w, -) is the mean width of amphibole grains.
AB - The fracture strength of amphibole is estimated with the aim of extending the applicability of the microboudin method to palaeostress analysis. Before estimating the fracture strength of amphibole, it is necessary to evaluate the influence of the size effect on fracturing. Among the three models of size effect (effective-length, effective-area, and effective-volume), the effective-length model is found to be the most suitable in our microboudinage analysis of a metachert from Turkey that contains numerous microboudinaged amphibole grains of variable width embedded within a quartz matrix. Taking into account the influence of the size effect on fracturing, we undertook a comparative microboudinage analysis of the metachert sample, which also contains coexisting microboudinage structures of tourmaline and epidote. The analysis revealed an instantaneous-fracture strength for amphibole of 80 MPa for a 1 mm cube. The far-field differential stress (σ0), calculated based on amphibole microboudinage structures and considering the effect of the fatigue limit, is σ0 = 8 λ (frac(1, over(w, -)))1 / 2, where λ is the dimensionless stress parameter determined by microboudinage analysis and over(w, -) is the mean width of amphibole grains.
KW - Absolute magnitude of palaeodifferential stress
KW - Amphibole
KW - Fracture strength
KW - Microboudin
KW - Size effect
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U2 - 10.1016/j.jsg.2009.10.008
DO - 10.1016/j.jsg.2009.10.008
M3 - Article
AN - SCOPUS:75149195757
SN - 0191-8141
VL - 32
SP - 136
EP - 150
JO - Journal of Structural Geology
JF - Journal of Structural Geology
IS - 2
ER -