HR: 0800h
AN: T21B-0594    [Abstracts]
TI: The Microboudin Method: a New Paleostress Analysis
AU: * Kimura, N
EM: kimura-nonn@aist.go.jp
AF: National Institute of Advanced Industrial Science and Technology, Center 7, Higashi 1-1-1, Tsukuba, 305-8567, Japan
AU: Okamoto, A
EM: okamoto@geo.kankyo.tohoku.ac.jp
AF: Tohoku University, Aoba 6-6-20 Aoba-ku Aramaki, Sendai, 980-8579, Japan
AU: Masuda, T
EM: setmasu@ipc.shizuoka.ac.jp
AF: Shizuoka University, Oya 836, Suruga, Shizuoka, 422-8529, Japan
AB: The microboudin method has been recently established as a new paleopiezometer. The method is successfully applied to monomineralic metamorphic tectonites such as metacherts and marbles, which include the microboudinage structures of columnar minerals (tourmaline, epidote etc.). The absolute magnitude of the far- field paleodifferential stress σ₀ is estimated from the two parameters: the dimensionless stress parameter λ, and the extensional fracture strength S₀^* of micrometer-scale columnar mineral grains. λ is derived from the mechanical model for microboudinage based on the shear-lag model and the Weibull theory. The value of S₀^* for tourmaline and epidote were obtained from directly measured flexural strength by considering the size and shape of these minerals and influence of time on fracturing. The values of σ₀ estimated by this method for samples from Aksu (China), Eskisehir (Turkey), Wadi Tayin (Sultanate of Oman), Asemi (Japan) Greenbushes (Australia), and Sausar (India) are in the range of 1-15 MPa. These σ₀-values correspond to the differential stress at mid-crustal levels (> 10 km).
DE: 8020 Mechanics, theory, and modeling
DE: 8030 Microstructures
DE: 8164 Stresses: crust and lithosphere
DE: 8194 Instruments and techniques
SC: Tectonophysics [T]
MN: 2007 Fall Meeting